Accuracy and Computational Efficiency Study of Reduced Chemical Kinetic Mechanisms for Methane-Air Combustion

Cesar Celis¹; Luís Fernando Figueira da Silva¹

¹ Pontifícia Universidade Católica do Rio de Janeiro

doi:10.20906/CPS/COB-2015-0134

Resumo

Accurate predictions of minor chemical species and radicals are crucial for determining the production of pollutants such as soot. Reduced chemical kinetic mechanisms compromise their accuracy in favor of a lower computational cost. When using these reduced mechanisms then, it is important to asses both the accuracy of the results obtained, and the amount of computational time saved. This works describes such an assessment of seven reduced chemical kinetic mechanisms utilized for methane-air combustion. The reduced mechanisms evaluated involve different numbers of chemical species and reactions. The assessment is carried out using partially stirred reactors, with and without in situ adaptive tabulation-based chemistry acceleration techniques, by comparing the results with detailed chemical kinetics baseline computations. In terms of accuracy, the main results show that in general major species such as carbon dioxide are predicted reasonably well (~0.5-10% error) by the reduced mechanisms considered. Important differences between detailed and reduced mechanisms results (~5-65%) are observed however when predicting minor species such as acetylene. The in situ adaptive tabulation technique used in this work leads to further reductions in the accuracy of the minor species predicted, i.e., to further increases in prediction errors (~0-90%). Regarding the computational cost, the results show that savings of up to 80% can be obtained when using the reduced mechanisms analyzed. The use of chemistry acceleration techniques results in further cost reductions of about 40%. Overall the results obtained in this work emphasize the need of carefully selecting the reduced mechanism that is more suitable for a given application.

Palavras-chave: Reduced chemical kinetic mechanisms; Methane-air combustion; Partially stirred reactors