Monte-Carlo simulation of soot particle coagulation and aggregation: the effect of a realistic size distribution

The evolution of the morphology of primary soot particles was investigated in a laminar premixed flame with the emphasis on the effect of a realistic particle size distribution. A time-dependent Monte-Carlo method was used to calculate flame trajectories of single particles. In the nucleation zone of the flame, particles were grown by coagulation and simultaneous surface growth. The particles for coagulation were selected according to a pre-calculated size distribution obtained by solving the dynamics of the entire soot particle ensemble. In the post-nucleation zone, defined by the point of transition from coalescent to aggregate growth, only surface growth was applied to the particles. The simulation results provide further support to the notion that particle nucleation and the presence of small particles influence the morphology of primary particles and the location of transition. It is demonstrated that the mean size of subparticles comprising the primary particles is substantially smaller when using a realistic size distribution in the nucleation zone of the investigated flame. This, in turn, reduces the degree of aggregation of the primary particles at the time of transition to an extent that surface growth is able to recover their spherical shape in the post-nucleation zone. (c) 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved.