Atomization and Sprays

SPRAY STRUCTURE AND CHARACTERISTICS OF HIGH-PRESSURE GASOLINE INJECTORS FOR DIRECT-INJECTION ENGINE APPLICATIONS

ABSTRACT

This article presents an experimental analysis of spray development, spray tip penetration, and the macroscopic characteristics of a high-pressure gasoline injector for direct-injected gasoline engine applications. Also, this study deals with microscopic characteristics of the fuel spray, such as mean droplet size, mean velocity, and the instantaneous velocity vector fields in the fuel spray of a high-pressure injector. The spray development, spray penetration, and global spray structure were visualized using a shadowgraph technique. Atomization characteristics of the fuel spray such as mean droplet sizes and mean velocities were measured using the phase Doppler particle analyzer system. In addition, instantaneous velocity vector fields of the fuel spray with time after injection were obtained from cross-correlation particle image velocimetry.
The experimental results obtained provide the effect of injection pressure on the spray behaviors, spray structure, microscopic characteristics of the fuel spray, and the velocity vector fields at different moments after the start of injection. The injection pressure of the fuel is an important factor, which has an effect on the spray development processes involving the spray tip penetration, spray width, and mixing of fuel droplets and ambient air. With an increase in fuel injection pressure, the droplet size decreases, and the location of maximum droplet size appears farther downstream than in the case of low injection pressure. The results of spray visualization show that the counterrotating vortex along the outer edge of the spray surface is observed at a later stage of fuel injection, and it continues until right after the end of fuel injection. The velocity vector fields by particle image velocimetry show detailed flow vectors and spray development processes in the fuel sprays at different elapsed times after the start of injection.