A Computational Study of Unstart in a Dual-Mode Scramjet

By: Logan Riley

Noon – 12:30pm E525

Abstract: Scramjets (Supersonic Combusting Ramjets) are an efficient air-breathing propulsion system for hypersonic (Mach>5) flight. Such high speed operation makes for a challenging flight environment featuring high aerodynamic and thermal loads, unsteady turbulence and shock wave/boundary layer interactions (SBLIs), and short residence times in which to mix and burn fuel. One of the most difficult problems in maintaining controlled scramjet flight is mitigating the potential for unstart of the scramjet engine. Unstart may occur when pressure in the combustor increases as a result of heat release leading to thermal choking. Unstart can lead to increased aerodynamic loads or, in the extreme case, the loss of the vehicle entirely. Since the mechanisms of unstart are not fully understood, we would like to leverage computations to explore the phenomenology of unstart in a scramjet flowpath. For this talk, we will explore unstart in a dual-mode scramjet in the presence of inlet distortion using results from unsteady Reynolds-Averaged Navier-Stokes (RANS) computations based on experimental work performed at the Air Force Research Lab (AFRL).