Radiation from flames in furnaces

Theoretical and experimental research on the radiative transport from flames in furnaces is reviewed. A “flow chart” of the procedure of solving a radiative transfer problem is presented. Banded and continuous emission in furnace flames is considered. Emission from particulate clouds is discussed in three groups according to the value of the Mie parameter X=πd/λ: for X≪1 (soot in flames) where scattering is negligible, and calculated and measured optical constants are available, for X≈1 (cenospheres in flames) where scattering by individual particles is taken into account, and for X≫1 (pulverized coal flames) where the scattering is multiple and anisotropic. Simplified furnace calculations: the well-stirred and the plug-flow furnace models and the zone method of analysis are discussed, together with approximate methods for the solutions of the transport equation when allowance has to be made for multiple scattering. The experimental information surveyed is presented in two groups: o (a) Radiometric measurements on industrial size flames, and (b) Physical measurements of radiative properties of absorbing-emitting-scattering media. The experimental research reviewed includes data of radiant emittance and emissivity of flames as a function of design and operational input variables obtained at IJmuiden and discussions on the correlation of values of absorption coefficients determined from flame measurements with results of theoretical studies. Further research is required on methods of predicting temperatures, gas-, and soot-concentration distributions in flames from input parameters; on the radiative properties of soots at flame temperatures, and of scattering characteristics of particles that are large compared with the wavelength of the incident radiation. Approximate methods for the solution of the transport equation for scattering media need checking experimentally.