Control of highly diluted combustion in Diesel engines

In this paper, an open-loop control strategy to improve the stability of highly diluted Diesel combustion during sharp transients is proposed. The main advantage of this open-loop method is that no additional in-cylinder sensor is required. The approach coordinates existing airpath and fuelpath controllers, and aims at accurately controlling the end of the cool-flame phenomenon. For this purpose, the injection time is adjusted based on an auto-ignition model and a cool-flame model. Both models are expressed under integral forms, named knock integral models. Experimental results obtained on a test bench and on-board a vehicle are presented. The results highlight the relevance of the approach in terms of combustion stability improvement, pollutant emissions and noise.