Extinction and scattering properties at wavelengths of 250-5200 nm were studied for soot emitted from large buoyant turbulent diffusion flames where soot properties are independent of position in the overfire region and characteristic flame residence time. Flames burning in still air and fueled with both gas (acetylene, ethylene, propane and proylene) and liquid (benzene, toluene, cyclohexane and n-heptane) hydrocarbon fuels were considered. Measuring scattering patterns and ratios of total scattering/absorption cross sections were in good agreement with predictions based on the Rayleigh-Debye-Gans (RDG) scattering approximations in the visible. Measured depolarization ratios were correlated byprimary particle size parameter, completing RDG methodology needed to make soot scattering predictions. measurments of dimensionless extinction coefficients were in good agreement with earlier measurements for similar soot populations and were independent of fuel type and wavelength except for reduced values as the near ultraviolet was approached. The ratios of the scattering/absorption refractive index functions were independent of fuel type and were in good agreement with earlier measurements. The refractive index function for absorption was similarly independent of fuel type but was larger than earlier reflectrometry measurements in the infrared. Ratios of total scattering/abosption cross sections were relatively large in the visible and near infrared, with maximum values of 0.4-0.9 suggesting greater potential for scattering from soot particles to affect flame radiation properties than previously thought.
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