Method and system for NOx reduction
AssigneeFord Global Technologies, LLC
InventorsLifeng Xu, Ching-Hsong George Wu, Robert Henry Hammerle
Life of this patent
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Abstract
A system and method for controlling reductant injection upstream of a selective reduction catalyst (SCR) to overcome NOX inhibiting effects by injecting reductant in an amount proportional to engine out NOX concentration when the NOX concentration is above a predetermined level and injecting predetermined amounts of reductant into the SCR catalyst when engine out NOX concentration is below the predetermined level such as when the engine is idling or decelerating.
Claims20
A method for controlling reductant injection into an engine exhaust stream upstream of a selective reduction catalyst coupled to said engine, the method comprising the steps of:
- determining a NOX concentration level upstream of said catalyst;
- controlling the amount of reductant injected into the engine exhaust stream proportional to the NOX concentration if the NOX concentration level is greater than a predetermined NOX concentration level;
- and
- injecting a predetermined amount of reductant into the engine exhaust stream if the NOX concentration level is less than said predetermined NOX concentration level and the amount of ammonia in the catalyst is less than the ammonia storage capacity of the catalyst.
A system for controlling reductant injection into an internal combustion engine exhaust stream upstream of a catalyst coupled to said engine, comprising:
- means for determining a NOX concentration level upstream of said catalyst;
- means for controlling reductant injection as a function of NOX concentration if the NOX concentration level is greater than a predetermined NOX concentration level and for injecting a predetermined amount of reductant into the exhaust stream if the NOX concentration level is less than said predetermined NOX concentration level and the amount of ammonia in the catalyst is less than the catalyst ammonia storage capacity.
An article of manufacture comprising:
- a computer storage medium having a computer program encoded therein for controlling reductant injection into the exhaust stream of an internal combustion engine, upstream of a selective reduction catalyst coupled to said engine, said computer storage medium comprising:
- code for causing the computer to determine a NOX concentration level upstream of said catalyst;
- code for causing the computer to control the amount of reductant injected proportional to NOX concentration if the NOX concentration level is greater than a predetermined NOX concentration level and to inject a predetermined amount of reductant if the NOX concentration level is less than said predetermined NOX concentration level and the amount of ammonia in the catalyst is less than the ammonia storage capacity of the catalyst.
A method for controlling reductant injection into an engine exhaust stream upstream of a catalyst coupled to said engine, the method comprising the steps of:
- determining an engine-out NOX concentration level;
- controlling the amount of reductant injected into the engine exhaust stream as a function of the NOX concentration if the NOX concentration level is greater than a predetermined NOX concentration level;
- determining the exhaust gas flow rate;
- reducing the value of a variable Q, indicative of catalyst reductant storage capacity, by an amount proportional to said NOX concentration level and said flow rate if said NOX concentration is greater than said predetermined NOX concentration level.
Dependencies are inferred from the claim text.