Structures of Water Jets in a Mach 1.94 Supersonic Crossflow

The structures of water jets injected into an M=1.94 crossflow were studied experimentally. Two plain orifice nozzles with L/d0 of 20 and orifice diameters of 0.5 and 1.0 mm were tested. Liquid injectors were flush mounted on the bottom plate of the wind tunnel to provide normal injection. Wide ranges of test conditions for jet-to-air momentum flux ratios, aeration levels, and freestream air velocity were tested. A two-component phase Doppler particle analyzer (PDPA) was utilized for the measurement of droplet and spray plume properties along the centerline and across the half plane of spray plumes at various freestream locations. Based on the PDPA measurements, correlations for the penetration heights of pure- and aerated-liquid jets were developed. It was found that once the jet is aerated, the penetration height and cross-sectional area of the spray plume increase dramatically to create a more uniformly distributed spray plume for injected liquid. The atomization processes of pure- and aerated-liquid jets are completed at x/d0<100 at the M=1.94 crossflow, due to the strong action of the supersonic freestream air. The flux- averaged SMD is fairly constant for x/d0≥100 and is on the order of 10 µm for both pure- and aerated-liquid jets. Centerline distribution profiles of droplet and spray plume properties in the freestream direction can be normalized by the penetration height of each spray to obtain universal curves for both pure- and aerated- liquid jets in regions where the liquid atomization process is complete. The normalized distribution profiles for droplet size and x-component droplet velocity exhibit S and mirrored-S shapes, respectively. These S-type distribution profiles are caused by the presence of the bottom floor. These universal curves can potentially be used for the modeling of the far-field structure of liquid jets in supersonic crossflows. NOMENCLATURE