Power plants – Fluid motor means driven by waste heat or by exhaust energy... – With supercharging means for engine
Reexamination Certificate
1999-03-22
2001-02-13
Denion, Thomas (Department: 3748)
Power plants
Fluid motor means driven by waste heat or by exhaust energy...
With supercharging means for engine
C060S278000, C123S0650BA
Reexamination Certificate
active
06185939
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to an engine and more particularly to a reduction of exhaust emissions.
BACKGROUND ART
The use of fossil fuel as the combustible fuel in engines results in the combustion products of carbon monoxide, carbon dioxide, water vapor, smoke and particulate, unburned hydrocarbons, nitrogen oxides and sulfur oxides. Of these above products carbon dioxide and water vapor are considered normal and unobjectionable. In most applications, governmental imposed regulations are restricting the amount of pollutants being emitted in the exhaust gases.
In the past, NOx emissions have been reduced by reducing the intake manifold temperature, controlling the injection timing (normally retarding), and modifying the injection rate shape. And, the adverse effects on fuel consumption, particulate emissions engine performance have largely been alleviated through improvements in the basic engine design and fuel selection. For example, at the present time smoke and particulates have normally been controlled by design modifications in the combustion chamber and injection pressure. Particulates are also controlled by traps and filters, and sulfur oxides are normally controlled by the selection of fuels being low in total sulfur. This leaves carbon monoxide, unburned hydrocarbons and nitrogen oxides as the emission constituents of primary concern in the exhaust gas being emitted from the engine.
Many systems have been developed for recycling a portion of the exhaust gas through the engine thereby reducing the emission of these constituents into the atmosphere. The recirculation of a portion of exhaust gas is used to reduce NOx pollution emitted to the atmosphere. In a naturally aspirated engine this process is relative simple. But, with a turbocharged engine, the recirculation of a portion of the exhaust gas into the intake air becomes more complex because the intake pressure may be higher than the exhaust pressure during many operating conditions. In many of such past system a volume of the exhaust gas from the engine was redirected to the intake air of the engine through the turbocharger and/or an aftercooler and to the engine. Such systems caused the premature plugging of aftercooler cores and malfunctioning of the systems. Additionally, with such recirculation system deterioration of the exhaust flow was caused by deposit buildup. Various approaches have been used to address the adverse pressure gradient issue. For example, throttling valves have been installed in the air inlet, back pressure valves in the exhaust gas, intake manifold venturi tubes, etc. to provide sufficient pressure drop to get the exhaust gas to flow to the intake air. Although this provides the necessary pressure drop to functionally operate an exhaust gas recirculation system several disadvantages, such as, fuel consumption, emissions, and/or performance occur.
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 exhaust gas recirculation system is used with an engine. The engine defines a plurality of operating parameters and has a rotatable crankshaft through which an engine speed can be defined. And, a plurality of cylinders are defined as a part of the engine. The exhaust gas recirculation system is comprised of a flow of intake air entering a respective one of the plurality of cylinders. The intake air is pressurized to a preestablished pressure. A supply of combustible fuel enters the respective one of the plurality of cylinders. A combustion process within the respective one of said plurality of cylinders defines a flow of exhaust gas having a preestablished pressure being less that said preestablished pressure of the intake air during at least a portion of the engine operating parameters. A portion of the exhaust gas is circulated to the intake air defining a flow of recirculated exhaust gas. The flow of recirculated exhaust gas is cooled prior to being pressurized to a preestablished level and the pressurization of the flow of recirculated exhaust gas being at least as great as the preestablished pressure of the intake air. And, the flow of recirculated exhaust gas is controlled to vary a quantity of recirculated exhaust gas depending on the operating parameter of the engine.
In another aspect of the invention an exhaust gas recirculation system is used with an engine. The engine has a cylinder and a rotatable crankshaft. The engine has a turbocharger defining a compressor section compressing a flow of intake air to a first preestablished pressure and is driven by a flow of exhaust gas having a first preestablished pressure. The exhaust gas recirculation system is comprised of a portion of the flow of exhaust gas being recirculated back to the cylinder and forming a flow of recirculated exhaust gas. The flow of recirculated exhaust gas is cooled. The flow of recirculated exhaust gas being compressed to a second preestablished pressure. The second preestablished pressure of the flow of exhaust gas being at least as great as the first preestablished pressure of the intake air during a portion of an operating parameter of the engine. And, a portion of the flow of intake air being mixed with the flow of recirculated exhaust gas prior to the flow of recirculated exhaust gas being compressed to the second preestablished pressure.
In another aspect of the invention a method of reducing exhaust emissions from an engine having a flow of intake air being at a preestablished pressure and a flow of exhaust gas being at a preestablished pressure being less than the preestablished pressure of the intake air. The method of reducing exhaust emission is comprised of the steps of extracting a portion of the flow of exhaust gas forming a flow of recirculation exhaust gas. Cooling the flow of recirculation exhaust gas. Increasing the pressure of the flow of recirculation exhaust gas to a quantity being at least equivalent to the pressure of the flow of intake air. And, blending the flow of recirculation exhaust gas and a portion of the flow of intake air prior to the pressure of the flow of recirculation gas being increased to a quantity being at least equivalent to the pressure of the flow of intake air.
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Coleman Gerald N.
Evancik Michael J.
Feucht Dennis D.
Lawrence Keith E.
Ma Jiubo
Caterpillar Inc.
Denion Thomas
Gain Larry G.
Trieu Thai-Ba
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