Monte carlo simulation of soot aggregation with simultaneous surface growth-why primary particles appear spherical

Numerical simulations of soot aggregation in premixed laminar flames

“…Recent studies, using numerical simulations of singleparticle trajectories [22,23] and of "lumped" properties with the method of moments [2], suggested a critical importance of interplay among all these individual processes-nucleation, coagulation, and surface growth. Moreover, these results suggested that the transition of spherical, coalescent growth into fractal-like objects is linked directly to the nucleation, as it supplies the abundance of very small primary particles.…”

“…This is accomplished with the code of Mitchell [21], which performs a ballistic collision in R 3 and, based on the point of contact of the newly formed pair, translates the coordinates of the primary particles of one of the aggregates relative to the other particle.…”

“…The corresponding number of carbon atoms is added to the aggregate and by considering the density of soot and the surface area of the aggregate, each primary particle is also increased in radius. The surface area of the particle, its radius of gyration, and fractal dimension are then recalculated with Monte-Carlo integration routines over the whole aggregate [21]. If through oxidation the number of carbon atoms in an aggregate falls to below 32 then this particle is considered "oxidized" and is removed from the system [6,3].…”

“…In recent applications of this general approach, particle dynamics were formulated in terms of one or two state variables like total particle volume and surface area [3,10,25,24]. In another development, a collector-particle technique was applied to investigate the transition between coalescent and aggregate growth [22,23], with the results incorporated [2] into the method of moments [6].…”

“…In the present study we combine two techniques, the efficient stochastic particle collision algorithm [3,10] and the sterically-resolved collector-particle simulations [22,23]. In the following, we describe the numerical model, test the accuracy and authenticity of model predictions, and then perform a series of numerical simulations of time evolution of soot particles and their size distribution.…”