Mixing and flame holding with air inlet configuration in scramjet combustor

A parametric study of combustor inlet configuration for Supersonic Combustion Ramjet (SCRAMJET) Engine has been conducted by solving Two-Dimensional full Navier-Stokes equations. The main stream is air of Mach 5 entering through the configured inlet of the combustor and gaseous hydrogen is injected from the side wall at sonic condition. The parameters that include are the air inlet width and stream angle with a backward facing step under the inlet port. On the effect of inlet width variation, two competing phenomena have been observed: (i) in upstream of injector the strength of recirculation is higher for wider inlet and consequently the mixing increases and (ii) in downstream, the diffusion of hydrogen decreases with the increase of inlet width and eventually mixing decreases. As a result, in far downstream the mixing efficiency increases up to certain inlet width and then decreases for further increment of inlet width. During the variation of air stream angle, strong interaction between main and injecting flows can be observed for small angle causing sharp increase in mixing efficiency on the top of injector. Due to high momentum of air stream towards the side wall, no recirculation occurs at the upstream of injector for small angle and the system becomes unable for flame holding. Among the cases considered, the configuration of moderate air stream angle shows higher mixing efficiency and good flame holding capability.