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Direct numerical simulation of lean premixed CH4/air and H-2/air flames at high Karlovitz numbers

Carlsson, Henning LU ; Yu, Rixin LU and Bai, Xue-Song LU (2014) In International Journal of Hydrogen Energy 39(35). p.20216-20232
Abstract
Three-dimensional direct numerical simulation with detailed chemical kinetics of lean premixed CH4/air and H-2/air flames at high Karlovitz numbers (Ka similar to 1800) is carried out. It is found that the high intensity turbulence along with differential diffusion result in a much more rapid transport of H radicals from the reaction zone to the low temperature unburned mixtures (similar to 500 K) than that in laminar flamelets. The enhanced concentration of H radicals in the low temperature zone drastically increases the reaction rates of exothermic chain terminating reactions (e.g., H + O-2+M = HO2 + M in lean H-2/air flames), which results in a significantly enhanced heat release rate at low temperatures. This effect is observed in both... (More)
Three-dimensional direct numerical simulation with detailed chemical kinetics of lean premixed CH4/air and H-2/air flames at high Karlovitz numbers (Ka similar to 1800) is carried out. It is found that the high intensity turbulence along with differential diffusion result in a much more rapid transport of H radicals from the reaction zone to the low temperature unburned mixtures (similar to 500 K) than that in laminar flamelets. The enhanced concentration of H radicals in the low temperature zone drastically increases the reaction rates of exothermic chain terminating reactions (e.g., H + O-2+M = HO2 + M in lean H-2/air flames), which results in a significantly enhanced heat release rate at low temperatures. This effect is observed in both CH4/air and H-2/air flames and locally, the heat release rate in the low temperature zone can exceed the peak heat release rate of a laminar flamelet. The effects of chemical kinetics and transport properties on the H-2/air flame are investigated, from which it is concluded that the enhanced heat release rate in the low temperature zone is a convection-diffusion-reaction phenomenon, and to obtain it, detailed chemistry is essential and detailed transport is important. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Turbulent premixed combustion, Direct numerical simulation, High, Karlovitz number, Detailed chemistry, Differential diffusion
in
International Journal of Hydrogen Energy
volume
39
issue
35
pages
20216 - 20232
publisher
Elsevier
external identifiers
  • wos:000347017200038
  • scopus:84912559293
ISSN
1879-3487
DOI
10.1016/j.ijhydene.2014.09.173
language
English
LU publication?
yes
id
c55c0f89-05ff-4319-8b0c-ec1132ed72d3 (old id 5085342)
date added to LUP
2015-02-26 12:56:25
date last changed
2017-08-13 03:55:19
@article{c55c0f89-05ff-4319-8b0c-ec1132ed72d3,
  abstract     = {Three-dimensional direct numerical simulation with detailed chemical kinetics of lean premixed CH4/air and H-2/air flames at high Karlovitz numbers (Ka similar to 1800) is carried out. It is found that the high intensity turbulence along with differential diffusion result in a much more rapid transport of H radicals from the reaction zone to the low temperature unburned mixtures (similar to 500 K) than that in laminar flamelets. The enhanced concentration of H radicals in the low temperature zone drastically increases the reaction rates of exothermic chain terminating reactions (e.g., H + O-2+M = HO2 + M in lean H-2/air flames), which results in a significantly enhanced heat release rate at low temperatures. This effect is observed in both CH4/air and H-2/air flames and locally, the heat release rate in the low temperature zone can exceed the peak heat release rate of a laminar flamelet. The effects of chemical kinetics and transport properties on the H-2/air flame are investigated, from which it is concluded that the enhanced heat release rate in the low temperature zone is a convection-diffusion-reaction phenomenon, and to obtain it, detailed chemistry is essential and detailed transport is important. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.},
  author       = {Carlsson, Henning and Yu, Rixin and Bai, Xue-Song},
  issn         = {1879-3487},
  keyword      = {Turbulent premixed combustion,Direct numerical simulation,High,Karlovitz number,Detailed chemistry,Differential diffusion},
  language     = {eng},
  number       = {35},
  pages        = {20216--20232},
  publisher    = {Elsevier},
  series       = {International Journal of Hydrogen Energy},
  title        = {Direct numerical simulation of lean premixed CH4/air and H-2/air flames at high Karlovitz numbers},
  url          = {http://dx.doi.org/10.1016/j.ijhydene.2014.09.173},
  volume       = {39},
  year         = {2014},
}