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

In this paper, we present the results of an extensive measurement campaign to investigate the effects of external and internal sidewall compression and variation of internal contraction on the performance and flowfield of a SCRamjet-inlet. Experiments were conducted in the H2K windtunnel of DLR Cologne at Mach 7. The performance was evaluated by static and total pressure ratios, kinetic energy efficiency and mass capture ratios. The flowfield was analysed 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 behaviour. 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 pres-sure 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