Influence of rapid laser heating on the optical properties of in-flame soot

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DOIResolve DOI: http://doi.org/10.1007/s00340-015-6072-6
AuthorSearch for: ; Search for: ; Search for: ; Search for: ; Search for:
TypeArticle
Journal titleApplied physics B
ISSN0946-2171
1432-0649
Volume
Issue
AbstractTo understand the effect of rapid heating on the optical properties of in-flame soot and its potential influence on the laser-induced incandescence (LII) signal, the time-resolved extinction coefficient of soot is measured in diffusion and premixed flames during laser heating. Heating is performed using a 1064-nm pulsed laser with fluences ranging from 0.2 to 6.2 mJ/mm2. Extinction measurements are carried out using continuous-wave lasers at four different wavelengths. A rapid enhancement of extinction, by up to 10 % in the diffusion flame and 18 % in the premixed flame, occurs during laser heating most likely as a result of temperature-dependent optical properties and laser-induced thermal annealing of soot. The thermal expansion of flame gases causes a gradual decline of soot concentration for about 2 μs after the laser pulse. Significant loss of soot material by sublimation is observed at fluences as low as 1.03 and 2.06 mJ/mm2 for the diffusion and premixed flames, respectively. A secondary rise in extinction coefficient is observed from about 50 to 800 ns after the laser pulse at low monitoring wavelengths, attributed to the formation of light-absorbing gaseous species from the sublimated soot material. These effects may impact the LII signal and should be accounted for in LII analysis.
Publication date
LanguageEnglish
AffiliationMeasurement Science and Standards; National Research Council Canada
Peer reviewedYes
NPARC number21275118
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Record identifier8d1b58d1-0398-428d-a9b5-ccc400fa8fb7
Record created2015-05-11
Record modified2016-05-09
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