An analysis of soot formation pathways in laminar coflow ethylene flames at higher pressures

Sooting laminar diffusion flames at atmospheric and elevated pressures are investigated numerically by solving finite rate chemical kinetic mechanism, which is used to model the evolution of larger polycyclic aromatic hydrocarbons (PAHs) up to coronene. The soot formation is analyzed at higher pressures using Method of Moments with interpolative closure (MOMIC). In this study, two reduced mechanisms are considered, which have soot precursor up to naphthalene and coronene to simulate ethylene laminar coflow diffusion flames. The results show that soot volume fraction is under-predicted by both mechanisms, due to the under-prediction of soot precursors. Predicted peak soot volume fraction is slightly impacted by chemical mechanism. Both mechanisms provide the same peak soot volume fraction at atmospheric pressure and shows a difference of 25% at elevated pressure. However, the inclusion of larger PAH species in the KAUST mechanism shows a similar spatial distribution of soot volume fraction with experiment due to homogeneous surface reactions in nucleation. The results of the pathway analysis indicate the increase in pressure affects the soot formation through the pathways of PAHs nucleation condensation and H-abstraction C2 H2-addition (HACA) mechanism.