Effect of N2/CO2 dilution on laminar burning velocity of H2–CO–O2 oxy-fuel premixed flame

• Laminar burning velocities of H2–CO–O2–N2 (CO2) mixtures were measured.
• Correlations between dilution fraction and laminar burning velocity reduction rate were obtained.
• Equations were proposed to predict the laminar burning velocities of H2–CO fuels.

The dilution effect of N2/CO2 on the laminar burning velocity of H2–CO–O2 mixtures was investigated. The dilution fraction of N2 and CO2 in the unburned mixtures varied from 0% to 70% and 0%–50%, respectively, and H2 content in H2–CO fuels altered from 5% to 100%. All the studies were carried out at standard laboratory conditions (1 atm, 298 K) with equivalence ratio changing from 0.6 to 2.0. The Heat flux method and OH-PLIF (Planar Laser-Induced Fluorescence) based Bunsen flame method were employed to measure the laminar burning velocities. The Li mechanism was used in simulations, due to its good prediction of laminar burning velocities. Based on extensive experimental results, the correlations between dilution fraction and laminar burning velocity reduction rate were analyzed. It was found that, for a given dilution fraction, the reduction in laminar burning velocity is largely independent equivalence ratio and fuel H2–CO mole fraction. This behavior does not extend to all fuels, e.g. methane. Exploiting the lack of dependence on equivalence ratio and fuel composition, a unified correlation equation was proposed which can be used to predict the laminar burning velocities of H2–CO fuels for given fuel component, dilution rate and equivalence ratio.