Characterization of Carbon Particulates in Diffusion Flames

Abstract

A constrained multispectral transmittance method, where the optical properties of soot are assumed to be known, is used to determine in situ soot size distributions and volume fractions in six solid-, liquid- and gas-fueled diffusion flames. The resulting soot volume fractions range from 0.97×1O^-6 for propane to 1.1×1O^-7 for acetone, and all soot size distributions indicate that the most probable radius is less than O.1μm. In addition, it is found that in the visible region, the relationship between the spectral extinction coefficient k_λ (cm^-1) and the soot volume fraction f_v can be well represented by k_λ=(7.33×10⁴λ^-0.989)f_v, irrespective of the kind of soot. Here, λ denotes the wavelength of radiation in units of μm.