Patent Application
20070175457
This invention relates to internal combustion engines, including but not limited to engines having exhaust gas recirculation passages.
Exhaust gas recirculation (EGR) for internal combustion engines is known. Some engines may also cool the recirculated exhaust gas in EGR coolers. In an engine having a turbocharger, a difference in pressure between the exhaust system and intake system of the engine may determine the maximum amount of exhaust gas that may be recirculated from the exhaust into the intake of the engine.
The pressure of exhaust gas in the exhaust system during operation of the engine is referred to as exhaust back pressure (EBP). Similarly, the pressure of air or a mixture of air and exhaust gas in the intake manifold of the engine is referred to as intake manifold pressure or manifold absolute pressure (MAP) during operation of the engine. An EGR valve is usually employed to fluidly connect the exhaust and intake manifolds. When the EGR valve is opened, exhaust gas flows from the exhaust system into the intake system of the engine. Primary factors that determine the capacity of the EGR system on an engine to flow exhaust gas are the size of the EGR valve opening, and a difference of pressure between EBP and MAP, typically referred to as Delta P.
For emissions control reasons, some engines may require more EGR gas for mixing with the intake air than the engine is able to provide during operation, partly because many engines are advantageously designed to run under low Delta P conditions that are conducive to high fuel economy. Nevertheless, even under conditions of low Delta P, the demand for EGR gas flow increases as emissions requirements for the engine become more stringent.
There have been many methods to augment EGR gas flow on an engine having low Delta P during operation. One method uses an intake throttle valve, configured to constrict air flow into the intake manifold of an engine that is placed at a location upstream of the point of mixing of exhaust gas and air in the intake system. By closing the intake throttle valve, the MAP is lowered and Delta P increases. One disadvantage of this method is that pumping losses in the engine increase, thus lowering fuel economy and the power output of the engine.
Accordingly, there is a need for augmentation of EGR gas flow in an engine having a turbocharger that does not depend on the use of an intake throttle valve or other methods.
An apparatus includes a gas passage having a gas inlet, an engine gas outlet, and at least one exhaust gas recirculation (EGR) gas outlet, wherein the at least one EGR gas outlet is disposed between the gas inlet and the engine gas outlet. The gas passage is arranged to receive exhaust gas through the inlet and expel gas through both the gas outlets. A flow orifice is operatively associated with the gas passage and is disposed between the engine gas outlet and the at least one EGR gas outlet.
An internal combustion engine includes an intake system in fluid communication with a plurality of cylinders and an exhaust system in fluid communication with the plurality of cylinders. A turbocharger includes a turbine in fluid communication with the exhaust manifold and a compressor in fluid communication with the intake manifold. An exhaust gas recirculation (EGR) passage fluidly connects the exhaust system with the intake system, and contains an EGR valve. A gas passage fluidly connects the exhaust system with the turbine and the EGR passage. An orifice is located in the gas passage, between the EGR passage and the turbine.
A method for augmenting flow out of a gas passage includes the step of collecting exhaust gas in a volume of an internal combustion engine. Exhaust gas flows out of the volume to form an exhaust gas flow into a junction. A first portion of the exhaust gas flow exiting the junction is constricted with an orifice. The first portion of the exhaust gas flow is routed to a turbine and a second portion of the exhaust flow exiting the junction is routed to an exhaust gas recirculation (EGR) cooler.
The following describes an apparatus for and method of augmenting flow of exhaust gas from an exhaust system of a turbocharged diesel engine into an EGR cooler without creating additional restriction in an intake system of the engine. The diesel engine may have an intake throttle device, and may additionally have one or more turbochargers. A typical diesel engine 100 is shown in
The engine 100 has a crankcase 101 that includes a plurality of cylinders in the crankcase 101 that are fluidly connected to an intake system 103 and to an exhaust system 105. A turbocharger 107 includes a turbine 109 having a turbine inlet 113 connected to the exhaust system 105 and driving a compressor 111 connected to the intake system 103. An air cleaner 115 is connected to an inlet of the compressor 111. An outlet 117 of the compressor 111 is connected to an inlet 119 of a charge air cooler 121 through a hot air passage 123. An outlet 125 of the charge air cooler 121 is connected to an intake throttle 127 through a cold air passage 129.
An EGR cooler 131 is connected to the exhaust system 105 through an EGR passage 133 at a Y-junction 134. Downstream of the EGR cooler 131 is an EGR valve 135. The EGR valve 135 may alternatively be connected upstream of the EGR cooler 131 in the EGR passage 133, but still downstream of the junction 134. On an outlet side of the EGR valve 135 is a mixing junction 137 having a first inlet 138 connected to the intake throttle 127 and a second inlet 140 connected to the EGR valve 135. An outlet 142 of the mixing junction 137 is connected to the intake system 103. During normal engine operation, cooled intake air enters the mixing junction 137 through the first inlet 138 and mixes with exhaust gas entering the junction 137 from the second inlet 140. A mixture of exhaust gas and air exits the junction 137 from the outlet 142 and enters the intake system 103.
When the engine 100 operates at or near an idle condition, i.e., when engine speed is low and there is little to no torque load on the engine, the intake throttle may be completely closed 127 while the EGR valve 135 may be open to induce a flow of exhaust gas from the junction 134 to enter the EGR passage 133, pass through the EGR cooler 131, the EGR valve 135, and enter the junction 137. The mixture of air and exhaust gas exiting the junction 137 must be adequate to maintain a stable idle engine speed of the engine 100.
When the engine 100 operates above an idle condition, the intake throttle 127 may be substantially, or more than 5%, open. Cooled intake air exiting the charge air cooler 121 enters the junction 137 and mixes with exhaust gas coming from the EGR valve 135. The mixture of air and exhaust gas exits the junction 137 and enters the intake system 103 of the engine 100. A desired flow of exhaust gas from the EGR valve 135 may be augmented by, for example, constricting fresh air flow into the engine 100 by closing the intake throttle 127 to an adequate extent. This solution to inducing exhaust gas flow through the engine 100 creates losses in engine efficiency. For example, an increase in intake restriction of the engine causes a loss of power and increased fuel consumption. In a first embodiment of the invention, a flow orifice 136 is added downstream of the junction 134 in the exhaust system 105. The flow orifice 136 causes a high pressure region of exhaust gas to be created adjacent to and upstream of the orifice 136. This high pressure region forces exhaust gas to enter the passage 133.
In the prior art, many different arrangements have been used to augment flow of exhaust gas in an EGR system of an engine. An example of a typical exhaust system pipe 200 is shown in
Use of an exhaust system pipe 200 alone does not enable adequate inducement of exhaust gas to pass from the main pipe 218 into the EGR outlet 204. A known feature to aid exhaust gas flow through an EGR outlet 304 of an exhaust system pipe 300 is shown in
Computational simulations of exhaust flow through an exhaust system pipe have indicated that an improvement in the complexity of the design for the exhaust system pipe may be made without compromising performance. One embodiment of an improved exhaust system pipe 400 is shown in
The orifice plate 422 may be made of steel sheet metal, and may advantageously be welded into the tube 418 before the flange 420 is installed thereon. The orifice plate 422 has an opening 424 to allow exhaust gas to pass through and exit through the exhaust outlet 406. The opening 424 may be circular, or it may be another appropriate shape for the size and type of the tube 418, for example, the opening 424 may be elliptical if installed in an area of the tube 418 that is also elliptical. A size for the opening 424 may be determined based on computational calculations, depending on the requirements of the engine as well as the sizes of the openings in the EGR outlet 404, the exhaust opening 406, and the inlet opening 402. The size of the opening 424 may advantageously provide a flow area that is about 40% less than the flow area provided by the tube 418 prior to the orifice plate 422, but other reductions in area may be used.
An alternative embodiment of an exhaust system pipe 500 is shown in
The outlet flange 522 has an opening 524 to allow exhaust gas to pass through and exit the exhaust outlet 506. The opening 524 is smaller than the size of the tube 418 and may be circular, or another appropriate shape for the size and type of the tube 518. For example, the opening 524 may be elliptical if installed in an area of the tube 518 that is also elliptical. Similar to the exhaust system 400, the size of the opening 524 may advantageously provide a flow area that is about 40% less than a flow area provided by the tube 518, but other sizes may be used.
Another alternative embodiment of an exhaust system pipe 600 that has an inlet 602, an EGR outlet 604, an exhaust outlet 606, and a bellows section 608 disposed between an inlet flange 610 and a Y-section 612 is shown in
The tube 618 has a constrictor section 624 at a location between the Y-section 612 and the exhaust outlet 606. A smallest internal diameter of the constrictor section 624 is smaller than an internal diameter of the tube 618. The constrictor section 624 may be formed by a radially inward loading applied to a section of the tube 618 causing plastic deformation of the section to the tube 618. The constrictor 624 may have an orifice section 626 positioned between two blending sections 628. The blending sections 628 may be the result of a pressing operation to form the constrictor 624, and may also help relieve stresses during thermal gradients of the Y-pipe 600 during operation. The constrictor orifice section 626 may advantageously provide a flow area that is about 40% less than a flow area provided by the tube 618, but other reductions in flow area may be used.
Use of an orifice can advantageously augment flow for more than one outlets of a fluid junction. A fluid junction 700 is shown in
The junction 700 may be advantageous for the operation of an engine having more than one EGR cooler connected to an exhaust system, each cooler receiving exhaust gas from one of the secondary outlets 706 and 708. A fluid flow exiting the primary outlet 704 may be exhaust gas routed to a turbocharger turbine. Fluid flowing out of the secondary outlet 706 may be exhaust gas routed to a first EGR cooler (not shown), while fluid flowing out of the secondary outlet 708 may be exhaust gas routed to a second EGR cooler (not shown). The junction 700 may be integrated with exhaust pipes in the engine's exhaust system, and may be fabricated from steel sheet or any other appropriate material or process known in the art of engine exhaust systems.
A method for augmenting flow of exhaust gas through an outlet of an exhaust system pipe in an internal combustion engine is shown in
The method may be repeated during operation of the engine. In a case where one EGR cooler is used, the fluid junction may be a Y-pipe. If two EGR coolers are used, the fluid junction may be replaced by a cross-junction. The fluid junction may be arranged in any configuration that enables supply of exhaust gas to as many EGR coolers as necessary. In any case, the orifice may be placed on a leg of the junction that is connected to an inlet of a turbine to augment exhaust gas flow going to the EGR coolers that may be connected to other legs of the junction.
The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.
