直噴ディーゼルノズルから噴射したジメチルエーテル (DME) の着火特性

抄録

Experiments were performed to clarify the ignition characteristics of dimethyl ether (DME) injected by a D.I. diesel injector into a high-pressure, high-temperature vessel. Ambient air pressure, temperature, oxygen concentration and nozzle valve opening pressure were changed as experimental parameters. The results clarify the differences between the DME and a conventional diesel fuel in the ignition characteristics such as flame luminosity characteristics and ignition delay. A non-luminous flame is observed in the ignition process of the DME spray. In the case of ordinary air (oxygen concentration 21%), the ignition delay for the DME spray is almost the same as the diesel fuel spray under a high ambient pressure, whereas under a low ambient pressure, the ignition delay for the DME spray is shorter than the diesel fuel spray. In the case of low oxygen concentration, the ignition delay for the DME spray is shorter than the diesel fuel spray under high ambient pressure as well as low ambient pressure. The effect of the nozzle valve opening pressure on the ignition delay is very small for the DME spray, whereas the ignition delay for the diesel fuel spray is increased with decrease in the valve opening pressure.