Numerically Simulated Comparative Performance of a Scramjet and Shcramjet at Mach 11

The aeropropulsive performance characteristics of a scramjet and a shock-induced combustion ramjet (shcramjet) are compared at a flight Mach number of 11 and an altitude of 34.5 km. The vehicles share the same inlet type, fuel injection system, fuel/air equivalence ratio, mixing/combustor duct, methodology of nozzle design, and gridding technique. The numerical simulation of the three-dimensional vehicle flowfields from tip to tail are performed by the window allocatable resolver for propulsion code, in which the multispecies Favre-averaged Navier-Stokes equations are closed by the Wilcox k-omega turbulence model. Combustion is simulated by the H(2)-air chemical kinetics model of Jachimowski. Magnitudes of the thrust, fuel-specific impulse, pressure, and frictional forces acting on the vehicles are determined. Results show that the scramjet outperforms the shcramjet with a fuel-specific impulse of 1450 s as opposed to 1109 s developed by the shcramjet. However, the shcramjet is appreciably smaller and thus lighter than the scramjet with a combustor length which is one-fifth of the scramjet combustor length, requiring much less cooling.