Numerical analysis of hysteresis in mode transition of centerline mach reflection in stunted busemann intakes for axisymmetric scramjet engines

Hypersonic air-breathing propulsion, in particular, scramjet (supersonic combustion ramjet) engines, is a promising technology for efficient and economical access-to-space and atmospheric transport. Axisymmetric air intakes based on the Busemann geometry offer appreciable efficiency with maximum total pressure recovery and minimum shock loss, but the inherently long geometry incurs large skin friction drag and structural weight, requiring shortening by some means. Two distinctly different configurations of Mach reflection are found to exist at the centerline for identical inflow conditions and intake lengths in the course of shortening by axial contraction (stunting). Parametric studies with steady and transient numerical simulations are performed to examine the inviscid transient flowfields with variations in the shortening length and freestream Mach number. This paper presents the results and flowfields with focus on the variations of the exit Mach number and temperature as well as intake drag and discusses the hysteresis observed in the stunting and reverse (stretching) process of the Busemann intakes.