Comparison of the ionic mechanism of soot formation with a free radical mechanism

Abstract

The possible mechanisms by which large hydrocarbon ions might be produced in a fuel rich sooty flame are examined and all of them are eliminated except growth through ion-molecule reactions starting from the chemiion, HCO+. Large ions are not, as sometimes assumed, an indicator of neutral species. The ionic mechanism of soot nucleation is compared with a free radical mechanism by comparing the time each mechanism requires to add 10 carbon atoms to the growing species, ion or neutral. Experimental concentrations are combined with appropriate rate coefficients for the individual steps. The ionic mechanism appears to require less time, but the differences are within the accuracy of the data available.