Patent ID: 8800274

Claim:
Method for operating an internal combustion engine configured to operate in a compression-ignition combustion mode and including an exhaust aftertreatment system comprising an ammonia-selective catalytic reduction device, the method comprising: determining a present engine NOx generation rate; determining an actual NOx reduction rate of the ammonia-selective catalytic reduction device; determining an ammonia slip rate from the ammonia-selective catalytic reduction device corresponding to the actual NOx reduction rate of the ammonia-selective catalytic reduction device and the present engine NOx generation rate; and controlling, by a controller, the engine to adjust the present engine NOx generation rate in response to the ammonia slip rate from the ammonia-selective catalytic reduction device, comprising: determining an actual ammonia storage trajectory for the ammonia-selective catalytic reduction device corresponding to the present engine NOx generation rate, adjusting the present engine NOx generation rate to achieve a preferred ammonia storage trajectory associated with a setpoint amount of stored ammonia to prevent said ammonia slip, the setpoint amount of stored ammonia determined in relation to an inlet temperature of the ammonia-selective catalytic reduction device, employing an inverse engine NOx generation model to determine a fraction of externally recirculated exhaust gas that achieves the adjusted engine NOx generation rate, and controlling flow of the externally recirculated exhaust gas to achieve the fraction of externally recirculated exhaust gas that achieves the adjusted engine NOx generation rate.