Reducing NOx emissions from an engine while maximizing fuel economy

Claim 1

A method for operating a lean-burn engine with good fuel economy and reduced emissions of NO x , particulates, gaseous hydrocarbons and carbon monoxide, comprising: providing an exhaust system having an exhaust passage leading to a catalytic reactor effective for NO x reduction by selective catalytic reduction utilizing a NO x -reducing reagent selected from the group consisting of ammelide, ammeline, ammonium carbonate, ammonium bicarbonate, ammonium carbamate, ammonium cyanate, ammonium salts of inorganic acids, ammonium salts of organic acids, biuret, cyanuric acid, hexamethylenetetramine, isocyanic acid, lower alkyl amines, melamine, tricyanourea and urea; providing means for mixing exhaust gases from said exhaust passage and incoming air and supplying the resulting mixture to the engine; sensing operating parameters indicative of conditions effective for catalytic NO x reduction; generating an operation signal representative of sensed operating parameters; comparing the operation signal to a reference value to determine if catalytic NO x reduction can be effectively operated; generating a control signal representative of the results of the comparison; and operating at least one of said catalytic reactor and/or said EGR unit in response to said control signal.

Claim 2

A method for operating a lean-burn engine with good fuel economy and reduced emissions of NO x , particulates, gaseous hydrocarbons and carbon monoxide, comprising: providing an exhaust system having an exhaust passage leading to a catalytic reactor effective for NO x reduction by selective catalytic reduction utilizing a NO x -reducing reagent selected from the group consisting of ammelide, ammeline, ammonium carbonate, ammonium bicarbonate, ammonium carbamate, ammonium cyanate, ammonium salts of inorganic acids, ammonium salts of organic acids, biuret, cyanuric acid, hexamethylenetetramine, isocyanic acid, lower alkyl amines, melamine, tricyanourea and urea; providing means for mixing exhaust gases from said exhaust passage and incoming air and supplying the resulting mixture to the engine; sensing operating parameters indicative of conditions effective for catalytic NO x reduction; generating an operation signal representative of sensed operating parameters; comparing the operation signal to a reference value to determine if catalytic NO x reduction can be effectively operated; generating a control signal representative of the results of the comparison; and operating at least one of said catalytic reactor and/or said EGR unit in response to said control signal.

Claim 6

An apparatus for controlling the operation of a lean-burn engine to obtain good fuel economy and low emissions of NO x and particulates, comprising: an exhaust system having an exhaust passage leading to a catalytic reactor effective for NO x reduction by selective catalytic reduction; means to mix exhaust gases from said exhaust passage and incoming air and to supply the resulting mixture to the engine; sensing means for sensing operating parameters indicative of conditions effective for catalytic NO x reduction and generating an operation signal representative thereof; control means for comparing the operation signal to reference value, determine if catalytic NO x reduction can be effectively operated, and generate a control signal representative thereof; and means responsive to said control signal for operating at least one of said catalytic reactor and/or said EGR unit.

Claim 7

An apparatus for controlling the operation of a lean-burn engine to obtain good fuel economy and low emissions of NO x and particulates, comprising: an exhaust system having an exhaust passage leading to a catalytic reactor effective for NO x reduction by selective catalytic reduction; means to mix exhaust gases from said exhaust passage and incoming air and to supply the resulting mixture to the engine; sensing means for sensing operating parameters indicative of conditions effective for catalytic NO x reduction and generating an operation signal representative thereof; control means for comparing the operation signal to reference value, determine if catalytic NO x reduction can be effectively operated, and generate a control signal representative thereof; and means responsive to said control signal for operating at least one of said catalytic reactor and/or said EGR unit.