Abstract:
One embodiment is a unique system which is operable to provide a mixture of charge air and exhaust to an internal combustion intake at a sub-ambient temperature. Further embodiments, forms, objects, features, advantages, aspects, and benefits shall become apparent from the following description and drawings.

Description:
BACKGROUND 
       [0001]    Present approaches to exhaust gas recirculation (“EGR”) suffer from a variety of drawbacks, limitations, disadvantages and problems including those respecting cooling, circulation, efficiency and others. There is a need for the unique and inventive EGR apparatuses, systems and methods disclosed herein. 
       SUMMARY 
       [0002]    One embodiment is a unique system which is operable to provide a mixture of charge air and exhaust to an internal combustion engine intake at a sub-ambient temperature. Further embodiments, forms, objects, features, advantages, aspects, and benefits shall become apparent from the following description and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0003]      FIG. 1  is a schematic of an exhaust gas recirculation system for an internal combustion engine. 
           [0004]      FIG. 2  is a schematic of an exhaust gas recirculation system for an internal combustion engine. 
           [0005]      FIG. 3  is a schematic of an exhaust gas recirculation system for an internal combustion engine. 
           [0006]      FIG. 4  is a schematic of an exhaust gas recirculation system for an internal combustion engine. 
           [0007]      FIG. 5  is a schematic of an exhaust gas recirculation system for an internal combustion engine. 
           [0008]      FIG. 6  is a schematic of an exhaust gas recirculation system for an internal combustion engine. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the figures and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Such alterations and further modifications in the illustrated embodiments, and such further applications of the principles of the invention as illustrated therein are contemplated as would occur to one skilled in the art. 
         [0010]    With reference to  FIG. 1 , there is illustrated internal combustion engine system  100  which includes engine  110 . In the illustrated embodiment, engine  110  is an in-line six-cylinder diesel engine whose cylinders are flow coupled with an intake manifold  111  and an exhaust manifold  112 . A number of additional engine configurations are also contemplated, for example, more or fewer cylinders might be present, the cylinder configuration could be a V configuration or a flat configuration, the engine might combust fuels other than or in addition to diesel fuel, spark ignition or other types of ignition might be used, and/or configurations other than reciprocating piston configurations such as rotary engine configurations could be used. Depending on the engine configuration, there may be additional manifolds, split manifolds, or one or more cylinders might be ported independent of a manifold. 
         [0011]    During engine operation exhaust is expelled to exhaust manifold  112  which provides exhaust to EGR cooler  130  and to turbine  121  of turbocharger  120  via the illustrated exhaust conduits. Turbine  121  is preferably a variable geometry turbine but could also be another type of turbine, for example, a variable nozzle turbine, a fixed geometry turbine, an internally wastegated turbine, or an externally wastegated turbine. As shown in the illustrated embodiment, exhaust flows from exhaust manifold  112  through an exhaust conduit and a portion of the exhaust is then routed through a conduit leading to EGR cooler  130 , while another portion of the exhaust is routed to drive turbine  121  of turbocharger  120 . Exhaust may also be routed through separate conduits coupled to exhaust manifold  112 , one leading to an EGR cooler and the other leading to turbine  121 . The illustrated embodiment shows a high pressure loop EGR flow path in which exhaust gas is recirculated from a location upstream of turbine  121  to a location downstream of compressor  122 . Other embodiments contemplate low pressure loop EGR flow paths. Additional embodiments contemplate supercharging systems which utilize a compressor driven by means other than an exhaust turbine such as, for example, an electric motor, a drive shaft, a drive belt, a hydraulic drive, a pneumatic drive or a combination thereof. Additional embodiments contemplate supercharging systems with multiple compression stages such as series turbochargers, or other staged compressor configurations. Furthermore, coolers may be present between or after compression stages. 
         [0012]    Turbine  121  is coupled to and drives compressor  122  to intake fresh air (which may optionally be filtered) and to output compressed charge air which is then routed to charge air cooler  150 . EGR pump  148  is operable to pump exhaust form EGR cooler  130  to EGR cooler  155 . EGR pump  148  is preferably a rotary centrifugal compressor which could be driven by a belt, an electric motor, a turbine, a pneumatic drive source, a hydraulic drive source, or a combination thereof. Additional embodiments contemplate that EGR pump  148  could be another type of pump, for example, a reciprocating pump, or a vane pump. EGR cooler  130  is preferably a parallel flow cooler and preferably utilizes coolant which circulates through a cooling circuit to cool exhaust gas within EGR cooler  130 , but could also be another type of cooler, for example, a counterflow cooler or a cooler that dissipates heat to the surrounding environment. The coolant is preferably engine coolant which is circulated by an engine coolant pump. The coolant could also be other coolant which is circulated through a separate cooling circuit by a separate pump. 
         [0013]    From EGR pump  148  exhaust is routed to EGR cooler  155 . EGR cooler  155  preferably cools exhaust flowing through it by dissipating heat to the surrounding environment, typically ambient air. The ambient air could be ram air which flows past EGR cooler  155  due to vehicle motion, or forced air which is driven by a fan. Additional embodiments contemplate use of alternate types of coolers. For example, cooler  130  could cool using a gas flowing or expanding through a coolant circuit, or could be an ambient type cooler similar to cooler  155 . Furthermore, cooler  155  could include a cooling circuit through which liquid or gas coolant is circulated to cool EGR. Additionally, charge air cooler  150  could be any of the foregoing types of coolers. Either or both of charge air cooler  150  and EGR cooler  155  may optionally include bypass valves  149  and  154  which can be controlled (for example by an ECM, ECU or other controller) to partially or completely bypass flow around their respective coolers. EGR cooler  130  may also optionally be provided with a bypass valve and bypass flowpath. 
         [0014]    From EGR cooler  155  exhaust is routed to expander  168 . Expander  168  allows exhaust gas to expand and can preferably extract work from the expansion of exhaust gas. Expander  168  could be, for example, a turbine with a shaft or other mechanical connection to EGR pump  148 , a vane type expander, a piston-type expander, or any other configuration operable to allow expansion of exhaust and extract work from the expansion. Extracted work can be received by an electric generator, a hydraulic pump, a mechanical shaft or some other component and can be provided for immediate use by EGR pump  148 , or delivered to the crankshaft of engine  100 , for example by a flywheel motor-generator, or received for storage in a battery, a capacitor such as a super-capacitor, an ultracapacitor or an electrochemical double layer capacitor, a hydraulic accumulator, or another energy-storage device. Flow from charge air cooler  150  and expander  168  is supplied to intake manifold  111  and then to the cylinders of engine  110 . While it is preferred that expander  168  can extract work from the expansion of exhaust gas, certain embodiments may omit this capability. While it is preferred that expander  168  be present to allow exhaust gas to expand, certain embodiments may omit expander  168  and have a connection from the outlet of EGR cooler  155  or its bypass to intake manifold  111 . 
         [0015]    System  100  may be operated to provide a mixture of charge air and exhaust to an internal combustion engine intake at a sub-ambient temperature. For example, in one mode of operation, cooler  150  is operable to cool charge air to a temperature at or near ambient temperature, cooler  130  is operable to cool exhaust to a temperature at or near the temperature of engine coolant, cooler  155  is operable to cool exhaust to a temperature at or near ambient temperature, expander  168  is operable to cool exhaust to a sub-ambient temperature, and a mixture of the output of expander  168  and cooler  150  can be provided to the intake of engine  110  at a sub-ambient temperature. In additional modes of operation, charge air and exhaust can be cooled to a variety of other pre-intake temperatures while still providing a mixture of charge air and exhaust to the intake of engine  110  at a sub-ambient temperature. 
         [0016]    With reference to  FIG. 2  there is illustrated internal combustion engine system  200 . System  200  includes multiple features described above in connection with  FIG. 1  which are labeled with the same reference numerals as used in  FIG. 1 . As illustrated in  FIG. 2  exhaust flows from EGR cooler  130  to rotary centrifugal compressor  142  of EGR pump  140 . Compressor  142  compresses exhaust and pumps the compressed exhaust to EGR cooler  155 . From EGR cooler  155 , compressed cooled exhaust proceeds to turbine  141  where it is cooled through expansion and provides driving force to turbine  141  and to EGR pump  140 . EGR pump  140  is also driven by an external power source, for example, a drive shaft, a drive belt, an electric motor, a hydraulic drive, a pneumatic drive, a variable speed device drive or a combination thereof. In the illustrated embodiment compressor  142  and turbine  141  are coupled to a common shaft which is also coupled with the external power source. Turbine  141  is preferably a variable geometry turbine which can be adjusted to achieve desired compressor pressure ratio, shaft speed, outlet temperature, engine emissions, and/or fuel economy, but could also be another type of turbine, for example, a variable nozzle turbine, a fixed geometry turbine, an internally wastegated turbine, or an externally wastegated turbine. Turbine  141  can extract work from the expansion of exhaust gas to assist in driving compressor  142  or extracted work can be provided to one of a variety of other elements as described above in connection with expander  168 . From turbine  141  exhaust is provided to intake manifold  111  and then to the cylinders of engine  110 . 
         [0017]    System  200  may be operated to provide a mixture of charge air and exhaust to an internal combustion engine intake at a sub-ambient temperature. For example, in one mode of operation, cooler  150  is operable to cool charge air to a temperature at or near ambient temperature, cooler  130  is operable to cool exhaust to a temperature at or near the temperature of engine coolant, cooler  155  is operable to cool exhaust to a temperature at or near ambient temperature, turbine  141  is operable to cool exhaust to a sub-ambient temperature, and a mixture of the output of turbine  141  and cooler  150  can be provided to the intake of engine  110  at a sub-ambient temperature. In additional modes of operation, charge air and exhaust can be cooled to a variety of other pre-intake temperatures while still providing a mixture of charge air and exhaust to the intake of engine  110  at a sub-ambient temperature. 
         [0018]    With reference to  FIG. 3  there is illustrated an internal combustion engine system  300 . System  300  includes multiple features described above which are labeled with the same reference numerals as used in the foregoing Figs. As illustrated in  FIG. 3  exhaust flows from EGR cooler  130  to compressor  142  of EGR pump  140 . Compressor  142  compresses exhaust and pumps the compressed exhaust into a charge air flowpath upstream of mixed charge cooler  157  which preferably cools a mixture of exhaust and charge air flowing through it by dissipating heat to the surrounding environment, but could also be any of the alternative cooler types described above in connection with coolers  130 ,  150  and  155 . From mixed charge cooler  157 , the mixture of compressed cooled exhaust and charge air proceeds to turbine  141  where it is cooled through expansion and provides driving force to turbine  141 . In alternative embodiments, charge air and recirculated exhaust gas may be cooled by separate coolers and then mixed before being provided to turbine  141 . From turbine  141  exhaust is provided to intake manifold  111  and then to the cylinders of engine  110 . 
         [0019]    In system  300  the mixture of EGR and charge air has a much larger flow rate than either stream alone. Expander  141  thus has a much greater mass flow rate than compressor  142 , and can provide more power than compressor  142  requires. Under many operating conditions, EGR pump  140  can deliver power to the engine or to another receiver of extracted work rather than being a net power consumer. This power can be provided by turbocharger  120  and then extracted by turbine  141 . Rather than deliberately reducing efficiency of turbine  121  to drive exhaust manifold pressure high enough that EGR will flow from exhaust to intake manifold, turbine  121  operates at high efficiency and low pressure ratio, delivering more power to compressor  122  so the compressed charge air entering mixed charge cooler  157  is at similar pressure to that of EGR leaving compressor  142 . Thus, turbine  121  invests extra energy into the fresh air stream, and that energy is harvested by turbine  141 . 
         [0020]    System  300  may be operated to provide a mixture of charge air and exhaust to an internal combustion engine intake at a sub-ambient temperature. For example, in one mode of operation, cooler  130  is operable to cool exhaust to a temperature at or near the temperature of engine coolant, cooler  157  is operable to cool a mixture of exhaust and charge air to a temperature at or near ambient temperature, turbine  141  is operable to cool a mixture of exhaust and charge air to a sub-ambient temperature, and a mixture of exhaust and charge air can be provided to the intake of engine  110  at a sub-ambient temperature. In additional modes of operation, charge air and exhaust can be cooled to a variety of other pre-intake temperatures while still providing a mixture of charge air and exhaust to the intake of engine  110  at a sub-ambient temperature. 
         [0021]    With reference to  FIG. 4  there is illustrated an internal combustion engine system  400 . System  400  includes multiple features described in the foregoing Figs. which are labeled with the same reference numerals used in the foregoing Figs. System  400  includes an expander  410  which is preferably a turbine, most preferably a variable geometry turbine, mounted on a common shaft with turbine  121  and compressor  122  of turbocharger  120 . In other embodiments expander  410  can be differently coupled with turbocharger  120  via one or more mechanical, electrical, hydraulic or other linkages or a combination thereof. In other embodiments expander  410  can be selectably coupled and de-coupled with turbocharger  120 . In other embodiments, expander  410  can be independent of turbocharger  120 . Expander  410  receives charge air which has been compressed by compressor  122  and cooled by charge air cooler  150 . Expander  410  expands the charge air which it receives and outputs to intake manifold  111 . Expander  410  can extract work from the expansion of exhaust gas to assist in driving compressor  122  or extracted work can be provided to one of a variety of other elements as described above in connection with expander  168 . 
         [0022]    System  400  includes EGR cooler  130  which can receive and cool a portion of the exhaust gas output by engine  110 . An EGR valve  133  is preferably positioned downstream from EGR cooler  130 , but could also be positioned in other locations, for example, upstream of EGR cooler  130  or further downstream than the illustrated position. EGR valve  133  is preferably operable to vary the amount of recirculated exhaust gas that passes through EGR cooler  130 , but could also be an on/off valve. From EGR valve  133 , recirculated exhaust gas passes to bypass valve  154  which is preferably operable to selectively vary the amount of recirculated exhaust gas provided to EGR cooler  155  or bypassed around EGR cooler  155 , but could also be a binary valve which routes all recirculated exhaust gas either to EGR cooler  155  or to bypass EGR cooler  155 . Recirculated exhaust gas from EGR cooler  155 , bypassed around EGR cooler  155 , or both can be mixed with charge air from expander  410  and provided to intake manifold  111 . 
         [0023]    In a preferred mode of operation system  400  is operable to provide charge air from compressor  122  which has been compressed to pressure greater than that which would allow recirculation of exhaust gas through a high pressure loop exhaust recirculation path. The work used to compress the air to this pressure is extracted by expander  410 . It should be appreciated that system  400  could also include a two-stage turbocharging system. 
         [0024]    System  400  may be operated to provide a mixture of charge air and exhaust to an internal combustion engine intake at a sub-ambient temperature. For example, in one mode of operation, cooler  130  is operable to cool exhaust to a temperature at or near the temperature of engine coolant, cooler  155  is operable to cool exhaust to a temperature at or near ambient temperature, cooler  150  is operable to cool charge air to a temperature at or near ambient temperature, turbine  410  is operable to cool charge air to a sub-ambient temperature, and a mixture of exhaust and charge air can be provided to the intake of engine  110  at a sub-ambient temperature. In additional modes of operation, charge air and exhaust can be cooled to a variety of other pre-intake temperatures while still providing a mixture of charge air and exhaust to the intake of engine  110  at a sub-ambient temperature. 
         [0025]    With reference to  FIG. 5  there is illustrated an internal combustion engine system  500 . System  500  includes multiple features described in the foregoing Figs. which are labeled with the same reference numerals used in the foregoing Figs. System  500  includes an EGR pump  510  positioned downstream of EGR cooler  130  and which is operable to selectably control the flow of exhaust gas through EGR cooler  130 . EGR pump  510  is preferably a turbo-compressor-type pump. EGR pump  510  could be electrically driven, mechanically driven, hydraulically driven, pneumatically driven or driven by a combination thereof. In one embodiment EGR pump  510  is driven by a high speed electric motor powered by an engine driven alternator. In one embodiment EGR pump  510  is driven by a hydraulic motor. 
         [0026]    From EGR pump  510  recirculated exhaust gas proceeds to valve  520  which is operable to selectably route recirculated exhaust gas to intake manifold  111  or to a location upstream of mixed charge cooler  157 . Mixed charge cooler  157  is operable to cool compressed charge air received from compressor  122  or, when recirculated exhaust is provided upstream of mixed charge cooler, to cool a mixture of compressed charge air and recirculated exhaust gas. 
         [0027]    System  500  may be operated to provide a mixture of charge air and exhaust to an internal combustion engine intake at a sub-ambient temperature. For example, in one mode of operation, cooler  130  is operable to cool exhaust to a temperature at or near the temperature of engine coolant, cooler  157  is operable to cool a mixture of exhaust and charge air to a temperature at or near ambient temperature, turbine  410  is operable to expand a mixture of exhaust and charge air to a sub-ambient temperature, and a mixture of exhaust and charge air can be provided to the intake of engine  110  at a sub-ambient temperature. In additional modes of operation, charge air and exhaust can be cooled to a variety of other pre-intake temperatures while still providing a mixture of charge air and exhaust to the intake of engine  110  at a sub-ambient temperature. 
         [0028]    With reference to  FIG. 6  there is illustrated an internal combustion engine system  600 . System  600  includes many of the features described in the foregoing Figs. which are labeled with the same reference numerals used in the foregoing Figs. System  600  includes a low pressure loop exhaust gas recirculation in which exhaust gas passes from turbine  121  to one or more aftertreatment components  610  from which an EGR valve  615  can selectably pass a portion of the exhaust gas to EGR cooler  130 . From EGR cooler  130  recirculated exhaust gas passes to water separator or condensation separator  620 . From separator  620 , recirculated exhaust gas is mixed with charge air and the mixture is passed to compressor  122 . From compressor  122 , the mixture passes to valve  640 . Valve  640  is operable to selectably route the mixture to mixed charge cooler  157  or to bypass mixed charge cooler  157  and route all or a portion of the mixture to expander  410 . From mixed charge cooler  157  the mixture passes to valve  650  which is selectably operable to route the mixture to expander  410 , or to bypass expander  410  and route the mixture to intake manifold  111 . 
         [0029]    System  600  may be operated to provide a mixture of charge air and exhaust to an internal combustion engine intake at a sub-ambient temperature. For example, in one mode of operation, cooler  130  is operable to cool exhaust to a temperature at or near the temperature of engine coolant, cooler  157  is operable to cool a mixture of exhaust and charge air to a temperature at or near ambient temperature, turbine  410  is operable to a mixture of exhaust and charge air to a sub-ambient temperature, and a mixture of exhaust and charge air can be provided to the intake of engine  110  at a sub-ambient temperature. In additional modes of operation, charge air and exhaust can be cooled to a variety of other pre-intake temperatures while still providing a mixture of charge air and exhaust to the intake of engine  110  at a sub-ambient temperature. 
         [0030]    While exemplary embodiments of the invention have been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected. It should be understood that while the use of words such as preferable, preferably, preferred or more preferred utilized in the description above indicate that the feature so described may be more desirable, it nonetheless may not be necessary and embodiments lacking the same may be contemplated as within the scope of the invention, the scope being defined by the claims that follow. In reading the claims, it is intended that when words such as “a,” “an,” “at least one,” or “at least one portion” are used there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. When the language “at least a portion” and/or “a portion” is used the item can include a portion and/or the entire item unless specifically stated to the contrary.