柴油机高压喷油嘴喷射过程空化效应数值模拟

为揭示柴油机高压喷油嘴喷射过程空化机理,根据质量守恒、动量守恒、混合组分平衡的基本规律建立了高压喷油嘴喷射过程空化效应数学模型,并对高压喷油嘴喷射过程空化效应进行了数值模拟分析,得出了曲率半径、压力波动幅度及柴油的部分物理参数对高压喷油嘴喷射过程空化效应的影响规律:随着喷油嘴入口处的曲率半径增大,喷孔内气相体积分数越来越小,空穴层的厚度也越来越薄,高压喷油嘴雾化性能变差;随着压力波动幅度的减少,喷油嘴出口质量流量变化越来越小,有利于喷油嘴喷油量的精确控制;燃油温度、喷油压力的提高使得喷油嘴内部空化现象得到加强,但是压力的增大更有利于空穴增强,从而有利于燃油雾化.

Numerical Simulation of Cavitation Effect in the Injection Process of High Pressure Injector Nozzle in Diesel

In order to reveal the cavitation mechanism of diesel injection process, a numerical model has been developed to investigate the cavitation processes in injector nozzle according to the conservation of mass, momentum and the basic rules of the mixture fraction balance. Then, the numerical simulation results of cavitation effect were analyzed. It is discovered that the atomization performance of high pressure injection nozzle becomes poor and the vapor volume fraction and the thickness of cavitation in the injector nozzle decrease, and the radius of the nozzle inlet rounding lip tends to increase. The numerical study also points out that the amplitude of inlet pressure is reduced with the small variations of outlet mass flow, which is better for the accurate control of injection quantity. The nozzle internal cavitation phenomenon is strengthened at elevated fuel temperature and injection pressure conditions. However, increasing the injection pressure is more conducive to enhancement atomization.