|Publication number||USRE39937 E1|
|Application number||US 10/180,458|
|Publication date||Dec 11, 2007|
|Filing date||Jun 27, 2002|
|Priority date||Sep 30, 1998|
|Also published as||DE19946725A1, US6079395|
|Publication number||10180458, 180458, US RE39937 E1, US RE39937E1, US-E1-RE39937, USRE39937 E1, USRE39937E1|
|Inventors||Gerald N. Coleman|
|Original Assignee||Caterpillar, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (25), Referenced by (3), Classifications (12), Legal Events (2)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This invention relates generally to as engines and more particularly to a reduction of exhaust emissions.
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, the majority of the products of combustion have been controlled through design modifications and fuel selection. For example, at the present time smoke has normally been controlled by design modifications in the combustion chamber, particulates are normally 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 emissions 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 components into the atmosphere. The recirculation of a portion of exhaust gas is used to reduce pollution emitted to the atmosphere. 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 to the engine. It is anticipated that future exhaust emission standards will require the use of cooled exhaust gas recirculation to meet the emission standards. One method of cooling the exhaust gas is to use an engine jacket water cooler. The problem with this approach is that the temperature of the engine jacket water is increased and the heat must be rejected to the atmosphere via a heat exchanger or radiator. The tendency of vehicle manufactures is to reduce the frontal area of their vehicles to improve visibility and aerodynamics. Thus, with this tendency the available heat rejection area of the heat exchanger is being reduced and any increase in heat exchanger size requiring a larger frontal area is not well accepted. And, if the additional heat added to the engine cooling system by the exhaust gas cooling is not rejected, the extra heat will cause engine overheating under some operating parameters.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the invention an exhaust gas recirculation system is adapted for use with an engine. The engine has a cooling system defining a heat exchanger having a coolant flowing therethrough. The engine and the cooling system having a preestablished size and cooling rejection rate. The exhaust gas recirculation system is comprised at least a cylinder positioned within the engine. A piston positioned within the cylinder and defining a compression stroke. A flow of intake air enter the cylinder. A supply of combustible fuel enter the cylinder. A combustion process within the cylinder defines a flow of exhaust gas exiting therefrom. An exhaust valve regulator is interposed the flow of intake air and the flow of exhaust gas. The exhaust valve regulator is movable between an open position and a closed position. An exhaust gas cooler is positioned in the flow of exhaust gas being directed to the flow of intake air. The exhaust gas cooler has the coolant in the engine cooling the exhaust gas. And, a control system has a plurality of sensors being in communication with the engine. The sensors communicate a signal to a controller. The controller has a plurality of paths or maps defined therein and the controller interprets the signal and defines an operating parameter of the engine and controls the open position and the closed position of the exhaust valve regulator.
In another aspect of the invention, a method of reducing exhaust emissions from an engine defining a cylinder and having a piston positioned in the cylinder is comprised of the following steps. Passing a flow of exhaust gas through an exhaust gas cooler. Cooling the engine and the exhaust gas cooler with a coolant. The coolant being a common coolant. Circulating the coolant through a heat exchanger and cooling said engine. Passing the flow of exhaust gas after passing through the exhaust gas cooler to a flow of intake air. Passing the flow of intake air and the flow of exhaust gas after passing through the exhaust gas cooler to a cylinder. Supplying a quantity of combustible fuel to the cylinder in a preestablished relationship to a compression stroke of the piston. Monitoring an operating parameter of the engine and controlling the quantity of flow of exhaust gas to the flow of intake air depending on the operating parameter. And, combusting the flow of intake air and the flow of exhaust gas within the cylinder.
As best shown in
The exhaust system 80, in this application, includes an exhaust manifold 84 defining an exhaust passage 86 therein being in communication with the exhaust passage 60 within the head 58. A turbocharger 88 is attached to the exhaust manifold 84 in a conventional manner and has a turbine section 90 operative connected to and being driven by the flow of exhaust gas 62 from a combustion process within the plurality of cylinders 54. The turbocharger 88 further includes a compressor section 92 being driven by the turbine section 90 in a conventional manner. The flow of exhaust gas 62 exits an exhaust opening, not shown, in the turbine section 90 and passes to the atmosphere.
The intake system 82 includes an intake manifold 96 defining an intake passage 98 therein being in communication with the intake passage 64 within the bead 58. The compressor section 92 of the turbocharger 88 is operatively connected to the intake passage 98 in a conventional manner. The flow of intake air 66 is communicated from the atmosphere through a filter, not shown, to the compressor section 92 of the turbocharger 88 in a convention manner. The intake air 66 is communicated from the compressor section 92 through an aftercooler 100 which, in this application, is an air to air aftercooler located in the frontal area 18 and to the intake passage 98 within the intake manifold 96 in a conventional manner. And, in communicated into the intake passage 64 within the head 58 and to the plurality of cylinders 54.
An exhaust gas recirculation system 110 is operatively communicated between the flow of exhaust gas 62 and the flow of intake air 66. For example, in this application, a tube 112 having a passage 114 therein extends from the exhaust manifold 84 to the flow of intake air 66. An exhaust valve regulator 116 is positioned in the tube 112 and is interposed the exhaust manifold 84 and the flow of intake air 66. An exhaust gas cooler 118 is positioned in the tube 112 and is interposed the exhaust valve regulator 116 and the flow of intake air 66. The exhaust valve regulator 116 has an open position 120, shown in phantom, and a closed position 122. The exhaust valve regulator 116 is operatively movable through a infinite number of positions between the open position 120 and the closed position 122. With the exhaust valve regulator 116 at the open position 120, maximum exhaust gas 62 is recirculated to the plurality of cylinders 54. And, with the exhaust valve regulator 116 at the closed position 122 zero exhaust gas 62 is recirculated to the plurality of cylinders 54. At the positions therebetween, the amount of exhaust gas 62 recirculation is varied between maximum and zero recirculation. The exhaust gas cooler 118 has a coolant inlet line 124 communicating with the coolant 36 in the engine 30. And, a coolant outlet line 126 communicates with the coolant 36 in the engine 30. Each of the coolant inlet line 124 and the coolant outlet line 126 are connected to the engine block 52 and the exhaust gas cooler 118 in a conventional manner.
A control system 130 communicates between the engine 30 and the exhaust gas recirculation system 110. A plurality of paths or maps 132, depending on operating parameters of the engine 30 are used to control emissions and the resulting operating parameters of the engine 30. For example, the control system 130 includes a plurality of sensors 134 being positioned about the engine 30. The plurality of sensors 134 monitor engine 30 operating parameters. Such parameters include engine speed, coolant temperature, intake manifold pressure, exhaust manifold pressure and fuel quantity. Other parameters could include oil temperature, intake manifold temperature, ambient temperature and/or pressure. A plurality of communication means 136 such as wires or electronic devices are interposed the plurality of sensors 134 and a controller 138, such as a computer. The controller 138, as used with this application, is located onboard the vehicle 10 or engine 30. As an alternative, the controller 138 could be remotely positioned from the vehicle 10 or engine 30. The plurality of paths or maps 132 are stored within the controller 138. The plurality of paths or maps 132 are adjustable and can be changed or varied.
A conventional fuel injection system 140 is used with the engine 30. The fuel injection system 140 include a plurality of injectors 142, only one being shown, operative connected to respective ones of the plurality of cylinder 54. Each of the plurality of injectors 142 provides a flow of combustible fuel, not shown, to each of the plurality of cylinders 54. The quantity of fuel injected to each of the plurality of cylinders 54 is controllably injected between a low fuel quantity position and a high fuel quantity position, not shown. Thus, the quantity of fuel is variably controlled to each of the plurality of cylinders 54. Each of the plurality of fuel injectors 142, in this application, is electronically controlled by the controller 138. Other methods of controlling the plurality of fuel injectors could be used, for example, a mechanical system, a hydraulic system or a pneumatic system. Additionally, the controller 138, in this application, determines the relative timing (advance or retard) daring the operating parameters of the engine 30 in which fuel enters the respective one of the plurality of cylinders 54 and during the appropriate stroke's position.
In use, the engine 30 is started. Fuel is supplied to each of the plurality of cylinders 54 by the respective fuel injector 142 of the fuel system 140. Intake air 66 is supplied to the engine 30. For example, intake air 66 enters the compressor section 92 and is compressed. From the compressor section 92, intake air 66 passes through the aftercooler 100 and is cooled becoming more dense and enters into the intake passage 98 in the intake manifold 96. From the intake passage 98, as the intake valve 68 in moved into the open position 70 intake air 66 is drawn into the respective one of the plurality of cylinders 54. The intake air 66 and the fuel are combusted. After combustion, as the exhaust valve 74 is moved into the open position 76 the combusted fuel and intake air 66 form the flow of exhaust gas 62. The flow of exhaust gas 62 enters the exhaust passage 86 of the exhaust manifold 84 and passes to the atmosphere.
Under predetermined operating conditions of the engine 30, the exhaust gas recirculation system 110 is actuated. One such predetermined operating condition that would use the exhaust gas recirculation system 110 would be with high load conditions of the engine 30. This condition would provide maximum emissions reduction, specially NOx. For example, the controller 138 receives a signal from at least one of the plurality of sensors 134. The signal is interpreted by the controller 138 and directs a command to the exhaust valve regulator 116. The exhaust valve regulator 116 is moved in a conventional manner from the closed position 122 to the open position 120. Thus, a flow of exhaust gas 62 in allowed to flow through the exhaust valve regulator 116 and the exhaust gas cooler 118, and into and mixes with the flow of intake air 66. In the process of passing through the exhaust gas cooler 118, the flow of exhaust gas 66 is cooled. Additionally, as the hot exhaust gas 66 passes through the exhaust gas cooler 118, heat is absorbed by the engine coolant 36 passing therethrough. Thus, the engine coolant 36 temperature is increased.
Under certain operating parameters of the engine 30 and with the ambient temperature of the atmospheric air being high, 110 degrees Fahrenheit or higher, the heat added by the exhaust gas cooler 118 can cause the cooling system 34 to overheat. Thus, the mode of operation of the engine 30 must be altered to compensate for the overheating of the engine 30 cooling system 34. One option or alternative to solve the overheating problem is to have the plurality paths or maps 132 divided into at least two distinct exhaust emission parameters based on the engine 30 coolant 36 temperature. For example, one of the plurality of paths or maps 132 could be considered a normal coolant temperature strategy and would use a relatively high rate of exhaust gas 62 being mixed with the intake air 66 and the timing of the fuel injector 142 would be advanced to provide the operator with an improved fuel economy. And, another of the plurality of paths or maps 132 could be considered a high coolant 36 temperature strategy and would reduce the amount of exhaust gas 62 being mixed with the intake air 66 and the timing of the fuel injector would be retarded. During the high coolant 36 temperature strategy, fuel economy would be reduced. However, the heat rejection from the exhaust gas cooler 118 would be reduced preventing engine 30 overheating. The plus side to this strategy is that the vehicle cooling system 34, with the preestablished frontal area 18 can be sized in a conventional manner because the high coolant 36 temperature strategy results in a smaller engine beat rejection requirement. Additionally, the vehicle 10 and the engine 30 would run at the best fuel economy most of the time during the normal coolant temperature strategy.
With the present exhaust gas recirculation system 110 and with the control system 130 as defined above, the controller 138 receives a plurality of signals from individual ones of the plurality of sensors 134, interprets the signals and operates the exhaust gas recirculation system 110 depending on the appropriate one of the plurality of paths or maps 132. For example, as interpreted by the controller 138 the exhaust valve regulator 116 is moved between the open position 120 and the closed position 122 depending on the engine 10 operational parameter, path, map or condition. Thus, as the operating conditions of the engine 30 necessitate, the amount of exhaust gas recirculation or flow of exhaust gas 62 is varied and the emissions are controlled within a preestablished parameter. And, with the engine 30 coolant 36 temperature reaching the overheating temperature, the amount of exhaust gas recirculation or flow of exhaust gas 62 to the plurality of cylinders is reduced. This results in less heat rejection by the exhaust gas cooler 118. And, to compensate for the reduced flow of exhaust gas 62 to be mixed with the intake air 66, the timing of the fuel injector 142 is retarded. Thus, the emissions of the engine 30 are maintained within an acceptable level.
Other aspects, objects and advantages of this invention can be obtained from a sturdy of the drawings, the disclosure and the appended claims.
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|U.S. Classification||123/568.12, 123/568.21, 123/568.22|
|International Classification||F02D21/08, F02M25/07|
|Cooperative Classification||F02M26/32, F02D21/08, F02M26/05, F02M26/28|
|European Classification||F02M25/07J4H, F02D21/08, F02M25/07P6C6|
|Nov 4, 2008||CC||Certificate of correction|
|Sep 23, 2011||FPAY||Fee payment|
Year of fee payment: 12