Influence of fumigation methanol on the combustion and particulate emissions of a diesel engine

•Fumigation methanol influences engine combustion and particulate emissions.•It reduces diesel fuel consumed and increases heat released in premixed mode.•Peak cylinder pressure is increased at high engine load but reduced at low engine load.•It increases ignition delay and peak heat release rate but not combustion duration.•Particulate mass and number concentrations reduced at medium and high engine loads. This study is aimed to investigate the effects of fumigation methanol on the combustion and particulate emissions of a diesel engine under different engine loads and fumigation level. Experiments were performed on a 4-cylinder direct injection diesel engine operating at the engine speed of 1920 rev/min with five engine loads. The combustion characteristic analysis indicates that with fumigation methanol, the maximum cylinder pressure decreases at low to medium engine loads but increases at high engine load. Fumigation methanol increases the peak heat release rate and ignition delay but does not significantly change the combustion duration. The fumigation method results in a significant decrease in particulate mass and number concentrations from medium to high engine loads, due to the increase of fuel burned in the premixed mode and a reduction of diesel fuel involved. Fumigation methanol also slightly decreases the fraction of accumulation mode particles and thus the particulate geometric mean diameter (GMD).