高压喷雾碰壁的粒度特性研究

Droplet Size Characteristics of Wall Impinging Diesel Fuel Spray at High Injection Pressure

作者采用基于激光衍射原理的Malvern粒径测试仪,在可模拟压缩上止点密度条件下,研究了柴油机泵-管-嘴供油系统下2种孔径喷嘴,在高压喷射近距离垂直碰壁时的粒度和浓度分布特性,对冷壁与热壁的影响作了对比。结果表明,冷碰壁喷雾的特点是燃油碰壁后大量附着壁面,且小孔径时壁面油雾层的浓度及SMD值较小;热碰壁喷雾的显著特点是,高温壁面对油束碰壁后的燃油有“热反溅”作用,小孔径油束碰壁后油滴蒸发及气化的速率远高于大孔径,对燃油蒸发及气化最佳的壁面温度在573K附近。

This paper describes the characteristics of droplet size and concentration distribution of diesel spray with wall impingement at high injection pressure. Two nozzles with different hole diameters in a fuel supply system that consists of pump-pipe-nozzle have been researched. The experiment is carried out under the condition that the air density is similar to the state in the engine cylinder. The spray impinges on a flat plate vertically. The temperature of the plate surface is variable. The droplet size is measured by a Malvern Particle Sizer based on the principle of Laser diffraction. When the spray impinges on a room-temperature wall, much of fuel will accumulate on the wall surface. While in the space over the wall, the smaller the nozzle hole, the smaller the SMD and the droplet density. When the wall temperature is high enough, the droplet of the impinging spray will be rebounded and evaporated. The optimum surface temperature for rebounding and evaporat- ing is about 573K.