Strategy of improving fuel consumption and reducing emission at low load in a diesel methanol dual fuel engine

The experiments were performed to achieve a significant reduction in nitrogen oxides (NOx) and soot emissions while achieving no reduction in Brake Thermal Efficiency (BTE) for Diesel Methanol Dual Fuel (DMDF) engine at low load condition. The optimization strategies mainly include internal exhaust gas recirculation (EGR), external EGR, intake air heating and diesel injection timing retarded. NOx and soot emissions, BTE, and combustion characteristics were discussed. Experiments were conducted at 1660 r/min with the output torque 220 N·m, corresponding to 50% of full engine load. The main parameters for evaluating the optimization results include NOx emissions, soot emissions, BTE, Pressure Rising Rate (PRR) and fuel cost. The optimized result of DMDF mode is obviously better than those of diesel mode. The optimization process for DMDF mode weakens the trade-off relationship between key parameters which includes NOx emissions, soot emissions, BTE, PRR and fuel cost. Meanwhile, NOx emissions are significantly lower than those from the baseline diesel mode, which decreases from 9.76 to 1.53 g/kW.h. Soot emissions are almost maintained at the level of the baseline diesel mode. The optimized fuel cost of DMDF mode is greatly improved, and the BTE is slightly higher than that of baseline diesel mode.