An experimental investigation of turbulent slot injection at Mach 6

Abstract

The use of film cooling for protecting a surface exposed to high temperature air at hypersonic speeds is investigated experimentally. The tests were conducted in a Mach 6 contoured axisymmetric nozzle with a streamlined centerbody. The Reynolds number in the test section was in the range of 1-3.6 X 10 6/in.; and a wall to freestream temperature ratio of 0.635. Heat-transfer distributions downstream of the slot were obtained for various mass flow rates and the effect of injection on the velocity, temperature and Mach number profiles was studied. Correlations for the cooling lengths with the blowing rate parameters X = pjUj/peUe for the various coolants-—air, helium, hydrogen, and argon were obtained. Correlations for the heattransfer rates in the form (1 — q/go.») an<l for the effectiveness [e = (Taw. — T0oo)/(T0j — T0oo)] of the adiabatic wall temperatures were obtained as a function of X and x/S (distance from the slot/slot width) for each of the injected coolant gases. The adiabatic wall temperatures are not a basic result of the measurements, but have been inferred from the heat transfer measured, using a local flat plate equation for the same wall temperature. Skin-friction coefficients were also obtained from the measured profiles. Finally the results of this study are compared with available results in the literature.