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Investigations of microwave stimulation of a turbulent low-swirl flame

Ehn, A. LU ; Petersson, P. LU ; Zhu, J. J. LU ; Li, Z. S. LU ; Aldén, M. LU ; Nilsson, E. J K LU ; Larfeldt, J. LU ; Larsson, A.; Hurtig, T. and Zettervall, N. LU , et al. (2017) In Proceedings of the Combustion Institute2000-01-01+01:00 36(3). p.4121-4128
Abstract

Irradiating a flame by microwave radiation is one of several plasma-assisted combustion (PAC) technologies that can be used to modify the combustion chemical kinetics in order to improve flame-stability and to delay lean blow-out. One practical implication is that engines may be able to operate with leaner fuel mixtures and have an improved fuel flexibility capability including biofuels. In addition, this technology may assist in reducing thermoacoustic instabilities that may severely damage the engine and increase emission production. To examine microwave-assisted combustion a combined experimental and computational study of microwave-assisted combustion is performed for a lean, turbulent, swirl-stabilized, stratified flame at... (More)

Irradiating a flame by microwave radiation is one of several plasma-assisted combustion (PAC) technologies that can be used to modify the combustion chemical kinetics in order to improve flame-stability and to delay lean blow-out. One practical implication is that engines may be able to operate with leaner fuel mixtures and have an improved fuel flexibility capability including biofuels. In addition, this technology may assist in reducing thermoacoustic instabilities that may severely damage the engine and increase emission production. To examine microwave-assisted combustion a combined experimental and computational study of microwave-assisted combustion is performed for a lean, turbulent, swirl-stabilized, stratified flame at atmospheric conditions. The objectives are to demonstrate that the technology increases both the laminar and turbulent flame speeds, and modifies the chemical kinetics, enhancing the flame-stability at lean mixtures. The study combines experimental investigations using hydroxyl (OH) and formaldehyde (CH2O) Planar Laser-Induced Fluorescence (PLIF) and numerical simulations using finite rate chemistry Large Eddy Simulations (LES). The reaction mechanism is based on a methane (CH4)-air skeletal mechanism expanded with sub-mechanisms for ozone, singlet oxygen, chemionization, electron impact dissociation, ionization and attachment. The experimental and computational results show similar trends, and are used to demonstrate and explain some significant aspects of microwave-enhanced combustion. Both simulation and experimental studies are performed close to lean blow off conditions. In the simulations, the flame is gradually subjected to increasing reduced electric field strengths, resulting in a wider flame that stabilizes nearer to the burner nozzle. Experiments are performed at two equivalence ratios, where the leaner case absorbs up to more than 5% of the total flame power. Data from experiments reveal trends similar to simulated results with increased microwave absorption.

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keywords
Large eddy simulations, Laser-induced fluorescence, Plasma-assisted combustion, Turbulent combustion
in
Proceedings of the Combustion Institute2000-01-01+01:00
volume
36
issue
3
pages
4121 - 4128
publisher
Elsevier
external identifiers
  • scopus:84998772437
  • wos:000393412600088
ISSN
1540-7489
DOI
10.1016/j.proci.2016.06.164
language
English
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yes
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5f320919-688e-4e9b-8351-13411e0ef77f
date added to LUP
2017-02-17 12:28:36
date last changed
2018-01-07 11:50:41
@article{5f320919-688e-4e9b-8351-13411e0ef77f,
  abstract     = {<p>Irradiating a flame by microwave radiation is one of several plasma-assisted combustion (PAC) technologies that can be used to modify the combustion chemical kinetics in order to improve flame-stability and to delay lean blow-out. One practical implication is that engines may be able to operate with leaner fuel mixtures and have an improved fuel flexibility capability including biofuels. In addition, this technology may assist in reducing thermoacoustic instabilities that may severely damage the engine and increase emission production. To examine microwave-assisted combustion a combined experimental and computational study of microwave-assisted combustion is performed for a lean, turbulent, swirl-stabilized, stratified flame at atmospheric conditions. The objectives are to demonstrate that the technology increases both the laminar and turbulent flame speeds, and modifies the chemical kinetics, enhancing the flame-stability at lean mixtures. The study combines experimental investigations using hydroxyl (OH) and formaldehyde (CH<sub>2</sub>O) Planar Laser-Induced Fluorescence (PLIF) and numerical simulations using finite rate chemistry Large Eddy Simulations (LES). The reaction mechanism is based on a methane (CH<sub>4</sub>)-air skeletal mechanism expanded with sub-mechanisms for ozone, singlet oxygen, chemionization, electron impact dissociation, ionization and attachment. The experimental and computational results show similar trends, and are used to demonstrate and explain some significant aspects of microwave-enhanced combustion. Both simulation and experimental studies are performed close to lean blow off conditions. In the simulations, the flame is gradually subjected to increasing reduced electric field strengths, resulting in a wider flame that stabilizes nearer to the burner nozzle. Experiments are performed at two equivalence ratios, where the leaner case absorbs up to more than 5% of the total flame power. Data from experiments reveal trends similar to simulated results with increased microwave absorption.</p>},
  author       = {Ehn, A. and Petersson, P. and Zhu, J. J. and Li, Z. S. and Aldén, M. and Nilsson, E. J K and Larfeldt, J. and Larsson, A. and Hurtig, T. and Zettervall, N. and Fureby, C.},
  issn         = {1540-7489},
  keyword      = {Large eddy simulations,Laser-induced fluorescence,Plasma-assisted combustion,Turbulent combustion},
  language     = {eng},
  number       = {3},
  pages        = {4121--4128},
  publisher    = {Elsevier},
  series       = {Proceedings of the Combustion Institute2000-01-01+01:00},
  title        = {Investigations of microwave stimulation of a turbulent low-swirl flame},
  url          = {http://dx.doi.org/10.1016/j.proci.2016.06.164},
  volume       = {36},
  year         = {2017},
}