Investigation of two-dimensional scramiet inlet flowfield at Mach 7

A measurement campaign has been carried out to investigate the viscous flow effects in a fixed geometry two-dimensional scramjet inlet at Mach 7. The tests have been performed in a hypersonic blowdown wind-tunnel facility. The existing boundary layer separation due to shock interaction in the inlet throat can lead to inlet unstart. Therefore, an optional passive boundary layer bleed has been integrated at the throat. The passive bleed reduces the lip shock induced separation bubble in the throat significantly. The obtained experimental wall pressure distribution and pitot pressure profiles are discussed and compared to 2-D and 3-D computational fluid dynamics calculations. To investigate the compression behavior, different backpressure ratios have been applied to the isolator flow and the effects on the internal flow structure are analyzed by means of shadowgraph pictures, static pressure distribution, and pilot pressure profiles at the exit of the isolator. The heat transfer coefficient to the inner side wall of the isolator is calculated using the time-dependent surface temperature, measured with an infrared system. The resulting 2-D Stanton number distributions are presented for different configurations and different backpressure ratios. In addition, three different Reynolds numbers have been used to investigate the effect on the separation bubble located in the corner of the first and second ramp transitions and the resulting change in ramp heat flux.