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Multi-species PLIF study of the structures of turbulent premixed methane/air jet flames in the flamelet and thin-reaction zones regimes

Rosell, Joakim LU ; Bai, Xue Song LU ; Sjöholm, Johan LU ; Zhou, Bo LU ; Li, Zheming LU ; Wang, Zhenkan LU ; Pettersson, Per; Li, Zhongshan LU ; Richter, Mattias LU and Alden, Marcus LU (2017) In Combustion and Flame 182. p.324-338
Abstract

Simultaneously planar laser-induced fluorescence (PLIF) measurements of OH, CH, CH2O and toluene are carried out to investigate the structures of turbulent premixed methane/air jet flames in the flamelet regime and the thin-reaction zones regime. A premixed flame jet burner of an inner diameter of 1.5 mm is employed. Stoichiometric methane/air mixtures introduced as a jet are ignited and stabilized in a hot co-flow generated by a coaxial porous plug pilot flame surrounding the jet. The Reynolds number for the studied jet ranges from 960 to 11,500 with the characteristic Karlovitz number ranging from 1 to 60. The focus of this study is on the characterization of the structures and turbulent burning velocity of premixed flames... (More)

Simultaneously planar laser-induced fluorescence (PLIF) measurements of OH, CH, CH2O and toluene are carried out to investigate the structures of turbulent premixed methane/air jet flames in the flamelet regime and the thin-reaction zones regime. A premixed flame jet burner of an inner diameter of 1.5 mm is employed. Stoichiometric methane/air mixtures introduced as a jet are ignited and stabilized in a hot co-flow generated by a coaxial porous plug pilot flame surrounding the jet. The Reynolds number for the studied jet ranges from 960 to 11,500 with the characteristic Karlovitz number ranging from 1 to 60. The focus of this study is on the characterization of the structures and turbulent burning velocity of premixed flames in the flamelet and the thin-reaction zones regimes. The preheat zone is analyzed using the CH2O and toluene PLIF fields, whereas the reaction zone is analyzed using the CH and OH PLIF fields. Laser Doppler Anemometer (LDA) measurements are performed to characterize the turbulence field and it is noted that when the Reynolds/Karlovitz number increases a successive thickening of the preheat zone is observed, whereas the reaction zone, characterized by the CH layer maintains nearly the same thickness. The heat release zone, characterized by the combination of the OH and CH2O PLIF fields, is shown to nearly maintain the same thickness under the present experimental conditions. The flame surface wrinkle ratio is shown to be Reynolds number and Karlovitz number independent when the Reynolds number is high enough such that the smallest wrinkle scales reach to the length scales of the thin reaction layers. The global fuel consumption speed of the jet flame is analyzed using the toluene PLIF field and the OH PLIF field. A discrepancy in the two consumption velocities is found as the Karlovitz number increases. This is found to be a result of the broadening of the oxidation zone. These findings provide experimental support to the flamelet and thin-reaction zone regime hypotheses of turbulent premixed combustion.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Flamelet regime, Karlovitz number, Multiple species simultaneous PLIF, Thin-reaction zone regime, Turbulent premixed flames
in
Combustion and Flame
volume
182
pages
15 pages
publisher
Elsevier
external identifiers
  • scopus:85019082467
  • wos:000404945100029
ISSN
0010-2180
DOI
10.1016/j.combustflame.2017.04.003
language
English
LU publication?
yes
id
505216de-e1a7-4712-ae7d-1fe1ec3097d5
date added to LUP
2017-05-29 11:11:58
date last changed
2018-01-07 12:05:30
@article{505216de-e1a7-4712-ae7d-1fe1ec3097d5,
  abstract     = {<p>Simultaneously planar laser-induced fluorescence (PLIF) measurements of OH, CH, CH<sub>2</sub>O and toluene are carried out to investigate the structures of turbulent premixed methane/air jet flames in the flamelet regime and the thin-reaction zones regime. A premixed flame jet burner of an inner diameter of 1.5 mm is employed. Stoichiometric methane/air mixtures introduced as a jet are ignited and stabilized in a hot co-flow generated by a coaxial porous plug pilot flame surrounding the jet. The Reynolds number for the studied jet ranges from 960 to 11,500 with the characteristic Karlovitz number ranging from 1 to 60. The focus of this study is on the characterization of the structures and turbulent burning velocity of premixed flames in the flamelet and the thin-reaction zones regimes. The preheat zone is analyzed using the CH<sub>2</sub>O and toluene PLIF fields, whereas the reaction zone is analyzed using the CH and OH PLIF fields. Laser Doppler Anemometer (LDA) measurements are performed to characterize the turbulence field and it is noted that when the Reynolds/Karlovitz number increases a successive thickening of the preheat zone is observed, whereas the reaction zone, characterized by the CH layer maintains nearly the same thickness. The heat release zone, characterized by the combination of the OH and CH<sub>2</sub>O PLIF fields, is shown to nearly maintain the same thickness under the present experimental conditions. The flame surface wrinkle ratio is shown to be Reynolds number and Karlovitz number independent when the Reynolds number is high enough such that the smallest wrinkle scales reach to the length scales of the thin reaction layers. The global fuel consumption speed of the jet flame is analyzed using the toluene PLIF field and the OH PLIF field. A discrepancy in the two consumption velocities is found as the Karlovitz number increases. This is found to be a result of the broadening of the oxidation zone. These findings provide experimental support to the flamelet and thin-reaction zone regime hypotheses of turbulent premixed combustion.</p>},
  author       = {Rosell, Joakim and Bai, Xue Song and Sjöholm, Johan and Zhou, Bo and Li, Zheming and Wang, Zhenkan and Pettersson, Per and Li, Zhongshan and Richter, Mattias and Alden, Marcus},
  issn         = {0010-2180},
  keyword      = {Flamelet regime,Karlovitz number,Multiple species simultaneous PLIF,Thin-reaction zone regime,Turbulent premixed flames},
  language     = {eng},
  month        = {08},
  pages        = {324--338},
  publisher    = {Elsevier},
  series       = {Combustion and Flame},
  title        = {Multi-species PLIF study of the structures of turbulent premixed methane/air jet flames in the flamelet and thin-reaction zones regimes},
  url          = {http://dx.doi.org/10.1016/j.combustflame.2017.04.003},
  volume       = {182},
  year         = {2017},
}