A REVIEW OF FUEL PRE-INJECTION IN SUPERSONIC,CHEMICALLY REACTING FLOWS

Developing anefficient, supersonic combustion-based, air breathing propulsioncycle operating above Mach 3.5, especially when conventionalhydrocarbon fuels are sought and particularly when liquid fuelsare preferred to increase density, requires mostly effectivemechanisms to improve mixing efficiency. One way to extend thetime available for mixing is to inject part of the fuel upstreamof the vehicle's combustion chamber Injection from the wallremains one of the most challenging problems in supersonicaerodynamics, including the requirement to minimize impulselosses, improve fuel-air mixing, reduce inlet/combustorinteractions, and promote flame stability. This article presents areview of studies involving liquid and, in selected cases, gaseousfuel injected in supersonic inlets or in combustor's insulators.In all these studies, the fuel was injected from a wall in a wakeof thin swept pylons at low dynamic pressure ratios ($q_{\rm{jet}}$/$q_{\rm {air}}$ =0.6$\sim$1.5), including individualpylon/injector geometries and combinations in the inlet andcombustor's isolator, a variety of injection conditions, differentinjectants, and evaluated their effects on fuel plume spray,impulse losses, and mixing efficiency. This review article cites46 references.