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Flame structure analysis for categorization of lean premixed CH4/air and H-2/air flames at high Karlovitz numbers: Direct numerical simulation studies

Carlsson, Henning LU ; Yu, Rixin LU and Bai, Xue-Song LU (2015) In Proceedings of the Combustion Institute 35. p.1425-1432
Abstract
This paper presents direct numerical simulation studies of lean CH4/air and H-2/air flames at high Karlovitz numbers utilizing detailed chemical kinetic mechanisms. Identical Karlovitz numbers are applied to the two flames; however, as the interaction of high turbulence intensity small scale structures with the reaction zones is considered, a significant difference in the effect of the turbulence structures on the inner reaction layer is observed. The heat release rate layer as well as layers of different species reaction rates is found to be more distributed for the H-2/air flame compared with those in the CH4/air flame, owing to the difference in the Kolmogorov length scale and the differential diffusion effects. A modified,... (More)
This paper presents direct numerical simulation studies of lean CH4/air and H-2/air flames at high Karlovitz numbers utilizing detailed chemical kinetic mechanisms. Identical Karlovitz numbers are applied to the two flames; however, as the interaction of high turbulence intensity small scale structures with the reaction zones is considered, a significant difference in the effect of the turbulence structures on the inner reaction layer is observed. The heat release rate layer as well as layers of different species reaction rates is found to be more distributed for the H-2/air flame compared with those in the CH4/air flame, owing to the difference in the Kolmogorov length scale and the differential diffusion effects. A modified, species-specific Karlovitz number is proposed, where the chemical time scale in the definition is a characteristic speciesspecific chemical time scale, which is obtained from stationary 1D simulations. The difference between the two flames for different intermediate species corresponds well to the difference in the obtained species-specific Karlovitz numbers. A validation study of the species-specific Karlovitz number is also conducted, where a turbulent effective chemical time scale is quantified for different intermediate species from instantaneous data sets. It is shown that in the preheat zone and reaction zone of the flame, the ratio between the laminar and turbulent chemical time scales of intermediate species corresponds well to the species-specific Karlovitz numbers for the two different flames. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Turbulent premixed combustion, High Karlovitz number, Direct numerical, simulations, Detailed chemical kinetics, Distributed flame structure
in
Proceedings of the Combustion Institute
volume
35
pages
1425 - 1432
publisher
Elsevier
external identifiers
  • wos:000348048800035
  • scopus:84947543745
ISSN
1540-7489
DOI
10.1016/j.proci.2014.09.002
language
English
LU publication?
yes
id
02402c8d-15ff-482f-840f-6d81db4cf375 (old id 5204244)
date added to LUP
2015-03-25 14:43:06
date last changed
2017-06-25 03:24:42
@article{02402c8d-15ff-482f-840f-6d81db4cf375,
  abstract     = {This paper presents direct numerical simulation studies of lean CH4/air and H-2/air flames at high Karlovitz numbers utilizing detailed chemical kinetic mechanisms. Identical Karlovitz numbers are applied to the two flames; however, as the interaction of high turbulence intensity small scale structures with the reaction zones is considered, a significant difference in the effect of the turbulence structures on the inner reaction layer is observed. The heat release rate layer as well as layers of different species reaction rates is found to be more distributed for the H-2/air flame compared with those in the CH4/air flame, owing to the difference in the Kolmogorov length scale and the differential diffusion effects. A modified, species-specific Karlovitz number is proposed, where the chemical time scale in the definition is a characteristic speciesspecific chemical time scale, which is obtained from stationary 1D simulations. The difference between the two flames for different intermediate species corresponds well to the difference in the obtained species-specific Karlovitz numbers. A validation study of the species-specific Karlovitz number is also conducted, where a turbulent effective chemical time scale is quantified for different intermediate species from instantaneous data sets. It is shown that in the preheat zone and reaction zone of the flame, the ratio between the laminar and turbulent chemical time scales of intermediate species corresponds well to the species-specific Karlovitz numbers for the two different flames. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.},
  author       = {Carlsson, Henning and Yu, Rixin and Bai, Xue-Song},
  issn         = {1540-7489},
  keyword      = {Turbulent premixed combustion,High Karlovitz number,Direct numerical,simulations,Detailed chemical kinetics,Distributed flame structure},
  language     = {eng},
  pages        = {1425--1432},
  publisher    = {Elsevier},
  series       = {Proceedings of the Combustion Institute},
  title        = {Flame structure analysis for categorization of lean premixed CH4/air and H-2/air flames at high Karlovitz numbers: Direct numerical simulation studies},
  url          = {http://dx.doi.org/10.1016/j.proci.2014.09.002},
  volume       = {35},
  year         = {2015},
}