Numerical simulation and parametric sensitivity study of particle size distributions in a burner-stabilised stagnation flame

A detailed population balance model is used to perform a parametric sensitivity study on the computed particle size distributions (PSDs) for a laminar premixed ethylene burner-stabilised stagnation flame. The soot morphology in the post-flame region is studied using computed sintering level distributions, fringe length analysis of the polycyclic aromatic hydrocarbons (PAHs) within the primary soot particles, and TEM-like projections of aggregates. The computed PSDs were sensitive to the minimum particle inception size, the coagulation rate and the inception species concentration. Changes in the particle inception size and the coagulation rate led to an overall shift in the position of the coagulation peak. Only changes in the inception species concentration led to a systematic shift in both the position of the trough between the modes of the bimodal PSD and the coagulation peak at larger diameters. Given the overall model, varying the inception species concentration with each burner-stagnation plate separation was the only means possible to achieve a satisfactory agreement between the experimental and computed PSDs. This study shows that further work is required to better understand the soot precursor chemistry, the inception of soot particles. Additional work may also be needed in the area of experimental mobility sizing for the flame studied here.