EFFECT OF SELECTIVE ACCOMMODATION ON SOOT AGGREGATE SHIELDING IN TIME-RESOLVED LASER-INDUCED INCANDESCENCE EXPERIMENTS

Time-resolved laser-induced incandescence (TiRe-LII) is an emerging diagnostic for characterizing primary-particle size distributions within soot-laden aerosols. This measurement requires an accurate model of heat conduction between the laser-energized soot and the surrounding gas, which is complicated by fractal-like structure of soot aggregates since primary particles on the aggregate exterior shield the interior from approaching gas molecules. Previous efforts to characterize aggregate shielding using Direct-Simulation-Monte-Carlo (DSMC) analysis assume a monatomic gas and a Maxwell kernel, which is known to be a poor representation of true gas/surface scattering physics. This paper investigates how selective thermal accommodation into the translational and rotational modes of the gas molecule influences the aggregate shielding effect using the Cercignani-Lampis-Lord (CLL) kernel and thermal accommodation coefficients derived from molecular dynamics simulations.