Power plants – Fluid motor means driven by waste heat or by exhaust energy... – With supercharging means for engine
Reexamination Certificate
1999-11-09
2001-05-29
Koczo, Michael (Department: 3746)
Power plants
Fluid motor means driven by waste heat or by exhaust energy...
With supercharging means for engine
C123S567000
Reexamination Certificate
active
06237336
ABSTRACT:
TECHNICAL FIELD
The present invention relates to internal combustion engines, and, more particularly, to exhaust gas recirculation systems in such engines.
BACKGROUND ART
An exhaust gas recirculation (EGR) system is used for controlling the generation of undesirable pollutant gases and particulate matter in the operation of internal combustion engines. Such systems have proven particularly useful in internal combustion engines used in motor vehicles such as passenger cars, light duty trucks, and other on-road motor equipment. EGR systems primarily recirculate the exhaust gas by-products into the intake air supply of the internal combustion engine. The exhaust gas which is reintroduced to the engine cylinder reduces the concentration of oxygen therein, which in turn lowers the maximum combustion temperature within the cylinder and slows the chemical reaction of the combustion process, decreasing the formation of nitrous oxides (NoX). Furthermore, the exhaust gases typically contain unburned hydrocarbons which are burned on reintroduction into the engine cylinder, which further reduces the emission of exhaust gas by-products which would be emitted as undesirable pollutants from the internal combustion engine.
When utilizing EGR in a turbocharged diesel engine, the exhaust gas to be recirculated is preferably removed upstream of the exhaust gas driven turbine associated with the turbocharger. In many EGR applications, the exhaust gas is diverted directly from the exhaust manifold. Likewise, the recirculated exhaust gas is preferably reintroduced to the intake air stream downstream of the compressor and air-to-air after cooler (ATAAC). Reintroducing the exhaust gas downstream of the compressor and ATAAC is preferred due to the reliability and maintainability concerns that arise if the exhaust gas passes through the compressor and ATAAC. An example of such an EGR system is disclosed in U.S. Pat. No. 5,802,846 (Bailey), which is assigned to the assignee of the present invention.
With conventional EGR systems as described above, the charged and cooled combustion air which is transported from the ATAAC is at a relatively high pressure as a result of the charging from the turbocharger. Since the exhaust gas is also typically inducted into the combustion air flow downstream of the ATAAC, conventional EGR systems are configured to allow the lower pressure exhaust gas to mix with the higher pressure combustion air. Such EGR systems may include a venturi section which induces the flow of exhaust gas into the flow of combustion air passing therethrough. However, the exhaust gas may be drawn from only a subset of the combustion cylinders within the engine. For example, the exhaust gas may be drawn from only a single cylinder and thus is provided in a pulsed manner to the venturi section. Some of the combustion cylinders therefore receive an adequate mixture of combustion air and exhaust gas, while other cylinders receive very little or no exhaust gas in the combustion air mixture.
The present invention is directed to overcoming one or more of the problems as set forth above.
DISCLOSURE OF THE INVENTION
In one aspect of the invention, an internal combustion engine includes at least one cylinder head defining a plurality of combustion cylinders. Each combustion cylinder has a displacement volume. An exhaust manifold is fluidly connected to each cylinder for transporting exhaust gas therefrom. An intake manifold provides combustion air to each cylinder. A turbocharger is driven by exhaust gas from the exhaust manifold and provides charged combustion air to the intake manifold. A mixing vessel has at least two inlets, at least one outlet and a mixing chamber. One of the inlets is fluidly connected with the exhaust manifold and an other of the inlets is fluidly connected with the turbocharger. The one inlet and the other inlet are connected with the mixing vessel in a parallel manner. The mixing chamber has a volume which is dependent upon a plurality of the displacement volumes.
In another aspect of the invention, a method of recirculating exhaust gas in an internal combustion engine includes the steps of: providing at least one cylinder head defining a plurality of combustion cylinders, each combustion cylinder having a displacement volume; providing an exhaust manifold and an intake manifold, each fluidly connected to each cylinder; providing a mixing vessel having at least two inlets, at least one outlet and a mixing chamber, one of the inlets fluidly connected with the exhaust manifold and an other of the inlets fluidly connected with a turbocharger, the one inlet and the other inlet connected with the mixing vessel in a parallel manner; transporting exhaust gas from the exhaust manifold to the one inlet; transporting combustion air from the turbocharger to the other inlet; mixing the exhaust gas and the combustion air within the mixing chamber in a volume which is dependent upon a plurality of the displacement volumes; and transporting the mixed exhaust gas and combustion air to the intake manifold.
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Feucht Dennis D.
Lawrence Keith E.
Caterpillar Inc.
Koczo Michael
Taylor Todd T.
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