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A Molecular Dynamics Study of Inception and Growth of Soot during Combustion
Akaash Sharmaa, Khaled Mosharraf Mukut, Eirini Goudeli, SOMESH ROY, Marquette University
Abstract Number: 193
Working Group: Combustion
Abstract
Accurate prediction of soot formation and growth in combustion systems is very important for reasons ranging from reduced combustion efficiency to the global climatic forcing of soot. Unfortunately, the fundamental physico-chemical processes behind the formation of soot are still not completely understood. In this study, a detailed and systematic investigation of inception and growth of soot is conducted by full-atom reactive molecular dynamics (rMD) simulations using reactive force-field (reaxFF) interatomic potentials for bond breakage and new bond formation upon collisions. The simulations show the formation and evolution of several precursors and incipient soot clusters with time starting with acetylene at different temperatures. The number of 5-, 6-, and 7-membered aromatic rings increase with time as the size of the incipient soot clusters grows. The majority of the aromatic rings are found at the core of the clusters, while the aliphatic branches are found mostly on the surface. The gyration diameter, Sauter-mean diameter, and the fraction of the aromatic rings within the incipient cluster increase substantially with time, while the C/H ratio remains approximately constant at about 2.5, consistent with the literature. The incipient clusters also show a decrease in the relative shape anisotropy with time leading to a more spherical shape as the aliphatic branches on the particle surface become shorter. Additionally instances of sintering were observed specifically for certain ranges of temperature and incipient cluster sizes.