Patent ID: 11879375
Assignee: PACCAR INC
Field: Environmental technology (Chemistry)
Classification: CPC F  Y | IPC F

Claim 0:
1. A method, comprising:
operating a diesel engine of a heavy-duty truck such that the diesel engine generates an exhaust gas flow that enters an exhaust after-treatment system of the heavy-duty truck, the exhaust after-treatment system including a selective catalytic reduction system;
measuring a level of NOx gases in the exhaust gas flow downstream of the selective catalytic reduction system;
controlling a diesel exhaust fluid injector upstream of the selective catalytic reduction system to inject diesel exhaust fluid into the exhaust gas flow upstream of the selective catalytic reduction system at an injection rate that is based on the measured level of NOx gases;
determining whether ammonia slip is occurring at the selective catalytic reduction system, including:
adjusting the injection rate, thereby changing an ammonia-to-NOx ratio at the selective catalytic reduction system;
measuring first levels of NOx gases in the exhaust gas flow upstream of the selective catalytic reduction system and second levels of NOx gases in the exhaust gas flow downstream of the selective catalytic reduction system as the ammonia-to-NOx ratio at the selective catalytic reduction system changes;
determining a measured efficiency of the selective catalytic reduction system based on the measured first and second levels of NOx gases; and
determining whether the measured efficiency is positively or negatively correlated with the changing ammonia-to-NOx ratio; and

adjusting the injection rate based on whether ammonia slip is occurring at the selective catalytic reduction system.