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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

Seshadri, Kalyanasundaram and Bai, Xue Song LU (2017) 10th U.S. National Combustion Meeting
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), carbon monoxide (CO) and N2. 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, are completely consumed in the reaction... (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), carbon monoxide (CO) and N2. 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, are completely consumed in the reaction zone, while there is leakage of CO from the reaction zone to the leading order. 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 oxidation layer is presumed to be made of two sub-layers. In one sub-layer consumption of O2 takes place, while in the other layer H2 is presumed to maintain steady-state. The scalar-dissipation rate at extinction is predicted from results of the asymptotic analysis and are found to qualitatively agree well with measurements. 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 reaction zone within the reaction zone.

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2018-07-09 10:38:31
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@misc{4f65fb0e-d435-4ff7-85e1-ad361c2ad749,
  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>), carbon monoxide (CO) and N<sub>2</sub>. 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>, are completely consumed in the reaction zone, while there is leakage of CO from the reaction zone to the leading order. 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 oxidation layer is presumed to be made of two sub-layers. In one sub-layer consumption of O<sub>2</sub> takes place, while in the other layer H<sub>2</sub> is presumed to maintain steady-state. The scalar-dissipation rate at extinction is predicted from results of the asymptotic analysis and are found to qualitatively agree well with measurements. 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 reaction zone within the reaction zone.</p>},
  author       = {Seshadri, Kalyanasundaram and Bai, Xue Song},
  language     = {eng},
  title        = {Rate-ratio asymptotic analysis of the influence of addition of carbon monoxide on the structure and mechanisms of extinction of nonpremixed methane flames},
  year         = {2017},
}