Effects of Droplet Behaviors on Fuel Adhesion of Flat Wall Impinging Spray Injected by a DISI Injector

Owing to the short impingement distance and high injection pressure, it is difficult to avoid the fuel spray impingement on the combustion cylinder wall and piston head in Direct Injection Spark Ignition (DISI) engine, which is a possible source of hydrocarbons and soot emission. For better understanding of the mechanisms behind the spray-wall impingement, the fuel spray and adhesion on a flat wall using a mini-sac injector with a single-hole was examined. The microscopic characteristics of impinging spray were investigated through Particle Image Analysis (PIA). The droplet size and velocity were compared before impingement. The adhered fuel on the wall was measured by Refractive Index Matching (RIM). The fuel adhesion mass and area were discussed. Moreover, the relationships between droplets behaviors and fuel adhesion on the wall were discussed. The droplets impingement models were compared in order to find the key factor which dominates the fuel adhesion during the spray-wall interaction. Results show that only one dry wall model of droplet impingement can separate the spray-wall impinging behaviors. However, the wet wall impingement models work well for the spray-wall impinging behaviors.