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Rate-ratio asymptotic analysis of the influence of addition of carbon monoxide on the structure and mechanisms of extinction of nonpremixed methane flames with comparison to experiments

Seshadri, Kalyanasundaram and Bai, Xue Song LU (2017) In Combustion and Flame 175. p.107-117
Abstract

Rate-ratio asymptotic (RRA) analysis is carried out to elucidate the influence of carbon monoxide on the structure and critical conditions of 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 (N2). The other stream, called the oxidizer stream, is a mixture of oxygen (O2), and N2. Carbon monoxide (CO) is added either to the oxidizer stream or to the fuel stream. Chemical reactions, represented by four global steps, are presumed to take place in a thin reaction zone. To the leading order the reactants,... (More)

Rate-ratio asymptotic (RRA) analysis is carried out to elucidate the influence of carbon monoxide on the structure and critical conditions of 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 (N2). The other stream, called the oxidizer stream, is a mixture of oxygen (O2), and N2. Carbon monoxide (CO) is added either to the oxidizer stream or to the fuel stream. Chemical reactions, represented by four global steps, are presumed to take place in a thin reaction zone. To the leading order the reactants, CH4, O2, and CO are completely consumed in the reaction zone. On either side of this thin reaction zone, the flow field is inert. These inert regions represent the outer structure of the flame. The outer structures provide 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. The scalar dissipation rate at extinction is predicted from results of the asymptotic analysis and compared with previous measurements and computational predictions using detailed chemistry. The predictions of the asymptotic analysis are found to agree well with the experimental data for CO addition to the fuel stream, and for small amounts of CO addition to the oxidizer stream. For large amounts of CO addition to the oxidizer stream, the approximations introduced in the asymptotic analysis become inaccurate. A key finding is that with increasing amounts of CO added to the oxidizer stream the scalar dissipation rate at extinction first increases and then decreases. It is attributed to changes in location of the inner layer within the reaction zone.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Carbon monoxide addition, Extinction, Flame structure, Methane flames, Rate-ratio asymptotic analysis
in
Combustion and Flame
volume
175
pages
11 pages
publisher
Elsevier
external identifiers
  • scopus:85002199061
  • wos:000390834100010
ISSN
0010-2180
DOI
10.1016/j.combustflame.2016.08.029
language
English
LU publication?
yes
id
d70c134d-f1dc-463a-9bc9-a698e236cf61
date added to LUP
2017-03-20 13:28:25
date last changed
2017-09-18 11:33:20
@article{d70c134d-f1dc-463a-9bc9-a698e236cf61,
  abstract     = {<p>Rate-ratio asymptotic (RRA) analysis is carried out to elucidate the influence of carbon monoxide on the structure and critical conditions of 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 (CH<sub>4</sub>) and nitrogen (N<sub>2</sub>). The other stream, called the oxidizer stream, is a mixture of oxygen (O<sub>2</sub>), and N<sub>2</sub>. Carbon monoxide (CO) is added either to the oxidizer stream or to the fuel stream. Chemical reactions, represented by four global steps, are presumed to take place in a thin reaction zone. To the leading order the reactants, CH<sub>4</sub>, O<sub>2</sub>, and CO are completely consumed in the reaction zone. On either side of this thin reaction zone, the flow field is inert. These inert regions represent the outer structure of the flame. The outer structures provide 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. The scalar dissipation rate at extinction is predicted from results of the asymptotic analysis and compared with previous measurements and computational predictions using detailed chemistry. The predictions of the asymptotic analysis are found to agree well with the experimental data for CO addition to the fuel stream, and for small amounts of CO addition to the oxidizer stream. For large amounts of CO addition to the oxidizer stream, the approximations introduced in the asymptotic analysis become inaccurate. A key finding is that with increasing amounts of CO added to the oxidizer stream the scalar dissipation rate at extinction first increases and then decreases. It is attributed to changes in location of the inner layer within the reaction zone.</p>},
  author       = {Seshadri, Kalyanasundaram and Bai, Xue Song},
  issn         = {0010-2180},
  keyword      = {Carbon monoxide addition,Extinction,Flame structure,Methane flames,Rate-ratio asymptotic analysis},
  language     = {eng},
  month        = {01},
  pages        = {107--117},
  publisher    = {Elsevier},
  series       = {Combustion and Flame},
  title        = {Rate-ratio asymptotic analysis of the influence of addition of carbon monoxide on the structure and mechanisms of extinction of nonpremixed methane flames with comparison to experiments},
  url          = {http://dx.doi.org/10.1016/j.combustflame.2016.08.029},
  volume       = {175},
  year         = {2017},
}