Numerical investigation of axisymmetric intake flowfield and performance for scramjet-powered ascent flight

Air intakes play a crucial role in the operation of scramjet engines, one of the most promising hypersonic airbreathing propulsion technologies for efficient and flexible space transportation, it is thus essential to accurately understand and predict the flowfields for high-performance intake design, especially in varying operating conditions. Axisymmetric intake flowfields are investigated numerically assuming a typical scramjet operation on a constant dynamic pressure ascent trajectory, aiming to achieve scramjet-powered access-to-space. Physical insight into scramjet flowfields at various flight altitudes and Mach numbers have been gained by means of high-resolution simulation to resolve the viscous flowfields. High levels of adaptive mesh refinement have identified detailed flow phenomena including shock reflection, interactions, and boundary layer as well as their aerodynamic and aerothermal effects on pressure and temperature fields. In particular, Mach reflection characterized by a Mach disk has been found to occur at the centerline, even in the operating conditions where regular reflection would result from computational simulation without mesh adaption. The intake performance has been evaluated with respect to the compression efficiency, drag, and exit temperature. The intake drag has been found to decrease at higher Mach numbers at higher altitudes on a constant dynamic pressure trajectory during acceleration due to reduced pressure drag while viscous drag varies little. Rather little influence of varying wall conditions has been observed on the intake drag between the isothermal and adiabatic wall conditions due to counteracting behavior between viscous and pressure drag components.