EFFECTS OF SOOT AGGLOMERATION ON RADIATIVE-TRANSFER

A detailed analysis is presented of soot-particle agglomeration for a premixed flame with a fuel equivalence ratio of phi-0 = 1.8. Measured scattering and extinction coefficients and dissymmetry ratios at 0.488-mu-m are combined with a scattering and extinction model for agglomerates to estimate each of the following: primary particle diameter, number density of primary particles and the total number of agglomerates as a function of position in the flame. The inferred primary particle diameters vary in the range from 0.009 to 0.029-mu-m, whereas the number of primary particles per agglomerate varies from 11 to 24. The inferred agglomerate parameters, along with the measured spectral emissivities in the wavelength range 0.4-6.7-mu-m and the known refractive indices of soot, are combined to yield the spectral and total emissivities of soot. Comparisons are carried out with the results of previous investigations. It is shown that for the type of flame studied, for which the degree of agglomeration is low, the governing parameter in soot radiation is the refractive index.