Enhanced real-time ammonia slip detection
AssigneeFord Global Technologies, LLC
InventorsChris Riffle, Frank M. Korpics, Michiel J. Van Nieuwstadt, Devesh Upadhyay, David Robert Nader
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Abstract
Various systems and methods are described for detecting ammonia slip. In one example method, an exhaust system with two NOx sensors uses transient responses of the NOx sensors to allocate tailpipe NOx sensor output to NOx and NH3 levels therein. An ammonia slip detection counter with gains is included that determines a probability of NOx and NH3 based on the measured sensor activities that are further processed by a controller to adjust one or more parameters based on the allocation and changes of sensor output.
Claims16
A method for an engine comprising:
- allocating a NOx sensor output to each of NH3 and NOx based on calculating upstream and downstream NOx rates of change relative to an SCR emission device,
- determining an expected downstream NOx rate of change,
- generating an envelope surrounding the expected downstream NOx rate of change, and
- comparing the calculated downstream NOx rate of change to the expected downstream NOx rate of change and the envelope surrounding the expected downstream NOx rate of change, where the expected downstream NOx rate of change is determined based on the calculated upstream rate of change;
- and
- adjusting reductant delivery into engine exhaust via an injector based on the allocation.
A method for performing real-time control of ammonia slip in an engine exhaust system, comprising:
- allocating an output of a NOx sensor arranged downstream of an SCR emission device to each of NH3 and NOx based on:
- predicting a a rate of change of NOx downstream of the
- SCR emission device,
- generating an envelope that surrounds the predicted rate of change, and
- comparing an actual rate of change of NOx downstream of the SCR emission device to the predicted rate of change and the envelope, the actual rate of change based on the output from the NOx sensor downstream of the SCR emission device;
- and
- adjusting delivery of a reductant to engine exhaust upstream of the SCR emission device via an injector based on the allocation.
A system, comprising:
- an engine with an exhaust system;
- an exhaust treatment system disposed in the exhaust system and including an SCR emission device, a urea injector disposed upstream of the SCR emission device, a NOx sensor disposed downstream of the SCR emission device, and a NOx sensor disposed upstream of the SCR emission device;
- and
- a control system in communication with the exhaust treatment system, where the control system includes non-transitory instructions for NH3 slip detection based on a transient NOx signal, wherein the NH3 slip detection includes:
- allocating an output of the NOx sensor disposed downstream of the SCR emission device to each of NH3 and NOx and
- adjusting injection of reductant via the urea injector to engine exhaust gas upstream of the SCR emission device based on the allocation, where the allocation is based on:
- a comparison of an envelope which surrounds an expected rate of change of NOx downstream of the SCR emission device and a calculated rate of change of NOx downstream of the SCR emission device,
- wherein if the calculated rate of change of NOx downstream of the SCR emission device is within the envelope, determining there is a NOx slip condition.
Dependencies are inferred from the claim text.