Experimental investigation on different injection strategies in a heavy-duty diesel engine: Emissions and loss analysis

Experiments were carried out to investigate different injection strategies on a heavy-duty diesel engine. In particular, pilot/main, post/main and single main injection strategies were considered. Engine speed, load, exhaust gas recirculation rate and relative air/fuel ratio were held constant, whereas pilot and post injection fuel masses and injection timings were varied. For each measurement, heat release and detailed loss analyses were carried out to compare the influence of different injection strategies on the fuel conversion process and its associated efficiencies. As it is known, fuel conversion efficiency depends strongly on the injection timing, in particular on the main injection timing. However, the detailed loss analysis reveals that fuel conversion efficiency is largely determined by the interaction between real combustion and wall heat losses, respectively. To complete the analysis, emissions of nitric oxides, soot mass and particle number of the different injection settings are compared.