Quantitative effects of rapid heating on soot-particle sizing through analysis of two-pulse LII

Handle URI:
http://hdl.handle.net/10754/623026
Title:
Quantitative effects of rapid heating on soot-particle sizing through analysis of two-pulse LII
Authors:
Cenker, Emre ( 0000-0003-2015-4851 ) ; Roberts, William L. ( 0000-0003-1999-2831 )
Abstract:
During the rapid laser pulse heating and consecutive cooling in laser-induced incandescence (LII), soot particles may undergo thermal annealing and sublimation processes which lead to a permanent change in its optical properties and its primary particle size, respectively. Overall, effects of these two processes on soot and LII model-based particle sizing are investigated by measuring the two-color time-resolved (2C-TiRe) LII signal decay from in-flame soot after two consecutive laser pulses at 1064-nm wavelength. Experiments are carried out on a non-premixed laminar ethylene/air flame from a Santoro burner with both low and moderate laser fluences suitable for particle sizing. The probe volume is set to a radial position close to the flame axis where the soot particles are known to be immature or less graphitic. With the first pulse, soot is pre-heated, and the LII signal after the consecutive second pulse is used for analysis. The two-color incandescence emission technique is used for the pyrometric determination of the LII-heated peak soot temperature at the second pulse. A new LII simulation tool is developed which accounts for particle heating via absorption and annealing, and cooling via sublimation, conduction, and radiation with various existing sub-models from the literature. The same approach of using two laser pulses is implemented in the simulations. Measurements indicate that thermal annealing and associated absorption enhancement becomes important at laser fluences above 0.17 J/cm2 for the immature in-flame soot. After a heating pulse at 0.33 J/cm2, the increase of the soot absorption function is calculated as 35% using the temperature measured at the second pulse and an absorption model based on the Rayleigh approximation. Present annealing model, on the other hand, predicts graphitization of soot even in the absence of laser heating at typical flame temperatures. Recorded experimental LII signal decays and LII-heated peak soot temperature information are used for particle sizing with the LII modeling to assess the effects of sublimation. A reduction in particle size due to sublimation starts at a laser fluence of 0.1 J/cm2 for the in-flame soot. After a heating pulse at 0.33 J/cm2, the particle loses 55% of its initial mass.
KAUST Department:
Clean Combustion Research Center
Citation:
Cenker E, Roberts WL (2017) Quantitative effects of rapid heating on soot-particle sizing through analysis of two-pulse LII. Applied Physics B 123. Available: http://dx.doi.org/10.1007/s00340-017-6653-7.
Publisher:
Springer Nature
Journal:
Applied Physics B
Issue Date:
27-Feb-2017
DOI:
10.1007/s00340-017-6653-7
Type:
Article
ISSN:
0946-2171; 1432-0649
Sponsors:
The research reported in this publication was supported by funding from King Abdullah University of Science and Technology (KAUST).
Additional Links:
http://link.springer.com/article/10.1007/s00340-017-6653-7
Appears in Collections:
Articles; Clean Combustion Research Center

Full metadata record

DC FieldValue Language
dc.contributor.authorCenker, Emreen
dc.contributor.authorRoberts, William L.en
dc.date.accessioned2017-03-20T07:50:09Z-
dc.date.available2017-03-20T07:50:09Z-
dc.date.issued2017-02-27en
dc.identifier.citationCenker E, Roberts WL (2017) Quantitative effects of rapid heating on soot-particle sizing through analysis of two-pulse LII. Applied Physics B 123. Available: http://dx.doi.org/10.1007/s00340-017-6653-7.en
dc.identifier.issn0946-2171en
dc.identifier.issn1432-0649en
dc.identifier.doi10.1007/s00340-017-6653-7en
dc.identifier.urihttp://hdl.handle.net/10754/623026-
dc.description.abstractDuring the rapid laser pulse heating and consecutive cooling in laser-induced incandescence (LII), soot particles may undergo thermal annealing and sublimation processes which lead to a permanent change in its optical properties and its primary particle size, respectively. Overall, effects of these two processes on soot and LII model-based particle sizing are investigated by measuring the two-color time-resolved (2C-TiRe) LII signal decay from in-flame soot after two consecutive laser pulses at 1064-nm wavelength. Experiments are carried out on a non-premixed laminar ethylene/air flame from a Santoro burner with both low and moderate laser fluences suitable for particle sizing. The probe volume is set to a radial position close to the flame axis where the soot particles are known to be immature or less graphitic. With the first pulse, soot is pre-heated, and the LII signal after the consecutive second pulse is used for analysis. The two-color incandescence emission technique is used for the pyrometric determination of the LII-heated peak soot temperature at the second pulse. A new LII simulation tool is developed which accounts for particle heating via absorption and annealing, and cooling via sublimation, conduction, and radiation with various existing sub-models from the literature. The same approach of using two laser pulses is implemented in the simulations. Measurements indicate that thermal annealing and associated absorption enhancement becomes important at laser fluences above 0.17 J/cm2 for the immature in-flame soot. After a heating pulse at 0.33 J/cm2, the increase of the soot absorption function is calculated as 35% using the temperature measured at the second pulse and an absorption model based on the Rayleigh approximation. Present annealing model, on the other hand, predicts graphitization of soot even in the absence of laser heating at typical flame temperatures. Recorded experimental LII signal decays and LII-heated peak soot temperature information are used for particle sizing with the LII modeling to assess the effects of sublimation. A reduction in particle size due to sublimation starts at a laser fluence of 0.1 J/cm2 for the in-flame soot. After a heating pulse at 0.33 J/cm2, the particle loses 55% of its initial mass.en
dc.description.sponsorshipThe research reported in this publication was supported by funding from King Abdullah University of Science and Technology (KAUST).en
dc.publisherSpringer Natureen
dc.relation.urlhttp://link.springer.com/article/10.1007/s00340-017-6653-7en
dc.rightsThe final publication is available at Springer via http://dx.doi.org/10.1007/s00340-017-6653-7en
dc.titleQuantitative effects of rapid heating on soot-particle sizing through analysis of two-pulse LIIen
dc.typeArticleen
dc.contributor.departmentClean Combustion Research Centeren
dc.identifier.journalApplied Physics Ben
dc.eprint.versionPost-printen
kaust.authorCenker, Emreen
kaust.authorRoberts, William L.en
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