喷油器喷嘴结构参数对空化效应的影响

基于不可压缩流体体积(volume of fluid,VOF)函数多相流模型,模拟喷油器完整喷射周期内的燃油流动和空化特性,获得喷嘴空化形成及发展的关键区域和影响空化效应的关键结构参数,并分析其对流场及空化特性的影响规律。结果表明:较小针阀升程时,在针阀锥形表面台阶和喷孔下边缘位置处发生明显空化现象,当升程增加时,空化集中分布在喷孔位置处,从倒圆处开始诱发并逐渐向下游延伸;针阀台阶夹角增大使得针阀表面台阶处和喷孔下缘的前部的局部空化增强,穴蚀更严重,且燃油流量减小;通过增大针阀座倒圆半径和喷孔直径锥度系数可有效地改善喷孔局部空化程度。

Influence of the Structural Parameters of Injector Nozzle on Cavitation Effect

The fuel flow and cavitation in the nozzle of injector directly affect the fuel injection directly, which may be caused nozzle cavitation erosion. In this paper, Based on the multiphase flow model of incompressible fluid volume function (VOF), the fuel flow and cavitation characteristics during the whole injection cycle of the injector is simulated, and the key area of the formation and development of cavitation in the orifice was obtained. The critical structure parameters of the injector which influence the cavitation were identified, and the law of its influence on the flow field and cavitation characteristics was studied. The results show that cavitation occurs at the step of conical surface of needle valve and the lower edge of orifice when the lift of needle valve is small. When the lift is increased, cavitation is concentrated at the position of orifice, which starts from the inverted circle and extends to the downstream gradually. With the increase of the angle between the steps of the needle valve, the cavitation of the steps on the surface of the needle valve and the front of the lower edge of the injection hole is enhanced, the cavitation is more serious, and the fuel flow is reduced the local cavitation degree can be effectively improved by increasing the rounding radius of needle valve seat and the taper coefficient of orifice diameter.