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RATE-RATIO ASYMPTOTIC ANALYSIS OF THE INFLUENCE OF ADDITION OF HYDROGEN ON THE STRUCTURE AND MECHANISMS OF EXTINCTION OF NONPREMIXED METHANE FLAMES

Seshadri, Kalyanasundaram and Bai, Xue-Song LU (2015) In Combustion Science and Technology 187(1-2). p.3-26
Abstract
Rate-ratio asymptotic analysis is carried out to elucidate the influence of hydrogen on the structure and critical conditions for extinction of nonpremixed methane flames. Steady, axisymmetric, laminar flow of two counterflowing streams toward a stagnation plane is considered. One stream, called the fuel stream is made up of a mixture of methane (CH4) and nitrogen (N-2). The other stream, called the oxidizer stream, is a mixture of oxygen (O-2), and N-2. Hydrogen (H-2) is added either to the oxidizer stream or to the fuel stream. A reduced mechanism of four global steps is employed in the analysis. Chemical reactions are presumed to take place in a thin reaction zone that is established in the vicinity of the stagnation plane. On either... (More)
Rate-ratio asymptotic analysis is carried out to elucidate the influence of hydrogen on the structure and critical conditions for extinction of nonpremixed methane flames. Steady, axisymmetric, laminar flow of two counterflowing streams toward a stagnation plane is considered. One stream, called the fuel stream is made up of a mixture of methane (CH4) and nitrogen (N-2). The other stream, called the oxidizer stream, is a mixture of oxygen (O-2), and N-2. Hydrogen (H-2) is added either to the oxidizer stream or to the fuel stream. A reduced mechanism of four global steps is employed in the analysis. Chemical reactions are presumed to take place in a thin reaction zone that is established in the vicinity of the stagnation plane. On either side of this thin reaction zone, the flow field is inert. These inert regions represent the outer structure of the flame. The reactants, CH4, O-2, and H-2 are completely consumed at the reaction zone. The outer structure is constructed employing a previously developed Burke-Schumann (flame-sheet) formulation. It provides matching conditions required for predicting the structure of the reaction zone. In the reaction zone, chemical reactions are presumed to take place in two layers-the inner layer and the oxidation layer. In the inner layer fuel (methane) is consumed and the intermediate species hydrogen and carbon monoxide are formed. These intermediate species and added hydrogen are oxidized in the oxidation layer to water vapor and carbon dioxide. Critical conditions of extinction were predicted from results of the asymptotic analysis and found to agree well with previous measurements. Addition of hydrogen to methane flames promotes combustion by delaying extinction. An important finding of the asymptotic analysis is that the mechanisms by which hydrogen promotes combustion when it is added to the oxidizer stream is different from that when it is added to the fuel stream. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Extinction, Hydrogen enrichment, Methane/air non-premixed flame, Rate-ratio asymptotic analysis, Scalar dissipation rate
in
Combustion Science and Technology
volume
187
issue
1-2
pages
3 - 26
publisher
Taylor & Francis
external identifiers
  • wos:000346263500002
  • scopus:84961300676
ISSN
1563-521X
DOI
10.1080/00102202.2014.971948
language
English
LU publication?
yes
id
391c5e0c-75c9-43b7-9ecb-551a322543c1 (old id 4941534)
date added to LUP
2015-01-27 16:39:37
date last changed
2017-03-19 03:21:18
@article{391c5e0c-75c9-43b7-9ecb-551a322543c1,
  abstract     = {Rate-ratio asymptotic analysis is carried out to elucidate the influence of hydrogen on the structure and critical conditions for extinction of nonpremixed methane flames. Steady, axisymmetric, laminar flow of two counterflowing streams toward a stagnation plane is considered. One stream, called the fuel stream is made up of a mixture of methane (CH4) and nitrogen (N-2). The other stream, called the oxidizer stream, is a mixture of oxygen (O-2), and N-2. Hydrogen (H-2) is added either to the oxidizer stream or to the fuel stream. A reduced mechanism of four global steps is employed in the analysis. Chemical reactions are presumed to take place in a thin reaction zone that is established in the vicinity of the stagnation plane. On either side of this thin reaction zone, the flow field is inert. These inert regions represent the outer structure of the flame. The reactants, CH4, O-2, and H-2 are completely consumed at the reaction zone. The outer structure is constructed employing a previously developed Burke-Schumann (flame-sheet) formulation. It provides matching conditions required for predicting the structure of the reaction zone. In the reaction zone, chemical reactions are presumed to take place in two layers-the inner layer and the oxidation layer. In the inner layer fuel (methane) is consumed and the intermediate species hydrogen and carbon monoxide are formed. These intermediate species and added hydrogen are oxidized in the oxidation layer to water vapor and carbon dioxide. Critical conditions of extinction were predicted from results of the asymptotic analysis and found to agree well with previous measurements. Addition of hydrogen to methane flames promotes combustion by delaying extinction. An important finding of the asymptotic analysis is that the mechanisms by which hydrogen promotes combustion when it is added to the oxidizer stream is different from that when it is added to the fuel stream.},
  author       = {Seshadri, Kalyanasundaram and Bai, Xue-Song},
  issn         = {1563-521X},
  keyword      = {Extinction,Hydrogen enrichment,Methane/air non-premixed flame,Rate-ratio asymptotic analysis,Scalar dissipation rate},
  language     = {eng},
  number       = {1-2},
  pages        = {3--26},
  publisher    = {Taylor & Francis},
  series       = {Combustion Science and Technology},
  title        = {RATE-RATIO ASYMPTOTIC ANALYSIS OF THE INFLUENCE OF ADDITION OF HYDROGEN ON THE STRUCTURE AND MECHANISMS OF EXTINCTION OF NONPREMIXED METHANE FLAMES},
  url          = {http://dx.doi.org/10.1080/00102202.2014.971948},
  volume       = {187},
  year         = {2015},
}