Informing TiRe-LII assumptions for soot nanostructure and optical properties for estimation of soot primary particle diameter

Abstract

Time-resolved laser-induced incandescence for primary particle size determination is tested using three model carbon blacks. Optical properties change as does the nanostructure upon laser annealing, whereas aggregate morphology and primary particle size remain equivalent to the original material, as shown by transmission electron microscopy (TEM). Primary particle diameters found from fitting experimentally measured time-resolved laser-induced incandescence (LII) signals with existing models do not match the particle diameters as directly visualized by TEM. The accommodation coefficient is shown to be a crucial parameter which can result in substantial variations in simulated conductive cooling profiles for particle sizing. Aggregate structure in the form of intra-aggregate connectivity and shielding is an additional underlying cause for erroneous particle sizing, not presently captured by LII models.