Combined cycle engine
AssigneeThe United States of America as represented by the Administrator of the U.S. Environmental Protection Agency
InventorsCharles L. Gray, Jr., Karl H. Hellman
Life of this patent
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Abstract
A method of operation of an internal combustion engine to minimize NOx emission in exhaust gas involves detection of load on the vehicle engine as either a low load or a high load. While a low load is detected unthrottled air and a quantity of fuel providing for lean combustion are mixed with injection of fuel adjacent top dead center in the compression stroke. While a high load condition is detected, throttled air and a quantity of fuel governed by sensed oxygen content of the exhaust gas are mixed in an approximate stoichiometric ratio with injection of the fuel much earlier than injection at low load, preferably during the intake stroke.
Claims16
A method of operation of an internal combustion engine, having a combustion chamber associated with each of a plurality of piston cylinders, to minimize NOx emission in exhaust gas, said method comprising:
- detecting load on the vehicle engine as a low load or a high load;
- responsive to detection of a low load, admitting a first quantity of air into the combustion chamber during an intake stroke and starting injection of a first quantity of fuel, during a compression stroke and adjacent top dead center, to form a first, lean combustion mixture wherein the first quantity of air is substantially in excess of stoichiometry;
- igniting said lean combustion mixture;
- responsive to detection of a high load, admitting a second quantity of air into the combustion chamber during an intake stroke and starting injection of a second quantity of fuel significantly earlier, relative to top dead center in the compression stroke, than start of injection of the first quantity of fuel, said second quantities of air and fuel being controlled to provide a second, substantially stoichiometric combustion mixture;
- and
- igniting said substantially stoichiometric combustion mixture.
Dependencies are inferred from the claim text.