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OXYGEN ENHANCED COMBUSTION FOR NOx CONTROL
David R. Thompson; Lawrence E. Bool; Jack C. Chen
Conventional wisdom says adding oxygen to a combustion system enhances product throughput, system efficiency, and, unless special care is taken, increases NOx emissions. This increase in NOx emissions is typically due to elevated flame temperatures associated with oxygen use leading to added thermal NOx formation. Innovative low flame temperature oxy-fuel burner designs have been developed and commercialized to minimize both thermal and fuel NOx formation for gas and oil fired industrial furnaces. To be effective these systems require close to 100% oxy-fuel combustion and the cost of oxygen is paid for by fuel savings and other benefits. For applications to coal-fired utility boilers at the current cost of oxygen, however, it is not economically feasible to use 100% oxygen for NOx control. In spite of this conventional wisdom, Praxair and its team members, in partnership with the US Department of Energy National Energy Technology Laboratory, have developed a novel way to use oxygen to reduce NOx emissions without resorting to complete oxy-fuel conversion. In this concept oxygen is added to the combustion process to enhance operation of a low NOx combustion system. Only a small fraction of combustion air is replaced with oxygen in the process. By selectively adding oxygen to a low NOx combustion system it is possible to reduce NOx emissions from nitrogen-containing fuels, including pulverized coal, while improving combustion characteristics such as unburned carbon. A combination of experimental work and modeling was used to define how well oxygen enhanced combustion could reduce NOx emissions. The results of this work suggest that small amounts of oxygen replacement can reduce the NOx emissions as compared to the air-alone system. NOx emissions significantly below 0.15 lbs/MMBtu were measured. Oxygen addition was also shown to reduce carbon in ash. Comparison of the costs of using oxygen for NOx control against competing technologies, such as SCR, show that this concept offers substantial savings over SCR and is an economically attractive alternative to purchasing NOx credits or installing other conventional technologies. In conjunction with the development of oxygen based low NOx technology, Praxair also worked on developing the economically enhancing oxygen transport membrane (OTM) technology which is ideally suited for integration with combustion systems to achieve further significant cost reductions and efficiency improvements. This OTM oxygen production technology is based on ceramic mixed conductor membranes that operate at high temperatures and can be operated in a pressure driven mode to separate oxygen with infinite selectivity and high flux. An OTM material was selected and characterized. OTM elements were successfully fabricated. A single tube OTM reactor was designed and assembled. Testing of dense OTM elements was conducted with promising oxygen flux results of 100% of target flux. However, based on current natural gas prices and stand-alone air separation processes, ceramic membranes do not offer an economic advantage for this application. Under a different DOE-NETL Cooperative Agreement, Praxair is continuing to develop oxygen transport membranes for the Advanced Boiler where the economics appear more attractive.
Enhancing SNCR-aided combustion with oxygen addition
Kobayashi, Hisashi; Wu, Kuang Tsai; Bool, III, Lawrence E.
NOx emissions from combustion are reduced, NOx reduction efficiency by SNCR is improved, and other efficiencies are realized, by injecting oxygen into a fuel-rich combustion zone under controlled conditions.
A demonstration of the American Combustion PyretronTM oxygen-enhanced burner ws conducted under the Superfund Innovative Technology Evaluation (SITE) program. The Demonstration was conducted at the U.S. EPA's Combustion Research Facility (CRF) in Jefferson, Arkansas....
A demonstration of the American Combustion Pyretron TM oxygen-enhanced burner was conducted under the Superfund Innovative Technology Evaluation (SITE) program. he Demonstration was conducted at the U.S. EPA's Combustion Research Facility (CRF) in Jefferson, Arkansas. n eight wee...
The SITE Demonstration of the American Combustion Pyretron Oxygen-enhanced Burner
Laurel J. Staley; Robert E. Mournighan
A demonstration of the American Combustion Pyretron Ö oxygen-enhanced burner was conducted under the Superfund Innovative Technology Evaluation (SITE) program. The Demonstration was conducted at the U.S. EPAĺs Combustion Research Facility (CRF) in Jefferson, Arkansas. An eight week test series was conducted which involved burning a mixture of listed waste KO87 with contaminated soil from the Stringfellow Acid Pits under
High-Efficiency, High-Capacity, Low-NOx Aluminum Melting Using Oxygen-Enhanced Combustion
D'Agostini, M.D.
This report describes the development and application of a novel oxygen enhanced combustion system with an integrated vacuum swing adsorption (VSA) oxygen supply providing efficient, low NOx melting in secondary aluminum furnaces. The mainstay of the combustion system is a novel air-oxy-natural gas burner that achieves high productivity and energy efficiency with low NOx emissions through advanced mixing concepts and the use of separate high- and low-purity oxidizer streams. The technology was installed on a reverberatory, secondary aluminum melting plant at the Wabash Aluminum Alloy's Syracuse, N.Y. plant, where it is currently in operation. Field testing gave evidence that the new burner technology meets the stringent NOx emissions target of 0.323 lb NO2/ton aluminum, thus complying with regulations promulgated by Southern California's South Coast Air Quality Management District (SCAQMD). Test results also indicated that the burner technology exceeded fuel efficiency and melting capacity goals. Economic modeling showed that the novel air-oxy-fuel (ADF) combustion technology provides a substantial increase in furnace profitability relative to air-fuel operation. Model results also suggest favorable economics for the air-oxy-fuel technology relative to a full oxy-fuel conversion of the furnace.
Numerical study of the enhancement of combustion performance in a scramjet combustor due to injection of electric-discharge-activated oxygen molecules
NASA Astrophysics Data System (ADS)
Starik, A. M.; Bezgin, L. V.; Kopchenov, V. I.; Loukhovitski, B. I.; Sharipov, A. S.; Titova, N. S.
A comprehensive analysis of the efficiency of an approach based on the injection of a thin oxygen stream, subjected to a tailored electric discharge, into a supersonic H2-air flow to enhance the combustion performance in the mixing layer and in the scramjet combustor is conducted. It is shown that for such an approach there exist optimal values of reduced electric field E/N and transversal dimension d of the injected oxygen stream, which provide the minimal length of induction zone in the mixing layer. The optimal values of E/N and d depend on air flow parameters and the specific energy put into the oxygen. The injection of a thin oxygen stream (d = 1 mm) subjected to an electric discharge with E/N = 50-100 Td, which produces mostly singlet oxygen O2(a 1?g) and O_{2}(b\\,^{1}\\Sigma_{g}^{+} ) molecules and atomic oxygen, allows one to arrange stable combustion in a scramjet duct at an extremely low air temperature Tair = 900 K and pressure Pair = 0.3 bar even at a small specific energy put into the oxygen Es = 0.2 J ncm-3, and to provide rather high combustion completeness ? = 0.73. The advance in the energy released during combustion is much higher (hundred times), in this case, than the energy supplied to the oxygen stream in the electric discharge. This approach also makes it possible to ensure the rather high combustion completeness in the scramjet combustor with reduced length. The main reason for the combustion enhancement of the H2-air mixture in the scramjet duct is the intensification of chain-branching reactions due to the injection of a small amount of cold non-equilibrium oxygen plasma comprising highly reactive species, O2(a 1?g) and O_{2}(b\\,^{1}\\Sigma_{g}^{+} ) molecules and O atoms, into the H2-air supersonic flow.
Oxygen enriched combustion system performance study
M. A. Delano; Y. Kwan
The current study was undertaken to evaluate the performance of a pressure swing adsorption (PSA) oxygen plant to provide oxygen for industrial combustion applications. PSA oxygen plants utilize a molecular sieve material to separate air into an oxygen rich product stream and a nitrogen rich exhaust stream. These plants typically produce 90-95% purity oxygen and are located in close proximity
Dilute Oxygen Combustion - Phase 3 Report
Riley, Michael F.
Dilute Oxygen Combustion (DOC) burners have been successfully installed and operated in the reheat furnace at Auburn Steel Co., Inc., Auburn, NY, under Phase 3 of the Dilute Oxygen Combustion project. Two new preheat zones were created employing a total of eight 6.5 MMBtu/hr capacity burners. The preheat zones provide a 30 percent increase in maximum furnace production rate, from 75 tph to 100 tph. The fuel rate is essentially unchanged, with the fuel savings expected from oxy-fuel combustion being offset by higher flue gas temperatures. When allowance is made for the high nitrogen level and high gas phase temperature in the furnace, measured NOx emissions are in line with laboratory data on DOC burners developed in Phase 1 of the project. Burner performance has been good, and there have been no operating or maintenance problems. The DOC system continues to be used as part of Auburn Steel's standard reheat furnace practice. High gas phase temperature is a result of the high firing density needed to achieve high production rates, and little opportunity exists for improvement in that area. However, fuel and NOx performance can be improved by further conversion on furnace zones to DOC burners, which will lower furnace nitrogen levels. Major obstacles are cost and concern about increased formation of oxide scale on the steel. Oxide scale formation may be enhanced by exposure of the steel to higher concentrations of oxidizing gas components (primarily products of combustion) in the higher temperature zones of the furnace. Phase 4 of the DOC project will examine the rate of oxide scale formation in these higher temperature zones and develop countermeasures that will allow DOC burners to be used successfully in these furnace zones.
Dilute Oxygen Combustion Phase 3 Final Report
Riley, M.F.; Ryan, H.M.
Dilute Oxygen Combustion (DOC) burners have been successfully installed and operated in the reheat furnace at Auburn Steel Co., Inc., Auburn, NY, under Phase 3 of the Dilute Oxygen Combustion project. Two new preheat zones were created employing a total of eight 6.5 MMBtu/hr capacity burners. The preheat zones provide a 30 percent increase in maximum furnace production rate, from 75 tph to 100 tph. The fuel rate is essentially unchanged, with the fuel savings expected from oxy-fuel combustion being offset by higher flue gas temperatures. When allowance is made for the high nitrogen level and high gas phase temperature in the furnace, measured NOx emissions are in line with laboratory data on DOC burners developed in Phase 1 of the project. Burner performance has been good and there have been no operating or maintenance problems. The DOC system continues to be used as part of Auburn Steel?s standard reheat furnace practice. High gas phase temperature is a result of the high firing density needed to achieve high production rates, and little opportunity exists for improvement in that area. However, fuel and NOx performance can be improved by further conversion of furnace zones to DOC burners, which will lower furnace nitrogen levels. Major obstacles are cost and concern about increased formation of oxide scale on the steel. Oxide scale formation may be enhanced by exposure of the steel to higher concentrations of oxidizing gas components (primarily products of combustion) in the higher temperature zones of the furnace. Phase 4 of the DOC project will examine the rate of oxide scale formation in these higher temperature zones and develop countermeasures that will allow DOC burners to be used successfully in these furnace zones.
Oxygen Compatibility Screening Tests in Oxygen-Rich Combustion Environment
NASA Technical Reports Server (NTRS)
Eckel, Anerew J.
The identification and characterization of oxygen-rich compatible materials enables full-flow, staged combustion designs. Although these oxygen-rich designs offer significant cost, performance, and reliability benefits over existing systems, they have never been used operationally by the United States. If these systems are to be realized, it is critical to understand the long-term oxidative stability in high-temperature, high-pressure, oxygen-rich combustion environments. A unique facility has been constructed at the NASA Lewis Research Center to conduct tests of small-scale rocket engine materials and subcomponents in an oxygen-rich combustion environment that closely approximates a full-scale rocket engine. Thus, a broad range of advanced materials and concepts can be screened in a timely manner and at a relatively low cost.
Hydrogen-oxygen powered internal combustion engine
NASA Technical Reports Server (NTRS)
Cameron, H.; Morgan, N.
Hydrogen at 300 psi and oxygen at 800 psi are injected sequentially into the combustion chamber to form hydrogen-rich mixture. This mode of injection eliminates difficulties of preignition, detonation, etc., encountered with carburated, spark-ignited, hydrogen-air mixtures. Ignition at startup is by means of a palladium catalyst.
[Fire by spontaneous combustion of oxygen cylinders].
Coumans, Tanja; Maissan, Iscander M; Wolff, AndrÚ P; Stolker, Robert Jan; Damen, Johan; Scheffer, Gert Jan
The use of medicinal oxygen can be dangerous. The spontaneous combustion of an oxygen cylinder was the cause of a fire in an operating theatre and an emergency medical service. The fire developed after turning on the gas main while the flow supply valve was already open. Not opening the pressure reduction valve while the oxygen flow supply valve is open can prevent this type of fire. Information from the contractor shows that the probability of such an incident is 1 in a million. PMID:21083949
Incineration is widely used to clean up Superfund sites. Modifications which improve the efficiency with which waste can be incinerated are therefore of interest to EPA. Oxygen/air burners are of interest because their installation on conventional incinerators can allow for signi...
The paper discusses Enhanced Combustion Woodstove (ECW) technology, developed by EPA in response to the field observation that woodstoves certified by EPA as being clean burning were not achieving the level of emission control "seen" in laboratory tests. ts development was also i...
Bimetallic Fe-Ni Oxygen Carriers for Chemical Looping Combustion
Bhavsar, Saurabh; Veser, Goetz
The relative abundance, low cost, and low toxicity of iron make Fe-based oxygen carriers of great interest for chemical looping combustion (CLC), an emerging technology for clean and efficient combustion of fossil and renewable fuels. However, Fe also shows much lower reactivity than other metals (such as Ni and Cu). Here, we demonstrate strong improvement of Fe-based carriers by alloying the metal phase with Ni. Through a combination of carrier synthesis and characterization with thermogravimetric and fixed-bed reactor studies, we demonstrate that the addition of Ni results in a significant enhancement in activity as well as an increase in selectivity for total oxidation. Furthermore, comparing alumina and ceria as support materials highlights the fact that reducible supports can result in a strong increase in oxygen carrier utilization.
Oxygen Deficient Metabolism in Organs: A Link to Combustion Scienceá
Miller, Jason Mathew
In an attempt to better understand and model transport of oxygen, O2, from capillaries to living cells in surrounding tissue, the group combustion (O2 deficient) concept from the field of combustion science in engineering is applied...
Quantitative Measurement of Oxygen in Microgravity Combustion
NASA Technical Reports Server (NTRS)
Silver, Joel A.
A low-gravity environment, in space or in ground-based facilities such as drop towers, provides a unique setting for studying combustion mechanisms. Understanding the physical phenomena controlling the ignition and spread of flames in microgravity has importance for space safety as well as for better characterization of dynamical and chemical combustion processes which are normally masked by buoyancy and other gravity-related effects. Due to restrictions associated with performing measurements in reduced gravity, diagnostic methods which have been applied to microgravity combustion studies have generally been limited to capture of flame emissions on film or video, laser Schlieren imaging and (intrusive) temperature measurements using thermocouples. Given the development of detailed theoretical models, more sophisticated diagnostic methods are needed to provide the kind of quantitative data necessary to characterize the properties of microgravity combustion processes as well as provide accurate feedback to improve the predictive capabilities of the models. When the demands of space flight are considered, the need for improved diagnostic systems which are rugged, compact, reliable, and operate at low power becomes apparent. The objective of this research is twofold. First, we want to develop a better understanding of the relative roles of diffusion and reaction of oxygen in microgravity combustion. As the primary oxidizer species, oxygen plays a major role in controlling the observed properties of flames, including flame front speed (in solid or liquid flames), extinguishment characteristics, flame size and flame temperature. The second objective is to develop better diagnostics based on diode laser absorption which can be of real value in both microgravity combustion research and as a sensor on-board Spacelab as either an air quality monitor or as part of a fire detection system. In our prior microgravity work, an eight line-of-sight fiber optic system measured water vapor mole fractions in the NASA Lewis 2.2-sec Drop Tower. In that system, the laser and all electronics resided at the top of the drop tower and was connected via a fiber optic cable to the rig, on which a 'pitch and catch' set of fiber collimating lenses were used to transmit the laser beam across a jet diffusion flame. This system required eight independent detection/demodulation units and had poor spatial resolution. This research builds on this earlier work, resulting in an improved capability for quantitative, nonintrusive measurement of major combustion species. A vertical cavity surface-emitting diode laser (VCSEL) and a continuous spatial scanning method permit the measurement of temporal and spatial profiles of the concentrations and temperatures of molecular oxygen. High detection sensitivity is achieved with wavelength modulation spectroscopy (WMS). One-g experiments are performed using a slot diffusion flame. Microgravity measurements on a solid fuel (cellulose sheet) system are planned for the NASA Lewis 2.2-second Drop Tower Facility.
Low NOx combustion using cogenerated oxygen and nitrogen streams
Kobayashi, Hisashi (Putnam Valley, NY); Bool, Lawrence E. (East Aurora, NY); Snyder, William J. (Ossining, NY)
Combustion of hydrocarbon fuel is achieved with less formation of NOx by feeding the fuel into a slightly oxygen-enriched atmosphere, and separating air into oxygen-rich and nitrogen-rich streams which are fed separately into the combustion device.
The combustion kinetics of coal chars in oxygen-enriched environments.
Shaddix, Christopher R.; Murphy, Jeffrey J.
Oxygen-enhanced and oxygen-fired pulverized coal combustion is actively being investigated to achieve emission reductions and reductions in flue gas cleanup costs, as well as for coal-bed methane and enhanced oil recovery applications. To fully understand the results of pilot scale tests and to accurately predict scale-up performance through CFD modeling, accurate rate expressions are needed to describe coal char combustion under these unconventional combustion conditions. In the work reported here, the combustion rates of two pulverized coal chars have been measured in both conventional and oxygen-enriched atmospheres. A combustion-driven entrained flow reactor equipped with an optical particle-sizing pyrometry diagnostic and a rapid-quench sampling probe has been used for this investigation. Highvale subbituminous coal and a high-volatile eastern United States bituminous coal have been investigated, over oxygen concentrations ranging from 6 to 36 mol% and gas temperatures of 1320-1800 K. The results from these experiments demonstrate that pulverized coal char particles burn under increasing kinetic control in elevated oxygen environments, despite their higher burning rates in these environments. Empirical fits to the data have been successfully performed over the entire range of oxygen concentrations using a single-film oxidation model. Both a simple nth-order Arrhenius expression and an nth-order Langmuir-Hinshelwood kinetic equation provide good fits to the data. Local fits of the nth-order Arrhenius expression to the oxygen-enriched and oxygen-depleted data produce lower residuals in comparison to fits of the entire dataset. These fits demonstrate that the apparent reaction order varies from 0.1 under near-diffusion-limit oxygen-depleted conditions to 0.5 under oxygen-enriched conditions. Burnout predictions show good agreement with measurements. Predicted char particle temperatures tend to be low for combustion in oxygen-depleted environments.
Dilute Oxygen Combustion Phase IV Final Report
Riley, M.F.
Novel furnace designs based on Dilute Oxygen Combustion (DOC) technology were developed under subcontract by Techint Technologies, Coraopolis, PA, to fully exploit the energy and environmental capabilities of DOC technology and to provide a competitive offering for new furnace construction opportunities. Capital cost, fuel, oxygen and utility costs, NOx emissions, oxide scaling performance, and maintenance requirements were compared for five DOC-based designs and three conventional air5-fired designs using a 10-year net present value calculation. A furnace direct completely with DOC burners offers low capital cost, low fuel rate, and minimal NOx emissions. However, these benefits do not offset the cost of oxygen and a full DOC-fired furnace is projected to cost $1.30 per ton more to operate than a conventional air-fired furnace. The incremental cost of the improved NOx performance is roughly $6/lb NOx, compared with an estimated $3/lb. NOx for equ8pping a conventional furnace with selective catalytic reduction (SCCR) technology. A furnace fired with DOC burners in the heating zone and ambient temperature (cold) air-fired burners in the soak zone offers low capital cost with less oxygen consumption. However, the improvement in fuel rate is not as great as the full DOC-fired design, and the DOC-cold soak design is also projected to cost $1.30 per ton more to operate than a conventional air-fired furnace. The NOx improvement with the DOC-cold soak design is also not as great as the full DOC fired design, and the incremental cost of the improved NOx performance is nearly $9/lb NOx. These results indicate that a DOC-based furnace design will not be generally competitive with conventional technology for new furnace construction under current market conditions. Fuel prices of $7/MMBtu or oxygen prices of $23/ton are needed to make the DOC furnace economics favorable. Niche applications may exist, particularly where access to capital is limited or floor space limitations are critical. DOC technology will continue to have a highly competitive role in retrofit applications requiring increases in furnace productivity.
New Findings on Combustion Behavior of Oxygenated Synthetic Diesel Fuels
New results were obtained on pollutants evolution during the combustion of four oxygenated fuels, whichwere compared with n-tetradecane and n-octane combustion. Three different techniques were adopted on a single cylinder direct injection diesel engine, equipped with optical accesses: two-colour pyrometry for the measurement of in-cylinder soot loading, high speed cinematography for the visualization and analysis of spray and combustion, fast
The Pyretron is a burner which is designed to allow for the injection of oxygen into the combustion air stream for the purpose of increasing the efficiency of a hazardous waste incinerator. The SITE demonstration of the Pyretron took place at the U.S. EPA's Combustion Re...
Combustion Enhancement by Active Control
E. Haile; O. Delabroy; D. Durox; F. Lacas; S. Candel
Active control has many potential applications in the domain of combustion. Active instability control has been successfully\\u000a demonstrated in a variety of laboratory combustors and its practical use is currently being explored. Active control methods\\u000a also appear to be suited to the optimization of combustion system operation. The external controller may be used for example\\u000a to extend the stability margin
Combustion Enhancement with a Silent Discharge Plasma
NASA Astrophysics Data System (ADS)
Rosocha, Louis
It is well known that the application of an external electric field to a flame can affect its propagation speed, stability, and combustion chemistry (Lawton & Weinberg 1969). External electrodes, arc discharges, and plasma jets have been employed to allow combustible gas mixtures to operate outside their flammability limits by gas heating, injection of free radicals, and field-promoted flame stabilization (Yagodnikov & Voronetskii 1994). Other investigators have carried out experiments with silent electrical discharges applied to propagating flames (Inomata et al 1983, Kim et al 2003). These have demonstrated that the flame propagation velocity is actually decreased (combustion retarded) when a silent discharge is applied directly to the flame region, but that the flame propagation velocity is increased (combustion promoted) when a silent discharge is applied to the unburned gas mixture upstream of a flame. Two other recent works have considered the possibility of combustion enhancement in aircraft gas turbine engine combustor mixers by using a plasma-generating fuel nozzle, that employs an electric-arc or microwave plasma generator, to produce dissociated fuel or ionized fuel (Johnson et al 2001); and pulsed corona-enhanced detonation of fuel-air mixtures in jet engines (Wang et al 2003). In contrast to these prior works, we have employed a silent discharge plasma (SDP) reactor to break up large fuel molecules into smaller molecules and create free radicals or other active species in a gas stream before the fuel is mixed with an oxidizer and combusted. In experiments reported here, a cylindrical SDP reactor was used to 'activate' propane before mixing it with air and igniting the combustible gas mixture. With the plasma, the physical appearance of the flame changes and substantial changes in mass spectrometer fragmentation peaks are observed (e.g., propane fragments decrease and water and carbon dioxide increase). This indicates that the combustion process is enhanced with the application of the plasma. Results of changes in the degree of combustion will be discussed in terms of variations in the plasma specific energy.
Praxair's dilute oxygen combustion technology for pyrometallurgical applications
NASA Astrophysics Data System (ADS)
Riley, M. F.; Kobayashi, H.; Deneys, A. C.
Dilute oxygen combustion (DOC) technology uses separate high-velocity fuel and oxygen jets to generate strong in-furnace gas recirculation, producing combustion between the fuel and a highly diluted oxygen and furnace-gas mixture. These very low NOx oxy-fuel burners have been developed and commercially demonstrated in steel reheating furnaces. The burner design meets industry needs for increased productivity and lower operating costs with minimal capital expense and low maintenance. The performance of DOC technology has been measured under laboratory and industrial conditions encompassing both natural gas and coke oven gas firing, and a wide range of furnace temperatures and nitrogen levels that simulate air infiltration. This paper describes the results of the tests using natural gas as the fuel and lists potential applications for DOC technology in the non-ferrous metals industry.
Characteristics of non-premixed oxygen-enhanced combustion: II. Flame structure effects on soot precursor kinetics resulting in soot-free flames
Skeen, S.A.; Axelbaum, R.L. [Department of Energy, Environmental, Chemical Engineering, Washington University in St. Louis, St. Louis, MO (United States); Yablonsky, G. [Department of Energy, Environmental, Chemical Engineering, Washington University in St. Louis, St. Louis, MO (United States); Parks College, Saint Louis University, St. Louis, MO (United States)
A detailed computational study was performed to understand the effects of the flame structure on the formation and destruction of soot precursors during ethylene combustion. Using the USC Mech Version II mechanism the contributions of different pathways to the formation of benzene and phenyl were determined in a wide domain of Z{sub st} values via a reverse-pathway analysis. It was shown that for conventional ethylene-air flames two sequential reversible reactions play primary roles in the propargyl (C{sub 3}H{sub 3}) chemistry, namely (1) C{sub 2}H{sub 2}+CH{sub 3}= pC{sub 3} H{sub 4}+H, (2) pC{sub 3} H{sub 4}= C{sub 3} H{sub 3}+ H with the corresponding overall endothermic reaction of propargyl formation (3) C{sub 2} H{sub 2}+CH{sub 3}= C{sub 3} H{sub 3}+2H. The contributions of these reactions to propyne (pC{sub 3}H{sub 4}) and propargyl formation and propargyl self-combination leading to benzene and phenyl were studied as a function of physical position, temperature, Z{sub st}, and H concentration. In particular, the role of H radicals on soot precursor destruction was studied in detail. At low Z{sub st}, Reactions 1 and 2 contribute significantly to propyne and propargyl formation on the fuel side of the radical pool at temperatures greater than approx. 1600 K. At higher local temperatures near the radical pool where the concentration of H is significant, the reverse reactions begin to dominate resulting in soot precursor destruction. As Z{sub st} is increased, these regions merge and only net propargyl consumption is observed. Based on the equilibrium constant of Reaction 3, a Z{sub st} value was estimated above which the rate of propargyl formation as a soot precursor is greatly reduced (Z{sub st} = 0.3). This condition compares well with the experimental results for permanently blue counterflow flames in the literature. (author)
Oxygen carriers for chemical looping combustion of solid fuels
Aurora Rubel; Kunlei Liu; Jim Neathery; Darrell Taulbee
A thermal analyzerľdifferential scanning calorimeterľmass spectrometer (TGľDSCľMS) was used to study oxygen carriers (OC) for their potential use for the application of chemical looping combustion (CLC) to solid fuels. Reaction rates, changes in reaction rates with repeated oxidationľreductions, exothermic heats during oxidation, and the effect of changing reduction gas compositions were studied. Oxidation rates were greater than reduction rates and
Oxygen enriched combustion system performance study. Phase 2: 100 percent oxygen enriched combustion in regenerative glass melters, Final report
Tuson, G.B.; Kobayashi, H.; Campbell, M.J.
The field test project described in this report was conducted to evaluate the energy and environmental performance of 100% oxygen enriched combustion (100% OEC) in regenerative glass melters. Additional objectives were to determine other impacts of 100% OEC on melter operation and glass quality, and to verify on a commercial scale that an on-site Pressure Swing Adsorption oxygen plant can reliably supply oxygen for glass melting with low electrical power consumption. The tests constituted Phase 2 of a cooperative project between the United States Department of Energy, and Praxair, Inc. Phase 1 of the project involved market and technical feasibility assessments of oxygen enriched combustion for a range of high temperature industrial heating applications. An assessment of oxygen supply options for these applications was also performed during Phase 1, which included performance evaluation of a pilot scale 1 ton per day PSA oxygen plant. Two regenerative container glass melters were converted to 100% OEC operation and served as host sites for Phase 2. A 75 ton per day end-fired melter at Carr-Lowrey Glass Company in Baltimore, Maryland, was temporarily converted to 100% OEC in mid- 1990. A 350 tpd cross-fired melter at Gallo Glass Company in Modesto, California was rebuilt for permanent commercial operation with 100% OEC in mid-1991. Initially, both of these melters were supplied with oxygen from liquid storage. Subsequently, in late 1992, a Pressure Swing Adsorption oxygen plant was installed at Gallo to supply oxygen for 100% OEC glass melting. The particular PSA plant design used at Gallo achieves maximum efficiency by cycling the adsorbent beds between pressurized and evacuated states, and is therefore referred to as a Vacuum/Pressure Swing Adsorption (VPSA) plant.
Powdered aluminum and oxygen rocket propellants: Subscale combustion experiments
NASA Technical Reports Server (NTRS)
Meyer, Mike L.
Aluminum combined with oxygen has been proposed as a potential lunar in situ propellant for ascent/descent and return missions for future lunar exploration. Engine concepts proposed to use this propellant have not previously been demonstrated, and the impact on performance from combustion and two-phase flow losses could only be estimated. Therefore, combustion tests were performed for aluminum and aluminum/magnesium alloy powders with oxygen in subscale heat-sink rocket engine hardware. The metal powder was pneumatically injected, with a small amount of nitrogen, through the center orifice of a single element O-F-O triplet injector. Gaseous oxygen impinged on the fuel stream. Hot-fire tests of aluminum/oxygen were performed over a mixture ratio range of 0.5 to 3.0, and at a chamber pressure of approximately 480 kPa (70 psia). The theoretical performance of the propellants was analyzed over a mixture ratio range of 0.5 to 5.0. In the theoretical predictions the ideal one-dimensional equilibrium rocket performance was reduced by loss mechanisms including finite rate kinetics, two-dimensional divergence losses, and boundary layer losses. Lower than predicted characteristic velocity and specific impulse performance efficiencies were achieved in the hot-fire tests, and this was attributed to poor mixing of the propellants and two-phase flow effects. Several tests with aluminum/9.8 percent magnesium alloy powder did not indicate any advantage over the pure aluminum fuel.
Combustion of coal chars in oxygen-enriched atmospheres
Bejarano, P.A.; Levendis, Y.A. [Northeastern University, Boston, MA (United States)
This work pertains to the high-temperature combustion of pulverized coal chars under oxygen-enriched atmospheres. Single char particles were burned in a drop-tube furnace, electrically-heated to 1300-1500 K, in 21%, 50% and 100% O{sub 2}, in a balance of N{sub 2}. Their luminous combustion histories were observed with two-color ratio pyrometry. A solution of the Planckian ratio-pyrometry equation for temperature was implemented, extending on Wien's approximation. The temperature and time histories for 45-53 {mu}m bituminous chars experienced wide particle-to-particle disparity, and varied depending on oxygen mole fraction and furnace temperature. Average char surface temperatures increased from 1600-1800 K in air, to 2100-2300 K in 50% O-2, to 2300-2400 K in 100% O{sub 2}, at gas temperatures of 1300-1500 K, respectively. Combustion durations decreased from 25-45 ms in air, to 8-17 ms in 50% O{sub 2}, to 6-13 in 100% O{sub 2}. Thus, average particle temperatures increased by up to 45%, whereas burnout times decreased by up to 87% as combustion was progressively enriched in O{sub 2} until 100% was attained. The apparent and intrinsic reactivity of the chars burning at 1500 K gas temperature were found to increase by factors of to 8 and 35, respectively, as the oxygen mole fraction increased by a factor of five, from 21% to 100%.
REDUCTION OF NOx EMISSION FROM COAL COMBUSTION THROUGH OXYGEN ENRICHMENT
Western Research Institute
BOC Process Gas Solutions and Western Research Institute (WRI) conducted a pilot-scale test program to evaluate the impact of oxygen enrichment on the emissions characteristics of pulverized coal. The combustion test facility (CTF) at WRI was used to assess the viability of the technique and determine the quantities of oxygen required for NOx reduction from coal fired boiler. In addition to the experimental work, a series of Computational Fluid Dynamics (CFD) simulations were made of the CTF under comparable conditions. A series of oxygen enrichment test was performed using the CTF. In these tests, oxygen was injected into one of the following streams: (1) the primary air (PA), (2) the secondary air (SA), and (3) the combined primary and secondary air. Emission data were collected from all tests, and compared with the corresponding data from the baseline cases. A key test parameter was the burner stoichiometry ratio. A series of CFD simulation models were devised to mimic the initial experiments in which secondary air was enriched with oxygen. The results from these models were compared against the experimental data. Experimental evidence indicated that oxygen enrichment does appear to be able to reduce NOx levels from coal combustion, especially when operated at low over fire air (OFA) levels. The reductions observed however are significantly smaller than that reported by others (7-8% vs. 25-50%), questioning the economic viability of the technique. This technique may find favor with fuels that are difficult to burn or stabilize at high OFA and produce excessive LOI. While CFD simulation appears to predict NO amounts in the correct order of magnitude and the correct trend with staging, it is sensitive to thermal conditions and an accurate thermal prediction is essential. Furthermore, without development, Fluent's fuel-NO model cannot account for a solution sensitive fuel-N distribution between volatiles and char and thus cannot predict the trends seen in the experiment.
Methanol Droplet Combustion in Oxygen-Inert Environments in Microgravity
NASA Technical Reports Server (NTRS)
Nayagam, Vedha; Dietrich, Daniel L.; Hicks, Michael C.; Williams, Forman A.
The Flame Extinguishment (FLEX) experiment that is currently underway in the Combustion Integrated Rack facility onboard the International Space Station is aimed at understanding the effects of inert diluents on the flammability of condensed phase fuels. To this end, droplets of various fuels, including alkanes and alcohols, are burned in a quiescent microgravity environment with varying amounts of oxygen and inert diluents to determine the limiting oxygen index (LOI) for these fuels. In this study we report experimental observations of methanol droplets burning in oxygen-nitrogen-carbon dioxide and oxygen-nitrogen-helium gas mixtures at 0.7 and 1 atmospheric pressures. The initial droplet size varied between approximately 1.5 mm and 4 mm to capture both diffusive extinction brought about by insufficient residence time at the flame and radiative extinction caused by excessive heat loss from the flame zone. The ambient oxygen concentration varied from a high value of 30% by volume to as low as 12%, approaching the limiting oxygen index for the fuel. The inert dilution by carbon dioxide and helium varied over a range of 0% to 70% by volume. In these experiments, both freely floated and tethered droplets were ignited using symmetrically opposed hot-wire igniters and the burning histories were recorded onboard using digital cameras, downlinked later to the ground for analysis. The digital images yielded droplet and flame diameters as functions of time and subsequently droplet burning rate, flame standoff ratio, and initial and extinction droplet diameters. Simplified theoretical models correlate the measured burning rate constant and the flame standoff ratio reasonably well. An activation energy asymptotic theory accounting for time-dependent water dissolution or evaporation from the droplet is shown to predict the measured diffusive extinction conditions well. The experiments also show that the limiting oxygen index for methanol in these diluent gases is around 12% to 13% oxygen by volume.
RECENT ADVANCES IN CaSO4 OXYGEN CARRIER FOR CHEMICAL-LOOPING COMBUSTION (CLC) PROCESS
Qingjie Guo; Jianshe Zhang; Hongjing Tian
Chemical-looping combustion (CLC) is a novel combustion technology with inherent separation of the greenhouse gas CO2 and low NOx (NO, NO2, N2O) emissions. In CLC, the solid oxygen carrier supplies the stoichiometric oxygen needed for CO2 and water formation, resulting in a free nitrogen mixture. The performance of oxygen carrier is the key to CLC's application. A good oxygen carrier
Enhanced Combustion Low NOx Pulverized Coal Burner
David Towle; Richard Donais; Todd Hellewell; Robert Lewis; Robert Schrecengost
For more than two decades, Alstom Power Inc. (Alstom) has developed a range of low cost, infurnace technologies for NOx emissions control for the domestic U.S. pulverized coal fired boiler market. This includes Alstom's internally developed TFS 2000{trademark} firing system, and various enhancements to it developed in concert with the U.S. Department of Energy. As of the date of this report, more than 270 units representing approximately 80,000 MWe of domestic coal fired capacity have been retrofit with Alstom low NOx technology. Best of class emissions range from 0.18 lb/MMBtu for bituminous coal to 0.10 lb/MMBtu for subbituminous coal, with typical levels at 0.24 lb/MMBtu and 0.13 lb/MMBtu, respectively. Despite these gains, NOx emissions limits in the U.S. continue to ratchet down for new and existing boiler equipment. On March 10, 2005, the Environmental Protection Agency (EPA) announced the Clean Air Interstate Rule (CAIR). CAIR requires 25 Eastern states to reduce NOx emissions from the power generation sector by 1.7 million tons in 2009 and 2.0 million tons by 2015. Low cost solutions to meet such regulations, and in particular those that can avoid the need for a costly selective catalytic reduction system (SCR), provide a strong incentive to continue to improve low NOx firing system technology to meet current and anticipated NOx control regulations. The overall objective of the work is to develop an enhanced combustion, low NOx pulverized coal burner, which, when integrated with Alstom's state-of-the-art, globally air staged low NOx firing systems will provide a means to achieve: Less than 0.15 lb/MMBtu NOx emissions when firing a high volatile Eastern or Western bituminous coal, Less than 0.10 lb/MMBtu NOx emissions when firing a subbituminous coal, NOx reduction costs at least 25% lower than the costs of an SCR, Validation of the NOx control technology developed through large (15 MWt) pilot scale demonstration, and Documentation required for economic evaluation and commercial application. During the project performance period, Alstom performed computational fluid dynamics (CFD) modeling and large pilot scale combustion testing in its Industrial Scale Burner Facility (ISBF) at its U.S. Power Plant Laboratories facility in Windsor, Connecticut in support of these objectives. The NOx reduction approach was to optimize near-field combustion to ensure that minimum NOx emissions are achieved with minimal impact on unburned carbon in ash, slagging and fouling, corrosion, and flame stability/turn-down. Several iterations of CFD and combustion testing on a Midwest coal led to an optimized design, which was extensively combustion tested on a range of coals. The data from these tests were then used to validate system costs and benefits versus SCR. Three coals were evaluated during the bench-scale and large pilot-scale testing tasks. The three coals ranged from a very reactive subbituminous coal to a moderately reactive Western bituminous coal to a much less reactive Midwest bituminous coal. Bench-scale testing was comprised of standard ASTM properties evaluation, plus more detailed characterization of fuel properties through drop tube furnace testing and thermogravimetric analysis. Bench-scale characterization of the three test coals showed that both NOx emissions and combustion performance are a strong function of coal properties. The more reactive coals evolved more of their fuel bound nitrogen in the substoichiometric main burner zone than less reactive coal, resulting in the potential for lower NOx emissions. From a combustion point of view, the more reactive coals also showed lower carbon in ash and CO values than the less reactive coal at any given main burner zone stoichiometry. According to bench-scale results, the subbituminous coal was found to be the most amenable to both low NOx, and acceptably low combustibles in the flue gas, in an air staged low NOx system. The Midwest bituminous coal, by contrast, was predicted to be the most challenging of the three coals, with the Western bituminous coal predicted to beh
Titania-supported iron oxide as oxygen carrier for chemical-looping combustion of methane
BeatrÝz M. Corbella; JosÚ MarÝa Palacios
Chemical-looping combustion is a two-stage process proposed as an alternative for the combustion of carbonaceous materials, such as natural gas or coal gas, for almost complete CO2 capture. In the reduction stage, the structural oxygen contained in the lattice of a reducible inorganic oxide, is used for combustion of the carbonaceous material. In the regeneration stage the oxygen carrier, found
The use of ilmenite as an oxygen carrier in chemical-looping combustion
Henrik Leion; Anders Lyngfelt; Marcus Johansson; Erik Jerndal; Tobias Mattisson
The feasibility of using ilmenite as oxygen carrier in chemical-looping combustion has been investigated. It was found that ilmenite is an attractive and inexpensive oxygen carrier for chemical-looping combustion. A laboratory fluidized-bed reactor system, simulating chemical-looping combustion by exposing the sample to alternating reducing and oxidizing conditions, was used to investigate the reactivity. During the reducing phase, 15g of ilmenite
Combustion of hydrogen-oxygen mixture in electrochemically generated nanobubbles
NASA Astrophysics Data System (ADS)
Svetovoy, Vitaly B.; Sanders, Remko G. P.; Lammerink, Theo S. J.; Elwenspoek, Miko C.
Ignition of exothermic chemical reactions in small volumes is considered as difficult or impossible due to the large surface-to-volume ratio. Here observation of the spontaneous reaction is reported between hydrogen and oxygen in bubbles whose diameter is smaller than a threshold value around 150 nm. The effect is attributed to high Laplace pressure and to fast dynamics in nanobubbles and is the first indication on combustion in the nanoscale. In this study the bubbles were produced by water electrolysis using successive generation of H2 and O2 above the same electrode with short voltage pulses in the microsecond range. The process was observed in a microsystem at current densities >1000 A/cm2 and relative supersaturations >1000.
Combustion of hydrogen-oxygen mixture in electrochemically generated nanobubbles.
Svetovoy, Vitaly B; Sanders, Remko G P; Lammerink, Theo S J; Elwenspoek, Miko C
Ignition of exothermic chemical reactions in small volumes is considered as difficult or impossible due to the large surface-to-volume ratio. Here observation of the spontaneous reaction is reported between hydrogen and oxygen in bubbles whose diameter is smaller than a threshold value around 150 nm. The effect is attributed to high Laplace pressure and to fast dynamics in nanobubbles and is the first indication on combustion in the nanoscale. In this study the bubbles were produced by water electrolysis using successive generation of H(2) and O(2) above the same electrode with short voltage pulses in the microsecond range. The process was observed in a microsystem at current densities >1000 A/cm(2) and relative supersaturations >1000. PMID:22060445
NASA Astrophysics Data System (ADS)
Murdin, P.
The process whereby a substance is combined with oxygen with the production of heat. Burning is a familiar example of this process. The energy required to propel chemical rockets is provided by the combustion of fuel with an oxidant at very high temperatures. A common oxidant is liquid oxygen (often denoted by LOX). Others include hydrogen peroxide and nitrogen tetroxide....
CO 2 capture from coal combustion using chemical-looping combustion - Reactivity investigation of Fe, Ni and Mn based oxygen carriers using syngas
Tobias Mattisson; Marcus Johansson; Anders Lyngfelt
Chemical-looping combustion (CLC) is a combustion technology where an oxygen carrier is used to transfer oxygen from the combustion air to the fuel, thus avoiding direct contact between air and fuel. The system is composed of two reactors, a fuel and an air reactor, where the flue gas from the fuel reactor contains CO 2 and H 2O and the
Impact of oxygen enriched combustion on heat release curves of a Single Cylinder Diesel engine
K. Rajkumar; P. Govindarajan
In the present experimental work a computerized Single cylinder Diesel engine with data acquisition system was used to study the effects of oxygen enriched air intake on heat release rate. Increasing the oxygen content with the air leads to faster burn rates and the ability to burn more fuel at the same stoichiometry. Added oxygen in the combustion air offers
Combustion Enhancement Using a Silent Discharge Plasma Reactor
NASA Astrophysics Data System (ADS)
Rosocha, Louis; Platts, David; Coates, Don; Stange, Sy
Electric fields affect flame propagation speed, stability, and combustion chemistry. External electrodes, arc discharges, and plasma jets have been used to combust gas mixtures outside their flammability limits. Experiments with silent electrical discharges (SEDs) and propagating flames have shown that flame propagation velocity is actually decreased (combustion retarded) when an SED is applied directly to the flame region, but velocity is increased (combustion promoted) when applied to the unburned gas mixture upstream of a flame. More recent work has proposed electric arc/microwave-driven plasma-generating fuel nozzles to produce dissociated fuel or ionized fuel for aircraft gas turbine engine combustor mixers. In contrast to prior works, we have used a silent discharge plasma (SDP) reactor to break up large fuel molecules into smaller molecules and create free radicals/active species in a gas stream before the fuel is mixed with an oxidizer and combusted. A cylindrical SDP reactor was used to 'activate' propane before mixing it with air and igniting the combustible gas mixture. With the plasma, the physical appearance of the flame changes and substantial changes in mass spectrometer fragmentation peaks for fuel and combustion products are observed (i.e., combustion is enhanced). Results of changes in the degree of combustion will be discussed in terms of variations in the plasma specific energy.
Oxygen and Opacity Stack Emission Monitoring Systems To Optimize Combustion Efficiency and Meet EPA Requirementsá
Molloy, R. C.
The combustion efficiency of industrial fuel burning equipment can be optimized through the use of oxygen and opacity stack emission monitoring systems. By providing the operator with the means to obtain accurate, continuous, dynamic feedback...
Evaluation of Advanced PSA and Oxygen Combustion System for Industrial Furnace Applications
Delano, M. A.; Lagree, D.; Kwan, Y.
M. A. Delano Union Carbide Corp. Tarrytown, NY ABSTRACT EVALUATION OF ADVANCED PSA AND OXYGEN COMBUSTION SYSTEM FOR INDUSTRIAL FURNACE APPLICATIONS D. Lagree Union Carbide Corp. Tonawanda, NY The performance of a pilot scale advanced PSA... oxygen generation system and a low NO x oxygen burner was evaluated for industrial furnace applications. The PSA system employs a two-bed vacuum cycle design with a capacity of 1.3 TPD at 90% O 2 purity. The oxygen generated from the PSA system...
Mathematical simulation of hydrogen-oxygen combustion in rocket engines using LOGOS code
NASA Astrophysics Data System (ADS)
Betelin, V. B.; Shagaliev, R. M.; Aksenov, S. V.; Belyakov, I. M.; Deryuguin, Yu. N.; Korchazhkin, D. A.; Kozelkov, A. S.; Nikitin, V. F.; Sarazov, A. V.; Zelenskiy, D. K.
Hydrogen-oxygen fuels are very attractive now for rocket engines designers, because this pair is ecology friendly. Computer aided design of new effective and clean hydrogen engines needs mathematical tools for supercomputer modeling of hydrogen-oxygen components mixing and combustion in rocket engines. The paper presents the results of developing, verification and validation of mathematical model making it possible to simulate unsteady processes of ignition and combustion in rocket engines.
Comparison of iron-, nickel-, copper- and manganese-based oxygen carriers for chemical-looping combustion
Paul Cho; Tobias Mattisson; Anders Lyngfelt
For combustion with CO2 capture, chemical-looping combustion (CLC) with inherent separation of CO2 is a promising technology. Two interconnected fluidized beds are used as reactors. In the fuel reactor, a gaseous fuel is oxidized by an oxygen carrier, e.g. metal oxide particles, producing carbon dioxide and water. The reduced oxygen carrier is then transported to the air reactor, where it
Algorithmic Enhancements for Unsteady Aerodynamics and Combustion Applications
NASA Technical Reports Server (NTRS)
Venkateswaran, Sankaran; Olsen, Michael (Technical Monitor)
Research in the FY01 focused on the analysis and development of enhanced algorithms for unsteady aerodynamics and chemically reacting flowfields. The research was performed in support of NASA Ames' efforts to improve the capabilities of the in-house computational fluid dynamics code, OVERFLOW. Specifically, the research was focused on the four areas: (1) investigation of stagnation region effects; (2) unsteady preconditioning dual-time procedures; (3) dissipation formulation for combustion; and (4) time-stepping methods for combustion.
Evaluation of steam-to-oxygen ratios for forward combustion in Asphalt Ridge tar sand
Johnson, L.A. Jr.; Romanowski, L.J. Jr.
Three one-dimensional and one three-dimensional physical simulations of forward combustion with steam-oxygen injection were conducted using Asphalt Ridge tar sand. One-dimensional simulations had steam-oxygen ratios of 3.1:1, 4.3:1, and 6.0:1 at oxygen fluxes of 10.8 to 8.0 scfh/ft/sup 2/. The three-dimensional simulation had a steam-to-oxygen ratio of 3.0:1. Results from the one-dimensional simulations show a reduction in the fuel deposition and oxygen demand as the steam-to-oxygen ratio increases. In conjunction with reduction in fuel deposition is the increase in combustion front velocity and oil yield with increasing steam-to-oxygen ratio. These trends are assumed to be the result of improved displacement efficiency of the steam zone that precedes the pyrolysis and combustion zones in the forward combustion process and suppression of coking by the steam. The effect of combustion front channeling was demonstrated by the three-dimensional simulation. Channeling caused a decrease in process sweep efficiency and oil yield with increased fuel consumption. Product oils from all simulations were significantly improved in quality compared with the original bitumen. The product oils had significantly lower molecular weights, viscosities, and percentage of components boiling above 1000/sup 0/F (538/sup 0/C). 12 refs., 10 figs., 6 tabs.
Laboratory investigation of the oxygen combustion process for heavy oil recovery
Moss, J.T.; Cady, G.V.
The laboratory investigations were conducted using core material and produced oil from a typical Alberta heavy oil rservoir. The experiments established combustion characteristics using air and the combustion Thermal Drive (CTD) process for thermal oil recovery. Both the combustion and CTD tests indicated the oil's favorable response to thermal recovery. The results of laboratory studies using oxygen and oxygen with water injection have indicated that the enriched air process, as Ramey suggested almost thirty years ago, is not only viable as an oil recovery method, but the process is also highly desirable. 17 refs.
Experimental Research of the Oxygen-Enriched Combustion of Sewage Sludge and Coal in CFB
NASA Astrophysics Data System (ADS)
Xin, S. W.; Lu, X. F.; Liu, H. Z.
Sewage sludge is the by-products of sewage treatment, and it is a fuel of high moisture, high ash and low caloric. Oxygen-enriched combustion technology is one of the new and clean coal combustion technologies that can control pollutant emission, which makes CO2 separation, SO2 treatment become easier, and NOx emission reduced. In this paper, we carried out the experimental research on the advantages of oxygen-enriched combustion and the characteristics of sewage sludge in a CFB incinerator that the diameter of the furnace is 100 mm, It is an important foundation for the industrialized application of the oxygen-enriched combustion of sewage sludge and coal in CFB. Experimental analyzed on the combustion characteristics of three conditions in the oxygen concentration of 21%ś35%, which were the weight ratio of coal and sludge were 1?1, 1?2 and also the coal was given. Furthermore, the change of gas composition along with the change of oxygen content and the temperature of dense phase region was analyzed. The results showed that the combustion characteristics differ from the different mixing rate between coal and sludge in different oxygen atmosphere, when the fluidized air velocity was 1.56 m/sś1.88 m/s, the combustion stability; When the amount of the fuel was constant, as the increase of the oxygen contents in the experimental atmosphere, the total air volume decreased, the furnace temperature increased gradually, the concentration of SO2 and NOx showed increasing trend, which is beneficial to the removal of SO2; The concentration of NOx was increased gradually as temperature of the fluidized bed increased.
Simulation of surface profile formation in oxygen laser cutting of mild steel due to combustion cycles
NASA Astrophysics Data System (ADS)
Ermolaev, G. V.; Kovalev, O. B.
A physicomathematical model of cyclic iron combustion in an oxygen flow during oxygen laser cutting of metal sheets is developed. The combustion front is set into motion by focused laser radiation and a heterogeneous oxidation reaction in oxygen. The burning rate is limited by oxygen supply from the gas phase towards the metal surface, and the interface motion depends on the local temperature. A 3D numerical simulation predicts wavy structures on the metal surface; their linear sizes depend on the scanning speed of the laser beam, the thickness of the produced liquid oxide film and the parameters of the oxygen jet flow. Simulation results help in understanding the mechanism of striation formation during oxygen gas-laser cutting of mild steel and are in qualitative agreement with experimental findings.
Pressurized chemical-looping combustion of coal with an iron ore-based oxygen carrier
Xiao, Rui; Song, Min; Zhang, Shuai; Shen, Laihong [School of Energy and Environment, Southeast University, Sipailou No. 2, Nanjing 210096 (China); Song, Qilei [School of Energy and Environment, Southeast University, Sipailou No. 2, Nanjing 210096 (China); Department of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA (United Kingdom); Lu, Zuoji [School of Energy and Environment, Southeast University, Sipailou No. 2, Nanjing 210096 (China); GCL Engineering Limited, Zhujiang No. 1, Nanjing 210008 (China)
Chemical-looping combustion (CLC) is a new combustion technology with inherent separation of CO{sub 2}. Most of the previous investigations on CLC of solid fuels were conducted under atmospheric pressure. A pressurized CLC combined cycle (PCLC-CC) system is proposed as a promising coal combustion technology with potential higher system efficiency, higher fuel conversion, and lower cost for CO{sub 2} sequestration. In this study pressurized CLC of coal with Companhia Valedo Rio Doce (CVRD) iron ore was investigated in a laboratory fixed bed reactor. CVRD iron ore particles were exposed alternately to reduction by 0.4 g of Chinese Xuzhou bituminous coal gasified with 87.2% steam/N{sub 2} mixture and oxidation with 5% O{sub 2} in N{sub 2} at 970 C. The operating pressure was varied between 0.1 MPa and 0.6 MPa. First, control experiments of steam coal gasification over quartz sand were performed. H{sub 2} and CO{sub 2} are the major components of the gasification products, and the operating pressure influences the gas composition. Higher concentrations of CO{sub 2} and lower fractions of CO, CH{sub 4}, and H{sub 2} during the reduction process with CVRD iron ore was achieved under higher pressures. The effects of pressure on the coal gasification rate in the presence of the oxygen carrier were different for pyrolysis and char gasification. The pressurized condition suppresses the initial coal pyrolysis process while it also enhances coal char gasification and reduction with iron ore in steam, and thus improves the overall reaction rate of CLC. The oxidation rates and variation of oxygen carrier conversion are higher at elevated pressures reflecting higher reduction level in the previous reduction period. Scanning electron microscope and energy-dispersive X-ray spectroscopy (SEM-EDX) analyses show that particles become porous after experiments but maintain structure and size after several cycles. Agglomeration was not observed in this study. An EDX analysis demonstrates that there is very little coal ash deposited on the oxygen carrier particles but no appreciable crystalline phases change as verified by X-ray diffraction (XRD) analysis. Overall, the limited pressurized CLC experiments carried out in the present work suggest that PCLC of coal is promising and further investigations are necessary. (author)
Nanocrystalline perovskites for catalytic combustion and oxygen separation
Sangar, Neeraj, 1974-
Nanocrystalline perovskites (Lal-xAMnl-yByO3) were successfully synthesized with higher surface area and smaller grain size by chemical co-precipitation compared to solid-state and complexation/combustion synthesis routes. ...
Enhancement of pulverized coal combustion by plasma technology
Gorokhovski, M.A.; Jankoski, Z.; Lockwood, F.C.; Karpenko, E.I.; Messerle, V.E.; Ustimenko, A.B. [University of Rouen, Rouen (France)
Plasma-assisted pulverized coal combustion is a promising technology for thermal power plants (TPP). This article reports one- and three- dimensional numerical simulations, as well as laboratory and industrial measurements of coal combustion using a plasma-fuel system (PFS). The chemical kinetic and fluid mechanics involved in this technology are analysed. The results show that a PFS, can be used to promote early ignition and enhanced stabilization of a pulverized coal flame. It is shown that this technology, in addition to enhancing the combustion efficiency of the flame, reduces harmful emissions from power coals of all ranks (brown, bituminous, anthracite and their mixtures). Data summarising the experience of 27 pulverized coal boilers in 16 thermal power plants in several countries (Russia, Kazakhstan, Korea, Ukraine, Slovakia, Mongolia and China), embracing steam productivities from 75 to 670 tons per hour (TPH), are presented. Finally, the practical computation of the characteristics of the PFS, as function of coal properties, is discussed.
Rocket combustion chamber life-enhancing design concepts
NASA Technical Reports Server (NTRS)
Quentmeyer, Richard J.
NASA continues to pursue technologies which can lead to an increase in life and reduce the costs of fabrication of the Space Shuttle Main Engine. The joint NASA/Air Force Advanced Launch System Program has set its prime objectives to be high reliability and low cost for their new advanced booster engine. In order to meet these objectives, NASA will utilize the results of several ongoing programs to provide the required technologies. An overview is presented of those programs which address life enhancing design concepts for the combustion chamber. Seven different design concepts, which reduce the thermal strain and/or increase the material strength of the combustion chamber liner wall are discussed. Subscale rocket test results are presented, where available, for life enhancing design concepts. Two techniques for reducing chamber fabrication costs are discussed, as well as issues relating to hydrocarbon fuels/combustion chamber liner materials compatibility.
New type of microengine using internal combustion of hydrogen and oxygen
NASA Astrophysics Data System (ADS)
Svetovoy, Vitaly B.; Sanders, Remco G. P.; Ma, Kechun; Elwenspoek, Miko C.
Microsystems become part of everyday life but their application is restricted by lack of strong and fast motors (actuators) converting energy into motion. For example, widespread internal combustion engines cannot be scaled down because combustion reactions are quenched in a small space. Here we present an actuator with the dimensions 100 Î 100 Î 5 ?m3 that is using internal combustion of hydrogen and oxygen as part of its working cycle. Water electrolysis driven by short voltage pulses creates an extra pressure of 0.5-4 bar for a time of 100-400 ?s in a chamber closed by a flexible membrane. When the pulses are switched off this pressure is released even faster allowing production of mechanical work in short cycles. We provide arguments that this unexpectedly fast pressure decrease is due to spontaneous combustion of the gases in the chamber. This actuator is the first step to truly microscopic combustion engines.
New type of microengine using internal combustion of hydrogen and oxygen.
Svetovoy, Vitaly B; Sanders, Remco G P; Ma, Kechun; Elwenspoek, Miko C
Microsystems become part of everyday life but their application is restricted by lack of strong and fast motors (actuators) converting energy into motion. For example, widespread internal combustion engines cannot be scaled down because combustion reactions are quenched in a small space. Here we present an actuator with the dimensions 100 Î 100 Î 5??m(3) that is using internal combustion of hydrogen and oxygen as part of its working cycle. Water electrolysis driven by short voltage pulses creates an extra pressure of 0.5-4?bar for a time of 100-400??s in a chamber closed by a flexible membrane. When the pulses are switched off this pressure is released even faster allowing production of mechanical work in short cycles. We provide arguments that this unexpectedly fast pressure decrease is due to spontaneous combustion of the gases in the chamber. This actuator is the first step to truly microscopic combustion engines. PMID:24599052
Combustion of methane-oxygen and methane-oxygen-CFC mixtures initiated by a high-current slipping surface discharge
I. A. Kossyi; V. P. Silakov; N. M. Tarasova
Results are presented from experimental studies of the destruction of chlorofluorocarbon (CF2Cl2) molecules in a methane-oxygen (air) gas mixture whose combustion is initiated by a high-current slipping surface discharge.\\u000a It is found that a three-component CH4+O2(air)+CF2Cl2 gas mixture (even with a considerable amount of the third component) demonstrates properties of explosive combustion involving\\u000a chain reactions that are typical of two-component
Detailed Chemical Kinetic Modeling of Diesel Combustion with Oxygenated Fuels
H J Curran; E M Fisher; P-A Glaude; N M Marinov; W J Pitz; C K Westbrook; P F Flynn; R P Durrett; A O zur Loye; O C Akinyemi; F L Dryer
Emission standards for diesel engines in vehicles have been steadily reduced in recent years, and a great deal of research and development effort has been focused on reducing particulate and nitrogen oxide emissions. One promising approach to reducing emissions involves the addition of oxygen to the fuel, generally by adding an oxygenated compound to the normal diesel fuel. Miyamoto et
Laboratory investigation of the oxygen combustion process for heavy oil recovery
Moss, J.T.; Cady, G.V.
The laboratory investigations were conducted using core material and produced oil from a typical Alberta heavy oil reservoir. The experiments established combustion characteristics using air and the Combination Thermal Drive (CTD) process for thermal oil recovery. Both the combustion and CTD tests indicated the oil's favorable response to thermal recovery. The results of laboratory studies using oxygen and oxygen with water injection have indicated that the enriched air process, as Ramey suggested almost thirty years ago, is not only viable as an oil recovery method, but the process is also highly desirable.
Laboratory investigation of the oxygen combustion process of heavy oil recovery
Moss, J.T.; Cady, G.V.
The laboratory investigations were conducted using core material and produced oil from a typical Alberta heavy oil reservoir. The experiments established combustion characteristics using air and the CTD process for thermal oil recovery. Both combustion and CTD tests indicated the oil's favorable response to thermal recovery. The results of laboratory studies using oxygen and oxygen with water injection have indicated that the enriched air process, as Ramey suggested almost thirty years ago, is not only viable as an oil recovery method, but the process is also highly desirable. 17 refs.
Combustion Effects in Laser-oxygen Cutting: Basic Assumptions, Numerical Simulation and High Speed Visualization
NASA Astrophysics Data System (ADS)
Zaitsev, Alexander V.; Ermolaev, Grigory V.
Laser-oxygen cutting is very complicated for theoretical description technological process. Iron-oxygen combustion playing a leading role making it highly effective, able to cut thicker plates and, at the same time, producing special types of striations and other defects on the cut surface. In this paper results of numerical simulation based on elementary assumptions on iron-oxygen combustion are verified with high speed visualization of laser-oxygen cutting process. On a base of assumption that iron oxide lost its protective properties after melting simulation of striation formation due cycles of laser induced non self-sustained combustion is proposed. Assumption that reaction limiting factor is oxygen transport from the jet to cutting front allows to calculate reaction intensity by solving Navier - Stokes and diffusion system in gas phase. Influence of oxygen purity and pressure is studied theoretically. The results of numerical simulation are examined with high speed visualization of laser-oxygen cutting of 4-20 mm mild steel plates at cutting conditions close to industrial.
Numerical simulation of operation processes in the combustion chamber and gas generator of oxygen-methane liquid rocket engine
NASA Astrophysics Data System (ADS)
Kalmykov, G. P.; Larionov, A. A.; Sidlerov, D. A.; Yanchilin, L. A.
The results of numerical simulations of processes in gas generators and combustion chambers operating on oxygen and methane are presented. Specific features of mixing, evaporation, and combustion of propellants have been investigated. The degree of combustion completeness in chambers with three types of injectors - coaxial-jet gas-liquid, liquid-liquid monopropellant, and bipropellant impinging-jets injectors - has been estimated.
Combustion and Performance Analyses of Coaxial Element Injectors with Liquid Oxygen/Liquid Methane Propellants
NASA Technical Reports Server (NTRS)
Hulka, J. R.; Jones, G. W.
Liquid rocket engines using oxygen and methane propellants are being considered by the National Aeronautics and Space Administration (NASA) for in-space vehicles. This propellant combination has not been previously used in a flight-qualified engine system, so limited test data and analysis results are available at this stage of early development. NASA has funded several hardware-oriented activities with oxygen and methane propellants over the past several years with the Propulsion and Cryogenic Advanced Development (PCAD) project, under the Exploration Technology Development Program. As part of this effort, the NASA Marshall Space Flight Center has conducted combustion, performance, and combustion stability analyses of several of the configurations. This paper summarizes the analyses of combustion and performance as a follow-up to a paper published in the 2008 JANNAF/LPS meeting. Combustion stability analyses are presented in a separate paper. The current paper includes test and analysis results of coaxial element injectors using liquid oxygen and liquid methane or gaseous methane propellants. Several thrust chamber configurations have been modeled, including thrust chambers with multi-element swirl coax element injectors tested at the NASA MSFC, and a uni-element chamber with shear and swirl coax injectors tested at The Pennsylvania State University. Configurations were modeled with two one-dimensional liquid rocket combustion analysis codes, the Rocket Combustor Interaction Design and Analysis (ROCCID), and the Coaxial Injector Combustion Model (CICM). Significant effort was applied to show how these codes can be used to model combustion and performance with oxygen/methane propellants a priori, and what anchoring or calibrating features need to be applied or developed in the future. This paper describes the test hardware configurations, presents the results of all the analyses, and compares the results from the two analytical methods
Chemical looping combustion of biomass-derived syngas using ceria-supported oxygen carriers.
Huang, H B; Aisyah, L; Ashman, P J; Leung, Y C; Kwong, C W
Cu, Ni and Fe oxides supported on ceria were investigated for their performance as oxygen carriers during the chemical looping combustion of biomass-derived syngas. A complex gas mixture containing CO, H2, CO2, CH4 and other hydrocarbons was used to simulate the complex fuel gas environment derived from biomass gasification. Results show that the transfer of the stored oxygen into oxidants for the supported Cu and Ni oxides at 800░C for the combustion of syngas was effective (>85%). The unsupported Cu oxide showed high oxygen carrying capacity but particle sintering was observed at 800░C. A reaction temperature of 950░C was required for the supported Fe oxides to transfer the stored oxygen into oxidants effectively. Also, for the complex fuel gas environment, the supported Ni oxide was somewhat effective in reforming CH4 and other light hydrocarbons into CO, which may have benefits for the reduction of tar produced during biomass pyrolysis. PMID:23711944
Experimental and numerical study of PC combustion with oxygen enrichment in a blowpipe model of blast furnace
Cang Daqiang; Yang Min; Ding Yulong; Yang Tianjun [Univ. of Science and Technology, Beijing (China)
The method of pulverized coal injection (PCI), oxygen enrichment position, and PC size with oxygen enrichment have been studied to improve of the combustion efficiency of PC by using a theoretical model and experiment. The results showed: (1) by using double coal lance instead of single coal lance in a blowpipe, the combustion efficiency of anthracite can be increased significantly; (2) under the experimental conditions, pure oxygen directly mixed with hot blast is suitable for combustion efficiency when oxygen content is lower then 24%, and when oxygen content is higher, oxygen enrichment location at a proper position of blowpipe away from PC lance should be used; and (3) fine anthracite particle with high oxygen content is an effective way to improve the combustion efficiency of anthracite.
Enhanced Combustion Low NOx Pulverized Coal Burner
David Towle; Richard Donais; Todd Hellewell; Robert Lewis; Robert Schrecengost
For more than two decades, Alstom Power Inc. (Alstom) has developed a range of low cost, infurnace technologies for NOx emissions control for the domestic U.S. pulverized coal fired boiler market. This includes Alstom's internally developed TFS 2000{trademark} firing system, and various enhancements to it developed in concert with the U.S. Department of Energy. As of the date of this
Sy Tran, Luc; Sirjean, Baptiste; Glaude, Pierre-Alexandre; Fournet, RenÚ; Battin-Leclerc, FrÚdÚrique
Due to growing environmental concerns and diminishing petroleum reserves, a wide range of oxygenated species has been proposed as possible substitutes to fossil fuels: alcohols, methyl esters, acyclic and cyclic ethers. After a short review the major detailed kinetic models already proposed in the literature for the combustion of these molecules, the specific classes of reactions considered for modeling the oxidation of acyclic and cyclic oxygenated molecules respectively, are detailed. PMID:23700355
This paper summarizes the various system performance tests and the long-term operating experience of the LINDE Oxygen Combustion System installed on the U.S. Environmental Protection Agency's Mobile Incineration System (MIS) when it was in operation at the Denney Farm site in sou...
This paper summarizes the various system performance tests and the long-term operating experience of the LINDE(r) Oxygen Combustion System (OCS) installed on the U.S. Environmental Protection Agency's (EPA) Mobile Incineration System (MIS) when it was in operation at the Denney F...
John M. Veranth; Gautham Krishnamoorthy
This report examines coal combustion using oxygen feed with carbon dioxide recycle to control the adiabatic flame temperature. Computer simulations using an existing state-of-the-art 3-dimensional computer code for turbulent reacting flows with reacting particles were employed to study the effects of increased carbon dioxide mole fraction on the char burnout, radiant heat transfer, metal partitioning, and NOx formation.
Combustion versus Fuel Cells: Consider the combination of hydrogen and oxygen
Combustion versus Fuel Cells: Consider the combination of hydrogen and oxygen H2 + 1 2 O2 - H2O substantially less work. 3.) If we do the process in a fuel cell, we use chemical availability from Gibbs cycle. The bottom line is that the recovery of the chemical energy as work is at best 117650 141780
Enhanced efficiency of internal combustion engines by employing spinning gas.
Geyko, V I; Fisch, N J
The efficiency of the internal combustion engine might be enhanced by employing spinning gas. A gas spinning at near sonic velocities has an effectively higher heat capacity, which allows practical fuel cycles, which are far from the Carnot efficiency, to approach more closely the Carnot efficiency. A remarkable gain in fuel efficiency is shown to be theoretically possible for the Otto and Diesel cycles. The use of a flywheel, in principle, could produce even greater increases in efficiency. PMID:25215720
Enhanced efficiency of internal combustion engines by employing spinning gas
NASA Astrophysics Data System (ADS)
Geyko, V. I.; Fisch, N. J.
The efficiency of the internal combustion engine might be enhanced by employing spinning gas. A gas spinning at near sonic velocities has an effectively higher heat capacity, which allows practical fuel cycles, which are far from the Carnot efficiency, to approach more closely the Carnot efficiency. A remarkable gain in fuel efficiency is shown to be theoretically possible for the Otto and Diesel cycles. The use of a flywheel, in principle, could produce even greater increases in efficiency.
PHYSICAL REVIEW E 90, 022139 (2014) Enhanced efficiency of internal combustion engines by employing spinning gas
PHYSICAL REVIEW E 90, 022139 (2014) Enhanced efficiency of internal combustion engines by employing; published 28 August 2014) The efficiency of the internal combustion engine might be enhanced by employing Optimizing the internal combustion engine to achieve the highest possible fuel efficiency can be approached
Promoted Combustion of Metals in a High-Pressure, Flowing Oxygen Environment
NASA Technical Reports Server (NTRS)
Maes, M. J.; Stoltzfus, J. M.
Traditional promoted combustion testing has used 0.125 inch diameter samples that are ignited in a pressurized, oxygen-enriched environment. Many years of testing this sample size have yielded useful data regarding threshold pressure, or the minimum oxygen pressure required to support self-sustained combustion. However, when a material is tested in a flowing system, the threshold pressure changes. White Sands Test Facility has developed a test system to burn samples in flowing gaseous oxygen. Current sample configurations are 0.5 inch diameter rods and 1.25 inch diameter pipes with pressures ranging up to 2000 psi and gas velocities reaching 200 ft/s. This paper describes the test apparatus, modifications made as the result of a fire, and a description of the tests currently being performed.
Comparison of Oxygen-Bomb Combustion with Standard Ignition Techniques for Determining Author(s): William A. Reiners and Norma M. Reiners
Minnesota, University of
Comparison of Oxygen-Bomb Combustion with Standard Ignition Techniques for Determining Total Ash. http://www.jstor.org #12;COMPARISON OF OXYGEN-BOMB COMBUSTION WITH STANDARD IGNITION TECHNIQUES samples by oxygen- bomb combustion and by a simple muffle-furnacetechnique. The influence of using
Performance and Stability Analyses of Rocket Combustion Devices Using Liquid Oxygen/Liquid Methane Propellants
NASA Technical Reports Server (NTRS)
Hulka, James R.; Jones, G. W.
Liquid rocket engines using oxygen and methane propellants are being considered by the National Aeronautics and Space Administration (NASA) for in-space vehicles. This propellant combination has not been previously used in flight-qualified engine systems, so limited test data and analysis results are available at this stage of early development. NASA has funded several hardware-oriented programs with oxygen and methane propellants over the past several years with the Propulsion and Cryogenic Advanced Development (PCAD) project, under the Exploration Technology Development Program. As part of this effort, NASA Marshall Space Flight Center has conducted combustion, performance, and combustion stability analyses of several of the configurations on these programs. This paper summarizes these analyses. Test and analysis results of impinging and coaxial element injectors using liquid oxygen and liquid methane propellants are included. Several cases with gaseous methane are included for reference. Several different thrust chamber configurations have been modeled, including thrust chambers with multi-element like-on-like and swirl coax element injectors tested at NASA MSFC, and a unielement chamber with shear and swirl coax injectors tested at The Pennsylvania State University. Configurations were modeled with two one-dimensional liquid rocket combustion analysis codes, the Rocket Combustor Interaction Design and Analysis (ROCCID), and the Coaxial Injector Combustion Model (CICM). Significant effort was applied to show how these codes can be used to model combustion and performance with oxygen/methane propellants a priori, and what anchoring or calibrating features need to be applied or developed in the future. This paper describes the test hardware configurations, presents the results of all the analyses, and compares the results from the two analytical methods.
A Preliminary Study on the Toxic Combustion Products Testing of Polymers Used in High-Pressure Oxygen Systems
NASA Technical Reports Server (NTRS)
Hshieh, Fu-Yu; Beeson, Harold D.
One likely cause of polymer ignition in a high-pressure oxygen system is adiabatic-compression heating of polymers caused by pneumatic impact. Oxidative _ pyrolysis or combustion of polymers in a high-pressure oxygen system could generate toxic gases. This paper reports the preliminary results of toxic combustion product testing of selected polymers in a pneumatic-impact test system. Five polymers commonly used in high-pressure oxygen systems, Nylon 6/6, polychlorotrifluoroethylene (CTFE), polytetrafluoroethylene (PTFE), fluoroelastomer (Viton(TradeMark) A), and nitrile rubber (Buna N), were tested in a pneumatic-impact test system at 2500- or 3500-psia oxygen pressure. The polymers were ignited and burned, then combustion products were collected in a stainless-steel sample bottle and analyzed by GC/MS/IRD, GC/FID, and GC/Methanizer/FID. The results of adiabatic-compression tests show that combustion of hydrocarbon polymers, nitrogen-containing polymers, and halogenated polymers in high-pressure oxygen systems are relatively complete. Toxicity of the combustion product gas is presumably much lower than the combustion product gas generated from ambient-pressure oxygen (or air) environments. The NASA-Lewis equilibrium code was used to determine the composition of combustion product gas generated from a simulated, adiabatic-compression test of nine polymers. The results are presented and discussed.
How does the addition of oxygen improve the applicability of incineration? his paper addresses that question by evaluating the performance of oxygen enhanced hazardous waste incineration in three different applications. he cases studied include a laboratory study of the use of ox...
Dynamic oxygen-enhanced MRI of cerebrospinal fluid.
Mehemed, Taha M; Fushimi, Yasutaka; Okada, Tomohisa; Yamamoto, Akira; Kanagaki, Mitsunori; Kido, Aki; Fujimoto, Koji; Sakashita, Naotaka; Togashi, Kaori
Oxygen causes an increase in the longitudinal relaxation rate of tissues through its T1-shortening effect owing to its paramagnetic properties. Due to such effects, MRI has been used to study oxygen-related signal intensity changes in various body parts including cerebrospinal fluid (CSF) space. Oxygen enhancement of CSF has been mainly studied using MRI sequences with relatively longer time resolution such as FLAIR, and T1 value calculation. In this study, fifteen healthy volunteers were scanned using fast advanced spin echo MRI sequence with and without inversion recovery pulse in order to dynamically track oxygen enhancement of CSF. We also focused on the differences of oxygen enhancement at sulcal and ventricular CSF. Our results revealed that CSF signal after administration of oxygen shows rapid signal increase in both sulcal CSF and ventricular CSF on both sequences, with statistically significant predominant increase in sulcal CSF compared with ventricular CSF. CSF is traditionally thought to mainly form from the choroid plexus in the ventricles and is absorbed at the arachnoid villi, however, it is also believed that cerebral arterioles contribute to the production and absorption of CSF, and controversy remains in terms of the precise mechanism. Our results demonstrated rapid oxygen enhancement in sulcal CSF, which may suggest inhaled oxygen may diffuse into sulcal CSF space rapidly probably due to the abundance of pial arterioles on the brain sulci. PMID:24956198
The effect of carbon dioxide-oxygen mixtures on oil recovery by in-situ combustioná
Broussard, Neal Joseph
will be those reservoirs which contain low- gravity, high-viscosity crude oils. The objective of this research is to ascertain the benefits to be derived from using carbon dioxide-oxygen mixtures as the injected gas for oil recovery by in-situ combustion... TGASI Porosity of sand pack, % bv Specific gravity of produced oil, grms/cc Water saturation, % pv Gas saturation, % pv percent by volume of oxygen in injected gas Percent by volume of carbon dioxide in injected gas Total gas injected, SCF Atomic...
Chemicl-looping combustion of coal with metal oxide oxygen carriers
Siriwardane, R.; Tian, H.; Richards, G.; Simonyi, T.; Poston, J.
The combustion and reoxidation properties of direct coal chemical-looping combustion (CLC) over CuO, Fe2O3, Co3O4, NiO, and Mn2O3 were investigated using thermogravimetric analysis (TGA) and bench-scale fixed-bed flow reactor studies. When coal is heated in either nitrogen or carbon dioxide (CO2), 50% of weight loss was observed because of partial pyrolysis, consistent with the proximate analysis. Among various metal oxides evaluated, CuO showed the best reaction properties: CuO can initiate the reduction reaction as low as 500 ░C and complete the full combustion at 700 ░C. In addition, the reduced copper can be fully reoxidized by air at 700 ░C. The combustion products formed during the CLC reaction of the coal/metal oxide mixture are CO2 and water, while no carbon monoxide was observed. Multicycle TGA tests and bench-scale fixed-bed flow reactor tests strongly supported the feasibility of CLC of coal by using CuO as an oxygen carrier. Scanning electron microscopy (SEM) images of solid reaction products indicated some changes in the surface morphology of a CuO-coal sample after reduction/oxidation reactions at 800 ░C. However, significant surface sintering was not observed. The interactions of fly ash with metal oxides were investigated by X-ray diffraction and thermodynamic analysis. Overall, the results indicated that it is feasible to develop CLC with coal by metal oxides as oxygen carriers.
Effect of temperature on reduction of CaSO{sub 4} oxygen carrier in chemical-looping combustion of simulated coal gas in a fluidized bed reactor
Song, Q.L.; Xiao, R.; Deng, Z.Y.; Shen, L.H.; Xiao, J.; Zhang, M.Y. [Southeast University, Nanjing (China)
Chemical-looping combustion (CLC) is a promising combustion technology for gaseous and solid fuel with efficient use of energy and inherent separation of CO{sub 2}. The concept of a coal-fueled CLC system using, calcium sulfate (CaSO{sub 4}) as oxygen carrier is proposed in this study. Reduction tests of CaSO{sub 4} oxygen carrier with simulated coal gas were performed in a laboratory-scale fluidized bed reactor in the temperature range of 890-950{degree}C. A high concentration of CO{sub 2} was obtained at the initial reduction period. CaSO{sub 4} oxygen carrier exhibited high reactivity initially and decreased gradually at the late period of reduction. The sulfur release during the reduction of CaSO{sub 4} as oxygen carrier was also observed and analyzed. H{sub 2} and CO{sub 2} conversions were greatly influenced by reduction temperature. The oxygen carrier conversion and mass-based reaction rates during the reduction at typical temperatures were compared. Higher temperatures would enhance reaction rates and result in high conversion of oxygen carrier. An XRD patterns study indicated that CaS was the dominant product of reduction and the variation of relative intensity with temperature is in agreement with the solid conversion. ESEM analysis indicated that the surface structure of oxygen carrier particles changed significantly from impervious to porous after reduction. EDS analysis also demonstrated the transfer of oxygen from the oxygen carrier to the fuel gas and a certain amount of sulfur loss and CaO formation on the surface at higher temperatures. The reduction kinetics of CaSO{sub 4} oxygen carrier was explored with the shrinking unreacted-core model. The apparent kinetic parameters were obtained, and the kinetic equation well predicted the experimental data. Finally, some basic considerations on the use of CaSO{sub 4} oxygen carrier in a CLC system for solid fuels were discussed.
Determination of mercury in ash and soil samples by oxygen flask combustion methodľCold vapor atomic fluorescence spectrometry (CVAFS)
Wenhua Geng; Tsunenori Nakajima; Hirokazu Takanashi; Akira Ohki
A simple method was developed for the determination of mercury (Hg) in coal fly ash (CFA), waste incineration ash (WIA), and soil by use of oxygen flask combustion (OFC) followed by cold vapor atomic fluorescence spectrometry (CVAFS). A KMnO4 solution was used as an absorbent in the OFC method, and the sample containing a combustion agent and an ash or
Enhancement of combustion efficiency with mixing ratio during fluidized bed combustion of anthracite and bituminous blended coal
Jeong-Gook Jang; Mi-Ran Kim; Ki-Ho Lee; Jea-Keun Lee
In order to investigate the effect of mixing ratio of bituminous coal to blended coal on the enhancement of combustion efficiency,\\u000a combustion experiments of blended coal with anthracite and bituminous are done in a laboratory scale fluidized bed combustor\\u000a (10.8 cm ID and 170 cm height). The gross heating values of anthracite and bituminous coal used in this study are
A Brief Study on Toxic Combustion Products of the Polymers Used in High-Pressure Oxygen Systems
NASA Technical Reports Server (NTRS)
Hshieh, Fu-Yu; Beeson, Harold D.
One likely cause of polymer ignition in a high-pressure oxygen system is the adiabatic-compression heating of polymers caused by pneumatic impact. Oxidative pyrolysis or combustion of polymers in a high-pressure oxygen system could generate toxic gases. This paper investigates the feasibility of using the NASA pneumatic-impact system to conduct adiabatic-compression combustion tests and determines the toxic combustion products produced from the burning of five selected polymers. Five polymers commonly used in high-pressure oxygen systems, Zytel(Registered TradeMark) 42 (Nylon 6/6), Buna N (nitrile rubber), Witon(Registered TradeMark) A (copolymer of vinylidene fluoride and hexafluoropropylene), Neoflon(Registered TradeMark) (polychlorotrifluoroethylene), and Teflon(Registered TradeMark) (polytetrafluoroethylene), were tested in the NASA pneumatic-impact test system at 17.2-MPa oxygen pressure. The polymers were ignited and burned; combustion products were collected in a stainless-steel sample bottle and analyzed using various methods. The results show that the NASA pneumatic-impact system is an appropriate test system to conduct adiabatic-compression combustion tests and to collect combustion products for further chemical analysis. The composition of the combustion product gas generated from burning the five selected polymers are presented and discussed.
Combustion Stability Analyses of Coaxial Element Injectors with Liquid Oxygen/Liquid Methane Propellants
NASA Technical Reports Server (NTRS)
Hulka, J. R.
Liquid rocket engines using oxygen and methane propellants are being considered by the National Aeronautics and Space Administration (NASA) for in-space vehicles. This propellant combination has not been previously used in a flight-qualified engine system, so limited test data and analysis results are available at this stage of early development. NASA has funded several hardware-oriented activities with oxygen and methane propellants over the past several years with the Propulsion and Cryogenic Advanced Development (PCAD) project, under the Exploration Technology Development Program. As part of this effort, the NASA Marshall Space Flight Center has conducted combustion stability analyses of several of the configurations. This paper presents test data and analyses of combustion stability from the recent PCAD-funded test programs at the NASA MSFC. These test programs used swirl coaxial element injectors with liquid oxygen and liquid methane propellants. Oxygen was injected conventionally in the center of the coaxial element, and swirl was provided by tangential entry slots. Injectors with 28-element and 40-element patterns were tested with several configurations of combustion chambers, including ablative and calorimeter spool sections, and several configurations of fuel injection design. Low frequency combustion instability (chug) occurred with both injectors, and high-frequency combustion instability occurred at the first tangential (1T) transverse mode with the 40-element injector. In most tests, a transition between high-amplitude chug with gaseous methane flow and low-amplitude chug with liquid methane flow was readily observed. Chug analyses of both conditions were conducted using techniques from Wenzel and Szuch and from the Rocket Combustor Interactive Design and Analysis (ROCCID) code. The 1T mode instability occurred in several tests and was apparent by high-frequency pressure measurements as well as dramatic increases in calorimeter-measured heat flux throughout the chamber. Analyses of the transverse mode were conducted with ROCCID and empirical methods such as Hewitt d/V. This paper describes the test hardware configurations, test data, analysis methods, and presents results of the various analyses.
Oxygen bomb combustion of biological samples for inductively coupled plasma optical emission spectrometry
NASA Astrophysics Data System (ADS)
Souza, Gilberto B.; Carrilho, Elma Neide V. M.; Oliveira, Camila V.; Nogueira, Ana Rita A.; Nˇbrega, Joaquim A.
A rapid sample preparation method is proposed for decomposition of milk powder, corn bran, bovine and fish tissues, containing certified contents of the analytes. The procedure involves sample combustion in a commercial stainless steel oxygen bomb operating at 25 bar. Most of the samples were decomposed within 5 min. Diluted nitric acid or water-soluble tertiary amines 10% v/v were used as absorption solutions. Calcium, Cu, K, Mg, Na, P, S and Zn were recovered with the bomb washings and determined by inductively coupled plasma optical emission spectrometry (ICP-OES). Ethanol mixed with paraffin was used as a combustion aid to allow complete combustion. A cooling step prior releasing of the bomb valve was employed to increase the efficiency of sample combustion. Iodine was also determined in milk samples spiked with potassium iodide to evaluate the volatilization and collection of iodine in amine CFA-C medium and the feasibility of its determination by ICP-OES with axial view configuration. Most of the element recoveries in the samples were between 91 and 105% and the certified and found contents exhibited a fair agreement at a 95% confidence level.
Functionalized graphene sheet colloids for enhanced fuel/propellant combustion.
Sabourin, Justin L; Dabbs, Daniel M; Yetter, Richard A; Dryer, Frederick L; Aksay, Ilhan A
We have compared the combustion of the monopropellant nitromethane with that of nitromethane containing colloidal particles of functionalized graphene sheets or metal hydroxides. The linear steady-state burning rates of the monopropellant and colloidal suspensions were determined at room temperature, under a range of pressures (3.35-14.4 MPa) using argon as a pressurizing fluid. The ignition temperatures were lowered and burning rates increased for the colloidal suspensions compared to those of the liquid monopropellant alone, with the graphene sheet suspension having significantly greater burning rates (i.e., greater than 175%). The relative change in burning rate from neat nitromethane increased with increasing concentrations of fuel additives and decreased with increasing pressure until at high pressures no enhancement was found. PMID:19925013
Chemical-looping combustion of coal with metal oxide oxygen carriers
Ranjani Siriwardane; Hanjing Tian; George Richards; Thomas Simonyi; James Poston [United States Department of Energy, Morgantown, WN (United States). National Energy Technology Laboratory
The combustion and reoxidation properties of direct coal chemical-looping combustion (CLC) over CuO, Fe{sub 2}O{sub 3}, CO{sub 3}O{sub 4}, NiO, and Mn{sub 2}O{sub 3} were investigated using thermogravimetric analysis (TGA) and bench-scale fixed-bed flow reactor studies. When coal is heated in either nitrogen or carbon dioxide (CO{sub 2}), 50% of weight loss was observed because of partial pyrolysis, consistent with the proximate analysis. Among various metal oxides evaluated, CuO showed the best reaction properties: CuO can initiate the reduction reaction as low as 500{sup o}C and complete the full combustion at 700{sup o}C. In addition, the reduced copper can be fully reoxidized by air at 700{sup o}C. The combustion products formed during the CLC reaction of the coal/metal oxide mixture are CO{sub 2} and water, while no carbon monoxide was observed. Multicycle TGA tests and bench-scale fixed-bed flow reactor tests strongly supported the feasibility of CLC of coal by using CuO as an oxygen carrier. Scanning electron microscopy (SEM) images of solid reaction products indicated some changes in the surface morphology of a CuO-coal sample after reduction/oxidation reactions at 800 {sup o}C. However, significant surface sintering was not observed. The interactions of fly ash with metal oxides were investigated by X-ray diffraction and thermodynamic analysis. Overall, the results indicated that it is feasible to develop CLC with coal by metal oxides as oxygen carriers. 22 refs., 12 figs., 2 tabs.
Trityl-based EPR probe with enhanced sensitivity to oxygen.
Bobko, Andrey A; Dhimitruka, Ilirian; Eubank, Timothy D; Marsh, Clay B; Zweier, Jay L; Khramtsov, Valery V
An asymmetric derivative of the triarylmethyl radical, TAM-H, containing one aldehyde and two carboxyl groups, was synthesized. The electron paramagnetic resonance (EPR) spectrum of TAM-H is characterized by a doublet of narrow lines with a linewidth of 105 mG under anoxic conditions and hyperfine interaction constant of 245 mG. The partial overlap of the components of the doublet results in enhanced sensitivity of the spectral amplitudes ratio to oxygen compared with oxygen-induced linewidth broadening of a single line. Application of the TAM-H probe allows for EPR measurements in an extended range of oxygen pressures from atmospheric to 1 mm Hg, whereas the EPR spectrum linewidth of the popular TAM-based oxygen sensor Oxo63 is practically insensitive to oxygen partial pressures below 20 mm Hg. Enhanced sensitivity of the TAM-H probe relative to Oxo63 was demonstrated in the detection of oxygen consumption by Met-1 cancer cells. The TAM-H probe allowed prolonged measurements of oxygen depletion during the hypoxia stage and down to true anoxia (
Variable oxygen/nitrogen enriched intake air system for internal combustion engine applications
Poola, Ramesh B. (Woodridge, IL); Sekar, Ramanujam R. (Naperville, IL); Cole, Roger L. (Elmhurst, IL)
An air supply control system for selectively supplying ambient air, oxygen enriched air and nitrogen enriched air to an intake of an internal combustion engine includes an air mixing chamber that is in fluid communication with the air intake. At least a portion of the ambient air flowing to the mixing chamber is selectively diverted through a secondary path that includes a selectively permeable air separating membrane device due a differential pressure established across the air separating membrane. The permeable membrane device separates a portion of the nitrogen in the ambient air so that oxygen enriched air (permeate) and nitrogen enriched air (retentate) are produced. The oxygen enriched air and the nitrogen enriched air can be selectively supplied to the mixing chamber or expelled to atmosphere. Alternatively, a portion of the nitrogen enriched air can be supplied through another control valve to a monatomic-nitrogen plasma generator device so that atomic nitrogen produced from the nitrogen enriched air can be then injected into the exhaust of the engine. The oxygen enriched air or the nitrogen enriched air becomes mixed with the ambient air in the mixing chamber and then the mixed air is supplied to the intake of the engine. As a result, the air being supplied to the intake of the engine can be regulated with respect to the concentration of oxygen and/or nitrogen.
Emissions of Parent, Nitro, and Oxygenated Polycyclic Aromatic Hydrocarbons from Residential Wood Combustion in Rural China
SHEN, Guofeng; TAO, Shu; WEI, Siye; ZHANG, Yanyan; WANG, Rong; WANG, Bin; LI, Wei; SHEN, Huizhong; HUANG, Ye; CHEN, Yuanchen; CHEN, Han; YANG, Yifeng; WANG, Wei; WANG, Xilong; LIU, Wenxin; SIMONICH, Staci L. M.
Residential wood combustion is one of the important sources of air pollution in developing countries. Among the pollutants emitted, parent polycyclic aromatic hydrocarbons (pPAHs) and their derivatives, including nitrated and oxygenated PAHs (nPAHs and oPAHs), are of concern because of their mutagenic and carcinogenic effects. In order to evaluate their impacts on regional air quality and human health, emission inventories, based on realistic emission factors (EFs), are needed. In this study, the EFs of 28 pPAHs (EFPAH28), 9 nPAHs (EFPAHn9) and 4 oPAHs (EFPAHo4) were measured for residential combustion of 27 wood fuels in rural China. The measured EFPAH28, EFPAHn9, and EFPAHo4 for brushwood were 86.7▒67.6, 3.22▒1.95Î10?2, and 5.56▒4.32 mg/kg, which were significantly higher than 12.7▒7.0, 8.27▒5.51Î10?3, and 1.19▒1.87 mg/kg for fuel wood combustion (p < 0.05). Sixteen U.S. EPA priority pPAHs contributed approximately 95% of the total of the 28 pPAHs measured. EFs of pPAHs, nPAHs, and oPAHs were positively correlated with one another. Measured EFs varied obviously depending on fuel properties and combustion conditions. The EFs of pPAHs, nPAHs, and oPAHs were significantly correlated with modified combustion efficiency and fuel moisture. Nitro-naphthalene and 9-fluorenone were the most abundant nPAHs and oPAHs identified. Both nPAHs and oPAHs showed relatively high tendencies to be present in the particulate phase than pPAHs due to their lower vapor pressures. The gas-particle partitioning of freshly emitted pPAHs, nPAHs and oPAHs was primarily controlled by organic carbon absorption. PMID:22765266
Combustion Synthesis of Yttrium BARIUM(2) COPPER(3) OXYGEN(6+X) Superconductor.
NASA Astrophysics Data System (ADS)
Lin, Sy-Chyi
YBa_2Cu_3 O_{rm 6 + x} was produced from copper, barium peroxide, and yttrium oxide by Self-propagating High-temperature Synthesis (SHS) and thermal explosion methods. The SHS process was conducted in two modes: a horizontal combustion and a vertical combustion. The influence of copper particle size on the stability of the reaction front was studied. In contrast to previous studies, a stable reaction front could be maintained even when relatively large copper particles (smaller than 325 mesh) were used. In the horizontal SHS process, large diameter pellets (larger than 22 mm in diameter) enabled stable combustion at room temperature. Elevated ambient temperatures (400 {~} 500^circ C) were needed to stabilize the combustion front movement in small diameter pellets. The product had an average concentration of 84 wt% YBa_2Cu _3O_{rm 6 + x}. In the vertical SHS process, with the aid of a booster, the combustion front moved more rapidly and smoothly than that in the horizontal SHS process and gave a product concentration of about 90 wt% YBa _2Cu_3O_ {rm 6 + x}. High quality product (above 95 wt% YBa_2Cu_3 O_{rm 6 + x}) may be obtained by sintering/calcining the SHS product in an oxygen atmosphere. Three different sintering/calcining processes were studied and the required temperature and the time for each process were determined. The temperature at the center of the pellet in a vertical SHS was measured by thermocouples. The pellet temperature rise is a two step process. The first temperature rise is caused by the oxidation of the copper and the second is caused by the reaction between yttrium oxide and barium cuprate. A reaction mechanism is proposed to explain this behavior. A thermal explosion process was conducted in a continuous rotary kiln. In this mode a pellet was introduced suddenly into a heated rotary kiln causing it to be combusted. After the combustion, the pellet was sintered at 900 to 980 ^circC and a product containing about 95 wt% YBa_2Cu_3 O_{rm 6 + x} was obtained. The impacts of the thermal explosion temperature and the sintering conditions on the product quality were studied. The best temperature was found to be 800 ^circC and 100 minutes was sufficient for the pellet to reach equilibrium.
Combustion Stability Characteristics of the Project Morpheus Liquid Oxygen/Liquid Methane Main Engine
NASA Technical Reports Server (NTRS)
Melcher, J. C.; Morehead, Robert L.
The Project Morpheus liquid oxygen (LOX) / liquid methane rocket engines demonstrated acousticcoupled combustion instabilities during sea-level ground-based testing at the NASA Johnson Space Center (JSC) and Stennis Space Center (SSC). High-amplitude, 1T, 1R, 1T1R (and higher order) modes appear to be triggered by injector conditions. The instability occurred during the Morpheus-specific engine ignition/start sequence, and did demonstrate the capability to propagate into mainstage. However, the instability was never observed to initiate during mainstage, even at low power levels. The Morpheus main engine is a JSC-designed 5,000 lbf-thrust, 4:1 throttling, pressure-fed cryogenic engine using an impinging element injector design. Two different engine designs, named HD4 and HD5, and two different builds of the HD4 engine all demonstrated similar instability characteristics. Through the analysis of more than 200 hot fire tests on the Morpheus vehicle and SSC test stand, a relationship between ignition stability and injector/chamber pressure was developed. The instability has the distinct characteristic of initiating at high relative injection pressure drop (dP) at low chamber pressure (Pc); i.e., instabilities initiated at high dP/Pc at low Pc during the start sequence. The high dP/Pc during start results during the injector /chamber chill-in, and is enhanced by hydraulic flip in the injector orifice elements. Because of the fixed mixture ratio of the existing engine design (the main valves share a common actuator), it is not currently possible to determine if LOX or methane injector dP/Pc were individual contributors (i.e., LOX and methane dP/Pc typically trend in the same direction within a given test). The instability demonstrated initiation characteristic of starting at or shortly after methane injector chillin. Colder methane (e.g., sub-cooled) at the injector inlet prior to engine start was much more likely to result in an instability. A secondary effect of LOX sub-cooling was also possibly observed; greater LOX sub- cooling improved stability. Some tests demonstrated a low-amplitude 1L-1T instability prior to LOX injector chill-in. The Morpheus main engine also demonstrated chug instabilities during some engine shutdown sequences on the flight vehicle and SSC test stand. The chug instability was also infrequently observed during the startup sequence. The chug instabilities predictably initiated at low dP/Pc at low Pc. The chug instabilities were always self-limiting; startup chug instabilities terminated during throttle-up and shutdown chug instabilities decayed by shutdown termination.
Enhanced Combustion Woodstove (ECW) technology. Report for January 1991-July 1993
McCrillis, R.C.; Abbott, J.H.; Ponder, W.H.; Butts, N.L.; Henry, D.S.
The paper discusses Enhanced Combustion Woodstove (ECW) technology, developed by EPA in response to the field observation that woodstoves certified by EPA as being clean burning were not achieving the level of emission control 'seen' in laboratory tests. ECW technology is based on the fact that woodstove emissions are caused by the incomplete combustion and pyrolysis of wood in the primary combustion zone. To achieve low emissions, the stove must incorporate a secondary combustion zone above the wood which will hold flame at all times. Current noncatalytic woodstoves can achieve satisfactory secondary combustion only under fairly ideal conditions. Stable secondary combustion may not be achieved at typical low-fire conditions, leading to high emissions. Initial work focused on using an electrical glowplug (ECW electric) to ignite and add energy to the secondary combustion zone. Later work has focused on using a gaseous fuel (ECW gaseous or ECWG) for this purpose.
The subject of this paper is the experience with a novel and field-proven method for the enhanced control of transient emissions from rotary kiln incinerators using oxygen enrichment. hen high-BTU content wastes are fed into rotary kiln incinerators in an intermittent mode (typic...
Comparison of CuO and NiO as oxygen carrier in chemical looping combustion of a Victorian brown coal
C. Saha; S. Bhattacharya
Chemical looping combustion (CLC) is a novel process where an oxygen carrier, preferably oxides of metal, is used to transfer oxygen from the combustion air to the fuel. The outlet gas from the process reactor consists of CO2 and H2O, and concentrated stream of CO2 is obtained for sequestration when water vapour is condensed. Chemical looping has been widely studied
Enhanced combustion by jet ignition in a turbocharged cryogenic port fuel injected hydrogen engine
Alberto A. Boretti; Harry C. Watson
The Hydrogen Assisted Jet Ignition (HAJI) is a physico-chemical combustion enhancement system developed at the University of Melbourne. Jet ignition can ignite ultra-lean air\\/fuel mixtures which are far beyond the stable ignition limit of a spark plug. Jet ignition may further enhance the combustion properties of hydrogen enabling the development of a diesel-like, almost throttle-less, control of load by quantity
Mapping of the range of operational conditions for Cu, Fe, and Ni-based oxygen carriers in chemical-looping combustion
Alberto Abad; Juan Adßnez; Francisco GarcÝa-Labiano; Luis F. de Diego; Pilar Gayßn; Javier Celaya
Chemical-looping combustion (CLC) is a two-step combustion process that produces a pure CO2 stream, ready for compression and sequestration. A CLC system is composed by two reactors, an air and a fuel reactor, and an oxygen carrier (OC) circulating between the reactors, which transfers the oxygen necessary for the fuel combustion from the air to the fuel. This system can
Fate of hazardous air pollutants in oxygen-fired coal combustion with different flue gas recycling.
Zhuang, Ye; Pavlish, John H
Experiments were performed to characterize transformation and speciation of hazardous air pollutants (HAPs), including SO(2)/SO(3), NO(x), HCl, particulate matter, mercury, and other trace elements in oxygen-firing bituminous coal with recirculation flue gas (RFG) from 1) an electrostatic precipitator outlet or 2) a wet scrubber outlet. The experimental results showed that oxycombustion with RFG generated a flue gas with less volume and containing HAPs at higher levels, while the actual emissions of HAPs per unit of energy produced were much less than that of air-blown combustion. NO(x) reduction was achieved in oxycombustion because of the elimination of nitrogen and the destruction of NO in the RFG. The elevated SO(2)/SO(3) in flue gas improved sulfur self-retention. SO(3) vapor could reach its dew point in the flue gas with high moisture, which limits the amount of SO(3) vapor in flue gas and possibly induces material corrosion. Most nonvolatile trace elements were less enriched in fly ash in oxycombustion than air-firing because of lower oxycombustion temperatures occurring in the present study. Meanwhile, Hg and Se were found to be enriched on submicrometer fly ash at higher levels in oxy-firing than in air-blown combustion. PMID:22439940
Heat Release Rate and Effective Heat of Combustion Measurements: A Comparative Study of Thermal and Oxygen Consumption Techniques
Fatima Moussan; Jean-Louis Delfau; Christian Vovelle; Christian Pham Van Cang; GÚrard Bosseboeuf
A new calorimeter especially built for the measurement of the heat release rate and effective heat of combustion of composite materials is pre sented. Two procedures can be used to obtain these data: the first one is based on the direct measurement of the convective and radiant heat liberated by the flame, the second involves oxygen consumption measurement. Preliminary ex
A hybrid power generation system utilizing solar thermal energy with CO 2 recovery based on oxygen combustion method
Pyong Sik Pak; Takeshi Hatikawa; Yutaka Suzuki
A CO2-recovering power generation system utilizing solar thermal energy was proposed. In the system, relatively low temperature saturated steam around 200 ░C is produced by using solar thermal energy and is utilized as the working fluid of a gas turbine in which generated CO2 is recovered based on the method of oxygen combustion. Solar thermal utilization efficiency becomes considerably high
Burning of solids in oxygen-rich environments in normal and reduced gravity. [combustion of cellulose acetates
NASA Technical Reports Server (NTRS)
Andracchio, C. R.; Cochran, T. H.
An experimental program was conducted to investigate the combustion characteristics of solids burning in a weightless environment. The combustion characteristics of thin cellulose acetate material were obtained from specimens burned in supercritical as well as in low pressure oxygen atmospheres. Flame spread rates were measured and found to depend on material thickness and pressure in both normal gravity (1-g) and reduced gravity (0-g). A gravity effect on the burning process was also observed; the ratio of 1-g to 0-g flame spread rate becomes larger with increasing material thickness. Qualitative results on the combustion characteristics of metal screens (stainless steel, Inconel, copper, and aluminum) burning in supercritical oxygen and normal gravity are also presented. Stainless steel (300 sq mesh) was successfully ignited in reduced gravity; no apparent difference in the flame spread pattern was observed between 1-g and 0-g.
Oxygen sensor feedback loop digital electronic signal integrator for internal combustion engine control
Hartford, T.W.; Kessler, J.A.
A method and apparatus for controlling the various functions of an internal combustion engine are disclosed that uses a program-controlled microprocessor having a memory preprogrammed with various control laws and associated control schedules receives information concerning one or more engine-operating parameters such as manifold pressure, throttle position, engine coolant temperature, air temperature, and engine speed or period and the like. These parameters are sensed or measured and then the value thereof is supplied to input circuits for signal conditioning and conversion to digital words usable by the microprocessor. The microprocessor system computes digital control words indicative of particular computer-commanded engine control operations and output circuitry responds to predetermined computer-generated commands and to the computed digital command words for converting them into corresponding pulse-width control signals for controlling such engine operations as fuel-injection, ignition timing, proportional and/or on-off egr control, and the like. The engine control system further includes an oxygen sensor feedback system for providing reliable data to said microprocessor for command control purposes. In particular the oxygen sensor signal is sampled a predetermined number of times per each engine revolution and the totality of each sampling is determined per revolution. This generates a digital word representing the condition of the air/fuel ratio of the engine over each revolution.
Clinical oxygen enhancement ratio of tumors in carbon ion radiotherapy: the influence of local oxygenation changes.
Antonovic, Laura; Lindblom, Emely; Dasu, Alexandru; Bassler, Niels; Furusawa, Yoshiya; Toma-Dasu, Iuliana
The effect of carbon ion radiotherapy on hypoxic tumors has recently been questioned because of low linear energy transfer (LET) values in the spread-out Bragg peak (SOBP). The aim of this study was to investigate the role of hypoxia and local oxygenation changes (LOCs) in fractionated carbon ion radiotherapy. Three-dimensional tumors with hypoxic subvolumes were simulated assuming interfraction LOCs. Different fractionations were applied using a clinically relevant treatment plan with a known LET distribution. The surviving fraction was calculated, taking oxygen tension, dose and LET into account, using the repairable-conditionally repairable (RCR) damage model with parameters for human salivary gland tumor cells. The clinical oxygen enhancement ratio (OER) was defined as the ratio of doses required for a tumor control probability of 50% for hypoxic and well-oxygenated tumors. The resulting OER was well above unity for all fractionations. For the hypoxic tumor, the tumor control probability was considerably higher if LOCs were assumed, rather than static oxygenation. The beneficial effect of LOCs increased with the number of fractions. However, for very low fraction doses, the improvement related to LOCs did not compensate for the increase in total dose required for tumor control. In conclusion, our results suggest that hypoxia can influence the outcome of carbon ion radiotherapy because of the non-negligible oxygen effect at the low LETs in the SOBP. However, if LOCs occur, a relatively high level of tumor control probability is achievable with a large range of fractionation schedules for tumors with hypoxic subvolumes, but both hyperfractionation and hypofractionation should be pursued with caution. PMID:24728013
V. A. Kuvshinov
The use of carbon dioxide and combustion gases in EOR technologies is of interest from the point of view of CO2 geological sequestration. During the period of 1980-1990 large-scale pilot tests were carried out in Russia to utilize carbon dioxide and combustion gases, formed at different petrochemical production plants, to enhance oil recovery in different hydrocarbon fields. The analysis of
Combustion of solid fuel slabs with gaseous oxygen in a hybrid motor analog
NASA Technical Reports Server (NTRS)
Chiaverini, Martin J.; Harting, George C.; Lu, Yeu-Cherng; Kuo, Kenneth K.; Serin, Nadir; Johnson, David K.
Using a high-pressure, two-dimensional hybrid motor, an experimental investigation was conducted on fundamental processes involved in hybrid rocket combustion. HTPB (Hydroxyl-terminated Polybutadiene) fuel cross-linked with diisocyanate was burned with gaseous oxygen (GOX) under various operating conditions. Large-amplitude pressure oscillations were encountered in earlier test runs. After identifying the source of instability and decoupling the GOX feed-line system and combustion chamber, the pressure oscillations were drastically reduced from plus or minus 20% of the localized mean pressure to an acceptable range of plus or minus 1.5%. Embedded fine--wire thermocouples indicated that the surface temperature of the burning fuel was around 1000 K depending upon axial locations and operating conditions. Also, except near the leading edge region, the subsurface thermal wave profiles in the upstream locations are thicker than those in the downstream locations since the solid-fuel regression rate, in general, increases with distance along the fuel slab. The recovered solid fuel slabs in the laminar portion of the boundary layer exhibited smooth surfaces, indicating the existence of a liquid melt layer on the burning fuel surface in the upstream region. After the transition section, which displayed distinct transverse striations, the surface roughness pattern became quite random and very pronounced in the downstream turbulent boundary-layer region. Both real-time X-ray radiography and ultrasonic pulse echo techniques were used to determine the instantaneous web thicknesses and instantaneous solid-fuel regression rates over certain portions of the fuel slabs. Globally averaged and axially dependent but time-averaged regression rates were also obtained and presented. Several tests were conducted using, simultaneously, one translucent fuel slab and one fuel slab processed with carbon black powder. The addition of carbon black did not affect the measured regression rates or surface temperatures in comparison to the translucent fuel slabs.
Supplemental Oxygen (Oxygen Therapy)
... gas and is non-flammable, however, it supports combustion. Materials burn more readily in an oxygen-enriched ... avoid using lotions or creams containing petroleum. The combustion of flammable products containing petroleum can also be ...
Development of a combination oxygen-supported water-assisted thermal drive process
Cady, G.V.; White, P.D.
The use of in-situ combustion oil recovery processes has developed over a forty-five year period from early ideas expressed in patents. Subsequent to early concepts, the combustion process was field tested by Russian scientists in 1934. The combustion process development intensified during the 1950's when oil companies designed and initiated three combustion tests. Further combustion process enhancement came when Tejas Engineers and a consortium of oil companies introduced the Combustion Thermal Drive (CTD) process in 1964. The CTD process involves air combustion with concurrent water injection to provide an efficient means of moving heat stored from behind to ahead of the combustion front. Ultra-pure oxygen combustion was suggested by Ramey in 1954. An extension to pure oxygen combustion is the combination oxygen-water process to improve heat efficiency during combustion. This paper discusses the development of a Combination Oxygen Supported Water Assisted Thermal Drive (COSWATD) process.
Alterations of bitumen produced by the in-situ combustion process at the oxygen Wolf Lake Project, Alberta
Riechert, C.; Fuhr, B. (Alberta Research Council, Edmonton (Canada)); Williams, G. (British Petroleum Canada Ltd., Calgary, Alberta (Canada)); Sawatzky, H.; Jha, K.; Lafleur, R. (Canmet, Energy Mines and Resources Canada, Ottawa, Ontario (Canada))
The Oxygen Wolf Lake Project, operated by BP Resources Canada Limited, recovers bitumen by an in-situ combustion process. Bitumen samples produced from this process were analyzed and compared with analyses of unaltered bitumen from the same formation. The naphtha and middle distillate fractions were greater in the samples produced by the in-situ combustion process, which indicates thermal cracking has occurred. Gas chromatograph and Mass Spectral analyses of these samples have been used to further describe the changes to the oil. The compositional changes found in the study have been related to reductions in viscosity and density. Implications of bitumen alterations to the performance of the combustion process and production problems are discussed.
Contrasting reactive oxygen species and transition metal concentrations in combustion aerosols.
See, S W; Wang, Y H; Balasubramanian, R
The presence of reactive oxygen species (ROS) and 10 transition metals (Ag, Cd, Co, Cu, Fe, Mn, Ni, Ti, V and Zn) in both the acid-soluble and water-soluble fractions of fine particles of combustion origin were determined. ROS was analyzed using the dichlorofluorescin fluorescence technique. Particles emitted from on-road vehicles, gas cooking, incense burning, and cigarette smoke were characterized along with those in the background air of outdoor and indoor environments. In addition, this study evaluated the possible relationships between ROS and individual transition metals. It is found that cigarette smoke which had the highest concentration of metals also contained the highest concentration of ROS. Regression analysis performed showed that water-soluble metals including Cd, Co, Cu, Fe, Mn, and Ni showed better correlation with ROS concentration as compared to acid-soluble (total) metals. The findings demonstrated that water-soluble metals could be one of the species influencing ROS formation in ambient air. PMID:17011545
John M. Veranth; Gautham Krishnamoorthy
Two computational problems were worked on for this study. The first chapter examines the option of coal combustion using oxygen feed with carbon dioxide recycle to control the adiabatic flame temperature. Computer simulations using an existing state-of-the-art 3-dimensional computer code for turbulent reacting flows with reacting particles were employed to study the effects of increased carbon dioxide mole fraction on the char burnout, radiant heat transfer, metal partitioning, and NOx formation. The second chapter compares assumptions for the CO/CO{sub 2} ratio at the surface of mineral inclusions made in previous studies to predictions obtained from a pseudo-steady state kinetic model (SKIPPY) for a single porous particle. The detailed kinetic simulations from SKIPPY for varying particle sizes and bulk gas compositions were used to develop algebraic expressions for the CO/CO{sub 2} ratio that can be incorporated into metal vaporization sub-models run as a post processor to detailed furnace simulations. Vaporization rate controls the formation of metal-enriched sub-micron particles in pulverized coal fired power plants.
Carbon deposition model for oxygen-hydrocarbon combustion, volume 1. Interim final report
Hernandez, R.; Ito, J.I.; Niiya, K.Y.
Presented are details of the design, fabrication, and testing of subscale hardware used in the evaluation of carbon deposition characteristics of liquid oxygen and three hydrocarbon fuels for both main chamber and preburner/gas generator operating conditions. In main chamber conditions, the deposition of carbon on the combustion chamber wall was investigated at mixture ratios of 2.0 to 4.0 and at pressures of 1000 to 1500 psia. No carbon deposition on the chamber walls was detected at these main chamber mixture ratios. In preburner/gas generator operating conditions, the deposition of carbon on the turbine simulator tubes was evaluated at mixture ratios of 0.20 to 0.60 and at chamber pressures of 720 to 1650 psia. The results of the tests showed carbon deposition rate to be a strong function of mixture ratio and a weak function of chamber pressure. Further analyses evaluated the operational consequences of carbon deposition on preburner/gas generator performance. The report is in two volumes, of which this is Volume 1 covering the main body of the report plus Appendixes A through D.
Carbon deposition model for oxygen-hydrocarbon combustion, volume 2. Interim final report
Hernandez, R.; Ito, J.I.; Niiya, K.Y.
Presented are details of the design, fabrication, and testing of subscale hardware used in the evaluation of carbon deposition characteristics of liquid oxygen and three hydrocarbon fuels for both main chamber and preburner/gas generator operating conditions. In main chamber conditions, the deposition of carbon on the combustion chamber wall was investigated at mixture ratios of 2.0 to 4.0 and at chamber pressures of 1000 to 1500 psia. No carbon deposition on chamber walls was detected at these main chamber mixture ratios. In preburner/gas generator operating conditions, the deposition of carbon on the turbine simulator tubes was evaluated at mixture ratios of 0.20 to 0.60 and at chamber pressures of 720 to 1650 psia. The results of the tests showed carbon deposition rate to be a strong function of mixture ratio and a weak function of chamber pressure. Further analyses evaluated the operational concequences of carbon deposition on preburner/gas generator performance. This is Volume 2 of the report, which contains data plots of all the test programs.
Preliminary Study of Oxygen-Enhanced Longitudinal Relaxation in MRI: A Potential Novel Biomarker of Oxygenation Changes in Solid Tumors
O'Connor, James P.B. [Imaging Science and Biomedical Engineering, University of Manchester, Manchester (United Kingdom) and Cancer Research UK Department of Medical Oncology, Christie Hospital, Manchester (United Kingdom); Naish, Josephine H.; Parker, Geoff J.M. [Imaging Science and Biomedical Engineering, University of Manchester, Manchester (United Kingdom); Waterton, John C. [Imaging Science and Biomedical Engineering, University of Manchester, Manchester (United Kingdom); AstraZeneca, Cheshire (United Kingdom); Watson, Yvonne [Imaging Science and Biomedical Engineering, University of Manchester, Manchester (United Kingdom); Jayson, Gordon C. [Cancer Research UK Department of Medical Oncology, Christie Hospital, Manchester (United Kingdom); Buonaccorsi, Giovanni A.; Cheung, Sue; Buckley, David L.; McGrath, Deirdre M. [Imaging Science and Biomedical Engineering, University of Manchester, Manchester (United Kingdom); West, Catharine M.L. [Academic Department of Radiation Oncology, University of Manchester, Manchester (United Kingdom); Davidson, Susan E. [Department of Clinical Oncology, Christie Hospital, Manchester (United Kingdom); Roberts, Caleb; Mills, Samantha J. [Imaging Science and Biomedical Engineering, University of Manchester, Manchester (United Kingdom); Mitchell, Claire L.; Hope, Lynn; Ton, N. Chan [Cancer Research UK Department of Medical Oncology, Christie Hospital, Manchester (United Kingdom); Jackson, Alan [Imaging Science and Biomedical Engineering, University of Manchester, Manchester (United Kingdom)
Purpose: There is considerable interest in developing non-invasive methods of mapping tumor hypoxia. Changes in tissue oxygen concentration produce proportional changes in the magnetic resonance imaging (MRI) longitudinal relaxation rate (R{sub 1}). This technique has been used previously to evaluate oxygen delivery to healthy tissues and is distinct from blood oxygenation level-dependent (BOLD) imaging. Here we report application of this method to detect alteration in tumor oxygenation status. Methods and materials: Ten patients with advanced cancer of the abdomen and pelvis underwent serial measurement of tumor R{sub 1} while breathing medical air (21% oxygen) followed by 100% oxygen (oxygen-enhanced MRI). Gadolinium-based dynamic contrast-enhanced MRI was then performed to compare the spatial distribution of perfusion with that of oxygen-induced DELTAR{sub 1}. Results: DELTAR{sub 1} showed significant increases of 0.021 to 0.058 s{sup -1} in eight patients with either locally recurrent tumor from cervical and hepatocellular carcinomas or metastases from ovarian and colorectal carcinomas. In general, there was congruency between perfusion and oxygen concentration. However, regional mismatch was observed in some tumor cores. Here, moderate gadolinium uptake (consistent with moderate perfusion) was associated with low area under the DELTAR{sub 1} curve (consistent with minimal increase in oxygen concentration). Conclusions: These results provide evidence that oxygen-enhanced longitudinal relaxation can monitor changes in tumor oxygen concentration. The technique shows promise in identifying hypoxic regions within tumors and may enable spatial mapping of change in tumor oxygen concentration.
Effects of EGR, water/N2/CO2 injection and oxygen enrichment on the availability destroyed due to combustion for a range of conditions and fuelsá
Sivadas, Hari Shanker
This study was directed at examining the effects of exhaust gas recirculation (EGR), water/N2/CO2 injections and oxygen enrichment on availability destroyed because of combustion in simple systems like those of constant pressure and constant volume...
Enhanced capability of the Combustion-Heated Scramjet Test Facility
NASA Technical Reports Server (NTRS)
Rock, Kenneth E.; Andrews, Earl H.; Eggers, James M.
The Combustion-Heated Scramjet Test Facility (CHSTF) is described together with its modifications. The expanded simulation capabilities of the facility are documented. Nozzle exit surveys and tunnel calibration information are presented. It is noted that these modifications included a new heat-sink nickel liner heater, a new Mach 4.7 nozzle, and a new 70-ft vacuum sphere exhaust system. It is found that the facility in the air ejector mode of operation performed similarly to that prior to the addition of the vacuum sphere ducting.
Metallized Gelled Propellants: Oxygen/RP-1/Aluminum Rocket Heat Transfer and Combustion Measurements
NASA Technical Reports Server (NTRS)
Palaszewski, Bryan; Zakany, James S.
A series of rocket engine heat transfer experiments using metallized gelled liquid propellants was conducted. These experiments used a small 20- to 40-lb/f thrust engine composed of a modular injector, igniter, chamber and nozzle. The fuels used were traditional liquid RP-1 and gelled RP-1 with 0-, 5-, and 55-percentage by weight loadings of aluminum particles. Gaseous oxygen was used as the oxidizer. Three different injectors were used during the testing: one for the baseline O(2)/RP-1 tests and two for the gelled and metallized gelled fuel firings. Heat transfer measurements were made with a rocket engine calorimeter chamber and nozzle with a total of 31 cooling channels. Each chamber used a water flow to carry heat away from the chamber and the attached thermocouples and flow meters allowed heat flux estimates at each of the 31 stations. The rocket engine Cstar efficiency for the RP-1 fuel was in the 65-69 percent range, while the gelled 0 percent by weight RP-1 and the 5-percent by weight RP-1 exhibited a Cstar efficiency range of 60 to 62% and 65 to 67%, respectively. The 55-percent by weight RP-1 fuel delivered a 42-47% Cstar efficiency. Comparisons of the heat flux and temperature profiles of the RP-1 and the metallized gelled RP-1/A1 fuels show that the peak nozzle heat fluxes with the metallized gelled O2/RP-1/A1 propellants are substantially higher than the baseline O2/RP-1: up to double the flux for the 55 percent by weight RP-1/A1 over the RP-1 fuel. Analyses showed that the heat transfer to the wall was significantly different for the RP-1/A1 at 55-percent by weight versus the RP-1 fuel. Also, a gellant and an aluminum combustion delay was inferred in the 0 percent and 5-percent by weight RP-1/A1 cases from the decrease in heat flux in the first part of the chamber. A large decrease in heat flux in the last half of the chamber was caused by fuel deposition in the chamber and nozzle. The engine combustion occurred well downstream of the injector face based on the heat flux estimates from the temperature measurements.
Highly Efficient Oxygen-Storage Material with Intrinsic Coke Resistance for Chemical Looping Combustion-Based CO2 Capture.
Imtiaz, Qasim; Kurlov, Alexey; Rupp, Jennifer Lilia Marguerite; MŘller, Christoph RŘdiger
Chemical looping combustion (CLC) and chemical looping with oxygen uncoupling (CLOU) are emerging thermochemical CO2 capture cycles that allow the capture of CO2 with a small energy penalty. Here, the development of suitable oxygen carrier materials is a key aspect to transfer these promising concepts to practical installations. CuO is an attractive material for CLC and CLOU because of its high oxygen-storage capacity (20?wt?%), fast reaction kinetics, and high equilibrium partial pressure of oxygen at typical operating temperatures (850-1000?░C). However, despite its promising characteristics, its low Tammann temperature requires the development of new strategies to phase-stabilize CuO-based oxygen carriers. In this work, we report a strategy based on stabilization by co-precipitated ceria (CeO2-x ), which allowed us to increase the oxygen capacity, coke resistance, and redox stability of CuO-based oxygen carriers substantially. The performance of the new oxygen carriers was evaluated in detail and compared to the current state-of-the-art materials, that is, Al2 O3 -stabilized CuO with similar CuO loadings. We also demonstrate that the higher intrinsic oxygen uptake, release, and mobility in CeO2-x -stabilized CuO leads to a three times higher carbon deposition resistance compared to that of Al2 O3 -stabilized CuO. Moreover, we report a high cyclic stability without phase intermixing for CeO2-x -supported CuO. This was accompanied by a lower reduction temperature compared to state-of-the-art Al2 O3 -supported CuO. As a result of its high resistance towards carbon deposition and fast oxygen uncoupling kinetics, CeO2-x -stabilized CuO is identified as a very promising material for CLC- and CLOU-based CO2 capture architectures. PMID:25916240
Plasma torch for ignition, flameholding and enhancement of combustion in high speed flows
NASA Technical Reports Server (NTRS)
O'Brien, Walter F. (Inventor); Billingsley, Matthew C. (Inventor); Sanders, Darius D. (Inventor); Schetz, Joseph A. (Inventor)
Preheating of fuel and injection into a plasma torch plume fro adjacent the plasma torch plume provides for only ignition with reduced delay but improved fuel-air mixing and fuel atomization as well as combustion reaction enhancement. Heat exchange also reduced erosion of the anode of the plasma torch. Fuel mixing atomization, fuel mixture distribution enhancement and combustion reaction enhancement are improved by unsteady plasma torch energization, integral formation of the heat exchanger, fuel injection nozzle and plasma torch anode in a more compact, low-profile arrangement which is not intrusive on a highspeed air flow with which the invention is particularly effective and further enhanced by use of nitrogen as a feedstock material and inclusion of high pressure gases in the fuel to cause effervescence during injection.
Supporting technology for enhanced oil recovery: In-situ combustion predictive model
R. M. Ray; J. D. Munoz
The In-Situ Combustion Predictive Model (ICPM) was developed by Scientific Software-Intercomp for the National Petroleum Council (NPC) for its 1984 survey of US enhanced oil recovery potential (NPC, 1984). The architecture of the ICPM is similar to that of the other predictive models in the series (Paul et al., 1982; Aydelotte and Pope, 1983; Paul et al., 1984): an oil
The Tapioca Bomb: A Demonstration to Enhance Learning about Combustion and Chemical Safety
ERIC Educational Resources Information Center
Keeratichamroen, Wasana; Dechsri, Precharn; Panijpan, Bhinyo; Ruenwongsa, Pintip
In any demonstration to students, producing light and sound usually ensures interest and can enhance understanding and retention of the concepts involved. A guided inquiry (Predict, Observe, Explain: POE) approach was used to involve the students actively in their learning about the explosive combustion of fine flour particles in air in theů
NASA Technical Reports Server (NTRS)
Bulzan, Dan
An overview of the emissions related research being conducted as part of the Fundamental Aeronautics Subsonics Fixed Wing Project is presented. The overview includes project metrics, milestones, and descriptions of major research areas. The overview also includes information on some of the emissions research being conducted under NASA Research Announcements. Objective: Development of comprehensive detailed and reduced kinetic mechanisms of jet fuels for chemically-reacting flow modeling. Scientific Challenges: 1) Developing experimental facilities capable of handling higher hydrocarbons and providing benchmark combustion data. 2) Determining and understanding ignition and combustion characteristics, such as laminar flame speeds, extinction stretch rates, and autoignition delays, of jet fuels and hydrocarbons relevant to jet surrogates. 3) Developing comprehensive kinetic models for jet fuels.
Oxygen Fireflooding: Combustion Tube Tests With Light, Medium, and Heavy Crude Oils
Goutam Shahani; James Hansel
Five light, medium, and heavy crude oils were evaluated in a combustion tube, primarily at 750 and 2,000 psig (5.2 and 13.8 MPa) and with OÔ concentrations between 21 (air) and 95%. The overall characteristics of combustion with OÔ appear to be superior to those with air. For light and medium crude oils, when the combustion are marginal (e.g., at
Metallized Gelled Propellants: Oxygen/RP-1/aluminum Rocket Combustion Experiments
NASA Technical Reports Server (NTRS)
Palaszewski, Bryan; Zakany, James S.
A series of combustion experiments were conducted to measure the specific impulse, Cstar-, and specific-impulse efficiencies of a rocket engine using metallized gelled liquid propellants. These experiments used a small 20- to 40-1bf (89- to 178-N) thrust, modular engine consisting of an injector, igniter, chamber and nozzle. The fuels used were traditional liquid RP-1 and gelled RP-1 with 0-, 5-, and 55-wt% loadings of aluminum and gaseous oxygen was the oxidizer. Ten different injectors were used during the testing: 6 for the baseline 02/RP-1 tests and 4 for the gelled fuel tests which covered a wide range of mixture ratios. At the peak of the Isp versus oxidizer-to-fuel ratio (O/F) data, a range of 93 to 99% Cstar efficiency was reached with ungelled 02/RP-1. A Cstar efficiency range of 75 to 99% was obtained with gelled RP-l (0-wt% RP-1/Al) while the metallized 5-wt% RP-1/Al delivered a Cstar efficiency of 94 to 99% at the peak Isp in the O/F range tested. An 88 to 99% Cstar efficiency was obtained at the peak Isp of the gelled RP1/Al with 55-wt% Al. Specific impulse efficiencies for the 55-wt% RP-1/Al of 67%-83% were obtained at a 2.4:1 expansion ratio. Injector erosion was evident with the 55-wt% testing, while there was little or no erosion seen with the gelled RP-1 with 0- and 5-wt% Al. A protective layer of gelled fuel formed in the firings that minimized the damage to the rocket injector face. This effect may provide a useful technique for engine cooling. These experiments represent a first step in characterizing the performance of and operational issues with gelled RP-1 fuels.
Combustion Stability Characteristics of the Project Morpheus Liquid Oxygen / Liquid Methane Main Engine
NASA Technical Reports Server (NTRS)
Melcher, John C.; Morehead, Robert L.
The project Morpheus liquid oxygen (LOX) / liquid methane (LCH4) main engine is a Johnson Space Center (JSC) designed 5,000 lbf-thrust, 4:1 throttling, pressure-fed cryogenic engine using an impinging element injector design. The engine met or exceeded all performance requirements without experiencing any in- ight failures, but the engine exhibited acoustic-coupled combustion instabilities during sea-level ground-based testing. First tangential (1T), rst radial (1R), 1T1R, and higher order modes were triggered by conditions during the Morpheus vehicle derived low chamber pressure startup sequence. The instability was never observed to initiate during mainstage, even at low power levels. Ground-interaction acoustics aggravated the instability in vehicle tests. Analysis of more than 200 hot re tests on the Morpheus vehicle and Stennis Space Center (SSC) test stand showed a relationship between ignition stability and injector/chamber pressure. The instability had the distinct characteristic of initiating at high relative injection pressure drop at low chamber pressure during the start sequence. Data analysis suggests that the two-phase density during engine start results in a high injection velocity, possibly triggering the instabilities predicted by the Hewitt stability curves. Engine ignition instability was successfully mitigated via a higher-chamber pressure start sequence (e.g., 50% power level vs 30%) and operational propellant start temperature limits that maintained \\cold LOX" and \\warm methane" at the engine inlet. The main engine successfully demonstrated 4:1 throttling without chugging during mainstage, but chug instabilities were observed during some engine shutdown sequences at low injector pressure drop, especially during vehicle landing.
Enhancing the combustible properties of bamboo by torrefaction.
Rousset, Patrick; Aguiar, Clarissa; LabbÚ, Nicole; CommandrÚ, Jean-Michel
Bamboo has wide range of moisture content, low bulk energy density and is difficult to transport, handle, store and feed into existing combustion and gasification systems. Because of its important fuel characteristics such as low ash content, alkali index and heating value, bamboo is a promising energy crop for the future. The aim of this study was to evaluate the effects of torrefaction on the main energy properties of Bambusa vulgaris. Three different torrefaction temperatures were employed: 220, 250 and 280░C. The elemental characteristics of lignite and coal were compared to the torrefied bamboo. The characteristics of the biomass fuels tend toward those of low rank coals. Principal component analysis of FTIR data showed a clear separation between the samples by thermal treatment. The loadings plot indicated that the bamboo samples underwent chemical changes related to carbonyl groups, mostly present in hemicelluloses, and to aromatic groups present in lignin. PMID:21703854
Analytical chemical kinetic investigation of the effects of oxygen, hydrogen, and hydroxyl radicals on hydrogen-air combustion
NASA Technical Reports Server (NTRS)
Carson, G. T., Jr.
Quantitative values were computed which show the effects of the presence of small amounts of oxygen, hydrogen, and hydroxyl radicals on the finite-rate chemical kinetics of premixed hydrogen-air mixtures undergoing isobaric autoignition and combustion. The free radicals were considered to be initially present in hydrogen-air mixtures at equivalence ratios of 0.2, 0.6, 1.0, and 1.2. Initial mixture temperatures were 1100 K, 1200 K, and 1500 K, and pressures were 0.5, 1.0, 2.0, and 4.0 atm. Of the radicals investigated, atomic oxygen was found to be the most effective for reducing induction time, defined as the time to 5 percent of the total combustion temperature rise. The reaction time, the time between 5 percent and 95 percent of the temperature rise, is not decreased by the presence of free radicals in the initial hydrogen-air mixture. Fuel additives which yield free radicals might be used to effect a compact supersonic combustor design for efficient operation in an otherwise reaction-limited combustion regime.
Liquid oxygen/hydrogen testing of a single swirl coaxial injector element in a windowed combustion chamber
NASA Astrophysics Data System (ADS)
Hulka, J.; Makel, D.
A modular, high pressure, liquid rocket single element combustion chamber was developed at Aerojet for use with nonintrusive combustion diagnostics. The hardware is able to accommodate full-size injection elements and includes a recessed annular injector around the single element to provide a source for hot gas background flow, which reduces recirculation in the chamber and provides additional injection mass to elevate chamber pressure. Experiments are being conducted to develop the diagnostics required to characterize a single-element combustion spray field for combustion modeling, benchmark data for CFD model validation, and development of the transfer functions between single element cold flow and multielement hot fire. The latter task is being pursued using an injector element identical to elements that had been previously cold-flow tested in single element tests to ambient backpressure and hot fire tested in a multielement injector. Preliminary tests conducted to date without hydrogen flowing through the annular coaxial orifice of the single element show the general flow characteristics of a reacting, unconfined, liquid oxygen hollow cone swirl spray.
Variation of antioxidative activity and growth enhancement of Brassicaceae induced by low-pressure oxygen plasma
NASA Astrophysics Data System (ADS)
Ono, Reoto; Hayashi, Nobuya
The mechanism of growth enhancement induced by active oxygen species generated in an oxygen plasma is investigated. The plant growth enhancement induced by the active oxygen species would relate to an antioxidative activity, which is one of the biological responses. The amount of generated active oxygen species is varied by the oxygen gas pressure in a low-pressure RF glow discharge plasma. The antioxidative activity of sprouts of Brassicaceae induced by the oxygen plasma is maximized at pressures between 30 and 40 Pa, whereas the antioxidative activity becomes small at around 60 and 80 Pa. The pressure dependence of the antioxidative activity of sprout stems is opposite to that of the stem length of the sprouts. The growth enhancement would be induced by the increase in the concentration of active oxygen species in plants owing to the decrease in the amount of antioxidative substances.
Spiking of Hydrocarbon Fuels with Silanes-based Combustion Enhancers
NASA Astrophysics Data System (ADS)
Hidding, Bernhard; Fikri, Mustapha; Bozkurt, Metehan; Schulz, Christof; Soltner, Theresa; Kornath, Andreas; Pfitzner, Michael; Lang, Martin; Adamczyk, Andrew J.; Broadbelt, Linda; Ellerbrock, Hartwig; Simone, Domenico; Bruno, Claudio
The concept of spiking hydrocarbon fuels such as kerosenes with liquid silicon hydrides in order to render the fuel combination hypergolic and to improve the combustion efficiency is presented and preliminarily analyzed. In view of scarcity of available data, various approaches are used, among them quantum-mechanical ab initio calculations for the thermodynamics and shock-tube measurements for the kinetics of higher, liquid silanes. Based on these results and other data, performance predictions indicate that miscible hydrocarbon/silicon hydride fuels (HC/SH) have the potential to be stored in a single tank, to be hypergolic with many oxidizers, and to yield similar, partly better specific impulses (and volume-specific impulses) than hydrocarbon fuels without silane additives. A variety of hybrid HC/SH fuel combinations seems to be accessible, which might offer the possibility to design a fuel combination with characteristics adjustable in a wide range. The current and future availability of larger amounts of liquid silanes is discussed.
Oxygen-diffusion limited metal combustions in Zr, Ti, and Fe foils: Time- and angle-resolved x-ray diffraction studies
Wei, Haoyan; Yoo, Choong-Shik; Chen, Jing-Yin; Shen, Guoyin (CIW); (WSU)
The transient phase and chemical transformations of diffusion controlled metal combustions in bulk Zr, Ti, and Fe foils have been investigated, in situ, using novel time- and angle-resolved x-ray diffraction (TARXD). The TARXD employs monochromatic synchrotron x-rays and a fast-rotating diffracted beam chopper resolving the diffraction image temporally in time-resolution of {approx}45 {mu}s along the azimuth on a 2D pixel array detector. The metal foil strips (10-25 {mu}m in thickness) are ignited using a pulsed electrical heating with a typical heating rate of {approx}10{sup 6} K/s. The x-ray results indicate that the combustion occurs in molten metals, producing a wide range of stoichiometric solid oxides. It reflects an enhanced oxygen solubility and mobility of molten metals with respect to those of solid metals. However, the initial oxides formed are mainly oxygen-deficient metal oxides of ZrO, TiO, and FeO/Fe{sub 3}O{sub 4} - the lowest suboxides stable at these high temperatures. These transition metal monoxides further react with unreacted molten metals, yielding the secondary products of Zr{sub 3}O, Ti{sub 3}O, and Ti{sub 2}O - but not in FeO/Fe{sub 3}O{sub 4}. On the other hand, the higher stoichiometric oxides of ZrO{sub 2} and TiO{sub 2} are formed in the later time only on the metal surface. These results clearly indicate that the combustion process of metal strips is diffusion limited and strongly depends on the solubility and diffusivity of oxygen into molten metals. The time-resolved diffraction data reveals no evidence for metal oxidation in solids, but a series of temperature-induced polymorphic phase transitions. The dynamic thermal expansibility of Fe measured in the present fast heating experiments is similar to those in static conditions (3.3*10{sup -5}/K vs 3.5*10{sup -5}/K for {alpha}-Fe and 6.5*10{sup -5}/K versus 7.0*10{sup -5}/K for {gamma}-Fe).
Enhancement of Sodium Ion Battery Performance Enabled by Oxygen Vacancies.
Xu, Yang; Zhou, Min; Wang, Xin; Wang, Chengliang; Liang, Liying; Grote, Fabian; Wu, Minghong; Mi, Yan; Lei, Yong
The utilization of oxygen vacancies (OVs) in sodium ion batteries (SIBs) is expected to enhance performance, but as yet it has rarely been reported. Taking the MoO3-x nanosheet anode as an example, for the first time we demonstrate the benefits of OVs on SIB performance. Moreover, the benefits at deep-discharge conditions can be further promoted by an ultrathin Al2 O3 coating. A series of measurements show that the OVs increase the electric conductivity and Na-ion diffusion coefficient, and the promotion from ultrathin coating lies in the effective reduction of cycling-induced solid-electrolyte interphase. The coated nanosheets exhibited high reversible capacity and great rate capability with the capacities of 283.9 (50?mA?g(-1) ) and 179.3?mAh?g(-1) (1?A?g(-1) ) after 100 cycles. This work may not only arouse future attention on OVs for sodium energy storage, but also open up new possibilities for designing strategies to utilize defects in other energy storage systems. PMID:26111350
Progress in an oxygen-carrier reaction kinetics experiment for rotary-bed chemical looping combustion
Jester-Weinstein, Jack (Jack L.)
The design process for an experimental platform measuring reaction kinetics in a chemical looping combustion (CLC) process is documented and justified. To enable an experiment designed to characterize the reaction kinetics ...
Chemical-looping combustion of coal with metal oxide oxygen carriers
Ranjani Siriwardane; Hanjing Tian; George Richards; Thomas Simonyi; James Poston
The combustion and reoxidation properties of direct coal chemical-looping combustion (CLC) over CuO, FeO, COO, NiO, and MnO were investigated using thermogravimetric analysis (TGA) and bench-scale fixed-bed flow reactor studies. When coal is heated in either nitrogen or carbon dioxide (CO), 50% of weight loss was observed because of partial pyrolysis, consistent with the proximate analysis. Among various metal oxides
A series of demonstration tests of the American Combustion, Inc. Thermal Destruction System was performed under the SITE program. his oxygen-enhanced combustion system was retrofit to the rotary kiln incinerator at EPA's Combustion Research Facility. his system's performeance was...
Vapor hydrogen and oxygen isotopes reflect water of combustion in the urban atmosphere.
Gorski, Galen; Strong, Courtenay; Good, Stephen P; Bares, Ryan; Ehleringer, James R; Bowen, Gabriel J
Anthropogenic modification of the water cycle involves a diversity of processes, many of which have been studied intensively using models and observations. Effective tools for measuring the contribution and fate of combustion-derived water vapor in the atmosphere are lacking, however, and this flux has received relatively little attention. We provide theoretical estimates and a first set of measurements demonstrating that water of combustion is characterized by a distinctive combination of H and O isotope ratios. We show that during periods of relatively low humidity and/or atmospheric stagnation, this isotopic signature can be used to quantify the concentration of water of combustion in the atmospheric boundary layer over Salt Lake City. Combustion-derived vapor concentrations vary between periods of atmospheric stratification and mixing, both on multiday and diurnal timescales, and respond over periods of hours to variations in surface emissions. Our estimates suggest that up to 13% of the boundary layer vapor during the period of study was derived from combustion sources, and both the temporal pattern and magnitude of this contribution were closely reproduced by an independent atmospheric model forced with a fossil fuel emissions data product. Our findings suggest potential for water vapor isotope ratio measurements to be used in conjunction with other tracers to refine the apportionment of urban emissions, and imply that water vapor emissions associated with combustion may be a significant component of the water budget of the urban boundary layer, with potential implications for urban climate, ecohydrology, and photochemistry. PMID:25733906
Modeling of the chemical-looping combustion of methane using a Cu-based oxygen-carrier
Abad, Alberto; Adanez, Juan; Garcia-Labiano, Francisco; de Diego, Luis F.; Gayan, Pilar [Instituto de Carboquimica (CSIC), Department of Energy and Environment, Miguel Luesma Castan 4, 50018 Zaragoza (Spain)
A mathematical model for a bubbling fluidized bed has been developed to simulate the performance of the fuel-reactor in chemical-looping combustion (CLC) systems. This model considers both the fluid dynamic of the fluidized bed and freeboard and the kinetics of reduction of the oxygen-carrier, here CuO impregnated on alumina. The main outputs of the model are the conversion of the carrier and the gas composition at the reactor exit, the axial profiles of gas concentrations and the fluid dynamical structure of the reactor. The model was validated using measurements when burning CH{sub 4} in a 10 kW{sub th} prototype using a Cu-based oxygen-carrier. The influence of the circulation rate of solids, the load of fuel gas, the reactor temperature and size of the oxygen-carrier particles were analyzed. Combustion efficiencies predicted by the model showed a good agreement with measurements. Having validated the model, the implications for designing and optimizing a fuel-reactor were as follows. The inventory of solids for a high conversion of the fuel was sensitive to the reactor's temperature, the solids' circulation rate and the extent to which the solids entering to the reactor had been regenerated. The optimal ratio of oxygen-carrier to fuel was found to be 1.7-4 for the Cu-based oxygen-carrier used here. In this range, the inventory of solids to obtain a combustion efficiency of 99.9% at 1073 K was less than 130 kg/MW{sub th}. In addition, the model's results were very sensitive to the resistance to gas diffusing between the emulsion and bubble phases in the bed, to the decay of solids' concentration in the freeboard and to the efficiency contact between gas and solids in the freeboard. Thus, a simplified model, ignoring any restriction to gas and solids contacting each other, will under-predict the inventory of solids by a factor of 2-10. (author)
Determination of fluorine, chlorine and bromine in household products by means of oxygen bomb combustion and ion chromatography.
Zhang, Shuai; Zhao, Tianbo; Wang, Jia; Qu, Xiaoling; Chen, Wei; Han, Yin
A method for routine determination of fluorine, chlorine and bromine in household products was developed and validated. In this work, halogen analyses were made based on oxygen bomb combustion followed by ion chromatography (IC). The chromatographic analysis was performed by an IonPac AS19 hydroxide-selective anion-exchange column, a reagent free ion chromatograph eluent generator and an anion self-regenerating suppressor in 10 min. The response was linear (r ? 0.9995) in the entire investigated domain. The limit of detection for the halogens was in the range of 2 to 9 Î 10(-3) mg/L and the limit of quantification was lower than 8 mg/Kg with 20 ÁL of injection volume. The certified reference material of ERM-EC 681k was pretreated using an oxygen bomb combustion procedure to demonstrate the precision of the proposed method. The quantitative analysis results obtained by IC for the target elements were 797 ▒ 9 mg/Kg chlorine and 786 ▒ 25 mg/Kg bromine, which were in good agreement with the certified values of 800 ▒ 4 mg/Kg chlorine, 770 ▒ 5 mg/Kg bromine for ERM-EC 681k, respectively. This validated method was successfully applied for the analysis of fluorine, chlorine and bromine in household product samples, and the variation of halogen contained among the tested samples was remarkable. PMID:22752184
Early Gaseous Oxygen Enrichment to Enhance Magnetite Pellet Oxidation
NASA Astrophysics Data System (ADS)
Tang, Ming; Cho, Hyeon Jeong; Pistorius, Petrus Christiaan
It is suggested that oxygen enrichment in the gas atmosphere, during continuous heating of magnetite pellets, can cause pellets to be oxidized throughout their volumes, eliminating unoxidized cores. The peculiarities of the oxidation kinetics of magnetite concentrate imply that such oxygen enrichment might be particularly effective at lower temperatures. This suggestion was tested by developing and testing a mixed-control model for pellet oxidation (to allow the sizes of unreacted cores to be predicted), and by experimentally testing the effects of oxygen enrichment at relatively low temperatures ("early oxygen enrichment"). The results confirmed that the extents (depth) of oxidation and pellet strength were both improved significantly by applying oxygen enrichment up to 873 K (600 ░C), as part of a heating cycle up to 1073 K (800 ░C).
Physics and chemistry of the influence of excited molecules on combustion enhancement.
Starik, A M; Loukhovitski, B I; Sharipov, A S; Titova, N S
The paper addresses detailed analysis of kinetic processes in the H2-O2, CO-O2 and CH4-O2-reactive systems upon the presence of singlet oxygen molecules O2(a(1)?g) and [Formula: see text] and the influence of the activation of oxygen molecules in electric discharge on the acceleration of ignition in the H2-O2 and CH4-O2 mixtures. The possibility of the intensification of CO oxidation due to excitation of O2 and N2 molecule vibrations and generation of singlet oxygen molecules is also considered. It is shown that the effect of accelerating the ignition strongly depends on the reduced electric field and, as a consequence, on the composition of discharge plasma as well as on the features of chain mechanism development in oxy-fuel systems. It is revealed that the most effective approach for the intensification of CO oxidation both in the moist air and in the products of hydrocarbon combustion in air is the generation of O2(a(1)?g) molecules by electric discharge. Computations showed that the presence of 1% O2(a(1)?g) in the total oxygen allowed one to convert CO to CO2 even at the temperature T=850-900?K in the time of 10(-2)?s. The excitation of O2 and N2 molecule vibrations is less effective for such a conversion. PMID:26170425
Low oxygen tension enhances endothelial fate of human pluripotent stem cells
Kusuma, Sravanti; Peijnenburg, Elizabeth; Patel, Parth; Gerecht, Sharon
Objective A critical regulator of the developing or regenerating vasculature is low oxygen tension. Precise elucidation of the role of low oxygen environments on endothelial commitment from human pluripotent stem cells (hPSCs) necessitates controlled in vitro differentiation environments. Approach and Results We employed a feeder-free, two-dimensional differentiation system in which we could accurately monitor dissolved oxygen levels during hPSC differentiation toward early vascular cells (EVCs). We found that oxygen uptake rate of differentiating hPSCs is lower in 5% O2 compared to atmospheric conditions. EVCs differentiated in 5% O2 had an increased VEcad expression with clusters of VEcad+ cells surrounded by PDGFR?+ cells. When we assessed the temporal effects of low oxygen differentiation environments, we determined that low oxygen environments during the early stages of EVC differentiation enhance endothelial lineage commitment. EVCs differentiated in 5% O2 exhibited an increased expression of VEcad and CD31 along with their localization to the membrane, enhanced lectin binding and acLDL uptake, rapid cord-like structure formation, and increased expression of arterial EC markers. Inhibition of reactive oxygen species generation during the early stages of differentiation abrogated the endothelial inductive effects of the low oxygen environments. Conclusions Low oxygen tension during early stages of EVC derivation induces endothelial commitment and maturation through the accumulation of reactive oxygen species, highlighting the importance of regulating oxygen tensions during hPSC-vascular differentiation. PMID:24526696
Use of axial membrane vibrations to enhance mass transfer in a hollow tube oxygenator
William B. Krantz; Robert R. Bilodeau; Marc E. Voorhees; Roger J. Elgas
Membrane-oxygenator performance is limited by the mass-transfer resistance on the blood side. The most successful techniques thus far for enhancing oxygenator performance have employed liquid-side pressure pulsations. However, this technique is limited since it causes the least relative motion near the membrane. In this study we explore the use of axial vibrations of a membrane tube bundle to increase oxygen
Effect of Ozone Addition on Combustion Efficiency of Hydrogen: Liquid-Oxygen Propellant in Small Rockets
NASA Technical Reports Server (NTRS)
Miller, Riley O.; Brown, Dwight D.
An experimental study shows that 2 percent by weight ozone in oxygen has little effect on overall reactivity for a range of oxidant-fuel weight ratios from 1 to 6. This conclusion is based on characteristic-velocity measurements in 200-pound-thrust chambers at a pressure of 300 pounds per square inch absolute with low-efficiency injectors. The presence of 9 percent ozone in oxygen also did not affect performance in an efficient chamber. Explosions were encountered when equipment or procedure permitted ozone to concentrate locally. These experiments indicate that even small amounts of ozone in oxygen can cause operational problems.
Biologically enhanced cathode design for improved capacity and cycle life for lithium-oxygen batteries
Oh, Dahyun
Lithium-oxygen batteries have a great potential to enhance the gravimetric energy density of fully packaged batteries by two to three times that of lithium ion cells. Recent studies have focused on finding stable electrolytes ...
Enhancement of electric oxygen-iodine laser performance using a rectangular discharge and longer gain length
Carroll, David L.
Enhancement of electric oxygen-iodine laser performance using a rectangular discharge and longer transition of atomic iodine via a 50% increase in gain length, flow rates, and discharge power. O2 a 1 of Physics. doi:10.1063/1.3269811 The electrically driven oxygen-iodine laser Electri- cOIL that was first
Discharge-driven electric oxygen-iodine laser superlinear enhancement via increasing g0L
Carroll, David L.
Discharge-driven electric oxygen-iodine laser superlinear enhancement via increasing g0L G. F the development of an electric oxygen-iodine laser with higher output using a larger product of gain and gain length, g0L. A factor of 4.4 increase in laser power output on the 1315 nm atomic iodine transition
Enhancement of electric oxygen-iodine laser performance using larger mode volume resonators
Carroll, David L.
Enhancement of electric oxygen-iodine laser performance using larger mode volume resonators Brian S iodine via a 100% increase in the resonator mode volume. O2 a1 is produced by a single rf.4130, 140.4780, 230.5750. The electrically driven oxygen-iodine laser (Electric- OIL) that was first
Super-linear Enhancement of the Electric Oxygen-Iodine Laser David L. Carrolla
Carroll, David L.
Super-linear Enhancement of the Electric Oxygen-Iodine Laser David L. Carrolla , Brian S. Woodardb., Urbana, Illinois, 61801, United States ABSTRACT Continuing experiments with Electric Oxygen-Iodine Laser output on the 1315-nm transition of atomic iodine. The peak output power observed was 538 W. Keywords
Electric Oxygen-Iodine Laser Performance Enhancement using Larger Discharge and Resonator Mode Volumes
Carroll, David L.
Electric Oxygen-Iodine Laser Performance Enhancement using Larger Discharge and Resonator Mode transition of atomic iodine for only a 50% increase in gain length (5.1 cm to 7.6 cm), flow rates that significantly higher power was available in the electric oxygen-iodine laser gas flow which could be extracted
In Situ CO, Oxygen, and Opacity Measurement for Optimizing Combustion Control System Performanceá
Molloy, R. C.
detailed review of the latest state-of-the-art In Situ measurement techniques is provided, including: gas filter correlation spectroscopy (CO), zirconium oxide fuel cell (oxygen), and glass fiber optics based transmissometers (opacity). Recent...
Application of oxygen-enriched combustion for locomotive diesel engines. Phase 1
Poola, R.B.; Sekar, R.R.; Assanis, D.N.
A thermodynamic simulation is used to study the effects of oxygen-enriched intake air on the performance and nitrogen oxide (NO) emissions of a locomotive diesel engine. The parasitic power of the air separation membrane required to supply the oxygen-enriched air is also estimated. For a given constraint on peak cylinder pressure, the gross and net power outputs of an engine operating under different levels of oxygen enrichment are compared with those obtained when a high-boost turbocharged engine is used. A 4% increase in peak cylinder pressure can result in an increase in net engine power of approximately 13% when intake air with an oxygen content of 28% by volume is used and fuel injection timing is retarded by 4 degrees. When the engine is turbocharged to a higher inlet boost, the same increase in peak cylinder pressure improves power by only 4%. If part of the significantly higher exhaust enthalpies available as a result of oxygen enrichment are recovered, the power requirements of the air separator membrane can be met, resulting in substantial net power improvements. Oxygen enrichment reduces particulate and visible smoke emissions but increases NO emissions. However, a combination of retarded fuel injection timing and post-treatment of exhaust gases may be adequate to meet the locomotive diesel engine NO{sub x} standards. Exhaust gas after-treatment and heat recovery would be required to realize the full potential of oxygen enrichment. Economic analysis shows that oxygen-enrichment technology is economically feasible and provides high returns on investment. The study also indicates the strong influence of membrane parasitic requirements and exhaust energy recovery on economic benefits. To obtain an economic advantage while using a membrane with higher parasitic power requirements, it is necessary to recover a part of the exhaust energy.
Turbulence in a gaseous hydrogen-liquid oxygen rocket combustion chamber
NASA Technical Reports Server (NTRS)
Lebas, J.; Tou, P.; Ohara, J.
The intensity of turbulence and the Lagrangian correlation coefficient for a LOX-GH2 rocket combustion chamber was determined from experimental measurements of tracer gas diffusion. A combination of Taylor's turbulent diffusion theory and a numerical method for solving the conservation equations of fluid mechanics was used to calculate these quantities. Taylor's theory was extended to consider the inhomogeneity of the turbulence field in the axial direction of the combustion chamber, and an exponential function was used to represent the Lagrangian correlation coefficient. The results indicate that the value of the intensity of turbulence reaches a maximum of 14% at a location about 7" downstream from the injector. The Lagrangian correlation coefficient associated with this value is given by the above exponential expression where alpha = 10,000/sec.
The influence of oxygen concentration on the combustion of a fuel/oxidizer mixture
Biteau, H. [School of Engineering and Electronics, BRE Centre for Fire Safety Engineering, The University of Edinburgh, Edinburgh EH9 3JL (United Kingdom); Institut National de l'Environnement Industriel et des Risques, Parc Technologique Alata, Verneuil en Halatte (France); Fuentes, A. [Institut Universitaire des Systemes Thermiques Industriels (CNRS UMR 6595), Universite de Provence, 13453 Marseille Cedex 13 (France); Marlair, G. [Institut National de l'Environnement Industriel et des Risques, Parc Technologique Alata, Verneuil en Halatte (France); Torero, J.L. [School of Engineering and Electronics, BRE Centre for Fire Safety Engineering, The University of Edinburgh, Edinburgh EH9 3JL (United Kingdom)
The aim of the present study is to investigate the influence of the O{sub 2} concentration on the combustion behaviour of a fuel/oxidizer mixture. The material tested is a ternary mixture of lactose, starch, and potassium nitrate, which has already been used in an attempt to estimate heat release rate using the FM-Global Fire Propagation Apparatus. It provides a well-controlled combustion chamber to study the evolution of the combustion products when varying the O{sub 2} concentration, between air and low oxidizer conditions. Different chemical behaviours have been exhibited. When the O{sub 2} concentration was reduced beyond 18%, large variations were observed in the CO{sub 2} and CO concentrations. This critical O{sub 2} concentration seems to be the limit before which the material only uses its own oxidizer to react. On the other hand, mass loss did not highlight this change in chemical reactions and remained similar whatever the test conditions. This presumes that the oxidation of CO into CO{sub 2} are due to reactions occurring in the gas phase especially for large O{sub 2} concentrations. This actual behaviour can be verified using a simplified flammability limit model adapted for the current work. Finally, a sensitivity analysis has been carried out to underline the influence of CO concentration in the evaluation of heat release rate using typical calorimetric methods. The results of this study provide a critical basis for the investigation of the combustion of a fuel/oxidizer mixture and for the validation of future numerical models. (author)
Fibronectin coating of oxygenator membranes enhances endothelial cell attachment
Background Extracorporeal membrane oxygenation (ECMO) can replace the lungsĺ gas exchange capacity in refractory lung failure. However, its limited hemocompatibility, the activation of the coagulation and complement system as well as plasma leakage and protein deposition hamper mid- to long-term use and have constrained the development of an implantable lung assist device. In a tissue engineering approach, lining the blood contact surfaces of the ECMO device with endothelial cells might overcome these limitations. As a first step towards this aim, we hypothesized that coating the oxygenatorĺs gas exchange membrane with proteins might positively influence the attachment and proliferation of arterial endothelial cells. Methods Sheets of polypropylene (PP), polyoxymethylpentene (TPX) and polydimethylsiloxane (PDMS), typical material used for oxygenator gas exchange membranes, were coated with collagen, fibrinogen, gelatin or fibronectin. Tissue culture treated well plates served as controls. Endothelial cell attachment and proliferation were analyzed for a period of 4ádays by microscopic examination and computer assisted cell counting. Results Endothelial cell seeding efficiency is within range of tissue culture treated controls for fibronectin treated surfaces only. Uncoated membranes as well as all other coatings lead to lower cell attachment. A confluent endothelial cell layer develops on fibronectin coated PDMS and the control surface only. Conclusions Fibronectin increases endothelial cellsĺ seeding efficiency on different oxygenator membrane material. PDMS coated with fibronectin shows sustained cell attachment for a period of four days in static culture conditions. PMID:23356939
Experimental and analytical study to model temperature profiles and stoichiometry in oxygen-enriched in-situ combustioná
Rodriguez, Jose Ramon
A new combustion zone analytical model has been developed in which the combustion front temperature may be calculated. The model describes in the combustion zone, the amount of fuel burned based on reaction kinetics, the fuel concentration...
Carbon deposition model for oxygen-hydrocarbon combustion. Task 6: Data analysis and formulation of an empirical model
NASA Technical Reports Server (NTRS)
Makel, Darby B.; Rosenberg, Sanders D.
The formation and deposition of carbon (soot) was studied in the Carbon Deposition Model for Oxygen-Hydrocarbon Combustion Program. An empirical, 1-D model for predicting soot formation and deposition in LO2/hydrocarbon gas generators/preburners was derived. The experimental data required to anchor the model were identified and a test program to obtain the data was defined. In support of the model development, cold flow mixing experiments using a high injection density injector were performed. The purpose of this investigation was to advance the state-of-the-art in LO2/hydrocarbon gas generator design by developing a reliable engineering model of gas generator operation. The model was formulated to account for the influences of fluid dynamics, chemical kinetics, and gas generator hardware design on soot formation and deposition.
Oxygen enhances phosphine toxicity for postharvest pest control.
Liu, Yong-Biao
Phosphine fumigations under superatmospheric oxygen levels (oxygenated phosphine fumigations) were significantly more effective than the fumigations under the normal 20.9% atmospheric oxygen level against western flower thrips [Frankliniella occidentalis (Pergande)] adults and larvae, leafminer Liriomyza langei Frick pupae, grape mealybug [Pseudococcus maritimus (Ehrhorn)] eggs, and Indianmeal moth [Plodia interpunctella (HŘbner)] eggs and pupae. In 5-h fumigations with 1,000 ppm phosphine at 5 degrees C, mortalities of western flower thrips increased significantly from 79.5 to 97.7% when oxygen was increased from 20.9 to 40% and reached 99.3% under 80% O2. Survivorships of leafminer pupae decreased significantly from 71.2% under 20.9% O2 to 16.2% under 40% O2 and reached 1.1% under 80% O2 in 24-h fumigations with 500 ppm phosphine at 5 degrees C. Complete control of leafminer pupae was achieved in 24-h fumigations with 1,000 ppm phosphine at 5 degrees C under 60% O2 or higher. Survivorships of grape mealybug eggs also decreased significantly in 48-h fumigations with 1,000 ppm phosphine at 2 degrees C under 60% O2 compared with the fumigations under 20.9% O2. Indian meal moth egg survivorships decreased significantly from 17.4 to 0.5% in responses to an oxygen level increase from 20.9 to 40% in 48-h fumigations with 1,000 ppm phosphine at 10 degrees C and reached 0.2% in fumigations under 80% O2. When the oxygen level was reduced from 20.9 to 15 and 10% in fumigations, survivorships of Indianmeal moth eggs increased significantly from 17.4 to 32.9 and 39.9%, respectively. Increased O2 levels also resulted in significantly lower survival rates of Indianmeal moth pupae in response to 24-h fumigations with 500 and 1,000 ppm phosphine at 10 degrees C and a complete control was achieved in the 1,000 ppm phosphine fumigations under 60% O2. Oxygenated phosphine fumigations have marked potential to improve insecticidal efficacy. Advantages and limitations of oxygenated phosphine fumigation are discussed. PMID:22066172
Regenerable MgO promoted metal oxide oxygen carriers for chemical looping combustion
Siriwardane, Ranjani V.; Miller, Duane D.
The disclosure provides an oxygen carrier comprised of a plurality of metal oxide particles in contact with a plurality of MgO promoter particles. The MgO promoter particles increase the reaction rate and oxygen utilization of the metal oxide when contacting with a gaseous hydrocarbon at a temperature greater than about 725.degree. C. The promoted oxide solid is generally comprised of less than about 25 wt. % MgO, and may be prepared by physical mixing, incipient wetness impregnation, or other methods known in the art. The oxygen carrier exhibits a crystalline structure of the metal oxide and a crystalline structure of MgO under XRD crystallography, and retains these crystalline structures over subsequent redox cycles. In an embodiment, the metal oxide is Fe.sub.2O.sub.3, and the gaseous hydrocarbon is comprised of methane.
Enhancement of hybrid rocket combustion performance using nano-sized energetic particles
NASA Astrophysics Data System (ADS)
Risha, Grant Alexander
Until now, the regression rate of classical hybrid rocket engines have typically been an order of magnitude lower than solid propellant motors; thus, hybrids require a relatively large fuel surface area for a given thrust level. In addition to low linear regression rates, relatively low combustion efficiency (87 to 92%), low mass burning rates, varying oxidizer-to-fuel ratio during operation, and lack of scaling laws have been reported. These disadvantages can be ameliorated by introducing nano-sized energetic powder additives into the solid fuel. The addition of nano-sized energetic particles into the solid fuel enhances performance as measured by parameters such as: density specific impulse, mass and linear burning rates, and thrust. Thermophysical properties of the solid fuel such as density, heat of combustion, thermal diffusivity, and thermal conductivity are also enhanced. The types of nano-sized energetic particles used in this study include aluminum, boron, boron carbide, and some Viton-A coated particles. Since the combustion process of solid fuels in a hybrid rocket engine is governed by the mass flux of the oxidizer entering the combustion chamber, the rate-limiting process is the mixing and reacting of the pyrolysis products of the fuel grain with the incoming oxidizer. The overall goal of this research was to determine the relative propulsive and combustion behavior for a family of newly-developed HTPB-based solid-fuel formulations containing various nano-sized energetic particles. Seventeen formulations contained 13% additive by weight, one formulation (SF4) contained 6.5% additive by weight, and one formulation (SF19) contained 5.65% boron by weight. The two hybrid rocket engines which were used in this investigation were the Long Grain Center-Perforated (LGCP) rocket engine and the X-Ray Transparent Casing (XTC) rocket engine. The smaller scale LGCP rocket engine was used to evaluate all of the formulations because conducting experiments using the LGCP required much less preparation and materials. (Abstract shortened by UMI.)
Self-ignition combustion synthesis of oxygen-doped TiFe
R. Wakabayashi; S. Sasaki; T. Akiyama
This paper describes the Self-Ignition Combustion Synthesis (SICS) of the hydrogen storage alloy Ti1.15FeOx (x=0, 0.024, and 0.050) in a hydrogen atmosphere and the obtained product's hydrogenation properties. Ti, Fe, and ?-Fe2O3 powders were mixed to produce Ti1.15FeOx and uniformly heated to the eutectic temperature 1358K for self-ignition, which occurred after the hydrogenation and decomposition of Ti. The X-ray diffraction
Conversion of Methane to Hydrogen in a Reversible Flow Reactor in the Process of Filtration Combustion of Fuel Mixtures Enriched with Oxygen
NASA Astrophysics Data System (ADS)
Dmitrenko, Yu. M.; Klyovan, R. A.
This paper considers the process of partial oxidation of methane to syngas in a reversible flow reactor in the process of filtration combustion of fuel mixtures enriched with oxygen in an inert porous medium. Experimental studies have been made of the influence of the volume concentration of oxygen in the initial fuel mixture on the basic parameters of the conversion process Ś the maximum temperature in the combustion wave and the composition of reaction products. Investigations have been carried out for fuel mixtures having different calorific values under the same filtration conditions. It has been shown that the addition of oxygen to the initial methane-air mixture permits increasing considerably the efficiency of the conversion process.
Enhancing Hematopoietic Stem Cell Transplantation Efficacy by Mitigating Oxygen Shock.
Mantel, Charlie R; O'Leary, Heather A; Chitteti, Brahmananda R; Huang, XinXin; Cooper, Scott; Hangoc, Giao; Brustovetsky, Nickolay; Srour, Edward F; Lee, Man Ryul; Messina-Graham, Steven; Haas, David M; Falah, Nadia; Kapur, Reuben; Pelus, Louis M; Bardeesy, Nabeel; Fitamant, Julien; Ivan, Mircea; Kim, Kye-Seong; Broxmeyer, Hal E
Hematopoietic stem cells (HSCs) reside in hypoxic niches within bone marrow and cord blood. Yet, essentially all HSC studies have been performed with cells isolated and processed in non-physiologic ambient air. By collecting and manipulating bone marrow and cord blood in native conditions of hypoxia, we demonstrate that brief exposure to ambient oxygen decreases recovery of long-term repopulating HSCs and increases progenitor cells, a phenomenon we term extraphysiologic oxygen shock/stress (EPHOSS). Thus, true numbers of HSCs in the bone marrow and cord blood are routinely underestimated. We linked ROS production and induction ofáthe mitochondrial permeability transition pore (MPTP) via cyclophilin D and p53 as mechanisms of EPHOSS. The MPTP inhibitor cyclosporin A protects mouse bone marrow and human cord blood HSCs from EPHOSS during collection in air, resulting in increased recovery of transplantable HSCs. Mitigating EPHOSS during cell collection and processing by pharmacological means may be clinically advantageous for transplantation. PMID:26073944
Evaluation of Advanced PSA and Oxygen Combustion System for Industrial Furnace Applicationsá
Delano, M. A.; Lagree, D.; Kwan, Y.
of use. In contrast, high purity (99.999% pure) oxygen is produced by the Y. Kwan Energy and Environmental Research Corp. Irvine, CA distillation of liquid air at a remote plant and usually transported to the point of use either as cryogenic liquid... separation. COPYRIGHT ? 1988 UNION CARBIDE CORPORATION s a s t, f . 287 ESL-IE-88-09-51 Proceedings from the Tenth Annual Industrial Energy Technology Conference, Houston, TX, September 13-15, 1988 PERFORMANCE The performance requirement...
Microprocessor Based Combustion Monitoring and Control Systems Utilizing in Situ Opacity, Oxygen and CO Measurementá
Molloy, R. C.
, smog, and gas phase reactions with Other air pollutants. 333 ESL-IE-81-04-58 Proceedings from the Third Industrial Energy Technology Conference Houston, TX, April 26-29, 1981 Excess Air (Excess Oxygen) Sensible Heat Loss - The air (air is 20... or by simultaneously measuring CO as outlined below. Principle of Operation - Modern In Situ CO Analyzers uti lize an advanced infrared negative absorption gas filter correlation technique which takes into account the unique signature of the CO absorption band...
Influence of Surface Oxygen in the Activation of Carbonized Coals by Partial Combustion
J. R. Arthur; E. J. Newitt; M. M. Raftery
IT has long been appreciated that surface compounds as well as gaseous oxides are formed when carbons and oxygen interact. Rhead and Wheeler's original suggestion1 that the so-called surface oxides are intermediates in the overall reaction mechanism is not borne out by more recent work2,3, which shows that at least a proportion of the oxides should be regarded as by-products
Medium-Pressure Hydrogen-Oxygen Combustion Turbine Systems for Utilization of Industrial Waste Heat
NASA Astrophysics Data System (ADS)
Furutani, Hirohide; Uzunow, Nikolaj
Recovery of waste heat is an effective means of achieving energy conservation, and the total amount of industrial waste heat is still notable. However, the value of waste heat as an energy source is low (low exergy). Its utilization therefore requires larger recovery systems with increased costs. The concept of introducing a second, high-quality heat source in the form of H2-O2 combustion in order to improve the system's performance is presented here. System analysis of the combination effect (higher output from combined than from separate sources) was conducted. The investigation results show that the systems under consideration have the potential for significant merits under moderate conditions. The proposed combination of low- and high-quality heat sources also permits reductions in the system size and cost.
John M. Veranth; Gautham Krishnamoorthy
An accurate estimation of the CO/CO{sub 2} ratio at the surface of an ash inclusion in coal during combustion is necessary to predict the equilibrium partial pressure of volatile reduced metal species inside the burning particle and the rate of vaporization of metal oxides. Assumptions that have been made previously for the CO/CO{sub 2} ratio at the surface of mineral inclusions are compared to those obtained from a steady state detailed kinetics code for a single porous particle (SKIPPY). The detailed kinetic simulations from SKIPPY for varying particle sizes and bulk gas compositions were used to develop algebraic expressions for the CO/CO{sub 2} ratio that can be incorporated into metal vaporization sub-models run as a post processor to detailed furnace simulations.
Combustion of solid fuel slabs with gaseous oxygen in a hybrid motor analog
NASA Technical Reports Server (NTRS)
Chiaverini, Martin J.; Harting, George C.; Lu, Yeu-Cherng; Kuo, Kenneth K.; Serin, Nadir; Johnson, David K.
Using a high-pressure, two-dimensional hybrid motor, an experimental investigation was conducted on fundamental processes involved in hybrid rocket combustion. HTPB (Hydroxyl-terminated- Polybutadiene) fuel cross linked with diisocyanate was burned with GOX under various operating conditions. Large amplitude pressure oscillations were encountered in earlier test runs. After identifying the source of instability and decoupling the GOX feed line system and combustion chamber, the pressure oscillations were drastically reduced from +/- 20% of the localized mean pressure to an acceptable range of +/- 1.5%. Embedded fine-wire thermocouples indicated that the surface temperature of the burning fuel was around 1000 K depending upon axial locations and operating conditions. Also, except near the leading-edge region, the subsurface thermal wave profiles in the upstream locations arc thicker than those in the downstream locations since the solid-fuel regression rate, in general, increases with distance along the fuel slab. The recovered solid fuel slabs in the laminar portion of the boundary layer exhibited smooth surfaces, indicating the existence of a liquid melt layer on the burning fuel surface in the upstream region. After the transition section, which displayed distinct transverse striations, the surface roughness pattern became quite random and very pronounced in the downstream turbulent boundary-layer region. Both real time X-ray radiography and ultrasonic pulse-echo techniques were used to determine the instantaneous web thicknesses and instantaneous solid-fuel regression rates over certain portions of the fuel slabs. Globally averaged and axially dependent but time-averaged regression rates were also obtained and presented. Several tests were conducted using, simultaneously, one translucent fuel slab and one fuel slab processed with carbon black powder. The addition of carbon black did not affect the measured regression rates or surface temperatures in comparison to the translucent fuel slabs.
External field enhanced photoemission in silver-cesium-oxygen photocathodes.
Burroughs, E G
Reduction in the surface barrier of silver-cesium-oxygen photocathodes by the application of high external electric fields has been demonstrated by the extension of the photoelectric threshold. Photocurrent for selected wavelengths as a function of field strength have been fitted to Schottky plots; however, the observed shifts in photoelectric threshold are not consistent with this theory. Photoyield increases near threshold of five times have been observed for fields of 10(4) V/cm. In addition, data of thermionic emission as a function of photoelectric threshold and cathode temperature are presented along with a discussion of these parameters and their effect on optimum signal-to-noise ratio. PMID:20072211
Efficiency evaluation of oxygen enrichment in energy conversion processes
Bomelburg, H.J.
The extent to which energy conversion efficiencies can be increased by using oxygen or oxygen-enriched air for combustion was studied. Combustion of most fuels with oxygen instead of air was found to have five advantages: increases combustion temperature and efficiency, improves heat transfer at high temperatures, reduces nitrous oxide emissions, permits a high ration of exhaust gas recirculation and allows combustion of certain materials not combustible in air. The same advantages, although to a lesser degree, are apparent with oxygen-enriched air. The cost-effectiveness of the process must necessarily be improved by about 10% when using oxygen instead of air before such use could become justifiable on purely economic terms. Although such a modest increase appears to be attainable in real situations, this study ascertained that it is not possible to generally assess the economic gains. Rather, each case requires its own evaluation. For certain processes industry has already proven that the use of oxygen leads to more efficient plant operation. Several ideas for essentially new applications are described. Specifically, when oxygen is used with exhaust gas recirculation in external or internal combustion engines. It appears also that the advantages of pulse combustion can be amplified further if oxygen is used. When burning wet fuels with oxygen, direct steam generation becomes possible. Oxygen combustion could also improve processes for in situ gasification of coals, oil shales, peats, and other wet fuels. Enhanced oil recovery by fire flooding methods might also become more effective if oxygen is used. The cold energy contained in liquid oxygen can be substantially recovered in the low end of certain thermodynamic cycles. Further efforts to develop certain schemes for using oxygen for combustion appear to be justified from both the technical and economic viewpoints.
Oxygen-enhanced water gas shift on ceria-supported PdľCu and PtľCu bimetallic catalysts
Junichiro Kugai; Jeffrey T. Miller; Neng Guo; Chunshan Song
Aiming at enhancing H2 production in water gas shift (WGS) for fuel cell application, a small amount of oxygen was added to WGS reaction toward oxygen-enhanced water gas shift (OWGS) on ceria-supported bimetallic PdľCu and PtľCu catalysts. Both CO conversion and H2 yield were found to increase by the oxygen addition. The remarkable enhancement of H2 production by O2 addition
Sulfur evolution in chemical looping combustion of coal with MnFe2O4 oxygen carrier.
Wang, Baowen; Gao, Chuchang; Wang, Weishu; Zhao, Haibo; Zheng, Chuguang
Chemical looping combustion (CLC) of coal has gained increasing attention as a novel combustion technology for its advantages in CO2 capture. Sulfur evolution from coal causes great harm from either the CLC operational or environmental perspective. In this research, a combined MnFe2O4 oxygen carrier (OC) was synthesized and its reaction with a typical Chinese high sulfur coal, Liuzhi (LZ) bituminous coal, was performed in a thermogravimetric analyzer (TGA)-Fourier transform infrared (FT-IR) spectrometer. Evolution of sulfur species during reaction of LZ coal with MnFe2O4 OC was systematically investigated through experimental means combined with thermodynamic simulation. TGA-FTIR analysis of the LZ reaction with MnFe2O4 indicated MnFe2O4 exhibited the desired superior reactivity compared to the single reference oxides Mn3O4 or Fe2O3, and SO2 produced was mainly related to oxidization of H2S by MnFe2O4. Experimental analysis of the LZ coal reaction with MnFe2O4, including X-ray diffraction and X-ray photoelectron spectroscopy analysis, verified that the main reduced counterparts of MnFe2O4 were Fe3O4 and MnO, in good agreement with the related thermodynamic simulation. The obtained MnO was beneficial to stabilize the reduced MnFe2O4 and avoid serious sintering, although the oxygen in MnO was not fully utilized. Meanwhile, most sulfur present in LZ coal was converted to solid MnS during LZ reaction with MnFe2O4, which was further oxidized to MnSO4. Finally, the formation of both MnS and such manganese silicates as Mn2SiO4 and MnSiO3 should be addressed to ensure the full regeneration of the reduced MnFe2O4. PMID:25079636
Study of using oxygen-enriched combustion air for locomotive diesel engines
Poola, R.B.; Sekar, R. [Argonne National Lab., IL (United States); Assanis, D.N. [Michigan Univ., Ann Arbor, MI (United States); Cataldi, G.R. [Association of American Railroads, Washington, DC (United States)
A thermodynamic simulation is used to study effects of O2-enriched intake air on performance and NO emissions of a locomotive diesel engine. Parasitic power of the air separation membrane required to supply the O2-enriched air is also estimated. For a given constraint on peak cylinder pressure, gross and net power output of an engine operating under different levels of O2 enrichment are compared with those obtained when a high-boost turbocharged engine is used. A 4% increase in peak cylinder pressure can result in 13% increase in net engine power when intake air with 28 vol% O2 is used and fuel injection timing retarded by 4 degrees. When the engine is turbocharged to a higher inlet boost, the same increase in peak cylinder pressure can result in only 4% improvement in power. If part of the higher exhaust enthalpies from the O2 enrichment is recovered, the power requirements of the air separator membrane can be met. O2 enrichment with its higher combustion temperatures reduces emissions of particulates and visible smoke but increases NO emissions (by up to 3 times at 26% O2 content). Therefore, exhaust gas after-treatment and heat recovery would be required if the full potential of O2 enrichment for improving the performance of locomotive diesel engines is to be realized.
Enhanced oxidative vaporization of Cr2O3 and chromium by oxygen atoms
NASA Technical Reports Server (NTRS)
Fryburg, G. C.; Kohl, F. J.; Stearns, C. A.
Rates of oxidative vaporization of Cr2O3 have been found to be markedly enhanced in the presence of oxygen atoms. Investigations were conducted over the temperature range 200-1250 C. For Cr2O3 the enhancement was about 10 to the 9th power at 550 C in oxygen containing 2.5% atoms. Rapid oxidative vaporization of bare chromium was observed below 800 C, the rate being about one-half that of Cr2O3. Results are interpreted in terms of thermochemical analysis.
Enhanced electroreduction of oxygen and stripping voltammetry on PdPt nanoparticles
NASA Astrophysics Data System (ADS)
Loganathan, Moorthi; Kakade, Bhalchandra; Swami, Anita; Tamaki, Takanori; Yamaguchi, Takeo
Enhanced oxygen reduction reaction (ORR) on PdPt nanopartiles has been demonstrated after their synthesis using a simple co-precipitation method in presence of reducing agent like N-methylpyrrolidone. Enhancement in the ORR activity of PdPt over commercial Pt catalyst has been discussed based on formation of extent of deleterious oxygenated species on catalytic active sites and the same has been studied quantitatively using stripping voltammetry. An improved specific activity (Is) of 500 ÁA/cm2.Pt for PdPt has been observed versus 200 ÁA/cm2.Pt for Pt catalyst at 0.9 V.
New diagnostic methods for laser plasma- and microwave-enhanced combustion.
Miles, Richard B; Michael, James B; Limbach, Christopher M; McGuire, Sean D; Chng, Tat Loon; Edwards, Matthew R; DeLuca, Nicholas J; Shneider, Mikhail N; Dogariu, Arthur
The study of pulsed laser- and microwave-induced plasma interactions with atmospheric and higher pressure combusting gases requires rapid diagnostic methods that are capable of determining the mechanisms by which these interactions are taking place. New rapid diagnostics are presented here extending the capabilities of Rayleigh and Thomson scattering and resonance-enhanced multi-photon ionization (REMPI) detection and introducing femtosecond laser-induced velocity and temperature profile imaging. Spectrally filtered Rayleigh scattering provides a method for the planar imaging of temperature fields for constant pressure interactions and line imaging of velocity, temperature and density profiles. Depolarization of Rayleigh scattering provides a measure of the dissociation fraction, and multi-wavelength line imaging enables the separation of Thomson scattering from Rayleigh scattering. Radar REMPI takes advantage of high-frequency microwave scattering from the region of laser-selected species ionization to extend REMPI to atmospheric pressures and implement it as a stand-off detection method for atomic and molecular species in combusting environments. Femtosecond laser electronic excitation tagging (FLEET) generates highly excited molecular species and dissociation through the focal zone of the laser. The prompt fluorescence from excited molecular species yields temperature profiles, and the delayed fluorescence from recombining atomic fragments yields velocity profiles. PMID:26170432
Supporting technology for enhanced oil recovery: In-situ combustion predictive model
Ray, R.M.; Munoz, J.D.
The In-Situ Combustion Predictive Model (ICPM) was developed by Scientific Software-Intercomp for the National Petroleum Council (NPC) for its 1984 survey of US enhanced oil recovery potential (NPC, 1984). The architecture of the ICPM is similar to that of the other predictive models in the series (Paul et al., 1982; Aydelotte and Pope, 1983; Paul et al., 1984): an oil rate versus time function for a single pattern is computed, the results of which are passed to the economic calculations. Data for process costs, resevoir development costs, and operating costs, and a pattern schedule if multiple patterns are desired, allow the computation of discounted cash flow and other measures of profitability. A brief summary of the oil recovery and economic calculations for the ICPM is given in Sections 1.2 and 1.3. 12 refs., 15 figs., 24 tabs.
The Enhancing Effects of Hyperbaric Oxygen on Mouse Skin Carcinogenesis
Doguchi, Hiroshi; Saio, Masanao; Kuniyoshi, Shimpei; Matsuzaki, Akiko; Yoshimi, Naoki
The effects of hyperbaric oxygen (HBO) on mouse skin two-stage chemical carcinogenesis were examined. Six-week-old inbred CD-1 female mice were divided into the following five groups: group 1, normoxia and application of 25 nmol 7,12-dimethylbenz[a]anthracene (DMBA) and 8.5 nmol 12-O-tetradecanoylphorbol-13-acetate (TPA) (n=19); group 2, HBO and DMBA/TPA (n=21); group 3, HBO and DMBA/acetone (n=3); group 4, normoxia and acetone (n=3); and group 5, non-treatment group (n=5). HBO was started at the same time as DMBA. Mice were euthanized at 23 weeks after the start of the experiment. Mice in group 2 showed the occurrence of tumors at 8 weeks after the beginning of the experiment, while the occurrence of tumors in mice in group 1 was observed beginning at 9 weeks. There was a difference in occurrence among low-grade papillomas, high-grade papillomas and SCCs in both groups 1 and 2 by the ?2-test at end of the experiment (p<0.05). The Ki-67 labeling indices of tumors revealed that the percentages of positive cells in low-grade papillomas in groups 1 and 2 were 15.27 ▒ 2.54% and 29.67 ▒ 2.82%, respectively (p<0.01). The results suggested that the tumors in group 2, which was treated with HBO, were more progressive than those in group 1, which was not treated with HBO. In this study, HBO accelerated tumor cell proliferation and advanced tumor progression in skin carcinogenesis by DMBA/TPA. PMID:24791069
The Effect of Varying Magnetic Field Gradient on Combustion Dynamic
NASA Astrophysics Data System (ADS)
Suzdalenko, Vera; Zake, Maija; Barmina, Inesa; Gedrovics, Martins
The focus of the recent experimental research is to provide control of the combustion dynamics and complex measurements (flame temperature, heat production rate, and composition of polluting emissions) for pelletized wood biomass using a non-uniform magnetic field that produces magnetic force interacting with magnetic moment of paramagnetic oxygen. The experimental results have shown that a gradient magnetic field provides enhanced mixing of the flame compounds by increasing combustion efficiency and enhancing the burnout of volatiles.
Enhanced formation of sulfate and nitrate associated with the use of oxygenated Fuels
Du, Y.; Ren, Y.; Mangelson, N.F.; Eatough, D.J. [Brigham Young Univ., Provo, UT (United States). Dept. of Chemistry and Biochemistry; Cooper, J.A. [TRC Environmental Corp., Beaverton, OR (United States)
Oxygenated fuels are used in some western mountain valley communities to help in the control of CO during winter inversions. However, it is possible that oxygenated fuel use will increase PM{sub 2.5} concentrations. The oxygen in these fuels may lead to increased concentrations of oxidants. In turn, the concentrations of atmospheric oxidants involved in SO{sub 2} and NO{sub 2} chemistry may increase. This may lead to increased conversion of SO{sub 2} and NO{sub x} to particulate sulfate and nitrate. To explore the possible presence of this enhanced atmospheric chemistry, samples of gas and particulate sulfur and nitrogen oxides were collected in 5/day sample sets during four 3-day inversion episodes at two locations in the urban areas of Utah Valley. Two of the episodes occurred during December 1995 when oxygenated fuels were used in the valley. The last two episodes occurred in February 1996 after the end of oxygenated fuel use on January 15. Fogs were absent during all four episodes. The results indicate that the conversion of SO{sub 2} to sulfate and NO{sub 2} to nitrate are both increased about two-fold during the use of oxygenated fuels, as compared to the non-oxygenated fuel periods. The results, possible chemistry which may be related to the observed differences and implications for attainment of both the present and proposed new PM standard will be presented.
Quantifying NOx for Industrial Combustion Processes
C. E. Baukal; P. B. Eleazer
The objectives of this paper are to (1) identify the problems with many of the units that are used to report and regulate NOx, (2) show how to properly correct NOx measurements for oxygen-enhanced combustion, and (3) recommend a preferred type of NOx unit. The current variety of NOx units make comparisons difficult and can cause considerable confusion. NOx may
Simultaneous imaging of tumor oxygenation and microvascular permeability using Overhauser enhanced MRI
Matsumoto, Shingo; Yasui, Hironobu; Batra, Sonny; Kinoshita, Yuichi; Bernardo, Marcelino; Munasinghe, Jeeva P.; Utsumi, Hideo; Choudhuri, Rajani; Devasahayam, Nallathamby; Subramanian, Sankaran; Mitchell, James B.; Krishna, Murali C.
Architectural and functional abnormalities of blood vessels are a common feature in tumors. A consequence of increased vascular permeability and concomitant aberrant blood flow is poor delivery of oxygen and drugs, which is associated with treatment resistance. In the present study, we describe a strategy to simultaneously visualize tissue oxygen concentration and microvascular permeability by using a hyperpolarized 1H-MRI, known as Overhauser enhanced MRI (OMRI), and an oxygen-sensitive contrast agent OX63. Substantial MRI signal enhancement was induced by dynamic nuclear polarization (DNP). The DNP achieved up to a 7,000% increase in MRI signal at an OX63 concentration of 1.5 mM compared with that under thermal equilibrium state. The extent of hyperpolarization is influenced mainly by the local concentration of OX63 and inversely by the tissue oxygen level. By collecting dynamic OMRI images at different hyperpolarization levels, local oxygen concentration and microvascular permeability of OX63 can be simultaneously determined. Application of this modality to murine tumors revealed that tumor regions with high vascular permeability were spatio-temporally coincident with hypoxia. Quantitative analysis of image data from individual animals showed an inverse correlation between tumor vascular leakage and median oxygen concentration. Immunohistochemical analyses of tumor tissues obtained from the same animals after OMRI experiments demonstrated that lack of integrity in tumor blood vessels was associated with increased tumor microvascular permeability. This dual imaging technique may be useful for the longitudinal assessment of changes in tumor vascular function and oxygenation in response to chemotherapy, radiotherapy, or antiangiogenic treatment. PMID:19815528
Simultaneous imaging of tumor oxygenation and microvascular permeability using Overhauser enhanced MRI.
Matsumoto, Shingo; Yasui, Hironobu; Batra, Sonny; Kinoshita, Yuichi; Bernardo, Marcelino; Munasinghe, Jeeva P; Utsumi, Hideo; Choudhuri, Rajani; Devasahayam, Nallathamby; Subramanian, Sankaran; Mitchell, James B; Krishna, Murali C
Architectural and functional abnormalities of blood vessels are a common feature in tumors. A consequence of increased vascular permeability and concomitant aberrant blood flow is poor delivery of oxygen and drugs, which is associated with treatment resistance. In the present study, we describe a strategy to simultaneously visualize tissue oxygen concentration and microvascular permeability by using a hyperpolarized (1)H-MRI, known as Overhauser enhanced MRI (OMRI), and an oxygen-sensitive contrast agent OX63. Substantial MRI signal enhancement was induced by dynamic nuclear polarization (DNP). The DNP achieved up to a 7,000% increase in MRI signal at an OX63 concentration of 1.5 mM compared with that under thermal equilibrium state. The extent of hyperpolarization is influenced mainly by the local concentration of OX63 and inversely by the tissue oxygen level. By collecting dynamic OMRI images at different hyperpolarization levels, local oxygen concentration and microvascular permeability of OX63 can be simultaneously determined. Application of this modality to murine tumors revealed that tumor regions with high vascular permeability were spatio-temporally coincident with hypoxia. Quantitative analysis of image data from individual animals showed an inverse correlation between tumor vascular leakage and median oxygen concentration. Immunohistochemical analyses of tumor tissues obtained from the same animals after OMRI experiments demonstrated that lack of integrity in tumor blood vessels was associated with increased tumor microvascular permeability. This dual imaging technique may be useful for the longitudinal assessment of changes in tumor vascular function and oxygenation in response to chemotherapy, radiotherapy, or antiangiogenic treatment. PMID:19815528
Detection of Molecular Oxygen at Low Concentrations Using Quartz Enhanced Photoacoustic Spectroscopy
Pohlk÷tter, Andreas; K÷hring, Michael; Willer, Ulrike; Schade, Wolfgang
Molecular oxygen is detected at low concentrations using photoacoustic spectroscopy despite its unfavorable photoacoustic properties. The system consists of a seed laser diode, a tapered amplifier and a quartz tuning fork based spectrophone, thus employing quartz enhanced photoacoustic spectroscopy (QEPAS). With this system a detection limit of 13 ppm is reached with a compact and long term stable setup. Further improvement of the detection limit is possible by adding suitable gases to the sample gas that promote the radiationless de-excitation of the oxygen molecules. PMID:22163666
Chronic Lung Allograft Dysfunction: Oxygen-enhanced T1-Mapping MR Imaging of the Lung.
Renne, Julius; Lauermann, Peer; Hinrichs, Jan B; Sch÷nfeld, Christian; Sorrentino, Sajoscha; Gutberlet, Marcel; Jakob, Peter; Haverich, Axel; Warnecke, Gregor; Welte, Tobias; Wacker, Frank K; Gottlieb, Jens; Vogel-Claussen, Jens
Purpose To evaluate oxygen-enhanced T1-mapping magnetic resonance (MR) imaging of the lungs for detection of chronic lung allograft dysfunction (CLAD) in patients who have undergone double lung transplantation. Materials and Methods The local ethics committee approved this study. Seventy-six recipients of double lung allografts who underwent MR imaging of the lungs during an outpatient visit between 2011 and 2013 were included in this study after they provided written informed consent. Patients were classified as having CLAD on the basis of spirometric results and were divided into three groups: no CLAD (bronchiolitis obliterans syndrome level 0 [BOS 0]), early CLAD (BOS 0p), and late-stage CLAD (BOS 1-3). Coronal T1 maps of the lungs were acquired with the patient breathing room air and 100% oxygen by using an inversion-recovery snapshot fast low-angle shot sequence at 1.5 T. The median and interquartile range of T1 values at room air and at 100% oxygen and the oxygen transfer function were calculated. Statistical analysis was performed with analysis of variance and the Tukey honestly significant difference test or the Kruskal-Wallis test and the Mann-Whitney U test (? = 0.05). Bonferroni correction was applied for multiple comparisons. Results The oxygen transfer function was significantly lower in patients in the BOS 0p (P = .025) and BOS 1-3 groups (P = .003) than it was in the patients with BOS 0. Absolute T1 values (room air, P = .66; 100% oxygen, P = .67) did not differ significantly among the groups. The heterogeneity of T1 values, measured by using the interquartile range, showed a strong trend toward higher values in patients with BOS (room air, P = .06; 100% oxygen, P = .08). Conclusion Oxygen transfer function may serve as an early marker for detection of CLAD. (ę) RSNA, 2015 Online supplemental material is available for this article. PMID:25816104
Liquid oxygen\\/hydrogen testing of a single swirl coaxial injector element in a windowed combustion chamber
J. Hulka; D. Makel
A modular, high pressure, liquid rocket single element combustion chamber was developed at Aerojet for use with nonintrusive combustion diagnostics. The hardware is able to accommodate full-size injection elements and includes a recessed annular injector around the single element to provide a source for hot gas background flow, which reduces recirculation in the chamber and provides additional injection mass to
Investigation of chemical looping combustion by solid fuels. 2. redox reaction kinetics and product characterization with coal, biomass, and solid waste as solid fuels and CuO as an oxygen carrier
Yan Cao; Bianca Casenas; Wei-Ping Pan
This paper is the second in a series of two on the investigation of the chemical looping combustion (CLC) of solid fuels. The first paper put forward the concept of the CLC of solid fuels using a circulating fluidized bed as a reactor and Cu-CuO as the oxygen carrier, which was based on an analysis of oxygen transfer capability, reaction
Combustion optimization in a hydrogen-enhanced lean burn SI engine
Goldwitz, Joshua A. (Joshua Arlen), 1980-
Lean operation of spark ignition (SI) automotive engines offers attractive performance incentives. Lowered combustion temperatures inhibit NO[sub]x pollutant formation while reduced manifold throttling minimizes pumping ...
Enhancement of fine-scale mixing for fuel-rich plume combustion
NASA Astrophysics Data System (ADS)
Schadow, K. C.; Gutmark, E.; Parr, T. P.; Parr, D. M.; Wilson, K. J.; Ferrell, G. B.
The effect of enhancing small-scale turbulent structures on the combustion intensity and flame stability was studied in nonreacting and reacting flows. Hot-wire anemometry was used to map the mean and turbulent flow fields of the nonreacting flows. Reacting flows were studied in a free flame and in a ducted gas-generator fuel-rich plume using Planar Laser Induced Fluorescence, a rake of thermocouples and high speed photography. A modified circular nozzle having several backward facing steps upstream of its exit was used to introduce numerous inflection points in the initial mean velocity profiles, thus producing multiple corresponding sources of small-scale turbulence generators. Cold flow tests showed turbulence increases of up to six times the initial turbulence level relative to a circular nozzle. The ensuing result was that the flame of this nozzle was more intense with a homogeneous heat release. The fuel-rich plume was stable even in supersonic speeds, and secondary ignition was obtained under conditions that prevented sustained afterburning using the circular nozzle.
Icariin enhances neuronal survival after oxygen and glucose deprivation by increasing SIRT1
Lin Wang; Ling Zhang; Zhi-Bin Chen; Jia-Yong Wu; Xin Zhang; Yun Xu
It has been reported that icariin protects neurons against ischemia\\/reperfusion injury. In this study, we found that icariin could enhance neuronal viability and suppress neuronal death after oxygen and glucose deprivation (OGD). Further study showed that neuroprotection by icariin was through the induction of Sirtuin type 1 (SIRT1), an effect that was reversed by SIRT1 inhibitor III and P38 inhibitor
Water and oxygen permeation of silicon nitride films prepared by plasma-enhanced chemical vapor deposition
D. S. Wuu; W. C. Lo; C. C. Chiang; H. B. Lin; L. S. Chang; R. H. Horng; C. L. Huang; Y. J. Gao
Silicon nitride (SiNx) films deposited on flexible polyethersulfone (PES) substrates by plasma-enhanced chemical vapor deposition (PECVD) have been investigated for water vapor transmission rate (WVTR) and oxygen transmission rate (OTR) barrier applications. Details of the NH3\\/SiH4 flow ratio and chamber pressure effects on the SiNx\\/PES properties in terms of chemical bonding, transmittance, refractive index, deposition rate, adhesion, roughness, OTR and
A detailed chemical analysis of changes to bitumen produced by the in situ combustion process at the oxygen Wolf Lake Project, Alberta. Part 11; Whole oil samples
Alex, R.F.; Fuhr, B.; Reichert, C. (Alberta Research Council, Oil Sands and Hydrocarbon Recovery, Edmonton, Alberta T6H 5X2 (CA))
The detailed chemical changes in bitumen brought about over a one year period by a in situ combustion process in an oil sands reservoir have been investigated. Relative to a core sample, the fireflood-produced oils exhibited a significant reduction in density and viscosity which began early in the production cycle. This behavior was correlated with a marked increase in material boiling in the naphtha and middle distillate ranges and a concomitant decrease in the residue cut. The sulfur and nitrogen contents in the produced oils decreased relative to the core sample. A reduction in the acid number of the produced oil samples was coupled with an increase in the oxygen content as the fireflood proceeded. In this paper the relationship between these changes and the dynamics of the in situ combustion process are discussed.
Enhancement of oxidative vaporization of chromium (III) oxide and chromium by oxygen atoms
NASA Technical Reports Server (NTRS)
Fryburg, G. C.; Kohl, F. J.; Stearns, C. A.
Rates of oxidative vaporization of Cr2O3 were found to be markedly enhanced in the presence of O atoms. Investigations were conducted over the temperature range 470 to 1520 K. For Cr2O3 the enhancement was about 10 to the 9th power at 820 K in oxygen containing 2.5 percent atoms. Rapid oxidative vaporization of bare chromium was observed below 1070 K, the rate being about one-half that of Cr2O3. Results are interpreted in terms of thermochemical analysis.
Ultraviolet Irradiation-Dependent Fluorescence Enhancement of Hemoglobin Catalyzed by Reactive Oxygen Species
Pan, Leiting; Wang, Xiaoxu; Yang, Shuying; Wu, Xian; Lee, Imshik; Zhang, Xinzheng; Rupp, Romano A.; Xu, Jingjun
Ultraviolet (UV) light has a potent effect on biological organisms. Hemoglobin, an oxygen-transport protein, plays an irreplaceable role in sustaining life of all vertebrates. In this study we scrutinize the effects of ultraviolet irradiation (UVI) as well as visible irradiation on the fluorescence characteristics of bovine hemoglobin (BHb) in vitro. Data show that UVI results in fluorescence enhancement of BHb in a dose-dependant manner. Furthermore, UVI-induced fluorescence enhancement is significantly increased when BHb is pretreated with hydrogen peroxide (H2O2), a type of reactive oxygen species (ROS). Meanwhile, The water-soluble antioxidant vitamin C suppresses this UVI-induced fluorescence enhancement. In contrast, green light irradiation does not lead to fluorescence enhancement of BHb no matter whether H2O2 is acting on the BHb solution or not. Taken together, these results indicate that catalysis of ROS and UVI-dependent irradiation play two key roles in the process of UVI-induced fluorescence enhancement of BHb. PMID:22952902
Enhanced oxygen separation through robust freeze-cast bilayered dual-phase membranes.
Gaudillere, Cyril; Garcia-Fayos, Julio; Balaguer, MarÝa; Serra, JosÚ M
Dual-phase oxygen-permeable asymmetric membranes with enhanced oxygen permeation were prepared by combining freeze-casting, screen-printing, and constraint-sintering techniques. The membranes were evaluated under oxyfuel operating conditions. The prepared membranes are composed of an original ice-templated La(0.6)Sr(0.4)Co(0.2)Fe(0.8)O(3-?) support with hierarchically oriented porosity and a top fully densified bilayered coating comprising a 10??m-thick La(0.6)Sr(0.4)Co(0.2)Fe(0.8)O(3-?) layer and a top protective 8??m-thick layer made of an optimized NiFe2O4/Ce(0.8)Tb(0.2)O(2-?) composite synthesized by the one-pot Pechini method. Preliminary analysis confirmed the thermochemical compatibility of the three involved phases at high temperature without any additional phase detected. This membrane exhibited a promising oxygen permeation value of 4.8?mL?min(-1) ?cm(-2) at 1000?░C upon using Ar and air as the sweep and feed gases, respectively. Mimicking oxyfuel operating conditions by switching argon to pure CO2 as a sweep gas at 1000?░C and air as feed enabled an oxygen flux value of 5.6?mL?min(-1) ?cm(-2) to be reached. Finally, under the same conditions and increasing the oxygen partial pressure to 0.1?MPa in the feed, the oxygen permeation reached 12?mL?min(-1) ?cm(-2). The influence of CO2 content in the sweep gas was studied and its reversible and positive effect over oxygen permeation at temperatures equal to or above 950?░C was revealed. Finally, the membrane stability over a period of 150?h under CO2-rich sweep gas showed a low degradation rate of 2.4Î10(-2) ?mL?min(-1) ?cm(-2) per day. PMID:25070608
Comparative investigation on chemical looping combustion of coal-derived synthesis gas containing H2S over supported NiO oxygen carriers
Ksepko, E.; Siriwardane, R.; Tian, H.; Simonyi, T.; Sciazko, M.
Chemical looping combustion (CLC) of simulated coal-derived synthesis gas was conducted with NiO oxygen carriers supported on SiO2, ZrO2, TiO2, and sepiolite. The effect of H2S on the performance of these samples for the CLC process was also evaluated. Five-cycle thermogravimetric analysis (TGA) tests at 800 #1;C indicated that all oxygen carriers had a stable performance at 800 #1;C, except NiO/SiO2. Full reduction/oxidation reactions of the oxygen carrier were obtained during the five-cycle test. It was found that support had a significant effect on reaction performance of NiO both in reduction and oxidation rates. The reduction reaction was significantly faster than the oxidation reaction for all oxygen carriers, while the oxidation reaction is fairly slow due to oxygen diffusion on NiO layers. The reaction profile was greatly affected by the presence of H2S, but there was no effect on the capacity due to the presence of H2S in synthesis gas. The presence of H2S decreased reduction reaction rates significantly, but oxidation rates of reduced samples increased. X-ray diffraction (XRD) data of the oxidized samples after a five-cycle test showed stable crystalline phases without any formation of sulfides or sulfites/sulfates. Increase in reaction temperature to 900 #1;C had a positive effect on the performance.
Design and implementation of Carbon Monoxide and Oxygen emissions measurement in swirl-stabilized oxy-fuel combustion
Sommer, Andrew (Andrew Zhang)
Oxy-fuel combustion in natural gas power generation is a technology of growing interest as it provides the most efficient means of carbon capture. Since all the emissions from these power plants are sequestered, there are ...
Ultraviolet irradiation induces autofluorescence enhancement via production of reactive oxygen species and photodecomposition in erythrocytes
Wu, Xian [The Key Laboratory of Weak-Light Nonlinear Photonics, Ministry of Education, TEDA Applied Physics School and School of Physics, Nankai University, Tianjin 300457 (China)] [The Key Laboratory of Weak-Light Nonlinear Photonics, Ministry of Education, TEDA Applied Physics School and School of Physics, Nankai University, Tianjin 300457 (China); Pan, Leiting, E-mail: email@example.com [The Key Laboratory of Weak-Light Nonlinear Photonics, Ministry of Education, TEDA Applied Physics School and School of Physics, Nankai University, Tianjin 300457 (China)] [The Key Laboratory of Weak-Light Nonlinear Photonics, Ministry of Education, TEDA Applied Physics School and School of Physics, Nankai University, Tianjin 300457 (China); Wang, Zhenhua; Liu, Xiaoli; Zhao, Dan; Zhang, Xinzheng; Rupp, Romano A. [The Key Laboratory of Weak-Light Nonlinear Photonics, Ministry of Education, TEDA Applied Physics School and School of Physics, Nankai University, Tianjin 300457 (China)] [The Key Laboratory of Weak-Light Nonlinear Photonics, Ministry of Education, TEDA Applied Physics School and School of Physics, Nankai University, Tianjin 300457 (China); Xu, Jingjun, E-mail: email@example.com [The Key Laboratory of Weak-Light Nonlinear Photonics, Ministry of Education, TEDA Applied Physics School and School of Physics, Nankai University, Tianjin 300457 (China)] [The Key Laboratory of Weak-Light Nonlinear Photonics, Ministry of Education, TEDA Applied Physics School and School of Physics, Nankai University, Tianjin 300457 (China)
Ultraviolet (UV) light has a significant influence on human health. In this study, human erythrocytes were exposed to UV light to investigate the effects of UV irradiation (UVI) on autofluorescence. Our results showed that high-dose continuous UVI enhanced erythrocyte autofluorescence, whereas low-dose pulsed UVI alone did not have this effect. Further, we found that H{sub 2}O{sub 2}, one type of reactive oxygen species (ROS), accelerated autofluorescence enhancement under both continuous and pulsed UVI. In contrast, continuous and pulsed visible light did not result in erythrocyte autofluorescence enhancement in the presence or absence of H{sub 2}O{sub 2}. Moreover, NAD(P)H had little effect on UVI-induced autofluorescence enhancement. From these studies, we conclude that UVI-induced erythrocyte autofluorescence enhancement via both UVI-dependent ROS production and photodecomposition. Finally, we present a theoretical study of this autofluorescence enhancement using a rate equation model. Notably, the results of this theoretical simulation agree well with the experimental data further supporting our conclusion that UVI plays two roles in the autofluorescence enhancement process.
Gain and continuous-wave laser power enhancement with a multiple discharge electric oxygen-iodine laser
Carroll, David L.
Gain and continuous-wave laser power enhancement with a multiple discharge electric oxygen-iodine transition of atomic iodine via an increase in flow rates and pressure using multiple discharges in an electric oxygen-iodine laser. O2 a 1 is produced by two parallel radio-frequency-excited electric
Ignition delays, heats of combustion, and reaction rates of aluminum alkyl derivatives used as ignition and combustion enhancers for supersonic combustion
NASA Technical Reports Server (NTRS)
Ryan, Thomas W., III; Schwab, S. T.; Harlowe, W. W.
The subject of this paper is the design of supersonic combustors which will be required in order to achieve the needed reaction rates in a reasonable sized combustor. A fuel additive approach, which is the focus of this research, is the use of pyrophorics to shorten the ignition delay time and to increase the energy density of the fuel. Pyrophoric organometallic compounds may also provide an ignition source and flame stabilization mechanism within the combustor, thus permitting use of hydrocarbon fuels in supersonic combustion systems. Triethylaluminum (TEA) and trimethylaluminum (TMA) were suggested for this application due to their high energy density and reactivity. The objective here is to provide comparative data for the ignition quality, the energy content, and the reaction rates of several different adducts of both TEA and TMA. The results of the experiments indicate the aluminum alkyls and their more stable derivatives reduce the ignition delay and total reaction time to JP-10 jet fuel. Furthermore, the temperature dependence of ignition delay and total reaction time of the blends of the adducts are significantly lower than in neat JP-10.
Environmental enhancement of creep crack growth in Inconel 718 by oxygen and water vapor
Valerio, P.; Gao, M.; Wei, R.P. (Lehigh Univ., Bethlehem, PA (United States). Dept. of Mechanical Engineering and Mechanics)
Inconel 718 alloy is widely used in high temperature applications. Because of its sensitivity to environmentally enhanced crack growth at high temperatures, its use has been limited to modest temperatures (i.e., below 973 K). To improve its performance and to better predict its service life, it is important to develop a better understanding of the processes of crack growth at high temperatures in this alloy. It has been shown that the creep crack growth rates (CCGR) in air are at least two orders of magnitude faster than those in vacuum or inert environments. CCGR were also found to depend strongly on temperature. Fractographic studies showed that crack growth was intergranular in air and in vacuum with brittle appearing grain boundary separation in air and extensive cavity formation in vacuum. The increased CCGR in air has been attributed to the enhancement by oxygen; principally through enhanced cavity nucleation and growth by high-pressure carbon monoxide/dioxide formed by the reactions of oxygen that diffused into the material with the grain boundary carbides. The appropriateness of this mechanism, however, may be questioned by the absence of cavitation on the crack surfaces produced in air. As such the mechanism for crack growth needs to be re-examined. Because of the presence of moisture in air, the possible influence of hydrogen needs to be considered as well. In this study, preliminary experiments were conducted to examine the process of environmentally enhanced creep crack growth in Inconel 718 alloy in terms of possible mechanisms and rate controlling processes. Creep crack growth experiments were carried out in air, oxygen (from 2.67 to 100 kPa), moist argon (water vapor) and pure argon at temperatures from 873 to 973 K.
Multicolor tunability and upconversion enhancement of fluoride nanoparticles by oxygen dopant.
Niu, Wenbin; Wu, Suli; Zhang, Shufen; Su, Liap Tat; Tok, Alfred Iing Yoong
The ability to manipulate the upconversion luminescence of lanthanide-ion doped fluoride upconversion nanoparticles (UCNPs) is particularly important and highly desired due to their wide applications in color displays, multiplexing bioassays and multicolor imaging. Here, we developed a strategy for simultaneously tuning color output and enhancing upconversion emission of Yb/Er doped fluoride UCNPs, based on adjusting the oxygen doping level. The synthesis of multicolored multifunctional NaGdF4:Yb,Er UCNPs was used as the model host system to demonstrate this protocol. Ammonium nitrate (NH4NO3) was used as the oxygen source and added into the reaction system at the beginning stage of nucleation and growth process of fluoride UCNPs, which facilitates the formation of enough oxygen atoms and the diffusion of these into the fluoride host matrix. The results revealed that multicolour output and upconversion enhancement mainly resulted from the variation of phonon energy and crystal field symmetry of the host lattice, respectively. This strategy can be further expanded to other fluoride host matrices. As an example of an application, multicolored UCNPs were used as a color converter in light emitting diodes, which can effectively convert near-infrared light into visible light. It is expected that these multicolored UCNPs will be promising for applications in multiplexing biodetection, bioimaging (optical and magnetic resonance imaging) and other optical technologies, and the present method for the control of O(2-) doping may also be used in other functional nanomaterials. PMID:23887282
Biologically enhanced cathode design for improved capacity and cycle life for lithium-oxygen batteries
Oh, Dahyun; Qi, Jifa; Lu, Yi-Chun; Zhang, Yong; Shao-Horn, Yang; Belcher, Angela M.
Lithium-oxygen batteries have a great potential to enhance the gravimetric energy density of fully packaged batteries by 2ľ3 times that of lithium-ion cells. Recent studies have focused on finding stable electrolytes to address poor cycling capability and improve practical limitations of current lithium-oxygen batteries. In this study, the catalyst electrode, where discharge products are deposited and decomposed, was investigated since it plays a critical role in the operation of rechargeable lithium-oxygen batteries. Here we report the electrode design principle to improve specific capacity and cycling performance of lithium-oxygen batteries by utilizing high efficiency nanocatalysts assembled by M13 virus with earth abundant elements, such as manganese oxides. By incorporating only 3ľ5 wt % of palladium nanoparticles in the electrode, this hybrid nanocatalyst achieves 13,350 mAh g?1c (7,340 mAh g?1c+catalyst) of specific capacity at 0.4 A g?1c and a stable cycle life up to 50 cycles (4,000 mAh g?1c, 400 mAh g?1c+catalyst) at 1 A g?1c. PMID:24220635
Combustion-derived flame generated ultrafine soot generates reactive oxygen species and activates Nrf2 antioxidants differently in neonatal and adult rat lungs
Background Urban particulate matter (PM) has been epidemiologically correlated with multiple cardiopulmonary morbidities and mortalities, in sensitive populations. Children exposed to PM are more likely to develop respiratory infections and asthma. Although PM originates from natural and anthropogenic sources, vehicle exhaust rich in polycyclic aromatic hydrocarbons (PAH) can be a dominant contributor to the PM2.5 and PM0.1 fractions and has been implicated in the generation of reactive oxygen species (ROS). Objectives Current studies of ambient PM are confounded by the variable nature of PM, so we utilized a previously characterized ethylene-combusted premixed flame particles (PFP) with consistent and reproducible physiochemical properties and 1) measured the oxidative potential of PFP compared to ambient PM, 2) determined the ability of PFPs to generate oxidative stress and activate the transcription factor using in vitro and ex vivo models, and 3) we correlated these responses with antioxidant enzyme expression in vivo. Methods We compared oxidative stress response (HMOX1) and antioxidant enzyme (SOD1, SOD2, CAT, and PRDX6) expression in vivo by performing a time-course study in 7-day old neonatal and young adult rats exposed to a single 6-hour exposure to 22.4 ?g/m3 PFPs. Results We showed that PFP is a potent ROS generator that induces oxidative stress and activates Nrf2. Induction of the oxidative stress responsive enzyme HMOX1 in vitro was mediated through Nrf2 activation and was variably upregulated in both ages. Furthermore, antioxidant enzyme expression had age and lung compartment variations post exposure. Of particular interest was SOD1, which had mRNA and protein upregulation in adult parenchyma, but lacked a similar response in neonates. Conclusions We conclude that PFPs are effective ROS generators, comparable to urban ambient PM2.5, that induce oxidative stress in neonatal and adult rat lungs. PFPs upregulate a select set of antioxidant enzymes in young adult animals, that are unaffected in neonates. We conclude that the inability of neonatal animals to upregulate the antioxidant response may, in part, explain enhanced their susceptibility to ultrafine particles, such as PFP. PMID:23902943
Chemical kinetic modeling of oxy-fuel combustion of sour gas for enhanced oil recovery
Bongartz, Dominik
Oxy-fuel combustion of sour gas, a mixture of natural gas (primarily methane (CH 4 )), carbon dioxide (CO 2 ), and hydrogen sulfide (H 2 S), could enable the utilization of large natural gas resources, especially when ...
The impact of chlorine disinfection on biochemical oxygen demand levels in chemically enhanced primary treatment effluent.
Dai, Ji; Jiang, Feng; Shang, Chii; Chau, Kwok-ming; Tse, Yuet-kar; Lee, Chi-fai; Chen, Guang-Hao; Fang, Jingyun; Zhai, Liming
The response trends of biochemical oxygen demand (BOD) and organic strength after the chlorination/dechlorination process were explored through a 2-year, 5-month chemically enhanced primary treatment (CEPT) effluent onsite monitoring program and a 2-month laboratory-scale study. The monitoring results showed that better instantaneous mixing at the chlorine injection point reduced the effect of chlorination/dechlorination on the 5-day BOD levels. The laboratory study results demonstrated that chlorination did not change the particle size distribution, dissolved organic carbon, or chemical oxygen demand of the organic content of the effluent. Nevertheless, chlorination/dechlorination strongly affected the BOD measurement when nitrification was inhibited by changing bioactivity/biodegradation rates. PMID:23863431
Overhauser enhanced magnetic resonance imaging for tumor oximetry: Coregistration of tumor anatomy and tissue oxygen concentration
Krishna, Murali C.; English, Sean; Yamada, Kenichi; Yoo, John; Murugesan, Ramachandran; Devasahayam, Nallathamby; Cook, John A.; Golman, Klaes; Ardenkjaer-Larsen, Jan Henrik; Subramanian, Sankaran; Mitchell, James B.
An efficient noninvasive method for in vivo imaging of tumor oxygenation by using a low-field magnetic resonance scanner and a paramagnetic contrast agent is described. The methodology is based on Overhauser enhanced magnetic resonance imaging (OMRI), a functional imaging technique. OMRI experiments were performed on tumor-bearing mice (squamous cell carcinoma) by i.v. administration of the contrast agent Oxo63 (a highly derivatized triarylmethyl radical) at nontoxic doses in the range of 2ľ7 mmol/kg either as a bolus or as a continuous infusion. Spatially resolved pO2 (oxygen concentration) images from OMRI experiments of tumor-bearing mice exhibited heterogeneous oxygenation profiles and revealed regions of hypoxia in tumors (<10 mmHg; 1 mmHg = 133 Pa). Oxygenation of tumors was enhanced on carbogen (95% O2/5% CO2) inhalation. The pO2 measurements from OMRI were found to be in agreement with those obtained by independent polarographic measurements using a pO2 Eppendorf electrode. This work illustrates that anatomically coregistered pO2 maps of tumors can be readily obtained by combining the good anatomical resolution of water proton-based MRI, and the superior pO2 sensitivity of EPR. OMRI affords the opportunity to perform noninvasive and repeated pO2 measurements of the same animal with useful spatial (?1 mm) and temporal (2 min) resolution, making this method a powerful imaging modality for small animal research to understand tumor physiology and potentially for human applications. PMID:11854518
Quantifying NOx for industrial combustion processes.
Baukal, C E; Eleazer, P B
The objectives of this paper are to (1) identify the problems with many of the units that are used to report and regulate NOx, (2) show how to properly correct NOx measurements for oxygen-enhanced combustion, and (3) recommend a preferred type of NOx unit. The current variety of NOx units make comparisons difficult and can cause considerable confusion. NOx may be measured on a wet or dry basis, but it is commonly reported on a dry basis. The reported NOx may differ from the actual measurements, which may be converted to a specific O2 basis level. Nearly all of the measured NOx from industrial combustion systems is in the form of NO, which is converted to NO2 in the atmosphere. However, when given on a mass basis, the measured NO is commonly reported as NO2 for regulatory purposes, but may be reported as NO, NO2, or simply NOx in technical papers. Some existing regulations may penalize combustion technologies with higher efficiencies and lower flue gas volumes, such as oxygen-enhanced combustion. Confusion may occur when applying some of the "conventional" NOx units to oxygen-enhanced processes. A better unit is the mass of NOx generated per unit of production, which also incorporates the overall process efficiency into the emissions. That unit does not penalize more efficient processes that may generate more NOx on a volume basis, but less NOx on a production basis. PMID:15655998
Oxygen and relative humidity monitoring with films tailored for enhanced photoluminescence.
Cui, Weipan; Liu, Rui; Manna, Eeshita; Park, Joong-Mok; Fungura, Fadzai; Shinar, Joseph; Shinar, Ruth
Approaches to generate porous or doped sensing films, which significantly enhance the photoluminescence (PL) of oxygen optical sensors, and thus improve the signal-to-noise (S/N) ratio, are presented. Tailored films, which enable monitoring the relative humidity (RH) as well, are also presented. Effective porous structures, in which the O2-sensitive dye Pt octaethylporphyrin (PtOEP) or the Pd analog PdOEP was embedded, were realized by first generating blend films of polyethylene glycol (PEG) with polystyrene (PS) or with ethyl cellulose (EC), and then immersing the dried films in water to remove the water-soluble PEG. This approach creates pores (voids) in the sensing films. The dielectric contrast between the films' constituents and the voids increases photon scattering, which in turn increases the optical path of the excitation light within the film, and hence light absorption by the dye, and its PL. Optimized sensing films with a PEG:PS ratio of 1:4 (PEG's molecular weight Mw ?8000) led to ?4.4Î enhancement in the PL (in comparison to PS films). Lower Mw ?200 PEG with a PEG:EC ratio of 1:1 led to a PL enhancement of ?4.7Î. Film-dependent PL enhancements were observed at all oxygen concentrations. The strong PL enhancement enables (i) using lower dye (luminophore) concentrations, (ii) reducing power consumption and enhancing the sensor's operational lifetime when using organic light emitting diodes (OLEDs) as excitation sources, (iii) improving performance when using compact photodetectors with no internal gain, and (iv) reliably extending the dynamic range. The effect of RH on O2 sensing is also presented. Dye:EC films are sensitive to the RH, as shown by the change of the dye's PL decay time with RH at a given O2 concentration. Surprisingly, this RH sensitivity vanishes by adding PEG to EC, including by washing PEG off. In contrast, doping EC with TiO2 nanoparticles maintains the RH effect with the advantage of significant PL enhancement. This enhancement enables differentiation of <10% changes in the RH, which is unattained with the dye:EC sensing films. The results are discussed in terms of the composition, thickness, and microstructure, whether porous or nanoparticle doped, of the composite films. PMID:25467504
Two-Photon Antenna-Core Oxygen Probe with Enhanced Performance
Recent development of two-photon phosphorescence lifetime microscopy (2PLM) of oxygen enabled first noninvasive high-resolution measurements of tissue oxygenation in vivo in 3D, providing valuable physiological information. The so far developed two-photon-enhanced phosphorescent probes comprise antenna-core constructs, in which two-photon absorbing chromophores (antenna) capture and channel excitation energy to a phosphorescent core (metalloporphyrin) via intramolecular excitation energy transfer (EET). These probes allowed demonstration of the methodsĺ potential; however, they suffer from a number of limitations, such as partial loss of emissivity to competing triplet state deactivation pathways (e.g., electron transfer) and suboptimal sensitivity to oxygen, thereby limiting spatial and temporal resolution of the method. Here we present a new probe, PtTCHP-C307, designed to overcome these limitations. The key improvements include significant increase in the phosphorescence quantum yield, higher efficiency of the antenna-core energy transfer, minimized quenching of the phosphorescence by electron transfer and increased signal dynamic range. For the same excitation flux, the new probe is able to produce up to 6-fold higher signal output than previously reported molecules. Performance of PtTCHP-C307 was demonstrated in vivo in pO2 measurements through the intact mouse skull into the bone marrow, where all blood cells are made from hematopoietic stem cells. PMID:24848643
Characterization of mercury-enriched coal combustion residues from electric utilities using enhanced sorbents for mercury control
Sanchez, F.; Keeney, R.; Kosson, D.; Delapp, R. [Vanderbilt University, Nashville, TN (United States). Dept. of Civil and Environmental Engineering
This report evaluates changes that may occur to coal-fired power plant air pollution control residues from the use of activated carbon and other enhanced sorbents for reducing air emissions of mercury and evaluates the potential for captured pollutants leaching during the disposal or use of these residues. Leaching of mercury, arsenic, and selenium during land disposal or beneficial use of coal combustion residues (CCRs) is the environmental impact pathway evaluated in this report. Coal combustion residues refer collectively to fly ash and other air pollution control solid residues generated during the combustion of coal collected through the associated air pollution control system. This research is part of an on-going effort by US Environmental protection Agency (EPA) to use a holistic approach to account for the fate of mercury and other metals in coal throughout the life-cycle stages of CCR management. This report focuses on facilities that use injected sorbents for mercury control. It includes four facilities with activated carbon injection (ACI) and two facilities using brominated ACI. Fly ash has been obtained from each facility with and without operation of the sorbent injection technology for mercury control. Each fly ash sampled was evaluated in the laboratory for leaching as a function of pH and liquid-to-solid ratio. Mercury, arsenic and selenium were the primary constituent of interest; results for these elements are presented here. 30 refs., 30 figs., 14 tabs., 10 apps.
Enhancing effect of oxygen radical scavengers on murine macrophage anticryptococcal activity through production of nitric oxide
We examined the roles of reactive nitrogen intermediates (RNI) and reactive oxygen intermediates (ROI) in interferon-gamma (IFN-?)-induced cryptococcostatic activity of murine peritoneal macrophages using NG-monomethyl-L-arginine (L-NMMA), a competitive inhibitor of RNI synthesis, and superoxide dismutase (SOD) and catalase, oxygen radical scavengers. IFN-?-activated macrophages produced nitric oxide (NO) in a dose-dependent manner, as measured by increased nitrite concentration in the culture supernatant. IFN-? also enhanced the suppressive effect on cryptococcal growth in a similar dose-dependent manner. The induction of killing activity and NO production by an optimal dose of IFN-? (100 U/ml) was virtually suppressed by 500 ?M L-NMMA. These results confirmed the importance of the RNI-mediated effector mechanism in anticryptococcal activity of macrophages. SOD and catalase significantly enhanced the cryptococcostatic activity of macrophages induced by a suboptimal dose of IFN-? (20 U/ml). The augmenting effect of these reagents was mediated by NO, since they potentiated the production of NO by macrophages and their effects were totally blocked by L-NMMA. Our results indicate that the IFN-?-induced anticryptococcal activity of macrophages is dependent mostly on RNI, and suggest that the ROI system down-regulates the effector mechanism for cryptococcostasis by suppressing the RNI system. PMID:8608643
Palladiumľplatinum core-shell icosahedra with substantially enhanced activity and durability towards oxygen reduction
Wang, Xue; Choi, Sang-Il; Roling, Luke T.; Luo, Ming; Ma, Cheng; Zhang, Lei; Chi, Miaofang; Liu, Jingyue; Xie, Zhaoxiong; Herron, Jeffrey A.; Mavrikakis, Manos; Xia, Younan
Conformal deposition of platinum as ultrathin shells on facet-controlled palladium nanocrystals offers a great opportunity to enhance the catalytic performance while reducing its loading. Here we report such a system based on palladium icosahedra. Owing to lateral confinement imposed by twin boundaries and thus vertical relaxation only, the platinum overlayers evolve into a corrugated structure under compressive strain. For the core-shell nanocrystals with an average of 2.7 platinum overlayers, their specific and platinum mass activities towards oxygen reduction are enhanced by eight- and sevenfold, respectively, relative to a commercial catalyst. Density functional theory calculations indicate that the enhancement can be attributed to the weakened binding of hydroxyl to the compressed platinum surface supported on palladium. After 10,000 testing cycles, the mass activity of the core-shell nanocrystals is still four times higher than the commercial catalyst. These results demonstrate an effective approach to the development of electrocatalysts with greatly enhanced activity and durability. PMID:26133469
Palladium-platinum core-shell icosahedra with substantially enhanced activity and durability towards oxygen reduction.
Wang, Xue; Choi, Sang-Il; Roling, Luke T; Luo, Ming; Ma, Cheng; Zhang, Lei; Chi, Miaofang; Liu, Jingyue; Xie, Zhaoxiong; Herron, Jeffrey A; Mavrikakis, Manos; Xia, Younan
Conformal deposition of platinum as ultrathin shells on facet-controlled palladium nanocrystals offers a great opportunity to enhance the catalytic performance while reducing its loading. Here we report such a system based on palladium icosahedra. Owing to lateral confinement imposed by twin boundaries and thus vertical relaxation only, the platinum overlayers evolve into a corrugated structure under compressive strain. For the core-shell nanocrystals with an average of 2.7 platinum overlayers, their specific and platinum mass activities towards oxygen reduction are enhanced by eight- and sevenfold, respectively, relative to a commercial catalyst. Density functional theory calculations indicate that the enhancement can be attributed to the weakened binding of hydroxyl to the compressed platinum surface supported on palladium. After 10,000 testing cycles, the mass activity of the core-shell nanocrystals is still four times higher than the commercial catalyst. These results demonstrate an effective approach to the development of electrocatalysts with greatly enhanced activity and durability. PMID:26133469
Enhanced proliferation and dopaminergic differentiation of ventral mesencephalic precursor cells by synergistic effect of FGF2 and reduced oxygen tension
Jensen, Pia [Department of Neurobiology Research, Institute of Molecular Medicine, University of Southern Denmark, Winslowparken 21, DK-5000 Odense C (Denmark) [Department of Neurobiology Research, Institute of Molecular Medicine, University of Southern Denmark, Winslowparken 21, DK-5000 Odense C (Denmark); Department of Neurosurgery, University of Bern, CH-3010 Bern (Switzerland); Gramsbergen, Jan-Bert; Zimmer, Jens [Department of Neurobiology Research, Institute of Molecular Medicine, University of Southern Denmark, Winslowparken 21, DK-5000 Odense C (Denmark)] [Department of Neurobiology Research, Institute of Molecular Medicine, University of Southern Denmark, Winslowparken 21, DK-5000 Odense C (Denmark); Widmer, Hans R. [Department of Neurosurgery, University of Bern, CH-3010 Bern (Switzerland)] [Department of Neurosurgery, University of Bern, CH-3010 Bern (Switzerland); Meyer, Morten, E-mail: email@example.com [Department of Neurobiology Research, Institute of Molecular Medicine, University of Southern Denmark, Winslowparken 21, DK-5000 Odense C (Denmark)] [Department of Neurobiology Research, Institute of Molecular Medicine, University of Southern Denmark, Winslowparken 21, DK-5000 Odense C (Denmark)
Effective numerical expansion of dopaminergic precursors might overcome the limited availability of transplantable cells in replacement strategies for Parkinson's disease. Here we investigated the effect of fibroblast growth factor-2 (FGF2) and FGF8 on expansion and dopaminergic differentiation of rat embryonic ventral mesencephalic neuroblasts cultured at high (20%) and low (3%) oxygen tension. More cells incorporated bromodeoxyuridine in cultures expanded at low as compared to high oxygen tension, and after 6 days of differentiation there were significantly more neuronal cells in low than in high oxygen cultures. Low oxygen during FGF2-mediated expansion resulted also in a significant increase in tyrosine hydroxylase-immunoreactive (TH-ir) dopaminergic neurons as compared to high oxygen tension, but no corresponding effect was observed for dopamine release into the culture medium. However, switching FGF2-expanded cultures from low to high oxygen tension during the last two days of differentiation significantly enhanced dopamine release and intracellular dopamine levels as compared to all other treatment groups. In addition, the short-term exposure to high oxygen enhanced in situ assessed TH enzyme activity, which may explain the elevated dopamine levels. Our findings demonstrate that modulation of oxygen tension is a recognizable factor for in vitro expansion and dopaminergic differentiation of rat embryonic midbrain precursor cells.
Upgrading and enhanced recovery of Jobo heavy oil using hydrogen donor under in-situ combustioná
Huseynzade, Samir
In-situ upgrading of oil using hydrogen donors is a new process. In particular, very little research has been conducted with respect to in-situ oil upgrading using hydrogen donor under in-situ combustion. Several papers describe the use of metal...
Upgrading and enhanced recovery of Jobo heavy oil using hydrogen donor under in-situ combustioná
Huseynzade, Samir
In-situ upgrading of oil using hydrogen donors is a new process. In particular, very little research has been conducted with respect to in-situ oil upgrading using hydrogen donor under in-situ combustion. Several papers describe the use of metal...
Plasma-Enhanced Combustion of Hydrocarbon Fuels and Fuel Blends Using Nanosecond Pulsed Discharges
Cappelli, Mark; Mungal, M Godfrey
This project had as its goals the study of fundamental physical and chemical processes relevant to the sustained premixed and non-premixed jet ignition/combustion of low grade fuels or fuels under adverse flow conditions using non-equilibrium pulsed nanosecond discharges.
Experimental and Modeling Studies of the Characteristics of Liquid Biofuels for Enhanced Combustion
E. Meeks; A. U. Modak; C.V. Naik; K. V. Puduppakkam; C. Westbrook; F. N. Egolfopoulos; T. Tsotsis; S. H. Roby
The objectives of this project have been to develop a comprehensive set of fundamental data regarding the combustion behavior of biodiesel fuels and appropriately associated model fuels that may represent biodiesels in automotive engineering simulation. Based on the fundamental study results, an auxiliary objective was to identify differentiating characteristics of molecular fuel components that can be used to explain different fuel behavior and that may ultimately be used in the planning and design of optimal fuel-production processes. The fuels studied in this project were BQ-9000 certified biodiesel fuels that are certified for use in automotive engine applications. Prior to this project, there were no systematic experimental flame data available for such fuels. One of the key goals has been to generate such data, and to use this data in developing and verifying effective kinetic models. The models have then been reduced through automated means to enable multi-dimensional simulation of the combustion characteristics of such fuels in reciprocating engines. Such reliable kinetics models, validated against fundamental data derived from laminar flames using idealized flow models, are key to the development and design of optimal engines, engine operation and fuels. The models provide direct information about the relative contribution of different molecular constituents to the fuel performance and can be used to assess both combustion and emissions characteristics. During this project, we completed a major and thorough validation of a set of biodiesel surrogate components, allowing us to begin to evaluate the fundamental combustion characteristics for B100 fuels.
Reduction kinetics of Cu-, Ni-, and Fe-based oxygen carriers using syngas (CO + H{sub 2}) for chemical-looping combustion
Alberto Abad; Francisco Garcia-Labiano; Luis F. de Diego; Pilar Gayn; Juan Adnez [Instituto de Carboquimica (CSIC), Zaragoza (Spain). Department of Energy and Environment
The reactivity of three Cu-, Fe-, and Ni-based oxygen carriers to be used in a chemical-looping combustion (CLC) system using syngas as fuel has been analyzed. The oxygen carriers exhibited high reactivity during reduction with fuel gases present in syngas (H{sub 2} and CO), with average values in the range 8-30% min{sup -1}. No effect of the gas products (H{sub 2}O, CO{sub 2}) on the reduction reaction rate was detected. The kinetic parameters of reaction with H{sub 2} and CO have been determined by thermogravimetric analysis. The grain model with spherical or platelike geometry in the grain was used for the kinetic determination, in which the chemical reaction controlled the global reaction rate. The activation energies determined for these reactions were low, with values ranging from 14 to 33 kJ mol{sup -1}. The reaction order depended on the reacting gas, and values from 0.5 to 1 were found. Moreover, the reactivity of the oxygen carriers when both H{sub 2} and CO are simultaneously present in the reacting gases has been analyzed, both at atmospheric and pressurized conditions. For the Cu- and Fe-based oxygen carriers, the reaction rate of the oxygen carrier with syngas corresponded to the addition of the reaction rates for the individual fuel gases, H{sub 2} and CO. For the Ni-based oxygen carrier, the reaction rate was that corresponding to the fuel gas that reacted faster with the oxygen carrier at the reacting conditions (fuel concentration, temperature, and pressure). The consequences of the behavior of the reaction of syngas and the water-gas shift (WGS) equilibrium on the design of the fuel reactor of a CLC system have been analyzed. A preliminary estimation of the solids inventory for the use of syngas in the fuel reactor of a CLC system gave values in the range of 19-34 kg MW{sup -1} when the WGS equilibrium was considered to be instantaneous. 8 figs., 4 tabs.
Carbon deposition model for oxygen-hydrocarbon combustion. Task 6: Data analysis and formulation of an empirical model. Final report, April 1989-May 1990
Makel, D.B.; Rosenberg, S.D.
The formation and deposition of carbon (soot) was studied in the Carbon Deposition Model for Oxygen-Hydrocarbon Combustion Program. An empirical, 1-D model for predicting soot formation and deposition in LO2/hydrocarbon gas generators/preburners was derived. The experimental data required to anchor the model were identified and a test program to obtain the data was defined. In support of the model development, cold flow mixing experiments using a high injection density injector were performed. The purpose of this investigation was to advance the state-of-the-art in LO2/hydrocarbon gas generator design by developing a reliable engineering model of gas generator operation. The model was formulated to account for the influences of fluid dynamics, chemical kinetics, and gas generator hardware design on soot formation and deposition.
Reversed flow fluidized-bed combustion apparatus
Shang, Jer-Yu (Fairfax, VA); Mei, Joseph S. (Morgantown, WV); Wilson, John S. (Morgantown, WV)
The present invention is directed to a fluidized-bed combustion apparatus provided with a U-shaped combustion zone. A cyclone is disposed in the combustion zone for recycling solid particulate material. The combustion zone configuration and the recycling feature provide relatively long residence times and low freeboard heights to maximize combustion of combustible material, reduce nitrogen oxides, and enhance sulfur oxide reduction.
Catalytic Activity Enhancement for Oxygen Reduction on Epitaxial Perovskite Thin Films for Solid-Oxide Fuel Cells
La O', Gerardo Jose [Massachusetts Institute of Technology (MIT); Ahn, Sung Jin [Massachusetts Institute of Technology (MIT); Crumlin, Ethan [Massachusetts Institute of Technology (MIT); Orikasa, Yuki [Massachusetts Institute of Technology (MIT); Biegalski, Michael D [ORNL; Christen, Hans M [ORNL; Shao-Horn, Yang [Massachusetts Institute of Technology (MIT)
The active ingredient: La{sub 0.8}Sr{sub 0.2}CoO{sub 3-{delta}} (LSC) epitaxial thin films are prepared on (001)-oriented yttria-stabilized zirconia (YSZ) single crystals with a gadolinium-doped ceria (GDC) buffer layer. The LSC epitaxial films exhibit better oxygen reduction kinetics than bulk LSC. The enhanced activity is attributed in part to higher oxygen nonstoichiometry.
Role of Metal Coordination Structures in Enhancement of Electrocatalytic Activity of Ternary Nanoalloys for Oxygen Reduction Reaction
Wanjala, Bridgid N.; Fang, Bin; Loukrakpam, Rameshwori; Chen, Yongsheng; Engelhard, Mark H.; Luo, Jin; Yin, Jun; Yang, Lefu; Shan, Shiyao; Zhong, Chuan-Jian
The ability to harness the metal-metal and metal-oxygen coordination structures of nanoalloy catalysts is critical for catalyzing the oxygen reduction reaction because such a detailed atomic-scale structure dictates the surface binding site and strength for molecular oxygen and oxygenated intermediate species in the electrocatalytic process. This report describes the results of an investigation of the metal-metal and metal-oxygen coordination structures of ternary nanoalloys and their manipulation to enhance the electrocatalytic activity for oxygen reduction reaction. The basic hypothesis is that such atomic-scale structure can be manipulated by oxidative-reductive thermal treatment to influence the binding site and strength of molecular oxygen and oxygenated species on the nanoalloy surface. The results have revealed remarkable increases in both mass activity and specific activity for the catalysts processed by the oxidative-reductive treatment over those treated under non-reactive or low-degree oxidative atmospheres before the reductive treatment. In comparison with non-reactive-reductive treatment, an increased degree of heteroatomic alloying among the three metal components in the ternary catalysts and a decreased percentage of oxides (NiO and CoO) have been revealed by X-ray absorption fine structure spectroscopy for the catalysts treated by the oxidative-reductive treatment. An enrichment of surface Pt has also been detected by x-ray photoelectron spectroscopy for such catalysts. A combination of the increase in the heteroatomic alloying, the decrease in metal oxides, and the enrichment of surface Pt by the oxidative-reductive thermal treatment has therefore been concluded to be responsible for the enhanced electrocatalytic activity. The demonstration of this new approach to manipulating the metal-metal and metal-oxygen coordination structures forms the basis for an effective strategy in engineering ternary nanoalloy catalysts, and has provided new insights into the role of such structures in the enhancement of the electrocatalytic activity.
Oxygen Reduction Kinetics Enhancement on a 2 Heterostructured Oxide Surface for Solid Oxide Fuel Cells
Crumlin, Ethan [Massachusetts Institute of Technology (MIT); Mutoro, Eva [ORNL; Ahn, Sung Jin [Massachusetts Institute of Technology (MIT); Jose la O', Gerardo [Massachusetts Institute of Technology (MIT); Leonard, Donovan N [ORNL; Borisevich, Albina Y [ORNL; Biegalski, Michael D [ORNL; Christen, Hans M [ORNL; Shao-Horn, Yang [Massachusetts Institute of Technology (MIT)
Heterostructured interfaces of oxides, which can exhibit transport and reactivity characteristics remarkably different from those of bulk oxides, are interesting systems to explore in search of highly active cathodes for the oxygen reduction reaction (ORR). Here, we show that the ORR of {approx}85 nm thick La{sub 0.8}Sr{sub 0.2}CoO{sub 3-{delta}} (LSC{sub 113}) films prepared by pulsed laser deposition on (001)-oriented yttria-stabilized zirconia (YSZ) substrates is dramatically enhanced ({approx} 3-4 orders of magnitude above bulk LSC{sub 113}) by surface decorations of (La{sub 0.5}Sr{sub 0.5}){sub 2}CoO{sub 4{+-}{delta}} (LSC{sub 214}) with coverage in the range from {approx}0.1 to {approx}15 nm. Their surface and atomic structures were characterized by atomic force, scanning electron, and scanning transmission electron microscopy, and the ORR kinetics were determined by electrochemical impedance spectroscopy. Although the mechanism for ORR enhancement is not yet fully understood, our results to date show that the observed ORR enhancement can be attributed to highly active interfacial LSC{sub 113}/LSC{sub 214} regions, which were shown to be atomically sharp.
Utilization of spent activated carbon to enhance the combustion efficiency of organic sludge derived fuel.
Chen, Wei-Sheng; Lin, Chang-Wen; Chang, Fang-Chih; Lee, Wen-Jhy; Wu, Jhong-Lin
This study examines the heating value and combustion efficiency of organic sludge derived fuel, spent activated carbon derived fuel, and derived fuel from a mixture of organic sludge and spent activated carbon. Spent activated carbon was sampled from an air pollution control device of an incinerator and characterized by XRD, XRF, TG/DTA, and SEM. The spent activated carbon was washed with deionized water and solvent (1N sulfuric acid) and then processed by the organic sludge derived fuel manufacturing process. After washing, the salt (chloride) and sulfide content could be reduced to 99% and 97%, respectively; in addition the carbon content and heating value were increased. Different ratios of spent activated carbon have been applied to the organic sludge derived fuel to reduce the NO(x) emission of the combustion. PMID:22209404
Enhanced oxygen reduction activity and solid oxide fuel cell performance with a nanoparticles-loaded cathode.
Zhang, Xiaomin; Liu, Li; Zhao, Zhe; Tu, Baofeng; Ou, Dingrong; Cui, Daan; Wei, Xuming; Chen, Xiaobo; Cheng, Mojie
Reluctant oxygen-reduction-reaction (ORR) activity has been a long-standing challenge limiting cell performance for solid oxide fuel cells (SOFCs) in both centralized and distributed power applications. We report here that this challenge has been tackled with coloading of (La,Sr)MnO3 (LSM) and Y2O3 stabilized zirconia (YSZ) nanoparticles within a porous YSZ framework. This design dramatically improves ORR activity, enhances fuel cell output (200-300% power improvement), and enables superior stability (no observed degradation within 500 h of operation) from 600 to 800 ░C. The improved performance is attributed to the intimate contacts between nanoparticulate YSZ and LSM particles in the three-phase boundaries in the cathode. PMID:25686380
Resistive switching of oxygen enhanced TiO2 thin-film devices
NASA Astrophysics Data System (ADS)
Salaoru, Iulia; Prodromakis, Themistoklis; Khiat, Ali; Toumazou, Christofer
In this work, we investigate the effect of oxygen-enhanced TiO2 thin films on the switching dynamics of Pt/TiO2/Pt memristive nanodevices. We demonstrate that such devices can be used as resistive random access memory (RRAM) cells without required electroforming. We experimentally demonstrate that devices based on TiO2 films fabricated via sputtering with partial pressures of Ar/O2 6/6 sccm and 2/10 sccm show OFF/ON ratios of six and two orders of magnitude, respectively. Additionally, it was found that a lower O2 flow during sputtering of TiO2 allows for lower energy requirements for switching the devices from a high to low resistive state.
Enhancing Electrocatalytic Oxygen Reduction on Nitrogen-Doped Graphene by Active Sites Implantation
NASA Astrophysics Data System (ADS)
Feng, Leiyu; Yang, Lanqin; Huang, Zujing; Luo, Jingyang; Li, Mu; Wang, Dongbo; Chen, Yinguang
The shortage of nitrogen active sites and relatively low nitrogen content result in unsatisfying eletrocatalytic activity and durability of nitrogen-doped graphene (NG) for oxygen reduction reaction (ORR). Here we report a novel approach to substantially enhance electrocatalytic oxygen reduction on NG electrode by the implantation of nitrogen active sites with mesoporous graphitic carbon nitride (mpg-C3N4). Electrochemical characterization revealed that in neutral electrolyte the resulting NG (I-NG) exhibited super electrocatalytic activity (completely 100% of four-electron ORR pathway) and durability (nearly no activity change after 100000 potential cyclings). When I-NG was used as cathode catalyst in microbial fuel cells (MFCs), power density and its drop percentage were also much better than the NG and Pt/C ones, demonstrating that the current I-NG was a perfect alternative to Pt/C and offered a new potential for constructing high-performance and less expensive cathode which is crucial for large-scale application of MFC technology.
Antioxidant Activity of Oxygen Evolving Enhancer Protein 1 Purified from Capsosiphon fulvescens.
Kim, Eun-Young; Choi, Youn Hee; Lee, Jung Im; Kim, In-Hye; Nam, Taek-Jeong
This study was conducted to determine the antioxidant activity of a protein purified from Capsosiphon fulvescens. The purification steps included sodium acetate (pH 6) extraction and diethylaminoethyl-cellulose, reversed phase Shodex C4P-50 column chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis indicated that the molecular weight of the purified protein was 33 kDa. The N-terminus and partial peptide amino acid sequence of this protein was identical to the sequence of oxygen evolving enhancer (OEE) 1 protein. The antioxidant activity of the OEE 1 was determined in vitro using a scavenging test with 4 types of reactive oxygen species (ROS), including the 2,2-diphenyl-1-picrylhydrazyl radical, hydroxyl radical, superoxide anion, and hydrogen peroxide (H2 O2 ). OEE 1 had higher H2 O2 scavenging activity, which proved to be the result of enzymatic antioxidants rather than nonenzymatic antioxidants. In addition, OEE 1 showed less H2 O2 -mediated ROS formation in HepG2 cells. In conclusion, this study demonstrates that OEE 1 purified from C. fulvescens is an excellent antioxidant. PMID:25944160
Atomic Ordering Enhanced Electrocatalytic Activity of Nanoalloys for Oxygen Reduction Reaction
Loukrakpam, Rameshwori; Shan, Shiyao; Petkov, Valeri; Yang, Lefu; Luo, Jin; Zhong, Chuan-Jian
For oxygen reduction reaction (ORR) over alloy electrocatalysts, the understanding of how the atomic arrangement of the metal species in the nanocatalysts is responsible for the catalytic enhancement is challenging for achieving better design and tailoring of nanoalloy catalysts. This paper reports results of an investigation of the atomic structures and the electrocatalytic activities of ternary and binary nanoalloys, aiming at revealing a fundamental insight into the unique atomic-scale structure?electrocatalytic activity relationship. PtIrCo catalyst and its binary counterparts (PtCo and PtIr) are chosen as a model system for this study. The effect of thermochemical treatment temperature on the atomic-scale structure of the catalysts was examined as a useful probe to the structure?activity correlation. The structural characterization of the binary and ternary nanoalloy catalysts was performed by combining surface sensitive techniques such as XPS and 3D atomic ordering sensitive techniques such as high-energy X-ray diffraction (HE-XRD) coupled to atomic pair distribution function (PDF) analysis (HE-XRD/PDFs) and computer simulations. The results show that the thermal treatment temperature tunes the nanoalloyĺs atomic and chemical ordering in a different way depending on the chemical composition, leading to differences in the nanoalloyĺs mass and specific activities. A unique structural tunability of the atomic ordering in a platinum?iridium?cobalt nanoalloy has been revealed for enhancing greatly the electrocatalytic activity toward oxygen reduction reaction, which has significant implication for rational design and nanoengineering of advanced catalysts for electrochemical energy conversion and storage.
Experimental and analytical study to model temperature profiles and stoichiometry in oxygen-enriched in-situ combustion
Rodriguez, Jose Ramon
in Venezuela. These runs were carried out with air containing three values of oxygen concentration, 21%, 30%, and 40%. The weight percentage of sand, clay, water, and oil in the sand mix was kept constant in all runs at 86.6%, 4.7%, 4.0%, and 4.7% respectively...
IGF-I enhances cellular senescence via the reactive oxygen species-p53 pathway
Handayaningsih, Anastasia-Evi; Takahashi, Michiko; Fukuoka, Hidenori; Iguchi, Genzo; Nishizawa, Hitoshi; Yamamoto, Masaaki; Suda, Kentaro [Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe (Japan)] [Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe (Japan); Takahashi, Yutaka, E-mail: email@example.com [Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe (Japan)] [Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe (Japan)
Highlights: Black-Right-Pointing-Pointer Cellular senescence plays an important role in tumorigenesis and aging process. Black-Right-Pointing-Pointer We demonstrated IGF-I enhanced cellular senescence in primary confluent cells. Black-Right-Pointing-Pointer IGF-I enhanced cellular senescence in the ROS and p53-dependent manner. Black-Right-Pointing-Pointer These results may explain the underlying mechanisms of IGF-I involvement in tumorigenesis and in regulation of aging. -- Abstract: Cellular senescence is characterized by growth arrest, enlarged and flattened cell morphology, the expression of senescence-associated {beta}-galactosidase (SA-{beta}-gal), and by activation of tumor suppressor networks. Insulin-like growth factor-I (IGF-I) plays a critical role in cellular growth, proliferation, tumorigenesis, and regulation of aging. In the present study, we show that IGF-I enhances cellular senescence in mouse, rat, and human primary cells in the confluent state. IGF-I induced expression of a DNA damage marker, {gamma}H2AX, the increased levels of p53 and p21 proteins, and activated SA-{beta}-gal. In the confluent state, an altered downstream signaling of IGF-I receptor was observed. Treatment with a reactive oxygen species (ROS) scavenger, N-acetylcystein (NAC) significantly suppressed induction of these markers, indicating that ROS are involved in the induction of cellular senescence by IGF-I. In p53-null mouse embryonic fibroblasts, the IGF-I-induced augmentation of SA-{beta}-gal and p21 was inhibited, demonstrating that p53 is required for cellular senescence induced by IGF-I. Thus, these data reveal a novel pathway whereby IGF-I enhances cellular senescence in the ROS and p53-dependent manner and may explain the underlying mechanisms of IGF-I involvement in tumorigenesis and in regulation of aging.
Warm Oxygen Enhancements in the Inner Magnetosphere and Their Relation to Geomagnetic Activity, Plasmasphere, and Ring Current.
NASA Astrophysics Data System (ADS)
Jahn, J. M.; Skoug, R. M.; Gkioulidou, M.; Bonnell, J. W.; Larsen, B.; Reeves, G. D.; Spence, H. E.
Ionospheric oxygen plays an important role in the dynamics of Earth's magnetosphere. During geomagnetic storms, oxygen transported into the tail can experience significant energization and become a major contributor to the storm-time ring current. At very low energies, a dense cold oxygen torus straddles the outer plasmasphere, frequently with O+/H+ ratios approaching unity. With the Radiation Belt Storm Probes we now also observe a third oxygen population in this region. In this paper we discuss the nature of "warm" (10's eV to few keV, i.e., between plasmasphere and ring current ion energies) oxygen density enhancements over the course of the Van Allen Probes mission. We find that the composition of this warm thermal plasma is very dynamic throughout the inner magnetosphere. The warm oxygen density is highly responsive to changes in geomagnetic activity, varying by more than two orders of magnitude between quiet times and moderate storms. This variation at times is a greater than the variation of the corresponding proton density. The O+/H+ warm plasma density ration will frequently exceed unity, usually during the recovery phase of storms. The region of enhanced warm oxygen density reaches from the plasmasphere boundary out to at least geosynchronous orbit (the largest L-shells covered by the Van Allen Probes). It can be observed at all local times. Barring other geomagnetic activity, warm oxygen density enhancements disappear typically within 5 days of their first detection, which is consistent with drift times through the inner magnetosphere along open drift paths. We are putting these characteristics in context of the composition, location, and evolution of the plasmasphere and the ring current.
Multicolor tunability and upconversion enhancement of fluoride nanoparticles by oxygen dopant
NASA Astrophysics Data System (ADS)
Niu, Wenbin; Wu, Suli; Zhang, Shufen; Su, Liap Tat; Tok, Alfred Iing Yoong
The ability to manipulate the upconversion luminescence of lanthanide-ion doped fluoride upconversion nanoparticles (UCNPs) is particularly important and highly desired due to their wide applications in color displays, multiplexing bioassays and multicolor imaging. Here, we developed a strategy for simultaneously tuning color output and enhancing upconversion emission of Yb/Er doped fluoride UCNPs, based on adjusting the oxygen doping level. The synthesis of multicolored multifunctional NaGdF4:Yb,Er UCNPs was used as the model host system to demonstrate this protocol. Ammonium nitrate (NH4NO3) was used as the oxygen source and added into the reaction system at the beginning stage of nucleation and growth process of fluoride UCNPs, which facilitates the formation of enough oxygen atoms and the diffusion of these into the fluoride host matrix. The results revealed that multicolour output and upconversion enhancement mainly resulted from the variation of phonon energy and crystal field symmetry of the host lattice, respectively. This strategy can be further expanded to other fluoride host matrices. As an example of an application, multicolored UCNPs were used as a color converter in light emitting diodes, which can effectively convert near-infrared light into visible light. It is expected that these multicolored UCNPs will be promising for applications in multiplexing biodetection, bioimaging (optical and magnetic resonance imaging) and other optical technologies, and the present method for the control of O2- doping may also be used in other functional nanomaterials.The ability to manipulate the upconversion luminescence of lanthanide-ion doped fluoride upconversion nanoparticles (UCNPs) is particularly important and highly desired due to their wide applications in color displays, multiplexing bioassays and multicolor imaging. Here, we developed a strategy for simultaneously tuning color output and enhancing upconversion emission of Yb/Er doped fluoride UCNPs, based on adjusting the oxygen doping level. The synthesis of multicolored multifunctional NaGdF4:Yb,Er UCNPs was used as the model host system to demonstrate this protocol. Ammonium nitrate (NH4NO3) was used as the oxygen source and added into the reaction system at the beginning stage of nucleation and growth process of fluoride UCNPs, which facilitates the formation of enough oxygen atoms and the diffusion of these into the fluoride host matrix. The results revealed that multicolour output and upconversion enhancement mainly resulted from the variation of phonon energy and crystal field symmetry of the host lattice, respectively. This strategy can be further expanded to other fluoride host matrices. As an example of an application, multicolored UCNPs were used as a color converter in light emitting diodes, which can effectively convert near-infrared light into visible light. It is expected that these multicolored UCNPs will be promising for applications in multiplexing biodetection, bioimaging (optical and magnetic resonance imaging) and other optical technologies, and the present method for the control of O2- doping may also be used in other functional nanomaterials. Electronic supplementary information (ESI) available: Upconversion spectra of NaYF4:Yb,Er UCNPs prepared with various oxygen sources (trimethylamine N-oxide and ammonium carbonate, Fig. S1) and different addition temperatures of NH4NO3 (Fig. S2), enlarged XRD patterns (Fig. S3), the intensity ratios of green to red emissions of NaGdF4:Yb,Er UCNPs prepared with various amounts of NH4NO3 (Fig. S4), power dependence of upconversion spectra of NaGdF4:Yb,Er UCNPs prepared at 300 ░C for 1 h (Fig. S5), upconversion spectra of the product after further reaction between as-prepared NaYF4:Yb,Er and 50 mg of NH4NO3 at 300 ░C for 1 h (Fig. S6), XRD patterns of NaYF4:Yb,Er and NaLuF4:Yb,Er UCNPs prepared with various amounts of NH4NO3 (Fig. S7 and S8), the corresponding magnetization curves of NaGdF4:Yb,Er UCNPs (Fig. S9). See DOI: 10.1039/c3nr01612a
Self-assembled nanoporous Pt-based nanowire networks with enhanced oxygen-reduction activity
Galinski, Henning; Lin, Yang; Scherrer, Barbara; Evans, Anna; D÷beli, Max; Gauckler, Ludwig J
The development of "alternative" power sources poses one of the central scientific challenges of this century. The fuel cell is one of the potential alternatives which can be used for various forms of portable power generation. But in order to stand up to batteries, the fuel cell needs to be safe, reliable and economically competitive. Even though the implementation of nano-engineered thin-film electrolytes recently caused a leap in evolution of miniaturised fuel cells, the development of a new generation of electrodes has been less effective. This situation is based on the intricate demand to enhance the oxygen-reduction activity while reducing the cost-intensive Pt content of those electrodes. Despite this central challenge, the integrity of those electrodes has to be conserved over a time span of 10000 hours. Here, we show a solution for both problems, as the nano-porous Pt-based nanowire networks investigated in this contribution guarantee for an enhanced catalytic activity which is up to a factor 13 high...
Research Combustion Lab Facility Capabilities and Throughput Enhanced by New Test Stands
NASA Technical Reports Server (NTRS)
The original test stand location has a small copper rocket engine mounted on the stand. The new stand, located about 4 feet to the left, has a long pulse detonation combustion engine mounted on it. To the rear of the two stands can be seen a bulkhead with feed line outlets that can be switched at common valves behind the bulkhead to supply either stand. A gauge panel is visible through a doorway in the bulkhead at which various purge pressures are set. A connection panel for instrumentation wiring can be seen above the stands.
Visible light-induced singlet oxygen-mediated intracellular disassembly of polymeric micelles co-loaded with a photosensitizer and an anticancer drug for enhanced photodynamic therapy.
Saravanakumar, Gurusamy; Lee, Junseok; Kim, Jihoon; Kim, Won Jong
Herein, we report a biocompatible amphiphilic block copolymer micelle bearing a singlet oxygen-sensitive vinyldithioether cleavable linker at the core-shell junction, which undergoes singlet oxygen-mediated photocleavage in the presence of visible light. The micelle facilitates the light-responsive release of singlet oxygen and an anticancer drug for enhanced photodynamic therapy. PMID:25998105
Oxidation of Glyoxylic Acid by Cerium(IV): Oxygen-Induced Enhancement of the Primary Radical Concentration
Steinbock, Oliver
Oxidation of Glyoxylic Acid by Cerium(IV): Oxygen-Induced Enhancement of the Primary Radical radical formed by abstraction of a hydrogen atom from hydrated glyoxylic acid. The rate constant for the anaerobic self-decay of the radical was measured as approximately 3.7 Î 109 L mol-1 s-1. Surprisingly
Promoted combustion of nine structural metals in high-pressure gaseous oxygen - A comparison of ranking methods
NASA Technical Reports Server (NTRS)
Steinberg, Theodore A.; Rucker, Michelle A.; Beeson, Harold D.
The 316, 321, 440C, and 17-4 PH stainless steels, as well as Inconel 600, Inconel 718, Waspaloy, Monel 400, and Al 2219, have been evaluated for relative nonflammability in a high-pressure oxygen environment with a view to the comparative advantages of four different flammability-ranking methods. The effects of changes in test pressure, sample diameter, promoter type, and sample configuration on ranking method results are evaluated; ranking methods employing velocity as the primary ranking criterion are limited by diameter effects, while those which use extinguishing pressure are nonselective for metals with similar flammabilities.
Enhancement of photosynthetic CO2 assimilation in the absence of oxygen, as dependent upon species and temperature.
Hesketh, J
The assimilation of CO2 was enhanced in seven plant species by 44% at 30░ in the absence of oxygen, and in three of the species by 85% at 40░. Net assimilation of CO2 was not significantly greater in the absence of O2 than it was in air with leaves of three tropical grasses and of one dicotyledonous species, Amaranthus palmeri. For two species in 30░, the enhanced CO2 assimilation values were similar to those of the tropical grasses and of A. palmeri. The absence of O2 did not enhance net CO2 assimilation in maize even in light of low intensity. PMID:24549501
Oxygen-Enhanced Surface Segregation of Mn in Cu-Mn and Ag-Mn Alloy Films Studied by ISS\\/AES
Itsuo Katayama; Kenjiro Oura; Fumiya Shoji; Teruo Hanawa
The influence of oxygen contamination on the surface segregation of simultaneously deposited Cu-Mn and Ag-Mn thin-film alloys has been investigated by a combined use of low-energy ion scattering spectroscopy(ISS) and Auger electron spectroscopy(AES). It has been reported that (1) in both Cu-Mn and Ag-Mn systems, the surface segregation of Mn is enhanced by oxygen adsorption and (2) the oxygen-enhanced segregation
Low oxygen tension enhances the generation of lung progenitor cells from mouse embryonic and induced pluripotent stem cells
Garreta, Elena; Melo, Esther; Navajas, Daniel; FarrÚ, Ramon
Abstract Whole?organ decellularization technology has emerged as a new alternative for the fabrication of bioartificial lungs. Embryonic stem cells (ESC) and induced pluripotent stem cells (iPSC) are potentially useful for recellularization since they can be directed to express phenotypic marker genes of lung epithelial cells. Normal pulmonary development takes place in a low oxygen environment ranging from 1 to 5%. By contrast, in vitro ESC and iPSC differentiation protocols are usually carried out at room?air oxygen tension. Here, we sought to determine the role played by oxygen tension on the derivation of Nkx2.1+ lung/thyroid progenitor cells from mouse ESC and iPSC. A step?wise differentiation protocol was used to generate Nkx2.1+ lung/thyroid progenitors under 20% and 5% oxygen tension. On day 12, gene expression analysis revealed that Nkx2.1 and Foxa2 (endodermal and early lung epithelial cell marker) were significantly upregulated at 5% oxygen tension in ESC and iPSC differentiated cultures compared to 20% oxygen conditions. In addition, quantification of Foxa2+Nkx2.1+Pax8? cells corresponding to the lung field, with exclusion of the potential thyroid fate identified by Pax8 expression, confirmed that the low physiologic oxygen tension exerted a significant positive effect on early pulmonary differentiation of ESC and iPSC. In conclusion, we found that 5% oxygen tension enhanced the derivation of lung progenitors from mouse ESC and iPSC compared to 20% room?air oxygen tension. PMID:25347858
Interagency assessment of oxygenated fuels
Oxygenates have been used as octane enhancers in gasoline since the late 1970s, due to the phaseout of lead. During the 1980s, oxygenates came in to wider use as some States implemented oxygenated gasoline programs for the control of carbon monoxide (CO) pollution in cold weather. People with coronary artery disease are particularly sensitive to the adverse effects of this air pollutant. The first winter oxygenated gasoline program in the United States was implemented in Denver, Colorado in 1988. The 1990 Clean Air Act Amendments required the use of oxygenated gasoline in several areas of the country that failed to attain the National Ambient Air Quality Standard (NAAQS) for CO. During the winter months of 1992-1993, many new oxygenated gasoline programs were implemented to increase combustion efficiency in cold weather and thereby reduce CO emissions. Methyl tertiary-butyl ether (MTBE) has become the most widely used motor vehicle oxygenate in the U.S., though in some areas, ethanol is the dominant oxygenate used in motor vehicle fuels. Other fuel oxygenates that are in use or may potentially be used include ethyl tertiary-butyl ether (ETBE), tertiary-amyl methyl ether (TAME), diisopropyl ether (DIPE), tertiary-butyl alcohol (TBA), and methanol. Because of limitations in available data, there is less emphasis in this report on these other oxygenates. The Clean Air Act requires at least 2.7% by weight oxygen content for gasoline sold in CO nonattainment areas, and about 15% by volume MTBE or about 7.5% by volume ethanol to achieve this requirement. The purpose of this report is to provide a review of the scientific literature on oxygenated fuels and to assess effects of the winter oxygenated fuels program on air quality, water quality, fuel economy and engine performance, and public health.
Excavated Fe-N-C sites for enhanced electrocatalytic activity in the oxygen reduction reaction.
Jeong, Beomgyun; Shin, Dongyoon; Jeon, Hongrae; Ocon, Joey D; Mun, Bongjin Simon; Baik, Jaeyoon; Shin, Hyun-Joon; Lee, Jaeyoung
Platinum (Pt) is the best electrocatalyst for the oxygen reduction reaction (ORR) in hydrogen fuel cells, but it is an extremely expensive resource. The successful development of a cost-effective non-Pt ORR electrocatalyst will be a breakthrough for the commercialization of hydrogen-air fuel cells. Ball milling has been used to incorporate metal and nitrogen precursors into micropores of carbon more effectively and in the direct nitrogen-doping of carbon under highly pressurized nitrogen gas in the process of the preparation of non-noble ORR catalysts. In this study, we first utilize ball milling to excavate the ORR active sites embedded in Fe-modified N-doped carbon nanofibers (Fe-N-CNFs) by pulverization. The facile ball-milling process resulted in a significant enhancement in the ORR activity and the selectivity of the Fe-N-CNFs owing to the higher exposure of the metal-based catalytically active sites. The degree of excavation of the Fe-based active sites in the Fe-N-CNFs for the ORR was investigated with cyclic voltammetry, X-ray photoelectron spectroscopy, and pore-size distribution analysis. We believe that this simple approach is useful to improve alternative ORR electrocatalysts up to the level necessary for practical applications. PMID:24700786
Platinum-Based Nanowire Networks with Enhanced Oxygen-Reduction Activity
NASA Astrophysics Data System (ADS)
Galinski, Henning; Ryll, Thomas; Lin, Yang; Scherrer, Barbara; Evans, Anna; Gauckler, Ludwig J.; D÷beli, Max
Pt-Al and Pt-Y-Al thin-film electrodes on yttria-stabilized zirconia electrolytes were prepared by dealloying of cosputtered Pt-Al or Pt-Y-Al films. The selective dissolution of Al from the Pt-alloy compound causes the formation of a highly porous nanowire network with a mean branch thickness below 25 nm and a pore intercept length below 35 nm. The oxygen-reduction capability of the resulting electrodes is analyzed in a micro-solid-oxide fuel-cell setup at elevated temperatures (598-873 K). Here, we demonstrate that these nanoporous thin films excel "state-of-the-art" fuel-cell electrodes in terms of catalytic activity and thermal stability. The nanoporous Pt electrodes exhibit exchange-current densities that are up to 13 times higher than conventional Pt electrodes, measured at 648 K. It is shown that the enhanced intrinsic electrocatalytic activity of these Pt electrodes is achieved by the addition of yttrium as a ternary constituent, which allows for an engineering of the material's band structure.
Piperlongumine induces pancreatic cancer cell death by enhancing reactive oxygen species and DNA damage
Dhillon, Harsharan; Chikara, Shireen; Reindl, Katie M.
Pancreatic cancer is one of the most deadly cancers with a nearly 95% mortality rate. The poor response of pancreatic cancer to currently available therapies and the extremely low survival rate of pancreatic cancer patients point to a critical need for alternative therapeutic strategies. The use of reactive oxygen species (ROS)-inducing agents has emerged as an innovative and effective strategy to treat various cancers. In this study, we investigated the potential of a known ROS inducer, piperlongumine (PPLGM), a bioactive agent found in long peppers, to induce pancreatic cancer cell death in cell culture and animal models. We found that PPLGM inhibited the growth of pancreatic cancer cell cultures by elevating ROS levels and causing DNA damage. PPLGM-induced DNA damage and pancreatic cancer cell death was reversed by treating the cells with an exogenous antioxidant. Similar to the in vitro studies, PPLGM caused a reduction in tumor growth in a xenograft mouse model of human pancreatic cancer. Tumors from the PPLGM-treated animals showed decreased Ki-67 and increased 8-OHdG expression, suggesting PPLGM inhibited tumor cell proliferation and enhanced oxidative stress. Taken together, our results show that PPLGM is an effective inhibitor for in vitro and in vivo growth of pancreatic cancer cells, and that it works through a ROS-mediated DNA damage pathway. These findings suggest that PPLGM has the potential to be used for treatment of pancreatic cancer. PMID:25530945
Smouldering Combustion Phenomena in Science and Technology
Guillermo Rein
Smouldering is the slow, low-temperature, flameless form of combustion of a condensed fuel. It poses safety and environmental hazards and allows novel technological application but its fundamentals remain mostly unknown to the scientific community. The terms filtering combustion, smoking problem, deep seated fires, hidden fires, peat or peatlands fires, lagging fires, low oxygen combustion, in-situ combustion, fireflood and underground gasification,
Supersonic Inlet with Pylons Set and Star-Shaped Forebody for Mixing, Combustion and Thrust Enhancement
NASA Technical Reports Server (NTRS)
Gilinsky, M.; Gonor, A. L.; Khaikine, V. A.; Blankson, I. M.
Two new approaches are discussed in this paper for application in the Scramjet inlet of an air-breathing propulsion system: 1) In the first approach, the pylon set is installed in the rectangular inlet near the cowl front edge. For a quasi-axisymmetric inlet, a similar set is installed along the Star-shaped forebody axis. This set contains 3 - 4 airfoil-shaped strips or cross-sectional rings depending on the type of inlet. The inlets: rectangular, axisymmetric or star-shaped, are located at different distances from the forebody. Fuel injection takes place through these pylons, which provides for uniform mixing downstream. The locations, sizes and angles of these pylons are very important for efficient application. Optimal values of geometrical parameters were determined from multi-parametric NSE-based numerical simulations of the laminar and turbulent external/internal flows. These simulations have shown significant benefits for mixing, combustion and thrust of the proposed approach by comparison with traditional well-known designs. Experimental tests will be conducted soon at the NASA LaRC and Institute of Mechanics at Moscow State University. Preliminary estimates are very promising.
Combustion-enhancement and pollutant-control research with acoustically induced mixing. Final report
Faeser, R.J.; Rudnicki, M.I.
The application of acoustic energy to a pulverized-coal flame was investigated to determine its influence on NO/sub x/ generation, combustion intensity and turndown ratio. A bench-scale, research combustor utilizing plug flow and burning 5 lb/hr of Illinois No. 6C coal was tested as both a two-stage and single-staged combustor with and without acoustics applied. Sound intensities up to 149 dB at frequencies from 1100 Hz to 3000 Hz were evaluated. The experiments showed that NO/sub x/ generation was unaffected by acoustic mixing in the low first-stage stoichiometric ratio (SR/sub 1/) range of a two-staged combustor and increased up to 20% by use of acoustics in the high SR/sub 1/ range. A similar increase in NO/sub x/ with acoustics was seen in a single stage combustor operating with 5% to 20% excess air. The testing further showed that carbon burnup efficiency could be increased by 7 to 9 percentage points (in the 90 to 100% range) when acoustics were applied. Limited test data indicated that volumetric heat release and turndown ratio could be increased by a factor of 2.8. 21 figures, 3 tables.
Enhanced oxygen-tolerance of the full heterotrimeric membrane-bound [NiFe]-hydrogenase of Ralstonia eutropha.
Radu, Valentin; Frielingsdorf, Stefan; Evans, Stephen D; Lenz, Oliver; Jeuken, Lars J C
Hydrogenases are oxygen-sensitive enzymes that catalyze the conversion between protons and hydrogen. Water-soluble subcomplexes of membrane-bound [NiFe]-hydrogenases (MBH) have been extensively studied for applications in hydrogen-oxygen fuel cells as they are relatively tolerant to oxygen, although even these catalysts are still inactivated in oxidative conditions. Here, the full heterotrimeric MBH of Ralstonia eutropha, including the membrane-integral cytochrome b subunit, was investigated electrochemically using electrodes modified with planar tethered bilayer lipid membranes (tBLM). Cyclic voltammetry and chronoamperometry experiments show that MBH, in equilibrium with the quinone pool in the tBLM, does not anaerobically inactivate under oxidative redox conditions. In aerobic environments, the MBH is reversibly inactivated by O2, but reactivation was found to be fast even under oxidative redox conditions. This enhanced resistance to inactivation is ascribed to the oligomeric state of MBH in the lipid membrane. PMID:24866391
Enhancement of singlet oxygen production based on FRET between Coumarin tri-compound and CdSe/ZnS QDs
NASA Astrophysics Data System (ADS)
Duong, Hong Dinh; Lee, Jee Won; Rhee, Jong Il
The compatibility between coumarin-derived dendrimer (CdD)-captured silica particles (SiCdDs) and watersoluble CdSe/ZnS quantum dots (QDs) in the FRET process improved the excited state of QDs in the reaction of singlet oxygen production under LED irradiation. Sol-gel GA was successfully used to improve the binding between SiCdDs and QDs. Singlet oxygen production using QDs coated with SiCdDs through sol-gel GA was enhanced by about 80 % compared to that achieved using QDs only. The single oxygen produced by the QDs, the QDs/GA-SiCdDs complexes and the SiCdDs/GA-QDs complexes in this study could be used in the treatment of HeLa cells.
Enhanced Oxygen-Tolerance of the Full Heterotrimeric Membrane-Bound [NiFe]-Hydrogenase of Ralstonia eutropha
Hydrogenases are oxygen-sensitive enzymes that catalyze the conversion between protons and hydrogen. Water-soluble subcomplexes of membrane-bound [NiFe]-hydrogenases (MBH) have been extensively studied for applications in hydrogenľoxygen fuel cells as they are relatively tolerant to oxygen, although even these catalysts are still inactivated in oxidative conditions. Here, the full heterotrimeric MBH of Ralstonia eutropha, including the membrane-integral cytochrome b subunit, was investigated electrochemically using electrodes modified with planar tethered bilayer lipid membranes (tBLM). Cyclic voltammetry and chronoamperometry experiments show that MBH, in equilibrium with the quinone pool in the tBLM, does not anaerobically inactivate under oxidative redox conditions. In aerobic environments, the MBH is reversibly inactivated by O2, but reactivation was found to be fast even under oxidative redox conditions. This enhanced resistance to inactivation is ascribed to the oligomeric state of MBH in the lipid membrane. PMID:24866391
Enhanced coal gasification heated by unmixed combustion integrated with an hybrid system of SOFC\\/GT
Pilar Lisbona; Luis M. Romeo
For clean utilization of coal, enhanced gasification by in situ CO2 capture has the advantage that hydrogen production efficiency is increased while no energy is required for CO2 separation. The unmixed fuel process uses a sorbent material as CO2 carrier and consists of three coupled reactors: a coal gasifier where CO2 is captured generating a H2-rich gas that can be
Evaluation of alkali concentration in conditions relevant to oxygen/natural gas glass furnaces by laser-induced breakdown spectroscopy.
Walsh, Peter M.; Molina, Alejandro; Shaddix, Christopher R.; Blevins, Linda Gail; Sickafoose, Shane M.
A number of industrial combustion systems are adopting oxygen-enhanced firing to improve heat transfer characteristics and reduce emissions. The exhaust gas from these systems is dominated by H2O and CO2 and therefore has substantially different gas properties from traditional combustion exhaust. In the past, laser-induced breakdown spectroscopy (LIBS) has been successfully used for the evaluation of alkali aerosol concentrations in air-based combustion systems. This paper presents results of LIBS measurements of alkali concentrations in a laboratory calibration setup and in an oxygen/natural gas container glass furnace. It shows how both gas conditions (composition and temperature) and the molecular form of the alkali species affect the LIBS signals. The paper proposes strategies for mitigating these effects in future applications of LIBS in oxygen-enhanced combustion systems.
Experiments of Supersonic Mixing and Combustion Enhancement Using Alternating-Wedge Strut: Part 1 ŚEffects of Supersonic Streamwise Vortices in a Scramjet Combustor
NASA Astrophysics Data System (ADS)
Sunami, Tetsuji; Wendt, Michael N.; Nishioka, Michio; Murakami, Atsuo; Kudou, Kenji
Effects of streamwise vortices on enhancement of supersonic mixing and combustion are examined in a scramjet combustor whose main flow is a Mach 2.45 vitiation air stream with a total temperature of 2200K. The fuel injector strut called ôAlternating-Wedge Strut (AW-Strut)ö is used to generate streamwise vortices and to inject hydrogen fuel into their core region. For comparison, a generic strut, ôMO-Strut,ö without streamwise vortex generation is also examined. Direct visualization of flame shows rapid formation of streamwise vortices and ignition/combustion within the vortices already upstream of the strut trailing edge. Wall pressure measurements along the combustor show that for the case of AW-Strut the wall pressure rise due to combustion is almost twice that of the MO-Strut case. Gas sampling at the combustor exit demonstrates that much more uniform fuel/air mixing is obtained for the case of AW-Strut. The present results verify the phenomenal performance of the supersonic streamwise vortices for enhancement of supersonic mixing and combustion.
Enhanced sunlight photocatalytic activity of Ag3PO4 decorated novel combustion synthesis derived TiO2 nanobelts for dye and bacterial degradation.
Eswar, Neerugatti KrishnaRao; Ramamurthy, Praveen Chandrashekarapura; Madras, Giridhar
This study demonstrates the synthesis of TiO2 nanobelts using solution combustion derived TiO2 with enhanced photocatalytic activity for dye degradation and bacterial inactivation. Hydrothermal treatment of combustion synthesized TiO2 resulted in unique partially etched TiO2 nanobelts and Ag3PO4 was decorated using the co-precipitation method. The catalyst particles were characterized using X-ray diffraction analysis, BET surface area analysis, diffuse reflectance and electron microscopy. The photocatalytic properties of the composites of Ag3PO4 with pristine combustion synthesized TiO2 and commercial TiO2 under sunlight were compared. Therefore the studies conducted proved that the novel Ag3PO4/unique combustion synthesis derived TiO2 nanobelt composites exhibited extended light absorption, better charge transfer mechanism and higher generation of hydroxyl and hole radicals. These properties resulted in enhanced photodegradation of dyes and bacteria when compared to the commercial TiO2 nanocomposite. These findings have important implications in designing new photocatalysts for water purification. PMID:26056065
Enhanced photocatalytic performance of N-nitrosodimethylamine on TiO2 nanotube based on the role of singlet oxygen.
Guo, Xiaoyan; Li, Qilin; Zhang, Man; Long, Mingce; Kong, Lulu; Zhou, Qixing; Shao, Huaiqi; Hu, Wanli; Wei, Tingting
N-nitrosodimethylamine (NDMA) photocatalytic degradation performance and mechanism were investigated on the TiO2 nanotube prepared from anatase TiO2 nanopowder in terms of the production of reactive oxygen species including hydroxyl radical, singlet oxygen and superoxide radical. Significantly higher NDMA degradation efficiency was obtained on anatase TiO2 nanotube rather than anatase TiO2 nanopowder. The tubular morphology may be responsible for almost 100% NDMA removal on TiO2 nanotube, presumably due to its confinement effect leading to NDMA molecules within the nanotube being attacked by reactive oxygen species such as hydroxyl radical and singlet oxygen, and initiating reaction inside the nanotube. In particular, the ability of the nanotubular structure of TiO2 nanotube to promote a singlet oxygen oxidation pathway contributes much to the enhanced NDMA degradation efficiency and favors the formation of dimethylamine and NO3(-). Such function originating from nanotube morphology could bring new insights for the photocatalytic degradation of organic pollutants. PMID:25290358
Multiparametric imaging of tumor oxygenation, redox status, and anatomical structure using Overhauser-enhanced MRI-prepolarized MRI system.
Ahn, Kang-Hyun; Scott, Greig; Stang, Pascal; Conolly, Steve; Hristov, Dimitre
An integrated Overhauser-enhanced MRI-Prepolarized MRI system was developed to obtain radiobiological information that could be accurately coregistered with diagnostic quality anatomic images. EPR and NMR images were acquired through the double resonance technique and field cycling of the main magnetic field from 5 mT to 0.5 T. Dedicated EPR and NMR coils were devised to minimize radiofrequency power deposition with high signal-to-noise ratio. Trityl and nitroxide radicals were used to characterize oxygen and redox sensitivities of multispin echo Overhauser-enhanced MRI. Oxygen resolution of 3 mmHg was obtained from 2 mM deoxygenated trityl phantoms. Trityl radicals were stable in reducing environments and did not alter the redox-sensitive decaying rate of the nitroxide signals. Nitroxide radicals had a compounding effect for the trityl oximetry. Tumor oxygenation and redox status were acquired with anatomical images by injecting trityl and nitroxide probes subsequently in murine tumors. The Overhauser-enhanced MRI-Prepolarized MRI system is ready for quantitative longitudinal imaging studies of tumor hypoxia and redox status as radiotherapy prognostic factors. PMID:21500268
Pretreatment of Parsley (Petroselinum crispum L.) Suspension Cultures with Methyl Jasmonate Enhances Elicitation of Activated Oxygen Species.
Kauss, H.; Jeblick, W.; Ziegler, J.; Krabler, W.
Suspension-cultured cells of parsley (Petroselinum crispum L.) were used to demonstrate an influence of jasmonic acid methyl ester (JAME) on the elicitation of activated oxygen species. Preincubation of the cell cultures for 1 d with JAME greatly enhanced the subsequent induction by an elicitor preparation from cell walls of Phytophtora megasperma f. sp. glycinea (Pmg elicitor) and by the polycation chitosan. Shorter preincubation times with JAME were less efficient, and the effect was saturated at about 5 [mu]M JAME. Treatment of the crude Pmg elicitor with trypsin abolished induction of activated oxygen species, an effect similar to that seen with elicitation of coumarin secretion. These results suggest that JAME conditioned the parsley suspension cells in a time-dependent manner to become more responsive to elicitation, reminiscent of developmental effects caused by JAME in whole plants. It is interesting that pretreatment of the parsley cultures with 2,6-dichloroisonicotinic and 5-chlorosalicylic acid only slightly enhanced the elicitation of activated oxygen species, whereas these substances greatly enhanced the elicitation of coumarin secretion. Therefore, these presumed inducers of systemic acquired resistance exhibit a specificity different from JAME. PMID:12232189
Enhancement in Figure of Merit ( ZT) by Annealing of BiTe Nanostructures Synthesized by Microwave-Assisted Flash Combustion
NASA Astrophysics Data System (ADS)
Kaur, Harjeet; Sharma, Lalit; Singh, Simrjit; Sivaiah, Bathula; Reddy, G. B.; Senguttuvan, T. D.
Uniform polycrystalline bismuth telluride (BiTe) nanowires of diameter 100 nm to 150 nm and hexagonal nanoplates with thickness of 50 nm to 100 nm have been successfully synthesized by the microwave-assisted flash combustion technique. The formation of BiTe nanostructures depends on the type of fuel and the oxidant-to-fuel ratio, which in turn affect the reaction time and reaction temperature. Spark plasma sintering has been employed for compaction and sintering of both as-synthesized as well as annealed BiTe powders. Increasing the sintering temperature while using faster sintering cycles reduced the porosity, resulting in high densification while preserving the nanostructures. The dimensionless figure of merit ( ZT) was evaluated from the Seebeck coefficient, electrical resistivity, and thermal conductivity values over the range from 300 K to 600 K. The effect of annealing on the enhancement of ZT is discussed. These evaluations suggest that the rarely studied BiTe is a potential candidate for thermoelectric applications at low temperatures.
Hydrogen-Enhanced Lunar Oxygen Extraction and Storage Using Only Solar Power
NASA Technical Reports Server (NTRS)
Burton, rodney; King, Darren
The innovation consists of a thermodynamic system for extracting in situ oxygen vapor from lunar regolith using a solar photovoltaic power source in a reactor, a method for thermally insulating the reactor, a method for protecting the reactor internal components from oxidation by the extracted oxygen, a method for removing unwanted chemical species produced in the reactor from the oxygen vapor, a method for passively storing the oxygen, and a method for releasing high-purity oxygen from storage for lunar use. Lunar oxygen exists in various types of minerals, mostly silicates. The energy required to extract the oxygen from the minerals is 30 to 60 MJ/kg O. Using simple heating, the extraction rate depends on temperature. The minimum temperature is approximately 2,500 K, which is at the upper end of available oven temperatures. The oxygen is released from storage in a purified state, as needed, especially if for human consumption. This method extracts oxygen from regolith by treating the problem as a closed batch cycle system. The innovation works equally well in Earth or Lunar gravity fields, at low partial pressure of oxygen, and makes use of in situ regolith for system insulation. The innovation extracts oxygen from lunar regolith using a method similar to vacuum pyrolysis, but with hydrogen cover gas added stoichiometrically to react with the oxygen as it is produced by radiatively heating regolith to 2,500 K. The hydrogen flows over and through the heating element (HE), protecting it from released oxygen. The H2 O2 heat of reaction is regeneratively recovered to assist the heating process. Lunar regolith is loaded into a large-diameter, low-height pancake reactor powered by photovoltaic cells. The reactor lid contains a 2,500 K HE that radiates downward onto the regolith to heat it and extract oxygen, and is shielded above by a multi-layer tungsten radiation shield. Hydrogen cover gas percolates through the perforated tungsten shielding and HE, preventing oxidation of the shielding and HE, and reacting with the oxygen to form water vapor. The water vapor is filtered through solid regolith to remove unwanted extraction byproducts, and then condensed to a liquid state and stored at 300 to 325 K. Conversion to usable oxygen is achieved by pumping liquid water into a high-pressure electrolyzer, storing the gaseous oxygen at high pressure for use, and diverting the hydrogen back to the reactor or to storage. The results from this design effort show that this oxygen-generating concept can be developed in an efficient system with low specific mass. Advantages include use of regolith as an oxygen source, filter, and thermal insulator. The system can be tested in Earth gravity and can be expected to operate similarly in lunar gravity. The system is scalable, either by increasing the power level and output of a standard module, or by employing multiple modules.
Oxygen vacancy enhanced photocatalytic activity of pervoskite SrTiO(3).
Tan, Huaqiao; Zhao, Zhao; Zhu, Wan-Bin; Coker, Eric N; Li, Binsong; Zheng, Min; Yu, Weixing; Fan, Hongyou; Sun, Zaicheng
A facile and general method has been developed to fabricate oxygen vacancies on perovskite SrTiO3 (STO) nanocrystals through a controllable solid-state reaction of NaBH4 and SrTiO3 nanocrystals. STO samples with tunable color, oxygen vacancy concentration on nanocrystal surface have been synthesized. TEM results reveal that these STO samples have a crystalline core/amorphous shell structure (SrTiO3@SrTiO3-x). XPS and EPR results disclose that the oxygen vacancy concentration increases with the increase of reaction time and temperature. The concentration of oxygen vacancies calculated from TGA data, could reach 5.07% (atom) in this study. UV-vis spectra and photocatalytic results indicate that oxygen vacancies on STO surface play an important role in influencing the light absorption and photocatalytic performance. However, an excess amount of oxygen vacancies leads to a decrease of photocatalytic performance. The optimal photocatalytic activity for H2 production under UV-vis irradiation is up to 2.2 mmol h(-1) g(-1), which is about 2.3 times than the original SrTiO3, corresponding to 3.28% (atom) of oxygen vacancy concentration. PMID:25311356
Emission Assessment From Full-scale Co-combustion Tests Of Binder-enhanced dRDF Pellets And High Sulfur Coal At Argonne National Laboratory
O. O. OhIsson; C. D. Livengood; K. E. Daugherty
Argonne National Laboratory (ANL) and University of North Texas (UNT) research teams collected over 800 emissions and ash samples during the combustion of over 650 tons of binder enhanced densified refuse-drived fuel (b-dRDF) pellets with high sulfur coal in a spreader-stoker boiler at ANL. This full-scale test burn was conducted to validate predictions from laboratory and pilot scale test results
Helmich, M.J.; Hoagland, M.C.; Hubbard, R.L.; Schaub, F.S.
A method of combusting natural gas fuel in a two cycle, turbocharged internal combustion engine substantially reduces the production of nitrogen-oxygen emissions. An improved turbocharger design provides increased air charging pressure, produces a controlled lean air/fuel mixture and lowers peak combustion temperatures. A jet cell ignition device ensures uniform, reliable ignition of the lean air/fuel mixture under all operating conditions and the lean air/fuel mixture in turn encourages complete fuel combustion and provides excellent combustion characteristics with methane, ethane and heavier paraffinic hydrocarbon fuels. These structural modifications and adjustment of other operating parameters combine to reduce nitric oxide (NO) and nitrogen dioxide (NO/sub 2/) emissions by as much as 75% while effecting only a negligible increase in fuel consumption.
Ultrathin Spinel-Structured Nanosheets Rich in Oxygen Deficiencies for Enhanced Electrocatalytic Water Oxidation.
Bao, Jian; Zhang, Xiaodong; Fan, Bo; Zhang, Jiajia; Zhou, Min; Yang, Wenlong; Hu, Xin; Wang, Hui; Pan, Bicai; Xie, Yi
Electrochemical water splitting is a clean technology for H2 fuels, but greatly hindered by the slow kinetics of the oxygen evolution reaction (OER). Herein, a series of spinel-structured nanosheets with oxygen deficiencies and ultrathin thicknesses were designed to increase the reactivity and the number of active sites of the catalysts, which were then taken as an excellent platform for promoting the water oxidation process. Theoretical investigations showed that the oxygen vacancies confined in the ultrathin nanosheet could lower the adsorption energy of H2 O, leading to increased OER efficiency. As expected, the NiCo2 O4 ultrathin nanosheets rich in oxygen vacancies exhibited a large current density of 285?mA?cm(-2) at 0.8?V and a small overpotential of 0.32?V, both of which are superior to the corresponding values of bulk samples or samples with few oxygen deficiencies and even higher than those of most reported non-precious-metal catalysts. This work should provide a new pathway for the design of advanced OER catalysts. PMID:25951435
Barium carbonate nanoparticle to enhance oxygen reduction activity of strontium doped lanthanum ferrite for solid oxide fuel cell
NASA Astrophysics Data System (ADS)
Hong, Tao; Chen, Fanglin; Xia, Changrong
BaCO3 nanoparticles are demonstrated as outstanding catalysts for high-temperature oxygen reduction reaction (ORR) on the La0.8Sr0.2FeO3-? (LSF) cathode for solid oxide fuel cells (SOFCs) based on ytrria-stabilized zirconia (YSZ) electrolytes. Thermal gravitational and X-ray diffraction measurements show that BaCO3 is stable and chemically compatible with LSF under the fabrication and operation conditions of intermediate-temperature SOFCs. The BaCO3 nanoparticles can greatly reduce the interfacial polarization resistance; from 2.96 to 0.84 ? cm2 at 700 ░C when 12.9wt% BaCO3 is infiltrated to the porous LSF electrode on the YSZ electrolyte. Electrochemical impedance spectroscopy shows that there is about one order of magnitude decrease in the low-frequency resistance, indicating that BaCO3 nanoparticles can greatly enhance the surface steps for ORR. Electrical conductivity relaxation investigation indicates about one order of magnitude increase in the chemical oxygen surface exchange coefficient when BaCO3 is applied, directly demonstrating significant increase in the kinetics for ORR. In addition, LSF cathodes with infiltrated BaCO3 nanoparticles have shown excellent stability and substantially enhanced cell performance as demonstrated with single cells, suggesting BaCO3 nanoparticles are very effective in enhancing ORR on LSF.
An algorithm for sensing venous oxygenation using ultrasound-modulated light enhanced by microbubbles
NASA Astrophysics Data System (ADS)
Honeysett, Jack E.; Stride, Eleanor; Deng, Jing; Leung, Terence S.
Near-infrared spectroscopy (NIRS) can provide an estimate of the mean oxygen saturation in tissue. This technique is limited by optical scattering, which reduces the spatial resolution of the measurement, and by absorption, which makes the measurement insensitive to oxygenation changes in larger deep blood vessels relative to that in the superficial tissue. Acousto-optic (AO) techniques which combine focused ultrasound (US) with diffuse light have been shown to improve the spatial resolution as a result of US-modulation of the light signal, however this technique still suffers from low signal-to-noise when detecting a signal from regions of high optical absorption. Combining an US contrast agent with this hybrid technique has been proposed to amplify an AO signal. Microbubbles are a clinical contrast agent used in diagnostic US for their ability to resonate in a sound field: in this work we also make use of their optical scattering properties (modelled using Mie theory). A perturbation Monte Carlo (pMC) model of light transport in a highly absorbing blood vessel containing microbubbles surrounded by tissue is used to calculate the AO signal detected on the top surface of the tissue. An algorithm based on the modified Beer-Lambert law is derived which expresses intravenous oxygen saturation in terms of an AO signal. This is used to determine the oxygen saturation in the blood vessel from a dual wavelength microbubble-contrast AO measurement. Applying this algorithm to the simulation data shows that the venous oxygen saturation is accurately recovered, and this measurement is robust to changes in the oxygenation of the superficial tissue layer.
Creatine supplementation enhances corticomotor excitability and cognitive performance during oxygen deprivation.
Turner, Clare E; Byblow, Winston D; Gant, Nicholas
Impairment or interruption of oxygen supply compromises brain function and plays a role in neurological and neurodegenerative conditions. Creatine is a naturally occurring compound involved in the buffering, transport, and regulation of cellular energy, with the potential to replenish cellular adenosine triphosphate without oxygen. Creatine is also neuroprotective in vitro against anoxic/hypoxic damage. Dietary creatine supplementation has been associated with improved symptoms in neurological disorders defined by impaired neural energy provision. Here we investigate, for the first time in humans, the utility of creatine as a dietary supplement to protect against energetic insult. The aim of this study was to assess the influence of oral creatine supplementation on the neurophysiological and neuropsychological function of healthy young adults during acute oxygen deprivation. Fifteen healthy adults were supplemented with creatine and placebo treatments for 7 d, which increased brain creatine on average by 9.2%. A hypoxic gas mixture (10% oxygen) was administered for 90 min, causing global oxygen deficit and impairing a range of neuropsychological processes. Hypoxia-induced decrements in cognitive performance, specifically attentional capacity, were restored when participants were creatine supplemented, and corticomotor excitability increased. A neuromodulatory effect of creatine via increased energy availability is presumed to be a contributing factor of the restoration, perhaps by supporting the maintenance of appropriate neuronal membrane potentials. Dietary creatine monohydrate supplementation augments neural creatine, increases corticomotor excitability, and prevents the decline in attention that occurs during severe oxygen deficit. This is the first demonstration of creatine's utility as a neuroprotective supplement when cellular energy provision is compromised. PMID:25632150
Y.P. Chugh; D. Biswas; D. Deb
This project has successfully demonstrated that the extraction ratio in a room-and-pillar panel at an Illinois mine can be increased from the current value of approximately 56% to about 64%, with backfilling done from the surface upon completion of all mining activities. This was achieved without significant ground control problems due to the increased extraction ratio. The mined-out areas were backfilled from the surface with gob, coal combustion by-products (CCBs), and fine coal processing waste (FCPW)-based paste backfill containing 65%-70% solids to minimize short-term and long-term surface deformations risk. This concept has the potential to increase mine productivity, reduce mining costs, manage large volumes of CCBs beneficially, and improve the miner's health, safety, and environment. Two injection holes were drilled over the demonstration panel to inject the paste backfill. Backfilling was started on August 11, 1999 through the first borehole. About 9,293 tons of paste backfill were injected through this borehole with a maximum flow distance of 300-ft underground. On September 27, 2000, backfilling operation was resumed through the second borehole with a mixture of F ash and FBC ash. A high-speed auger mixer (new technology) was used to mix solids with water. About 6,000 tons of paste backfill were injected underground through this hole. Underground backfilling using the ''Groutnet'' flow model was simulated. Studies indicate that grout flow over 300-foot distance is possible. Approximately 13,000 tons of grout may be pumped through a single hole. The effect of backfilling on the stability of the mine workings was analyzed using SIUPANEL.3D computer program and further verified using finite element analysis techniques. Stiffness of the backfill mix is most critical for enhancing the stability of mine workings. Mine openings do not have to be completely backfilled to enhance their stability. Backfill height of about 50% of the seam height is adequate to minimize surface deformations. Freeman United Coal Company performed engineering economic evaluation studies for commercialization. They found that the costs for underground management at the Crown III mine would be slightly higher than surface management at this time. The developed technologies have commercial potential but each site must be analyzed on its merit. The Company maintains significant interest in commercializing the technology.
Discovery of small-molecule enhancers of reactive oxygen species that are nontoxic or cause genotype-selective cell death.
Adams, Drew J; Boskovic, Zarko V; Theriault, Jimmy R; Wang, Alex J; Stern, Andrew M; Wagner, Bridget K; Shamji, Alykhan F; Schreiber, Stuart L
Elevation of reactive oxygen species (ROS) levels has been observed in many cancer cells relative to nontransformed cells, and recent reports have suggested that small-molecule enhancers of ROS may selectively kill cancer cells in various in vitro and in vivo models. We used a high-throughput screening approach to identify several hundred small-molecule enhancers of ROS in a human osteosarcoma cell line. A minority of these compounds diminished the viability of cancer cell lines, indicating that ROS elevation by small molecules is insufficient to induce death of cancer cell lines. Three chemical probes (BRD5459, BRD56491, BRD9092) are highlighted that most strongly elevate markers of oxidative stress without causing cell death and may be of use in a variety of cellular settings. For example, combining nontoxic ROS-enhancing probes with nontoxic doses of L-buthionine sulfoximine, an inhibitor of glutathione synthesis previously studied in cancer patients, led to potent cell death in more than 20 cases, suggesting that even nontoxic ROS-enhancing treatments may warrant exploration in combination strategies. Additionally, a few ROS-enhancing compounds that contain sites of electrophilicity, including piperlongumine, show selective toxicity for transformed cells over nontransformed cells in an engineered cell-line model of tumorigenesis. These studies suggest that cancer cell lines are more resilient to chemically induced increases in ROS levels than previously thought and highlight electrophilicity as a property that may be more closely associated with cancer-selective cell death than ROS elevation. PMID:23477340
Structural features and enhanced high-temperature oxygen ion transport in SrFe{sub 1-x}Ta{sub x}O{sub 3-{delta}}
Markov, Alexey A.; Shalaeva, Elizaveta V.; Tyutyunnik, Alexander P.; Kuchin, Vasily V. [Institute of Solid State Chemistry of Ural Branch of RAS, 91 Pervomaiskaya Str., 620990 Yekaterinburg (Russian Federation); Patrakeev, Mikhail V., E-mail: email@example.com [Institute of Solid State Chemistry of Ural Branch of RAS, 91 Pervomaiskaya Str., 620990 Yekaterinburg (Russian Federation); Leonidov, Ilya A.; Kozhevnikov, Victor L. [Institute of Solid State Chemistry of Ural Branch of RAS, 91 Pervomaiskaya Str., 620990 Yekaterinburg (Russian Federation)
Structural features, oxygen non-stoichiometry and transport properties are studied in the oxide series SrFe{sub 1-x}Ta{sub x}O{sub 3-{delta}}, where x=0.2, 0.3 and 0.4. X-ray diffraction and electron microscopy data evidence formation of the inhomogeneous materials at x=0.3 and 0.4, which include phase constituents with a cubic perovskite and a double perovskite structure types. The composition, the amount and the typical grain size of the phase inhomogeneities are shown to depend both on doping and oxygen content. The increased oxygen-ion conductivity is observed in oxygen depleted materials, which is explained by the increase in the amount of cubic perovskite-like phase and development of interfacial pathways favorable for enhanced oxygen ion transport. - Graphical abstract: The structural studies, oxygen content and conductivity measurements suggest that oxygen depletion from the double perovskite phase constituent of SrFe{sub 1-x}Ta{sub x}O{sub 3-{delta}} for x>0.2 is accompanied by formation of pathways for fast ion transport. Black-Small-Square Highlights: Black-Right-Pointing-Pointer The double perovskite type regions are shown to exist in SrFe{sub 1-x}Ta{sub x}O{sub 3-{delta}}. Black-Right-Pointing-Pointer The oxygen depletion is accompanied with phase separation. Black-Right-Pointing-Pointer The phase separation favors formation of pathways for enhanced oxygen ion transport.
Pt-Cu bimetallic electrocatalysts with enhanced catalytic properties for oxygen reduction.
Zhu, Chun-Mei; Gao, Ang; Wang, Yuan; Liu, Yan
A highly active Pt-Cu bimetallic catalyst for the electrocatalytic oxygen reduction reaction, with an average diameter of 2.9 nm and a Cu/Pt ratio of 0.30 for the bimetallic nanoparticles, was prepared by capturing Pt-Cu alloy nanoparticles on melem-modified carbon, followed by removing 90% of copper from the alloy NPs. PMID:25089299
Synergistically enhanced oxygen reduction activity of MnOx-CeO2/Ketjenblack composites.
Chen, Jiajie; Zhou, Nan; Wang, Haiyan; Peng, Zhiguang; Li, Huiyong; Tang, Yougen; Liu, Kun
Here we report a hybrid of MnOx-CeO2/Ketjenblack as a novel catalyst for oxygen reduction reaction (ORR) by a facile strategy. This hybrid exhibits comparable activity and better stability towards ORR than the commercial 20 wt% Pt/C due to the synergistic effect. PMID:26006057
A fluidized-bed combustion process with inherent CO 2 separation; application of chemical-looping combustion
Anders Lyngfelt; Bo Leckner; Tobias Mattisson
For combustion with CO2 capture, chemical-looping combustion has the advantage that no energy is lost for the separation of CO2. In chemical-looping combustion oxygen is transferred from the combustion air to the gaseous fuel by means of an oxygen carrier. The fuel and the combustion air are never mixed, and the gases from the oxidation of the fuel, CO2 and
Enhanced oxygen dissociation in a propagating constricted discharge formed in a self-pulsing atmospheric pressure microplasma jet
NASA Astrophysics Data System (ADS)
Schr÷der, Daniel; Burhenn, Sebastian; Kirchheim, Dennis; Schulz-von der Gathen, Volker
We report on the propagation of a constricted discharge feature in a repetitively self-pulsing microplasma jet operated in helium with a 0.075 vol% molecular oxygen admixture in ambient air environment. The constricted discharge is about 1 mm in width and repetitively ignites at the point of smallest electrode distance in a wedge-shaped electrode configuration, propagates through the discharge channel towards the nozzle, extinguishes, and re-ignites at the inlet at frequencies in the kHz range. It co-exists with a homogeneous, volume-dominated low temperature (T ? 300 K) ?-mode glow. Time-resolved measurements of nitrogen molecule C-state and nitrogen molecule ion B-state emission bands reveal an increase of the rotational temperature within the constricted discharge to about 600 K within 50 Ás. Its propagation velocity was determined by phase-resolved diagnostics to be similar to the gas velocity, in the order of 40 m s-1. Two-photon absorption laser-induced fluorescence spectroscopy synchronized to the self-pulsing reveals spatial regions of increased oxygen atom densities co-propagating with the constricted discharge feature. The generated oxygen pulse density is about ten times higher than in the co-existing homogeneous ?-mode. Densities reach about 1.5 Î 1016 cm-3 at average temperatures of 450 K at the nozzle. This enhanced dissociation of about 80% is attributed to the continuous interaction of the constricted discharge to the co-propagating gas volume.
Enhanced cohesion of photo-oxygenated fullerene films: A new opportunity for lithography
NASA Astrophysics Data System (ADS)
Hebard, A. F.; Eom, C. B.; Fleming, R. M.; Chabal, Y. J.; Muller, A. J.; Glarum, S. H.; Pietsch, G. J.; Haddon, R. C.; Mujsce, A. M.; Paczkowski, M. A.; Kochanski, G. P.
The irradiation of sublimed fullerene (C60 and C70) thin films with ultraviolet light in an oxygen-rich ambient has been found to lead to a substantially increased cohesive energy in the fullerene solid. The decreased solubility and lower vapor pressure of the phototransformed material enables wet (organic solvents) or dry (thermal or photon-induced sublimation) development of photo-defined negative images. One micrometer wide lines with good edge definition are demonstrated. X-ray, infrared, optical absorption, and high performance liquid chromatography reveal that photo-oxygenated C60 retains its fcc crystal structure but with a substantial fraction of the C60 molecules modified with carbonyl (C=O) bonds.
Oxygen Reduction Kinetics Enhancement on a 2 Heterostructured Oxide Surface for Solid Oxide Fuel Cells
Ethan Crumlin; Eva Mutoro; Sung Jin Ahn; Gerardo Jose la O; Donovan N Leonard; Albina Y Borisevich; Michael D Biegalski; Hans M Christen; Yang Shao-Horn
Heterostructured interfaces of oxides, which can exhibit transport and reactivity characteristics remarkably different from those of bulk oxides, are interesting systems to explore in search of highly active cathodes for the oxygen reduction reaction (ORR). Here, we show that the ORR of 85 nm thick La{sub 0.8}Sr{sub 0.2}CoO{sub 3-} (LSC) films prepared by pulsed laser deposition on (001)-oriented yttria-stabilized zirconia
Low oxygen tension inhibits osteogenic differentiation and enhances stemness of human MIAMI cells
Gianluca D'Ippolito; Sylma Diabira; Guy A. Howard; Bernard A. Roos; Paul C. Schiller
We recently reported the isolation of a unique subpopulation of human stromal cells from bone marrow (BM) termed marrow-isolated adult multilineage inducible (MIAMI) cells, capable of differentiating in vitro into mature-like cells from all three germ layers. The oxygen tension (pO2) in BM ranges from 1 to 7%, which prompted us to examine the role of pO2 in regulating the
Computational and experimental study of oxygen-enhanced axisymmetric laminar methane flames
Beth Anne V. Bennett; Zhongxian Cheng; Robert W. Pitz; Mitchell D. Smooke
Three axisymmetric laminar coflow diffusion flames, one of which is a nitrogen-diluted methane\\/air flame (the Ĺbase caseĺ) and the other two of which consist of nitrogen-diluted methane vs. pure oxygen, are examined both computationally and experimentally. Computationally, the local rectangular refinement method is used to solve the fully coupled nonlinear conservation equations on solution-adaptive grids. The model includes C2 chemistry
Reduced No.sub.x combustion method
Delano, Mark A. (Briarcliff Manor, NY)
A combustion method enabling reduced NO.sub.x formation wherein fuel and oxidant are separately injected into a combustion zone in a defined velocity relation, combustion gases are aspirated into the oxidant stream prior to intermixture with the fuel, and the fuel is maintained free from contact with oxygen until the intermixture.
Combustion enhancement and pollutant control research with acoustically induced mixing. Technical progress report, March-June, 1981
Faeser, R.J.; Rudnicki, M.I.
An experimental research program has been initiated to evaluate the possibility that beneficial effects can result when acoustic energy is impressed on the combustion zone of pulverized coal furnaces. These benefits include the reduction in NO/sub x/ generation, the increase in combustion intensity, and the increase in turndown ratio (maximum flow/minimum flow). The postulated reason for these possible benefits is the fine stirring action of high frequency acoustic waves. The first three-month period of this program was devoted to the formulation of a test plan, the design of the 5 lb/hr coal rate combustor with acoustic driver attachments, and the specification of the test facility.
Ames Hybrid Combustion Facility
NASA Technical Reports Server (NTRS)
Zilliac, Greg; Karabeyoglu, Mustafa A.; Cantwell, Brian; Hunt, Rusty; DeZilwa, Shane; Shoffstall, Mike; Soderman, Paul T.; Bencze, Daniel P. (Technical Monitor)
The report summarizes the design, fabrication, safety features, environmental impact, and operation of the Ames Hybrid-Fuel Combustion Facility (HCF). The facility is used in conducting research into the scalability and combustion processes of advanced paraffin-based hybrid fuels for the purpose of assessing their applicability to practical rocket systems. The facility was designed to deliver gaseous oxygen at rates between 0.5 and 16.0 kg/sec to a combustion chamber operating at pressures ranging from 300 to 900. The required run times were of the order of 10 to 20 sec. The facility proved to be robust and reliable and has been used to generate a database of regression-rate measurements of paraffin at oxygen mass flux levels comparable to those of moderate-sized hybrid rocket motors.
Hyperbaric oxygenation enhances transplanted cell graft and functional recovery in the infarct heart
Khan, Mahmood; Meduru, Sarath; Mohan, Iyyapu K.; Kuppusamy, M. Lakshmi; Wisel, Sheik; Kulkarni, Aditi; Rivera, Brian K.; Hamlin, Robert L.; Kuppusamy, Periannan
A major limitation to the application of stem-cell therapy to repair ischemic heart damage is the low survival of transplanted cells in the heart, possibly due to poor oxygenation. We hypothesized that hyperbaric oxygenation (HBO) can be used as an adjuvant treatment to augment stem-cell therapy. Therefore, the goal of this study was to evaluate the effect of HBO on the engraftment of rat bone-marrow-derived mesenchymal stem cells (MSCs) transplanted in infarct rat hearts. Myocardial infarction (MI) was induced in Fisher-344 rats by permanently ligating the left-anterior-descending coronary artery. MSCs, labeled with fluorescent superparamagnetic iron oxide (SPIO) particles, were transplanted in the infarct and peri-infarct regions of the MI hearts. HBO (100% oxygen at 2 ATA for 90 min) was administered daily for 2 weeks. Four MI groups were used: untreated (MI); HBO; MSC; MSC+HBO. Echocardiography, electro-vectorcardiography, and magnetic resonance imaging were used for functional evaluations. The engraftment of transplanted MSCs in the heart was confirmed by SPIO fluorescence and Prussian-blue staining. Immunohistochemical staining was used to identify key cellular and molecular markers including CD29, troponin-T, connexin-43, VEGF, ?-smooth-muscle actin, and von-Willebrand factor in the tissue. Compared to MI and MSC groups, the MSC+HBO group showed a significantly increased recovery of cardiac function including left-ventricular (LV) ejection fraction, fraction-shortening, LV wall-thickness, and QRS vector. Further, HBO treatment significantly increased the engraftment of CD29-positive cells, expression of connexin-43, troponin-T and VEGF, and angiogenesis in the infarct tissue. Thus, HBO appears to be a potential and clinically-viable adjuvant treatment for myocardial stem-cell therapy. PMID:19376124
Evidence for enhanced phosphorus regeneration from marine sediments overlain by oxygen depleted waters
Ingall, E.; Jahnki, R. [Skidaway Institute of Oceanography, Savannah, GA (United States)] [Skidaway Institute of Oceanography, Savannah, GA (United States)
Phosphorus regeneration and burial fluxes determined from in situ benthic flux chamber and solid phase measurements at sites on the Californian continental margin, Peruvian continental slope, North Carolina continental slope, and from the Santa Monica basin, California are reported. Comparison of these sites indicates that O{sub 2}-depleted bottomwaters enhance P regeneration from sediments, diminishing overall phosphorus burial efficiency. Based on these observations, a positive feedback, linking ocean anoxia, enhanced benthic phosphorus regeneration, and marine productivity is proposed. On shorter timescales, these results also suggest that O{sub 2} depletion in coastal regions caused by eutrophication may enhance P regeneration from sediments, thereby providing additional P necessary for increased biological productivity. 42 refs., 2 figs., 2 tabs.
Engineering the oxygen sensing regulation results in an enhanced recombinant human hemoglobin production by Saccharomyces cerevisiae.
MartÝnez, JosÚ L; Liu, Lifang; Petranovic, Dina; Nielsen, Jens
Efficient production of appropriate oxygen carriers for transfusions (blood substitutes or artificial blood) has been pursued for many decades, and to date several strategies have been used, from synthetic polymers to cell-free hemoglobin carriers. The recent advances in the field of metabolic engineering also allowed the generation of different genetically modified organisms for the production of recombinant human hemoglobin. Several studies have showed very promising results using the bacterium Escherichia coli as a production platform, reporting hemoglobin titers above 5% of the total cell protein content. However, there are still certain limitations regarding the protein stability and functionality of the recombinant hemoglobin produced in bacterial systems. In order to overcome these limitations, yeast systems have been proposed as the eukaryal alternative. We recently reported the generation of a set of plasmids to produce functional human hemoglobin in Saccharomyces cerevisiae, with final titers of active hemoglobin exceeding 4% of the total cell protein. In this study, we propose a strategy for further engineering S. cerevisiae by altering the oxygen sensing pathway by deleting the transcription factor HAP1, which resulted in an increase of the final recombinant active hemoglobin titer exceeding 7% of the total cellular protein. PMID:25082441
Leaching of mercury and other constituents of potential concern during land disposal or beneficial use of coal combustion residues (CCRs) is the environmental impact pathway evaluated in this report. The specific objectives of the research was to: (1) evaluate mercury, arsenic an...
Enhanced performance of an electric oxygen-iodine laser D. L. Carrolla
Carroll, David L.
. This continuous wave (cw) laser operating on the 1315 nm transition of atomic iodine is pumped by the production led to improvements in O2(a) production and efficiency. A 95% enhancement in cw laser power demonstration of gain and lasing from an air- helium discharge [Woodard, 2008a]. Computational modeling
Environmental enhancement of creep crack growth in Inconel 718 by oxygen and water vapor
P. Valerio; M. Gao; R. P. Wei
Inconel 718 alloy is widely used in high temperature applications. Because of its sensitivity to environmentally enhanced crack growth at high temperatures, its use has been limited to modest temperatures (i.e., below 973 K). To improve its performance and to better predict its service life, it is important to develop a better understanding of the processes of crack growth at
Low dose gamma irradiation enhances defined signaling components of intercellular reactive oxygen-mediated apoptosis induction
NASA Astrophysics Data System (ADS)
Bauer, G.
Transformed cells are selectively removed by intercellular ROS-mediated induction of apoptosis. Signaling is based on the HOCl and the NO/peroxynitrite pathway (major pathways) and the nitryl chloride and the metal-catalyzed Haber-Weiss pathway (minor pathways). During tumor progression, resistance against intercellular induction of apoptosis is acquired through expression of membrane-associated catalase. Low dose radiation of nontransformed cells has been shown to enhance intercellular induction of apoptosis. The present study was performed to define the signaling components which are modulated by low dose gamma irradiation. Low dose radiation induced the release of peroxidase from nontransformed, transformed and tumor cells. Extracellular superoxide anion generation was strongly enhanced in the case of transformed cells and tumor cells, but not in nontransformed cells. Enhancement of peroxidase release and superoxide anion generation either increased intercellular induction of apoptosis of transformed cells, or caused a partial protection under specific signaling conditions. In tumor cells, low dose radiation enhanced the production of major signaling components, but this had no effect on apoptosis induction, due to the strong resistance mechanism of tumor cells. Our data specify the nature of low dose radiation-induced effects on specific signaling components of intercellular induction of apoptosis at defined stages of multistep carcinogenesis.
Soft-Templating Synthesis of N-Doped Mesoporous Carbon Nanospheres for Enhanced Oxygen Reduction Reaction.
Bayatsarmadi, Bita; Zheng, Yao; Jaroniec, Mietek; Qiao, Shi Zhang
The development of ordered mesoporous carbon materials with controllable structures and improved physicochemical properties by doping heteroatoms such as nitrogen into the carbon framework has attracted a lot of attention, especially in relation to energy storage and conversion. Herein, a series of nitrogen-doped mesoporous carbon spheres (NMCs) was synthesized via a facile dual soft-templating procedure by tuning the nitrogen content and carbonization temperature. Various physical and (electro)chemical properties of the NMCs have been comprehensively investigated to pave the way for a feasible design of nitrogen-containing porous carbon materials. The optimized sample showed a favorable electrocatalytic activity as evidenced by a high kinetic current and positive onset potential for oxygen reduction reaction (ORR) due to its large surface area, high pore volume, good conductivity, and high nitrogen content, which make it a highly efficient ORR metal-free catalyst in alkaline solutions. PMID:25891306
Enhanced Surfactant Adsorption on Activated Carbon through Manipulation of Surface Oxygen Groups
NASA Astrophysics Data System (ADS)
Collins, John; Qu, Deyang; Foster, Michelle
Passive energy storage is a necessary component for balancing the lifecycle budget with new forms of green energy. The work presented describes how surface oxygen groups (SOG) on granulated activated carbon have been manipulated using Nitric Acid in a controlled, stepwise fashion. The structure and surface functionality of the activated carbon samples were characterized using DRIFTS, Raman Spectroscopy and Porosimetry. Total surface area was found to increase proportionally with the removal of heteroatom material, exposing previously insulated active sites responsible for SOG attachment. Broad oxide peaks were deconvoluted and analyzed, allowing for absolute identification of evolving functionality at each oxidation stage. SOGs were maximized on the third oxidation cycle with the presence of conjugated aromatic, phenol, lactone, and carboxylic acid groups. FSN Zonyl nonionic was applied to all oxidized samples at various concentrations. Total adsorbed surfactant was quantified for each concentration / oxidation scheme using attenuated total reflection. The relative quantity and polarity of chemisorbed surfactant were qualitatively assessed for each equilibrium concentration.
The oxycoal process with cryogenic oxygen supply
NASA Astrophysics Data System (ADS)
Kather, Alfons; Scheffknecht, GŘnter
Due to its large reserves, coal is expected to continue to play an important role in the future. However, specific and absolute CO2 emissions are among the highest when burning coal for power generation. Therefore, the capture of CO2 from power plants may contribute significantly in reducing global CO2 emissions. This review deals with the oxyfuel process, where pure oxygen is used for burning coal, resulting in a flue gas with high CO2 concentrations. After further conditioning, the highly concentrated CO2 is compressed and transported in the liquid state to, for example, geological storages. The enormous oxygen demand is generated in an air-separation unit by a cryogenic process, which is the only available state-of-the-art technology. The generation of oxygen and the purification and liquefaction of the CO2-enriched flue gas consumes significant auxiliary power. Therefore, the overall net efficiency is expected to be lowered by 8 to 12 percentage points, corresponding to a 21 to 36% increase in fuel consumption. Oxygen combustion is associated with higher temperatures compared with conventional air combustion. Both the fuel properties as well as limitations of steam and metal temperatures of the various heat exchanger sections of the steam generator require a moderation of the temperatures during combustion and in the subsequent heat-transfer sections. This is done by means of flue gas recirculation. The interdependencies among fuel properties, the amount and the temperature of the recycled flue gas, and the resulting oxygen concentration in the combustion atmosphere are investigated. Expected effects of the modified flue gas composition in comparison with the air-fired case are studied theoretically and experimentally. The different atmosphere resulting from oxygen-fired combustion gives rise to various questions related to firing, in particular, with regard to the combustion mechanism, pollutant reduction, the risk of corrosion, and the properties of the fly ash or the deposits that form. In particular, detailed nitrogen and sulphur chemistry was investigated by combustion tests in a laboratory-scale facility. Oxidant staging, in order to reduce NO formation, turned out to work with similar effectiveness as for conventional air combustion. With regard to sulphur, a considerable increase in the SO2 concentration was found, as expected. However, the H2S concentration in the combustion atmosphere increased as well. Further results were achieved with a pilot-scale test facility, where acid dew points were measured and deposition probes were exposed to the combustion environment. Besides CO2 and water vapour, the flue gas contains impurities like sulphur species, nitrogen oxides, argon, nitrogen, and oxygen. The CO2 liquefaction is strongly affected by these impurities in terms of the auxiliary power requirement and the CO2 capture rate. Furthermore, the impurity of the liquefied CO2 is affected as well. Since the requirements on the liquid CO2 with regard to geological storage or enhanced oil recovery are currently undefined, the effects of possible flue gas treatment and the design of the liquefaction plant are studied over a wide range.
The oxycoal process with cryogenic oxygen supply.
Kather, Alfons; Scheffknecht, GŘnter
Due to its large reserves, coal is expected to continue to play an important role in the future. However, specific and absolute CO2 emissions are among the highest when burning coal for power generation. Therefore, the capture of CO2 from power plants may contribute significantly in reducing global CO2 emissions. This review deals with the oxyfuel process, where pure oxygen is used for burning coal, resulting in a flue gas with high CO2 concentrations. After further conditioning, the highly concentrated CO2 is compressed and transported in the liquid state to, for example, geological storages. The enormous oxygen demand is generated in an air-separation unit by a cryogenic process, which is the only available state-of-the-art technology. The generation of oxygen and the purification and liquefaction of the CO2-enriched flue gas consumes significant auxiliary power. Therefore, the overall net efficiency is expected to be lowered by 8 to 12 percentage points, corresponding to a 21 to 36% increase in fuel consumption. Oxygen combustion is associated with higher temperatures compared with conventional air combustion. Both the fuel properties as well as limitations of steam and metal temperatures of the various heat exchanger sections of the steam generator require a moderation of the temperatures during combustion and in the subsequent heat-transfer sections. This is done by means of flue gas recirculation. The interdependencies among fuel properties, the amount and the temperature of the recycled flue gas, and the resulting oxygen concentration in the combustion atmosphere are investigated. Expected effects of the modified flue gas composition in comparison with the air-fired case are studied theoretically and experimentally. The different atmosphere resulting from oxygen-fired combustion gives rise to various questions related to firing, in particular, with regard to the combustion mechanism, pollutant reduction, the risk of corrosion, and the properties of the fly ash or the deposits that form. In particular, detailed nitrogen and sulphur chemistry was investigated by combustion tests in a laboratory-scale facility. Oxidant staging, in order to reduce NO formation, turned out to work with similar effectiveness as for conventional air combustion. With regard to sulphur, a considerable increase in the SO2 concentration was found, as expected. However, the H2S concentration in the combustion atmosphere increased as well. Further results were achieved with a pilot-scale test facility, where acid dew points were measured and deposition probes were exposed to the combustion environment. Besides CO2 and water vapour, the flue gas contains impurities like sulphur species, nitrogen oxides, argon, nitrogen, and oxygen. The CO2 liquefaction is strongly affected by these impurities in terms of the auxiliary power requirement and the CO2 capture rate. Furthermore, the impurity of the liquefied CO2 is affected as well. Since the requirements on the liquid CO2 with regard to geological storage or enhanced oil recovery are currently undefined, the effects of possible flue gas treatment and the design of the liquefaction plant are studied over a wide range. PMID:19495717
Redox cycling by motexafin gadolinium enhances cellular response to ionizing radiation by forming reactive oxygen species
Darren Magda; Cheryl Lepp; Nikolay Gerasimchuk; Intae Lee; Jonathan L Sessler; Alice Lin; John E Biaglow; Richard A Miller
Purpose: To examine the mechanism of radiation enhancement by motexafin gadolinium (Gd-Tex) in vitro.Methods and Materials: Oxidation of ascorbate and NADPH by Gd-Tex was evaluated in a neutral buffer. Growth inhibition of human uterine cancer cell line MES-SA was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) dye. Clonogenic assays were used to measure radiation response in MES-SA, A549 human lung carcinoma, E89,
High thermal sensitivity of blood enhances oxygen delivery in the high-flying bar-headed goose.
Meir, Jessica U; Milsom, William K
The bar-headed goose (Anser indicus) crosses the Himalaya twice a year at altitudes where oxygen (O2) levels are less than half those at sea level and temperatures are below -20░C. Although it has been known for over three decades that the major hemoglobin (Hb) component of bar-headed geese has an increased affinity for O2, enhancing O2 uptake, the effects of temperature and interactions between temperature and pH on bar-headed goose Hb-O2 affinity have not previously been determined. An increase in breathing of the hypoxic and extremely cold air experienced by a bar-headed goose at altitude (due to the enhanced hypoxic ventilatory response in this species) could result in both reduced temperature and reduced levels of CO2 at the blood-gas interface in the lungs, enhancing O2 loading. In addition, given the strenuous nature of flapping flight, particularly in thin air, blood leaving the exercising muscle should be warm and acidotic, facilitating O2 unloading. To explore the possibility that features of blood biochemistry in this species could further enhance O2 delivery, we determined the P50 (the partial pressure of O2 at which Hb is 50% saturated) of whole blood from bar-headed geese under conditions of varying temperature and [CO2]. We found that blood-O2 affinity was highly temperature sensitive in bar-headed geese compared with other birds and mammals. Based on our analysis, temperature and pH effects acting on blood-O2 affinity (cold alkalotic lungs and warm acidotic muscle) could increase O2 delivery by twofold during sustained flapping flight at high altitudes compared with what would be delivered by blood at constant temperature and pH. PMID:23470665
Study of electrostatic modulation of fuel sprays to enhance combustion performance in an aviation gas turbine. Master's thesis
Manning, W.W.
The influence of electrostatic and electrohydrodynamic charging on hydrocarbon fuel-spray patterns and droplet atomization was investigated. Research was performed in a combustion environment with an Allison T-56 combustor liner and an unmodified pressure-jet atomizer fuel nozzle. High-voltage probes and a variable-geometry probe-insertion device were developed to assess the effectiveness of probe type and location on fuel-spray modification and modulation. Exhaust-gas temperatures and temperature profiles were measured to determine changes in the combustor's thermal profile and combustion efficiency. JP-4, JET-A and Number-2 Diesel fuels were tested to analyze electrically-assisted atomization effectiveness relative to off-design fuel performance.
Combustion enhancement and pollutant-control research with acoustically induced mixing. Technical progress report, June-September 1981
Faeser, R.J.; Rudnicki, M.I.
An experimental research program has been initiated to evaluate the possibility that beneficial effects can result when acoustic energy is impressed on the combustion zone of pulverized coal furnaces. These benefits include the reduction in NO/sub x/ generation, the increase in combustion intensity, and the increase in turndown ratio (maximum flow/minimum flow). The postulated reason for these possible benefits is the increased relative motion of the gas and coal particles and the fine stirring action resulting from high frequency acoustic waves. During the second, three-month period of this contract, the design and fabrication of the combustor were completed and the test facility buildup was 70% completed. A checkout test of the acoustic equipment and a preliminary acoustic survey test of the combustor response were also completed.
Potential utility of hyperbaric oxygen therapy and propolis in enhancing the leishmanicidal activity of glucantime.
Ayres, Diana Copi; Fedele, Thiago Antonio; Marcucci, Maria Cristina; Giorgio, Selma
In this study we investigated the efficacy of hyperbaric oxygen (HBO) therapy, alone or combined with the pentavalent antimonial glucantime on Leishmania amazonensis infection. In parallel, the effect of Brazilian red propolis gel (propain) alone or combined with glucantime on L. amazonensis infection was evaluated. The inhibition of the infection in macrophages treated with glucantime in combination with HBO exposition was greater than that of macrophages treated with glucantime alone or HBO alone. The susceptible mouse strain BALB/c infected in the shaved rump with L. amazonensis treated with glucantime and exposed to HBO showed: time points in the course of the disease in which lesions were smaller than those of mice treated with glucantime alone and revascularization of the skin in the lesion site; interferon-gamma (IFN-g) levels were not elevated in lymph node cells from these animals. Propain alone was not efficient against lesions, although less exudative lesions were observed in animals treated with propain alone or combined with glucantime. These results reveal the potential value of HBO and red propolis in combination with glucantime for treating cutaneous leishmaniasis and encourage further studies on the effect of more aggressive HBO, propolis and glucantime therapies on different mouse models of leishmaniasis. PMID:22183457
Construction of a reusable, high-fidelity model to enhance extracorporeal membrane oxygenation training through simulation.
Thompson, Jess L; Grisham, Lisa M; Scott, Jeanne; Mogan, Chris; Prescher, Hannes; Biffar, David; Jarred, John; Meyer, Robyn J; Hamilton, Allan J
Initiation of extracorporeal membrane oxygenation (ECMO) is stressful, especially for inexperienced extracorporeal life support providers. The main objective of this study was to create a novel, reusable mannequin for high-fidelity simulation of ECMO initiation. We modified a Laerdal neonatal mannequin (SimNewB; Stavanger, Norway) so that it could be used to simulate an ECMO initiation. A simulation of a neonatal patient suffering from meconium aspiration was performed in the pediatric intensive care unit, and participants included new extracorporeal life support specialists in addition to the composition of the clinical ECMO team. A total of 17 individuals participated in the neonatal ECMO initiation simulation. Questionnaire results showed that 88% of participants felt better prepared to assist in an ECMO initiation after the simulation. All participants (100%) agreed that the modified mannequin and the environment were realistic and that this simulation helps teamwork and communication in future initiations of ECMO. Simulation can be used for the prevention, identification, and reduction of anxiety-related crisis situations that novice providers may infrequently encounter during routine clinical use of mechanical circulatory support. Use of a reusable, high-fidelity mannequin may be beneficial for effective team training of complex pediatric ECMO-related procedures. PMID:24675629
Phenolic extract of Dialium guineense pulp enhances reactive oxygen species detoxification in aflatoxin B? hepatocarcinogenesis.
Adeleye, Abdulwasiu O; Ajiboye, Taofeek O; Iliasu, Ganiyat A; Abdussalam, Folakemi A; Balogun, Abdulazeez; Ojewuyi, Oluwayemisi B; Yakubu, Musa T
This study investigated the effect of Dialium guineense pulp phenolic extract on aflatoxin B1 (AFB1)-induced oxidative imbalance in rat liver. Reactive oxygen species (ROS) scavenging potentials of free and bound phenolic extract of D. guineense (0.2-1.0?mg/mL) were investigated in vitro using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, superoxide ion (O2(-)), hydrogen peroxide (H2O2), hydroxyl radical, and ferric ion reducing system. In the in vivo study, 35 animals were randomized into seven groups of five rats each. Free and bound phenolic extract (1?mg/mL) produced 66.42% and 93.08%, 57.1% and 86.0%, 62.0% and 90.05%, and 60.11% and 72.37% scavenging effect on DPPH radical, O2(-) radical, H2O2, and hydroxyl radical, while ferric ion was significantly reduced. An AFB1-mediated decrease in the activities of ROS detoxifying enzymes (superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, and glucose 6 phosphate dehydrogenase) was significantly attenuated (P<.05). AFB1-mediated elevation in the concentrations of oxidative stress biomarkers; malondialdehyde, conjugated dienes, lipid hydroperoxides, protein carbonyl, and percentage DNA fragmentation were significantly lowered by D. guineense phenolic extract (P<.05). Overall, the in vitro and in vivo effects suggest that D. guineense phenolic extract elicited ROS scavenging and detoxification potentials, as well as the capability of preventing lipid peroxidation, protein oxidation, and DNA fragmentation. PMID:24892362
Enhancement of oxygen vacancies and solar photocatalytic activity of zinc oxide by incorporation of nonmetal
NASA Astrophysics Data System (ADS)
Patil, Ashokrao B.; Patil, Kashinath R.; Pardeshi, Satish K.
B-doped ZnO and N-doped ZnO powders have been synthesized by mechanochemical method and characterized by TG-DTA, XRD, SEM-EDX, XPS, UV-visible and photoluminescence (PL) spectra. X-ray diffraction data suggests the hexagonal wurtzite structure for modified ZnO crystallites and the incorporation of nonmetal expands the lattice constants of ZnO. The room temperature PL spectra suggest more number of oxygen vacancies exist in nonmetal-doped ZnO than that of undoped zinc oxide. XPS analysis shows the substitution of some of the O atoms of ZnO by nonmetal atoms. Solar photocatalytic activity of B-doped ZnO, N-doped ZnO and undoped ZnO was compared by means of oxidative photocatalytic degradation (PCD) of Bisphenol A (BPA). B-doped ZnO showed better solar PCD efficiency as compare to N-doped ZnO and undoped ZnO. The PCD of BPA follows first order reaction kinetics. The detail mechanism of PCD of Bisphenol A was proposed with the identification of intermediates such as hydroquinone, benzene-1,2,4-triol and 4-(2-hydroxypropan-2-yl) phenol.
The effect of hyperbaric oxygen in the enhancement of healing in selected problem wounds.
Warriner, Robert A; Hopf, Harriet W
Problem wounds represent a significant and growing challenge to our healthcare system. The incidence and prevalence of these wounds are increasing in the population, resulting in growing utilization of healthcare resources and dollars expended. Venous leg ulcers represent the most common lower-extremity wound seen in ambulatory wound care centers, with recurrences frequent and outcomes often less than satisfactory. Pressure ulcers are common in patients in long-term institutional care settings adding significant increases in cost, disability and liability. Foot ulcers in patients with diabetes contribute to more than half of lower-extremity amputations in the United States in a group at risk, representing only 3 percent of the population. In response to this challenge, specialized programs have emerged designed to identify and manage these patients, using standardized protocols and a variety of new technologies to improve outcomes. Hyperbaric oxygen treatment (HBO2T) has been increasingly utilized in an adjunctive role in the care of many of these patients, coinciding with optimized patient and local wound care. PMID:23045921
A biofilm enhanced miniature microbial fuel cell using Shewanella oneidensis DSP10 and oxygen reduction cathodes.
Biffinger, Justin C; Pietron, Jeremy; Ray, Ricky; Little, Brenda; Ringeisen, Bradley R
A miniature-microbial fuel cell (mini-MFC, chamber volume: 1.2 mL) was used to monitor biofilm development from a pure culture of Shewanella oneidensis DSP10 on graphite felt (GF) under minimal nutrient conditions. ESEM evidence of biofilm formation on GF is supported by substantial power density (per device cross-section) from the mini-MFC when using an acellular minimal media anolyte (1500 mW/m2). These experiments demonstrate that power density per volume for a biofilm flow reactor MFC should be calculated using the anode chamber volume alone (250W/m3), rather than with the full anolyte volume. Two oxygen reduction cathodes (uncoated GF or a Pt/vulcanized carbon coating on GF) were also compared to a cathode using uncoated GF and a 50mM ferricyanide catholyte solution. The Pt/C-GF (2-4% Pt by mass) electrodes with liquid cultures of DSP10 produced one order of magnitude larger power density (150W/m3) than bare graphite felt (12W/m3) in this design. These advances are some of the required modifications to enable the mini-MFC to be used in real-time, long-term environmental power generating situations. PMID:16939710
Polydopamine-graphene oxide derived mesoporous carbon nanosheets for enhanced oxygen reduction.
Qu, Konggang; Zheng, Yao; Dai, Sheng; Qiao, Shi Zhang
Composite materials combining nitrogen-doped carbon (NC) with active species represent a paramount breakthrough as alternative catalysts to Pt for the oxygen reduction reaction (ORR) due to their competitive activity, low cost and excellent stability. In this paper, a simple strategy is presented to construct graphene oxide-polydopamine (GD) based carbon nanosheets. This approach does not need to modify graphene and use any catalyst for polymerization under ambient conditions, and the obtained carbon nanosheets possess adjustable thicknesses and uniform mesoporous structures without using any template. The thickness of GD hybrids and the carbonization temperature are found to play crucial roles in adjusting the microstructure of the resulting carbon nanosheets and, accordingly their ORR catalytic activity. The optimized carbon nanosheet generated by a GD hybrid of 5 nm thickness after 900 ░C carbonization exhibits superior ORR activity with an onset potential of -0.07 V and a kinetic current density of 13.7 mA cm(-2) at -0.6 V. The unique mesoporous structure, high surface areas, abundant defects and favorable nitrogen species are believed to significantly benefit the ORR catalytic process. Furthermore, it also shows remarkable durability and excellent methanol tolerance outperforming those of commercial Pt/C. In view of the physicochemical versatility and structural tunability of polydopamine (PDA) materials, our work would shed new light on the understanding and further development of PDA-based carbon materials for highly efficient electrocatalysts. PMID:26147787
Enhanced nitrogen removal in constructed wetlands: effects of dissolved oxygen and step-feeding.
Li, Fengmin; Lu, Lun; Zheng, Xiang; Ngo, Huu Hao; Liang, Shuang; Guo, Wenshan; Zhang, Xiuwen
Four horizontal subsurface flow constructed wetlands (HSFCWs), named HSFCW1 (three-stage, without step-feeding), HSFCW2 (three-stage, with step-feeding), HSFCW3 (five-stage, without step-feeding) and HSFCW4 (five-stage, with step-feeding) were designed to investigate the effects of dissolved oxygen (DO) and step-feeding on nitrogen removal. High removal of 90.9% COD, 99.1% ammonium nitrogen and 88.1% total nitrogen (TN) were obtained simultaneously in HSFCW4 compared with HSFCW1-3. The excellent TN removal of HSFCW4 was due to artificial aeration provided sufficient DO for nitrification and the favorable anoxic environment created for denitrification. Step-feeding was a crucial factor because it provided sufficient carbon source (high COD: nitrate ratio of 14.3) for the denitrification process. Microbial activities and microbial abundance in HSFCW4 was found to be influenced by DO distribution and step-feeding, and thus improve TN removal. These results suggest that artificial aeration combined with step-feeding could achieve high nitrogen removal in HSFCWs. PMID:25069093
Dynamic Quenching of Porphyrin Triplet States by Two-Photon Absorbing Dyes: Towards Two-Photon-Enhanced Oxygen Nanosensors
Finikova, Olga S.; Chen, Ping; Ou, Zhongping; Kadish, Karl M.; Vinogradov, Sergei A.
Two-photon-enhanced dendritic nanoprobes are being developed for two-photon (2P) laser scanning microscopy of oxygen [1]. In these molecular constructs, phosphorescence of metalloporphyrins is coupled to two-photon absorption (2PA) of electronically separate antenna dyes via intramolecular F÷rster-type resonance energy transfer (FRET). In the originally developed probes, competing electron transfer (ET) between the antennae and the long-lived triplet states of metalloporphyrins partially quenched the phosphorescence, reducing the probe's sensitivity and dynamic range. The rate of such ET can be reduced by tuning the redox potentials of the chromophores. In order to identify the optimal metalloporphyrin-2P antenna pairs, we performed screening of several phosphorescent Pt porphyrins (FRET acceptors) and 2P dyes (FRET donors) using dynamic quenching of phosphorescence. Phosphorescence lifetimes of Pt porphyrins were measured as a function of the dye concentration in organic solutions. The obtained Stern-Volmer quenching constants were correlated with the corresponding ET driving forces (?GET), calculated using the Rehm-Weller equation. FRET-pairs with minimal quenching rates were identified. The developed approach allows convenient screening of candidate-compounds for covalent assembly of 2P-enhanced triplet nanodevices. Systematic electrochemical measurements in a series of Pt porphyrins with varying peripheral substitution and conjugation pathways are presented. PMID:19030124
Sensitive determination of reactive oxygen species in cigarette smoke using microchip electrophoresis-localized surface plasmon resonance enhanced fluorescence detection.
Wang, Huai-Song; Xiao, Fang-Nan; Li, Zhong-Qiu; Ouyang, Jun; Wu, Zeng-Qiang; Xia, Xing-Hua; Zhou, Guo-Jun
A sensitive approach to the determination of reactive oxygen species (ROS) in puffs of cigarette smoke (CS) has been developed. The experimental system consists of a microfluidic chip electrophoresis and a laser induced fluorescence (LIF) device enhanced by localized surface plasmon resonance. Core-shell Ag@SiO2 nanoparticles were prepared and then immobilized on the surface of the microchannel to increase the fluorescence intensity based on localized surface plasmon resonance-enhanced fluorescence (LSPREF) effect. The ROS in puffs of CS were trapped via the oxidation of 2',7'-dichlorodihydrofluorescein (DCHF) that had been loaded on polyacrylonitrile (PAN) nanofibers in a micro-column. Determination of ROS was based on the amount of 2',7'-dichlorofluorescein (DCF), which is the sole product from DCHF oxidation. With the optimization of the trapping efficiency, we detected about 8.0 pmol of ROS per puff in the mainstream CS. This microchip electrophoresis-SPREF system enables sensitive quantitation of ROS in CS with low consumption of reagent, material, and analysis time. PMID:24458305
Mechanism of Enhanced Superoxide Production in the Cytochrome b6f Complex of Oxygenic Photosynthesis
Baniulis, Danas; Hasan, S. Saif; Stofleth, Jason T.; Cramer, William A.
The specific rate of superoxide (O2?) production in purified active crystallizable cytochrome b6f complex, normalized to the rate of electron transport, has been found to be an order of magnitude greater than that measured in isolated yeast respiratory bc1 complex. The biochemical and structural basis for the enhanced production of O2? in the cytochrome b6f compared to the bc1 complex is discussed. The larger rate of superoxide production in the b6f complex could be a consequence of an increased residence time of plastosemiquinone/plastoquinol in its binding niche near the Rieske protein iron-sulfur cluster, resulting from (i) occlusion of the quinone portal by the phytyl chain of the unique bound chlorophyll, (ii) an altered environment of the proton-accepting glutamate believed to be a proton acceptor from semiquinone, or (iii) a more negative redox potential of the heme bp on the electrochemically positive side of the complex. The enhanced rate of superoxide production in the b6f complex is physiologically significant as chloroplast-generated ROS functions in the regulation of excess excitation energy, is a source of oxidative damage inflicted during photosynthetic reactions, and is a major source of ROS in plant cells. Altered levels of ROS production are believed to convey redox signaling from the organelle to the cytosol and nucleus. PMID:24298890
Role of metal components in PdľCu bimetallic catalysts supported on CeO 2 for the oxygen-enhanced water gas shift
Junichiro Kugai; Jeffrey T. Miller; Neng Guo; Chunshan Song
Catalytic hydrogen production and CO removal in a post-reforming process are critical for low-temperature fuel cell applications. The present study aims at clarifying the role of metal components in bimetallic catalysts for oxygen-enhanced water gas shift (OWGS), wherein a small amount of O2 is added to H2-rich reformate gas to enhance CO shift. Among CeO2-supported bimetallic catalysts, PdľCu and PtľCu
Rapid enhancement of energetic oxygen ions in the inner magnetosphere during substorms
NASA Astrophysics Data System (ADS)
Nakayama, Y.; Ebihara, Y.; Tanaka, T.
Satellite observations show that energetic (>100 keV) O+ ions are rapidly increased in the inner magnetosphere during substorms. The ultimate source of O+ ions is the Earth's ionosphere, so that O+ ions must be accelerated from ~eV to 100s keV somewhere in the magnetosphere. A fundamental question still arise regarding why O+ ions are accelerated and transported to the inner magnetosphere. We simulated substorms under two different solar wind conditions by using the global MHD simulation developed by Tanaka et al. (2010, JGR). The solar wind speed is set to be 372 km/s for Case I, and 500 km/s for Case II. In both cases, the MHD simulation result shows that the dawn to dusk electric field is enhanced in the night side tail region at >7 Re just after the substorm onset. In particular, the electric field in the inner region (~7 Re) is highly enhanced by the tension force because of relatively strong magnetic field together with curved field lines. The strongest electric field takes place near the region where the plasma pressure is high. We performed test particle simulation under the electric and magnetic fields for Cases I and II. O+ ions are released from two planes located at ▒2 Re in the Z direction in the tail region. O+ ions released at the two planes represent outflowing stream of O+ ions escaping from the Earth. The distribution function at the planes is assumed to be drifting Kappa distribution with temperature of 10 eV, the density of 105 m-3, and the parallel velocity given by the MHD simulation. In total, around a billion of particles are traced. Each test particle carries the real number of particles in accordance with the Liouville theorem. After tracing particles, we reconstructed 6-dimensional phase space density of O+ ions. We obtained the following results. (1) Just after substorm onset, the differential flux of O+ ions is almost simultaneously enhanced in the region where the electric field is strong. (2) The kinetic energy increases rapidly to 120 keV for Case I, and 200 keV Case II in the inner magnetosphere. (3) On the dayside, the pitch angle anisotropy of O+ ions increases with radial distance. We will discuss the acceleration processes and generation mechanisms of pitch angle anisotropy of O+ ions in more detail, and the overall contribution to the ring current.
Coal-oxygen process provides CO/sub 2/ for enhanced recovery
Abraham, B.M.; Asbury, J.G.; Lynch, E.P.; Teotia, A.P.S.
A description is given of a process which is based on the production of CO/sub 2/ in electric power plants that burn coal in an O/sub 2/-CO/sub 2/ mixture (not air). The process eliminates the need for flue gas desulfurization and carbon dioxide purification required in more conventional approaches to recovery from flue gases. It is environmentally attractive because CO/sub 2/ is not vented to the atmosphere and because, relative to flue gas recovery, the thermal efficiency of the power plant is improved. The analysis indicates that CO/sub 2/ could be delivered at economically attractive prices from sources within several hundred miles of EOR (Enhanced Oil Recovery) sites. 13 refs.
A novel strategy of enhanced glutathione production in high cell density cultivation of Candida utilisŚCysteine addition combined with dissolved oxygen controlling
Guo-Bin Liang; Guo-Cheng Du; Jian Chen
Effects of dissolved oxygen (DO) concentration on glutathione (GSH) production and cysteine oxidation were investigated in high cell density cultivation of Candida utilis. Lower DO concentration favors cysteine absorption but retards GSH production. Higher DO promotes GSH production but accelerates cysteine oxidation in the broth. A two-step DO control strategy was developed and compared for the potential in enhancing GSH
Silver/iron oxide/graphitic carbon composites as bacteriostatic catalysts for enhancing oxygen reduction in microbial fuel cells
NASA Astrophysics Data System (ADS)
Ma, Ming; You, Shijie; Gong, Xiaobo; Dai, Ying; Zou, Jinlong; Fu, Honggang
Biofilms from anode heterotrophic bacteria are inevitably formed over cathodic catalytic sites, limiting the performances of single-chamber microbial fuel cells (MFCs). Graphitic carbon (GC) - based nano silver/iron oxide (AgNPs/Fe3O4/GC) composites are prepared from waste pomelo skin and used as antibacterial oxygen reduction catalysts for MFCs. AgNPs and Fe3O4 are introduced in situ into the composites by one-step carbothermal reduction, enhancing their conductivity and catalytic activity. To investigate the effects of Fe species on the antibacterial and catalytic properties, AgNPs/Fe3O4/GC is washed with sulfuric acid (1 mol L-1) for 0.5 h, 1 h, and 5 h and marked as AgNPs/Fe3O4/GC-x (x = 0.5 h, 1 h and 5 h, respectively). A maximum power density of 1712 ▒ 35 mW m-2 is obtained by AgNPs/Fe3O4/GC-1 h, which declines by 4.12% after 17 cycles. Under catalysis of all AgNP-containing catalysts, oxygen reduction reaction (ORR) proceeds via the 4e- pathway, and no toxic effects to anode microorganisms result from inhibiting the cathodic biofilm overgrowth. With the exception of AgNPs/Fe3O4/GC-5 h, the AgNPs-containing composites exhibit remarkable power output and coulombic efficiency through lowering proton transfer resistance and air-cathode biofouling. This study provides a perspective for the practical application of MFCs using these efficient antibacterial ORR catalysts.
?-? Stacking induced enhanced molecular solubilization, singlet oxygen production, and retention of a photosensitizer loaded in thermosensitive polymeric micelles.
Shi, Yang; Elkhabaz, Ahmed; Yengej, Fjodor A Yousef; van den Dikkenberg, Joep; Hennink, Wim E; van Nostrum, Cornelus F
Cancer photodynamic therapy (PDT) by photosensitizers (PS)-loaded polymeric micelles (PM) is hampered by the tendency of PS to aggregate in PM and/or by premature release of PS in the blood circulation. In the present study, aromatic thermosensitive PM, characterized by ?-? stacking interaction, are used to encapsulate an axially solketal-substituted silicon phthalocyanine (Si(sol)2 Pc) with enhanced loading capacity, smaller size, and significantly improved retention of Si(sol)2 Pc compared with systems based on thermosensitive PM lacking aromatic groups. Interestingly, Si(sol)2 Pc is much less prone to aggregation in the aromatic PM, i.e., the amount of Si(sol)2 Pc that could be encapsulated without aggregation is 330 times higher in the aromatic PM than in the nonaromatic PM. Furthermore, Si(sol)2 Pc in the aromatic PM in a molecularly dissolved (non-aggregated) form displays three times more efficient singlet oxygen production than Si(sol)2 Pc aggregated in the non-aromatic PM. As a result, the photocytotoxicity of Si(sol)2 Pc-loaded aromatic PM to B16F10 cells is increased, compared with that of the non-aromatic PM, while no significant cytotoxicity is observed in the dark. Fluorescence-activated cell sorting (FACS) and confocal laser scanning microscopy (CLSM) analysis shows cell uptake of Si(sol)2 Pc loaded in the aromatic PM, and the Si(sol)2 Pc is taken up by the cells together with the micelles. The efficient singlet oxygen production of Si(sol)2 Pc dissolved in the aromatic PM makes it an interesting formulation for cancer PDT. PMID:25388924
Advancement in recombinant protein production using a marine oxygen carrier to enhance oxygen transfer in a CHO-S cell line.
Le Pape, Fiona; Bossard, Morgane; Dutheil, Delphine; Rousselot, Morgane; Polard, ValÚrie; FÚrec, Claude; Leize, Elisabeth; DelÚpine, Pascal; Zal, Franck
Recombinant proteins, particularly proteins used as therapeutics, are widely expressed for bioprocessing manufacturing processes. Mammalian cell lines represent the major host cells for bioproduction, according to their capacities of post-translational modifications and folding of secreted proteins. Many parameters can affect cell productivity, especially the rate of oxygen transfer. Dissolved oxygen, in high or low proportions, is a crucial parameter which can affect cell viability and thus productivity. HEMARINA has developed a new technology, commercially proposed as HEMOXCell(«), to improve cell culture at a large production scale. HEMOXCell(«) is a marine oxygen carrier having properties of high oxygen sensitivity, to be used as an oxygen additive during cell culture manufacturing. In this study, we investigated the effects of HEMOXCell(«) on the culture of the commonly used CHO-S cell line. Two main objectives were pursued: 1) cell growth rate and viability during a batch mode process, and 2) the determination of the effect of this oxygen carrier on recombinant protein production from a CHO-transfected cell line. Our results show an increase of CHO-S cellular growth at a rate of more than four-fold in culture with HEMOXCell(«). Moreover, an extension of the growth exponential phase and high cell viability were observed. All of these benefits seem to contribute to the improvement of recombinant protein production. This work underlines several applications using this marine-type oxygen carrier for large biomanufacturing. It is a promising cell culture additive according to the increasing demand for therapeutic products such as monoclonal antibodies. PMID:25961365
Chigier, N. [Carnegie Mellon Univ., Pittsburgh, PA (United States). Dept. of Mechanical Engineering
A survey is presented of the most recent developments in the field of spray combustion. Topics discussed are: physical processes of atomization; drop clusters; droplet arrays and streams; ideal sprays; cloud combustion; theoretical models of spray diffusion flames; spray diagnostic techniques; measurement of drop temperature; and spray combustion measurements. 67 refs.
G. Merker; C. Schwarz; G. Stiesch; F. Otto
The content spans from simple thermodynamics of the combustion engine to complex models for the description of the air\\/fuel mixture, ignition, combustion and pollutant formation considering the engine periphery of petrol and diesel engines. Thus the emphasis of the book is on the simulation models and how they are applicable for the development of modern combustion engines. Computers can be
High-index-contrast ridge waveguide lasers fabricated via oxygen-enhanced wet thermal oxidation
NASA Astrophysics Data System (ADS)
Liang, Di; Wang, Jusong; Hall, Douglas C.; Peake, Gregory M.; Hartmann, Quesnell
A simple, novel self-aligned deep etch plus wet thermal oxidization process is demonstrated which enables high-index-contrast (HIC) ridge waveguide (RWG) lasers fabricated in a high-efficiency, high-power AlGaAs/InAlGaAs/GaAs graded-index separate confinement heterostructure to operate with a curved half-ring resonator geometry having a bend radius as low as 10 ?m. A wet thermal oxidation process modified through addition of <1% O II to the N 2 carrier gas is shown to smooth the sidewall roughness of etched AlGaAs ridge structures 10-100 fold as the oxidation front progresses inward. The reduction of propagation scattering loss due to the reduced sidewall roughness is examined. The thermal oxide grown on the deeply-etched RWG sidewalls and base also provides electrical isolation from the contact metallization, resulting in a simplified, self-aligned process, and yields a RWG structure which effectively prevents current spreading. The thermal oxide appears to be of sufficiently high quality to passivate the etched active region surface based on a comparative analysis of straight RWG lasers of varying stripe widths (w=5 to 150 ?m) passivated with native-oxide vs. PECVD-deposited SiO II. For example, at w<15 ?m, the SiO II-insulated devices have ~2X higher threshold current densities than the native-oxide devices for comparable bar lengths. The resulting high lateral optical confinement factor at the semiconductor/oxide interface (?n=1.69) significantly enhances the laser gain and efficiency. A native-oxide-defined straight laser (w=7 ?m, L= 452 ?m) operates cw (300 K, unbonded, p-side up) with a threshold current of I th=21.5 mA (J th=679.5 A/cm2) and slope efficiency of 1.19 A/W (differential quantum efficiency = 78%) at a wavelength of ~813 nm.
Aging Enhances the Production of Reactive Oxygen Species and Bactericidal Activity in Peritoneal Macrophages by Upregulating Classical Activation Pathways
Smallwood, Heather S.; Lopez-Ferrer, Daniel; Squier, Thomas C.
Maintenance of macrophages in their basal state and their rapid activation in response to pathogen detection are central to the innate immune system, acting to limit nonspecific oxidative damage and promote pathogen killing following infection. To identify possible age-related alterations in macrophage function, we have assayed the function of peritoneal macrophages from young (3?4 months) and aged (14?15 months) Balb/c mice. In agreement with prior suggestions, we observe age-dependent increases in the extent of recruitment of macrophages into the peritoneum, as well as ex vivo functional changes involving enhanced nitric oxide production under resting conditions that contribute to a reduction in the time needed for full activation of senescent macrophages following exposure to lipopolysaccharides (LPS). Further, we observe enhanced bactericidal activity following Salmonella uptake by macrophages isolated from aged Balb/c mice in comparison with those isolated from young animals. Pathways responsible for observed phenotypic changes were interrogated using tandem mass spectrometry, which identified age-dependent increases in levels of proteins linked to immune cell pathways under basal conditions and following LPS activation. Immune pathways upregulated in macrophages isolated from aged mice include proteins critical to the formation of the immunoproteasome. Detection of these latter proteins is dramatically enhanced following LPS exposure for macrophages isolated from aged animals; in comparison, the identification of immunoproteasome subunits is insensitive to LPS exposure for macrophages isolated from young animals. Consistent with observed global changes in the proteome, quantitative proteomic measurements indicate that there are age-dependent abundance changes involving specific proteins linked to immune cell function under basal conditions. LPS exposure selectively increases the levels of many proteins involved in immune cell function in aged Balb/c mice. Collectively, these results indicate that macrophages isolated from old mice are in a preactivated state that enhances their sensitivities to LPS exposure. The hyper-responsive activation of macrophages in aged animals may act to minimize infection by general bacterial threats that arise due to age-dependent declines in adaptive immunity. However, this hypersensitivity and the associated increase in the level of formation of reactive oxygen species are likely to contribute to observed age-dependent increases in the level of oxidative damage that underlie many diseases of the elderly.
N-doped P25 TiO2-amorphous Al2O3 composites: one-step solution combustion preparation and enhanced visible-light photocatalytic activity.
Li, Fa-tang; Zhao, Ye; Hao, Ying-juan; Wang, Xiao-jing; Liu, Rui-hong; Zhao, Di-shun; Chen, Dai-mei
Nitrogen-doped Degussa P25 TiO2-amorphous Al2O3 composites were prepared via facile solution combustion. The composites were characterised using X-ray diffraction, high-resolution transmission microscopy, scanning electron microscopy, nitrogen adsorption-desorption measurements, X-ray photoelectron spectroscopy, UV-vis light-diffusion reflectance spectrometry (DRS), zeta-potential measurements, and photoluminescence spectroscopy. The DRS results showed that TiO2 and amorphous Al2O3 exhibited absorption in the UV region. However, the Al2O3/TiO2 composite exhibited visible-light absorption, which was attributed to N-doping during high-temperature combustion and to alterations in the electronic structure of Ti species induced by the addition of Al. The optimal molar ratio of TiO2 to Al2O3 was 1.5:1, and this composite exhibited a large specific surface area of 152 m2/g, surface positive charges, and enhanced photocatalytic activity. These characteristics enhanced the degradation rate of anionic methylene orange, which was 43.6 times greater than that of pure P25 TiO2. The high visible-light photocatalytic activity was attributed to synthetic effects between amorphous Al2O3 and TiO2, low recombination efficiency of photo-excited electrons and holes, N-doping, and a large specific surface area. Experiments that involved radical scavengers indicated that OH and O2- were the main reactive species. A potential photocatalytic mechanism was also proposed. PMID:23021102
Droplet Combustion Experiment movie
NASA Technical Reports Server (NTRS)
The Droplet Combustion Experiment (DCE) was designed to investigate the fundamental combustion aspects of single, isolated droplets under different pressures and ambient oxygen concentrations for a range of droplet sizes varying between 2 and 5 mm. The DCE principal investigator was Forman Williams, University of California, San Diego. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1 mission (STS-83, April 4-8 1997; the shortened mission was reflown as MSL-1R on STS-94). Advanced combustion experiments will be a part of investigations plarned for the International Space Station. (1.1 MB, 12-second MPEG, screen 320 x 240 pixels; downlinked video, higher quality not available)A still JPG composite of this movie is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300164.html.
NASA Technical Reports Server (NTRS)
The Droplet Combustion Experiment (DCE) was designed to investigate the fundamental combustion aspects of single, isolated droplets under different pressures and ambient oxygen concentrations for a range of droplet sizes varying between 2 and 5 mm. The DCE principal investigator was Forman Williams, University of California, San Diego. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). Advanced combustion experiments will be a part of investigations plarned for the International Space Station. (120KB JPEG, 655 x 736 pixels; downlinked video, higher quality not available) The MPG from which this composite was made is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300167.html.
Hydrogen peroxide enhances the oxidation of oxygenated volatile organic compounds on mineral dust particles: a case study of methacrolein.
Zhao, Yue; Huang, Dao; Huang, Liubin; Chen, Zhongming
Heterogeneous oxidation of oxygenated volatile organic compounds (OVOCs) serves as an important sink of OVOCs as well as a source of secondary organic material. However, the roles of gas phase oxidants in these reactions are poorly understood. In this work, we present the first laboratory study of the heterogeneous reactions of methacrolein (MACR) on various mineral dust particles in the presence of gaseous H2O2. It is found that the presence of gaseous H2O2 significantly promotes both the uptake and oxidation of MACR on kaolinite, ?-Al2O3, ?-Fe2O3, and TiO2, but not on CaCO3. The oxidation of MACR produces organic acids as its major low-molecular-weight product, whose yields are enhanced by a factor of 2-6 in the presence of H2O2. In addition, organic peroxides such as methyl hydroperoxide, peroxyformic acid, and peroxyacetic acid are only formed in the presence of H2O2, and the formation of methyl hydroperoxide indicates that MACR oxidation on the surface involves reaction with OH radicals. A probe reaction using salicylic acid verifies the production of OH radicals from H2O2 decomposition on kaolinite, ?-Al2O3, ?-Fe2O3, and TiO2, which rationalizes the enhanced MACR oxidation observed on these particles. The uptake coefficients of MACR on kaolinite, ?-Fe2O3, and TiO2 in the presence of H2O2 are on the order of 10(-5)-10(-4). Our results provide new insights into the formation and chemical evolution of organic species in the atmosphere. PMID:25111165
Inhibition of De Novo Ceramide Synthesis Reverses Diet-Induced Insulin Resistance and Enhances Whole-Body Oxygen Consumption
Ussher, John R.; Koves, Timothy R.; Cadete, Virgilio J.J.; Zhang, Liyan; Jaswal, Jagdip S.; Swyrd, Suzanne J.; Lopaschuk, David G.; Proctor, Spencer D.; Keung, Wendy; Muoio, Deborah M.; Lopaschuk, Gary D.
OBJECTIVE It has been proposed that skeletal muscle insulin resistance arises from the accumulation of intramyocellular lipid metabolites that impede insulin signaling, including diacylglycerol and ceramide. We determined the role of de novo ceramide synthesis in mediating muscle insulin resistance. RESEARCH DESIGN AND METHODS Mice were subjected to 12 weeks of diet-induced obesity (DIO), and then treated for 4 weeks with myriocin, an inhibitor of serine palmitoyl transferase-1 (SPT1), the rate-limiting enzyme of de novo ceramide synthesis. RESULTS After 12 weeks of DIO, C57BL/6 mice demonstrated a doubling in gastrocnemius ceramide content, which was completely reversed (141.5 ▒ 15.8 vs. 94.6 ▒ 10.2 nmol/g dry wt) via treatment with myriocin, whereas hepatic ceramide content was unaffected by DIO. Interestingly, myriocin treatment did not alter the DIO-associated increase in gastrocnemius diacyglycerol content, and the only correlation observed between lipid metabolite accumulation and glucose intolerance occurred with ceramide (R = 0.61). DIO mice treated with myriocin showed a complete reversal of glucose intolerance and insulin resistance which was associated with enhanced insulin-stimulated Akt and glycogen synthase kinase 3? phosphorylation. Furthermore, myriocin treatment also decreased intramyocellular ceramide content and prevented insulin resistance development in db/db mice. Finally, myriocin-treated DIO mice displayed enhanced oxygen consumption rates (3,041 ▒ 124 vs. 2,407 ▒ 124 ml/kg/h) versus their control counterparts. CONCLUSIONS Our results demonstrate that the intramyocellular accumulation of ceramide correlates strongly with the development of insulin resistance, and suggests that inhibition of SPT1 is a potentially promising target for the treatment of insulin resistance. PMID:20522596
Combustion processes for carbon capture
Terry F. Wall
A review of the technologies for coal-based power generation closest to commercial application involving carbon capture is presented. Carbon capture and storage (CCS) developments are primarily adaptations of conventional combustion systems, with additional unit operations such as bulk oxygen supply, CO2 capture by sorbents, CO2 compression, and storage. They use pulverized coal combustion in entrained flowŚthe dominant current technology for
Mechanism of smokeless diesel combustion with oxygenated fuels based on the dependence of the equivalence ration and temperature on soot particle formation
T Kitamura; T Ito; J Senda; H Fujimoto
The equivalence ratio ? and temperature T are well known to have a significant effect on the quality of particulate formation, such as the soot volume fraction, particle diameter and number density. The purpose of this work is to clarify the ?-T dependence of soot formation for various kinds of fuels, including paraffinic hydrocarbon, aromatic hydrocarbon and oxygenated hydrocarbon, and
Modeling of Laser-Induced Metal Combustion
Boley, C D; Rubenchik, A M
Experiments involving the interaction of a high-power laser beam with metal targets demonstrate that combustion plays an important role. This process depends on reactions within an oxide layer, together with oxygenation and removal of this layer by the wind. We present an analytical model of laser-induced combustion. The model predicts the threshold for initiation of combustion, the growth of the combustion layer with time, and the threshold for self-supported combustion. Solutions are compared with detailed numerical modeling as benchmarked by laboratory experiments.
Synergistic enhancement of nitrogen and sulfur co-doped graphene with carbon nanospheres insertion for electrocatalytic oxygen reduction reaction
Wu, Min; Xin, Huolin L.; Wang, Jie; Wu, Zexing; Wang, Deli
A nitrogen and sulfur co-doped graphene/carbon black (NSGCB) nanocomposite for the oxygen reduction reaction (ORR) was synthesized through a one-pot annealing of a precursor mixture containing graphene oxide, thiourea, and acidized carbon black (CB). The NSGCB showed excellent performance for the ORR with the onset and half-way potentials at 0.96 V and 0.81 V (vs. RHE), respectively. It is significantly improved over that of the catalysts derived from only graphene (0.90 V and 0.76 V) or carbon nanosphere (0.82 V and 0.74 V). The enhanced catalytic activity on the NSGCB electrode could be attributed to the synergistic effect of N/Smoreá╗co-doping and the enlarged interlayer space resulted from the insertion of carbon nanosphere into the graphene sheets. The four-electron selectivity and the limiting current density of the NSGCB nanocomposite are comparable to that of the commercially Pt/C catalyst. Furthermore, the NSGCB nanocomposite was superior to Pt/C in terms of long-term durability and tolerance to methanol poisoning.źáless
Synergistic enhancement of nitrogen and sulfur co-doped graphene with carbon nanospheres insertion for electrocatalytic oxygen reduction reaction
Wu, Min [Huazhong Univ. of Science and Technology, Wuhan (China); Xin, Huolin L. [Brookhaven National Lab. (BNL), Upton, NY (United States); Wang, Jie [Huazhong Univ. of Science and Technology, Wuhan (China); Wu, Zexing [Huazhong Univ. of Science and Technology, Wuhan (China); Wang, Deli [Huazhong Univ. of Science and Technology, Wuhan (China)
A nitrogen and sulfur co-doped graphene/carbon black (NSGCB) nanocomposite for the oxygen reduction reaction (ORR) was synthesized through a one-pot annealing of a precursor mixture containing graphene oxide, thiourea, and acidized carbon black (CB). The NSGCB showed excellent performance for the ORR with the onset and half-way potentials at 0.96 V and 0.81 V (vs. RHE), respectively. It is significantly improved over that of the catalysts derived from only graphene (0.90 V and 0.76 V) or carbon nanosphere (0.82 V and 0.74 V). The enhanced catalytic activity on the NSGCB electrode could be attributed to the synergistic effect of N/S co-doping and the enlarged interlayer space resulted from the insertion of carbon nanosphere into the graphene sheets. The four-electron selectivity and the limiting current density of the NSGCB nanocomposite are comparable to that of the commercially Pt/C catalyst. Furthermore, the NSGCB nanocomposite was superior to Pt/C in terms of long-term durability and tolerance to methanol poisoning.
Enhanced differentiation of neural stem cells to neurons and promotion of neurite outgrowth by oxygen-glucose deprivation.
Wang, Qin; Yang, Lin; Wang, Yaping
Stroke has become the leading cause of mortality worldwide. Hypoxic or ischemic insults are crucial factors mediating the neural damage in the brain tissue of stroke patients. Neural stem cells (NSCs) have been recognized as a promising tool for the treatment of ischemic stroke and other neurodegenerative diseases due to their inducible pluripotency. In this study, we aim to mimick the cerebral hypoxic-ischemic injury in vitro using oxygen-glucose deprivation (OGD) strategy, and evaluate the effects of OGD on the NSC's neural differentiation, as well as the differentiated neurite outgrowth. Our data showed that NSCs under the short-term 2h OGD treatment are able to maintain cell viability and the capability to form neurospheres. Importantly, this moderate OGD treatment promotes NSC differentiation to neurons and enhances the performance of the mature neuronal networks, accompanying increased neurite outgrowth of differentiated neurons. However, long-term 6h and 8h OGD exposures in NSCs lead to decreased cell survival, reduced differentiation and diminished NSC-derived neurite outgrowth. The expressions of neuron-specific microtubule-associated protein 2 (MAP-2) and growth associated protein 43 (GAP-43) are increased by short-term OGD treatments but suppressed by long-term OGD. Overall, our results demonstrate that short-term OGD exposure in vitro induces differentiation of NSCs while maintaining their proliferation and survival, providing valuable insights of adopting NSC-based therapy for ischemic stroke and other neurodegenerative disorders. PMID:25912159
Docosahexaenoic acid prevents paraquat-induced reactive oxygen species production in dopaminergic neurons via enhancement of glutathione homeostasis.
Lee, Hyoung Jun; Han, Jeongsu; Jang, Yunseon; Kim, Soo Jeong; Park, Ji Hoon; Seo, Kang Sik; Jeong, Soyeon; Shin, Soyeon; Lim, Kyu; Heo, Jun Young; Kweon, Gi Ryang
Omega-3 polyunsaturated fatty acid levels are reduced in the substantia nigra area in Parkinson's disease patients and animal models, implicating docosahexaenoic acid (DHA) as a potential treatment for preventing Parkinson's disease and suggesting the need for investigations into how DHA might protect against neurotoxin-induced dopaminergic neuron loss. The herbicide paraquat (PQ) induces dopaminergic neuron loss through the excessive production of reactive oxygen species (ROS). We found that treatment of dopaminergic SN4741 cells with PQ reduced cell viability in a dose-dependent manner, but pretreatment with DHA ameliorated the toxic effect of PQ. To determine the toxic mechanism of PQ, we measured intracellular ROS content in different organelles with specific dyes. As expected, all types of ROS were increased by PQ treatment, but DHA pretreatment selectively decreased cytosolic hydrogen peroxide content. Furthermore, DHA treatment-induced increases in glutathione reductase and glutamate cysteine ligase modifier subunit (GCLm) mRNA expression were positively correlated with glutathione (GSH) content. Consistent with this increase in GCLm mRNA levels, Western blot analysis revealed that DHA pretreatment increased nuclear factor-erythroid 2 related factor 2 (Nrf2) protein levels. These findings indicate that DHA prevents PQ-induced neuronal cell loss by enhancing Nrf2-regulated GSH homeostasis. PMID:25545062
Targeted lung expression of interleukin-11 enhances murine tolerance of 100% oxygen and diminishes hyperoxia-induced DNA fragmentation.
Waxman, A B; Einarsson, O; Seres, T; Knickelbein, R G; Warshaw, J B; Johnston, R; Homer, R J; Elias, J A
Acute lung injury is a frequent and treatment-limiting consequence of therapy with hyperoxic gas mixtures. To determine if IL-11 is protective in oxygen toxicity, we compared the effects of 100% O2 on transgenic mice that overexpress IL-11 in the lung and transgene (-) controls. IL-11 markedly enhanced survival in 100% O2 with 100% of transgene (-) animals dying within 72-96 h and > 90% of transgene (+) animals surviving for more than 10 d. This protection was associated with markedly diminished alveolar-capillary protein leak, endothelial and epithelial membrane injury, lipid peroxidation, and pulmonary neutrophil recruitment. Significant differences in copper zinc superoxide dismutase and catalase activities were not noted and the levels of total, reduced and oxidized glutathione were similar in transgene (+) and (-) animals. Glutathione reductase, glutathione peroxidase, and manganese superoxide dismutase activities were slightly higher in transgene (+) as versus (-) mice after 100% O2 exposure, and IL-11 diminished hyperoxia-induced expression of IL-1 and TNF. Hyperoxia also caused cell death with DNA fragmentation in the lungs of transgene (-) animals and IL-11 markedly diminished this cell death response. These studies demonstrate that IL-11 markedly diminishes hyperoxic lung injury. They also demonstrate this protection is associated with small changes in lung antioxidants, diminished hyperoxia-induced IL-1 and TNF production, and markedly suppressed hyperoxia-induced DNA fragmentation. PMID:9576762
Strongly coupled Pd nanotetrahedron/tungsten oxide nanosheet hybrids with enhanced catalytic activity and stability as oxygen reduction electrocatalysts.
Lu, Yizhong; Jiang, Yuanyuan; Gao, Xiaohui; Wang, Xiaodan; Chen, Wei
The design and synthesis of highly active oxygen reduction reaction (ORR) catalysts with strong durability at low cost is extremely desirable but still remains a significant challenge. Here we develop an efficient strategy that utilizes organopalladium(I) complexes containing palladium-palladium bonds as precursors for the synthesis of strongly coupled Pd tetrahedron-tungsten oxide nanosheet hybrids (Pd/W18O49) to improve the electrocatalytic activity and stability of Pd nanocrystals. The hybrid materials are synthesized by direct nucleation, growth, and anchoring of Pd tetrahedral nanocrystals on the in situ-synthesized W18O49 nanosheets. Compared to supportless Pd nanocrystals and W18O49, their hybrids exhibited not only surprisingly high activity but also superior stability to Pt for the ORR in alkaline solutions. X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and electrochemical analyses indicated that the enhanced electrocatalytic activity and durability are associated with the increased number and improved catalytic activity of active sites, which is induced by the strong interaction between the Pd tetrahedrons and W18O49 nanosheet supports. The present study provides a novel strategy for synthesizing hybrid catalysts with strong chemical attachment and electrical coupling between nanocatalysts and supports. The strategy is expected to open up exciting opportunities for developing a novel class of metal-support hybrid nanoelectrocatalysts with improved ORR activity and durability for both fuel cells and metal-air batteries. PMID:25054583
Time- and energy-efficient solution combustion synthesis of binary metal tungstate nanoparticles with enhanced photocatalytic activity.
Thomas, Abegayl; Janßky, Csaba; Samu, Gergely F; Huda, Muhammad N; Sarker, Pranab; Liu, J Ping; van Nguyen, Vuong; Wang, Evelyn H; Schug, Kevin A; Rajeshwar, Krishnan
In the search for stable and efficient photocatalysts beyond TiO2 , the tungsten-based oxide semiconductors silver tungstate (Ag2 WO4 ), copper tungstate (CuWO4 ), and zinc tungstate (ZnWO4 ) were prepared using solution combustion synthesis (SCS). The tungsten precursor's influence on the product was of particular relevance to this study, and the most significant effects are highlighted. Each sample's photocatalytic activity towards methyl orange degradation was studied and benchmarked against their respective commercial oxide sample obtained by solid-state ceramic synthesis. Based on the results herein, we conclude that SCS is a time- and energy-efficient method to synthesize crystalline binary tungstate nanomaterials even without additional excessive heat treatment. As many of these photocatalysts possess excellent photocatalytic activity, the discussed synthetic strategy may open sustainable materials chemistry avenues to solar energy conversion and environmental remediation. PMID:26018624
One-step solution-combustion synthesis of complex spinel titanate flake particles with enhanced lithium-storage properties
NASA Astrophysics Data System (ADS)
Li, Xue; Xiao, Qian; Liu, Bo; Lin, Huangchang; Zhao, Jinbao
In this work, we report the formation of porous Li2MTi3O8 (M = Zn, Co) flakes (hereafter referred to as f-Li2MTi3O8) via a facile one-step solution-combustion in less than 10 min. As anodes for rechargeable lithium-ion batteries, the synthesized f-Li2MTi3O8 exhibits high reversible charge-discharge capacity, great cycling stability and high rate performance. These results can be attributed to the intrinsic characteristics of spinel Li2MTi3O8 flakes, in which a porous framework could provide a diffusion space for lithium ion insertion into and extraction from the anode material, resulting in excellent cycle performance, even cycling at high rate of 2000 mA g-1.
Hybrid membrane--PSA system for separating oxygen from air
Staiger, Chad L. (Albuquerque, NM); Vaughn, Mark R. (Albuquerque, NM); Miller, A. Keith (Albuquerque, NM); Cornelius, Christopher J. (Blackburg, VA)
A portable, non-cryogenic, oxygen generation system capable of delivering oxygen gas at purities greater than 98% and flow rates of 15 L/min or more is described. The system consists of two major components. The first component is a high efficiency membrane capable of separating argon and a portion of the nitrogen content from air, yielding an oxygen-enriched permeate flow. This is then fed to the second component, a pressure swing adsorption (PSA) unit utilizing a commercially available, but specifically formulated zeolite compound to remove the remainder of the nitrogen from the flow. The system is a unique gas separation system that can operate at ambient temperatures, for producing high purity oxygen for various applications (medical, refining, chemical production, enhanced combustion, fuel cells, etc . . . ) and represents a significant advance compared to current technologies.
Oxygenated organic products of incomplete combustion, including oxygenated PAHs and phthalates, have been found in combustor emissions. Some have substantial health effects and significantly influence the risk assessment calculations. Others are found that may or may not be a...
Non-equilibrium Plasma-Assisted Combustion
NASA Astrophysics Data System (ADS)
Sun, Wenting
As a promising method to enhance combustion, plasma-assisted combustion has drawn considerable attention. Due to the fast electron impact excitation and dissociation of molecules at low temperatures, plasma introduces new reaction pathways, changes fuel oxidation timescales, and can dramatically modify the combustion processes. In this dissertation, the radical generation from the plasma and its effect on flame extinction and ignition were investigated experimentally together with detailed numerical simulation on a counterflow CH4 diffusion flame. It was found that the atomic oxygen production played a dominant role in enhancing the chain-branching reaction pathways and accelerating fuel oxidation at near limit flame conditions. To understand the direct coupling effect between plasma and flame, a novel plasma-assisted combustion system with in situ discharge in a counterflow diffusion flame was developed. The ignition and extinction characteristics of CH4/O 2/He diffusion flames were investigated. For the first time, it was demonstrated that the strong plasma-flame coupling in in situ discharge could significantly modify the ignition/extinction characteristics and create a new fully stretched ignition S-curve. To understand low temperature kinetics of combustion, it is critical to measure the formation and decomposition of H2O2. A molecular beam mass spectrometry (MBMS) system was developed and integrated with a laminar flow reactor. H2O2 measurements were directly calibrated, and compared to kinetic models. The results confirmed that low and intermediate temperature DME oxidation produced significant amounts of H2O2. The experimental characterizations of important intermediate species including H2O2, CH2O and CH3OCHO provided new capabilities to investigate and improve the chemical kinetics especially at low temperatures. A numerical scheme for model reduction was developed to improve the computational efficiency in the simulation of combustion with detailed kinetics. A multi-generation Path Flux Analysis (PFA) method for kinetic mechanism reduction is proposed and validated. In this method, the formation and consumption fluxes of each species at multiple reaction path generations were analyzed and used to identify the important reaction pathways. The comparisons of the ignition delays, flame speeds, and flame structures showed that the PFA method presented a higher accuracy than that of current existing methods in a broad range of initial pressures and temperatures.
NASA Astrophysics Data System (ADS)
Merker, G.; Schwarz, C.; Stiesch, G.; Otto, F.
The content spans from simple thermodynamics of the combustion engine to complex models for the description of the air/fuel mixture, ignition, combustion and pollutant formation considering the engine periphery of petrol and diesel engines. Thus the emphasis of the book is on the simulation models and how they are applicable for the development of modern combustion engines. Computers can be used as the engineers testbench following the rules and recommendations described here.
Synergistically enhanced activity of graphene quantum dot/multi-walled carbon nanotube composites as metal-free catalysts for oxygen reduction reaction.
Zhou, Xuemei; Tian, Zhimin; Li, Jing; Ruan, Hong; Ma, Yuanyuan; Yang, Zhi; Qu, Yongquan
Graphene quantum dots (GQDs), as metal-free carbon nanomaterials, have potential applications in electrochemical fields due to their strong chemical inertness, oxygen-rich functional groups and remarkable quantum confinement and edge effects. Herein, we demonstrate that a novel metal-free electrode composed of GQDs and multi-walled carbon nanotubes (MWCNTs) exhibits a significant synergistic effect on enhanced catalytic activity for oxygen reduction reaction (ORR). Compared to commercially available Pt/C catalysts, enhanced electrocatalytic activity, improved long-term stability and excellent resistance to crossover effect were observed for the novel composite electrode. Interestingly, the amount of GQDs introduced is found to have an apparent effect on the positions of the reduction peaks of the electrodes. PMID:24477654
Enhancing effect of the endocrine disruptor para-nonylphenol on the generation of reactive oxygen species in human blood neutrophils.
Okai, Yasuji; Sato, Eisuke F; Higashi-Okai, Kiyoka; Inoue, Masayasu
Although para-nonylphenol (NP) is known as an endocrine disruptor, the immunologic effect of NP has been poorly analyzed. We found that NP from 5 to 50 microM caused a dose-dependent stimulatory effect on the generation of reactive oxygen species (ROS) in human blood neutrophils, which was measured by using a chemiluminescence reagent, luminol. Furthermore, ROS-scavenging enzymes such as catalase and superoxide dismutase and antioxidative agents alpha-tocopherol and beta-carotene showed strong preventive effects on NP-induced ROS generation. To analyze the biochemical mechanism of NP-induced ROS generation in human neutrophils, we investigated the effects of different types of metabolic inhibitor for the activation pathways of ROS generation in the cells. Reduced nicotinamide adenine dinucleotide phosphate (NADPH)-dependent oxidase inhibitor, diphenyl iodonium chloride and the myeloperoxidase inhibitor sodium azide (NaN3) showed remarkable inhibitory effects on ROS generation induced by NP, but an inhibitor against mitochondrial respiratory function, potassium cyanide (KCN), did not exhibit significant effect. Furthermore, the phosphatidylinositol-3 (PI3) kinase inhibitor wortmannin and the tyrosine kinase inhibitor protein phosphorylation inhibitor 1 (PP1) caused strong suppression against NP-induced ROS generation. The selective protein kinase C inhibitor Ro-32-0432, p38 MAP kinase inhibitor SB 203580, and ERK MAP kinase inhibitor PD 98059 also showed significant suppressive effects on NP-induced ROS generation. These results suggest that NP causes an enhancing effect on ROS generation in human blood neutrophils through the activation of signal transduction pathways associated with the respiratory burst function in these cells. Additionally, to examine in vivo effects of NP, we also analyzed the effects of NP itself and the synergistic effects of NP and a typical inflammatory agent, opsonized zymosan, on human whole blood including neutrophils. PMID:15064160
Ketamine Enhances Human Neural Stem Cell Proliferation and Induces Neuronal Apoptosis Via Reactive Oxygen Species-Mediated Mitochondrial Pathway
Bai, Xiaowen; Yan, Yasheng; Canfield, Scott; Muravyeva, Maria Y.; Kikuchi, Chika; Zaja, Ivan; Corbett, John A.; Bosnjak, Zeljko J.
Background Growing evidence indicates that ketamine causes neurotoxicity in a variety of developing animal models, leading to a serious concern regarding the safety of pediatric anesthesia. However, if and how ketamine induces human neural cell toxicity is unknown. Recapitulation of neurogenesis from human embryonic stem cells (hESCs) in vitro allows investigation of the toxic effects of ketamine on neural stem cells (NSCs) and developing neurons which is impossible to perform in humans. In the present study we assessed the influence of ketamine on the hESC-derived NSCs and neurons. Methods hESCs were directly differentiated into neurons via NSCs. NSCs and two-week-old neurons were treated with varying doses of ketamine for different durations. NSC proliferation capacity was analyzed by Ki67 immunofluorescence staining and bromodeoxyurindine assay. Neuroapoptosis was analyzed by TUNEL staining and caspase 3 activity measurement. The mitochondria-related neuronal apoptosis pathway including mitochondrial membrane potential, cytochrome c distribution within cells, mitochondrial fission, and reactive oxygen species (ROS) production were also investigated. Results Ketamine (100 ?M) increased NSC proliferation after 6 h exposure. However, significant neuronal apoptosis was only observed after 24 h of ketamine treatment. In addition, ketamine decreased mitochondrial membrane potential and increased cytochrome c release from mitochondria into cytosol. Ketamine also enhanced mitochondrial fission as well as ROS production compared with no-treatment control. Importantly, Trolox, a ROS scavenger, significantly attenuated the increase of ketamine-induced ROS production and neuronal apoptosis. Conclusions These data for the first time demonstrate that (1) ketamine increases NSC proliferation and causes neuronal apoptosis; (2) mitochondria are involved in ketamine-induced neuronal toxicity which can be prevented by Trolox; and (3) the stem cell-associated neurogenesis system may provide a simple and promising in vitro model for rapidly screening anesthetic neurotoxicity and studying the underlying mechanisms as well as prevention strategies to avoid this toxic effect. PMID:23460563
Aluminum-doped ceria-zirconia solid solutions with enhanced thermal stability and high oxygen storage capacity
NASA Astrophysics Data System (ADS)
Dong, Qiang; Yin, Shu; Guo, Chongshen; Sato, Tsugio
A facile solvothermal method to synthesize aluminum-doped ceria-zirconia (Ce0.5Zr0.5- x Al x O2- x/2, x = 0.1 to 0.4) solid solutions was carried out using Ce(NH4)2(NO3)6, Zr(NO3)3Ě2H2O Al(NO3)3Ě9H2O, and NH4OH as the starting materials at 200░C for 24 h. The obtained solid solutions from the solvothermal reaction were calcined at 1,000░C for 20 h in air atmosphere to evaluate the thermal stability. The synthesized Ce0.5Zr0.3Al0.2O1.9 particle was characterized for the oxygen storage capacity (OSC) in automotive catalysis. For the characterization, X-ray diffraction, transmission electron microscopy, and the Brunauer-Emmet-Teller (BET) technique were employed. The OSC values of all samples were measured at 600░C using thermogravimetric-differential thermal analysis. Ce0.5Zr0.3Al0.2O1.9 solid solutions calcined at 1,000░C for 20 h with a BET surface area of 18 m2 g-1 exhibited a considerably high OSC of 427 ?mol-O g-1 and good OSC performance stability. The same synthesis route was employed for the preparation of the CeO2 and Ce0.5Zr0.5O2. The incorporation of aluminum ion in the lattice of ceria-based catalyst greatly enhanced the thermal stability and OSC.
Aluminum-doped ceria-zirconia solid solutions with enhanced thermal stability and high oxygen storage capacity
A facile solvothermal method to synthesize aluminum-doped ceria-zirconia (Ce0.5Zr0.5-xAlxO2-x/2, x?=?0.1 to 0.4) solid solutions was carried out using Ce(NH4)2(NO3)6, Zr(NO3)3Ě2H2O Al(NO3)3Ě9H2O, and NH4OH as the starting materials at 200░C for 24 h. The obtained solid solutions from the solvothermal reaction were calcined at 1,000░C for 20 h in air atmosphere to evaluate the thermal stability. The synthesized Ce0.5Zr0.3Al0.2O1.9 particle was characterized for the oxygen storage capacity (OSC) in automotive catalysis. For the characterization, X-ray diffraction, transmission electron microscopy, and the Brunauer-Emmet-Teller (BET) technique were employed. The OSC values of all samples were measured at 600░C using thermogravimetric-differential thermal analysis. Ce0.5Zr0.3Al0.2O1.9 solid solutions calcined at 1,000░C for 20 h with a BET surface area of 18 m2 g?1 exhibited a considerably high OSC of 427 ?mol-O g?1 and good OSC performance stability. The same synthesis route was employed for the preparation of the CeO2 and Ce0.5Zr0.5O2. The incorporation of aluminum ion in the lattice of ceria-based catalyst greatly enhanced the thermal stability and OSC. PMID:23025588
Aluminum-doped ceria-zirconia solid solutions with enhanced thermal stability and high oxygen storage capacity.
Dong, Qiang; Yin, Shu; Guo, Chongshen; Sato, Tsugio
A facile solvothermal method to synthesize aluminum-doped ceria-zirconia (Ce0.5Zr0.5-xAlxO2-x/2, x?=?0.1 to 0.4) solid solutions was carried out using Ce(NH4)2(NO3)6, Zr(NO3)3Ě2H2O Al(NO3)3Ě9H2O, and NH4OH as the starting materials at 200░C for 24 h. The obtained solid solutions from the solvothermal reaction were calcined at 1,000░C for 20 h in air atmosphere to evaluate the thermal stability. The synthesized Ce0.5Zr0.3Al0.2O1.9 particle was characterized for the oxygen storage capacity (OSC) in automotive catalysis. For the characterization, X-ray diffraction, transmission electron microscopy, and the Brunauer-Emmet-Teller (BET) technique were employed. The OSC values of all samples were measured at 600░C using thermogravimetric-differential thermal analysis. Ce0.5Zr0.3Al0.2O1.9 solid solutions calcined at 1,000░C for 20 h with a BET surface area of 18 m2 g-1 exhibited a considerably high OSC of 427 ?mol-O g-1 and good OSC performance stability. The same synthesis route was employed for the preparation of the CeO2 and Ce0.5Zr0.5O2. The incorporation of aluminum ion in the lattice of ceria-based catalyst greatly enhanced the thermal stability and OSC. PMID:23025588
2D ultrathin core-shell Pd@Ptmonolayer nanosheets: defect-mediated thin film growth and enhanced oxygen reduction performance.
Wang, Wenxin; Zhao, Yunfeng; Ding, Yi
An operational strategy for the synthesis of atomically smooth Pt skin by a defect-mediated thin film growth method is reported. Extended ultrathin core-shell structured d@Ptmonolayer nanosheets (thickness below 5 nm) exhibit nearly seven-fold enhancement in mass-activity and surprisingly good durability toward oxygen reduction reaction as compared with the commercial Pt/C catalyst. PMID:26119595
Electronic resonance enhanced coherent anti-Stokes Raman scattering technique for detection of combustion species and biological moleculesá
Hanna, Sherif Fayez
The application of electronic-resonance enhanced (ERE) coherent anti-Stokes Raman scattering (CARS) for the detection of nitric oxide (NO) and acetylene (C2H2) is experimentally demonstrated and the effects of various parameters on the ERE CARS...
Electronic resonance enhanced coherent anti-Stokes Raman scattering technique for detection of combustion species and biological molecules
Hanna, Sherif Fayez
The application of electronic-resonance enhanced (ERE) coherent anti-Stokes Raman scattering (CARS) for the detection of nitric oxide (NO) and acetylene (C2H2) is experimentally demonstrated and the effects of various parameters on the ERE CARS...
Influence of H 2 O, CO 2 and various combustible gases on the characteristics of a limiting current-type oxygen sensor
Keiichi Saji; Haruyoshi Kondo; Hideaki Takahashi; Takashi Takeuchi; Isemi Igarashi
Current-voltage characteristics of limiting current-type oxygen sensors were investigated. The sensor showed a two-stage current plateau in current-voltage characteristics in H2O-O2-N2 and CO2-O2-N2 mixtures. The sensor current in the first stage corresponded to O2 concentration and was practically independent of H2O and CO2 concentration in the gas mixtures. The sensor current in the second stage increased linearly with the H2O
Assessment of the effect of high ash content in pulverized coal combustion
Jayanti, S.; Maheswaran, K.; Saravanan, V. [Indian Institute of Technology, Madras (India). Dept. of Chemical Engineering
The existing literature on CFD-based coal combustion modelling is applicable mainly for coals of low ash content and the calculations are done on an ash-free basis. In Indian coals, the ash content may be significantly higher, up to 40% or more. Studies reported in the literature show that the mineral matter in the coal may have a number of effects on the combustion characteristics. In the present study, a sensitivity analysis is performed, using the CFD code CFX of AEA Technology, on the likely effect of ash content on the char reactivity, oxygen diffusion rate for char combustion and on the radiative heat transfer parameters. The results show that the effect of enhanced char reactivity is negligible whereas reduced oxygen diffusion rates due to a thicker ash layer may result in a significant reduction in char oxidation rates with a resultant decrease in the peak temperature in the furnace. The global parameters such as the peak temperature and the flue gas temperature remain relatively insensitive to the presence of high ash content. These results are consistent with the experimental observations of Kurose et al. . Kurose, M. Ikeda, H. Makino, Combustion characteristics of high ash coal in pulverized coal combustion, J. Fuel 80 (2001) 1447-1455).
Synoviocyte Derived-Extracellular Matrix Enhances Human Articular Chondrocyte Proliferation and Maintains Re-Differentiation Capacity at Both Low and Atmospheric Oxygen Tensions
Kean, Thomas J.; Dennis, James E.
Background Current tissue engineering methods are insufficient for total joint resurfacing, and chondrocytes undergo de-differentiation when expanded on tissue culture plastic. De-differentiated chondrocytes show poor re-differentiation in culture, giving reduced glycosaminoglycan (GAG) and collagen matrix accumulation. To address this, porcine synoviocyte-derived extracellular matrix and low (5%) oxygen tension were assessed for their ability to enhance human articular chondrocyte expansion and maintain re-differentiation potential. Methods Porcine synoviocyte matrices were devitalized using 3 non-detergent methods. These devitalized synoviocyte matrices were compared against tissue culture plastic for their ability to support human chondrocyte expansion. Expansion was further compared at both low (5%), and atmospheric (20%) oxygen tension on all surfaces. Expanded cells then underwent chondrogenic re-differentiation in aggregate culture at both low and atmospheric oxygen tension. Aggregates were assessed for their GAG and collagen content both biochemically and histologically. Results Human chondrocytes expanded twice as fast on devitalized synoviocyte matrix vs. tissue culture plastic, and cells retained their re-differentiation capacity for twice the number of population doublings. There was no significant difference in growth rate between low and atmospheric oxygen tension. There was significantly less collagen type I, collagen type II, aggrecan and more MMP13 expression in cells expanded on synoviocyte matrix vs. tissue culture plastic. There were also significant effects due to oxygen tension on gene expression, wherein there was greater collagen type I, collagen type II, SOX9 and less MMP13 expression on tissue culture plastic compared to synoviocyte matrix. There was a significant increase in GAG, but not collagen, accumulation in chondrocyte aggregates re-differentiated at low oxygen tension over that achieved in atmospheric oxygen conditions. Conclusions Synoviocyte-derived matrix supports enhanced expansion of human chondrocytes such that the chondrocytes are maintained in a state from which they can re-differentiate into a cartilage phenotype after significantly more population doublings. Also, low oxygen tension supports GAG, but not collagen, accumulation. These findings are a step towards the production of a more functional, tissue engineered cartilage. PMID:26075742
Combustion Group Group members
Wang, Wei
Combustion Group Group members: Thierry Poinsot, Emilien Courtine, Luc Vervisch, Benjamin Farcy ž New combustion and energy-conversion concepts #12;Introduction Combustion research thrusts Combustion Dynamics and Flame-Stabilization Research objectives ž Obtain fundamental understanding of combustion
Combustion chamber for internal combustion engine
This patent describes a combustion chamber for an internal combustion engine, comprising: a main combustion chamber hollowed out of the top of a piston; a subsidiary combustion chamber hollowed out of the piston top, the subsidiary combustion chamber communicating with and disposed in side by side relationship to the main combustion chamber; a fuel injection nozzle located generally between the
Microgravity Smoldering Combustion Takes Flight
NASA Technical Reports Server (NTRS)
The Microgravity Smoldering Combustion (MSC) experiment lifted off aboard the Space Shuttle Endeavour in September 1995 on the STS-69 mission. This experiment is part of series of studies focused on the smolder characteristics of porous, combustible materials in a microgravity environment. Smoldering is a nonflaming form of combustion that takes place in the interior of combustible materials. Common examples of smoldering are nonflaming embers, charcoal briquettes, and cigarettes. The objective of the study is to provide a better understanding of the controlling mechanisms of smoldering, both in microgravity and Earth gravity. As with other forms of combustion, gravity affects the availability of air and the transport of heat, and therefore, the rate of combustion. Results of the microgravity experiments will be compared with identical experiments carried out in Earth's gravity. They also will be used to verify present theories of smoldering combustion and will provide new insights into the process of smoldering combustion, enhancing our fundamental understanding of this frequently encountered combustion process and guiding improvement in fire safety practices.
Effect of Hydrologic and Geochemical Conditions on Oxygen-Enhanced Bioremediation in a Gasoline-Contaminated Aquifer
Landmeyer, J.E.; Bradley, P.M.
The effect of pre-existing factors, e.g., hydrologic, geochemical, and microbiological properties, on the results of oxygen addition to a reformulated gasoline-contaminated groundwater system was studied. Oxygen addition with an oxygen-release compound (a proprietary form of magnesium peroxide produced different results with respect to dissolved oxygen (DO) generation and contaminant decrease in the two locations. Oxygen-release compound injected at the former UST source area did not significantly change measured concentrations of DO, benzene, toluene, or MTBE. Conversely, oxygen-release compound injected 200 m downgradient of the former UST source area rapidly increased DO levels, and benzene, toluene, and MTBE concentrations decreased substantially. The different results could be related to differences in hydrologic and geochemical conditions that characterized the two locations prior to oxygen addition. The lack of recharge to ground water in the paved UST source area led to a much larger geochemical sink for DO compared to ground water in the unpaved area.
Investigation of gasification chemical looping combustion combined cycle performance
Wenguo Xiang; Sha Wang; Tengteng Di
A novel combined cycle based on coal gasification and chemical looping combustion (CLC) offers a possibility of both high net power efficiency and separation of the greenhouse gas CO. The technique involves the use of a metal oxide as an oxygen carrier, which transfers oxygen from the combustion air to the fuel, and the avoidance of direct contact between fuel
Enhanced growth and recombinant protein production of Escherichia coli by a perfluorinated oxygen carrier in miniaturized fed-batch cultures
Background Liquid perfluorochemicals (PFCs) are interesting oxygen carriers in medicine and biotechnology with a high solubility for oxygen. They have been repeatedly used for improving oxygen transfer into prokaryotic and eukaryotic cell cultures, however their application is still limited. Here we show the great benefit of air/oxygen saturated perfluorodecalin (PFD) for high cell density cultivation of Escherichia coli in microwell plates and their positive effect on the soluble production of a correctly folded heterologously expressed alcohol dehydrogenase. Results In EnBase« cultivations the best effect was seen with PFD saturated with oxygen enriched air (appr. 10 ?M oxygen per ml) when PFD was added at the time of induction. In contrast the effect of PFD was negligible when it was added already at the time of inoculation. Optimisation of addition time and content of loaded oxygen into the PFD resulted in an increased the cell density by 40% compared to control cultures, and correspondingly also the product yield increased, demonstrated at the example of a recombinant alcohol dehydrogenase. Conclusions PFCs are a valuable additive in miniaturized cell culture formats. For production of recombinant proteins in low cell density shaken cultures the addition of oxygen-enriched PFD makes the process more robust, i.e. a high product yield is not any more limited to a very narrow cell density window during which the induction has to be done. The positive effect of PFD was even more obvious when it was added during high cell density cultures. The effect of the PFD phase depends on the amount of oxygen which is loaded into the PFD and which thus is a matter of optimisation. PMID:21708024
Summary of Simplified Two Time Step Method for Calculating Combustion Rates and Nitrogen Oxide Emissions for Hydrogen/Air and Hydrogen/Oxygen
NASA Technical Reports Server (NTRS)
Marek, C. John; Molnar, Melissa
A simplified single rate expression for hydrogen combustion and nitrogen oxide production was developed. Detailed kinetics are predicted for the chemical kinetic times using the complete chemical mechanism over the entire operating space. These times are then correlated to the reactor conditions using an exponential fit. Simple first order reaction expressions are then used to find the conversion in the reactor. The method uses a two time step kinetic scheme. The first time averaged step is used at the initial times with smaller water concentrations. This gives the average chemical kinetic time as a function of initial overall fuel air ratio, temperature, and pressure. The second instantaneous step is used at higher water concentrations (greater than l x 10(exp -20)) moles per cc) in the mixture which gives the chemical kinetic time as a function of the instantaneous fuel and water mole concentrations, pressure and temperature (T(sub 4)). The simple correlations are then compared to the turbulent mixing times to determine the limiting properties of the reaction. The NASA Glenn GLSENS kinetics code calculates the reaction rates and rate constants for each species in a kinetic scheme for finite kinetic rates. These reaction rates are used to calculate the necessary chemical kinetic times. This time is regressed over the complete initial conditions using the Excel regression routine. Chemical kinetic time equations for H2 and NOx are obtained for H2/Air fuel and for H2/O2. A similar correlation is also developed using data from NASA's Chemical Equilibrium Applications (CEA) code to determine the equilibrium temperature (T(sub 4)) as a function of overall fuel/air ratio, pressure and initial temperature (T(sub 3)). High values of the regression coefficient R squared are obtained.
Simplified Two-Time Step Method for Calculating Combustion Rates and Nitrogen Oxide Emissions for Hydrogen/Air and Hydorgen/Oxygen
NASA Technical Reports Server (NTRS)
Molnar, Melissa; Marek, C. John
A simplified single rate expression for hydrogen combustion and nitrogen oxide production was developed. Detailed kinetics are predicted for the chemical kinetic times using the complete chemical mechanism over the entire operating space. These times are then correlated to the reactor conditions using an exponential fit. Simple first order reaction expressions are then used to find the conversion in the reactor. The method uses a two-time step kinetic scheme. The first time averaged step is used at the initial times with smaller water concentrations. This gives the average chemical kinetic time as a function of initial overall fuel air ratio, temperature, and pressure. The second instantaneous step is used at higher water concentrations (> 1 x 10(exp -20) moles/cc) in the mixture which gives the chemical kinetic time as a function of the instantaneous fuel and water mole concentrations, pressure and temperature (T4). The simple correlations are then compared to the turbulent mixing times to determine the limiting properties of the reaction. The NASA Glenn GLSENS kinetics code calculates the reaction rates and rate constants for each species in a kinetic scheme for finite kinetic rates. These reaction rates are used to calculate the necessary chemical kinetic times. This time is regressed over the complete initial conditions using the Excel regression routine. Chemical kinetic time equations for H2 and NOx are obtained for H2/air fuel and for the H2/O2. A similar correlation is also developed using data from NASA s Chemical Equilibrium Applications (CEA) code to determine the equilibrium temperature (T4) as a function of overall fuel/air ratio, pressure and initial temperature (T3). High values of the regression coefficient R2 are obtained.
Catalysis: Enhanced Catalytic Efficiency of Pt Nanoparticles Supported on 3D Ordered Macro-/Mesoporous Ce0.6 Zr0.3 Y0.1 O2 for Methane Combustion (Small 20/2015).
Arandiyan, Hamidreza; Dai, Hongxing; Ji, Kemeng; Sun, Hongyu; Zhao, Yanyan; Li, Junhua
The synthesis of 3D ordered macroporous (3DOM) Ce0.6 Zr0.3 Y0.1 O2 (CZY) is demonstrated by H. Arandiyan, H. Dai, J. Li, and co-workers on page 2366. The 3DOM CZY has mesoporous walls and a high surface area, and incorporates a high dispersion of platinum nanoparticles. A sample with 1.1 wt% Pt shows supercatalytic activity for methane combustion, which is attributed to its larger surface area, higher oxygen adspecies concentration, better low-temperature reducibility, and the unique 3DOM structure. PMID:25995146
Enhanced Catalytic Efficiency of Pt Nanoparticles Supported on 3D Ordered Macro-/Mesoporous Ce0.6 Zr0.3 Y0.1 O2 for Methane Combustion.
Arandiyan, Hamidreza; Dai, Hongxing; Ji, Kemeng; Sun, Hongyu; Zhao, Yanyan; Li, Junhua
Highly dispersed Pt nanoparticles supported on high-surface-area 3D ordered macroporous (3DOM) Ce0.6 Zr0.3 Y0.1 O2 (CZY) are synthesized via a bubbling cetyltrimethyl ammonium bromide/P123-assisted reduction route. The 1.1 wt% Pt/3DOM CZY catalyst shows supercatalytic activity for methane combustion, which is attributed to a higher oxygen adspecies amount, larger surface area, better low-temperature reducibility, and unique nanovoid-walled 3DOM structure. PMID:25677467
Hydrothermal Synthesis of Lanthanide Stannates Pyrochlore Nanocrystals for Catalytic Combustion of Soot Particulates
Nanocrystalline La2Sn2O7 and La2Sn1.8Co0.2O7 with a phase-pure pyrochlore structure were synthesized by a hydrothermal method, and their catalytic activity was investigated for soot combustion. The as-synthesized catalysts presented relatively larger surface area, and pore volume, which was benefit to the gas molecule diffusion in the reaction. A uniform spherical structure with particle size of 200ľ500?nm was found in SEM. The samples via hydrothermal route are more active for catalytic soot combustion, ascribing to the spherical morphology, high surface area and improved oxygen mobility. After Co, the reducibility was improved and surface oxygen vacancy was produced, resulting in the enhanced activity and selectivity to CO2 formation.
Riccardi, R. C.
. Because each furnace is designed and operated differently, careful evaluation is required. Look at several options. The performance and efficiency of a combustion system depends upon several major factors. They are: 1) Fuel to air ratio control, 2) Fuel...
Kashinath C Patil; Singanahally T Aruna; Sambandan Ekambaram
Many innovative self-propagating high-temperature synthesis (SHS) techniques such as filtration, combustion, the centrifugal thermite process, field activated combustion, solid-state metathesis, flame synthesis and simultaneous SHS and densification have been developed for the synthesis of Ĺadvanced materialsĺ. A novel gas producing self-propagating process initiated at low temperature using redox compounds and mixtures has been used for the preparation of fine particle
Photostability enhancement of Pyrromethene 567 and Perylene Orange in oxygen-free liquid and solid dye lasers.
Rahn, M D; King, T A; Gorman, A A; Hamblett, I
We investigated the effect of oxygen on the photostability of the laser dyes Pyrromethene 567, Perylene Orange, and Rhodamine 590 by determining their longevity of laser operation when pumped by the second harmonic of aQ -switched Nd:YAG laser. In solution, dissolved oxygen accelerated the photodegradation of Pyrromethene 567 and Perylene Orange but not Rhodamine 590. The photostability of Pyrromethene 567 was also found to be dependent on the solvent and on the lifetime of singlet oxygen. Deoxygenated Pyrromethene 567 doped polycom glass and modified poly(methyl methacrylate) (MPMMA) samples were tested for longevity of laser operation. A factor of 6 improvement in photostability was found for Pyrromethene 567 in MPMMA upon deoxygenation, and the total absorbed energy per mole of dye molecules to one-half output pulse energy was 36 GJ mol-1 . PMID:18259419
Enhanced response of microbial fuel cell using sulfonated poly ether ether ketone membrane as a biochemical oxygen demand sensor.
Ayyaru, Sivasankaran; Dharmalingam, Sangeetha
The present study is focused on the development of single chamber microbial fuel cell (SCMFC) using sulfonated poly ether ether ketone (SPEEK) membrane to determine the biochemical oxygen demand (BOD) matter present in artificial wastewater (AW). The biosensor produces a good linear relationship with the BOD concentration up to 650 ppm when using artificial wastewater. This sensing range was 62.5% higher than that of Nafion(«). The most serious problem in using MFC as a BOD sensor is the oxygen diffusion into the anode compartment, which consumes electrons in the anode compartment, thereby reducing the coulomb yield and reducing the electrical signal from the MFC. SPEEK exhibited one order lesser oxygen permeability than Nafion(«), resulting in low internal resistance and substrate loss, thus improving the sensing range of BOD. The system was further improved by making a double membrane electrode assembly (MEA) with an increased electrode surface area which provide high surface area for electrically active bacteria. PMID:24626398
Vertical migration of aggregated aerobic and anaerobic ammonium oxidizers enhances oxygen uptake in a stagnant water layer
Siegfried E. Vlaeminck; Katleen Dierick; Nico Boon; Willy Verstraete
Ammonium can be removed as dinitrogen gas by cooperating aerobic and\\u000a anaerobic ammonium-oxidizing bacteria (AerAOB and AnAOB). The goal of\\u000a this study was to verify putative mutual benefits for aggregated AerAOB\\u000a and AnAOB in a stagnant freshwater environment. In an ammonium fed water\\u000a column, the biological oxygen consumption rate was, on average, 76 kg\\u000a O-2 ha(-1)day(-1). As the oxygen transfer
Combustion chamber for internal combustion engines
A combustion chamber for internal combustion engines, of the type including means for producing swirl within the combustion chamber is described comprising: a combustion chamber provided in the head portion of a piston in the form of a cavity recessed in the axial direction of the piston; fuel injection nozzle means disposed in the combustion chamber and positioned eccentrically with
Combustion chamber for internal combustion engines
N. Yanagisawa; Y. Sato
A combustion chamber is described for an internal combustion engine, comprising: a main combustion chamber defined by a recess in the top of a piston of the engine, the main combustion chamber being formed with its opening diameter progressively enlarged downwards in the axial direction of the main combustion chamber, and a lip part formed along the periphery of the
Kinetics of oxygen-enhanced water gas shift on bimetallic catalysts and the roles of metals and support
NASA Astrophysics Data System (ADS)
Kugai, Junichiro
The post-processing of reformate is an important step in producing hydrogen (H2) with low carbon monoxide (CO) for low temperature fuel cells from syn-gas. However, the conventional process consists of three steps, i.e. two steps of water gas shift (WGS) and preferential oxidation (PROX) of CO, and it is not suitable for mobile applications due to the large volume of water gas shift (WGS) catalysts and conditioning and/or regeneration necessary for these catalysts. Aiming at replacing those three steps by a simple one-step process, small amount of oxygen was added to WGS (the reaction called oxygen-enhanced water gas shift or OWGS) to promote the reaction kinetics and low pyrophoric ceria-supported bimetallic catalysts were employed for stable performance in this reaction. Not only CO conversion, but also H2 yield was found to increase by the O2 addition on CeO2-supported catalysts. The characteristics of OWGS, high H2 production rate at 200 to 300░C at short contact time where unreacted O2 exists, evidenced the impact of O2 addition on surface species on the catalyst. Around 1.5 of reaction order in CO for various CeO2-supported metal catalysts for OWGS compared to reaction orders in CO ranging from -0.1 to 0.6 depending on metal species for WGS shows O2 addition decreases CO coverage to free up the active sites for co-reactant (H2O) adsorption and activation. Among the monometallic and bimetallic catalysts, Pt-Cu and Pd-Cu bimetallic catalysts were superior to monometallic catalysts in OWGS. These bimetallic components were found to form alloys where noble metal is surrounded mainly by Cu to have strong interaction between noble metal and copper resulting in high OWGS activity and low pyrophoric property. The metal loadings were optimized for CeO2-supported Pd-Cu bimetallic system and 2 wt% Pd with 5 -- 10 wt% Cu were found to be the optimum for the present OWGS condition. In the kinetic study, Pd in Pd-Cu was shown to increase the active sites for H2O dissociation and/or the subsequent reaction with chemisorbed CO as well as Pd keeps Cu in reduced state. Cu was found to keep Pd dispersed, suppress H2 activation on Pd, and facilitate CO 2 desorption from catalyst surface. While composition and structure of metal have large impacts on OWGS performance, CeO2 was shown to create new sites for H2O activation at metal-ceria interfacial region in concert with metal. These new sites strongly activate H2O to drive OWGS and WGS compared to the pure metallic sites which are present in majority on Al2O3-supported catalyst. The observed two regimes of turnover rate, the one dependent on catalyst surface area and the other independent of surface area, strongly suggested bifunctional reaction pathway where the reaction rate is determined by activation of H2O and by association of chemisorbed CO and H 2O. The associative route was also evidenced by pulse response study where the reaction occurs only when CO and H2O pulses are supplied together, and thus pre-adsorbed species such as formate and carbonate identified by FT-IR are proven to be spectators. No correlation between WGS rate and isotopic exchange rate of molecularly adsorbed D2O with H 2 showed H2O dissociation is necessary for WGS to occur. Long duration tests revealed CeO2-supported Pd-Cu, Pt-Cu and Cu catalysts are stable in OWGS condition compared to Pt, Pd, and Al 2O3-supported Pd-Cu catalysts which exhibited continuous deactivation during about 70 hours of test. The addition of Cu prevents agglomeration of monometallic Pd and carbonate formation on monometallic Pt during the reaction. The better activity and stability of Pd-Cu and Pt-Cu bimetallic catalysts in the realistic OWGS condition were ascribed to the unique active sites consisting of highly dispersed Pd in Cu or Pt in Cu on CeO2, which are good for H2O activation with low reaction inhibition by the product gases. Pt monometallic catalyst showed and highest activity in OWGS in the absence of product gases, but this was found vulnerable in the presence of product gases due to strong adsorption of H2 and CO2 on t
Study of methods for applying and enhancing transfer film coatings of polytetrafluoroethylene (PTEE) to Space Shuttle Main Engine (SSME) High Pressure Oxygen Turbo Pump (HPOTP) bearings
NASA Technical Reports Server (NTRS)
Kannel, J. W.; Dufrane, K. F.; Zugaro, F. F.
Machines were constructed and evaluated for burnishing polytetrafluoroethylene on balls for use in the high pressure oxygen turbopump (HPOTP). The most positive performance was obtained with single-ball burnishing, but one technique for burnishing three balls simultaneously holds promise. Evaluations of the coatings in a HPOTP bearing of earlier design (employed smaller diameter balls) showed very little life enhancement before high torque and ball and race wear initiated. Other coating techniques, such as molybdenum disulfide combined with PTFE transfer films, hold promise for providing the more durable quantities of solid lubricant needed for the bearings.
The Economics of Oxygen Enriched Air Production Via Membranesá
Gollan, A.; Kleper, M. H.
Oxygen enriched air combustion is a recognized approach to energy conservation. Conventional methods of producing oxygen enriched air: Pressure Swing Adsorption and Cryogenics, are energy-intensive and expensive. In this paper the economics of using...
Research in Industrial Combustion Systems - Current and Future R&Dá
Rebello, W. J.; Keller, J. G.
This paper briefly describes the current R&D activity in industrial combustion systems. The areas covered are novel burner systems, oxygen enriched systems, combustion controls and sensors and unique industrial process modifications. Some...
Mitochondrial reactive oxygen species accelerate the expression of heme carrier protein 1 and enhance photodynamic cancer therapy effect
Ito, Hiromu; Matsui, Hirofumi; Tamura, Masato; Majima, Hideyuki J.; Indo, Hiroko P.; Hyodo, Ichinosuke
Photodynamic therapy using hematoporphyrin and its derivatives is clinically useful for cancer treatments. It has been reported that cancer cells incorporate hematoporphyrin and its derivatives via heme carrier protein 1, which is a proton-coupled folate transporter. However, the mechanism of this protein expression has not been elucidated. In general, the concentration of reactive oxygen species in cancer cells is higher than that in normal cells. We previously reported that reactive oxygen species from mitochondria involved in the expression of peptide transporter 1 and accelerate the uptake of 5-aminolevulinic acid, which is a precursor of protoporphyrin IX. We suggested mitochondrial reactive oxygen species also regulated the expression of heme carrier protein 1. In this study, we used a rat gastric mucosal cell line RGM1 and its cancer-like mutated cell line RGK1. We clarified the expression of heme carrier protein 1 increased in cancer cells and it decreased in manganese superoxide dismutase expressed cancer cells. In addition, the uptake level of hematoporphyrin and photodynamic therapeutic effect were also decreased in manganese superoxide dismutase expressed cancer cells in comparison with cancer cells. Thus, we concluded that mitochondrial reactive oxygen species regulated heme carrier protein 1 expression and photodynamic therapeutic effect. PMID:25120282
Extracellular Matrix Degradation Products and Low-Oxygen Conditions Enhance the Regenerative Potential of Perivascular Stem Cells
Tottey, Stephen; Corselli, Mirko; Jeffries, Eric M.; Londono, Ricardo; Peault, Bruno
Tissue and organ injury results in alterations of the local microenvironment, including the reduction in oxygen concentration and degradation of the extracellular matrix (ECM). The response of perivascular stem cells to these microenvironment changes are of particular interest because of their wide distribution throughout the body and their potential involvement in tissue and organ response to injury. The chemotactic, mitogenic, and phenotypic responses of this stem cell population were evaluated in response to a combination of decreased oxygen concentration and the presence of ECM degradation products. Culture in low-oxygen conditions resulted in increased proliferation and migration of the cells and increased activation of the ERK signaling pathway and associated integrins without a change in cell surface marker phenotype. The addition of ECM degradation products were additive to these processes. Reactive oxygen species within the cells were increased in association with the mitogenic and chemotactic responses. The increased proliferation and chemotactic properties of this stem cell population without any changes in phenotype and differentiation potential has important implications for both in vitro cell expansion and for in vivo behavior of these cells at the site of injury. PMID:20653348
Reference particles for toxicological studies of wood combustion: formation, characteristics, and toxicity compared to those of real wood combustion particulate mass.
Torvela, Tiina; Uski, Oskari; Karhunen, Tommi; Lńhde, Anna; Jalava, Pasi; Sippula, Olli; Tissari, Jarkko; Hirvonen, Maija-Riitta; Jokiniemi, Jorma
Multiple studies show that particulate mass (PM) generated from incomplete wood combustion may induce adverse health issues in humans. Previous findings have shown that also the PM from efficient wood combustion may induce enhanced production of reactive oxygen species (ROS), inflammation, and cytotoxicity in vitro and in vivo. Underlying factors of these effects may be traced back to volatile inorganic transition metals, especially zinc, which can be enriched in the ultrafine fraction of biomass combustion particulate emission. In this study, nanoparticles composed of potassium, sulfur, and zinc, which are the major components forming inorganic fine PM, were synthesized and tested in vitro. In addition, in vitro toxicity of PM from efficient combustion of wood chips was compared with that of the synthesized particles. Cytotoxicity, cell cycle arrest, ROS generation, and tumor necrosis factor alpha release were related to zinc concentration in PM. Potassium sulfate and potassium carbonate did not induce toxic responses. In light of the provided data, it can be concluded that zinc, enriched in wood combustion emissions, caused the toxicity in all of the measured end points. PMID:25063562
Space Station Freedom combustion research
NASA Technical Reports Server (NTRS)
Faeth, G. M.
Extended operations in microgravity, on board spacecraft like Space Station Freedom, provide both unusual opportunities and unusual challenges for combustion science. On the one hand, eliminating the intrusion of buoyancy provides a valuable new perspective for fundamental studies of combustion phenomena. On the other hand, however, the absence of buoyancy creates new hazards of fires and explosions that must be understood to assure safe manned space activities. These considerations - and the relevance of combustion science to problems of pollutants, energy utilization, waste incineration, power and propulsion systems, and fire and explosion hazards, among others - provide strong motivation for microgravity combustion research. The intrusion of buoyancy is a greater impediment to fundamental combustion studies than to most other areas of science. Combustion intrinsically heats gases with the resulting buoyant motion at normal gravity either preventing or vastly complicating measurements. Perversely, this limitation is most evident for fundamental laboratory experiments; few practical combustion phenomena are significantly affected by buoyancy. Thus, we have never observed the most fundamental combustion phenomena - laminar premixed and diffusion flames, heterogeneous flames of particles and surfaces, low-speed turbulent flames, etc. - without substantial buoyant disturbances. This precludes rational merging of theory, where buoyancy is of little interest, and experiments, that always are contaminated by buoyancy, which is the traditional path for developing most areas of science. The current microgravity combustion program seeks to rectify this deficiency using both ground-based and space-based facilities, with experiments involving space-based facilities including: laminar premixed flames, soot processes in laminar jet diffusion flames, structure of laminar and turbulent jet diffusion flames, solid surface combustion, one-dimensional smoldering, ignition and flame spread of liquids, drop combustion, and quenching of panicle-air flames. Unfortunately, the same features that make microgravity attractive for fundamental combustion experiments, introduce new fire and explosion hazards that have no counterpart on earth. For example, microgravity can cause broader flammability limits, novel regimes of flame spread, enhanced effects of flame radiation, slower fire detector response, and enhanced combustion upon injecting fire extinguishing agents, among others. On the other hand, spacecraft provide an opportunity to use 'fire-safe' atmospheres due to their controlled environment. Investigation of these problems is just beginning, with specific fire safety experiments supplementing the space based fundamental experiments listed earlier; thus, much remains to be done to develop an adequate technology base for fire and explosion safety considerations for spacecraft.
Combustion energy of fullerene soot
Man, Naoki; Nagano, Yatsuhisa; Kiyobayashi, Tetsu; Sakiyama, Minoru (Osaka Univ., Toyonaka (Japan))
The standard energy of combustion of fullerene soot generated in arc discharge was determined to be [minus]36.0 [+-] 0.5 kJ g[sup [minus]1] by oxygen-bomb combustion calorimetry. The value was much closer to those of C[sub 60] and C[sub 70] than that of graphite. This result provides an energetic reason for the remarkable yield of fullerenes in arc discharge and supports the mechanism of fullerene formation, where fullerenes are the lowest energy products. Fullerene onion formation is interpreted in terms of energy relaxation of the fullerene soot. 20 refs., 1 tab.
Combustion Group Group members
Wang, Wei
Combustion Group Group members: Thierry Poinsot, Emilien Courtine, Luc Vervisch, Benjamin Farcy 2014 #12;Combustion Group Combustion Physics and Modeling Pollutants, Emissions, and Soot Formation Thermoacoustics and Combustion Dynamics Research focus ž Examine mechanisms responsible for flame stabilization
NASA Microgravity Combustion Science Program
NASA Technical Reports Server (NTRS)
King, Merrill K.
Combustion is a key element of many critical technologies used by contemporary society. For example, electric power production, home heating, surface and air transportation, space propulsion, and materials synthesis all utilize combustion as a source of energy. Yet, although combustion technology is vital to our standard of living, it poses great challenges to maintaining a habitable environment. For example, pollutants, atmospheric change and global warming, unwanted fires and explosions, and the incineration of hazardous wastes are major problem areas which would benefit from improved understanding of combustion. Effects of gravitational forces impede combustion studies more than most other areas of science since combustion involves production of high-temperature gases whose low density results in buoyant motion, vastly complicating the execution and interpretation of experiments. Effects of buoyancy are so ubiquitous that their enormous negative impact on the rational development of combustion science is generally not recognized. Buoyant motion also triggers the onset of turbulence, yielding complicating unsteady effects. Finally, gravity forces cause particles and drops to settle, inhibiting deconvoluted studies of heterogeneous flames important to furnace, incineration and power generation technologies. Thus, effects of buoyancy have seriously limited our capabilities to carry out 'clean' experiments needed for fundamental understanding of flame phenomena. Combustion scientists can use microgravity to simplify the study of many combustion processes, allowing fresh insights into important problems via a deeper understanding of elemental phenomena also found in Earth-based combustion processes and to additionally provide valuable information concerning how fires behave in microgravity and how fire safety on spacecraft can be enhanced.
NASA Technical Reports Server (NTRS)
Corrigan, Jackie
A method of energy production that is capable of low pollutant emissions is fundamental to one of the four pillars of NASA s Aeronautics Blueprint: Revolutionary Vehicles. Bubble combustion, a new engine technology currently being developed at Glenn Research Center promises to provide low emissions combustion in support of NASA s vision under the Emissions Element because it generates power, while minimizing the production of carbon dioxide (CO2) and nitrous oxides (NOx), both known to be Greenhouse gases. and allows the use of alternative fuels such as corn oil, low-grade fuels, and even used motor oil. Bubble combustion is analogous to the inverse of spray combustion: the difference between bubble and spray combustion is that spray combustion is spraying a liquid in to a gas to form droplets, whereas bubble combustion involves injecting a gas into a liquid to form gaseous bubbles. In bubble combustion, the process for the ignition of the bubbles takes place on a time scale of less than a nanosecond and begins with acoustic waves perturbing each bubble. This perturbation causes the local pressure to drop below the vapor pressure of the liquid thus producing cavitation in which the bubble diameter grows, and upon reversal of the oscillating pressure field, the bubble then collapses rapidly with the aid of the high surface tension forces acting on the wall of the bubble. The rapid and violent collapse causes the temperatures inside the bubbles to soar as a result of adiabatic heating. As the temperatures rise, the gaseous contents of the bubble ignite with the bubble itself serving as its own combustion chamber. After ignition, this is the time in the bubble s life cycle where power is generated, and CO2, and NOx among other species, are produced. However, the pollutants CO2 and NOx are absorbed into the surrounding liquid. The importance of bubble combustion is that it generates power using a simple and compact device. We conducted a parametric study using CAVCHEM, a computational model developed at Glenn, that simulates the cavitational collapse of a single bubble in a liquid (water) and the subsequent combustion of the gaseous contents inside the bubble. The model solves the time-dependent, compressible Navier-Stokes equations in one-dimension with finite-rate chemical kinetics using the CHEMKIN package. Specifically, parameters such as frequency, pressure, bubble radius, and the equivalence ratio were varied while examining their effect on the maximum temperature, radius, and chemical species. These studies indicate that the radius of the bubble is perhaps the most critical parameter governing bubble combustion dynamics and its efficiency. Based on the results of the parametric studies, we plan on conducting experiments to study the effect of ultrasonic perturbations on the bubble generation process with respect to the bubble radius and size distribution.
Lack of enhanced preservation of organic matter in sediments under the oxygen minimum on the Oman Margin
NASA Astrophysics Data System (ADS)
Pedersen, T. F.; Shimmield, G. B.; Price, N. B.
The impingement of oxygen minima on continental margins is widely thought to promote the accumulation of sedimentary facies enriched in well-preserved organic matter. It is shown here, however, that such a relationship does not clearly apply to the productive Oman Margin in the Arabian Sea, which hosts one of the most severe oxygen minima in the oceans. Measurements made on the 0-1 cm depth interval from fourteen box cores collected from the outer shelf-upper continental slope area off Oman show that (1) deposited organic matter is overwhelmingly of marine origin, (2) there is no significant correlation between the abundance of sedimentary organic carbon (C org) and the bottom- water O 2 concentration, (3) there is no relation between the sedimentary C org:N ratio and bottom-water O 2, (4) there is no correlation between the hydrogen index (HI) of the organic matter and bottom water oxygen. There are, however, significant correlations between the C org:N ratio and the I:C org, Cr:Al, and Zr:Al ratios, as well as between the C org:N ratio and the hydrogen index. These relationships are interpreted as being the result of winnowing and attendant reworking which produce a progressive increase in the C org:N ratio and a decrease in the HI and the I:C org ratio as organic matter becomes progressively degraded. Commensurate rises in the Cr:Al and Zr:Al ratios result from the increased proportion of heavy minerals associated with winnowed lag deposits. Overall, these data suggest that the bottom water oxygen concentration has little effect in governing either the distribution or the degree of preservation of organic matter on this margin. Thus, the generally high but spatially variable C org content of the sediments on the Oman Margin may not reflect the occurrence of an oxygen minimum but instead be the result of a high settling flux of organic matter, supported by monsoon-driven upwelling, and post-depositional redistribution of the organic material by hydrodynamic influences.
Riccardi, R. C.
. There are many opportunities to improve combustion system efficiency. However, there is no single correct way to maximize efficiency. Each technique must be evaluated and compared before a final selection is made. You have a choice of many energy saving systems...
Digital image processing applications in the ignition and combustion of char/coal particles
Kharbat, Esam Tawfiq
importance to understand the ignition and combustion processes of coal and oil sprays. While the previous studies conducted in this field assumed the ISOlated Particle Combustion (ISOC) model, for the interpretaflon of experimental data and for analytical.... ) Oxygen Products Heterogeneous Coal Particle Combusrion Figure 2. Illustration of Interactive Combustion However, it is important at this point to realize the differences in the processes involved in the combustion of oil drops and the combustion...
Internal Combustion Engine Flows
NASA Astrophysics Data System (ADS)
McCleney, Amy; Puzinauskas, Paul; Gibson, Kendrick
An automobile engine's performance can be enhanced by a more complete combustion reaction which results in less fuel consumption and lower emissions. The combustion improvement can be accomplished through an increase in turbulence from tumble flow, a circulatory motion inside the cylinder. In previous research, this increase is created by changing the intake ports on the engine so the flow is more precisely directed in the cylinder. In this study, the following three experiments were conducted: a detailed vane characterization experiment to direct the flow; a study of the effect of the piston shape on the flow; and a seeding settling experiment to determine experimentation quality. These experiments offer insight into the flow structure inside the test cylinder, as observed using particle image velocimetry and impulse swirl meter testing.
Decreased oxygen concentration in the glacial abyssal subarctic Pacific - evidence for enhanced oceanic carbon sequestration during cold periods?
NASA Astrophysics Data System (ADS)
Jaccard, S. L.; Galbraith, E. D.; Sigman, D. M.; Haug, G. H.; Francois, R.; Pedersen, T. F.
Measurements of benthic foraminiferal Cd/Ca have indicated that the glacial-interglacial change in deep North Pacific PO4 concentration was minimal, which has been taken by some workers as a sign that the biological pump did not store more carbon in the deep glacial ocean. Here we present sedimentary redox- sensitive trace metal (Mn, Mo, U) records from ODP Site 882 (NW subarctic Pacific, water depth 3,244 m) to make inferences about changes in deep North Pacific oxygenation - and thus respired carbon storage - across glacial Terminations I and II. These observations are complemented with 230Th-normalized biogenic barium and opal measurements as indicators for past organic carbon export to separate the influences of deep-water oxygen concentration and sedimentary organic carbon respiration on the redox state of the sediment. Our results suggest that the deep subarctic Pacific water mass was depleted in oxygen during glacial maxima, though it was not anoxic. We reconcile our results with the existing benthic foraminiferal Cd/Ca by invoking a decrease in the fraction of the deep ocean nutrient inventory that was preformed, rather than remineralized. This change would have corresponded to an increase in the deep Pacific storage of respired carbon, which would have lowered atmospheric carbon dioxide (CO2) by sequestering CO2 away from the atmosphere and by increasing ocean alkalinity through a transient dissolution event in the deep sea. Preliminary calculations show that the magnitude of change in preformed nutrients suggested by the North Pacific data would have accounted for a substantial portion of the observed decrease in glacial atmospheric pCO2.
Oxygen therapy is a treatment that provides you with extra oxygen. Oxygen is a gas that your body needs to function. Normally, your lungs absorb ... in your home. A different kind of oxygen therapy is called hyperbaric oxygen therapy. It uses oxygen ...
Analytical Model for the Diffusion Process in a In-Situ Combustion Tube
NASA Astrophysics Data System (ADS)
Gutierrez, Patricia; Reyes, Adrian
The in-situ combustion process (ISC) is basically an air or oxygen enriched gas injection oil recovery process, inside an extraction well. In contrast to a conventional gas injection process, an ISC process consists in using heat to create a combustion front that raises the fuel temperature, decreasing its viscosity, making extraction easier. The oil is taken toward the productor by means of a vigorous gas thrust as well as a water thrust. To improve and enhance this technique in the field wells, it has been widely perform experimental laboratory tests, in which an in-situ combustion tube is designed to simulate the extraction process. In the present work we propose to solve analytically the problem, with a parabolic partial differential equation associated to the convection-diffusion phenomenon, equation which describes the in-situ combustion process. The whole mathematical problem is established by completing this equation with the correspong boundary and initial conditions, the thickness of the combustion zone, flow velocity, and more parameters. The theoretically obtained results are compared with those reported in literature. We further, fit the parameter of our model to the mentioned data taken from the literature.
Enhanced magnetization of nanoparticles of Mg x Fe(3- x)O4 (0.5? x?1.5) synthesized by combustion reaction
NASA Astrophysics Data System (ADS)
Franco, Adolfo; Pereira Alves, Thiago Eduardo; de Oliveira Lima, EmÝlia Celma; da Silva Nunes, Eloisa; Zapf, Vivien
For the first time nanocrystalline magnetic particles of Mg x Fe(3- x)O4 with x ranging from 0.5 to 1.5 have been synthesized by a combustion reaction method using iron nitrate Fe(NO3)3.9H2O, magnesium nitrate Mg(NO3)2.6H2O, and urea CO(NH2)2 as fuel without intermediate decomposition and/or calcining steps. X-ray diffraction patterns of all systems showed broad peaks consistent with cubic inverse spinel structure of MgFe2O4. The absence of extra reflections in the diffraction patterns of as-prepared materials ensures the phase purity. The mean crystallite sizes determined from the prominent (311) peak of the diffraction using Scherrerĺs equation and transmission electron microscopy micrographs were c.a. 40 nm with spherical morphology. Fourier transform infrared spectra of the as-prepared material showed traces of organic and metallic salt by-products; however, these could be removed by washing with deionized water. Typical hysteresis curves were obtained for all specimens in magnetic field up to 14 T between 4 and 340 K. The saturation magnetization was 48.3 emu/g and 31.3 emu/g, 44.8 emu/g, and 28.4 emu/g for x=1.0 and 0.8 at 4 K and 340 K, respectively. The saturation magnetization, M s , of nanoparticles of the MgFe2O4 specimen is about 50% higher when compared to the bulk. The enhanced magnetization measured in our nanoparticles MgFe2O4 specimens may be attributed to the uncompensated magnetic moment of iron ions between the A- and B-sites, i.e., changes in the inversion factor. Our magnetization results of MgFe2O4 specimens are comparable to the existing data for the same compound but with different particle size and prepared by different synthesis methods.
Compound internal combustion and external combustion engine
A compound engine is described comprising at least one internal combustion cylinder having an inlet and an outlet and one external combustion cylinder having an inlet and an outlet, each of the combustion cylinders having a reciprocable piston therein coupled to a common utilization output shaft, heat exchanger means associated with the external combustion cylinder for transferring heat to a
Hyperbaric oxygen preconditioning attenuates hyperglycemia-enhanced hemorrhagic transformation by inhibiting matrix metalloproteinases in focal cerebral ischemia in rats
Soejima, Yoshiteru; Hu, Qin; Krafft, Paul R.; Fujii, Mutsumi; Tang, Jiping; Zhang, John H.
Hyperglycemia dramatically aggravates brain infarct and hemorrhagic transformation (HT) after ischemic stroke. Oxidative stress and matrix metalloproteinases (MMPs) play an important role in the pathophysiology of HT. Hyperbaric oxygen preconditioning (HBO-PC) has been proved to decrease oxidative stress and be neuroprotective in experimental stroke models. The present study determined whether HBO-PC would ameliorate HT by a pre-ischemic increase of reactive oxygen species (ROS) generation, and a suppression of MMP-2 and MMP-9 in hyperglycemic middle cerebral artery occlusion (MCAO) rats. Rats were pretreated with HBO (100% O2, 2.5 atmospheres absolute) 1 h daily for 5 days before MCAO. Acute hyperglycemia was induced by an injection of 50% dextrose. Neurological deficits, infarction volume and hemorrhagic volume were assessed 24 h and 7 days after ischemia. ROS scavenger n-acetyl cysteine (NAC), hypoxia-inducible factor-1? (HIF-1?) inhibitor 2-methoxyestradiol (2ME2) and activator cobalt chloride (CoCl2), and MMPs inhibitor SB-3CT were administrated for mechanism study. The activity of MMP-2 and MMP-9, and the expression HIF-1? were measured. HBO-PC improved neurological deficits, and reduced hemorrhagic volume; the expression of HIF-1? was significantly decreased, and the activity of MMP-2 and MMP-9 was reduced by HBO-PC compared with vehicle group. Our results suggested that HBO-PC attenuated HT via decreasing HIF-1? and its downstream MMP-2 and MMP-9 in hyperglycemic MCAO rats. PMID:23537951
NASA Astrophysics Data System (ADS)
Gamba, Mirko
Combustion in the supersonic regime presents several challenges over what the low-speed counterpart admits. Here we will review some of these challenges, and we will describe some of the key features of one of the canonical flow fields in supersonic combustion: the reacting transverse jet in a supersonic crossflow (JISCF). From a practical standpoint, the key challenges that limit our control of this combustion regime are fast mixing, robust flame holding and stability. In turn, these aspects are controlled by the complex effects introduced by chemistry, compressibility, shocks and shock/flow interactions, turbulence and the underlying coupling among them. Some of their properties will be discussed here. In particular, for a JISCF in a Mach 2.4 high enthalpy crossflow, the reaction zone structure, its dependence on near-wall events, boundary layer, and shock/boundary layer interaction will be described. We will demonstrate the paramount importance of the coupling between boundary layers and compressibility to provide mechanisms for flame stabilization at the wall. Mixing characteristics, overall structure, and the link to global parameters (momentum flux, velocity and density ratios) that characterize the JISCF, and possibly free shear supersonic flows in general, will also be highlighted from non-reacting experiments. Combustion in the supersonic regime presents several challenges over what the low-speed counterpart admits. Here we will review some of these challenges, and we will describe some of the key features of one of the canonical flow fields in supersonic combustion: the reacting transverse jet in a supersonic crossflow (JISCF). From a practical standpoint, the key challenges that limit our control of this combustion regime are fast mixing, robust flame holding and stability. In turn, these aspects are controlled by the complex effects introduced by chemistry, compressibility, shocks and shock/flow interactions, turbulence and the underlying coupling among them. Some of their properties will be discussed here. In particular, for a JISCF in a Mach 2.4 high enthalpy crossflow, the reaction zone structure, its dependence on near-wall events, boundary layer, and shock/boundary layer interaction will be described. We will demonstrate the paramount importance of the coupling between boundary layers and compressibility to provide mechanisms for flame stabilization at the wall. Mixing characteristics, overall structure, and the link to global parameters (momentum flux, velocity and density ratios) that characterize the JISCF, and possibly free shear supersonic flows in general, will also be highlighted from non-reacting experiments. Sponsored by DoE PSAAP at Stanford University.
Combustion effects of asymmetric valve strategies
This article discusses electrohydraulic valve actuation system developed by Lotus Engineering to reduce the development time involved in optimizing an engine combustion system and valve timing. To enhance in-cylinder turbulence, and hence the rate of combustion, asymmetric valve strategies were investigated using an engine fitted with AVT. The cylinder bore size of this engine was reduced to represent contemporary European saloon car powerplants better, and this engine was then used to optimize combustion systems. The cylinder head was extensively airflow tested to define its tumble, swirl, and flow characteristics. It was then fitted to the engine, and dynamometer tested to quantify the effects of these characteristics on combustion.
Increases in reactive oxygen species enhance vascular endothelial cell migration through a mechanism dependent on the transient receptor potential melastatin 4 ion channel.
Sarmiento, Daniela; Montorfano, Ignacio; Cerda, Oscar; Cßceres, Mˇnica; Becerra, Alvaro; Cabello-Verrugio, Claudio; Elorza, Alvaro A; Riedel, Claudia; Tapia, Pablo; Velßsquez, Luis A; Varela, Diego; Simon, Felipe
A hallmark of severe inflammation is reactive oxygen species (ROS) overproduction induced by increased inflammatory mediators secretion. During systemic inflammation, inflammation mediators circulating in the bloodstream interact with endothelial cells (ECs) raising intracellular oxidative stress at the endothelial monolayer. Oxidative stress mediates several pathological functions, including an exacerbated EC migration. Because cell migration critically depends on calcium channel-mediated Ca(2+) influx, the molecular identification of the calcium channel involved in oxidative stress-modulated EC migration has been the subject of intense investigation. The transient receptor potential melastatin 4 (TRPM4) protein is a ROS-modulated non-selective cationic channel that performs several cell functions, including regulating intracellular Ca(2+) overload and Ca(2+) oscillation. This channel is expressed in multiple tissues, including ECs, and contributes to the migration of certain immune cells. However, whether the TRPM4 ion channel participates in oxidative stress-mediated EC migration is not known. Herein, we investigate whether oxidative stress initiates or enhances EC migration and study the role played by the ROS-modulated TRPM4 ion channel in oxidative stress-mediated EC migration. We demonstrate that oxidative stress enhances, but does not initiate, EC migration in a dose-dependent manner. Notably, we demonstrate that the TRPM4 ion channel is critical in promoting H2O2-enhanced EC migration. These results show that TRPM4 is a novel pharmacological target for the possible treatment of severe inflammation and other oxidative stress-mediated inflammatory diseases. PMID:24518820
Toward Enhanced Photocatalytic Oxygen Evolution: Synergetic Utilization of Plasmonic Effect and Schottky Junction via Interfacing Facet Selection.
Bai, Song; Li, Xiyu; Kong, Qiao; Long, Ran; Wang, Chengming; Jiang, Jun; Xiong, Yujie
A metal-semiconductor-metal ternary hybrid structure with two well-designed interfaces is developed to synergize a Schottky junction with the plasmonic effect. The designed hybrid structure exhibits dramatically enhanced perform-ance in full-spectrum photocatalysis. PMID:25925245
Holcomb, Gordon R. [NETL
The activity reported in this presentation is to provide the mechanical and physical property information needed to allow rational design, development and/or choice of alloys, manufacturing approaches, and environmental exposure and component life models to enable oxy-fuel combustion boilers to operate at Ultra-Supercritical (up to 650{degrees}C & between 22-30 MPa) and/or Advanced Ultra-Supercritical conditions (760{degrees}C & 35 MPa).
Enhancement of the acrolein-induced production of reactive oxygen species and lung injury by GADD34.
Sun, Yang; Ito, Sachiko; Nishio, Naomi; Tanaka, Yuriko; Chen, Nana; Liu, Lintao; Isobe, Ken-ichi
Chronic obstructive pulmonary disease (COPD) is characterized by lung destruction and inflammation. As a major compound of cigarette smoke, acrolein plays a critical role in the induction of respiratory diseases. GADD34 is known as a growth arrest and DNA damage-related gene, which can be overexpressed in adverse environmental conditions. Here we investigated the effects of GADD34 on acrolein-induced lung injury. The intranasal exposure of acrolein induced the expression of GADD34, developing the pulmonary damage with inflammation and increase of reactive oxygen species (ROS). Conversely, the integrality of pulmonary structure was preserved and the generation of ROS was reduced in GADD34-knockout mice. Acrolein-induced phosphorylation of eIF2? in GADD34-knockout epithelial cells by shRNA protected cell death by reducing misfolded protein-caused oxidative stress. These data indicate that GADD34 participates in the development of acrolein-induced lung injury. PMID:25821552
Enhancement of the Acrolein-Induced Production of Reactive Oxygen Species and Lung Injury by GADD34
Sun, Yang; Ito, Sachiko; Nishio, Naomi; Tanaka, Yuriko; Chen, Nana; Isobe, Ken-ichi
Chronic obstructive pulmonary disease (COPD) is characterized by lung destruction and inflammation. As a major compound of cigarette smoke, acrolein plays a critical role in the induction of respiratory diseases. GADD34 is known as a growth arrest and DNA damage-related gene, which can be overexpressed in adverse environmental conditions. Here we investigated the effects of GADD34 on acrolein-induced lung injury. The intranasal exposure of acrolein induced the expression of GADD34, developing the pulmonary damage with inflammation and increase of reactive oxygen species (ROS). Conversely, the integrality of pulmonary structure was preserved and the generation of ROS was reduced in GADD34-knockout mice. Acrolein-induced phosphorylation of eIF2? in GADD34-knockout epithelial cells by shRNA protected cell death by reducing misfolded protein-caused oxidative stress. These data indicate that GADD34 participates in the development of acrolein-induced lung injury. PMID:25821552
Neutrophil killing of human umbilical vein endothelial cells is oxygen radical-mediated and enhanced by TNF-. alpha
Dame, M.K.; Varani, J.; Weinberg, J.M.; Ward, P.A. (Univ. of Michigan, Ann Arbor (United States))
Human umbilical vein endothelial cells are sensitive to killing by activated human neutrophils. Killing is inhibited in the presence of catalase and deferoxamine mesylate but not soybean trypsin inhibitor. Reagent hydrogen peroxide can substitute for activated neutrophils in producing endothelial cell injury. These data suggest that lethal injury is due to the production of oxygen radicals by activated neutrophils. In these respects, the human umbilical vein endothelial cells are similar to rat pulmonary artery endothelial cells in that pretreatment with TNF-{alpha} increases sensitivity to injury by activated neutrophils. In part, the increased endothelial cell sensitivity to killing by neutrophils may be due to up-regulation of surface adhesion molecules. However, it was observed that cells passaged more than two times in culture did not demonstrate increased killing after treatment with TNF-{alpha} while up-regulation of neutrophil adhesion could be detected through several additional passages. Although the human umbilical vein endothelial cells are qualitatively similar to rat pulmonary artery endothelial cells in their sensitivity to killing, they are quantitatively much more resistant. What accounts for the relative resistance of the human umbilical vein endothelial cells is not fully understood. In the rat pulmonary artery endothelial cells, killing is known to be dependent on an intraendothelial source of iron. Pre-treatment of the human umbilical vein endothelial cells with 8-hydroxyquinoline-bound iron increased their sensitivity to oxidant injury. These data suggest that the availability of iron within the human umbilical vein endothelial cells may be a limiting factor in sensitivity to oxygen radical-mediated injury.
Continuous-flow Mass Production of Silicon Nanowires via Substrate-Enhanced Metal-Catalyzed Electroless Etching of Silicon with Dissolved Oxygen as an Oxidant
NASA Astrophysics Data System (ADS)
Hu, Ya; Peng, Kui-Qing; Liu, Lin; Qiao, Zhen; Huang, Xing; Wu, Xiao-Ling; Meng, Xiang-Min; Lee, Shuit-Tong
Silicon nanowires (SiNWs) are attracting growing interest due to their unique properties and promising applications in photovoltaic devices, thermoelectric devices, lithium-ion batteries, and biotechnology. Low-cost mass production of SiNWs is essential for SiNWs-based nanotechnology commercialization. However, economic, controlled large-scale production of SiNWs remains challenging and rarely attainable. Here, we demonstrate a facile strategy capable of low-cost, continuous-flow mass production of SiNWs on an industrial scale. The strategy relies on substrate-enhanced metal-catalyzed electroless etching (MCEE) of silicon using dissolved oxygen in aqueous hydrofluoric acid (HF) solution as an oxidant. The distinct advantages of this novel MCEE approach, such as simplicity, scalability and flexibility, make it an attractive alternative to conventional MCEE methods.
Continuous-flow mass production of silicon nanowires via substrate-enhanced metal-catalyzed electroless etching of silicon with dissolved oxygen as an oxidant.
Hu, Ya; Peng, Kui-Qing; Liu, Lin; Qiao, Zhen; Huang, Xing; Wu, Xiao-Ling; Meng, Xiang-Min; Lee, Shuit-Tong
Silicon nanowires (SiNWs) are attracting growing interest due to their unique properties and promising applications in photovoltaic devices, thermoelectric devices, lithium-ion batteries, and biotechnology. Low-cost mass production of SiNWs is essential for SiNWs-based nanotechnology commercialization. However, economic, controlled large-scale production of SiNWs remains challenging and rarely attainable. Here, we demonstrate a facile strategy capable of low-cost, continuous-flow mass production of SiNWs on an industrial scale. The strategy relies on substrate-enhanced metal-catalyzed electroless etching (MCEE) of silicon using dissolved oxygen in aqueous hydrofluoric acid (HF) solution as an oxidant. The distinct advantages of this novel MCEE approach, such as simplicity, scalability and flexibility, make it an attractive alternative to conventional MCEE methods. PMID:24413157
Enhancement by Tumor Necrosis Factor Alpha of Dengue Virus-Induced Endothelial Cell Production of Reactive Nitrogen and Oxygen Species Is Key to Hemorrhage Development?
Yen, Yu-Ting; Chen, Hseun-Chin; Lin, Yang-Ding; Shieh, Chi-Chang; Wu-Hsieh, Betty A.
Hemorrhage is a severe manifestation of dengue disease. Virus strain and host immune response have been implicated as the risk factors for hemorrhage development. To delineate the complex interplay between the virus and the host, we established a dengue hemorrhage model in immune-competent mice. Mice inoculated intradermally with dengue virus develop hemorrhage within 3 days. In the present study, we showed by the presence of NS1 antigen and viral nuclei acid that dengue virus actively infects the endothelium at 12 h and 24 h after inoculation. Temporal studies showed that beginning at day 2, there was macrophage infiltration into the vicinity of the endothelium, increased tumor necrosis factor alpha (TNF-?) production, and endothelial cell apoptosis in the tissues. In the meantime, endothelial cells in the hemorrhage tissues expressed inducible nitric oxide synthase (iNOS) and nitrotyrosine. In vitro studies showed that primary mouse and human endothelial cells were productively infected by dengue virus. Infection by dengue virus induced endothelial cell production of reactive nitrogen and oxygen species and apoptotic cell death, which was greatly enhanced by TNF-?. NG-Nitro-l-arginine methyl ester and N-acetyl cysteine reversed the effects of dengue virus and TNF-? on endothelial cells. Importantly, hemorrhage development and the severity of hemorrhage were greatly reduced in mice lacking iNOS or p47phox or treatment with oxidase inhibitor, pointing to the critical roles of reactive nitrogen and oxygen species in dengue hemorrhage. PMID:18842737
Wheat Oxophytodienoate Reductase Gene TaOPR1 Confers Salinity Tolerance via Enhancement of Abscisic Acid Signaling and Reactive Oxygen Species Scavenging1[C][W
Dong, Wei; Wang, Mengcheng; Xu, Fei; Quan, Taiyong; Peng, Keqin; Xiao, Langtao; Xia, Guangmin
The 12-oxo-phytodienoic acid reductases (OPRs) are classified into the two subgroups OPRI and OPRII. The latter proteins participate in jasmonic acid synthesis, while the function of the former ones is as yet unclear. We describe here the characterization of the OPRI gene TaOPR1, isolated from the salinity-tolerant bread wheat (Triticum aestivum) cultivar SR3. Salinity stress induced a higher level of TaOPR1 expression in the seedling roots of cv SR3 than in its parental cultivar, JN177. This induction was abolished when abscisic acid (ABA) synthesis was inhibited. The overexpression of TaOPR1 in wheat significantly enhanced the level of salinity tolerance, while its heterologous expression in Arabidopsis alleviated root growth restriction in the presence of salinity and oxidants and raised the sensitivity to ABA. In Arabidopsis, TaOPR1 promoted ABA synthesis and the ABA-dependent stress-responsive pathway, partially rescued the sensitivity of the Arabidopsis aba2 mutant defective in ABA synthesis to salinity, and improved the activities of reactive oxygen species scavengers and the transcription of their encoding genes while reducing malondialdehyde and reactive oxygen species levels. TaOPR1 did not interact with jasmonate synthesis or the jasmonate signaling pathway. Rather than serving purely as an antioxidant, we believe that TaOPR1 acts during episodes of abiotic stress response as a signaling compound associated with the regulation of the ABA-mediated signaling network. PMID:23321418
Chemical Looping Combustion Kinetics
Edward Eyring; Gabor Konya
One of the most promising methods of capturing CO{sub 2} emitted by coal-fired power plants for subsequent sequestration is chemical looping combustion (CLC). A powdered metal oxide such as NiO transfers oxygen directly to a fuel in a fuel reactor at high temperatures with no air present. Heat, water, and CO{sub 2} are released, and after H{sub 2}O condensation the CO{sub 2} (undiluted by N{sub 2}) is ready for sequestration, whereas the nickel metal is ready for reoxidation in the air reactor. In principle, these processes can be repeated endlessly with the original nickel metal/nickel oxide participating in a loop that admits fuel and rejects ash, heat, and water. Our project accumulated kinetic rate data at high temperatures and elevated pressures for the metal oxide reduction step and for the metal reoxidation step. These data will be used in computational modeling of CLC on the laboratory scale and presumably later on the plant scale. The oxygen carrier on which the research at Utah is focused is CuO/Cu{sub 2}O rather than nickel oxide because the copper system lends itself to use with solid fuels in an alternative to CLC called 'chemical looping with oxygen uncoupling' (CLOU).
Role of metal components in Pd?Cu bimetallic catalysts supported on CeO2 for the oxygen-enhanced water gas shift
Kugai, J.; Miller, J. T.; Guo, N.; Song, C. (Chemical Sciences and Engineering Division); ( PSC-USR); (Penn State Univ.)
Catalytic hydrogen production and CO removal in a post-reforming process are critical for low-temperature fuel cell applications. The present study aims at clarifying the role of metal components in bimetallic catalysts for oxygen-enhanced water gas shift (OWGS), wherein a small amount of O{sub 2} is added to H{sub 2}-rich reformate gas to enhance CO shift. Among CeO{sub 2}-supported bimetallic catalysts, Pd-Cu and Pt-Cu combinations were found to show strong synergetic promoting effect in OWGS, which leads to much higher CO conversion and higher H{sub 2} yield than WGS at low temperature around 250 C. Temperature programmed reduction (TPR) showed strong interaction between Pd and Cu in Pd-Cu/CeO{sub 2} by a single reduction peak in contrast to multiple peaks on monometallic Cu/CeO{sub 2}. Extended X-ray absorption fine structure (EXAFS) analysis revealed that such bimetallic Pd-Cu and Pt-Cu form alloy nanoparticles, where noble metal is mainly surrounded by Cu atoms. Oxygen storage capacity (OSC) measurements point to higher resistance of Pd-Cu to oxidation indicating that Pd keeps Cu in reduced state in air pulse condition. From kinetic study, Pd in Pd-Cu was found to promote CO shift, rather than CO oxidation by increasing the number of active sites and by suppressing H{sub 2} activation (that is inherent to monometallic Pd), which minimizes both the inhibition effect of H{sub 2} and the loss of H{sub 2} by oxidation in OWGS. Transient response technique revealed that Cu in Pd-Cu enhances desorption of strongly chemisorbed CO{sub 2} on catalyst surface in contrast to very slow CO{sub 2} desorption from surface of monometallic Pd. Thus, the excellent OWGS activity of Pd-Cu catalyst has been attributed to the complementary roles of the two metals for enhancing CO shift, which is realized by its alloy structure and the accompanying strong interaction between metal components.
Enhanced oxygen storage capacity of cerium oxides in CeO sub 2 /La sub 2 O sub 3 /Al sub 2 O sub 3 containing precious metals
Miki, Takeshi; Ogawa, Takao, Haneda, Masaaki; Kakuta, Noriyoshi; Ueno, Akifumi (Toyohashi Univ. of Technology (Japan)); Tateishi, Syuji; Matsuura, Shinji; Sato, Masayasu (Cataler Industrial Co., Sizuoka (Japan))
Effects of the addition of precious metals (PM; Pt, Rh) on CeO{sub 2}/Al{sub 2}O{sub 3} and CeO{sub 2}/La{sub 2}O{sub 3}/Al{sub 2}O{sub 3} were confirmed to enhance the oxygen storage capacities (OSC). Increments in the OSC of the added CeO{sub 2}/La{sub 2}O{sub 3}/Al{sub 2}O{sub 3} catalysts were much greater than those in the OSC of the PM added CeO{sub 2}/Al{sub 2}O{sub 3}. The enhanced OSC is ascribed to the interaction between PM and a CeO{sub 2}-La{sub 2}O{sub 3} solid solution formed during the catalyst preparation. No enhancements in the OSC were observed on physical mixing of CeO{sub 2}/La{sub 2}O{sub 3}/Al{sub 2}O{sub 3} and Pt-Rh/Al{sub 2}O{sub 3}, although the composition ratio of PM:CeO{sub 2}:La{sub 2}O{sub 3} is the same as that in the PM added CeO{sub 2}/La{sub 2}O{sub 3}/Al{sub 2}O{sub 3}. This indicates that the intimate contacts between the precious metals and CeO{sub 2} particles dispersed on Al{sub 2}O{sub 3} are essential for the enhanced OSC of cerium oxides.
NASA Technical Reports Server (NTRS)
Liang, Pak-Yan; Jeng, San-Mou; Litchford, Ronald
The central purpose of this project is the improvement of liquid-fueled rocket motor design technology in order to assist the establishment of economical commercial access to space through the development of engines with enhanced performance and reliability. Specific research effort is focused on spray physics and associated combustion instability phenomena. Results concerning high pressure droplet gasification model, droplet turbulent dispersion model, and spray atomization model will contribute to the development of new computational tools for design of stable liquid propellant rocket engines.
High Selectivity Oxygen Delignification
Lucian A. Lucia
Project Objective: The objectives of this project are as follows: (1) Examine the physical and chemical characteristics of a partner mill pre- and post-oxygen delignified pulp and compare them to lab generated oxygen delignified pulps; (2) Apply the chemical selectivity enhancement system to the partner pre-oxygen delignified pulps under mill conditions (with and without any predetermined amounts of carryover) to determine how efficiently viscosity is preserved, how well selectivity is enhanced, if strength is improved, measure any yield differences and/or bleachability differences; and (3) Initiate a mill scale oxygen delignification run using the selectivity enhancement agent, collect the mill data, analyze it, and propose any future plans for implementation.
Stabilizing and enhancing activity of Ag as a catalyst for oxygen redaction reaction on hydrogen fuel cell cathodes
NASA Astrophysics Data System (ADS)
Stolbov, Sergey; Alcantara Ortigoza, Marisol
Progress in searching for cost-effective and highly active catalysts for the oxygen reduction reaction (ORR) on hydrogen fuel cell cathodes is hindered by the fact that only a few elements (expensive and scarce Pt, Ir, Au) do not dissolve in the reaction environment (acidic medium at the expected operating potential +0.8 to +1.0 V vs SHE). Yet, in this work, we explore silver as an active element for the ORR catalysts. Although the dissolution potential (DP) of elemental Ag is 0.8 V, we rely on our finding that binding of a metal monolayer (ML) to a reactive substrate can significantly increase its DP. Using our approach, we select Ag/Ru/W, Ag/Nb, and Ag/Ta as promising candidates for the ORR catalysts (where Ag and Ru are MLs). Our evaluation of DP within density functional theory (DFT) shows that, indeed, in the selected structures, DP of Ag significantly increases as compared to that of Ag(111) and, in the case of Ag/Nb, even exceeds that of Pt. The ORR free-energy diagrams calculated within DFT suggest that the above systems are more active toward ORR than Pt. We thus predict here three highly active and truly cost-effective ORR catalysts. Progress in searching for cost-effective and highly active catalysts for the oxygen reduction reaction (ORR) on hydrogen fuel cell cathodes is hindered by the fact that only a few elements (expensive and scarce Pt, Ir, Au) do not dissolve in the reaction environment (acidic medium at the expected operating potential +0.8 to +1.0 V vs SHE). Yet, in this work, we explore silver as an active element for the ORR catalysts. Although the dissolution potential (DP) of elemental Ag is 0.8 V, we rely on our finding that binding of a metal monolayer (ML) to a reactive substrate can significantly increase its DP. Using our approach, we select Ag/Ru/W, Ag/Nb, and Ag/Ta as promising candidates for the ORR catalysts (where Ag and Ru are MLs). Our evaluation of DP within density functional theory (DFT) shows that, indeed, in the selected structures, DP of Ag significantly increases as compared to that of Ag(111) and, in the case of Ag/Nb, even exceeds that of Pt. The ORR free-energy diagrams calculated within DFT suggest that the above systems are more active toward ORR than Pt. We thus predict here three highly active and truly cost-effective ORR catalysts. This work was supported by NSF under Grant CBET-1249134
Optical fiber system for combustion quality analysis in power boilers
NASA Astrophysics Data System (ADS)
Wojcik, Waldemar; Surtel, Wojciech; Smolarz, Andrzej; Kotyra, Andrzej; Komada, Pawel
The introduction of low emission techniques of combustion caused side-effects like oxygen lean corrosion. It also enforced more precise management of technological air, better coal milling and application of devices for combustion process monitoring. In the article authors presented their own solution of optical fiber system for combustion quality evaluation, already operating on power boiler type OP-650. Its functionality was described together with selected results of measurements. Directions of further development of the system were also indicated.
Experimental investigation on plasma-assisted combustion characteristics of premixed propane/air mixture
NASA Astrophysics Data System (ADS)
Liu, Xingjian; He, Liming; Yu, Jinlu; Zeng, Hao; Jin, Tao
A detailed study on the plasma-assisted combustion (PAC) characteristics of premixed propane/air mixture is presented. The PAC is measured electrically, as well as optically with a multichannel spectrometer. The characteristics are demonstrated by stable combustion temperature and combustion stability limits, and the results are compared with conventional combustion (CC). Stable combustion temperature measurements show that the introduction of PAC into combustion system can increase the stable combustion temperature, and the increment is more notable with an increase of discharge voltage. Besides, the rich and weak limits of combustion stability are both enlarged when plasma is applied into the combustion process and the increase of discharge voltage results in the expansion of combustion stability limits as well. The measurements of temperature head and emission spectrum illustrate that the kinetic enhancement caused by reactive species in plasma is the main enhancement pathway for current combustion system.
Reactive Oxygen Species Production Mediated by Humic-like Substances in Atmospheric Aerosols: Enhancement Effects by Pyridine, Imidazole, and Their Derivatives.
Dou, Jing; Lin, Peng; Kuang, Bin-Yu; Yu, Jian Zhen
Ambient particulate matter (PM) can cause adverse health effects via their ability to produce reactive oxygen species (ROS). Humic-like substances (HULIS), a complex mixture of amphiphilic organic compounds, have been demonstrated to contain the majority of redox activity in the water-extractable organic fraction of PM. Reduced organic nitrogen compounds, such as alkaloids resulting from biomass burning emissions, are among HULIS constituents. In this study, we examined the redox activities of pyridine, imidazole and their alkyl derivatives using a cell-free dithiothreitol (DTT) assay under simulated physiological conditions (37 ░C, pH = 7.40). These compounds were found to have little redox activity on their own as measured by the DTT assay, but they enhanced ROS generation catalyzed by 1,4-naphthoquinone (as a model quinone compound) and HULIS isolated from multiple aerosol samples. The enhancement effect by the individual nitrogen-containing bases was determined to be proportional to their amount in the assay solutions. It is postulated that the underlying mechanism involves the unprotonated N atom acting as a H-bonding acceptor to facilitate hydrogen-atom transfer in the ROS generation cycle. The enhancement capability was found to increase with their basicity (i.e., pKa of their conjugated acids, BH(+)), consistent with the proposed mechanism for enhancement. Among the imidazole homologues, a linear relationship was observed between the enhancement factors (in log scale) of the unprotonated form of the imidazole compounds (B) and the pKa of their conjugated acids (BH(+)). This relationship predicts that the range of alkylimidazole homologues (C6-C13) observed in atmospheric HULIS would be 1.5-4.4 times more effective than imidazole in facilitating HULIS-mediated ROS generation. Our work reveals that the ability of atmospheric PM organics to catalyze generation of ROS in cells could be affected by coexisting redox inactive organic constituents and suggests further work deploying multiple assays be conducted to quantify redox capabilities and enhancement effects of the HULIS components. PMID:25961507
This thesis describes the design and development of a combustion bomb which is capable of simulating diesel combustion without the need to heat the bomb to high temperatures. A lean precharge composed of acetylene, nitrogen and oxygen is inducted into the bomb through a shrouded valve and burned to simulate conditions produced by the compression stroke in an actual diesel
Mathematical model of chalcocite particle combustion
A. A. Shook; G. G. Richards; J. K. Brimacombe
A mathematical model has been developed to simulate the combustion of a single chalcocite particle (particle diameter between\\u000a 10 and 100 microns) in air, oxygen, and oxygen-SO2 mixtures. Neglecting temperature and composition gradients within the particle, the model computes the thermal and compositional\\u000a changes of the particle as a function of time. Five chemical reactions were considered to describe the
Caspase inhibition augmented oridonin-induced cell death in murine fibrosarcoma l929 by enhancing reactive oxygen species generation.
Wu, Jin-Nan; Huang, Jian; Yang, Jia; Tashiro, Shin-Ichi; Onodera, Satoshi; Ikejima, Takashi
Oridonin, a diterpenoid isolated from Rabdosia rubescences, has been reported to have antitumor effects. In this study, the growth-inhibitory activity of oridonin for L929 cells was exerted in a time-and dose-dependent manner. After treatment with oridonin for 24 h, L929 cells underwent both apoptosis and necrosis as measured by an lactate dehydrogenase (LDH) activity-based assay. A rapid generation of reactive oxygen species (ROS) was triggered by oridonin, and subsequently up-regulation of phospho-p53 (ser 15) expression and an increased expression ratio of Bax/Bcl-2 was observed. Furthermore, there was a significant fall in mitochondrial membrane potential (MMP) and increase in caspase-3 activity after exposure to oridonin for 24 h. Surprisingly, the pan-caspase inhibitor z-VAD-fmk and caspase3 inhibitor z-DEVD-fmk rendered L929 cells more sensitive to oridonin, rather than preventing oridonin-induced cell death. Oridonin and z-VAD-fmk co-treatment not only resulted in an even higher ROS production, but also made a more significant reduction in the MMP. Pretreatment of ROS scavenger N-acetylcysteine (NAC) led to a complete inhibition of oridonin-induced cell death, intracellular ROS generation, and MMP collapse. NAC treatment also reversed the potentiation of cell death by the pan-caspase inhibitor z-VAD-fmk. Taken together, these observations showed that oridonin-induced cell death in L929 cells involved intracellular ROS generation, activation of phospho-p53 (ser 15), and up-regulation of the Bax/Bcl-2 ratio; and the augmented cell death by z-VAD-fmk was dependent on an increased ROS production. PMID:18818479
Enhanced Lung Injury and Delayed Clearance of Pneumocystis carinii in Surfactant Protein A-Deficient Mice: Attenuation of Cytokine Responses and Reactive Oxygen-Nitrogen Species
Atochina, Elena N.; Beck, James M.; Preston, Angela M.; Haczku, Angela; Tomer, Yaniv; Scanlon, Seth T.; Fusaro, Trevor; Casey, John; Hawgood, Samuel; Gow, Andrew J.; Beers, Michael F.
Surfactant protein A (SP-A), a member of the collectin family, selectively binds to Pneumocystis carinii and mediates interactions between pathogen and host alveolar macrophages in vitro. To test the hypothesis that mice lacking SP-A have delayed clearance of Pneumocystis organisms and enhanced lung injury, wild-type C57BL/6 (WT) and SP-A-deficient mice (SP-A?/?) with or without selective CD4+-T-cell depletion were intratracheally inoculated with Pneumocystis organisms. Four weeks later, CD4-depleted SP-A-deficient mice had developed a more severe Pneumocystis infection than CD4-depleted WT (P. carinii pneumonia [PCP] scores of 3 versus 2, respectively). Whereas all non-CD4-depleted WT mice were free of PCP, intact SP-A?/? mice also had evidence of increased organism burden. Pneumocystis infection in SP-A-deficient mice was associated histologically with enhanced peribronchial and/or perivascular cellularity (score of 4 versus 2, SP-A?/? versus C57BL/6 mice, respectively) and a corresponding increase in bronchoalveolar lavage (BAL) cell counts. Increases in SP-D content, gamma interferon, interleukin-4, interleukin-5, and tumor necrosis factor alpha in BAL fluid occurred but were attenuated in PCP-infected SP-A?/? mice compared to WT mice. There were increases in total BAL NO levels in both infected groups, but nitrite levels were higher in SP-A?/? mice, indicating a reduction in production of higher oxides of nitrogen that was also reflected in lower levels of 3-nitrotyrosine staining in the SP-A?/? group. We conclude that despite increases in inflammatory cells, SP-A-deficient mice infected with P. carinii exhibit an enhanced susceptibility to the organism and attenuated production of proinflammatory cytokines and reactive oxygen-nitrogen species. These data support the concept that SP-A is a local effector molecule in the lung host defense against P. carinii in vivo. PMID:15385504
Paclitaxel therapy potentiates cold hyperalgesia in streptozotocin-induced diabetic rats through enhanced mitochondrial reactive oxygen species production and TRPA1 sensitization.
BarriŔre, David AndrÚ; Rieusset, Jennifer; Chanteranne, Didier; Busserolles, JÚr˘me; Chauvin, Marie-AgnŔs; Chapuis, LaŰtitia; Salles, JÚr˘me; Dubray, Claude; Morio, BÚatrice
Diabetes comorbidities include disabling peripheral neuropathy (DPN) and an increased risk of developing cancer. Antimitotic drugs, such as paclitaxel, are well known to facilitate the occurrence of peripheral neuropathy. Practitioners frequently observe the development or co-occurrence of enhanced DPN, especially cold sensitivity, in diabetic patients during chemotherapy. Preclinical studies showed that reactive oxygen species (ROS) and cold activate transient receptor potential ankyrin-1 (TRPA1) cation channels, which are involved in cold-evoked pain transduction signaling in DPN. Additionally, paclitaxel treatment has been associated with an accumulation of atypical mitochondria in the sensory nerves of rats. We hypothesized that paclitaxel might potentiate cold hyperalgesia by increasing mitochondrial injuries and TRPA1 activation. Thus, the kinetics of paclitaxel-induced cold hyperalgesia, mitochondrial ROS production, and TRPA1 expression were evaluated in dorsal root ganglia of normoglycemic and streptozotocin-induced diabetic rats. In diabetic rats, paclitaxel significantly enhanced cold hyperalgesia in comparison to normoglycemic paclitaxel-treated control rats. These effects were prevented by N-acetyl-cysteine, a reducing agent, and by HC030031, an antagonist of TRPA1. In diabetic and control rats, paclitaxel treatment was associated with an accumulation of atypical mitochondria and a 2-fold increase in mitochondrial ROS production. Moreover, mRNA levels of glutathione peroxidase 4 and glutathione-S-reductase were significantly lower in diabetic groups treated with paclitaxel. Finally, TRPA1 gene expression was enhanced by 45% in diabetic rats. Paclitaxel potentiation of cold hyperalgesia in diabetes may result from the combination of increased mitochondrial ROS production and poor radical detoxification induced by paclitaxel treatment and diabetes-related overexpression of TRPA1. PMID:22177224
The influence of N-doped carbon materials on supported Pd: enhanced hydrogen storage and oxygen reduction performance.
Kong, Xiang-Kai; Chen, Qian-Wang; Lun, Zheng-Yan
N-doped graphene has become an important support for Pd in both hydrogen storage and catalytic reactions. The molecular orbitals of carbon materials (including graphene, fullerene, and small carbon clusters) and those of the supported Pd species will hybrid much stronger as N dopants are introduced, owing to the increased electrostatic attraction at the interface. This enhances the carbon substrates' catching force for the supported Pd, preventing its leaching and aggregation in many practical applications. The better dispersion and stabilization of Pd nanoparticles, which are induced by various carbon supports with N-doping, are pleasing to us and could increase their efficiency and facilitate their recycling during various reaction processes in several fields. PMID:24435885
Laboratory procedure for determining the total heat of combustion in solid wastes. Open-file report
The heats evolved in the complete combustion of many compounds in oxygen have been carefully determined. The method ordinarily used is to burn the substance in a combustion bomb and to measure the heat evolved. The heat of combustion described in this method is expressed in calories per gram of sample or British Thermal Units (Btu) per pound of sample.
ORIGINAL PAPER Fireside Corrosion in Oxy-fuel Combustion of Coal
Laughlin, David E.
ORIGINAL PAPER Fireside Corrosion in Oxy-fuel Combustion of Coal Gordon R. Holcomb Ě Joseph Tylczak-fuel combustion is burning a fuel in oxygen rather than air for ease of capture of CO2 from for reuse between 10-4 and 10-3 atm of SO3 at 700 ░C. Keywords Fireside corrosion ┴ Oxidation ┴ Oxy-fuel combustion
Combustion Theory and Modelling Vol. 12, No. 2, April 2008, 349365
Heil, Matthias
Combustion Theory and Modelling Vol. 12, No. 2, April 2008, 349ş365 Premixed flames. Introduction An important realistic aspect in combustion is the reversibility of the chemical reactions, since. This is all the more true for the combustion of high caloric fuels, such as hydrogen with oxygen, where
Mobile Source Air Toxics (MSATs) from High Efficiency Clean Combustion: Catalytic Exhaust Treatment Effects
John Morse Storey; Samuel Arthur Lewis Sr; II Parks; James E; Teresa L Barone; Vitaly Y Prikhodko
High Efficiency Clean Combustion (HECC) strategies such as homogenous charge compression ignition (HCCI) and pre-mixed charge compression ignition (PCCI) offer much promise for the reduction of NOx and PM from diesel engines. While delivering low PM and low NOx, these combustion modes often produce much higher levels of CO and HC than conventional diesel combustion modes. In addition, partially oxygenated
Chemical Looping Combustion - Reduction of nickel oxide\\/nickel aluminate with hydrogen
Niklas Olsen
Chemical Looping Combustion (CLC) has been proposed as a power\\/heat generating process with inherent CO2 separation, as the fuel is not combusted in direct contact with nitrogen in the air. In CLC the combustion of fossil fuels is split into separate oxidation and reduction reactions. A reducible metal oxide is cycled between the reactors, and acts as an oxygen carrier.
Apparatus for photocatalytic destruction of internal combustion engine emissions during cold start
Janata, Jiri (Richland, WA); McVay, Gary L. (Richland, WA); Peden, Charles H. (West Richland, WA); Exarhos, Gregory J. (Richland, WA)
A method and apparatus for the destruction of emissions from an internal combustion engine wherein a substrate coated with TiO.sub.2 is exposed to a light source in the exhaust system of an internal combustion engine thereby catalyzing oxidation/reduction reactions between gaseous hydrocarbons, carbon monoxide, nitrogen oxides and oxygen in the exhaust of the internal combustion engine.
SOFT ROBOTICS. A 3D-printed, functionally graded soft robot powered by combustion.
Bartlett, Nicholas W; Tolley, Michael T; Overvelde, Johannes T B; Weaver, James C; Mosadegh, Bobak; Bertoldi, Katia; Whitesides, George M; Wood, Robert J
Roboticists have begun to design biologically inspired robots with soft or partially soft bodies, which have the potential to be more robust and adaptable, and safer for human interaction, than traditional rigid robots. However, key challenges in the design and manufacture of soft robots include the complex fabrication processes and the interfacing of soft and rigid components. We used multimaterial three-dimensional (3D) printing to manufacture a combustion-powered robot whose body transitions from a rigid core to a soft exterior. This stiffness gradient, spanning three orders of magnitude in modulus, enables reliable interfacing between rigid driving components (controller, battery, etc.) and the primarily soft body, and also enhances performance. Powered by the combustion of butane and oxygen, this robot is able to perform untethered jumping. PMID:26160940
Analysis of cyclic combustion of the coal-water suspension
NASA Astrophysics Data System (ADS)
Kijo-Kleczkowska, Agnieszka
Combustion technology of the coal-water suspension creates a number of new possibilities to organize the combustion process fulfilling contemporary requirements, e.g. in the environment protection. Therefore the in-depth analysis is necessary to examine the technical application of coal as a fuel in the form of suspension. The research undertakes the complex investigations of the continuous coal-water suspension as well as cyclic combustion. The cyclic nature of fuel combustion results from the movement of the loose material in the flow contour of the circulating fluidized bed (CFB): combustion chamber, cyclone and downcomer. The experimental results proved that the cyclic change of oxygen concentration around fuel, led to the vital change of both combustion mechanisms and combustion kinetics. The mathematical model of the process of fuel combustion has been presented. Its original concept is based on the allowance for cyclic changes of concentrations of oxygen around the fuel. It enables the prognosis for change of the surface and the centre temperatures as well as mass loss of the fuel during combustion in air, in the fluidized bed and during the cyclic combustion.
Combustion system for internal combustion engines
I. Matsuno; H. Yamazoe
A combustion system for internal combustion engines having an exhaust gas recirculating system which is operable by a lean airfuel mixture without aggravation of the combustion. The piston of the engine has a sub-piston projecting on the top thereof and the cylinder head is formed with a recess into which the sub-piston is insertable at a position near the top
Combustion device of an internal combustion engine
A combustion device of an internal combustion engine is described which consists of: a cylinder, a cylinder head closing one end of the cylinder; and a piston reciprocable in the cylinder; the head and piston having stepped portions adapted to interfit as the piston approaches the head so as to define a compression chamber, and a combustion chamber of greater
Reciprocating internal combustion engine with continuous combustion
The design of a reciprocating internal combustion engine having a continuous combustion is given. The combustion chamber must be connected with the cylinders of the engine by suitable transfer ports for supplying the gaseous medium to the cylinders and for discharging the burned mixture. In order to obtain a high efficiency, the transfer ports should be as short as possible.
Tipping point analysis of atmospheric oxygen concentration
NASA Astrophysics Data System (ADS)
Livina, Valerie N.; Vaz Martins, Teresa M.; Forbes, Alistair
We apply tipping point analysis to atmospheric oxygen concentration records. We warn that decrease of oxygen concentration from 21% to 19% would lead to significant health problems for humans and other animals, and estimate the time scale of such decline under various antropogenic scenarios. We suggest that society should be careful with introduction of new mass technologies that utilise double sink of atmospheric oxygen by both combustion and air-consuming synthesis in energy generation and product manufacturing.
Promoted Combustion Test Data Re-Examined
NASA Technical Reports Server (NTRS)
Lewis, Michelle; Jeffers, Nathan; Stoltzfus, Joel
Promoted combustion testing of metallic materials has been performed by NASA since the mid-1980s to determine the burn resistance of materials in oxygen-enriched environments. As the technolo gy has advanced, the method of interpreting, presenting, and applying the promoted combustion data has advanced as well. Recently NASA changed the bum criterion from 15 cm (6 in.) to 3 cm (1.2 in.). This new burn criterion was adopted for ASTM G 124, Standard Test Method for Determining the Combustion Behavior- of Metallic Materials in Oxygen-Enriched Atmospheres. Its effect on the test data and the latest method to display the test data will be discussed. Two specific examples that illustrate how this new criterion affects the burn/no-bum thresholds of metal alloys will also be presented.
Factors influencing spontaneous combustion of solid waste.
Moqbel, Shadi; Reinhart, Debra; Chen, Ruey-Hung
Landfill fires create a critical problem for landfill operators and require investigation of its occurrence and the conditions that favor its initiation. Subsurface fires are considered the most significant due to the difficulty in determining their location and extent. These fires are mainly caused by spontaneous combustion, combustion due to high temperature in absence of flame. This study investigates the effect of moisture content, oxygen concentration and leachate components on spontaneous ignition, combustion initiation, and self-heating of solid waste. A new procedure for testing spontaneous ignition is described; however, variations in solid waste components and landfill conditions can create some limitations to its use. The presence of water and dissolved solids in leachate was found to accelerate chemical self-heating of the solid waste. Oxygen concentration at 10% by volume can sustain chemical oxidation but did not promote accelerated burning. PMID:20110161
Particle behavior and char burnout mechanisms under pressurized combustion conditions
Bauer, C.M.; Spliethoff, H.; Hein, K.R.G.
Combined cycle systems with coal-fired gas turbines promise highest cycle efficiencies for this fuel. Pressurized pulverized coal combustion, in particular, yields high cycle efficiencies due to the high flue gas temperatures possible. The main problem, however, is to ensure a flue gas clean enough to meet the high gas turbine standards with a dirty fuel like coal. On the one hand, a profound knowledge of the basic chemical and physical processes during fuel conversion under elevated pressures is required whereas on the other hand suitable hot gas cleaning systems need to be developed. The objective of this work was to provide experimental data to enable a detailed description of pressurized coal combustion processes. A series of experiments were performed with two German hvb coals, Ensdorf and Goettelborn, and one German brown coal, Garzweiler, using a semi-technical scale pressurized entrained flow reactor. The parameters varied in the experiments were pressure, gas temperature and bulk gas oxygen concentration. A two-color pyrometer was used for in-situ determination of particle surface temperatures and particle sizes. Flue gas composition was measured and solid residue samples taken and subsequently analyzed. The char burnout reaction rates were determinated varying the parameters pressure, gas temperature and initial oxygen concentration. Variation of residence time was achieved by taking the samples at different points along the reaction zone. The most influential parameters on char burnout reaction rates were found to be oxygen partial pressure and fuel volatile content. With increasing pressure the burn-out reactions are accelerated and are mostly controlled by product desorption and pore diffusion being the limiting processes. The char burnout process is enhanced by a higher fuel volatile content.
Catalytic enhancement of the heme-based oxygen-sensing phosphodiesterase EcDOS by hydrogen sulfide is caused by changes in heme coordination structure.
Yan, Fang; Fojtikova, Veronika; Man, Petr; Stranava, Martin; MartÝnkovß, MarkÚta; Du, Yongming; Huang, Dongyang; Shimizu, Toru
EcDOS is a heme-based O2-sensing phosphodiesterase in which O2 binding to the heme iron complex in the N-terminal domain substantially enhances catalysis toward cyclic-di-GMP, which occurs in the C-terminal domain. Here, we found that hydrogen sulfide enhances the catalytic activity of full-length EcDOS, possibly owing to the admixture of 6-coordinated heme Fe(III)-SH(-) and Fe(II)-O2 complexes generated during the reaction. Alanine substitution at Met95, the axial ligand for the heme Fe(II) complex, converted the heme Fe(III) complex into the heme Fe(III)-SH(-) complex, but the addition of Na2S did not further reduce it to the heme Fe(II) complex of the Met95Ala mutant, and no subsequent formation of the heme Fe(II)-O2 complex was observed. In contrast, a Met95His mutant formed a stable heme Fe(II)-O2 complex in response to the same treatment. An Arg97Glu mutant, containing a glutamate substitution at the amino acid that interacts with O2 in the heme Fe(II)-O2 complex, formed a stable heme Fe(II) complex in response to Na2S, but this complex failed to bind O2. Interestingly, the addition of Na2S promoted formation of verdoheme (oxygen-incorporated, modified protoporphyrin IX) in an Arg97Ile mutant. Catalytic enhancement by Na2S was similar for Met95 mutants and the wild type, but significantly lower for the Arg97 mutants. Thus, this study shows the first isolation of spectrometrically separated, stable heme Fe(III)-SH(-), heme Fe(II) and heme Fe(II)-O2 complexes of full-length EcDOS with Na2S, and confirms that external-ligand-bound, 6-coordinated heme Fe(III)-SH(-) or heme Fe(II)-O2 complexes critically contribute to the Na2S-induced catalytic enhancement of EcDOS. PMID:25804428
Molecular structure of photosynthetic microbial biofuels for improved engine combustion and emissions characteristics.
Hellier, Paul; Purton, Saul; Ladommatos, Nicos
The metabolic engineering of photosynthetic microbes for production of novel hydrocarbons presents an opportunity for development of advanced designer biofuels. These can be significantly more sustainable, throughout the production-to-consumption lifecycle, than the fossil fuels and crop-based biofuels they might replace. Current biofuels, such as bioethanol and fatty acid methyl esters, have been developed primarily as drop-in replacements for existing fossil fuels, based on their physical properties and autoignition characteristics under specific combustion regimes. However, advances in the genetic engineering of microalgae and cyanobacteria, and the application of synthetic biology approaches offer the potential of designer strains capable of producing hydrocarbons and oxygenates with specific molecular structures. Furthermore, these fuel molecules can be designed for higher efficiency of energy release and lower exhaust emissions during combustion. This paper presents a review of potential fuel molecules from photosynthetic microbes and the performance of these possible fuels in modern internal combustion engines, highlighting which modifications to the molecular structure of such fuels may enhance their suitability for specific combustion regimes. PMID:25941673
This project was carried out to assess the impact of the use of oxygen and oxygen-enriched air for aeration of activated sludge systems on the safety of municipal waste-water treatment plants and their personnel. The tasks included (1) determination of oxygen combustion hazards f...
M Saenger; E.-U Hartge; J Werther; T Ogada; Z Siagi
Combustion mechanisms of two types of coffee husks have been studied using single particle combustion techniques as well as combustion in a pilot-scale fluidised bed facility (FBC), 150 mm in diameter and 9 m high. Through measurements of weight-loss and particle temperatures, the processes of drying, devolatilisation and combustion of coffee husks were studied. Axial temperature profiles in the FBC
An internal combustion engine method and apparatus are described wherein most or all of the air compression required for combustion is done outside of the internal combustion engine and out of heat exchange contact with the combustion chamber. The engine includes direct regeneration of exhaust heat and the compressor includes means for varying the compression ratio thereof in response to
Rotary internal combustion engine
Le, L.K.
This patent describes an internal combustion engine comprising; a rotary compressor mechanism; a rotary expander mechanism; and combustion chamber means disposed between the compressor mechanism and the expander mechanism, whereby compressed air is delivered to the combustion chamber through the compressor discharge port, and pressurized gas is delivered from the combustion chamber into the expander mechanism through the pressurized gas intake port.
Combustion fundamentals and applications
Not Available
These proceedings collect papers given at a meeting on combustion kinetics. Topics include: Effects of piston bowl geometry on combustion characteristics of diesel engines, bipropellant combustion, coal char reactivity, sulfur and nitrogen-oxide emissions, mineral matter in coal and wood, methane, liquid fuels, and carbon particle combustion.
Reactive oxygen species enhance excitatory synaptic transmission in rat spinal dorsal horn neurons by activating TRPA1 and TRPV1 channels.
Nishio, N; Taniguchi, W; Sugimura, Y K; Takiguchi, N; Yamanaka, M; Kiyoyuki, Yasukuni; Yamada, H; Miyazaki, N; Yoshida, M; Nakatsuka, T
Central neuropathic pain (CNP) in the spinal cord, such as chronic pain after spinal cord injury (SCI), is an incurable ailment. However, little is known about the spinal cord mechanisms underlying CNP. Recently, reactive oxygen species (ROS) have been recognized to play an important role in CNP of the spinal cord. However, it is unclear how ROS affect synaptic transmission in the dorsal horn of the spinal cord. To clarify how ROS impact on synaptic transmission, we investigated the effects of ROS on synaptic transmission in rat spinal cord substantia gelatinosa (SG) neurons using whole-cell patch-clamp recordings. Administration of tert-butyl hydroperoxide (t-BOOH), an ROS donor, into the spinal cord markedly increased the frequency and amplitude of spontaneous excitatory postsynaptic currents (sEPSCs) in SG neurons. This t-BOOH-induced enhancement was not suppressed by the Na(+) channel blocker tetrodotoxin. However, in the presence of a non-N-methyl-D-aspartate glutamate receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione, t-BOOH did not generate any sEPSCs. Furthermore, in the presence of a transient receptor potential ankyrin 1 (TRPA1) channel antagonist (HC-030031) or a transient receptor potential vanilloid 1 (TRPV1) channel antagonist (capsazepine or AMG9810), the t-BOOH-induced increase in the frequency of sEPSCs was inhibited. These results indicate that ROS enhance the spontaneous release of glutamate from presynaptic terminals onto SG neurons through TRPA1 and TRPV1 channel activation. Excessive activation of these ion channels by ROS may induce central sensitization in the spinal cord and result in chronic pain such as that following SCI. PMID:23707800
Overexpression of copper/zinc superoxide dismutase from mangrove Kandelia candel in tobacco enhances salinity tolerance by the reduction of reactive oxygen species in chloroplast
Jing, Xiaoshu; Hou, Peichen; Lu, Yanjun; Deng, Shurong; Li, Niya; Zhao, Rui; Sun, Jian; Wang, Yang; Han, Yansha; Lang, Tao; Ding, Mingquan; Shen, Xin; Chen, Shaoliang
Na+ uptake and transport in Kandelia candel and antioxidative defense were investigated under rising NaCl stress from 100 to 300 mM. Salinized K. candel roots had a net Na+ efflux with a declined flux rate during an extended NaCl exposure. Na+ buildup in leaves enhanced H2O2 levels, superoxide dismutase (SOD) activity, and increased transcription of CSD gene encoding a Cu/Zn SOD. Sequence and subcellular localization analyses have revealed that KcCSD is a typical Cu/Zn SOD in chloroplast. The transgenic tobacco experimental system was used as a functional genetics model to test the effect of KcCSD on salinity tolerance. KcCSD-transgenic lines were more Na+ tolerant than wild-type (WT) tobacco in terms of lipid peroxidation, root growth, and survival rate. In the latter, 100 mM NaCl led to a remarkable reduction in chlorophyll content and a/b ratio, decreased maximal chlorophyll a fluorescence, and photochemical efficiency of photosystem II. NaCl stress in WT resulted from H2O2 burst in chloroplast. Na+ injury to chloroplast was less pronounced in KcCSD-transgenic plants due to upregulated antioxidant defense. KcCSD-transgenic tobacco enhanced SOD activity by an increment in SOD isoenzymes under 100 mM NaCl stress from 24 h to 7 day. Catalase activity rose in KcCSD overexpressing tobacco plants. KcCSD-transgenic plants better scavenged NaCl-elicited reactive oxygen species (ROS) compared to WT ones. In conclusion, K. candel effectively excluded Na+ in roots during a short exposure; and increased CSD expression to reduce ROS in chloroplast in a long-term and high saline environment. PMID:25657655
Comparative sinterability of combustion synthesized and commercial titanium carbides
Manley, B.W.
The influence of various parameters on the sinterability of combustion synthesized titanium carbide was investigaged. Titanium carbide powders, prepared by the combustion synthesis process, were sintered in the temperature range 1150 to 1600/sup 0/C. Incomplete combustion and high oxygen contents were found to be the cause of reduced shrinkage during sintering of the combustion syntheized powders when compared to the shrinkage of commercial TiC. Free carbon was shown to inhibit shrinkage. The activation energy for sintering was found to depend on stoichiometry (C/Ti). With decreasing C/Ti, the rate of sintering increased. 29 references, 16 figures, 13 tables.
Preferential enhancement of reverse dermal Arthus reaction by polyelectrolytes: in vivo and in vitro evidence for mediation by oxygen-derived radicals and their metabolites
Ginsberg, I.; Warren, J.S.; Johnson, K.J.; Ward, P.A.
The ability of cationic and anionic polyelectrolytes (polyhistidine, histone, poly-arginine and polyanetholsulfonate) to modulate an acute immune complex (IgG-BSA) mediated inflammatory response was studied. Tissue injury elicited in rats by the reverse dermal Arthus reaction was increased 20-60% by complexing the antibody and polyelectrolye prior to intradermal injection. Intravenous administration of polyethylene glycol-coupled (PEG) superoxide dismutase (4125 U) produced a 30-70% suppression of this tissue injury. PEG-catalase (2000 U) had no suppressive effect. Concomitant in vitro functional studies (enzyme release, O/sub 2//sup -/ and H/sub 2/O/sub 2/ generation and chemiluminescence) of rat neutrophils stimulated with preformed immune complexes modified with polyelectrolytes demonstrated 2-fold increase in O/sub 2//sup -/ generation, modest increases in H/sub 2/O/sub 2/ generation and large increases in chemiluminescence. There was no change in enzyme (..beta..-glucuronidase) secretion. The polyelectrolytes employed in this study did not alter the capacity of preformed IgG-BSA complexes to fix complement. These studies suggest that immune complexes modified with either cationic or anionic polyelectrolytes have increased phlogistic potential that is at least in part mediated by enhanced generation of oxygen-derived metabolites and not by increased enzyme secretion or by increased fixation of complement.
Synthesis of octopus-tentacle-like Cu nanowire-Ag nanocrystals heterostructures and their enhanced electrocatalytic performance for oxygen reduction reaction.
Han, Min; Liu, Suli; Zhang, Linyan; Zhang, Can; Tu, Wenwen; Dai, Zhihui; Bao, Jianchun
In this article, the novel octopus-tentacle-like Cu nanowire-Ag nanocrystals heterostructures have been fabricated in solution phase via heterogeneous nucleation and growth of Ag nanocrystals on presynthesized Cu nanowires. The growth environment and dynamic factors of Ag nanocrystals play an important role for formation of such heterostructures. Combined the physical constants of Cu and Ag with a series of control experiments, the epitaxial growth means of Ag nanocrystals on Cu nanowire is found to abide by "layer-plus-island" (Stranski-Krastanow) mode. Because of the presence of multiple junctions and strong synergistic effect of their constituents, the obtained heterostructures exhibit greatly enhanced electrocatalytic performance toward oxygen reduction reaction compared with that of pure Ag nanocrystals, Cu nanowires, and mechanically mixed dual components as well as recently reported some non-Pt materials, which can be served as an alternative cathodic electrocatalyst to apply in alkaline fuel cells. Moreover, our method can be extended to fabricate octopus-tentacle-like Cu nanowire-Au nanocrystals and Cu nanowire-Pd nanocrystals heterostructures. PMID:23157177
Effect of oxygen plasma on field emission characteristics of single-wall carbon nanotubes grown by plasma enhanced chemical vapour deposition system
NASA Astrophysics Data System (ADS)
Kumar, Avshish; Parveen, Shama; Husain, Samina; Ali, Javid; Zulfequar, Mohammad; Harsh; Husain, Mushahid
Field emission properties of single wall carbon nanotubes (SWCNTs) grown on iron catalyst film by plasma enhanced chemical vapour deposition system were studied in diode configuration. The results were analysed in the framework of Fowler-Nordheim theory. The grown SWCNTs were found to be excellent field emitters, having emission current density higher than 20 mA/cm2 at a turn-on field of 1.3 V/?m. The as grown SWCNTs were further treated with Oxygen (O2) plasma for 5 min and again field emission characteristics were measured. The O2 plasma treated SWCNTs have shown dramatic improvement in their field emission properties with emission current density of 111 mA/cm2 at a much lower turn on field of 0.8 V/?m. The as grown as well as plasma treated SWCNTs were also characterized by various techniques, such as scanning electron microscopy, high resolution transmission electron microscopy, Raman spectroscopy, and Fourier transform infrared spectroscopy before and after O2 plasma treatment and the findings are being reported in this paper.
Photoinduced enhancement of the c-axis conductivity in oxygen-deficient YBa{sub 2}Cu{sub 3}O{sub x} thin films
Markowitsch, W.; Stockinger, C.; Lang, W. [Ludwig Boltzmann Institut fuer Festkoerperphysik, A-1060 Wien (Austria)] [Ludwig Boltzmann Institut fuer Festkoerperphysik, A-1060 Wien (Austria); [and Institut fuer Materialphysik der Universitaet Wien, A-1090 Wien (Austria); Bierleutgeb, K.; Pedarnig, J.D.; Baeuerle, D. [Angewandte Physik, Johannes-Kepler-Universitaet Linz, A-4040 Linz (Austria)] [Angewandte Physik, Johannes-Kepler-Universitaet Linz, A-4040 Linz (Austria)
High quality thin films of oxygen-depleted YBa{sub 2}Cu{sub 3}O{sub x} (x{approx}6.6) were prepared by pulsed-laser deposition on SrTiO{sub 3}, substrates that were cut with tilt angles of 10{degree} and 20{degree} with respect to the [001] direction, resulting in a steplike growth of the layers. The resistance showed a semiconducting behavior along the projection of the c axis to the film surface, but a metallic behavior in the perpendicular direction, indicating that the former is dominated by the c-axis resistivity and the latter by the ab-plane resistivity of YBa{sub 2}Cu{sub 3}O{sub x}. Long-term illumination of the samples with a 100 W halogen lamp resulted in a significant conductivity enhancement in both directions. The photoinduced change of the out-of-plane resistance vs temperature characteristics is comparable to the effect of large hydrostatic pressure, introducing structural changes similar to that of photoexcitation. {copyright} {ital 1997 American Institute of Physics.}
Hardesty, D.R. (ed.); Baxter, L.L.; Fletcher, T.H.; Mitchell, R.E.
The objective of this activity is to support the Office of Fossil Energy in executing research on coal combustion science. This activity consists of basic research on coal combustion that supports both the Pittsburgh Energy Technology Center (PETC) Direct Utilization Advanced Research and Technology Development Program, and the International Energy Agency (IEA) Coal Combustion Science Project. Specific tasks include: coal devolatilization, coal char combustion, and fate of mineral matter during coal combustion. 91 refs., 40 figs., 9 tabs.
Combustion Fundamentals Research
NASA Technical Reports Server (NTRS)
Increased emphasis is placed on fundamental and generic research at Lewis Research Center with less systems development efforts. This is especially true in combustion research, where the study of combustion fundamentals has grown significantly in order to better address the perceived long term technical needs of the aerospace industry. The main thrusts for this combustion fundamentals program area are as follows: analytical models of combustion processes, model verification experiments, fundamental combustion experiments, and advanced numeric techniques.
Coal combustion by wet oxidation
Bettinger, J.A.; Lamparter, R.A.; McDowell, D.C.
The combustion of coal by wet oxidation was studied by the Center for Waste Management Programs, of Michigan Technological University. In wet oxidation a combustible material, such as coal, is reacted with oxygen in the presence of liquid water. The reaction is typically carried out in the range of 204/sup 0/C (400/sup 0/F) to 353/sup 0/C (650/sup 0/F) with sufficient pressure to maintain the water present in the liquid state, and provide the partial pressure of oxygen in the gas phase necessary to carry out the reaction. Experimental studies to explore the key reaction parameters of temperature, time, oxidant, catalyst, coal type, and mesh size were conducted by running batch tests in a one-gallon stirred autoclave. The factors exhibiting the greatest effect on the extent of reaction were temperature and residence time. The effect of temperature was studied from 204/sup 0/C (400/sup 0/F) to 260/sup 0/C (500/sup 0/F) with a residence time from 600 to 3600 seconds. From this data, the reaction activation energy of 2.7 x 10/sup 4/ calories per mole was determined for a high-volatile-A-Bituminous type coal. The reaction rate constant may be determined at any temperature from the activation energy using the Arrhenius equation. Additional data were generated on the effect of mesh size and different coal types. A sample of peat was also tested. Two catalysts were evaluated, and their effects on reaction rate presented in the report. In addition to the high temperature combustion, low temperature desulfurization is discussed. Desulfurization can improve low grade coal to be used in conventional combustion methods. It was found that 90% of the sulfur can be removed from the coal by wet oxidation with the carbon untouched. Further desulfurization studies are indicated.
Effect of air distribution on solid fuel bed combustion
Kuo, J.T.; Hsu, W.S.; Yo, T.C. [National Taiwan Univ., Taipei (Taiwan, Province of China). Dept. of Mechanical Engineering
One important aspect of refuse mass-burn combination control is the manipulation of combustion air. Proper air manipulation is key to the achievement of good combustion efficiency and reduction of pollutant emissions. Experiments, using a small fix-grate laboratory furnace with cylindrical combustion chamber, were performed to investigate the influence of undergrate/sidewall air distribution on the combustion of beds of wood cubes. Wood cubes were used as a convenient laboratory surrogate of solid refuse. Specifically, for different bed configurations (e.g. bed height, bed voidage and bed fuel size, etc.), burning rates and combustion temperatures at different bed locations were measured under various air supply and distribution conditions. One of the significant results of the experimental investigation is that combustion, with air injected from side walls and no undergrate air, provide the most efficient combustion. On the other hand, combustion with undergrate air achieves higher combustion rates but with higher CO emissions. A simple one-dimensional model was constructed to derive correlations of combustion rate as functions of flue gas temperature and oxygen concentration. Despite the fact that the model is one dimensional and many detailed chemical and physical processes of combustion are not considered, comparisons of the model predictions and the experimental results indicate that the model is appropriate for quantitative evaluation of bed burning rates.
Gravity Effects on Combustion Synthesis of Glasses
NASA Technical Reports Server (NTRS)
Yi, H. C.; Guigne, J. Y.; Moore, J. J.; Robinson, L. A.; Manerbino, A. R.; Schowengerdt, F. D.; Gokoglu, S. (Technical Monitor)
The Combustion Synthesis technique has been used to produce glasses based on B2O3-Al2O3-MgO and CaO-Al2O3. The combustion characteristics of these combustion synthesis reactions using both small cylindrical pellets (SCP) and large spherical pellets (LSP) are presented. Low density pellets (approx. 35% of their theoretical density) were used, which made synthesis of low exothermic combustion reactions possible. Microstructural analysis of reacted samples was carried out to identify the glass-forming compositions. The effects of gravity on the glass formation were studied aboard the KC-135 using SCP samples. Gravity seemed to have such obvious effects on the combustion characteristics that the wave velocity was lower and the Width of the combustion wave was larger under reduced gravity conditions. Samples produced under low gravity also had more enhanced vitrification than those on ground, while some systems also exhibited lower combustion temperatures. It was also found that the container significantly affects both the combustion characteristics and microstructure. Substantially more divitrification occurred at the area which was in contact with the support (container).
Results of initial operation of the Jupiter Oxygen Corporation oxy-fuel 15 MWth burner test facility
Thomas Ochs; Danylo Oryshchyn; Rigel Woodside; Cathy Summers; Brian Patrick; Dietrich Gross; Mark Schoenfield; Thomas Weber; Dan OBrien
Jupiter Oxygen Corporation (JOC), in cooperation with the National Energy Technology Laboratory (NETL), constructed a 15 MWth oxy-fuel burner test facility with Integrated Pollutant Removal (IPRTM) to test high flame temperature oxy-fuel combustion and advanced carbon capture. Combustion protocols include baseline air firing with natural gas, oxygen and natural gas firing with and without flue gas recirculation, and oxygen and
The mechanism of CCN1-enhanced retinal neovascularization in oxygen-induced retinopathy through PI3K/AktľVEGF signaling pathway
Di, Yu; Zhang, Yiou; Yang, Hongwei; Wang, Aiyuan; Chen, Xiaolong
Background CCN1 (also called Cyr 61) is an extracellular matrix signaling molecule that has been implicated in neovascularization through its interactions with several endothelial integrin receptors. The roles of vascular endothelial growth factor (VEGF) in angiogenesis are well described. The aim of this study was to investigate the signal transduction mechanism of CCN1ľPI3K/AktľVEGF in retinopathy of prematurity (ROP), and the effects of CCN1 knockdown on ROP. Methods The oxygen-induced retinopathy (OIR) model was established in C57BL/6J mice exposed to a high concentration of oxygen. Retinas were obtained from the normoxia, OIR, OIR control (treated with scramble siRNA) and OIR treated (with CCN1 siRNA) groups. Retinal neovascularization (RNV) was qualitatively analyzed with ADPase staining and quantitatively analyzed by counting neovascular endothelial cell nuclei at postnatal day 17 when RNV reached a peak. mRNA level and protein expression of CCN1, p-Akt, and VEGF were measured by real-time PCR and Western blotting, and located with immunohistochemistry. Results CCN1 depletion resulted in less neovascularization clock hour scores in the number of preretinal neovascular cells compared with the OIR treated group (1.28▒0.83 versus 4.80▒0.82; and 7.12▒2.50 versus 23.25▒2.35, respectively, both P<0.05). Furthermore, CCN1, p-Akt and VEGF mRNA, and protein were significantly expressed in the retina of the OIR and OIR control groups. Intravitreal injection of CCN1 siRNA significantly reduced PI3K/AktľVEGF pathway expression of the OIR mouse model (all P<0.05). CCN1 siRNA significantly enhanced the avascular area and avascular diameter of OIR model (P<0.05). CCN1 siRNA decreased the levels of IL-1?, IL-6, and TNF-? significantly compared to the OIR group (P<0.05). Conclusion These results suggest that CCN1 plays an important role in RNV via the PI3K/AktľVEGF signaling pathway. CCN1 may be a potential target for the prevention and treatment of ROP. PMID:25995618
Benner, William H. (Danville, CA)
An oxygen analyzer which identifies and classifies microgram quantities of oxygen in ambient particulate matter and for quantitating organic oxygen in solvent extracts of ambient particulate matter. A sample is pyrolyzed in oxygen-free nitrogen gas (N.sub.2), and the resulting oxygen quantitatively converted to carbon monoxide (CO) by contact with hot granular carbon (C). Two analysis modes are made possible: (1) rapid determination of total pyrolyzable oxygen obtained by decomposing the sample at 1135.degree. C., or (2) temperature-programmed oxygen thermal analysis obtained by heating the sample from room temperature to 1135.degree. C. as a function of time. The analyzer basically comprises a pyrolysis tube containing a bed of granular carbon under N.sub.2, ovens used to heat the carbon and/or decompose the sample, and a non-dispersive infrared CO detector coupled to a mini-computer to quantitate oxygen in the decomposition products and control oven heating.
Chemical Kinetic Models for HCCI and Diesel Combustion
Pitz, W J; Westbook, C K; Mehl, M
Hydrocarbon fuels for advanced combustion engines consist of complex mixtures of hundreds or even thousands of different components. These components can be grouped into a number of chemically distinct classes, consisting of n-paraffins, branched paraffins, cyclic paraffins, olefins, oxygenates, and aromatics. Biodiesel contains its own unique chemical class called methyl esters. The fractional amounts of these chemical classes are quite different in gasoline, diesel fuel, oil-sand derived fuels and bio-derived fuels, which contributes to the very different combustion characteristics of each of these types of combustion systems. The objectives of this project are: (1) Develop detailed chemical kinetic models for fuel components used in surrogate fuels for diesel and HCCI engines; (2) Develop surrogate fuel models to represent real fuels and model low temperature combustion strategies in HCCI and diesel engines that lead to low emissions and high efficiency; and (3) Characterize the role of fuel composition on low temperature combustion modes of advanced combustion engines.
Detection of millimonolayers of oxygen on GaAs(001): observation of edge-effect rainbow enhancement in impact collision ion-scattering spectroscopy
Samir J. Anz; Kourosh Nafisi; Janice S. Allen; Anne Marie Russell; R. Stanley Williams
Time-of-flight impact collision ion-scattering spectroscopy (TOF-ICISS) data obtained with 12 keV Ar+ scattered from a GaAs(001) surface revealed the presence of millimonolayer amounts of oxygen. This magnitude of detection sensitivity is the result of an edge-effect rainbow singularity initiated by the forward scattering of argon by oxygen. Analysis of the TOF-ICISS data shows that the oxygen atoms are bonded primarily
Solution Combustion Synthesis Impregnated Layer Combustion Synthesis is a Novel
Mukasyan, Alexander
Solution Combustion Synthesis Impregnated Layer Combustion Synthesis is a Novel Methodology Engineering University of Notre Dame University of Notre Dame #12;Outline: Overview of combustion synthesis Reaction system Combustion front analaysis Theoretical model results Conclusions Acknowledgements #12
This report presents work carried out under contract DE-AC22-95PC95144 ''Combustion 2000 - Phase II.'' The goals of the program are to develop a coal-fired high performance power generation system (HIPPS) that is capable of: {lg_bullet} thermal efficiency (HHV) {ge} 47% {lg_bullet} NOx, SOx, and particulates {le} 10% NSPS (New Source Performance Standard) {lg_bullet} coal providing {ge} 65% of heat input {lg_bullet} all solid wastes benign {lg_bullet} cost of electricity {le} 90% of present plants Phase I, which began in 1992, focused on the analysis of various configurations of indirectly fired cycles and on technical assessments of alternative plant subsystems and components, including performance requirements, developmental status, design options, complexity and reliability, and capital and operating costs. Phase I also included preliminary R&D and the preparation of designs for HIPPS commercial plants approximately 300 MWe in size. Phase II, had as its initial objective the development of a complete design base for the construction and operation of a HIPPS prototype plant to be constructed in Phase III. As part of a descoping initiative, the Phase III program has been eliminated and work related to the commercial plant design has been ended. The rescoped program retained a program of engineering research and development focusing on high temperature heat exchangers, e.g. HITAF development (Task 2); a rescoped Task 6 that is pertinent to Vision 21 objectives and focuses on advanced cycle analysis and optimization, integration of gas turbines into complex cycles, and repowering designs; and preparation of the Phase II Technical Report (Task 8). This rescoped program deleted all subsystem testing (Tasks 3, 4, and 5) and the development of a site specific engineering design and test plan for the HIPPS prototype plant (Task 7). Work reported herein is from: {lg_bullet} Task 2.2.4 Pilot Scale Testing {lg_bullet} Task 22.214.171.124 Laboratory and Bench Scale Activities
A. Levasseur; S. Goodstine; J. Ruby; M. Nawaz; C. Senior; F. Robson; S. Lehman; W. Blecher; W. Fugard; A. Rao; A. Sarofim; P. Smith; D. Pershing; E. Eddings; M. Cremer; J. Hurley; G. Weber; M. Jones; M. Collings; D. Hajicek; A. Henderson; P. Klevan; D. Seery; B. Knight; R. Lessard; J. Sangiovanni; A. Dennis; C. Bird; W. Sutton; N. Bornstein; F. Cogswell; C. Randino; S. Gale; Mike Heap
This report is a presentation of work carried out on Phase II of the HIPPS program under DOE contract DE-AC22-95PC95144 from June 1995 to March 2001. The objective of this report is to emphasize the results and achievements of the program and not to archive every detail of the past six years of effort. These details are already available in the twenty-two quarterly reports previously submitted to DOE and in the final report from Phase I. The report is divided into three major foci, indicative of the three operational groupings of the program as it evolved, was restructured, or overtaken by events. In each of these areas, the results exceeded DOE goals and expectations. HIPPS Systems and Cycles (including thermodynamic cycles, power cycle alternatives, baseline plant costs and new opportunities) HITAF Components and Designs (including design of heat exchangers, materials, ash management and combustor design) Testing Program for Radiative and Convective Air Heaters (including the design and construction of the test furnace and the results of the tests) There are several topics that were part of the original program but whose importance was diminished when the contract was significantly modified. The elimination of the subsystem testing and the Phase III demonstration lessened the relevance of subtasks related to these efforts. For example, the cross flow mixing study, the CFD modeling of the convective air heater and the power island analysis are important to a commercial plant design but not to the R&D product contained in this report. These topics are of course, discussed in the quarterly reports under this contract. The DOE goal for the High Performance Power Plant System ( HIPPS ) is high thermodynamic efficiency and significantly reduced emissions. Specifically, the goal is a 300 MWe plant with > 47% (HHV) overall efficiency and {le} 0.1 NSPS emissions. This plant must fire at least 65% coal with the balance being made up by a premium fuel such as natural gas. To achieve these objectives requires a change from complete reliance of coal-fired systems on steam turbines (Rankine cycles) and moving forward to a combined cycle utilizing gas turbines (Brayton cycles) which offer the possibility of significantly greater efficiency. This is because gas turbine cycles operate at temperatures well beyond current steam cycles, allowing the working fluid (air) temperature to more closely approach that of the major energy source, the combustion of coal. In fact, a good figure of merit for a HIPPS design is just how much of the enthalpy from coal combustion is used by the gas turbine. The efficiency of a power cycle varies directly with the temperature of the working fluid and for contemporary gas turbines the optimal turbine inlet temperature is in the range of 2300-2500 F (1260-1371 C). These temperatures are beyond the working range of currently available alloys and are also in the range of the ash fusion temperature of most coals. These two sets of physical properties combine to produce the major engineering challenges for a HIPPS design. The UTRC team developed a design hierarchy to impose more rigor in our approach. Once the size of the plant had been determined by the choice of gas turbine and the matching steam turbine, the design process of the High Temperature Advanced Furnace (HITAF) moved ineluctably to a down-fired, slagging configuration. This design was based on two air heaters: one a high temperature slagging Radiative Air Heater (RAH) and a lower temperature, dry ash Convective Air Heater (CAH). The specific details of the air heaters are arrived at by an iterative sequence in the following order:-Starting from the overall Cycle requirements which set the limits for the combustion and heat transfer analysis-The available enthalpy determined the range of materials, ceramics or alloys, which could tolerate the temperatures-Structural Analysis of the designs proved to be the major limitation-Finally the commercialization issues of fabrication and reliability, availability and maintenance. The program that has s
Exposure to low oxygen tension and increased osmolarity enhance the ability of Mycobacterium avium to enter intestinal epithelial (HT-29) cells.
Bermudez, L E; Petrofsky, M; Goodman, J
Current evidence indicates that Mycobacterium avium infection in patients with AIDS is acquired mostly through the gastrointestinal (GI) tract and that M. avium binds to and invades GI mucosal cells in vitro. Since M. avium is exposed to specific environmental conditions in the GI tract such as changes in pH, low oxygen (O2) tension, increased osmolarity, and low concentration of iron, we investigated the effects of these conditions on the bacterium's ability to enter HT-29 intestinal cells. M. avium 101 (serovar 1) was cultured in 7H9 broth and then exposed to pH 4.5 to 8.0, low O2 tension, 0.1 to 0.3 M dextrose, and absence of iron for 2 h. After washing, bacteria (10(7)/ml) were used in the invasion assay. Confluent HT-29 cells were exposed to 10(6) bacteria for 1 h and then treated with amikacin (200 microg/ml) for 2 h to selectively kill extracellular but not intracellular M. avium. The supernatant was then removed, the monolayer was lysed, and the lysate was plated onto 7H10 agar plates. While exposure to acidic and basic pHs, as well as iron-free medium, had no significant effect on M. avium invasion of intestinal epithelial cells, low O2 tension and increased osmolarity enhanced invasion 11- and 9-fold, respectively, compared with the control. Exposure of M. avium to the combination of low O2 concentration and hyperosmolarity resulted in an approximate 10- to 15-fold increase in penetration of HT-29 cells. Hyperosmolarity and low O2 tension induced the invasive M. avium phenotype and can be useful for the identification of genes associated with M. avium invasion of intestinal mucosa. PMID:9284150
Metabolic agents that enhance ATP can improve cognitive functioning: a review of the evidence for glucose, oxygen, pyruvate, creatine, and L-carnitine.
Owen, Lauren; Sunram-Lea, Sandra I
Over the past four or five decades, there has been increasing interest in the neurochemical regulation of cognition. This field received considerable attention in the 1980s, with the identification of possible cognition enhancing agents or "smart drugs". Even though many of the optimistic claims for some agents have proven premature, evidence suggests that several metabolic agents may prove to be effective in improving and preserving cognitive performance and may lead to better cognitive aging through the lifespan. Aging is characterized by a progressive deterioration in physiological functions and metabolic processes. There are a number of agents with the potential to improve metabolic activity. Research is now beginning to identify these various agents and delineate their potential usefulness for improving cognition in health and disease. This review provides a brief overview of the metabolic agents glucose, oxygen, pyruvate, creatine, and L-carnitine and their beneficial effects on cognitive function. These agents are directly responsible for generating ATP (adenosine triphosphate) the main cellular currency of energy. The brain is the most metabolically active organ in the body and as such is particularly vulnerable to disruption of energy resources. Therefore interventions that sustain adenosine triphosphate (ATP) levels may have importance for improving neuronal dysfunction and loss. Moreover, recently, it has been observed that environmental conditions and diet can affect transgenerational gene expression via epigenetic mechanisms. Metabolic agents might play a role in regulation of nutritional epigenetic effects. In summary, the reviewed metabolic agents represent a promising strategy for improving cognitive function and possibly slowing or preventing cognitive decline. PMID:22254121
Noninvasive Monitoring of Microvascular Changes With Partial Irradiation Using Dynamic Contrast-Enhanced and Blood Oxygen Level-Dependent Magnetic Resonance Imaging
Lin, Yu-Chun [Department of Medical Imaging and Intervention, Chang Gung Memorial Hospital, Linkou, Taiwan (China) [Department of Medical Imaging and Intervention, Chang Gung Memorial Hospital, Linkou, Taiwan (China); Department of Electrical Engineering, Chang Gung University, Linkou, Taiwan (China); Department of Medical Imaging and Radiological Sciences, Chang Gung University, Linkou, Taiwan (China); Wang, Jiun-Jie [Department of Medical Imaging and Intervention, Chang Gung Memorial Hospital, Linkou, Taiwan (China) [Department of Medical Imaging and Intervention, Chang Gung Memorial Hospital, Linkou, Taiwan (China); Department of Medical Imaging and Radiological Sciences, Chang Gung University, Linkou, Taiwan (China); Hong, Ji-Hong [Department of Medical Imaging and Radiological Sciences, Chang Gung University, Linkou, Taiwan (China) [Department of Medical Imaging and Radiological Sciences, Chang Gung University, Linkou, Taiwan (China); Department of Radiation Oncology, Chang Gung Memorial Hospital, Linkou, Taiwan (China); Lin, Yi-Ping [Department of Radiation Oncology, Chang Gung Memorial Hospital, Linkou, Taiwan (China)] [Department of Radiation Oncology, Chang Gung Memorial Hospital, Linkou, Taiwan (China); Lee, Chung-Chi [Department of Medical Imaging and Radiological Sciences, Chang Gung University, Linkou, Taiwan (China) [Department of Medical Imaging and Radiological Sciences, Chang Gung University, Linkou, Taiwan (China); Department of Radiation Oncology, Chang Gung Memorial Hospital, Linkou, Taiwan (China); Wai, Yau-Yau; Ng, Shu-Hang; Wu, Yi-Ming [Department of Medical Imaging and Intervention, Chang Gung Memorial Hospital, Linkou, Taiwan (China) [Department of Medical Imaging and Intervention, Chang Gung Memorial Hospital, Linkou, Taiwan (China); Department of Medical Imaging and Radiological Sciences, Chang Gung University, Linkou, Taiwan (China); Wang, Chun-Chieh, E-mail: firstname.lastname@example.com [Department of Medical Imaging and Radiological Sciences, Chang Gung University, Linkou, Taiwan (China) [Department of Medical Imaging and Radiological Sciences, Chang Gung University, Linkou, Taiwan (China); Department of Radiation Oncology, Chang Gung Memorial Hospital, Linkou, Taiwan (China)
Purpose: The microvasculature of a tumor plays an important role in its response to radiation therapy. Dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) and blood oxygen level-dependent (BOLD) MRI are both sensitive to vascular characteristics. The present study proposed a partial irradiation approach to a xenograft tumor to investigate the intratumoral response to radiation therapy using DCE and BOLD MRI. Methods and Materials: TRAMP-C1 tumors were grown in C57BL/6J mice. Partial irradiation was performed on the distal half of the tumor with a single dose of 15 Gy. DCE MRI was performed to derive the endothelium transfer constant, K{sup trans}, using pharmacokinetic analysis. BOLD MRI was performed using quantitative R2* measurements with carbogen breathing. The histology of the tumor was analyzed using hematoxylin and eosin staining and CD31 staining to detect endothelial cells. The differences between the irradiated and nonirradiated regions of the tumor were assessed using K{sup trans} values, ?R2* values in response to carbogen and microvascular density (MVD) measurements. Results: A significantly increased K{sup trans} and reduced BOLD response to carbogen were found in the irradiated region of the tumor compared with the nonirradiated region (P<.05). Histologic analysis showed a significant aggregation of giant cells and a reduced MVD in the irradiated region of the tumor. The radiation-induced difference in the BOLD response was associated with differences in MVD and K{sup trans}. Conclusions: We demonstrated that DCE MRI and carbogen-challenge BOLD MRI can detect differential responses within a tumor that may potentially serve as noninvasive imaging biomarkers to detect microvascular changes in response to radiation therapy.
The environmental carcinogen 3-nitrobenzanthrone and its main metabolite 3-aminobenzanthrone enhance formation of reactive oxygen intermediates in human A549 lung epithelial cells
Hansen, Tanja [Fraunhofer Institute of Toxicology and Experimental Medicine, Nikolai-Fuchs-Str. 1, 30625 Hannover (Germany)]. E-mail: firstname.lastname@example.com; Seidel, Albrecht [Biochemical Institute for Environmental Carcinogens, Prof. Dr. Gernot Grimmer Foundation, Lurup 4, 22927 Grosshansdorf (Germany); Borlak, Juergen [Fraunhofer Institute of Toxicology and Experimental Medicine, Nikolai-Fuchs-Str. 1, 30625 Hannover (Germany)
The environmental contaminant 3-nitrobenzanthrone (3-NBA) is highly mutagenic and a suspected human carcinogen. We aimed to evaluate whether 3-NBA is able to deregulate critical steps in cell cycle control and apoptosis in human lung epithelial A549 cells. Increased intracellular Ca{sup 2+} and caspase activities were detected upon 3-NBA exposure. As shown by cell cycle analysis, an increased number of S-phase cells was observed after 24 h of treatment with 3-NBA. Furthermore, 3-NBA was shown to inhibit cell proliferation when added to subconfluent cell cultures. The main metabolite of 3-NBA, 3-ABA, induced statistically significant increases in tail moment as judged by alkaline comet assay. The potential of 3-NBA and 3-ABA to enhance the production of reactive oxygen species (ROS) was demonstrated by flow cytometry using 2',7'-dichlorofluorescein-diacetate (DCFH-DA). The enzyme inhibitors allopurinol, dicumarol, resveratrol and SKF525A were used to assess the impact of metabolic conversion on 3-NBA-mediated ROS production. Resveratrol decreased dichlorofluorescein (DCF) fluorescence by 50%, suggesting a role for CYP1A1 in 3-NBA-mediated ROS production. Mitochondrial ROS production was significantly attenuated (20% reduction) by addition of rotenone (complex I inhibition) and thenoyltrifluoroacetone (TTFA, complex II inhibition). Taken together, the results of the present study provide evidence for a genotoxic potential of 3-ABA in human epithelial lung cells. Moreover, both compounds lead to increased intracellular ROS and create an environment favorable to DNA damage and the promotion of cancer.
Measuring a 10,000-fold enhancement of singlet molecular oxygen (1O2*) concentration on illuminated ice relative to the corresponding liquid solution
NASA Astrophysics Data System (ADS)
Bower, Jonathan P.; Anastasio, Cort
Much attention has focused on the highly reactive hydroxyl radical in the oxidation of trace organic compounds on snow and ice (and subsequent release of volatile organics to the atmospheric boundary layer) but other oxidants are likely also important in this processing. Here we examine the ice chemistry of singlet molecular oxygen (1O2*), which can be significant in atmospheric water drops but has not been examined in ice or snow. To examine 1O2* on ice we illuminate laboratory ices containing Rose Bengal (RB) as the source of 1O2*, furfuryl alcohol (FFA) as the probe, and Na2SO4 to control the total solute concentration. We find that the 1O2*-mediated loss of FFA (and, thus, the 1O2* concentration) is up to 11,000 times greater on ice than in the equivalent liquid sample at the same photon flux. We attribute this large increase in the 1O2* steady-state concentration to the freeze-concentration of solutes into liquid-like regions (LLRs) in/on ice: compared to the initial solution, in the LLRs of ice the sources for 1O2* are highly concentrated, while the concentration of the dominant sink for 1O2* (i.e., water) remains largely unchanged. Similar to results expected in liquid solution, rates of FFA loss in ice depend on both the initial sensitizer concentration and temperature, providing evidence that these reactions occur in LLRs. However, we find that the enhancement in 1O2* concentrations on ice does not follow predictions from freezing-point depression, likely because experiments were conducted below the eutectic temperature for sodium sulfate, where all of the salt should have precipitated. We also explore a method for separating 1O2* and rad OH contributions to FFA oxidation in laboratory ices and show its application to two natural snow samples. We find that 1O2* concentrations in these snows are approximately 100 times higher than observed in polluted, mid-latitude fog waters, showing that the enhancement of 1O2* on ice is environmentally relevant and that 1O2* could be a significant sink for electron-rich organic compounds in snow.
Combustion chamber for an internal-combustion engine
A combustion chamber for an internal-combustion engine is described comprising: a main combustion chamber defined by a first recess in the top surface of the crown of a piston; an auxiliary combustion chamber defined by a second recess in the top surface of the crown of the piston beside the main combustion chamber, the volume of the auxiliary combustion chamber
Chemical Looping Combustion Reactions and Systems
Sarofim, Adel; Lighty, JoAnn; Smith, Philip; Whitty, Kevin; Eyring, Edward; Sahir, Asad; Alvarez, Milo; Hradisky, Michael; Clayton, Chris; Konya, Gabor; Baracki, Richard; Kelly, Kerry
Chemical Looping Combustion (CLC) is one promising fuel-combustion technology, which can facilitate economic CO2 capture in coal-fired power plants. It employs the oxidation/reduction characteristics of a metal, or oxygen carrier, and its oxide, the oxidizing gas (typically air) and the fuel source may be kept separate. This work focused on two classes of oxygen carrier, one that merely undergoes a change in oxidation state, such as Fe3O4/Fe2O3 and one that is converted from its higher to its lower oxidation state by the release of oxygen on heating, i.e., CuO/Cu2O. This topical report discusses the results of four complementary efforts: (1) the development of process and economic models to optimize important design considerations, such as oxygen carrier circulation rate, temperature, residence time; (2) the development of high-performance simulation capabilities for fluidized beds and the collection, parameter identification, and preliminary verification/uncertainty quantification (3) the exploration of operating characteristics in the laboratory-scale bubbling bed reactor, with a focus on the oxygen carrier performance, including reactivity, oxygen carrying capacity, attrition resistance, resistance to deactivation, cost and availability (4) the identification of mechanisms and rates for the copper, cuprous oxide, and cupric oxide system using thermogravimetric analysis.
Benner, W.H.
An oxygen analyzer which identifies and classifies microgram quantities of oxygen in ambient particulate matter and for quantitating organic oxygen in solvent extracts of ambient particulate matter. A sample is pyrolyzed in oxygen-free nitrogen gas (N/sub 2/), and the resulting oxygen quantitatively converted to carbon monoxide (CO) by contact with hot granular carbon (C). Two analysis modes are made possible: (1) rapid determination of total pyrolyzable obtained by decomposing the sample at 1135/sup 0/C, or (2) temperature-programmed oxygen thermal analysis obtained by heating the sample from room temperature to 1135/sup 0/C as a function of time. The analyzer basically comprises a pyrolysis tube containing a bed of granular carbon under N/sub 2/, ovens used to heat the carbon and/or decompose the sample, and a non-dispersive infrared CO detector coupled to a mini-computer to quantitate oxygen in the decomposition products and control oven heating.
On-Line Measurement of Heat of Combustion of Gaseous Hydrocarbon Fuel Mixtures
NASA Technical Reports Server (NTRS)
Sprinkle, Danny R.; Chaturvedi, Sushil K.; Kheireddine, Ali
A method for the on-line measurement of the heat of combustion of gaseous hydrocarbon fuel mixtures has been developed and tested. The method involves combustion of a test gas with a measured quantity of air to achieve a preset concentration of oxygen in the combustion products. This method involves using a controller which maintains the fuel (gas) volumetric flow rate at a level consistent with the desired oxygen concentration in the combustion products. The heat of combustion is determined form a known correlation with the fuel flow rate. An on-line computer accesses the fuel flow data and displays the heat of combustion measurement at desired time intervals. This technique appears to be especially applicable for measuring heats of combustion of hydrocarbon mixtures of unknown composition such as natural gas.
This report presents work carried out under contract DE-AC22-95PC95144 ''Combustion 2000 - Phase II.'' The goals of the program are to develop a coal-fired high performance power generation system (HIPPS) that is capable of: {lg_bullet} thermal efficiency (HHV) {ge} 47% {lg_bullet} NOx, SOx, and particulates {le} 10% NSPS (New Source Performance Standard) {lg_bullet} coal providing {ge} 65% of heat input {lg_bullet} all solid wastes benign {lg_bullet} cost of electricity {le} 90% of present plants Phase I, which began in 1992, focused on the analysis of various configurations of indirectly fired cycles and on technical assessments of alternative plant subsystems and components, including performance requirements, developmental status, design options, complexity and reliability, and capital and operating costs. Phase I also included preliminary R&D and the preparation of designs for HIPPS commercial plants approximately 300 MWe in size. Phase II, had as its initial objective the development of a complete design base for the construction and operation of a HIPPS prototype plant to be constructed in Phase III. As part of a descoping initiative, the Phase III program has been eliminated and work related to the commercial plant design has been ended. The rescoped program retained a program of engineering research and development focusing on high temperature heat exchangers, e.g. HITAF development (Task 2); a rescoped Task 6 that is pertinent to Vision 21 objectives and focuses on advanced cycle analysis and optimization, integration of gas turbines into complex cycles, and repowering designs; and preparation of the Phase II Technical Report (Task 8). This rescoped program deleted all subsystem testing (Tasks 3, 4, and 5) and the development of a site-specific engineering design and test plan for the HIPPS prototype plant (Task 7). Work reported herein is from: {lg_bullet} Task 2.2.4 Pilot Scale Testing {lg_bullet} Task 18.104.22.168 Laboratory and Bench Scale Activities
Effect of Oxyfuel Combustion on Superheater Corrosion
Covino, B.S., Jr.; Matthes, S.A.; Bullard, S.J.
Combustion of coal in an oxygen environment (as opposed to air) will facilitate the sequestering of carbon dioxide by minimizing the amount of nitrogen in the exit gas stream. The presence of higher levels of certain gases associated with oxyfuel combustion (eg, CO2, SO2, and H2O) may impact the corrosion of waterwalls, superheaters, headers, reheaters, and other boiler components. Research is being conducted on bare and ash-embedded boiler tube materials in simulated oxyfuel- combustion and air-combustion environments at a superheater temperature of 675░C. Alloys were exposed at temperature to two different gaseous environments. Preliminary results show: (1) an increase in corrosion rate of bare K02707, K11547, K21590, K91560, K92460, S30409, S34700, and N06617 exposed to the oxyfuel combustion environment when compared to the air combustion environment; (2) an increase in corrosion rate of alloys K21590, K92460, S34700, and N06617, when embedded in ash in comparison to bare exposure; and (3) no effect of gaseous environment on alloy corrosion rate when embedded in ash.
Biodegradation of gasoline ether oxygenates.
Hyman, Michael
Ether oxygenates such as methyl tertiary butyl ether (MTBE) are added to gasoline to improve fuel combustion and decrease exhaust emissions. Ether oxygenates and their tertiary alcohol metabolites are now an important group of groundwater pollutants. This review highlights recent advances in our understanding of the microorganisms, enzymes and pathways involved in both the aerobic and anaerobic biodegradation of these compounds. This review also aims to illustrate how these microbiological and biochemical studies have guided, and have helped refine, molecular and stable isotope-based analytical approaches that are increasingly being used to detect and quantify biodegradation of these compounds in contaminated environments. PMID:23116604
Pilot Plant Makes Oxygen Difluoride
NASA Technical Reports Server (NTRS)
Humphrey, Marshall F.; Lawton, Emil A.
Pilot plant makes oxygen difluoride highly-energetic, space-storable oxidizer not made commercially. Designed to handle reactants, product, and byproduct, most of which highly reactive, corrosive, and toxic. Oxygen difluoride evolves continuously from reactor containing potassium hydroxide in water at 10 degree C. Collection tanks alternated; one filled while other drained to storage cylinder. Excess OF2 and F2 dissipated in combustion of charcoal in burn barrel. Toxic byproduct, potassium fluoride, reacted with calcium hydroxide to form nontoxic calcium fluoride and to regenerate potassium hydroxide. Equipment processes toxic, difficult-to-make substance efficiently and safely.
NSDL National Science Digital Library
ChemTeacher compiles background information, videos, articles, demonstrations, worksheets and activities for high school teachers to use in their classrooms. The Combustion page includes resources for teaching students about the chemistry behind combustion.
Fletcher, R. J.
Energy is consumed, and wasted, in liberal amounts in the combustion processes which supply heat energy to boilers and process heaters. Close attention to combustion systems can be extremely beneficial: Optimum air to fuel ratios, i.e., maintaining...
HEATS OF COMBUSTION OF HIGH TEMPERATURE POLYMERS Richard N. Walters*, Stacey M. Hackett* and Richard E. Lyon
Laughlin, Robert B.
1 HEATS OF COMBUSTION OF HIGH TEMPERATURE POLYMERS Richard N. Walters*, Stacey M. Hackett Creek Avenue, Building C Egg Harbor Township, New Jersey 08234 ABSTRACT The heats of combustion to thermochemical calculations of the net heat of combustion from oxygen consumption and the gross heat
Proceedings of the Combustion Institute, Volume 29, 2002/pp. 26352643 DEMONSTRATION OF TEMPERATURE AND OH MOLE FRACTION
Wooldridge, Margaret S.
fractions in combustion synthesis flames. Introduction Gas-phase combustion synthesis (GPCS) of nano/hydrogen/oxygen/argon flames, verifying the applicability of the diagnostic approach to combustion synthesis systems- structured materials is a powerful synthesis method, capable of generating high-purity materials [1
NSDL National Science Digital Library
CREAM GK-12 Program, Engineering Education Research Center, College of Engineering and Architecture,
This lab exercise exposes students to a potentially new alternative energy sourceŚhydrogen gas. Student teams are given a hydrogen generator and an oxygen generator. They balance the chemical equation for the combustion of hydrogen gas in the presence of oxygen. Then they analyze what the equation really means. Two hypotheses are given, based on what one might predict upon analyzing the chemical equation. Once students have thought about the process, they are walked through the experiment and shown how to collect the gas in different ratios. By trial and error, students determine the ideal combustion ratio. For both volume of explosion and kick generated by explosion, they qualitatively record results on a 0-4 scale. Then, students evaluate their collected results to see if the hypotheses were correct and how their results match the theoretical equation. Students learn that while hydrogen will most commonly be used for fuel cells (no combustion situation), it has been used in rocket engines (for which a tremendous combustion occurs).
Internal combustion engine with dual combustion chambers
This patent describes a spark-ignition. The overhead valve type internal combustion engine comprises: a cylinder closed at the top by a semi-spherical cylinder head; a piston reciprocating within the cylinder with the piston; cylinder and cylinder head defining at least one combustion chamber; and wherein the cylinder head includes an intake valve aperture, an exhaust valve aperture, and a spark
Combustion Modeling in Internal Combustion Engines
The fundamental assumptions of the Blizard and Keck combustion model for internal combustion engines are examined and a generalization of that model is derived. The most significant feature of the model is that it permits the occurrence of unburned hydrocarbons in the thermodynamic-kinetic modeling of exhaust gases. The general formulas are evaluated in two specific cases that are likely to
Evaluation of novel ceria-supported materials as oxygen carriers for chemical-
Azad, Abdul-Majeed
Master's Thesis in the Master Degree Program, Innovative and Sustainable Energy Engineering ALI HEDAYATI-supported materials as oxygen carriers for chemical-looping combustion ALI HEDAYATI Department of Energy;Evaluation of novel ceria-supported materials as oxygen carriers for chemical-looping combustion Ali Hedayati
G. Perrin; H. Bergmann
An externally auto-ignited four-stroke internal combustion engine which includes a combustion chamber disposed in an upper surface of a piston such that, in an upper dead-center position of the piston, the combustion chamber receives almost all of the fuel-air mixture. The combustion chamber includes a planar bottom portion and has a cross-sectional shape of a truncated cone expanding in a
Sol-gel auto-combustion synthesis, structural and enhanced magnetic properties of Ni2+ substituted nanocrystalline Mg-Zn spinel ferrite
NASA Astrophysics Data System (ADS)
Bobade, D. H.; Rathod, S. M.; Mane, Maheshkumar L.
Nanocrystalline arrays of Ni2+ substituted Mg-Zn spinel ferrite having a generic formula Mg0.7-xNixZn0.3Fe2O4 (x=0.0, 0.2, 0.4 and 0.6) were successfully synthesized by sol-gel auto-combustion technique. The fuel used in the synthesis process was citric acid and the metal nitrate-to-citric acid ratio was taken as 1:3. The phase, crystal structure and morphology of Mg-Ni-Zn ferrites were investigated by X-ray diffraction, scanning electron microscopy, and Fourier transformer infrared spectroscopy techniques. The lattice constant, crystallite size, porosity and cation distribution were determined from the X-ray diffraction data method. The FTIR spectroscopy is used to deduce the structural investigation and redistribution of cations between octahedral and tetrahedral sites of Mg-Ni-Zn spinel structured material. Morphological investigation suggests the formation of grain growth as the Ni2+ content x increases. The saturation magnetization and magneton number were determined from hysteresis loop technique. The saturation magnetization increases with increasing Ni2+ concentration Ĺxĺ in Mg-Zn ferrite.
Internal combustion engine apparatus
Kondo, T.; Inaga, H.
An internal combustion engine apparatus is described comprising, in combination, an internal combustion engine having an ignition system capable of step advance when a predetermined engine speed is reached between low and high ranges of engine speed; and a centrifugal clutch connected to an output shaft of the internal combustion engine, the centrifugal clutch being engaged and disengaged at substantially the predetermined engine speed.
BOOK REVIEW: Turbulent Combustion
Norbert Peters
The book Turbulent Combustion by Norbert Peters is a concise monograph on single-phase gaseous low Mach number turbulent combustion. It is compiled from the author's review papers on this topic plus some additional material. Norbert Peters characterizes turbulent combustion both by the way fuel and air are mixed and by the ratio of turbulent and chemical time scales. This approach
A spark ignition internal combustion engine is described that uses a double-headed cylinder to achieve more complete combustion, and hence less unburned exhaust emissions, than existing internal combustion engine designs. The engine is of the piston type, with the piston mechanically arranged for both oscillatory and related vertically reciprocating motion. The cylinder is double-headed, and the heads are oriented with
An internal combustion engine is described which utilizes a combustion cylinder formed in part of material which can withstand high temperatures in conjunction with a displacement or power piston having a ringless section capable of withstanding high temperatures and being backed up by a relatively low temperature lubricated ringed piston section. Means to inject fuel and water into the combustion
Combustion synthesis and nanomaterials
Singanahally T. Aruna; Alexander S. Mukasyan
The recent developments and trends in combustion science towards the synthesis of nanomaterials are discussed. Different modifications made to conventional combustion approaches for preparation of nanomaterials are critically analyzed. Special attention is paid to various applications of combustion synthesized nanosized products.
The rate-limiting step for olefin combustion on silver: Experiment compared to theory
Roberts, J.T. (Univ. of Minnesota, Minneapolis (United States)); Madix, R.J.; Crew, W.W. (Stanford Univ., CA (United States))
The oxidation of propylene by atomically adsorbed oxygen on Ag(110) has been studied over a wide range of oxygen adatom coverages between 0.05 and 0.5 monolayers. Over the entire range of coverage combustion occurs easily, the only products observed are CO[sub 2] and H[sub 2]O, and all absorbed oxygen is found to react readily. The absence of acrolein as a product mitigates against the formation of allyl oxide as a combustion intermediate under these conditions. These results are in contrast to theoretical predictions concerning the mechanism of olefin combustion which invoke both homolytic C-H cleavage and oxygen insertion into a C-H bond to produce allyl oxide as an intermediate. Combustion of propylene and higher molecular weight 1-alkenes is proposed to occur predominantly via an acid-base reaction with chemisorbed oxygen. 39 refs., 3 figs., 1 tab.
DOE Project 18546, AOP Task 1.1, Fuel Effects on Advanced Combustion Engines
Bruce G Bunting; Michael Bunce
Research in 2011 was focused on diesel range fuels and diesel combustion and fuels evaluated in 2011 included a series of oxygenated biofuels fuels from University of Maine, oxygenated fuel compounds representing materials which could be made from sewage, oxygenated marine diesel fuels for low emissions, and a new series of FACE fuel surrogates and FACE fuels with detailed exhaust
Combustion synthesis of complex oxides
NASA Astrophysics Data System (ADS)
Ming, Qimin
Advanced ceramic materials have numerous applications in electronic engineering, chemical engineering, and semiconductor industry. The synthesis of these materials at an economical cost is the bottleneck in the application of these materials. Self-propagating High-temperature Synthesis (SHS) is a new technique for producing these materials for exothermic systems by a combustion wave that propagates and produces high purity products. The full potential of SHS to produce advanced materials has not yet been utilized. In this study, we used SHS to prepare two types of complex oxides: La 1-xSrxCrO3, La0.89Sr0.1 MnO3, powders, used to make interconnect and cathode of solid oxide fuel cells; and chromium- and gallium-doped La1-xSr xFeO3-delta, mixed ionic and electronic conductive powders used to manufacture ceramic membranes for oxygen separation. A thermodynamic feasibility analysis shows that the oxidation of Cr is the main source of heat generation of La1-xSrxCrO 3, which maintains a stable reaction front. Replacing part of the metallic Cr in the reaction mixture by its oxides decreases the combustion temperature and front propagating velocity and modifies the product morphology. The oxygen needed for the Cr oxidation is provided by the decomposition of CrO3 , SrO2, or NaClO4. The predicted and observed combustion temperatures are in reasonable agreement. TG/DTA analyses of La1-xSrxCrO3 indicated that SHS stability was strongly affected by the transport of oxygen between the two regions, in which oxygen was generated by the decomposition of either NaClO4 or CrO3 and that in which it was consumed by the oxidation of Cr. Partial melting at the high combustion temperature during SHS of La 1-xSrxMnO3 increased product homogeneity. The electrical conductivity at 1000░C in air of SHS-produced cathode material (of 180 O-1Ěcm-1) matches that of the commercial product made by other processes. However, the SHS process provides much higher productivity and decreases processing time and the consumption of the electrical power. SrFeO3-x and LaCrO3 were the main intermediates and products for SHS of chromium-doped La0.2Sr0.8FeO 3-delta. The final structure was a solid solution of Fe and Sr rich oxides and La and Cr rich oxides. Decreasing the reactant particle size increased the homogeneity of the SHS product and increased the velocity of the propagating combustion front. The SHS produced La0.2Sr 0.8Cr0.2Fe0.8O3-delta had a maximal electrical conductivity of 8.8 O-1Ěcm -1 at 560░C in a pure oxygen. The material, having the highest stability in reducing conditions, had a moderate oxygen permeation rate of 3.35 x 10-9 mol/sĚcm2 at 980░C in an oxygen partial pressure gradient from air to 4 x 10 -5 atm. The homogeneity and particle size of the combustion product of gallium-doped La0.5Sr0.5FeO3-delta may be increased by decreasing the cooling rate of the sample, either by increasing the sample diameter or by controlling the post-combustion temperature. The perovskite oxide maintained its cubic structure at all temperatures (from 20 to 1000░C) in air. However, decomposition occurred at 860░C under a simulated synthesis gas environment (22%CH4+21%CO2+57%H2, oxygen partial pressure of about 10-21 atm). Its maximal electrical conductivity was 142 O-1Ěcm-1 at 580░C under oxygen pressure of 1 atm. This material is suitable for use as a membrane in synthesis gas production, since the thermal expansions in air and reducing conditions are rather close at high temperatures.
Two phase exhaust for internal combustion engine
Vuk, Carl T. (Denver, IA)
An internal combustion engine having a reciprocating multi cylinder internal combustion engine with multiple valves. At least a pair of exhaust valves are provided and each supply a separate power extraction device. The first exhaust valves connect to a power turbine used to provide additional power to the engine either mechanically or electrically. The flow path from these exhaust valves is smaller in area and volume than a second flow path which is used to deliver products of combustion to a turbocharger turbine. The timing of the exhaust valve events is controlled to produce a higher grade of energy to the power turbine and enhance the ability to extract power from the combustion process.
The paper discusses the application of pulse combustion to solid and hazardous waste incineration. otary kiln incinerator simulator was retrofitted with a frequency-tunable pulse combustor to enhance the efficiency of combustion. he pulse combustor excites pulsations in the kiln ...
Control of flame configuration and combustion performance in industrial furnaces
C. Presser; Y. Goldman; J. B. Greenberg; Y. M. Timnat
The influence of geometric and kinematic factors on combustion performance is studied in a liquid fuelled furnace, experimentally and theoretically. By varying the spray axial location, it is possible to produce a more uniform air\\/fuel distribution with an apparent shortening and widening of the flame shape. Increasing the swirl number enhances turbulent mixing, creating a shorter flame in the combustion
A simplified method for determining heat of combustion of natural gas
NASA Technical Reports Server (NTRS)
Singh, Jag J.; Chegini, Hoshang; Mall, Gerald H.
A simplified technique for determination of the heat of combustion of natural gas has been developed. It is a variation of the previously developed technique wherein the carrier air, in which the test sample was burnt, was oxygen enriched to adjust the mole fraction of oxygen in the combustion product gases up to that in the carrier air. The new technique eliminates the need for oxygen enrichment of the experimental mixtures and natural gas samples and has been found to predict their heats of combustion to an uncertainty of the order of 1 percent.