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Characterization of the reaction zone structures in a laboratory combustor using optical diagnostics : From flame to flameless combustion

Zhou, Bo LU ; Costa, Mário; Li, Zhongshan LU ; Aldén, Marcus LU and Bai, Xue Song LU (2017) In Proceedings of the Combustion Institute2000-01-01+01:00 p.4305-4312
Abstract

Flame emission spectra and OH* imaging are carried out together with planar laser-induced fluorescence (PLIF) of OH and CH2O to characterize the reaction zone structures of three combustion modes, i.e. a flame mode, a transition mode and a flameless mode, established in a laboratory combustor. Spectroscopic measurements indicate that the invisibility of the flameless mode can be attributed to a moderate suppression of the CH* and C2 * emissions as well as a significant increase of the continuous background from the CO2 * emission. PLIF measurements of OH and CH2O show that all studied cases experience a premixing of unburnt reactants with the... (More)

Flame emission spectra and OH* imaging are carried out together with planar laser-induced fluorescence (PLIF) of OH and CH2O to characterize the reaction zone structures of three combustion modes, i.e. a flame mode, a transition mode and a flameless mode, established in a laboratory combustor. Spectroscopic measurements indicate that the invisibility of the flameless mode can be attributed to a moderate suppression of the CH* and C2 * emissions as well as a significant increase of the continuous background from the CO2 * emission. PLIF measurements of OH and CH2O show that all studied cases experience a premixing of unburnt reactants with the recirculated oxygen-containing hot burnt gases in the near-inlet region. It is found that the interplay between turbulence intensity and the availability of oxygen from both the inlet air jet and recirculation is important in establishing flameless combustion in the present combustor. Consistent with a previous chemical kinetic study, the present experimental results suggested that the flameless condition is in favor of converting a highly diluted CH4/air mixture into CO and H2, which will be further oxidized. For the flameless case, CH2O is detected slightly before the OH* region, where a relatively high level of minimal OH is observed. The reaction zone region marked by the OH* emission for the flameless case is characterized by a uniform instantaneous OH distribution with small standard deviation, suggesting a distributed oxidization of intermediate species such as CO and H2 for this combustion mode.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Flame emission spectra, Flameless combustion, Planar laser-induced fluorescence, Reaction zone structure visualization
in
Proceedings of the Combustion Institute2000-01-01+01:00
pages
4305 - 4312
publisher
Elsevier
external identifiers
  • scopus:85003013348
  • wos:000393412600109
ISSN
1540-7489
DOI
10.1016/j.proci.2016.06.182
language
English
LU publication?
yes
id
0f1e831d-819a-45bc-9e32-fdcd12737c17
date added to LUP
2017-02-17 12:39:26
date last changed
2018-03-25 04:34:20
@article{0f1e831d-819a-45bc-9e32-fdcd12737c17,
  abstract     = {<p>Flame emission spectra and OH<sup>*</sup> imaging are carried out together with planar laser-induced fluorescence (PLIF) of OH and CH<sub>2</sub>O to characterize the reaction zone structures of three combustion modes, i.e. a flame mode, a transition mode and a flameless mode, established in a laboratory combustor. Spectroscopic measurements indicate that the invisibility of the flameless mode can be attributed to a moderate suppression of the CH<sup>*</sup> and C<sub>2</sub> <sup>*</sup> emissions as well as a significant increase of the continuous background from the CO<sub>2</sub> <sup>*</sup> emission. PLIF measurements of OH and CH<sub>2</sub>O show that all studied cases experience a premixing of unburnt reactants with the recirculated oxygen-containing hot burnt gases in the near-inlet region. It is found that the interplay between turbulence intensity and the availability of oxygen from both the inlet air jet and recirculation is important in establishing flameless combustion in the present combustor. Consistent with a previous chemical kinetic study, the present experimental results suggested that the flameless condition is in favor of converting a highly diluted CH<sub>4</sub>/air mixture into CO and H<sub>2</sub>, which will be further oxidized. For the flameless case, CH<sub>2</sub>O is detected slightly before the OH<sup>*</sup> region, where a relatively high level of minimal OH is observed. The reaction zone region marked by the OH<sup>*</sup> emission for the flameless case is characterized by a uniform instantaneous OH distribution with small standard deviation, suggesting a distributed oxidization of intermediate species such as CO and H<sub>2</sub> for this combustion mode.</p>},
  author       = {Zhou, Bo and Costa, Mário and Li, Zhongshan and Aldén, Marcus and Bai, Xue Song},
  issn         = {1540-7489},
  keyword      = {Flame emission spectra,Flameless combustion,Planar laser-induced fluorescence,Reaction zone structure visualization},
  language     = {eng},
  pages        = {4305--4312},
  publisher    = {Elsevier},
  series       = {Proceedings of the Combustion Institute2000-01-01+01:00},
  title        = {Characterization of the reaction zone structures in a laboratory combustor using optical diagnostics : From flame to flameless combustion},
  url          = {http://dx.doi.org/10.1016/j.proci.2016.06.182},
  year         = {2017},
}