Droplet characteristics in spray field of an outward-opening pintle-type injector actuated by piezo for DI gasoline engines

Droplet velocity and size characteristics of conical the spray injected through the piezo pintletype 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 backflow position which gives the opposite direction velocity at Z=16, mm position under two different ambient pressures. Air backflow 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.