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Fourth International Symposium on Turbulence and Shear Flow Phenomena
June, 27-29, 2005, Marriot Hotel, Williamsburg, Virginia, USA

DOI: 10.1615/TSFP4

ANALYSIS OF KINETIC MECHANISM PERFORMANCE IN CONDITIONAL MOMENT CLOSURE MODELLING OF TURBULENT, NON-PREMIXED METHANE FLAMES

pages 623-628
DOI: 10.1615/TSFP4.1050
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Краткое описание

Presented are results obtained from the application of a first-order Conditional Moment Closure (CMC) approach to the modelling of two methane flames of differing geometries. Predictions are based upon a second-moment turbulence and scalar-flux closure, and are supplemented with a wide range of full and reduced chemical kinetic mechanisms, ranging from a simple 12-step to a complex 325-step mechanism. Included with an analysis of the full scheme performances is an appraisal of the behaviour of their derivatives, obtained from mechanism reduction techniques. Despite extensive studies of the predictive ability of such schemes under laminar flame conditions, this is the first time, to the authors' knowledge, that a systematic evaluation has been performed for turbulent reacting flows.
The motivation of these works lies in the authors' current developments of higher-order elliptic CMC methods for application to practical combustion devices. As a precursor, the study presented was undertaken to analyse the practicality of incorporating kinetic models of varying complexity into calculation procedures, and to make comparison of their performance.
The findings of the paper reflect upon the impact that selection of chemical kinetics has upon subsequent calculations, and conclusions include that although the application of reduced schemes is more than adequate to reproduce experimentally derived data, the selection of the parent mechanism is of paramount importance to the prediction of minor species. Although most widely used schemes are very well documented and validated, their performances vary considerably. Thus, careful consideration must be made as to their application and origins during the evaluation of any combustion model.

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