- Najm, H. N. and Knio, O. M. and Paul, P. H., Role of transport properties in the transient response of premixed methane/air flames,
PROCEEDINGS OF THE COMBUSTION INSTITUTE, vol. 29
pp. 1713--1720 .
(last updated on 2011/07/05)
We compute the detailed interaction of a premixed methane/air flame with a two-dimensional counter-rotating vortex pair using mixture-averaged transport properties for stoichiometric and rich N-2-diluted reactants. We present comparisons of the observed flame structure and transient flame response with results using temperature-tabulated properties, where dependence on mixture composition is neglected. We find that the significance of using the more accurate transport model depends on the particular aspect of transient flame response under consideration. While the effect on global flame response is generally small, we do observe quantitative differences of as much as 30\%-45\% in the extent of transient accumulation of some species on the reactants side of the flame. On the other hand, no significant qualitative differences are observed in the transient flame response. We examine and discuss these observations with regard to available experimental data in a premised methanie/air V-flame under the same mixture conditions as the computations and with similar flow-flame evolution. We find that the earlier-reported disagreements between computed and experimentally observed transient OH and CH responses are not much improved with the use of the more accurate mixture-averaged transport. This suggests that the root of the disagreement is not the transport model but the chemical mechanism and/or rate constants therein. Further work is needed to identify necessary improvements in the mechanism to achieve better agreement with the experiments.