Numerical Simulation of a Real Shcramjet Flowfield

Abstract

A shock-induced combustion ramjet (shcramjet) geometry is considered wherein the fuel, gaseous hydrogen, is injected in a two-oblique shock external compression inlet via cantilevered ramp injectors and a wall slot. The combustible mixture formed at the exit of the inlet is then ignited through the shock generated by the cowl of the engine. The numerical simulation of the three-dimensional flowfield of a shcramjet flying at M = 11 and at an altitude of 35 km was performed using the WARP code, in which multispecies Favre-averaged Navier-Stokes equations are closed by the k-w turbulence model and the Wilcox dilational dissipation correction, to account for compressibility effects at high turbulence Mach numbers. The hydrogen/air chemical reactions are modeled by Jachimowsky's nine species, 20 reaction model. It has been found that the combustor length resulting from the shock-induced process is of the order of 25-30% of the inlet length. The relatively low value of the fuel specific impulse obtained, 573 s, is mainly due to incomplete mixing achieved in the adopted inlet model. To the authors' knowledge, the paper contains the first ever proof, in the open scientific literature, of the feasibility of this hypersonic propulsion concept in realistic flow situations, by numerical simulation.