The structures of spray plumes from 0.5-mm waterjets injected into a subsonic crosse ow were experimentally investigated using phase Doppler particle anemometry. Droplet size, axial velocity, and volume e ux 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 e ux ratios and in which the momentum exchange between column waves and the airstream is signie cant. For cases with large-momentum e ux 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 e ux locations, an indicator of the location of the highest concentration of droplets, was measured and correlated with momentum e ux ratios and axial distances. It was found that more droplets are distributed toward the upper portion of the spray plume for larger momentum e ux ratios. Spray penetration, spray width, penetration-to-width ratio, and spray cross-sectional area were also found to increase with the momentum e ux ratio.
Read full abstract