Advanced

Plasma assisted combustion: Effects of O3 on large scale turbulent combustion studied with laser diagnostics and Large Eddy Simulations

Ehn, Andreas LU ; Zhu, Jiajian LU ; Petersson, Per LU ; Li, Zhongshan; Aldén, Marcus LU ; Fureby, C.; Hurtig, T.; Zettervall, N.; Larsson, A. and Larfeldt, J. (2015) In Proceedings of the Combustion Institute 35(3). p.3487-3495
Abstract
Abstract In plasma-assisted combustion, electric energy is added to the flame where the electric energy will be transferred to kinetic energy of the free electrons that, in turn, will modify the combustion chemical kinetics. In order to increase the understanding of this complex process, the influence of one of the products of the altered chemical kinetics, ozone (O3), has been isolated and studied. This paper reports on studies using a low-swirl methane (CH4) air flame at lean conditions with different concentrations of O3 enrichment. The experimental flame diagnostics include Planar Laser Induced Fluorescence (PLIF) imaging of hydroxyl (OH) and formaldehyde (CH2O). The experiments are also modeled using Large Eddy Simulations (LES) with... (More)
Abstract In plasma-assisted combustion, electric energy is added to the flame where the electric energy will be transferred to kinetic energy of the free electrons that, in turn, will modify the combustion chemical kinetics. In order to increase the understanding of this complex process, the influence of one of the products of the altered chemical kinetics, ozone (O3), has been isolated and studied. This paper reports on studies using a low-swirl methane (CH4) air flame at lean conditions with different concentrations of O3 enrichment. The experimental flame diagnostics include Planar Laser Induced Fluorescence (PLIF) imaging of hydroxyl (OH) and formaldehyde (CH2O). The experiments are also modeled using Large Eddy Simulations (LES) with a reaction model based on a skeletal CH4-air reaction mechanism combined with an O3 sub-mechanism to include the presence of O3 in the flame. This reaction mechanism is based on fundamental considerations including reactions between O3 and all other species involved. The experiments reveal an increase in CH2O in the low-swirl flame as small amounts of O3 is supplied to the CH4-air stream upstream of the flame. This increase is well predicted by the LES computations and the relative radical concentration shift is in good agreement with experimental data. Simulations also reveal that the O3 enrichment increase the laminar flame speed, su, with ∼10% and the extinction strain-rate, Ïext, with ∼20%, for 0.57% (by volume) O3. The increase in Ïext enables the O3 seeded flame to burn under more turbulent conditions than would be possible without O3 enrichment. Sensitivity analysis indicates that the increase in Ïext due to O3 enrichment is primarily due to the accelerated chain-branching reactions H 2 + O â OH + H , H 2 O + O â OH + OH and H + O 2 â OH + O . Furthermore, the increase in CH2O observed in both experiments and simulations suggest a significant acceleration of the chain-propagation reaction CH 3 + O â CH 2 O + H . (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to specialist publication or newspaper
publication status
published
subject
keywords
Laser-induced fluorescence, Large Eddy simulations, Ozone-assisted combustion, Plasma-assisted combustion, Turbulent combustion
categories
Popular Science
in
Proceedings of the Combustion Institute
volume
35
issue
3
pages
3487 - 3495
publisher
Elsevier
external identifiers
  • wos:000348049500116
  • scopus:84947899478
ISSN
1540-7489
DOI
10.1016/j.proci.2014.05.092
language
English
LU publication?
yes
id
0b66a489-c2f5-4d58-b3e0-39b147cfe4b0 (old id 4855895)
alternative location
http://www.sciencedirect.com/science/article/pii/S1540748914000959
date added to LUP
2014-12-03 03:28:54
date last changed
2017-07-23 03:18:27
@misc{0b66a489-c2f5-4d58-b3e0-39b147cfe4b0,
  abstract     = {Abstract In plasma-assisted combustion, electric energy is added to the flame where the electric energy will be transferred to kinetic energy of the free electrons that, in turn, will modify the combustion chemical kinetics. In order to increase the understanding of this complex process, the influence of one of the products of the altered chemical kinetics, ozone (O3), has been isolated and studied. This paper reports on studies using a low-swirl methane (CH4) air flame at lean conditions with different concentrations of O3 enrichment. The experimental flame diagnostics include Planar Laser Induced Fluorescence (PLIF) imaging of hydroxyl (OH) and formaldehyde (CH2O). The experiments are also modeled using Large Eddy Simulations (LES) with a reaction model based on a skeletal CH4-air reaction mechanism combined with an O3 sub-mechanism to include the presence of O3 in the flame. This reaction mechanism is based on fundamental considerations including reactions between O3 and all other species involved. The experiments reveal an increase in CH2O in the low-swirl flame as small amounts of O3 is supplied to the CH4-air stream upstream of the flame. This increase is well predicted by the LES computations and the relative radical concentration shift is in good agreement with experimental data. Simulations also reveal that the O3 enrichment increase the laminar flame speed, su, with ∼10% and the extinction strain-rate, Ïext, with ∼20%, for 0.57% (by volume) O3. The increase in Ïext enables the O3 seeded flame to burn under more turbulent conditions than would be possible without O3 enrichment. Sensitivity analysis indicates that the increase in Ïext due to O3 enrichment is primarily due to the accelerated chain-branching reactions H 2 + O â OH + H , H 2 O + O â OH + OH and H + O 2 â OH + O . Furthermore, the increase in CH2O observed in both experiments and simulations suggest a significant acceleration of the chain-propagation reaction CH 3 + O â CH 2 O + H .},
  author       = {Ehn, Andreas and Zhu, Jiajian and Petersson, Per and Li, Zhongshan and Aldén, Marcus and Fureby, C. and Hurtig, T. and Zettervall, N. and Larsson, A. and Larfeldt, J.},
  issn         = {1540-7489},
  keyword      = {Laser-induced fluorescence,Large Eddy simulations,Ozone-assisted combustion,Plasma-assisted combustion,Turbulent combustion},
  language     = {eng},
  number       = {3},
  pages        = {3487--3495},
  publisher    = {Elsevier},
  series       = {Proceedings of the Combustion Institute},
  title        = {Plasma assisted combustion: Effects of O3 on large scale turbulent combustion studied with laser diagnostics and Large Eddy Simulations},
  url          = {http://dx.doi.org/10.1016/j.proci.2014.05.092},
  volume       = {35},
  year         = {2015},
}