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

Soot aggregation with simultaneous surface growth was modeled using a dynamic Monte Carlo method. Simulations were performed in the environment of a 10-bar laminar premixed flame of ethylene. The Monte Carlo algorithm begins in the particle inception zone and constructs soot particles via ensemble-averaged collisions between small spheres and deposition of gaseous species on the sphere surfaces. Simulations were conducted using three scenarios. Scenario 1 forces all spheres to grow at a uniform rate, whereas scenario 2 only permits them to grow once they have collided and stuck to each other. Results from 1 and 2 were compared to a reference, labeled scenario 0, which simulates aggregation in the absence of surface growth. The simulations demonstrate that aggregation with sufficiently small spherical particles in the presence of surface growth leads to a spheroidal shape. The results show that the spheroidal shape of particles is attributed to rapid surface growth and intense particle nucleation. In addition, particle shape may also be affected by rearrangement of the internal structure of colliding aromatic clusters.

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