Reduction of transient NOx emissions based on set-point adaptation of real-time combustion control for light-duty diesel engines

This paper proposes a set-point adaptation algorithm for combustion control to reduce transient NO_x emissions. The set-point adaptation algorithm is activated only when an NO_x emission spike is detected. For the detection of NO_x emission spikes, an empirical NO_x prediction model was developed. The NO_x prediction model was derived based on three key parameters associated with the mechanistic formation of NO: the combustion temperature, mixed gas composition, and combustion duration. The predicted results of the developed NO_x model showed strong linear relation with the measured NO_x emissions, with a root mean square error of 12.92 ppm and an R² of 0.98. Using the proposed NO_x prediction model, transient NO_x emission spikes were detected and the set-point adaptation algorithm was activated to reduce transient NO_x emissions. The set-point adaptation algorithm retarded the combustion phase under such conditions, and the experimental results showed that transient NO_x emission spikes were reduced by the proposed set-point adaptation algorithm by about 25%.