Diagnostic for a mid-catalyst NH3 sensor
AssigneeCummins Inc.
InventorsMert Geveci, Feng Liu
Life of this patent
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Abstract
A system and method are disclosed for a selective catalytic reductant (SCR) catalyst with an NH3 sensor operationally coupled mid-catalyst of the SCR catalyst and a controller in electronic communication with the NH3 sensor configured to interpret a diagnostic enablement condition of the NH3 sensor. The controller is configured to control a reductant injector to inject varying reductant amounts over a range of ANR values in response to the enablement condition being satisfied. The controller also is configured to determine a lower bound of estimates of the NH3 amount at the mid-bed catalyst position for the reductant amounts, and determine an NH3 sensor fault condition in response to actual sensor outputs and the NH3 lower bound value.
Claims20
A method, comprising:
- operating an internal combustion engine to produce an exhaust gas to an aftertreatment system including a selective catalytic reduction (SCR) catalyst having a first catalyst portion and a second catalyst portion downstream of the first catalyst portion, the aftertreatment system including an NH3 sensor at a position between the first and second catalyst portions;
- enabling a diagnostic of the NH3 sensor in response to a temperature condition of the SCR catalyst exceeding a first threshold and a flow rate of the exhaust gas being less than a second threshold;
- in response to enabling the diagnostic, estimating an NH3 amount at the position of the NH3 sensor in response to a NOx amount to an inlet of the first catalyst portion and a diagnostic ANR value greater than 1;
- injecting a reductant amount into the exhaust gas in response to the diagnostic ANR value and the NOx amount to the inlet of the first catalyst portion;
- measuring an NH3 amount with the NH3 sensor in response to injecting the reductant amount;
- and
- determining a fault condition of the NH3 sensor in response to a deviation of the measured NH3 amount from the estimated NH3 amount.
A system, comprising:
- an exhaust system for receiving an exhaust gas from operation of an internal combustion engine, the exhaust system including a selective catalytic reduction (SCR) catalyst including a first catalyst portion positioned upstream of a second catalyst portion;
- an NH3 sensor coupled to the exhaust system at a position between the first and second catalyst portions operable to measure an NH3 amount;
- a reductant injector coupled to the exhaust system at a position upstream of the first catalyst portion operable to provide a reductant amount in response to a reductant injection command;
- a NOx sensor upstream of the SCR catalyst configured to provide a signal representative of a NOx amount to an inlet of the first catalyst portion;
- a controller, comprising:
- a diagnostic enablement module structured to enable a diagnostic of the NH3 sensor in response to a temperature condition of the SCR catalyst exceeding a first threshold and a flow rate of the exhaust gas being less than a second threshold;
- an ANR determination module structured to determine varying reductant amounts for injection by the reductant injector based upon the NOx amount in response to enablement of the diagnostic, wherein the varying reductant amounts provide a range of ANR diagnostic values;
- an NH3 estimation module structured to determine an estimate of a lower bound of NH3 amounts at the position of the NH3 sensor in response to the range of ANR diagnostic values and NOx amounts at the inlet to the first catalyst portion;
- and
- an NH3 sensor diagnostic module structured to determine a fault condition of the NH3 sensor in response to actual NH3 amounts measured by the NH3 sensor over the range of ANR diagnostic values deviating from the estimate of the lower bound of the NH3 amounts by more than a threshold amount.
Dependencies are inferred from the claim text.