缸内直喷汽油机喷嘴内流动影响参数分析

Parameters analysis of injector internal flow forgasoline direct injection engine

为了研究缸内直喷汽油机喷油嘴内流动特性及影响喷孔出口流动参数的因素,建立了欧拉多流体模型对喷嘴内流动进行模拟计算,并对所建模型进行了验证.分析了不同介质和不同喷嘴进出口压差下喷孔内流动特征及影响喷孔出口截面流动参数的因素.结果表明:气泡数密度增大则空穴程度增大,但当气泡数密度大于一定值时,空穴流动趋于稳定;随着空穴程度的增大,喷孔出口截面平均速度增大,平均湍动能减小;喷嘴进出口压差的增大,有利于空穴的发生;喷嘴内湍动和气泡与流动介质间相对运动产生的压力波动,有利于喷嘴内空穴发生;在较高的喷嘴进出口压差的情况下,局部湍动对喷孔出口截面的湍动能影响不可忽略;喷孔内流量系数主要受空穴程度影响.

In order to study the internal flow characteristics of injector and the influence parameters of holes orifice flow for gasoline direct injection engine,the Euler multifluid model was established and verified by experiments.Based on the relevant parameters analysis with different mediums and different pressure difference between inlet and outlet section,the influence parameters of holes outlet section were investigated.The results show that the cavitation level increases with the increasing of bubble number density,while the cavitation flow in nozzle becomes constant when the bubble number density is over a certain value.With the increase of cavitation degree,the average velocity increases with decreased average turbulence energy at the nozzle outlet section.The cavitation can be intensified by the enhancing of pressure difference between inlet and outlet of injector.The pressure oscillation from flow disturbances and relative motion between flow mediums are beneficial to cavitation.For high pressure difference between nozzle inlet and outlet section,the turbulence energy affected by pressure oscillation is not ignorable.The discharge coefficient of nozzle is mainly influenced by the cavitation degree.