Abstract:
An exhaust gas recirculation (EGR) system for an engine in which a portion of the exhaust gas is recirculated from an exhaust port of the engine into an intake port of the engine. The EGR system includes an exhaust gas recirculation line connecting said exhaust port of said engine to said intake port of said engine; a turbine disposed along the recirculation line; and a motor generator in operative communication with the turbine. The pressure and flow of a portion of said exhaust gas produced by said engine and recirculated from said exhaust port to said intake port is used to operate the turbine and the motor generator derives electric power from the operation of the turbine. In an embodiment, the motor generator can be used to drive the turbine to manipulate EGR flow. A method for recovering energy in connection with an EGR system is also disclosed.

Description:
BACKGROUND  
       [0001]     1. Technical Field  
         [0002]     The present invention relates to an exhaust gas recirculation (EGR) system for internal combustion engines.  
         [0003]     2. Background  
         [0004]     Increasing demands are commonly placed on engine and vehicle manufacturers to provide engines that provide improved performance, reliability, and durability while at the same time reducing undesirable emissions. Diesel engines, particularly those used for heavy duty, often employ extensive amounts of EGR.  
         [0005]     Moreover, with turbocharged engines that include EGR, EGR is typically performed by allowing some portion of the exhaust gas in the exhaust passage to flow toward an intake passage through an EGR flow path. The recirculation of exhaust gas by-products into an intake air supply of an internal combustion engine, which can then be reintroduced into an engine cylinder, can reduce the concentration of oxygen therein which, in turn, can lower the maximum combustion temperature within the cylinder and slow the chemical reaction of the combustion process, thereby decreasing the formation of nitrous oxides (NOx).  
         [0006]     However, because exhaust gas is at an elevated temperature and must typically be cooled before returning to the air inlet system, additional and substantial cooling systems are commonly employed for that purpose. Generally, such systems involve the inclusion of an additional (and commonly enlarged) radiator/heat exchanger. However, the inclusion of such additional equipment can, among other things, raise packaging design issues and necessitate the removal of an increased amount of heat from the system.  
         [0007]     Further, in the past, such exhausted energy was not always considered worth recovering. However, today, with the increasing use of EGR and the expanding potential uses for recovered energy, for example, in connection with hybrid technologies, there is an interest in both removing more and more heat or energy from EGR systems and recovering it for beneficial purposes.  
       SUMMARY  
       [0008]     An exhaust gas recirculation (EGR) system for an internal combustion engine in which a portion of the exhaust gas produced by the engine is recirculated from an exhaust port of the engine into an intake port of the engine. The EGR system includes an exhaust gas recirculation line connecting said exhaust port of said engine to said intake port of said engine; a turbine disposed along the exhaust gas recirculation line; and a motor generator in operative communication with the turbine. The pressure and flow of a portion of said exhaust gas produced by said engine and recirculated from said exhaust port to said intake port is used to operate the turbine and the motor generator derives electric power from the operation of the turbine. In an embodiment, the motor generator can be used to drive the turbine to manipulate EGR flow. A method for recovering energy in connection with an EGR system for an internal combustion engine is also disclosed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, wherein:  
         [0010]      FIG. 1  is a schematic illustration of an EGR system according to an embodiment of the present invention; and  
         [0011]      FIG. 2  is a schematic illustration of an EGR system according to another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0012]     Referring to  FIG. 1 , an exhaust gas recirculation (EGR) system  10  according to an embodiment of the present invention is shown. In the illustrated embodiment, the EGR system  10  is connected to an internal combustion engine  20  having an exhaust port  22  and an intake port  24 . However, the engine  10  need not be limited to a single exhaust port and a single intake port and may include a plurality of exhaust ports and/or intake ports. For example, and without limitation, the illustrated engine includes a second exhaust port  26  and a second intake port  28 .  
         [0013]     As shown in  FIG. 1 , system  10  is connected to engine  20 , the system  10  including an exhaust gas recirculation line  30 ; a turbine  40 ; and a motor generator  50 . If desired, the system  10  may optionally include a cooler  60 .  
         [0014]     The system  10  may further include a control device for controlling the amount of exhaust gas that is permitted to flow from the engine  20  into the exhaust gas recirculation line  30 . The control device may include, for example, a conventional valve or other flow-control device suitable for the functional environment. For example, as illustrated in  FIGS. 1 and 2  in phantom line format, a control valve  35  may be optionally included. The control valve  35  may be disposed along the recirculation line  30  between the exhaust port of the engine and the turbine. The control valve  35  is shown receiving exhaust flow from the engine. With such a control valve, exhaust from the engine exhaust port can be directed to turbine  40  or, if desired, could instead be routed past the turbine and on along the recirculation path. The control valve may include, for example, any number of conventional valves including, without limitation, a four-way valve that could either be of the poppet, butterfly, or other type. Moreover, exhaust that has been directed to (and through) turbine  40  can, for example as illustrated, be directed back through a control valve  35 , or could instead bypass the valve and be directed onward along the illustrated recirculation line. Further, the control valve  35  can, if desired, be configured to help prevent undesirable contaminants from flowing through the system.  
         [0015]     The exhaust gas recirculation line  30  serves to provide a fluid connection from exhaust port  22  to intake port  24  of engine  20 . However, as used herein, the term recirculation line is to be interpreted broadly and is not limited to a single contiguous line, and, if desired, may be comprised of individual line segments that form a substantially continuous flow path. As generally illustrated, turbine  40  is disposed along the exhaust gas recirculation line  30 , and motor generator  50  is in operative communication with the turbine  40 .  
         [0016]     In an embodiment, the pressure and flow associated with the portion of exhaust gas flowing from engine exhaust port  22  is used, at least in part, to operate the turbine  40 . For example, without limitation, at mid throttle, from about 30% to about 40% of the exhaust may be directed for EGR flow associated with the exhaust gas recirculation line  30 . Moreover, as used herein, the term “turbine” is meant to include mechanisms for translating the flow of exhaust gas into kinetic energy, for example, by rotating a plurality of blades associated with the turbine.  
         [0017]     A motor generator  50  may be in operative communication with the turbine, whereby energy, such as the kinetic energy associated with the operation of the turbine, can be transformed into electrical energy by the motor generator  50 . Conversely, if desired, the motor generator  50  may supply power to the turbine that can be used to force gas through or along the exhaust gas recirculation line  30 . The motor generator  50  may be, for example and without limitation, a conventional motor generator that is suitable for deriving electrical power from the operation of the turbine  40  and, if desired, also provide power to operate the turbine  40  (for example, in a “pump” mode).  
         [0018]     The flow of the exhaust gas through or past turbine  40  will typically reduce or lower the temperature associated with the exhaust gas flowing thereby or therethrough. However, as previously noted, if desired a cooler  60 , may be directly integrated into the flow path, selectably activated, or, if an optional route by-pass (not shown) is included, selectably introduced into the system  10  and the flow of the exhaust gas. The cooler  60  can serve to further reduce the temperature of the exhaust gas prior to their reentry into the intake of the engine  20 .  
         [0019]     As generally illustrated in the embodiment shown in  FIG. 1 , the EGR system  10  may further include a second exhaust gas recirculation line  70 . The second exhaust gas recirculation line  70  may serve to provide a fluid connection from second exhaust port  26  to a second intake port  28  of engine  20 . Although the exhaust port  22  and second exhaust port  26  are depicted as separate ports in connection with engine, those of skill in the art will recognize that the ports may take the form of a single port and after exiting the engine the associated lines may divert into the exhaust gas recirculation line  30  and the second exhaust gas recirculation line  70 , and further that the amount of flow to either line may be selectably controlled, such as by a valve or other flow device.  
         [0020]     In the embodiment illustrated, a turbo-charging device  80  is shown disposed along a portion of the path of the second exhaust gas recirculation line  70 . The “inlet” and “exhaust” of ambient or atmospheric gas(es) associated with the turbo-charging device are generally noted in the figure. It should be noted that the present invention is not limited to any specific type of turbo-charging device and the turbo-charging device may comprise a wide array of conventional turbochargers or similar devices used to serve similar purposes.  
         [0021]     With continued reference to  FIG. 1 , and the flow path illustrated in connection with second gas recirculation line  70 , the system  10  may optionally further include an after-cooler  90 . The after-cooler  90  may be disposed along the second gas recirculation line  70  following the turbo-charging device  80 , i.e., between the turbo-charging device  80  and second intake port  28 . In a similar fashion to the cooler  60 , previously discussed, after-cooler  90 , may be directly integrated into the flow path, selectably activated, or, if an optional route by-pass (not shown) is included, selectably introduced into the system  10  and the flow of the exhaust gas. The cooler  60  can serve to further reduce the temperature of the exhaust gas prior to their reentry into the intake of the engine  20 .  
         [0022]     As previously noted, the operation of the turbine associated with the flow of exhaust gas by or through turbine  40  can be transformed into electrical energy by the motor generator. That energy may thereafter be provided to, for example, one or more batteries to be stored or, instead, may be used or routed to directly, or indirectly, power or provide supplemental power to various components or systems associated with a vehicle.  
         [0023]     Moreover, during periods when there is less than the desired amount of flow of exhaust gas through or within the exhaust gas recirculation line  30 , the motor generator  50  can be used to supply power to the turbine that can be used to manipulate the exhaust flow in the system, for example, by forcing an increased flow or amount of exhaust gas through or along the exhaust gas recirculation line  30 . One of skill in the art will readily recognize that the EGR system associated with the present invention may include a controller (not shown) that is in communication with the motor generator  50  that can, if desired, monitor the flow of exhaust gas associated with the system at one or more positions along the flow path and control the operation of the turbine and/or the motor generator as desired. For example, without limitation, the controller may be programmed to meter or control the flow exhaust gas through the exhaust gas recirculation line according to select or specified engine requirements.  
         [0024]     Turning to  FIG. 2 , another embodiment of an EGR system  10   a  is shown. Many of the elements associated with  FIG. 2  have been previously illustrated and discussed in connection with  FIG. 1  and, for ease of reference, the numbering scheme has generally been maintained.  
         [0025]     The embodiment of the invention shown in  FIG. 2  is similar to that illustrated in  FIG. 1 . However, as readily seen, system includes an intake line  100 , and flow of gas(es) introduced from the second exhaust gas recirculation line  70  now join the flow of exhaust gas (“return”) flow from the exhaust gas recirculation line  30 . As shown, the intake line  100 , which may be part of the second exhaust gas recirculation line  70 , or may simply be a component or branch thereof, is in fluid communication with the exhaust gas recirculation line. The intake line  100  may connect to or may otherwise be disposed along a portion of the exhaust gas recirculation line  30  following the motor generator  50 , i.e., between the motor generator  50  and one or more engine intake ports, for example, common engine intake port  102 . If an after-cooler  90  is included in the system  10 , the intake line  100  may connect to or may otherwise be disposed along a portion of the exhaust gas recirculation line  30  before the after-cooler  90 , i.e., between the motor generator  50  and the after-cooler  90 .  
         [0026]     Consequently, an embodiment of the EGR system of the present invention can, if desired, serve to (a) recover energy (in the form of electricity) from energy associated with exhaust gas that would ordinarily need to be removed from the system, which may involve special or larger components and additional handling; and/or (b) the same components or hardware associated with the system can function or serve as an EGR pump.  
         [0027]     The present invention has been particularly shown and described with reference to the foregoing embodiments, which are merely illustrative of the best modes for carrying out the invention. It should be understood by those skilled in the art that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention without departing from the spirit and scope of the invention as defined in the following claims. It is intended that the following claims define the scope of the invention and that the method and apparatus within the scope of these claims and their equivalents be covered thereby. This description of the invention should be understood to include all novel and non-obvious combinations of elements described herein, and claims may be presented in this or a later application to any novel and non-obvious combination of these elements. Moreover, the foregoing embodiments are illustrative, and no single feature or element is essential to all possible combinations that may be claimed in this or a later application.