Studies of the Compositional and Temperature Effects on the Optical Properties of Flame Soot

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Abstract Charalampopoulos 9528598 The objectives of the proposed research is to study the effects of chemical composition, temperature and/or microstructure on the refractive indices of soot. The proposed studies involve both ex-situ and in-situ measurements. In the ex-situ studies particles will be collected from premixed propane/oxygen and acetylene/oxygen flames and formed into smooth pellets. These pellets will be analyzed for their carbon/hydrogen ratios and from ellipsometric measurements their refractive indices will be determined in the wavelength range 0.30 - 10 mm and for the temperature range 25 to 2500C. By correcting for voidage effects, the refractive indices of the particles which constitute the pellet surfaces will be determined. In-situ studies on the same flames, consisting of scattering, extinction and polarization measurements, will be used to obtain particle diameters, number of primary particles/agglomerate, number of agglomerates and the refractive indices of the primary particles. Aggregates of known configuration and refractive indices will be added to a CO/Air diffusion flame in order to test the experimental and data inversion approaches. Through this investigation the PI hopes to be able to account for the non-sphericity of the soot particles, test the methodology of the in-situ studies using straight-chain agglomerates, compare refractive indices obtained by the in-situ and ex-situ methods, and identify the critical parameters in determining soot refractive indices.