Patent Application
20100071365
The present invention relates to an exhaust gas recirculation system for an internal combustion engine, and more particularly, to an exhaust gas recirculation system having a particulate filter located between a first turbocharger and a second turbocharger.
The use of exhaust gas recirculation (EGR) systems in internal combustion engines is known. An EGR system is typically used to reduce nitrogen oxide emissions by recirculating a portion of an engine's exhaust gas back through the engine cylinders. Mixing of the exhaust gas with incoming air dilutes the mix with inert gas and thereby lowers the adiabatic flame temperature. Lowering the adiabatic flame temperature can reduce the amount of excess nitrogen oxides. Stated differently, the mixing or incoming air with inert gas cools combustion chamber temperatures to levels that result in the reduction of formation of nitrogen oxides.
The use of turbochargers with internal combustion engines is also known. A turbocharger is essentially an air compressor that is used to force additional air into the internal combustion engine. The air compressor is powered by a turbine that is driven by the engine's own exhaust gases. The turbine inlet receives the exhaust gases from the engine causing a turbine wheel to rotate, this rotation also driving the compressor which compresses ambient air and delivers it to the intake manifold of the engine at higher pressure. The compressed air provides for a greater amount of air entering into cylinders of the engine and can result in reduced fuel consumption and emissions.
In diesel engines, a diesel particulate filter (DPF) can work in combination with the EGR system and an oxidation catalyst to remove a majority of the nitrogen oxides, particulate matter and unburned hydrocarbons from burned diesel fuel. The DPF can have a porous honeycomb structure or a structure of a plurality of thin metal sheets, both structures affording for the catching or entrapping of soot as it passes through the exhaust gas system. The use of a DPF in combination with a downstream turbocharger can improve fuel economy, however a decrease in performance typically results. As such, an exhaust gas recirculation system that combines the use of a DPF with a turbocharger and still provide improved performance would be desirable.
An exhaust gas recirculation system for an internal combustion engine is disclosed. The exhaust gas recirculation system can include a first turbocharger and a second turbocharger with a particulate filter located between the two turbochargers. The first turbocharger can have a first exhaust turbine and a first charger while the second turbocharger can have a second exhaust turbine and a second charger. The particulate filter can be located between the first exhaust turbine and the second exhaust turbine and thereby remove particulates from an exhaust gas before it reaches the second exhaust turbine. In some instances, an exhaust gas recirculation line can be included and have an inlet that is located downstream from the particulate filter. In addition, the exhaust gas recirculation line can have an outlet that is located between the first charger and the second charger, or in the alternative downstream from the first charger. It is appreciated that the internal combustion engine can be a diesel engine and the particulate filter can be a diesel particulate filter.
The present invention discloses an exhaust gas recirculation (EGR) system for an internal combustion engine. As such, the EGR system has utility as a component for an internal combustion engine.
The EGR system can include a first turbocharger having a first exhaust turbine and a first compressor and a second turbocharger having a second exhaust turbine and a second compressor. The first exhaust turbine can be located downstream from an exhaust outlet, also known as an exhaust manifold, of the engine and the second exhaust turbine located between the exhaust manifold and the first exhaust turbine. A particulate filter can be located between the first exhaust turbine and the second exhaust turbine. The first and second exhaust turbines are driven by the exhaust gas from the engine, and provide power to a first compressor that is located upstream from an air intake manifold of the engine and a second compressor that is located between the air intake manifold and the first compressor, respectively. An EGR line can also be included, the EGR line having an inlet located between the first exhaust turbine and the second exhaust turbine and optionally downstream from the particulate filter. The EGR line can also have an outlet that is located between the first compressor and the second compressor, and/or downstream from the second compressor. In some instances, the internal combustion engine is a diesel engine and the particulate filter is a diesel particulate filter (DPF).
It is appreciated that the internal combustion engine has an air inlet line and an exhaust gas line. For the purposes of the present invention, the terms air inlet line and exhaust gas line refer to the tubing, piping, passageways and the like through which air is supplied to and exhaust is removed from the engine, respectively. It is further appreciated that one skilled in the art can discuss an EGR system for an internal combustion engine with the air inlet line and exhaust gas line assumed to be present and thus may or may not be mentioned.
A diesel engine can have a first turbocharger with a first exhaust turbine that is in fluid communication with an exhaust gas line and a first compressor that is in fluid communication with an air inlet line. In addition, a second turbocharger can be included with a second exhaust turbine in fluid communication with the exhaust gas line and a second compressor in fluid communication with the air inlet line. A DPF can be in fluid communication with the exhaust gas line and be located between the first exhaust turbine and the second exhaust turbine. Downstream from the DPF and upstream from the first exhaust gas turbine an EGR line inlet can be located which affords for exhaust gas that has passed through the DPF to be recirculated into the diesel engine. The EGR line has an outlet, the outlet being in fluid communication with the air inlet line and located upstream of the second compressor and/or downstream of the second compressor.
A process for recirculating exhaust gas in an internal combustion engine is also disclosed, the process including providing the EGR system as described above and operating the engine such that air flows in through the air inlet line and exhaust gas flows out through the exhaust gas line. The exhaust gas flows through the second exhaust gas turbine, then through the particulate filter, with part of the exhaust gas diverted through the EGR line into the air inlet line. It is appreciated that flowing of the exhaust gas through the second exhaust turbine drives the second compressor. Flowing the exhaust gas through the particulate filter removes particulates from the gas and thereby produces a “clean” exhaust gas and flowing the clean exhaust gas back through the engine provides for reduced nitrogen oxide emissions, improved fuel economy and/or improved performance.
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The second turbocharger 240 can include a second exhaust turbine 242 that is in fluid communication with exhaust gas line 220 and a second compressor 244 that is in fluid communication with the air inlet line 210. In addition, a connection means 246, illustratively including a shaft, can connect the second exhaust turbine 242 to the second compressor 244. It is appreciated that the second exhaust turbine 242 is located downstream from the engine 200 and upstream from the first exhaust turbine 232. Likewise, the first compressor 244 is located upstream from the engine 200 and downstream from the first compressor 234.
Located between the first exhaust turbine 232 and the second exhaust turbine 242 is a particulate filter 250 that is in fluid communication with the exhaust gas line 220. In some instances, the particulate filter 250 is downstream from the second exhaust turbine 242 and upstream from the first exhaust turbine 232. In addition, the engine 200 can be a diesel engine and the particulate filter 250 can be a diesel particulate filter.
An EGR line 260 can be included as part of the EGR system 20, the EGR line 220 having an inlet 262 that is in fluid communication with the exhaust gas line 220 and an outlet 264 that is in fluid communication with the air inlet line 210. In this manner, exhaust gas flowing through the exhaust gas line 220 can be diverted to the air inlet line 210. In some instances, a valve 266 can be included within the EGR line 260 such that the amount of exhaust gas diverted from the exhaust gas line 220 to the air inlet line 210 can be controlled. As shown in
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It is appreciated that the engine 200, the first turbocharger 230, the second turbocharger 240, the particulate filter 250 and the EGR line 260, 270 can have additional components that are not shown in the figures but known to those skilled in the art. Those skilled in the art will thus understand that such components can be included and not fall outside the scope of the present invention. In addition, it is known to those skilled in the art that a range of materials, illustratively including metals, alloys, ceramics, and plastics can be used to construct the EGR system and still fall within the scope of the present invention. The invention is not restricted to the illustrative embodiments and examples described above. The embodiments and the examples are not intended as limitations on the scope of the invention. Methods, apparatus, compositions and the like described herein are exemplary and not intended as limitations on the scope of the invention. Changes therein and other uses will occur to those skilled in the art. The scope of the invention is defined by the scope of the claims.
