Impact of Dilute Multiphase Flow in Supersonic Micronozzles

In this study, a computational investigation of multiphase flow within supersonic micronozzles has been performed in an effort to quantify the impact on thrust production and nozzle efficiency. Motivated by a scenario of incomplete chemical decomposition within a miniaturized, microfabricated monopropellant micropropulsion system, the multiphase flow is modeled over a range of throat Reynolds numbers (160≤Ret≤780) to consist of liquid droplets ranging in size from 0.1 to 3.0 μm in diameter (Stokes numbers 0.01–10.0) and with mass loadings up to 100% relative to the gas phase. The results indicate that the presence of liquid droplets within the supersonic gas flow can substantially degrade micronozzle performance with thrust reductions approaching 19% and specific impulse reductions of up to 35% possible for sub-micrometer-scale droplets at Ret=780 and a mass loading of 100%.