Propagation of Laminar Premixed Flames of CH4/H2/Air Mixtures at Elevated Temperatures

The laminar flame speeds of CH4/H2/air mixtures were experimentally studied at elevated initial temperatures using the Bunsen burner method combined with the Schlieren technique, and the corresponding cases were computed using CHEMKIN-PRO. The effect of initial temperatures on the propagation characteristics of laminar premixed flames was discussed from the perspectives of thermodynamics and chemical kinetics. The results show that the laminar flame speeds of the mixtures at 293-500 K can be predicted well by GRI-3.0 mechanism. The greater increments of laminar flame speeds of mixtures are presented at higher H2 fractions under all tested initial temperatures. The laminar flame speeds and adiabatic flame temperatures of mixtures almost linearly increase with a growth of initial temperatures with the same equivalence ratios. With the rise of initial temperatures, the dominant promotion of H+O2=O+OH on the mass burning rates of mixtures can be enhanced by the great growth of the mole fractions of H radicals. Therefore, the laminar flame speed of CH4/H2/air mixtures significantly increases at elevated temperatures. © 2021, Editorial Department of Journal of Northeastern University. All right reserved.