Detailed kinetic modeling of soot formation at lightly sooting conditions

Soot particles formed in combustion processes are well-known for their negative effects, but their formation is still elusive and challenging. In particular, the main chemical and physical pathways are not fully understood. It is important to characterize soot not only in terms of mass yield but also to accurately characterize number density and particle size distribution (PSDF). The distribution of soot particles is essential to understand the soot evolution in a flame. The aim of this work is to revise and validate a detailed kinetic mechanism based on a discrete sectional approach for soot, with the aim to compare the model predictions with the measurement from Gu et al. (2016) in burner-stabilized stagnation (BSS) configuration. The lightly sooting condition flames (ϕ = 1.8, 60% Ar, 1 atm) with different maximum temperatures are simulated using a pseudo-one-dimensional stagnation model. The predicted PSDF is in reasonable agreement with experimental results, but the model only partially reproduces the distinct separation between nucleation and coagulation modes observed experimentally at lowtemperature (flame K3). The model predictions slightly underestimate the particle size at K3 flames, leading to the underprediction of soot volume fraction and number density. The predicted PSDF of high-temperature flames (K6) reproduces the unimodal distribution of nucleation tails observed experimentally. The flux analysis of benzene at the maximum temperature shows that the lower formation of soot particles could be a result of the thermodynamically reversibility to form gasphase species at high temperature (>1750 K). The predicted trends of soot number density and volume fraction of all flames are quite satisfactory. However, this study shows that further attention to the formation of PAHs and their condensation on soot particles is required.