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A compact three-dimensional scramjet intake with a high compression ratio and a movable cowl as a starting device and for the adaption of the internal contraction to respective operating conditions...

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.

In this paper, an extensive investigation of the separation process of the first two stages of a carrier rocket that employs solid rocket motors for the lower stage is presented. As the reference vehicle, the VEGA rocket is used. The effect of the plumes of first-stage retrorockets on upper-stage aerodynamics and aerothermal loads is analyzed by means of wind-tunnel testing in the hypersonic wind tunnel H2K of DLR, German Aerospace Center. Aerodynamic coefficients are determined by force measurements. In addition, pressure distributions on the upper-stage surface and schlieren images for flow visualization are recorded. Infrared thermography measurements are conducted to determine the effect on aerothermal loads. Different flow conditions are achieved by variation of Reynolds number, retrorocket injection pressure ratio, and angle of attack. Results showed extensive flow separation around almost the entire upper stage by the retrorocket plumes already at low injection pressure ratios. During angle-of-attack sweeps, sudden changes in the flow structure occurred accompanied by strong changes in aerodynamic forces at values of α≈±2 deg. This behavior was found to be influenced by hysteresis effects.

This paper presents the numerical simulations and the performance analysis of a scramjet inlet as part of a combined experimental and numerical study. A well-validated finite volume flow solver was used to simulate a scramjet inlet with a double ramp configuration for outer compression, including varying degrees of sidewall compression. The computed wall pressure and heat transfer in the symmetry plane are in close agreement with the measurements, and the numerical results indicate that the weak sidewall compression alters the inlet performance significantly. The effects of partial relaminarization over the expansion corner, before the interior part of the inlet, is isolated and investigated in both the experiment and simulation. It is shown that relaminarization of a boundary layer is predicted accurately using the current numerical methods. This work represents a contribution to the understanding of the effects of sidewall compression and relaminarization in designing a scramjet inlet.

In this paper we report on an extensive investigation of the separation process of the first two stages of a carrier rocket corresponding to VEGA, which employs solid rocket motors. The effect of the plume of first stage retro rockets on upper stage aerodynamics and aerothermal loads is analysed mostly by means of windtunnel testing in the hypersonic windtunnel H2K of DLR Cologne. Aerodynamic coefficients are determined by force measurements. In addition pressure distributions on the upper stage surface and Schlieren images for flow visualization are recorded. Infrared thermography measurements are conducted to determine the effect on aerothermal loads. Different flow conditions are achieved by variation of Reynolds number, retro rocket injection pressure ratio and angle of attack.

We conducted an extensive experimental examination of the operational behavior of a three-dimensional scramjet inlet featuring a movable cowl to adapt the internal contraction according to the respective operation conditions. The experiments were conducted in the H2K wind tunnel of the DLR Cologne at Mach 7. The parameters investigated include different flight path angles (both angle of attack and angle of yaw), internal contraction ratio and Reynolds number. The critical internal contraction for inlet starting was found to agree well with common relations for starting of 3D-inlets. With increasing internal contraction, the inlet performance was found to improve and the inlet operated more stable. It was successfully tested for angles of attack up to ± 6° and angles of yaw up to 6°. Reynolds-Number had rather small effects on the performance and starting behavior of the inlet. Infraredthermography also gave some insight into the flow structure in the external part of the inlet.

In this paper, we present the results of an extensive measurement campaign to investigate the effect of external and internal sidewall compression as well as different contraction ratios on the performance of the flowfield of a scramjet inlet. Experiments were conducted in the H2K windtunnel of the DLR Cologne. The results show that external sidewall compression induces strong separation and vortex structures in the external part which impair the starting behaviour and inhibit any gains of the compression ratio. With internal sidewall compression, strong increases of the pressure ratio could be achieved and the inlet still started at internal contraction ratios well above the Kantrowitz-Limit.

This paper presents the numerical simulations and performance analysis of a 3D scramjet inlet with focus on the effects of sidewall compression and relaminarization. A well-validated �finite volume flow solver was used to simulate a scramjet inlet with a double ramp configuration for outer compression and varying degrees of sidewall compression. The computed wall pressure and heat transfer in the symmetry plane are in close agreement with the measurements and numerical results indicate that sidewall compression alters the inlet performance significantly. The effects of relaminarization over the expansion corner prior to the interior part of the inlet is isolated and studied in both experiment and simulation.