Molecular Weight and Shock-Wave Effects on Transverse Injection in Supersonic Flow

TLDR: In this article, an experimental study of the effects of injectant molecular weight on transverse-jet mixing in a supersonic crossflow was reported, and the effects were strongest when this occurred downstream of, and closest to, the injection port.

Abstract: An experimental study of the effects of injectant molecular weight on transverse-jet mixing in a supersonic crossflow is reported. In addition, the effects of an oblique shock impinging near the injection station were investigated. The examined gaseous injector is circular in geometry and angled downstream at 30 deg to the horizontal. Test conditions involved sonic injection of helium, methane, and air at a jet-to-freestream momentum flux ratio of 2.1 into a nominal Mach 4 air cross stream with average Reynolds number 5.77e + 7 per meter to provide a range of injectant molecular weights from 4―29. Sampling probe measurements were used to determine the local helium and methane concentration. A miniature five-hole pressure probe, pitot and cone-static pressure probes, and a diffuser-thermocouple probe were employed to document the flow. The goals of this effort are twofold. The first goal is to broaden and enrich the database for transverse injection in high-speed flows. Second, these data will aid greatly in the development of advanced turbulence models with a wide range of applicability for high-speed mixing flows. The main experimental results showed that an impinging shock reduces penetration and increases mixing for injectants of all molecular weights. Higher molecular weight injectant seems to increase penetration, but the effect is weak. The effects of shock impingement were strongest when this occurred downstream of, and closest to, the injection port.