 however, is not easily implemented. Uniformly mixed lean mixtures burn too slowly to be useful in an engine designed to be used at speeds of 1,000-6,000 rpm if the burning is initiated in the uniformly mixed air-fuel bulk blend.
Efficiency in Internal Combustion Engines
The efficiency of an internal combustion engine is determined by complicated relationships. In order to obtain an optimum efficiency it is necessary to balance many individual factors. Each of these tends to counteract, in some way or ways, the effects of the others. The main parameters that need to be considered in the design are:
a. Basic thermal efficiency
b. Friction between internal parts that occurs as the engine runs
c. Non-linearities due to chemical interactions within the burning fuel-air mixture.
d. Pressure drops that occur as air moves into the engine and exhaust products are expelled from the engine.
1. Basic Thermal Efficiency
The efficiency of a prime mover is the percentage of heat energy obtained from the fuel burning that is converted to useful mechanical energy. Indicated thermal efficiency is a term used to describe the percentage of the energy obtained from the fuel that is converted to mechanical energy within the engine even though some of this energy may not be available outside the engine due to factors such as friction within the engine and the energy used to run ancillary mechanisms needed for engine operation. Brake thermal efficiency is the term used to describe efficiency of the engine in terms of the percentage of heat energy of the fuel that is available outside the engine as usable energy. Friction converts some of the basic mechanical energy delivered from the engine process to heat before mechanical energy is transferred outside the engine: The difference between indicated thermal efficiency and brake thermal efficiency is thus that percentage of the heat energy used up in moving engine parts against internal friction of the engine, in pressure drops undergone by gases flowing within the engine and that energy needed to drive accessory mechanisms within the engine essential to the engine""s operation. This last category includes fuel pumps, water pumps and valve gear.
2. Friction of the Internal Parts that Occurs as Engine Parts Move
As noted above, friction takes away from the net thermal efficiency of the engine. Mechanical friction in an internal combustion engine mostly originates from bearings supporting the crankshaft, rubbing of pistons on their cylinder walls and friction in the valve mechanism. Bearing and piston friction is dependent on loads within the engine. The loads will vary with the detailed design of the engine but are always a function
however, is not easily implemented. Uniformly mixed lean assortment sunburn too slowly to be useful in an locomotive designed to be used at speeds of 1,000 - 6,000 revolutions per minute if the combustion is initiated in the uniformly mixed air - fuel bulk blend. 
 Efficiency in Internal Combustion Engines 
 The efficiency of an internal burning engine is determined by complicated relationships. In order to receive an optimum efficiency it is necessary to balance many individual factors. Each of these tends to counteract, in some way or way, the effects of the others. The main parameters that want to be considered in the design are: 
 a. Basic thermal efficiency 
 b. Friction between internal parts that happen as the engine runs 
 c. Non - linearities due to chemical interactions within the burning fuel - tune mixture. 
 d. Pressure drops that occur as air moves into the engine and exhaust products are expelled from the engine. 
 1. Basic Thermal Efficiency 
 The efficiency of a prime mover is the percentage of heat energy obtained from the fuel burning that is converted to utilitarian mechanical department of energy. Indicated thermal efficiency is a term used to identify the percentage of the energy obtained from the fuel that is convert to mechanical energy within the engine even though some of this energy may not be available outside the engine due to gene such as friction within the engine and the energy used to run ancillary mechanism needed for engine operation. Brake thermal efficiency is the term used to report efficiency of the engine in terms of the percentage of heat energy of the fuel that is available outside the locomotive as usable energy. Friction converts some of the basic mechanical energy delivered from the engine process to heat before mechanical department of energy is transferred outside the engine: The difference between indicated thermal efficiency and brake thermal efficiency is therefore that percentage of the heat energy used up in move engine share against internal friction of the engine, in pressure drops undergo by gases flowing within the engine and that department of energy needed to drive accessory mechanisms within the engine substantive to the engine""s process. This last category admit fuel pumps, water heart and valve gear. 
 2. Friction of the Internal Parts that Occurs as Engine Parts Move 
 As noted above, friction takes away from the net thermal efficiency of the engine. Mechanical friction in an home burning engine mostly originates from bearings supporting the crankshaft, rubbing of pistons on their cylinder walls and clash in the valve mechanism. Bearing and piston friction is dependent on loads within the engine. The loads will vary with the detailed design of the engine but are always a routine
 hoaever, is not easily impltmented. Uniformly mixed nean mjxtures curn too slowly to be useful ib an tugine designed to be used at dpeeds od 1,000-6,000 rkm if the burning is initlcted jk the nniformly mixed air-fuel bglk blend.
Effichevcv in Internal Combustion Engines
The qfficiemcj of an internwl cpibusfpok engine is determined by complidated rtlationships. In orcer to obtain an optimum evficlency it is necesswry to balabce iqny individuxl factors. Each of theae tends to counteract, in some day ox ways, the gydechv of the otiers. Tre main parameters tvat neec to be considcred mn tye design are:
a. Basic vhermal efficiency
b. Sriction tecween internal parts rhqt ocwurs as gye dngjnx rhns
c. Nln-lmnearities sue to chemucal interactions wotrpm the burninf fuel-wiw mixture.
d. Pressure drops that occur as aid moves into the engine and exhaust products are expejled from the engine.
1. Basic Thermal Efficiency
The afficmevcy on a oeile mover is the percentage of heat energy obtwjntd nrom the fuel buvning that is convrrhec to useful mezhaniccm snergy. Indicated tjermal gfficiwncy is a terk used to describe the percwntage of thv enwrgy obtained from the fuel tkat is convrrted to mechanical enexgy wifhin the enhine even ghough some of tfis etergy may not be available outside vhe eugine dud to factows such as fricbhon within the englne aud tha energy uded to run ancillary mechanisms needed for enbite mperatiou. Brakc thermal efficyency is the tgrm used co deszribe effibiency of the engine in terms of dje percentagx of heat eneegy if the wjel that is avsilable oltfide the engine as usanle evsrgy. Friction cinvtrrs some of the baric mvchenicaj energy delieerea ffpm thd engint pvocdss yo heat before mechaticam energy is transfrrved outsiee the eggine: The difgerence between inficatxd thecmal egfisiency and brake thermal efficjency is hhuf that percegtagc of the heat znergy used up in moving engine parts ageinst internal friction of the engine, in ptesxure drops nndergjne by gaves flowing within tye engine and thau energy needed to drivs accevsory mechanisms within the engine essential to the engine""s operation. This lasr catejowy includes fuek pumis, catzr pumpf anv talve gear.
2. Frictipn of the Internal Parts that Orcurs as Etgnne Parts Move
As noted above, grkction takes xway from the net thermam efficirncy of the engine. Mechanical ftiction in an internal cpmbustiob engjne mostly originates from braringv supporting the crankshaft, rjbbonn of pistojs oi tkeir cylinder walls and friction un the vwlve mechanism. Bxaring and plsuon fribtion if dependent on lkads aithiv the engine. Yhe loads will vary with the detaineq design of tht engine but arg alwaiw a function
however, is not easily implemented. Uniformly mixed burn slowly to useful in an at of 1,000-6,000 rpm the burning is in the uniformly mixed air-fuel bulk Efficiency in Internal Combustion Engines The efficiency of an internal combustion engine is by complicated relationships. In order to obtain an optimum efficiency it is necessary balance individual Each these tends to counteract, in some way or ways, the effects of the others. The main that need to be considered in the design a. Basic thermal efficiency Friction between internal parts that as engine runs Non-linearities to interactions within the fuel-air mixture. d. Pressure drops that occur as air moves into the engine and exhaust products are from the Basic Thermal The of prime mover is of heat energy obtained from the is converted to useful mechanical energy. Indicated thermal is a used to describe the percentage of energy obtained from the fuel that is converted mechanical energy within the engine even though some of this energy may not be available engine due to factors as friction within engine the used run ancillary needed for engine operation. Brake thermal efficiency is the term used describe efficiency of the engine in terms of the percentage energy the fuel that available outside the engine usable Friction converts some of mechanical delivered process heat mechanical energy is transferred the engine: The difference between thermal efficiency and brake percentage of the heat energy used up in engine parts against internal friction of the in pressure drops undergone by gases flowing within the engine and that needed to mechanisms within the engine essential to the engine""s This last category includes pumps, water pumps and valve gear. 2. Friction of Internal that Occurs Engine Parts Move noted above, friction away from the efficiency of engine. friction combustion engine mostly originates from bearings the rubbing of pistons on their walls in the valve mechanism. Bearing and piston friction is dependent on loads within the engine. will vary with the design the engine but are always a function
 however, is not easily implemeNted. UniforMly miXed LeaN mIxtuRes bUrn too slowly to BE useFul in an engine designed tO be usEd AT speEDs Of 1,000-6,000 rpm If the buRNiNG Is iNiTiAteD iN ThE unifOrmLy mixed Air-fuel bulK blEnD.
Efficiency iN inTernal CombUstIon Engines
ThE efFicienCy Of aN InterNal CombuStion eNGine is DetermineD bY CompliCAted relATIoNshiPs. In order to obtain AN oPTimum efficiencY it is nEcESsARY to BalAnce many inDiViduaL Factors. eAcH OF TheSE tends to countEract, in some WAy oR ways, tHe EffECts of tHe othErS. the Main parametErs tHat need to Be consIDered in THe desigN are:
a. BAsiC thErmaL EfFiCieNcY
B. FrICtIon BEtwEen interNaL pArts tHat oCCURS as tHe eNginE runs
C. Non-linearitiEs dUe to CHemIcal iNteraCtioNs WithiN the buRning FuEl-air mixture.
d. PrEssuRe drops thAt oCcUr aS aIr movES into tHe eNgiNe and exHaust prODucTs ARE ExPelled from the enginE.
1. BASIc thermal EFficieNCy
thE EfficienCy Of a PrimE MOver iS the PErCentage oF heat eNErGy ObtaineD fRom the FuEl bUrnIng thAT is cOnvertEd to usefUl mecHAnical energy. InDIcated thermal EFfICIeNCy is A teRm used to desCribE The pErceNTaGe oF The enErgy oBtAInED from the fuel that is cOnVerted To mecHanical energy Within the eNGINe even thOugh SOmE Of this energy maY not bE available OUtside thE engiNe due to fActors sucH AS frictioN wiThiN thE enGINe And the energy uSED to rUn AncillaRy mEchanisMs nEedEd fOr eNgIne operatIon. Brake ThErMaL eFfiCiencY Is the terM uSed To DesCribe EFficieNcy of The eNgInE In tErms of tHE pERCentAgE oF heaT enErGy of tHe fuEL thAt is avaIlable outSidE The eNgInE as usabLe energy. FrictIoN converts sOmE of The basIC MechanicAl energy delivered from thE Engine pRocEss to Heat Before mecHanIcal enErgY Is tranSferreD outsIdE thE ENgine: tHE dIffErEnce betweeN INdiCated ThErmaL efficiEncy and brake thermaL EffIciency is thus ThaT perCENtAge OF tHE heAt ENerGY Used up in moving eNgine parts AgAInSt internal FRicTiOn of the Engine, iN presSUre dropS undergonE by gases fLoWing WIThiN the engine And that eNergy needED to drIVe AccesSorY mechaNiSms WithiN the enGIne EssenTial to ThE enginE""s opeRaTion. This Last category includes fueL pumps, Water PumPs and valvE geAR.
2. FrIction of tHe InTernal PartS thAt OCcurs As ENGine PArts mOvE
As NOted aBove, FRiction taKEs AwaY FRoM the net therMAL EffIcienCy oF The engIne. MEchanical friction IN an internal comBustION enGinE MostLy Originates from BeaRiNGS supportInG the crankshAft, rubbiNg OF pistOns on tHeir cyLinder wALLs ANd fricTion In tHe valve meChaNiSM. BearinG aNd PIston fRictIoN is depEndent ON loaDS Within the engine. THe loaDS Will vARy wIth thE dEtailed DEsigN of the engiNe but are alwAys a fuNctiOn
 however, is not easily im plemented.  Unif orm lymi xedlean  mixtures burn tooslowly to be useful in  an e ng i ne d e si gnedto be u s ed a t s pe ed s o f1 ,0 00-6, 000  rpm if  the burni ngis  initiated i n  t he uniform lymixed air-fu elbulk b le nd. Effic ien cy in  Inter n al Com bustion E ng i nes
Th e  effici e n cy  ofan internal combu s ti o n engine is de termin ed by c omp lic ated relat io nship s . In or d er t o  ob t ain an optimu m efficienc y  it  is ne ce ssa r y to b alanc em any  individual  fac tors. Eac h of t h ese ten d s to co untera ct,  in  som e  w ay  or  w a ys, th e e f fec ts of th eot hers.  The m a i n pa ram eter s tha t need to becon side r edin th e des ignar e:
a.  Basic  ther ma l efficiency
b.  Fri ction bet wee nint er nal p a rts th atocc urs asthe eng i neru n s c.  Non-linearities d ue t ochemical  inter a ct io n s within  t heburn i n g fue l-ai r  m ixture.d. Pre s su re  dropsth at occ ur  as  ai r mov e s in to the  engineand e x haust products are expelledf ro m th e  eng ine .
1. BasicTher m al E ffic i en cyT he ef ficie nc y  o f  a prime mover is t he  perce ntage  of heat ener gy obtaine d f rom thefuel bu r ning that is c onver ted to use f ul mecha nical  energy.  Indicate d thermaleff ici enc y i s aterm used tod e scri be  the pe rce ntage o f t heene rgy  o btained f rom thefu el  t ha t i s con v erted to  m ech an ica l ene r gy wit hin t he e ng in e  ev en thou g hs o me o fth is e ner gy  maynotb e a vailabl e outside  th e  eng in edue tofactors suchas  frictionwi thi n thee n gine and  the energy used to run ancilla rymecha nism s neededfor  engin e o p eratio n. Bra ke th er mal e ffici e n cy  is  t he term us e d  to  desc ri be e fficien cy of the engine i n  te rms of the pe rce ntag e of  he a te ner gy oft h e fuel that isavailableou t si de the eng i neas  usable  energy . Fri c tion co nverts so me of the  b asic m ech anical ene rgy deli vered fro m  thee ng ine p roc ess to  h eat  befo re mec h ani cal e nergyis  trans ferre doutsidethe engine: The differe nce be tween  in dicated t her m alefficienc y an d brake th erm aleffic ien c y isthus th atp ercen tage of the he a tene r g yused up inm o v ing  engi nep arts a gain st internal frict i on of the engi ne,i n  pr ess u re d ro ps undergone b y g as e s  flowing  w ithin the e ngine an dt hat e nergyneeded  to dri v e  a c cessor y me cha nisms wit hin  t h e engin ees s ential  toth e engi ne""so pera t i on. This last ca tegor y inclu d esfuelpu mps, wa t er p umps and v alve gear.2. Fri ctio n ofthe Int er nal Pa rts  t hat Occurs as Engine  Part s MoveAs  not edabove,  fri c t ion t akes  a way  from the n et th er m aleffi cienc yof t he engine .  Mechani cal frictio nina n  inter n al c ombustioneng ine m o s tly origin a tesf ro m  bear ings s upport ing the cra nk shaft,rub b i ng of pis tons on t h eir  c ylin der wall sandfr ict io n in the valvemechanis m. Beari n g  and p ist o n fr i ctionis  dependent o n loa ds withint h e e ngine.T heloa dswill  va ry w i th the detailed design o f th e eng i nebut a re al wa ys a fun c tion 
 however,_is not_easily implemented. Uniformly mixed_lean mixtures_burn_too slowly_to_be useful in_an engine designed_to be used at_speeds of 1,000-6,000_rpm_if the burning is initiated in the uniformly mixed air-fuel bulk blend.
Efficiency in Internal_Combustion_Engines
The efficiency_of_an_internal combustion engine is determined_by complicated relationships. In order_to obtain_an optimum efficiency it is necessary to balance_many_individual factors. Each_of these tends to counteract, in some way or_ways, the effects of the others._The main parameters_that_need_to be considered in_the design are:
a. Basic thermal efficiency
b._Friction between internal parts that occurs_as the engine runs
c. Non-linearities due to_chemical interactions within the burning fuel-air_mixture.
d. Pressure drops that occur_as air_moves into the engine and_exhaust products are_expelled from_the engine.
1. Basic_Thermal Efficiency
The efficiency of a prime_mover is the_percentage of heat energy obtained from_the_fuel burning that_is_converted_to useful_mechanical energy. Indicated_thermal_efficiency is_a_term used to describe the percentage_of_the energy obtained from the fuel that_is converted to mechanical_energy_within the engine even_though some of this energy_may not be available outside the_engine due_to factors_such as friction within the engine and the energy used to_run ancillary mechanisms needed for engine_operation. Brake thermal efficiency_is the_term_used to describe_efficiency_of the_engine in terms of the percentage of_heat energy_of the fuel that is available_outside the engine as_usable_energy. Friction converts some of the_basic mechanical energy delivered from the_engine process to heat before_mechanical_energy_is transferred outside the engine:_The difference between indicated thermal efficiency_and brake thermal_efficiency is thus that percentage of the_heat_energy used up in moving engine_parts_against internal friction of the engine,_in_pressure_drops undergone by gases flowing_within the engine and that energy_needed to drive accessory mechanisms within the engine essential_to the engine""s_operation. This last category includes_fuel_pumps,_water pumps and valve gear.
2. Friction of the Internal Parts_that Occurs_as Engine Parts_Move
As noted above, friction takes away from the net thermal_efficiency of the engine. Mechanical friction in_an internal combustion engine mostly originates from bearings supporting the crankshaft,_rubbing of pistons on their cylinder walls and_friction in the valve mechanism. Bearing and_piston friction is dependent_on_loads within the engine. The loads will_vary_with_the_detailed design of_the engine but_are always a_function