闪沸喷雾孔几何形状对孔内流动特性影响的数值模拟  

Numerical simulation of the effects of nozzle geometry on the in-nozzle flow-characteristics of flash boiling sprays

作　　者：尹鹏[1] 许敏[1] YIN Peng;XU Min(Shanghai Jiao Tong University,Shanghai 200240,China)

机构地区：[1]上海交通大学机械与动力工程学院,上海200240

出　　处：《汽车安全与节能学报》2024年第3期360-367,共8页Journal of Automotive Safety and Energy

基　　金：国家自然科学基金资助项目(51876126)。

摘　　要：研究了汽车直喷汽油机喷嘴的几何形状对于闪沸喷雾孔内流动以及相变过程的影响机理。基于热不平衡假设建立了一维的两相相变流动模型,对于具有不同喷孔流道长度、直径、入口处圆角以及流道锥角的结构,分析了闪沸喷雾孔内流动的特性。将该模型结果与作者团队先前的实验结果进行了精度比对,验证了模型的准确性。结果表明:喷孔流道长度越长,孔径越小,从而孔内相变越剧烈。流道入口处圆角会减少喷孔内部蒸汽的生成。收缩型喷孔压降较小,孔内蒸汽相的生成也相应减少,从而扩张型喷嘴增大蒸汽产生速率。不同的喷孔结构,改变了流道内的压力以及速度分布;压力分布影响了气泡的生长速率,速度分布影响了气泡的生长时间,而两者共同作用影响了孔内的相变特性。This paper investigated the influence of nozzle geometry on the in-nozzle flow and phase-change process of flash boiling sprays in the direct-injection gasoline-engine cars.A one-dimensional two-phaseflow model was developed based on the thermal non-equilibrium assumption to analyze the in-nozzle flow characteristics of the flash boing spray with different nozzle lengths,different diameters,different rounding angles at the inlet,and different taper angles.The model’s results were verified through the accuracy comparison with the previous experimental results by the authors'team.The results show that the longer the nozzle channel length,the smaller orifice diameter,and the more intense of the phase transition in nozzles,while the round corners at the nozzle entrance reduces the vapor generated inside nozzles.The convergent nozzle has a smaller pressure drop and the generation of vapor phase inside the nozzle is reduced accordingly,while the divergent nozzle increases the vapor generation rate.The different nozzle geometries change the pressure distribution and the velocity distribution in the nozzle.The pressure distribution governs the bubble growth rate,while the velocity distribution affects the bubble growth time,both of which ultimately affect the phase change characteristics within the nozzle.

关 键 词：汽车动力 直喷汽油机 闪沸喷雾 热不平衡 孔内流动 两相流 数值模拟 

分 类 号：U464.136.1[机械工程—车辆工程]