Kyungrae Kang , Lydia Wermer , Jong Ho Choi , Seung Jin Song , Seong-kyun Im and Hyungrok Do
DOI Number XXX-YYY-ZZZ
Conference Number HiSST 2018-903
Shock-compressed flows in a model scramjet isolator were visualized using a high-speed schlieren imaging system to reveal unstarting and boundary layer suction-controlled flow behaviors. The model scramjet having a rectangular cross-section and contraction ratio of 4 at the inlet was tested in Mach 6 freestream flows. Inlet unstart, seen as flow spillage at the inlet caused by downstream flow choking, was triggered by high-pressure nitrogen jet injection after the isolator that simulates excessive heat release and resulting pressure rise in the combustor. Transient movements of an upstream-propagating shockwave, referred to as the unstart shock, and its fluctuation behavior upstream of the inlet are temporally resolved. Boundary layer suction was applied in the isolator wall removing a small portion (~2%) of the isolator flow from the boundary layer when activated. It is shown that the unstart shock, which completes the unstart process when arriving at the inlet, can be held or decelerated in the isolator depending on the suction activation time: early activation can stop while late activation can delay the unstart.