Spray structures of liquid jets atomized in subsonic crossflows

The structures of spray plumes from 0.5-mm waterjets injected into a subsonic crossflow were experimentally investigated using phase Doppler particle anemometry. Droplet size, axial velocity, and volume flux were measured across the spray plume at several axial distances downstream of the injector exit. Results indicate that large droplets can be found in the central portion of the spray plume for cases with small liquid/air momentum flux ratios and in which the momentum exchange between column waves and the airstream is significant. For cases with large-momentum flux ratios, the droplet size distribution exhibits a concave-layered structure, with the peak on the centerline and large droplets at the top. Droplets were found to concentrate in a small area within the spray plume, which indicates that the liquid mass distribution is not uniform. The height of the maximum volume flux locations, an indicator of the location of the highest concentration of droplets, was measured and correlated with momentum flux ratios and axial distances. It was found that more droplets are distributed toward the upper portion of the spray plume for larger momentum flux ratios. Spray penetration, spray width, penetration-to-width ratio, and spray cross-sectional area were also found to increase with the momentum flux ratio.