往复式汽油直喷发动机燃油喷雾特性研究

通过试验研究了高压燃油喷射系统和涡旋喷油器的喷雾特性,在不同喷射压力、背压压力和喷油持续期条件下,利用高速摄像机对喷入定体积容器的雾态燃油进行了喷雾贯穿距离、喷雾锥角、喷雾远端燃油发展速度和液滴特性等参数的测量.试验结果表明在低背压压力下,喷雾呈现出空锥、较大范围的分布形态,有利于实现燃油与空气的均质混合;然而在高背压条件下,喷雾呈现出紧凑密集的分布形态,有利于实现燃油与空气的分层混合.获得的贯穿距离经验公式与试验测量值在一定范围内是一致的.低背压条件下,涡旋形态出现在喷雾的远端,而在高背压条件下,涡旋形态出现在喷雾的中部.

Study on fuel spray characteristics of gasoline direct injection reciprocating engine

In order to reveal the influences of high pressure fuel injection system on the performance including fuel consumption and exhaust emissions of gasoline direct injection(GDI) engines,the spray characteristics of high pressure swirl type of GDI injector were investigated experimentally and numerically.The experimental analyses had been carried out that the fuel injection into a constant volume chamber within different ambient pressures was visualized by high speed complementary metal oxide semiconductor(CMOS) camera.The spray development,spray penetration,spray cone angle,spray tip velocity and droplet characteristics were measured at various injection pressure,ambient back pressure and at different injection durations.Experimental results show that under the low back pressure ambient conditions,the spray comes out a hollow cone with wide spray angle and initial spray slug at the tip which meet the mixing control concept of homogenous mixture preparation,while the spray exhibits a solid compact cone under high back pressure which satisfy the stratified mixture preparation concept.An obtained empirical equation for spray penetration is validated by experimental results.Vortexes in the opposite direction exist in the rear part of the spray under low back-pressure ambient conditions while the vortexes form in the middle part under high ambient pressure ambient conditions.