Effects of diesel pre-injection on the combustion and emission characteristics of a common-rail diesel engine fueled with diesel-methanol dual-fuel

Abstract

The diesel-methanol dual-fuel (DMDF) combustion was performed on a six-cylinder, common-rail diesel engine. To this end, methanol was premixed with air in the intake pipe and ignited by the directly injected diesel fuel in the cylinder. Single and double injection were considered in this study. Double injection included pre-injection and then main injection. The aim was to investigate, in comparison with the single injection strategy, what effects diesel pre-injection strategy may have on the combustion and emission characteristics of the test DMDF engine. The experiment was carried out at 1400r/min, 50% load and different values of the co-combustion ratio. The results show that, for double injection compared with single injection mode, both the heat release rate and the maximum cylinder temperature become lower, while the cycle-to-cycle variation of indicated mean effective pressure becomes higher. The results of emission characteristics indicate that, under double injection mode, the HC emissions decrease, while those of CO, NOx and PM increase. The NOx emissions and the size of particular matter both increase with co-combustion ratio, when diesel pre-injection was applied.