Characterization of the spray atomization process of a multi-hole gasoline direct injector based on measurements using a phase Doppler particle analyser

Abstract

The main objective of this experimental study was to investigate the spray atomization process of a multi-hole gasoline direct injector by characterizing the basic process of single-jet atomization as well as complex phenomena such as air entrainment and jet interactions. We measured the droplet size and velocity using a phase Doppler particle analysis system at different measurement distances and different injection pressures in both the parallel direction and the orthogonal direction with respect to spray propagation. In addition, we calculated the Weber numbers to characterize further the spray atomization process. Our experimental results showed that the droplet velocities followed similar trends for different measurement distances but that the peak value decreased as the distance increased. Furthermore, a leading edge of the spray was observed at the initial stage of injection but disappeared as the measurement distance increased. Based on the droplet diameter distribution, we confirmed that increasing the distance and air entrainment had effects on the jet atomization process. Air entrainment was seen at the edges of both sides of the jet when the droplet diameter was less than 23 µm and the droplet was travelling at a low velocity, and the spray atomization process was more activated under air entrainment conditions. A comparison of different injection pressures confirmed that the injection pressure plays an important role in droplet break-up.