Assessment of the applicability of conditional moment closure to a lifted turbulent flame: first order model

This paper presents the results of a detailed study of Conditional Moment Closure (CMC) applied to a lifted turbulent flame. The objectives are to find out how first order, radially averaged CMC can represent a lifted flame and which mechanism of flame stabilization can be described by this modeling...

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Bibliographic Details
Published in:Combustion and flame 2003, Vol.132 (1), p.102-114
Main Authors: Devaud, C.B., Bray, K.N.C.
Format: Article
Language:English
Subjects:
Applied sciences
CMC
Combustion. Flame
Energy
Energy. Thermal use of fuels
Exact sciences and technology
First order
Hydrogen
Lifted turbulent flame
Theoretical studies
Theoretical studies. Data and constants. Metering
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Summary:This paper presents the results of a detailed study of Conditional Moment Closure (CMC) applied to a lifted turbulent flame. The objectives are to find out how first order, radially averaged CMC can represent a lifted flame and which mechanism of flame stabilization can be described by this modeling method. As a first stage of this study of CMC applied to ignition/extinction phenomena, turbulence and combustion calculations are decoupled, that is, the effect of turbulence upon combustion is included but the heat released due to combustion is not part of the turbulence calculations. A 10-step chemical mechanism is used to predict rates of reaction in hydrogen-air mixtures. Attention is focused on the lift-off region of the flame which is commonly considered as a cold flow. Comparison with published experimental data shows that the lift-off height is accurately predicted at 14 mm. The Favre averaged radial profiles of temperature and species mole fractions are also compared with the experimental values. The computational results agree well with the experimental points for lean mixtures but the temperatures are overpredicted in rich mixtures close to the centerline. Some of the current flame stabilization mechanisms are discussed in the context of the present results. Simple elliptic first-order CMC is shown to be able to reproduce some of these mechanisms. Modeling accurately the axial transport is a key factor to these simulations.
ISSN:0010-2180
1556-2921
DOI:10.1016/S0010-2180(02)00427-3