Mechanisms of soot nucleation in flames—A critical review

Data in the literature have been organized to give a detailed description of the chemical sequences leading to soot formation in a premixed laminar flame. Neutral free radical, polyacetylene, and polycyclic aromatic hydrocarbon mechanisms are not consistent with this description. However, when chemiions are assumed to be the precursor on which the free radicals, polyacetylenes, and polycyclic aromatic hydrocarbons repeatedly add in fast ion-molecule reactions, a mechanism can be developed which is consistent with experiment. This mechanism should be tested further by careful observations of both ion and neutral species (including free radical) profiles in flames and by developing a computer model of the process to compare with experiment.