Investigation of laminar flame speeds of CH4/O2/CO2 mixtures at ordinary pressure and kinetic simulation

The laminar flame speeds of CH4/O2/CO2 mixtures in atmospheric conditions (300 K and 1 atm) were studied using a Bunsen burner. The surface area methodology based on images of flame was performed to obtain the laminar flame speeds for a range of equivalence ratios (from 0.6 to 1.4, step 0.1), oxygen concentrations (from 25% to 35%). The experimental data were compared to numerical flame speed predictions which was based on GRI-Mech.ver 3.0 mechanism using a Chemkin package. The results showed that the maximum of flame speeds appeared at the stoichiometric ratio. With an increase in O2 concentration, the flame speeds increased. The effect of CO2 dilution was also investigated with experimental measurements, flame structure analysis and reaction pathway analysis from calculation. In premixed CH4/O2/CO2 flame, the combustion reactants, important intermediate and products concentration became lower and the flame thickness became thicker compared to CH4/O2/N2 mixtures. The major oxidation pathway of CH4/O2/CO2 remain unchanged but contribution rates of major intermediates formation have changed a lot. In addition, a part of secondary chemical pathways have changed.