(380l) Dynamics of Early Soot Formation By Reactive Molecular Dynamics

Soot formation is of fundamental importance in combustion systems as the presence of soot influences the efficiency of combustion. Soot emission necessitates post-combustion control technologies, as soot can have deleterious effects on human health and the environment. Developing an accurate representation of early soot formation stages has proven challenging. The initial steps in soot nucleation are thought to be due to clustering reactions of different gaseous precursors species. However, there are still large uncertainties in the reaction rates involved in soot nucleation.

Here, reactive molecular dynamics (MD) simulations are used to capture accurately the dynamics of soot nuclei at the early stages of their formation, to determine its structure and composition of incipient soot nuclei and to obtain precise soot inception rates. Bond breakage and new bond formation upon collisions are accounted for by employing a reactive ReaxFF interatomic potential. A newly-developed MD framework is applied to elucidate the collisions between nascent soot nuclei of various sizes and reactant precursor species. The above atomistic method allows for accounting for soot cluster morphology and composition during its collisional growth. Furthermore, the effect of process conditions on soot dynamics is quantified. The above method predicts accurately the sticking probability that can be used to correct the collision frequency of soot aggregates and can be readily employed into larger scale models, including mesoscale methods, such as discrete element models for nascent soot (Kelesidis et al., 2017) and computational fluid dynamics.

Kelesidis, G. A., Goudeli, E., & Pratsinis, S. E. (2017). Proc Combust Inst, 36, 29-50.