柴油机喷孔内部空化效应的可视化实验研究

Visualization of Cavitation in Diesel Nozzle Orifice

柴油机喷孔内空化现象显著影响燃油雾化质量.针对目前广泛应用的VCO型喷嘴,设计大尺度透明喷嘴稳态实验系统,全面研究了无量纲数、雷诺数、喷嘴射流参数和结构参数对喷嘴内空化过程的影响.结果表明,空化数对空化剧烈程度影响显著,雷诺数对空化剧烈程度影响小于空化数;射流参数直接影响流体流动状态,增大入口压力、减小出口压力和针阀升程能使喷孔内的空化现象显著增强;结构参数决定喷孔内流动形式,增大喷孔倾角、直径和长径比,采用入口圆角等措施会抑制空化的产生.

Cavitation in diesel nozzle orifice is one of the most important reasons for the atomization of fuel liquid jet. VCO-type nozzle is widely used in internal combustion engines nowadays, and based on this nozzle, a large-scale transparent nozzle steady-state test rig was designed and several important parameters including cavitation number, Reynolds number, jet parameters and structural parameters were used to analyze the cavitation flow in nozzle. The results indicate that cavitation number significantly affects the cavitation and the effect of Reynolds number on cavita- tion is smaller than that of cavitation number; jet parameters directly influence the flow state, and the increase in inlet pressure and the decrease in outlet pressure and neddle lift will enhance cavitation; structural parameters decide flow patterns in noddle, and increasing nozzle inclination angle, nozzle diameter, the ratio of length to diameter and inlet corner radius will inhibition cavitation.