A Multispectral Transmittance Method for Simultaneous Determination of Size Distribution and Optical Dispersion Parameters of in situ Soot

Abstract

An analytical procedure is proposed to simultaneously determine the size distribution and optical dispersion parameters of soot from multispectral transmittance data for a luminous flame. Blokh's distribution and a gamma distribution are assumed as particle size laws, but only Blokh's distribution is successfully utilized throughout the study. The dispersion model of three bound and one free electrons developed by the author is adopted to describe the complex refractive index of soot. Of the dispersion parameters, only the effective free electron number density is treated as an adjustable parameter for each soot and the remaining parameters are fixed at adequate values. The proposed method is applied to Lee-Yu-Tien's data of spectral extinction coefficients of small-pool diffusion flames of six fuels. It was found that the most probable radius of in situ soot particles is less than 0.1 μm for luminous flames examined here and that the relationship between the effective free electron number density and the fuel H/C ratio is well represented by an expression derived from our previous formula.