Prediction of laminar premixed methane-air flames using a reduced kinetic mechanism

A reduced, quasi-global, four-step kinetic mechanism for premixed methane/air combustion, developed by Paczko et al., is adapted for use in predicting the multi-dimensional laminar flames employed in domestic appliances. The elementary reactions, and their rates, used as the basis of the reduced scheme are modified to bring predictions of both the elementary and reduced mechanisms closer to recent burning velocity data for methane/air mixtures and, in particular, to reduce predicted peak burning velocities. Comparisons with the data demonstrate that, over the equivalence ratio range of interest (0.8 less than or equal to phi less than or equal to 1.2), both the adapted schemes are in closer accord with experimental observations of burning velocity than the original formulations. In order to further assess the usefulness of the reduced scheme for predicting laminar flame structures in both idealised and practically relevant geometries, the mechanism is applied to the computation of both one- and two-dimensional, laminar flames. Comparisons with available data on one-dimensional flames and predictions of a full kinetic mechanism (GRI-Mech) demonstrate that the adapted four-step mechanism is in good agreement with that data and closely reproduces the predictions obtained using the full mechanism. In addition, predictions of the reduced scheme are demonstrated to be in reasonable agreement with data for CO and temperature along the centre-line of various stoichiometry, two-dimensional flames, thereby supporting use of the scheme in performing calculations for more complex burner configurations.