Stagnation point heat transfer measurements in partially ionized air

Abstract : Experimental measurements of convective stagnation point heat transfer in partially ionized air at stimulated flight velocities up to 55,000 fps are presented. Stagnation point heat transfer rates were measured in an arc-driven shock tube with calorimetric heat transfer gages, either coated with silicon-monoxide films or uncoated. The data are compared to theoretical predictions made with a simple binary diffusion model of partially ionized diatomic gas, nitrogen, whose transport properties were estimated from measured and calculated cross-section data. Stagnation point heat transfer rates calculated from this model for both a frozen and an equilibrium boundary layer, as well as equilibrium boundary layer results from other available calculations using more elaborate models of air, are compared to the data. It is concluded that the transport properties of air up to 15,000 K are known to reasonable accuracy and that heat conduction by electrons does not present a serious engineering problem for flight velocities up to 50,000 fps.