直喷汽油机压电晶体控制外开轴针式喷油器的喷雾场粒子特性

摘要

应用相位多普勒测量技术(PDA)对压电晶体控制的外开轴针式喷油器的喷雾场内粒子速度及直径大小进行测量与分析.结果表明,常压条件下,喷雾路径上的粒子速度和粒径都要明显大于喷雾外侧相邻的测量点.环境压力变化影响了气体回流进入喷雾内部的位置,从而使Z=16mm上的所有测点在两个背压条件下得到了速度方向完全相反的结果.喷油结束后,气体回流不仅使喷雾内部的粒子具有较高的速度,也使喷雾内部的粒子平均粒径明显大于喷雾外侧的粒子平均粒径.采用时间分割法将喷雾划分为4个区域进行分开比较.在喷射过程中,喷雾前端粒子速度较高,粒径较大,但随着喷油结束,喷雾场内的粒子速度接近于零,粒子算数平均直径(AMD)和索特平均直径(SMD)也分别达到了稳定水平.%Droplet velocity and size characteristics of conical the spray injected through the piezo pintle-type injectors are measured and analyzed by means of phase doppler anemometry (PDA). Experimental results indicate that the droplet velocity and size on the path of spray are much higher than those on the outer adjacent measuring point under atmospheric pressure condition. The rise of ambient pressure affects the air backfiow position which gives the opposite direction velocity at Z = 16 mm position under two different ambient pressures. Air backfiow not only improves droplet velocity inside the spray, but also droplet SMD, compared with those outside the spray. Time dividing method is used to divide the droplets into four parts for the study. Result shows that the leading edge of spray contains many droplets with high velocity and large size. However, AMD and SMD of droplets in the spray field remain at a stable level when droplet velocity approaches zero after fuel injection.