Structure of the laminar ablating air-Teflon boundary layer

Abstract

Abstract : Radiation profiles in an ablating flat plate air-teflon laminar boundary layer were studied both experimentally and theoretically. The experiments were conducted in a one atmosphere, 3000 - 6000K, subsonic free stream produced by an arc jet. Spatially resolved radiation profiles within the boundary layer were obtained in both the visible and infrared. The major radiation in the visible and near ultraviolet wavelengths was the CN violet. In the infrared, the major radiators were CO, CO2, NO and COF2. The theory which was developed to predict the structure included coupling of the heat and mass transfer at the Teflon surface. A 'partial equilibrium' model for the teflon-air chemistry was utilized, which does not allow the formation of CF3 and CF4 within the boundary layer. For the selected wavelengths in the infrared the theory generally predicted quite well both the spatial location and magnitude of the peak radiation, and also predicted the integrated radiation across the layer to within a factor of two. For the selected wavelength in the visible, the radiation intensity, which comes from CN, is much larger than predicted, indicating that the CN is not in thermodynamic equilibrium. (Author)