空化对GDI喷嘴内部流动及喷雾特性的影响

采用两相流非线性空化模型和Huh-Gosman喷雾模型对GDI多孔喷油器喷嘴内部流动和喷雾特性进行模拟。通过流量及喷雾试验对计算模型进行了验证,研究了喷嘴内空化现象对流动及喷雾特性的影响,并从抑制空化、提升流量的角度研究了喷嘴内部流动空化的影响因素及规律。研究结果显示:高压汽油在喷嘴内的流动存在明显的空化现象,空化导致的有效流通面积减小是喷嘴流量减小的原因。针阀升程增加,喷嘴流量先增加较快,后趋于平缓。喷孔的不均匀分布导致各喷孔内的空化状况不同,进而产生流量差异。空化作用也使得喷雾射流在喷孔出口截面的流动参数产生差异,影响喷雾的落点分布和喷雾形态。通过优化喷孔k系数和喷孔入口圆角半径可显著提高喷孔流量。

Effects of Cavitation on Internal Flow and Spray Characteristics in GDI Nozzle

The internal flow and spray characteristics of GDI multi-hole nozzle were simulated with the two-phase non-linear cavitation flow model and Huh-Gosman spray model and the numerical calculation models were verified by flow and spray char-acteristics test.The effects of cavitation flow within nozzle on internal flow and spray characteristics were investigated.Moreo-ver,the influencing factors and law of cavitation flow were revealed from the view of restraining cavitation and improving flow. The results show that it is the high-pressure gasoline within nozzle that leads to the cavitation phenomenon,and the effective flow area decreases caused by the cavitation is the reason why the flow rate of nozzle deceases.With the increase of the needle lift,the flow rate of nozzle increases rapidly and then becomes stable gradually.The asymmetry distribution of nozzle holes leads to different cavitation states in each hole and even different flow rates.The cavitation also causes difference in injection flow parameters in nozzle exit section,which changes the falling point and pattern of spray.By optimizing k coefficient and the fillet radius of nozzle inlet,the flow rate of nozzle improves remarkably.