Laminar flame speeds and ignition delay times of methane-air mixtures at elevated temperatures and pressures

Measurements on laminar flame speeds and ignition delay times of methane/air mixtures at elevated pressures and temperatures were carried out in a constant volume bomb and shock tube. The performances of GRI Mech 3.0, USC Mech II, and Aramco Mech 1.3 mechanisms were also evaluated from the data obtained. Results showed that the measured laminar flame speeds from the constant volume bomb by the linear method are slightly higher than those from the counter flow flame at rich mixtures and lower at lean mixtures. At rich mixtures, the laminar flame speeds with linear method are higher than that with non-linear method. The available mechanisms give slight overprediction to the constant volume bomb data at lean mixtures, and large underprediction at rich mixtures at elevated temperatures and pressures. Overall reaction order decreases and then increases with the rising of pressure from 0.1 to 10.0 MPa because of the chain reaction mechanism. For the ignition delay times, the three mechanisms are in good accordance with the experimental data of lean and stoichiometric mixtures at atmospheric pressure, while the discrepancy between calculation and measurement is increased at elevated pressures. These mechanisms seem to lack good sensitivity to the rich mixtures, especially at elevated pressures. Correlations for laminar burning velocities and ignition delay time of methane-air mixtures are provided.