共轨系统小压力室喷油嘴喷雾特性

Spray Characteristics of SAC Nozzle in Common-Rail System

柴油机喷油嘴是燃油系统和燃烧室之间的关键接口,对燃油雾化非常重要.设计加工了喷雾需要的单孔喷油嘴,检测了喷孔的入口和出口尺寸.喷油嘴经过液体挤压研磨处理,并测试了喷油嘴在挤压研磨前后10,MPa下的高压流量.液体挤压研磨能够提高流量系数10%～15%.测得给定工况下试验喷油嘴的喷油规律和针阀升程,用Matlab编程得到的结果能够清楚地反映喷雾特性.试验研究了环境压力、喷孔直径、喷孔K系数和轨压等对小压力室喷油嘴单孔喷雾的头部贯穿距离、喷雾锥角和投影面积等宏观特性的影响.增大喷孔直径和K系数,油束的贯穿距离和投影面积增大,喷雾锥角减小.增大背压,环境密度增大,贯穿距离和投影面积减小,但喷雾锥角增大.轨压提高,贯穿距离和投影面积增大,喷雾锥角先减小后增大,但变化的幅度不明显.喷孔倒锥喷油嘴相比正锥度和传统圆柱孔能够提高流量系数到0.93.在考虑发动机循环喷油量和喷油持续期的基础上可以选择更小的喷孔出口直径使雾化更好.

Diesel nozzle is key interface between injection system and combustion chamber. Characteristics of spray atomization are very important. Single-hole nozzle was designed. The diameters of inlet and outlet were measured by Macrona. Flow rate of the nozzle at 10 MPa pressure were tested. Hydro grinding method was used to increase the flow coefficient by approximately 10%-15%. Injection rate and needle lift curve were measured at a given operation condition on the injection test bench. The results obtained with the home made program from the frozen picture could reflect the spray characteristics. Macroscopic char- acteristics like spray tip penetration, spray angle and area were investigated at different conditions with SAC nozzle. Increasing outlet diameter and K factor increase the spray tip penetration and the projected area and decreases the spray cone angle. Increasing projected area, and increases the spray cone angle. ambient pressure decreases the tip penetration and the Increasing injection pressure increases the tip penetra- tion and the projected area, while spray cone angle shows decreasing and then increasing. Nozzle with taper hole can increase the flow coefficient to 0.93 compared with the traditional cylindrical hole. Nozzle with smaller outlet is appreciated to get better atomization on the satisfaction of fuel injection quantity and injection duration.