Microscopic level study on the spray impingement process and characteristics

Abstract

Spray impingement adversely affects fuel mixture preparation, combustion performance and emissions and more studies are required to understand this process. The isooctane spray impingement process and characteristics were investigated by ultrahigh speed imaging technique with the employment of highly spatially resolved long distance microscope. The effects of impact surface temperature were also studied. It was found that during the initial stage and steady stage of spray impingement, a large proportion of droplets splashed due to high velocity. The droplet size after impingement generally reduced because of the strong collision. For the end stage of impingement, droplets tended to stick on the impact surface and float on the fuel film due to the low droplet velocity and the existence of built liquid fuel film. It was also found that hot impact surface could only improve the impingement and reduced the film building-up rate in the initial stage. The steady stage and end stage of spray impingement were less affected by the variation in impact surface temperature.