Abstract: The transmission speeds of laminar flames of H₂/CH₄/air mixtures with CO₂/N₂ dilution were experimentally studied using the Bunsen burner method incorporating the schlieren technique. To thoroughly investigate the diluted effect of CO₂/N₂ on laminar premixed flames of H₂/CH₄/air mixtures， the adiabatic flame temperatures， sensitivities of the mixtures with various CO₂/N₂ dilution ratios and the mole fractions of vital radicals were calculated using GRI-3.0 mechanism. The research results showed that GRI-3.0 mechanism provided better estimates of the transmission speeds of hythane flames; laminar flame speeds and adiabatic flame temperatures decreased with the growth of CO₂/N₂ dilution ratios. Compared with N₂， CO₂ presented the stronger thermal effect and chemical kinetics effect on the decrease of the laminar flame speeds of diluted hythane. With the increase of CO₂ dilution ratios， the dominant promotion of the oxidation reaction H+O₂O+OH on the mass burning rates of mixtures can be inhibited by the significant reductions of H radicals. Therefore， the laminar flame speed of mixtures remarkable decreased with the growth of CO₂ rations.

Key words: Bunsen burner, laminar flame speed, CO₂/N₂ dilution, sensitivity analysis, vital radical