Determination of number density, size and morphology of aggregates in coflow diffusion flames using light scattering and local sampling

Number density, size, and morphology of silica aggregate particles in coflow diffusion flames have been determined experimentally using a novel method combining light scattering and local sampling techniques. The number density and volume fraction of both aggregates and spherical particles have been calculated from the scattering cross section measured from 90 degrees light scattering with the combination of determining particle size and morphology from the localized sampling and TEM image analysis. Rayleigh-Debye-Gans and Mie theories have been applied to the calculations for fractal aggregates and spherical particles, respectively. Of particular interests are the effects of carrier gas flow rates, different carrier gases, and flame temperatures on the growth of silica particles and the roles of radial heat and H2O diffusion have been studied when using N-2 or O-2 as a carrier gas. (C) 2000 Elsevier Science Ltd. All rights reserved.