Infrared Radiation of Flames

Knowledge of the infrared spectral radiance of combustion flames is needed in various military applications of infrared techniques. In an effort to fill this need, infrared spectral emittance and absorptance of flames were studied at various temperatures and for a variety of fuel-oxidizer combinations. Spectral emissivities were measured in the region 1 - 15-microns, as functions of fuel composition, flame temperature, and mixture ratio. Flame temperatures were determined from the infrared emission and absorption spectra, for various wavelengths. Methods of extrapolating flame radiance from laboratory to field conditions were investigated. For this purpose, the measurements of infrared flame spectra were correlated with concurrent analyses of molecular population distributions, transition probabilities, and spectral line shape and line width. A sample extrapolation was verified experimentally for a hydrogen-oxygen rocket engine, operating under simulated altitude conditions. Sponsored in part by DARPA.