Abstract
Methanol was injected into the suction port of each cylinder in an ordinary direct injection diesel engine, and was ignited by a small amount of gas oil as an ignition source. The effects of the equivalence ratio of methanol, the injection amount and the injection timing of gas oil, the intake temperature and the compression ratio on ignition, the maximum burning rate of methanol mixture and the knock limit were investigated experimentally. It is found that the maximum burning rate of methanol is almost independent on the intake temperature until knock onset, then, the burning process of methanol is "flame propagation". As results, a marked improvement in the trade-off between NO_x and smoke was achieved maintaining a high thermal efficiency by a suitable combination between the parameters mentioned above for each engine load further adopting the high EGR rate and the small orifice size nozzle as well.
