柴油机双层多孔喷油嘴内部空穴两相流动研究

Cavity flow in double-layer multi-holes diesel injector nozzle

针对柴油机喷油嘴内部两相流动影响柴油的雾化质量、燃烧特性及整车的排放特性,而柴油机喷油嘴头部细微结构的变化显著影响喷油嘴内部流动等问题.以某型国产喷油器喷油嘴为对象,在X射线精确测量其几何结构参数的基础上建立物理模型,基于多维数值模拟软件AVL FIRE对喷孔内部空穴两相流动特性进行模拟,分析不同位置喷孔及不同喷射压力对喷孔内部两相流动特性的影响.结果表明:同一喷射压力下,上下层喷孔位置对喷孔内部空穴产生时刻、分布区域及强度都产生影响,压力分布、液相速度分布及液相湍动能分布也各不相同;不同喷射压力下,空化强度随喷油压力的增加而提高.

In diesel engines,the cavity flow in nozzles not only greatly affects the characteristics of fuel atomization,but also has great influence on the subsequent combustion and exhaust emissions. However,the changing of detail structure of diesel nozzle tip greatly affects the flow characteristics in the nozzle hole. Taking a certain type of nozzle as research object,the simulative calculation model of multi-phases flow in the engine nozzle hole with high-pressure injection was established by AVL FIRE software.The effects of different orifice position and injection pressure on the characteristics of two-phase flow were investigated. The results show that when the injection pressure is fixed,the happened moment,the distribution region and the intension of cavitation in nozzle are affected by nozzle position,and the distribution of pressure,the turbulence velocity and the liquid turbulence energy are also different.When the injection pressure changes,the intension of the cavitation phenomena is promoted by the increase of injection pressure.