Influence of the cumulative effects of multiple laser pulses on laser-induced incandescence signals from soot

TitleInfluence of the cumulative effects of multiple laser pulses on laser-induced incandescence signals from soot
Publication TypeJournal Article
Year of Publication2011
AuthorsDe Iuliis, S, Cignoli, F, Maffi, S, Zizak, G
Journal TitleApplied Physics B: Lasers and Optics
Volume104
Issue2
Pages321-330
ISSN0946-2171
KeywordsLII; multiple laser pulses
Abstract

The effect of multiple laser pulses reaching soot particles before an actual laser-induced incandescence (LII) measurement is investigated in order to gain some insights on soot morphological and fine structure changes due to rapid laser heating. Soot, extracted from a premixed and a quenched diffusion flames, is flowing through a tubular cell and undergoes a variable number of pulses at different fluence. The response of soot is studied by the two-color LII technique. Transmission electron microscopy (TEM) analysis of laser-modified soot aggregates from the diffusion flame is also presented. The results indicate that even at low laser fluences a permanent soot transformation is induced causing an increase in the absorption function E ( m ). This is interpreted as an induced graphitization of soot particles by the laser pulse heating. At high fluences the vaporization process and a profound restructuring of soot particles affect the morphology of the aggregates. Soot from diffusion and premixed flames behaves in a similar way although this similarity occurs at different fluence levels indicating a different initial fine structure of soot particles.

URLhttp://dx.doi.org/10.1007/s00340-011-4535-y
DOI10.1007/s00340-011-4535-y