Exhaust gas recirculation system for a compression ignition engine and a method of controlling exhaust gas recirculation in a compression ignition engine
First Claim
1. An exhaust gas recirculation system for a compression ignition engine, comprising:
- a first pressure sensor for sensing an absolute gas pressure in an intake manifold of the engine;
a second pressure sensor for sensing an absolute gas pressure in an exhaust manifold of the engine;
an engine speed sensor for detecting a rotational speed of the engine crank shaft;
a fuelling rate sensor for detecting a fuelling rate for the engine;
an air charge temperature sensor for detecting a temperature of intake air in the intake manifold of the engine;
a conduit for providing a fluid passage between the exhaust manifold and the intake manifold, and an exhaust gas recirculation valve disposed in the conduit to regulate a flow of exhaust gas from the exhaust manifold to the intake manifold;
means for controlling the exhaust gas recirculation valve so that the flow of the exhaust gas through the conduit from the exhaust manifold to the intake manifold is regulated; and
an electronic controller for receiving signals from the first and second pressure sensors, the engine speed sensor, the fuelling rate sensor and the air charge temperature sensor, computing an optimal ratio of the exhaust gas to be recirculated to intake air based on the signals received and computing a valve position that permits the optimal ratio of exhaust gas to intake air to flow through the conduit to the intake manifold, and actuating the means for controlling the exhaust gas recirculation valve to position the valve at the computed valve position to permit the optimal ratio of exhaust gas to intake air to flow through the conduit from the exhaust manifold to the intake manifold.
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Abstract
An exhaust gas recirculation system for a compression ignition engine and a method of controlling exhaust gas recirculation in compression ignition engines are disclosed. The method and apparatus are adapted to the control of exhaust gas recirculation in diesel and/or multifuel (e.g. diesel and natural gas) engines. The apparatus includes a first pressure sensor for sensing an absolute gas pressure in the intake manifold of the engine, a second pressure sensor for sensing an absolute gas pressure in the exhaust manifold of the engine, an engine speed sensor for detecting engine RPM, a fuelling rate sensor for detecting the commanded fuelling rate for the engine, a temperature sensor for detecting the temperature of intake air in the intake manifold, a conduit for directing exhaust gas from the exhaust manifold to the intake manifold, an electronically actuated mechanical valve in the conduit for controlling the flow of exhaust gas and an electronic controller for analyzing signals from the sensors and outputting control signals to an electric stepper motor which controls the position of the valve. The advantages include accurate control of exhaust gas recirculation in real time, rapid response to changing combustion conditions which result in reduced pollution emission and higher fuel efficiency. A further advantage is a system which is readily retrofit to an existing compression ignition engine or included as a part of original equipment in new engines without engine redesign.
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Citations
23 Claims
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1. An exhaust gas recirculation system for a compression ignition engine, comprising:
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a first pressure sensor for sensing an absolute gas pressure in an intake manifold of the engine; a second pressure sensor for sensing an absolute gas pressure in an exhaust manifold of the engine; an engine speed sensor for detecting a rotational speed of the engine crank shaft; a fuelling rate sensor for detecting a fuelling rate for the engine; an air charge temperature sensor for detecting a temperature of intake air in the intake manifold of the engine; a conduit for providing a fluid passage between the exhaust manifold and the intake manifold, and an exhaust gas recirculation valve disposed in the conduit to regulate a flow of exhaust gas from the exhaust manifold to the intake manifold; means for controlling the exhaust gas recirculation valve so that the flow of the exhaust gas through the conduit from the exhaust manifold to the intake manifold is regulated; and an electronic controller for receiving signals from the first and second pressure sensors, the engine speed sensor, the fuelling rate sensor and the air charge temperature sensor, computing an optimal ratio of the exhaust gas to be recirculated to intake air based on the signals received and computing a valve position that permits the optimal ratio of exhaust gas to intake air to flow through the conduit to the intake manifold, and actuating the means for controlling the exhaust gas recirculation valve to position the valve at the computed valve position to permit the optimal ratio of exhaust gas to intake air to flow through the conduit from the exhaust manifold to the intake manifold. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of controlling exhaust gas recirculation in a compression ignition engine, comprising:
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a) sensing a fuelling rate for the engine; b) sensing a rotational speed of the engine; c) sensing an exhaust manifold absolute pressure and an intake manifold absolute pressure of the engine and computing a pressure drop between the exhaust manifold and the intake manifold; d) determining a volumetric efficiency of gas flow through the engine as a function of the rotational speed and the pressure drop; e) determining a % EGR as a function of the rotational speed and the fuelling rate for the engine; f) determining a temperature of gases in the exhaust manifold as a function of the rotational speed and the fuelling rate for the engine; g) sensing an intake air temperature of air drawn into the intake manifold; h) computing a fluid density of the exhaust gas based on an absolute pressure in the exhaust manifold, a molar mass of the exhaust gas and the temperature of the exhaust gas; h) computing a volumetric flow of exhaust gas through the EGR valve; i) deriving a variable based on the volumetric flow, the fluid density of the exhaust gas and the pressure drop to locate a required EGR valve position; and j) moving the EGR valve to the required position. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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Specification