Film Cooling Effectiveness in High Enthalpy Flows

An experimental study has been conducted to investigate the effectiveness of film cooling in hypersonic, high-enthalpy flows. Both air and nitrogen are used for a test gas and a coolant gas is helium. Injection mass fluxes are varied by changing total pressure of the coolant gas. The half-surface of a flat plate model with a blunt nose is coated with the thin film of silicon dioxide to obtain the dependence of heat fluxes by catalytic recombination effects. Heat fluxes are calculated by surface temperatures measured by coaxial thermocouples. In the case of dissociated air free stream, catalytic effects are observed in our wind tunnel. Experimental results show that thermal protection by film cooling is effective in chemically reactive flows. Non-dimensional heat fluxes and cooling lengths in the dissociated free stream are at the same level as in the nitrogen flows. With film cooling, heat fluxes on the non-coated surface are nearly as same as coated surface regardless of the wall catalysis.