High efficiency conversion of nitrogen oxides in an exhaust aftertreatment device at low temperature
AssigneeFord Global Technologies, LLC
InventorsLifeng Xu, Robert Walter McCabe
Life of this patent
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Abstract
A system and method for providing operating conditions that provide higher efficiency NOx reduction in a lean NOx catalyst coupled to a lean-burning internal combustion engine. A catalyst containing reductant is caused to attain a temperature greater than 300° C. After a duration of about 10 seconds at the elevated temperature, the NOx conversion efficiency of the catalyst is increased in the 140-250° C. temperature range.
Claims26
A method for increasing the conversion efficiency of an exhaust gas component in a catalyst coupled to and receiving exhaust gases from an internal combustion engine, comprising the steps of:
- operating at a lean air-fuel ratio;
- determining a quantity of reductant stored in the catalyst;
- injecting reductant into the exhaust gases at a location upstream of the catalyst, when said stored quantity is less than said predetermined quantity and
- raising catalyst temperature above a predetermined temperature by creating a set of operating conditions when said quantity of reductant stored in the catalyst is greater than a predetermined quantity wherein the catalyst absorbs at most a negligible fraction of the exhaust gas component.
A method for increasing the conversion efficiency of an exhaust gas component in a catalyst coupled to and receiving exhaust gases from an internal combustion engine, while operating at a lean air-fuel ratio, comprising the steps of:
- providing an indication that at least a predetermined quantity of reductant is stored in the catalyst;
- injecting reductant into the exhaust gases at a location upstream of the catalyst when an amount of reductant stored in the catalyst is less than said predetermined quantity;
- discontinuing said injection step in response to said indication;
- and
- raising catalyst temperature above a predetermined temperature by creating a set of operating conditions in response to said indication wherein the catalyst absorbs at most a negligible fraction of the exhaust gas component.
A system for increasing the conversion of exhaust gas NOx in a catalyst, the exhaust gases being lean, comprising:
- a combustion chamber in which the exhaust gases are produced, wherein the catalyst coupled to said combustion chamber processes the exhaust gases discharged from said combustion chamber;
- and
- an electronic control unit operably connected to said combustion chamber provides an indication of a quantity of reductant stored in the catalyst and if said quantity is greater than a predetermined quantity, create a set of operating conditions to cause the temperature in the catalyst to exceed a predetermined temperature wherein the catalyst absorbs at most a negligible fraction of the exhaust gas NOx;
- and
- an injector located upstream of the catalyst to supply reductant to the exhaust gases, wherein said electronic control unit actuates said injector to supply reductant when said quantity is less than a predetermined quantity.
A computer readable storage medium having stored data representing instructions executable by a computer to control an internal combustion engine combusting a lean air-fuel mixture and an injector supplying reductant to the engine exhaust gases upstream of a catalyst coupled to the engine comprising:
- instructions for providing an indication of a quantity of reductant stored in the catalyst wherein the catalyst processes exhaust gas NOx and the catalyst absorbs at most a negligible fraction of the exhaust gas NOx;
- instructions for commanding said injector to inject reductant into the exhaust gases at a location upstream of the catalyst when an amount of reductant stored in the catalyst is less than a predetermined quantity;
- and
- instructions for creating a set of operating conditions which cause the temperature in the catalyst to exceed a predetermined temperature, if said quantity is greater than a predetermined quantity.
A method for increasing NOx conversion efficiency in a catalyst coupled to and receiving exhaust gases from a combustion chamber, comprising:
- operating the combustion chamber at a lean air-fuel ratio such that the exhaust gases leaving the combustion chamber include excess oxygen;
- providing an indication that at least a predetermined quantity of reductant is stored in the catalyst;
- injecting reductant into the exhaust gases at a location upstream of the catalyst when a quantity of reductant stored in the catalyst is less than said predetermined quantity;
- decreasing said reductant injection in response to said indication;
- and
- raising catalyst temperature above a predetermined temperature by creating a set of operating conditions in response to said indication wherein the catalyst absorbs at most a negligible fraction of the exhaust gas NOx.
A system for increasing the NOx conversion efficiency of a catalyst processing exhaust gases, comprising:
- a combustion chamber producing therein the exhaust gases;
- an exhaust coupled to said combustion chamber, said exhaust couples said combustion chamber to the catalyst for directing the exhaust gases from said combustion chamber to the catalyst;
- a reductant injector disposed to supply reductant into the exhaust gases in between said combustion chamber and the catalyst;
- an electronic control unit operably connected to said combustion chamber and said injector, said electronic control unit commanding said injector to inject reductant when a quantity of reductant stored in the catalyst is less than a predetermined quantity of reductant;
- said control unit decreasing said injection when said quantity of reductant stored in the catalyst is greater than said predetermined quantity of reductant;
- and said control unit further creating a set of operating conditions to cause the temperature in the catalyst to exceed a predetermined temperature in response to said indication wherein the catalyst absorbs at most a negligible fraction of the exhaust gas NOx.
Dependencies are inferred from the claim text.