Investigations of the long-term effects of LII on soot and bath gas

Handle URI:
http://hdl.handle.net/10754/625425
Title:
Investigations of the long-term effects of LII on soot and bath gas
Authors:
Cenker, Emre ( 0000-0003-2015-4851 ) ; Bennett, A.; Roberts, William L. ( 0000-0003-1999-2831 )
Abstract:
A combination of high-repetition rate imaging, laser extinction measurements, two-colour soot pyrometry imaging, and high-resolution transmission electron microscopy of thermophoretically sampled soot is used to investigate the long-term and permanent effects of rapid heating of in-flame soot during laser-induced incandescence (LII). Experiments are carried out on a laminar non-premixed co-annular ethylene/air flame with various laser fluences. The high-repetition rate images clearly show that the heated and the neighbouring laser-border zones undergo a permanent transformation after the laser pulse, and advect vertically with the flow while the permanent marking is preserved. The soot volume fraction at the heated zone reduces due to the sublimation of soot and the subsequent enhanced oxidation. At the laser-border zones, however, optical thickness increases that may be due to thermophoretic forces drawing hot particles towards relatively cooler zones and the rapid compression of the bath gas induced by the pressure waves created by the expansion of the desorbed carbon clusters. Additionally sublimed carbon clusters can condense onto existing particles and contribute to increase of the optical thickness. Time-resolved two-colour pyrometry imaging show that the increased temperature of soot both in the heated and neighbouring laser-border zones persists for several milliseconds. This can be associated to the increase in the bath-gas temperature, and a change in the wavelength-dependent emissivity of soot particles induced by the thermal annealing of soot. Ex-situ analysis show that the lattice structure of the soot sampled at the laser-border zones tend to change and soot becomes more graphitic. This may be attributed to thermal annealing induced by elevated temperature.
KAUST Department:
Clean Combustion Research Center
Citation:
Cenker E, Bennett A, Roberts WL (2017) Investigations of the long-term effects of LII on soot and bath gas. Aerosol Science and Technology: 00–00. Available: http://dx.doi.org/10.1080/02786826.2017.1368444.
Publisher:
Informa UK Limited
Journal:
Aerosol Science and Technology
Issue Date:
24-Aug-2017
DOI:
10.1080/02786826.2017.1368444
Type:
Article
ISSN:
0278-6826; 1521-7388
Sponsors:
The research reported in this publication was supported by funding from King Abdullah University of Science and Technology (KAUST).
Additional Links:
http://www.tandfonline.com/doi/full/10.1080/02786826.2017.1368444
Appears in Collections:
Articles; Clean Combustion Research Center

Full metadata record

DC FieldValue Language
dc.contributor.authorCenker, Emreen
dc.contributor.authorBennett, A.en
dc.contributor.authorRoberts, William L.en
dc.date.accessioned2017-08-30T11:40:25Z-
dc.date.available2017-08-30T11:40:25Z-
dc.date.issued2017-08-24en
dc.identifier.citationCenker E, Bennett A, Roberts WL (2017) Investigations of the long-term effects of LII on soot and bath gas. Aerosol Science and Technology: 00–00. Available: http://dx.doi.org/10.1080/02786826.2017.1368444.en
dc.identifier.issn0278-6826en
dc.identifier.issn1521-7388en
dc.identifier.doi10.1080/02786826.2017.1368444en
dc.identifier.urihttp://hdl.handle.net/10754/625425-
dc.description.abstractA combination of high-repetition rate imaging, laser extinction measurements, two-colour soot pyrometry imaging, and high-resolution transmission electron microscopy of thermophoretically sampled soot is used to investigate the long-term and permanent effects of rapid heating of in-flame soot during laser-induced incandescence (LII). Experiments are carried out on a laminar non-premixed co-annular ethylene/air flame with various laser fluences. The high-repetition rate images clearly show that the heated and the neighbouring laser-border zones undergo a permanent transformation after the laser pulse, and advect vertically with the flow while the permanent marking is preserved. The soot volume fraction at the heated zone reduces due to the sublimation of soot and the subsequent enhanced oxidation. At the laser-border zones, however, optical thickness increases that may be due to thermophoretic forces drawing hot particles towards relatively cooler zones and the rapid compression of the bath gas induced by the pressure waves created by the expansion of the desorbed carbon clusters. Additionally sublimed carbon clusters can condense onto existing particles and contribute to increase of the optical thickness. Time-resolved two-colour pyrometry imaging show that the increased temperature of soot both in the heated and neighbouring laser-border zones persists for several milliseconds. This can be associated to the increase in the bath-gas temperature, and a change in the wavelength-dependent emissivity of soot particles induced by the thermal annealing of soot. Ex-situ analysis show that the lattice structure of the soot sampled at the laser-border zones tend to change and soot becomes more graphitic. This may be attributed to thermal annealing induced by elevated temperature.en
dc.description.sponsorshipThe research reported in this publication was supported by funding from King Abdullah University of Science and Technology (KAUST).en
dc.publisherInforma UK Limiteden
dc.relation.urlhttp://www.tandfonline.com/doi/full/10.1080/02786826.2017.1368444en
dc.rightsThis is an Accepted Manuscript of an article published by Taylor & Francis in Aerosol Science and Technology on 24 Aug 2017, available online: http://wwww.tandfonline.com/10.1080/02786826.2017.1368444.en
dc.subjectLIIen
dc.subjecthigh-repetition rate imagingen
dc.subjectpyrometry imagingen
dc.subjectbath-gas heatingen
dc.subjectthermal annealingen
dc.subjectsoot oxidationen
dc.titleInvestigations of the long-term effects of LII on soot and bath gasen
dc.typeArticleen
dc.contributor.departmentClean Combustion Research Centeren
dc.identifier.journalAerosol Science and Technologyen
dc.eprint.versionPost-printen
kaust.authorCenker, Emreen
kaust.authorBennett, A.en
kaust.authorRoberts, William L.en
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