US 9,038,373 B2 · Ammonia sensor control of an SCR aftertreatment system

Abstract

A system includes an engine, an exhaust conduit for the engine, a first SCR catalyst fluidly coupled to the exhaust conduit, and a second SCR catalyst fluidly coupled to the exhaust conduit at a position downstream of the first SCR catalyst. The system further includes an ammonia sensor positioned between the first and second SCR catalysts. A reductant doser is positioned upstream of the first SCR catalyst. The system includes a controller that determines an amount of NH3 present from the NH3 sensor, and computes an actuator response function from at least one operating condition of the first SCR catalyst. The actuator response function includes a reductant injector response as a function of the amount of NH3, and the actuator response function includes a response discontinuity. The controller further determines a reductant injection amount from the amount of NH3 and the actuator response function, and provides a reductant injector command.

Claims43

Dependent claims

A method, comprising:

determining an amount of ammonia (NH3) present at a first exhaust gas conduit position that is downstream of a first selective catalytic reduction (SCR) catalyst and upstream of a second SCR catalyst;
determining an actuator response function in response to at least one operating condition of the first SCR catalyst, wherein the actuator response function comprises a reductant injector response as a function of the amount of NH3, the actuator response function having a response discontinuity;
determining a reductant injection amount in response to the amount of NH3 and the actuator response function;
injecting an amount of reductant upstream of the first SCR catalyst in response to the reductant injection amount;
and
further comprising determining whether an NH3 fill-up override condition is present, and increasing the injected amount of reductant in response to the NH3 fill-up override condition.

3 more elements

An apparatus, comprising:

a reductant doser operationally coupled to an exhaust conduit at a position upstream of a first SCR catalyst;
and
a controller operationally coupled to control the reductant doser, the controller comprising:
an ammonia (NH3) determination module structured to determine an amount of NH3 present at a first exhaust gas conduit position, the first exhaust gas conduit position downstream of the first SCR catalyst and upstream of a second SCR catalyst;
a response bounding module structured to compute an actuator response function in response to at least one operating condition of the first SCR catalyst, wherein the actuator response function comprises a reductant injector response as a function of the amount of NH3, the actuator response function having a response discontinuity;
a dosing amount module structured to determine a reductant injection amount in response to the amount of NH3 and the actuator response function;
a dosing control module structured to provide a reductant injector command in response to the reductant injection amount;
a response dampening module structured to dynamically track a variability parameter, and to modify the actuator response function in response to the variability parameter, wherein the variability parameter and modification comprise a combination selected from the combinations consisting of:
the variability parameter comprises a recent error history variability and the response dampening module is structured to change an amplitude of the actuator response function inversely with the recent error history variability;
the variability parameter comprises an inlet variability and an outlet variability, and the response dampening module is structured to increase an amplitude of the actuator response function when the inlet variability is high and the outlet variability is low;
the variability parameter comprises an inlet variability and an outlet variability, and the response dampening module is structured to decrease an amplitude of the actuator response function when the inlet variability is low and the outlet variability is high;
the variability parameter comprises an inlet variability and the response dampening module is structured to increase an amplitude of the actuator response function when the inlet variability is high;
and
the variability parameter comprises an outlet variability, and the response dampening module is structured to decrease an amplitude of the actuator response function when the outlet variability is high;
wherein the reductant injector command operates the reductant doser to inject an amount of reductant upstream of the first SCR catalyst equal to the reductant injection amount.

12 more elements

A system comprising:

an internal combustion engine;
an exhaust conduit fluidly coupled to the internal combustion engine;
a first SCR catalyst fluidly coupled to the exhaust conduit;
a second SCR catalyst fluidly coupled to the exhaust conduit at a position downstream of the first SCR catalyst;
a third SCR catalyst fluidly coupled to the exhaust conduit at a position downstream of the second SCR catalyst;
a first ammonia sensor operationally coupled to the exhaust conduit at a first exhaust gas position downstream of the first SCR catalyst and upstream of the second SCR catalyst;
a second ammonia sensor operationally coupled to the exhaust conduit at a position between the second SCR catalyst and the third SCR catalyst;
a reductant doser operationally coupled to the exhaust conduit at a position upstream of the first SCR catalyst;
and
a controller operationally coupled to control the reductant doser, the controller comprising:
an ammonia (NH3) determination module structured to determine an amount of NH3 present at the first exhaust gas position;
a response bounding module structured to compute an actuator response function in response to at least one operating condition of the first SCR catalyst, wherein the actuator response function comprises a reductant injector response as a function of the amount of NH3, the actuator response function having a response discontinuity;
a dosing amount module structured to determine a reductant injection amount in response to the amount of NH3 and the actuator response function;
a dosing control module structured to provide a reductant injector command in response to the reductant injection amount;
and
a NOx trimming module structured to adjust the reductant injector command in a feedback control loop to control a second ammonia amount measured at the second ammonia sensor to a small, non-zero value;
wherein the reductant injector command operates the reductant doser to inject an amount of reductant upstream of the first SCR catalyst equal to the reductant injection amount.

14 more elements

Dependencies are inferred from the claim text.

Ammonia sensor control of an SCR aftertreatment system

Life of this patent

Ammonia sensor control of an SCR aftertreatment system

Life of this patent

Abstract

Claims43