直喷汽油机多孔喷油器喷嘴内部流动数值模拟

Numerical Simulation of Nozzle Flow in GDI Multi-hole Injector

摘要:

采用双流体法应用线性空化模型对某直喷汽油机多孔喷油器喷嘴内部流动形态进行模拟，分析了喷嘴内空化流动发展规律，总结并比较了几种判断空化流动的方法。模拟结果表明：在喷孔内及针阀开启关闭时与阀座缝隙间均发现有空化现象；空化形态不稳定，随时间变化；空化造成喷嘴流量减小流速增大，各孔流量亦产生差异；临界空化数可以有效预测空化现象；GDI多孔喷嘴仅在喷射压力很小而喷射背压很大的分层燃烧方式下有可能不空化。

Abstract:

The two-fluid method using linear cavitation model was utilized to simulate GDI multi-hole injector nozzle flow. The evolutionary law of the cavitation flow pattern was analyzed. Cavitation criterions were summarized and compared. Results showed that cavitation was formed at the hole corner and the gap between the moving needle and valve seat. Cavitation flow pattern was unstable and changed with time. Nozzle flow rate decreased and while exit velocity increased due to the cavitation. Also each hole flow rate was different. The critical cavitation number was efficient to predict the cavitation. The non-cavitation flow of GDI multi-hole injector could only be appeared when the injector worked in low injection pressure and high ambient pressure for stratified combustion applications.