A possible radiative model for microniccarbonaceous particle sizing based on time-resolved laser-induced incandescence

Abstract

A numerical model of time-resolved laser-induced incandescence(TIRE-LII) for different kinds of large carbonaceous particleis developed in this paper. Theoretical temporal LII signalswere computed for the following classes of particles: soot,the well known hollow particles called cenospheres (tens ofmicrons) and full carbonaceous particles called by analogypleospheres (a few microns), pleo- from the Greek pleos(solid). The large carbonaceous particles have a characteristictime for internal gradient dissipation much longer than soot,thus a temperature profile establishes inside them. On thebasis of these observations, a spatial time-dependent model forcenospheres and pleospheres was considered, i.e. a system ofpartial differential equations based on mass and energybalances.The computed LII signals pointed out the sensitivity of themodel to the different kinds of particle considered in thispaper. The two classes of large carbonaceous particles showeddifferent thermal behaviours. Furthermore, the analysis of thecombined effects on the total theoretical LII signal of thedifferent particles highlighted the sensitivity of the time decayof the LII profiles to the mean particle size distributionsand to the relative particle number ratios inside thecontrol volume. These results may constitute a basis of astrategy for a comprehensive discrimination between soot andlarge particles, and for their identification, as in heavy-oilcombustion.