Analysis of the two-phase flow in a de laval spray nozzle and exit plume

Abstract

One method used in spray forming and coating technology involves transonic/supersonic gas-droplet two- phase flows through a de Laval nozzle and subsequent subsonic freejet flow from the nozzle to the sprayed surface. To the first- order approximation, this complex phenomenon can be treated in a quasione-dimensional manner to simulate the entire converging- diverging nozzle flow field (with particle injection at the throat) as well as the plume (freejet) region. The basic numerical technique and computer model solve the steady gas field equations through a conservative variable approach and treat the droplet phase in a Lagrangian manner, with full aerodynamic and energetic coupling between the droplets and the transport gas handled via source terms. These analyses are simple and economical to execute. The one- dimensional models are valuable in constructing algorithms for automated process control. Finally, these one- dimensional models give direction to two- and three- dimensional simulations and serve as a test bed for models based on particle dynamics and energetics.