Premixed charge compression ignition engine with optimal combustion control
First Claim
1. A method for operating a premixed charge, compression ignition engine, the engine having a cylinder and a piston moveable in the cylinder, and the method comprising the steps of:
- providing in the cylinder a gaseous medium containing oxygen;
forming a combustible mixture by mixing generally homogeneously into the gaseous medium a first fuel that tends to autoignite relatively less readily and a second fuel that tends to autoignite relatively more readily; and
compressing the combustible mixture with the piston until combustion starts, wherein combustion starts at multiple ignition sites distributed throughout the combustible mixture after a delay in a timing of the start of combustion determined by a ratio of the first fuel to the second fuel.
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Abstract
A premixed charge compression ignition engine, and a control system, is provided which effectively initiates combustion by compression ignition and maintains stable combustion while achieving extremely low nitrous oxide emissions, good overall efficiency and acceptable combustion noise and cylinder pressures. The present engine and control system effectively controls the combustion history, that is, the time at which combustion occurs, the rate of combustion, the duration of combustion and/or the completeness of combustion, by controlling the operation of certain control variables providing temperature control, pressure control, control of the mixture'"'"'s autoignition properties and equivalence ratio control. The combustion control system provides active feedback control of the combustion event and includes a sensor, e.g. pressure sensor, for detecting an engine operating condition indicative of the combustion history, e.g. the start of combustion, and generating an associated engine operating condition signal. A processor receives the signal and generates control signals based on the engine operating condition signal for controlling various engine components to control the temperature, pressure, equivalence ratio and/or autoignition properties so as to variably control the combustion history of future combustion events to achieve stable, low emission combustion in each cylinder and combustion balancing between the cylinders.
217 Citations
36 Claims
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1. A method for operating a premixed charge, compression ignition engine, the engine having a cylinder and a piston moveable in the cylinder, and the method comprising the steps of:
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providing in the cylinder a gaseous medium containing oxygen;
forming a combustible mixture by mixing generally homogeneously into the gaseous medium a first fuel that tends to autoignite relatively less readily and a second fuel that tends to autoignite relatively more readily; and
compressing the combustible mixture with the piston until combustion starts, wherein combustion starts at multiple ignition sites distributed throughout the combustible mixture after a delay in a timing of the start of combustion determined by a ratio of the first fuel to the second fuel. - View Dependent Claims (2)
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3. A method for operating a premixed charge, compression ignition engine, the engine having a cylinder and a piston moveable in the cylinder, and the method comprising the steps of:
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providing in the cylinder a gaseous medium containing oxygen;
forming a combustible mixture by mixing generally homogeneously into the gaseous medium a first fuel that tends to autoignite relatively less readily and a second fuel that tends to autoignite relatively more readily;
compressing the combustible mixture with the piston until combustion starts, wherein combustion starts at multiple ignition sites distributed throughout the combustible mixture after a delay in a timing of the start of combustion determined by a ratio of the first fuel to the second fuel; and
controlling the timing of the start of combustion by varying the ratio of the amount of the first fuel to the amount of the second fuel. - View Dependent Claims (4, 5, 6)
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7. A method of operating an engine, comprising the steps of:
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mixing a first fuel, a second fuel and oxygen in a cylinder when a piston is approximately between 180 degrees and 60 degrees before a top dead center position;
varying a timing of a start of combustion at least in part by providing the first fuel and the second fuel to the cylinder in a determined ratio;
initiating combustion by compression igniting the mixture when the piston is between 20 crank angle degrees before the top dead center position and 10 crank angle degrees after the top dead center position. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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14. An engine comprising;
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an engine body with at least one cylinder;
a piston slidably positioned in each said at least one cylinder, and being movable between a bottom dead center position and a top dead center position;
a liquid fuel supply valve attached to said engine body;
a gaseous fuel supply valve attached to said engine body;
an electronic control unit in control communication with said liquid fuel supply valve and said gaseous fuel supply valve, and being operable to actuate said liquid fuel supply valve when said piston is approximately between 180 degrees and 60 degrees before the top dead center position. - View Dependent Claims (15, 16, 17, 18)
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19. A premixed charge compression ignition internal combustion engine, comprising:
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an engine body;
a combustion chamber formed in the engine body;
an intake air system for delivering intake air, including at least one of air and a mixture of air and fuel, to said combustion chamber;
combustion control system for controlling combustion events to reduce emissions, said combustion history control system including a mixture autoignition property control system for varying an autoignition property of the mixture, said mixture autoignition property control system including a first fuel supply for supplying a first fuel to the engine and a second fuel supply connected to at least one of said intake air system and said combustion chamber for supplying a second fuel to the engine, said first fuel having a first autoignition property and said second fuel having a second autoignition property different from said first autoignition property; and
a processor adapted to control an amount of said second fuel delivered to said at least one of said intake air system and said combustion chamber.
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20. A method for operating a homogeneous charge, compression ignition engine, the engine having a cylinder and a piston moveable in the cylinder, and the method comprising the steps of:
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providing in the cylinder a gaseous medium containing oxygen;
forming a combustible mixture by mixing generally homogeneously into the gaseous medium a first fluid fuel that is relatively difficult to ignite and a second fluid fuel that is relatively easy to ignite; and
compressing the combustible mixture with the piston until combustion starts generally simultaneously at a plurality of locations distributed throughout the combustible mixture after an ignition delay determined by the proportion of the first fuel to the second fuel. - View Dependent Claims (21)
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22. A method for operating a homogenous charge, compression ignition engine, the engine having a cylinder and a piston moveable in the cylinder, and the method comprising the steps of:
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providing in the cylinder a gaseous medium containing oxygen;
forming a combustible mixture by mixing generally homogeneously into the gaseous medium a first fluid fuel that is relatively difficult to ignite and a second fluid fuel that is relatively easy to ignite;
compressing the combustible mixture with the piston until combustion starts generally simultaneously at a plurality of locations distributed throughout the combustible mixture after an ignition delay determined by the proportion of the first fuel to the second fuel; and
wherein the ignition delay begins when the piston is at a predetermined rotational position relative to top dead center and wherein the method further comprises the step of controlling the ignition delay by varying the ratio of the amount of the first fuel to the amount of the second fuel. - View Dependent Claims (23, 24)
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25. A method of operating an engine, comprising the steps of:
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mixing a first fuel, a second fuel and oxygen in a cylinder when a piston is closer to a bottom dead center position than to a top dead center position;
adjusting an ignition delay at least in part by providing the first fuel and the second fuel to the cylinder in a determined proportion;
compression igniting the mixture when the piston is closer to the top dead center position than the bottom dead center position. - View Dependent Claims (26, 27, 28, 29, 30, 31)
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32. An engine comprising;
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an engine housing with at east one cylinder;
a piston slidably positioned in each said at least one cylinder, and being movable between a bottom dead center position and a top dead center position;
a liquid fuel supply valve attached to said engine housing;
a gaseous fuel supply valve attached to said engine housing;
a controller in control communication with said fuel injector and said gaseous fuel supply valve, and being operable to actuate said fuel injector when said piston is closer to said bottom dead center position than said top dead center position. - View Dependent Claims (33, 34, 35, 36)
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Specification