Modeling stretched methane-air flame growth

In this study, a one-dimensional, spherical, adiabatic, laminar, premixed flame is considered. Reactant conditions include methane-air mixture having fuel/air equivalence ratios of 0.6 to 1.4, pressures of 1 to 3 atm and temperatures of 300 to 500 K. The underlying unstretched laminar flame characteristics including the unstretched laminar flame speed, adiabatic flame temperature and gas density ratio are calculated using CHEMKIN 4.1 with GRI mechanism 3.0, dealing with 325 reactions and 53 species. Stretched flame speeds are then deduced by invoking Markstein theory. These results are extended to investigate the effect of confinement on flame propagation inside a closed chamber. For the methane-air mixture conditions considered, Stretch always decreases the flame speed, and the largest reduction occurs when the flame is the smallest. Increasing initial unburned gas temperature lessens the flame speed reduction due to stretch, while moderate changes in pressure do not influence the flame speed-flame stretch relationship in any significant manner