Method and apparatus to selectively reduce NOx in an exhaust gas feedstream
AssigneeGM Global Technology Operations LLC
InventorsSteven J. Schmieg, Richard J. Blint, Ling Deng, Michael B. Viola, Jong-Hwan Lee
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Abstract
A method and apparatus are described to selectively reduce NOx emissions of an internal combustion engine. An exhaust aftertreatment system includes an injection device operative to dispense a hydrocarbon reductant upstream of a silver-alumina catalytic reactor device. A control system determines a NOx concentration and hydrocarbon/NOx ratio based upon selected parameters of the exhaust gas feedstream and dispenses hydrocarbon reductant during lean engine operation. Included is a method to control elements of the feedstream during lean operation. The hydrocarbon reductant may include engine fuel.
Claims30
Method to selectively reduce NOx emissions in an exhaust gas feedstream of an internal combustion engine, comprising:
- determining a NOx concentration and a mass flow rate of the exhaust gas feedstream and an inlet temperature to a silver-alumina catalytic reactor device;
- determining a preferred hydrocarbon/NOx ratio to reduce the NOx concentration across the silver-alumina catalytic reactor device, the preferred hydrocarbon/NOx ratio varying in response to the NOx concentration, the mass flow rate of the exhaust gas feedstream and the inlet temperature to the silver-alumina catalytic reactor device;
- determining a quantity of hydrocarbon reductant that achieves the preferred hydrocarbon/NOx ratio in the exhaust gas feedstream upstream of the silver-alumina catalytic reactor device;
- dispensing the quantity of hydrocarbon reductant into the exhaust gas feedstream upstream of the silver-alumina catalytic reactor device;
- and
- selectively controlling a mass flow rate of hydrogen in the exhaust gas feedstream upstream of the silver-alumina catalytic reactor device.
Method to control NOx concentration output from an exhaust aftertreatment system comprising a silver-alumina catalytic reactor device during lean operation of an internal combustion engine, comprising:
- determining a preferred hydrocarbon/NOx ratio to achieve a NOx emissions reduction across the silver-alumina catalytic reactor device, the preferred hydrocarbon/NOx ratio varying in response to a NOx concentration and a mass flow rate of the exhaust gas feedstream and an inlet temperature to the silver-alumina catalytic reactor device;
- controlling a concentration of engine-out NOx;
- controlling a concentration of engine-out oxygen;
- determining a quantity of hydrocarbon reductant that achieves the hydrocarbon/NOx ratio for the NOx concentration;
- selectively dispensing the quantity of hydrocarbon reductant into the exhaust gas feedstream upstream of the silver-alumina catalytic reactor device;
- and,
- selectively controlling a mass flow rate of hydrogen into the exhaust gas feedstream upstream of the silver-alumina catalytic reactor device.
Dependencies are inferred from the claim text.