柴油机孔式喷油嘴内空穴流动的模拟分析

利用混合多相流体模型加空穴模型的方法，模拟了柴油机孔式喷油嘴稳定喷射时嘴内的空穴流动现象，分析了空穴在喷油嘴内形成机理及其分布情况。基于这一模型进一步分析了喷射压力、背压和喷孔长径比、喷孔入口圆角比、非轴对称喷孔等几何结构参数对喷孔内空穴分布的影响。通过模拟计算可知，提高喷射压差和减小喷孔入口圆角半径都可以提高空穴强度，同时也发现提高喷孔长径比可以使空穴在喷孔出口截面上分布更为均匀。从燃油空穴雾化理论的角度出发，空穴强度的提高以及在出口截面上的均匀分布都有利于燃油的破碎雾化。

Simulation Analysis on Cavitation Flow in a Diesel Engine Nozzle

The cavitation flow in a nozzle at steady spray of a diesel engine was simulated, and the formation mechanism and distribution of cavitation inside the nozzle were analyzed using mixed muhiphase flow model coupled with cavitation model. Based on this model, the effects of geometric and structural parame- ters, such as injection pressure, rear pressure, length-diameter ratio, inlet round angle-radius ratio and non-axis symmetry of nozzle, on the distribution of the cavitation inside the nozzle are analyzed. Simula- tion results show that better atomization can be realized by enhancing the cavitation intensity via increasing the injection pressure difference or decreasing the nozzle inlet round angle-radius ratio. Uniform distribution of cavitation at the nozzle exit section is obtained by increasing length-diameter ratio and leads to the improvement of atomization.