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FIRST-ORDER CONDITIONAL MOMENT CLOSURE MODELLING OF TURBULENT JET DIFFUSION FLAMES OF METHANE

Michael Fairweather
School of Chemical and Process Engineering, University of Leeds, Leeds, LS2 9JT, UK

Robert M. Woolley
School of Chemical and Process Engineering, University of Leeds, Leeds, LS2 9JT, United Kingdom

Resumo

A first-order conditional moment closure (CMC) model, together with fluid flow predictions based on both k-ε and second-moment turbulence closures, is used in the prediction of turbulent jet diffusion flames of methane, with chemical kinetic information supplied from the GRI-Mech 2.11 scheme. To provide an assessment of the ability these methods to predict a range of flames, comparisons are made with experimental data on three piloted and two un-piloted flames. It is concluded that first-order CMC modelling is capable of yielding reliable predictions for flames with little or no extinction effects, with the only exception being NO that is over predicted at most locations within the flames. Results derived using the two turbulence closures are in general in close accord, with calculations for flames that exhibit extinction effects demonstrating a gradual deterioration of results with increasing Reynolds number, pointing to the requirement for second-order CMC modelling as such effects become significant. Anomalies are observed in regard to predictions of NO which is significantly over predicted for the piloted flames, but only slightly over predicted for the un-piloted flames. These results demonstrate a requirement not only for second-order CMC modelling, but also a need to examine the application of different kinetic schemes, including a detailed investigation of NO chemistry kinetic mechanisms.