直喷式柴油机的燃油喷射特性是降低排放的重要因素。通过抑制初期喷油率、提高喷油后期的喷油率、控制针阀升程、缩短喷油时间能同时达到降低NO_X排放及烟度的目的。但控制喷油压力时,因喷油初期的压力低,故扩散燃烧缓慢,使燃油耗恶化,也未看到改善烟度的效果。 The direct injection diesel fuel injection characteristics are important factors to reduce emissions. By inhibiting the initial fuel injection rate and improve the late injection rate, control the needle valve lift, shorten the injection time can achieve the purpose of reducing NO_X emissions and smoke at the same time. However, when controlling the injection pressure, due to the low pressure at the initial injection stage, the diffusion combustion is slow and the fuel consumption is deteriorated, and the effect of improving the smoke level is not seen either.