In the ram/scramjet engines, transition of the combustion mode from subsonic one to supersonic one is very important in their performance and operation. The subsonic mode combustion occurs behind a pseudo-shock wave (PSW) in a isolator, while the PSW disappears in the supersonic mode. The mode transition sometimes shows hysteresis feature caused by strong interaction among shock waves, mixing and combustion. It is necessary to understand the mechanism of this interaction for prediction of the scramjet engine performance. In our previous study, the PSW was produced by mechanically controlling back pressure of a duct, and its effect on the mixing was investigated. In the present study, the PSW was produced by hot gas injection from a N2 or H2/N2 plasma torch in a Mach 2.3 airstream. The distributions of gas composition, pitot pressure, and stagnation temperature at the exit of the test section as well as the wall pressure distribution were measured to investigate the mechanism of PSW formation by heat addition and its influence to the mixing.
