Experimental Investigation of Sidewall Compression and Internal Contraction in a Scramjet Inlet

Abstract

In this paper, we present the results of an extensive measurement campaign to investigate the effects of external and internal sidewall compression and the variation of internal contraction on the performance and flowfield of a scramjet inlet. Experiments were conducted in the H2K wind tunnel of DLR, German Aerospace Center, in Cologne, Germany, at Mach 7. The performance was evaluated by static and total pressure ratios, kinetic energy efficiency, and mass capture ratios. The flowfield was analyzed using wall pressure distributions, pitot pressure, and Mach number profiles at the isolator interface to the combustion chamber and infrared thermography on the external ramps. The results show that the combination of a two-ramp inlet with external sidewall compression is not suitable for increasing the inlet’s compression capability as it induces strong separation and vortex structures in the external part, which strongly increase spillage and impair the starting behavior. Thus, no significant increases in internal contraction are possible, which inhibits any gains in the performance of the inlet. With internal sidewall compression, strong increases of the pressure ratio can be achieved at the cost of total pressure losses. With internal sidewall compression as well as without sidewall compression, the inlet is still self-starting at internal contraction ratios well above the Kantrowitz limit.