Shock-tube studies of equilibrium air radiation

Abstract

The results of an experimental investigation of equilibrium air radiation in the wavelength region of 0.17 to 6.0 ju are presented. The data were obtained using a thin-film heat-transfer gage to measure the stagnation-point, equilibrium radiative heat-transfer rate on hemispherical models mounted in an arc-driven, shock-tube facility. Stagnation conditions corresponding to flight velocities between 26,000 and 52,000 fps and altitudes from 100,000 to 170,000 ft were simulated. The results are compared with existing theoretical calculations, and reasonable agreement is shown to exist. Recent measurements of radiative heat transfer at wavelengths down to 1200 A are also discussed. Nomenclature Et = total radiant energy emission per unit volume and unit time FI = shock-layer shape correction factor F2 = thin-film gage geometric view factor I = thin-film gage current / = radiance M = Mach number p = pressure q = heat-transfer rate RN = nose radius of hemispherical body T = transmissivity; temperature t = time V = velocity Vs — incident normal shock velocity aG = absorptivity of thin-film gage 5 = shock-detachment distance X = wavelength of radiation p = gas density po = atmospheric density at standard conditions = 1.293 X 10-3 g/cm3 Subscripts