直喷式柴油机燃油喷射终止后雾场滴径分布的测量研究

An Investigation of Droplet Size Distribution After Ending of Fuel Injection in D.I.Diesel Engines

采用Ｍａｌｖｅｒｎ粒子分析仪在较大的喷射压力范围内对喷射终止后油束内部的燃油滴径分布规律进行了测量研究。研究发现，在喷油结束后油束尾部存在着由滴径很大的油滴群所组成的浓燃油区，其索特平均直径均大于喷油持续期内喷出的燃油。这部分燃油混合的相当缓慢，在本试验范围内，其完全消失的时间均在２ｍｓ以上，可以认为停喷以后油束尾部燃油的混合方式主要受油滴的蒸发和扩散所控制，而油束前端混合主要受卷吸所控制。

In this investigation,the fuel spray characteristics after the ending of injection have been studied by using Malvern Droplet Sizer.The results showed that a rich fuel region occurs in the tail of the spray mainly consisting of fuel droplets with much larger SMD than those in the injection period.The mixing process of the fuel and air in the spray tail is rather slow and lasts longer than 2 ms.It seems that the mixing process after the ending of injection should be considered to take place in two ways:mainly by air entrainment around the spray tip,and mainly by fuel evaporation and diffusion around the spray tail.