Experimental study of spray characteristics of liquid jets in supersonic crossflow

Abstract

The spray characteristics of a water jet in Mach 2.85 air crossflow were investigated experimentally using a Phase Doppler Anemometry system. The droplet diameter and velocity of liquid jets with various nozzle diameters were measured and analyzed. Experiments with liquid jets positioned ahead of a cavity were performed to investigate the effects of the cavity on the spray characteristics. It was found that the Sauter Mean Diameter distribution presented a C shape, and the streamwise velocity component presented a mirrored C shape. The Sauter Mean Diameter increased downstream in the upper layer of the liquid jet spray, and this is because large droplets are more prone than small droplets to move from the lower layer to the upper layer of the liquid jet, resulting in a larger Sauter Mean Diameter downstream. A smaller nozzle resulted in an earlier secondary atomization and the final Sauter Mean Diameter had a lower value. A comparison between liquid jets from a plane wall and those positioned ahead of a cavity found an increase in Sauter Mean Diameter near the shear layer of the cavity and a decrease in the streamwise velocity. This mixing process caused an oblique airflow at the outlet of the cavity and changed the distribution of droplets.