Evolution of soot size distribution during soot formation and soot oxidation-fragmentation in premixed flames: experimental and modeling study

The goal of this research was to provide better insights into the evolution of particle size distributions (PSDs) during soot formation, oxidation and fragmentation in premixed flames. Soot formation was studied in premixed ethylene/air, ethylene/benzene/air and benzene/air flat flames under different flame temperatures and C/O ratio conditions. The results demonstrated the major differences in the evolution of the PSDs, both measured and modeled, of soot derived from these flames. The model included reaction pathways leading to the formation of nano-sized particles and their coagulation to larger soot particles. The PSDs for these flames, both experimental and modeled, evolved from a single particle mode to a bimodal PSD. An important distinction between these flames was the behavior of the nucleation mode which persisted at all heights above the burner (HAB) for ethylene/air whereas it decreased for ethylene/benzene/air and was greatly suppressed at greater HAB for the pure benzene/air flames. The explanation for the decreased nucleation mode at higher elevations in the benzene flames was mainly associated with the decrease of soot precursors after the main oxidation zone of the benzene flames.