Analysis of the flow interactions between large water droplets and air in droplet acceleration nozzles

The conditions under which large drops, on the order of 150 micron in diameter, are formed from high velocity liquid jets and their subsequent behavior in high velocity airstreams are discussed. The quasi-one dimensional equations for fully coupled two phase turbulent flow of a noncondensable gas with evaporating droplets in a convergent-divergent nozzle are formulated. Droplet performance predictions for the Dust Erosion Tunnel (DET) are reviewed in the light of existing two phase flow test data. Criteria for the aerodynamic design of a droplet acceleration nozzle that would inhibit droplet breakup are developed and used for studying the performance of a droplet acceleration nozzle in the AEDC High Enthalpy Arc Tunnel (HEAT) test facility (H-1) and the DET facility. The conclusion is that although acceleration of large drops without breakup is feasible, many problems will have to be solved to obtain high droplet velocities with large droplets.