Correlations for the laminar burning velocity and burned gas Markstein length of methane-air mixtures diluted with flue gases at high temperatures and pressures

Laminar burning velocity and burned gas Markstein length correlations have been developed from the measurements of spherically expanding methane-air flames under constant pressure at 1-5 bar, 373-473 K, and with 0-15% dilution. A dilution mixture consisting of 71.49% N-2 + 19.01% H2O + 9.50% CO2 by mole, representing the actual principal residual concentrations from stoichiometric methane-air combustion, was used. Only equivalence ratios where the laminar burning velocity was greater than 15 cm/s were reported, due to the buoyancy effect limitation. The physical and chemical aspects of changes in the laminar burning velocity and flame front stability due to changes in temperature, pressure, equivalence and dilution ratios were discussed in detail. Experimentally measured laminar burning velocity data and a newly developed correlation in this study were compared with numerical results obtained from several chemical mechanisms as well as experimental data from the literature.