Investigation of soot oxidation by coupling LII, SAXS and scattering measurements

This work presents an in-situ characterization of the oxidation of soot particles in flames by coupling three different techniques. Small Angle X-ray Scattering and Static Light Scattering were used in order to provide information on the size of the primary spheres and the aggregates respectively. Laser Induced Incandescence was also used to determine the soot volume fraction in the flame. Flame temperatures and soot residence time were also determined. These techniques were combined to provide a complete description of the impact of the oxidation process on soot aggregates (aggregate and primary sphere densities, size distributions). In order to limit the phenomena to oxidation, soot was generated upstream by a miniCAST generator and injected into a non-sooting flame. Amongst other results, it is shown that primary sphere diameter reduction is accompanied by an increase of the geometric standard deviation. This effect can be modeled by considering the transition from a volume (diffusion) to a surface (reaction) oxidation process.