Nonluminous Radiation from Hydrocarbon-Air Diffusion Flames

Abstract

Explicit analytical solutions for the radiation from nonluminous regions of hydrocarbon laminar diffusion flames are obtained using a wide band model for nonisothermal, nongray radiation from inhomogcneous mixtures of combustion gases. The spatial distributions of the reactant species, of the combustion products, carbon dioxide and water vapor, and of the temperature in these flames are derived from a one-dimensional model with the Shvab-Zel'dovich assumptions. A wide band, theoretical closed form expression for the total band absorptance of infrared radiating gases, used in conjunction with wide band correlation parameters, allows a simple analytical solution for nongray radiation from nonisothermal and nonuniform distributions of carbon dioxide and water vapor observed in hydrocarbon laminar diffusion flames. The isothermal limit of this solution not only provides good agreement with experimental isothermal emissivity data for carbon dioxide, but also yields the correct functional dependence on temperature, for both carbon dioxide and water vapor. Agreement with absolute water vapor emissivity is reasonable. A tentative soot model to compute soot distribution profiles in diffusion flames is discussed. In the future, the techniques which have been developed here will be applied to soot-containing luminous flames.