Investigation of the Effect of Radiation on the Thermophoretic Motion of Soot Particles in Free-Molecular Regime

Abstract

The coupling of radiation and thermophoresis is hypothesized to result in attractive forces among soot particles in combustion environments. The effect of radiation from the soot particles on their thermophoretic motion in the free-molecular regime is studied by developing a `synthetic' simulation model. A Monte Carlo technique is used to carry out this study and the models are developed both for the two-particle system and the aggregate system that mimics cluster-cluster aggregation. The transfer of momentum and energy to and from the soot particles are computed via the monte carlo method. The thermophoretic force and the coagulation ratios are calculated for the developed models. The results indicate that thermophoresis would be a significant mode of soot particle coagulation for larger particle sizes and higher gas temperatures. The sphere aggregates are compared to single spheres with equivalent volume, surface area, and radius of gyration and the results show that the aggregate can be approximated to its volume equivalent sphere in a two-sphere model.