BACKGROUND  
       [0001]     The present invention pertains to engines and particularly to exhaust gas recirculation. More particularly, the invention pertains to the temperature of the exhaust gas being recirculated.  
       SUMMARY  
       [0002]     The invention relates to a heat exchanger between the exhaust gas being recirculated to the intake manifold and exhaust gas moving towards an aftertreatment system. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0003]      FIG. 1  is an overview layout of a heat exchange scheme for an engine.  
         [0004]      FIG. 2  shows a more detailed layout of an engine with an exhaust and intake system, and a heat exchange circuit between the recirculated gas and post-turbine gas.  
     
    
     DESCRIPTION  
       [0005]      FIG. 1  is a schematic of an engine system  10  having a heat exchanger system  41  between an exhaust manifold  15  via an exit conveyance  17  at an output conveyance  36  and an output conveyance  32  of a flow control mechanism  16 . The heat transfer system  41  may contain a heat transfer unit  27  and a heat transfer unit  34  connected by a conveyance  37  and  38 . Heat may be moved from one unit to another by a fluid  39 . Air  23  may enter a conveyance  31  and enter an intake manifold  13  of intake system  43  of an engine  11 . The engine  111  may output an exhaust  14  into an exhaust manifold  15  and then onto an exit conveyance  17  of exhaust system  45 . Some of the exhaust gas  14  may go through a re-circulative conveyance  28  (commonly known as exhaust gas recirculation (EGR)) to the flow control mechanism  16  which controls the flow of exhaust gas  14  through it. The output conveyance  32  may carry some exhaust gas  14 , as permitted by mechanism  16 , which goes to the heat transfer unit  27 . The exhaust gas  14  may exit the heat transfer unit  27  into a conveyance  33  which leads the gas  14  into the intake system  43  and mix with air  23  into a combination input air  12  which may enter the engine  11 . Fuel may be added in the intake system  43  or in the engine  11 . The exhaust gas  14  from conveyance  17  may go through the heat transfer unit  34 . The exhaust gas may proceed out of unit  34  into the output conveyance  36 .  
         [0006]     In an engine, for example, a turbo-charged diesel engine, there may be a preference to cool the exhaust gas recirculation (EGR) flow to reduce pollutant emissions from engine combustion. Also, there may be a preference to increase the post-turbine exhaust temperature at times to facilitate a regeneration of an aftertreatment system for the engine. The aftertreatment system may be, for example, a diesel particulate filter (DPF) which requires periodic regeneration to oxidize (burn off) the collected soot or particulate matter (PM) and may require a minimum temperature to achieve light-off of the collected soot. The aftertreatment system may also or instead be a diesel oxidation catalyst (DOC), and/or a continuously regenerated trap (CRT), but is not limited to these examples.  
         [0007]     The preference for cooling the EGR and heating the post-turbine exhaust may accomplished with heat transfer. Unwanted heat may be taken from the EGR path and transferred to the post-turbine exhaust. This is thermodynamically feasible since the post-turbine exhaust is about 200 degrees C. cooler than the gas in the EGR path.  
         [0008]      FIG. 2  shows the heat transfer accomplishable by connecting the exhaust and EGR paths thermally with a heat exchanger approach in the engine system  10 . Engine  11  may intake air and exhaust gas mixture  12  from an intake manifold  13 , provided the EGR valve  16  is open. The mixture  12  may have fuel added and go to one or more cylinders of engine  11  and be ignited into an expanding gas to push the one or more cylinders resulting in turning a crankshaft having a power output for vehicle propulsion or other purposes. The expanded and burnt gas  14  may exit engine  11  and go into the exhaust manifold  15 . Some of the exhaust gas  14  from manifold  15  may go to the EGR valve  16  via conveyance mechanism  28  and the remaining gas  14  may go through the exhaust pipe  17  to a turbine  18  of a turbo-charger  19  (which may, for instance, be a variable geometry turbo-charger). The turbine  18  may be rotated by a flow of exhaust gas  14  going through it. Turbine  18  may be mechanically connected to, as shown by a line  21 , a compressor  22 . The rotation of turbine  18  may result in a rotation of a compressor wheel or the like in compressor  22  which compresses incoming air  23  taken in through an input port  24  and outputs the compressed air  23  to an intercooler  25  via conveyance mechanism  29 . When air  23  is compressed, it may have a significant increase in temperature. The intercooler  25  may cool the air  23  so that it is denser as it enters intake manifold  13  via conveyance mechanism  31  from inter-cooler to mix with an exhaust gas  14  for mixture  12 . Fuel may be added to mixture  12  in the manifold  13 . Alternatively, the fuel may be mixed with the air in the cylinder head of the engine  11  via a fuel injector. Also, exhaust gas  14  may be added to the incoming air  23  for a mixture  12  in manifold  13  for more effective combustion and lower emissions from engine  11 .  
         [0009]     It may be advantageous to have cooler exhaust gas  14  enter the intake manifold  13 . Further, it may be advantageous to heat the exhaust gas  14  coming out of turbine  18  in order to facilitate a regeneration of an emissions aftertreatment system  26 , which may be, for example, a diesel particulate filter (DPF). A heat transfer unit  27  may be inserted in the path of gas  14  going from EGR valve  16  to manifold  13 , and between conveyance mechanisms  32  and  33 . Another heat transfer unit  34  may be inserted in path of exhaust gas  14  from turbine  18  to aftertreatment system  26 , and between conveyance mechanisms  35  and  36 .  
         [0010]     Heat transfer units  27  and  34  may be connected to each other by conveyance mechanisms or tubes  37  and  38 . A fluid  39  may flow from heat transfer unit  27  to heat transfer unit  34  via tube  37 . Fluid  39  may flow from heat transfer unit  34  to heat transfer unit  27  via tube  38 . A pump  42  or fluid mover may facilitate a flow or movement of fluid  39  in tubes  37  and  38 . Heat transfer units  27  and  34  may be devices having tubes or the like woven in the path of the exhaust gases  14 . For instance, if the fluid  39  in tube  37  flows through heat transfer unit  34  and has a temperature higher than the temperature of the exhaust gas  14 , then heat may transfer from fluid  39  to exhaust gas  14  via heat transfer unit  34 . As a result, fluid  39  may be cooled down in heat transfer unit  34  and returned to heat transfer unit  27  through tube  38  at a temperature lower than the temperature of fluid  39  in tube  37 . Also, exhaust gas  14  may be heated up in heat transfer unit  34  by the hotter fluid  39 . Fluid  39  in tube  38  may flow through heat transfer unit  27 . If the fluid  39  from tube  38  flows through heat transfer unit  27  and has a temperature lower than the temperature of the exhaust gas  14  there, then heat may transfer from the exhaust gas  14  to fluid  39  via the heat transfer unit  27 . As a result, fluid  39  may heated up in heat transfer unit  27  and go to heat transfer unit  34  through tube  37  at a temperature higher than the fluid  39  in tube  38 . Also, exhaust gas  14  may be cooled down in heat transfer unit  27  by the cooler fluid  39 . Thus, the temperature of exhaust gas  14  in conveyance mechanism  33  may be cooler than the temperature of gas  14  in conveyance mechanism  32 . Conversely, the temperature of the exhaust gas  14  in conveyance mechanism  36  may be hotter than the temperature of the exhaust gas  14  in conveyance mechanism  35 . However, if the exhaust gas  14  going through heat transfer unit  34  is hotter than the exhaust gas  14  going through heat transfer unit  27 , then there may be a heat transfer from the exhaust gas  14  exiting turbine  18  to the exhaust gas  14  exiting the EGR valve  16 , instead. The latter may occur with a cold engine  11  or cold ambient air  23  entering the intake manifold  13 . If there is no reason for the latter, the flow of fluid  39  need not occur.  
         [0011]     Fluid  39  flow in tubes  37  and  38  and through heat transfer units  27  and  34  may be facilitated or halted by pump  42  or other similar mechanism. If heat transfer is not desired from one heat transfer unit to the other heat transfer unit, then the flow of fluid  39  may be halted. Tubes  37  and  38 , fluid  39  and heat transfer units  27  and  34  may have physical properties and design characteristics to appropriately withstand the high temperatures as incurred by the respective components of a heat exchanger system  41 . The exhaust gas  14  of the EGR valve  16  path into conveyance mechanism  32  may typically have a temperature around 850 degrees K (577 degrees C., 1070 degrees F.). The exhaust gas  14  of the post-turbine  18  path in conveyance mechanism  35  may typically have a temperature around 700 degrees K (427 degrees C., 800 degrees F.).  
         [0012]     Engine system  10  may have a processor  40 , such as an engine control unit (ECU) or computer, connected to various components of the system. Processor  40  may be connected to components of engine  11  for measuring temperature, timing and other parameters and for controlling various aspects and parameters of engine  11  operations. Processor  40  may also be connected to sensors at the intake manifold  13  to measure temperature, pressure, flow, fuel mixture and to control air and fuel mixture intake, connected to sensors at the exhaust manifold  15  to measure temperature and flow, and connected to sensors at turbine  18  to measure temperature and to actuators to control the variable geometry components of the turbine. Processor  40  also may be connected to EGR valve  16  to control its opening and measure flow through it and temperature. Processor  40  may be connected to pump  42  to control the flow of fluid  39 . Processor  40  may be connected to sensors at heat transfer unit  27  to measure in and out temperatures of unit  27 , so as to appropriately monitor and control the flow of fluid  39  through the unit  27 . Processor  40  may be connected to sensors at the heat transfer unit  34  to measure in and out temperatures and note fluid  39  flow through the unit. Also, processor  40  may be connected to sensors and an actuator at the inter-cooler  25  to measure temperatures and control the effectiveness of the inter-cooler  25  on the incoming air  23 . Sensors and actuators are not necessarily shown in the Figures.  
         [0013]     Processor  40  may, in particular, monitor and control the effects of the heat exchange system  41 . Also, engine  11  and other associated components may be monitored and controlled for attaining appropriate conditions and operation of engine  11 .  
         [0014]     In the present specification, some of the matter may be of a hypothetical or prophetic nature although stated in another manner or tense.  
         [0015]     Although the invention has been described with respect to at least one illustrative example, many variations and modifications will become apparent to those skilled in the art upon reading the present specification. It is therefore the intention that the appended claims be interpreted as broadly as possible in view of the prior art to include all such variations and modifications.
A heat transfer system in an engine for transferring heat from the recirculated exhaust gas to an output of an engine exhaust system. The heat transfer may cool the recirculated exhaust for reduced emissions from engine combustion and, at the same time, increase the output exhaust temperature to facilitate regeneration of an exhaust aftertreatment system. There may a heat transfer unit at the output of an exhaust gas recirculating valve connected to a heat transfer unit at the output of the exhaust system.