Experiments on nitrogen and hydrogen transpiration cooling in a model scramjet combustor

Transpiration cooling systems are a promising approach to handle the high wall temperatures and heat loads generated in supersonic combustion ramjets (scramjets). The German Aerospace Center DLR has conducted experiments to investigate the applicability of transpiration cooling systems in scramjets and the phenomena resulting out of the interaction between a wedge/flame holder and coolant secondary flow. Results with hydrogen as coolant for different sintered porous materials, different blowing ratios and different boundary conditions with and without wedge are shown. The results are compared with previously gained results with nitrogen as inert coolant. A detailed analysis using optical Schlieren and Background Oriented Schlieren (BOS) investigations is presented. Phenomena like choking, shock-boundary layer interaction, coolant boundary layer separation and hydrogen self-ignition caused by shock-boundary layer interaction are addressed. Further research is discussed and concretized.