Effect of N2/CO2 dilution on laminar burning velocity of H2-air mixtures at high temperatures

The laminar burning velocities of H2-air mixtures diluted with N2 or CO2 gas at high temperatures were obtained from planar flames observed in externally heated diverging channels. Experiments were conducted for an equivalence ratio range of 0.8-1.3 and temperature range of 350-600 K with various dilution rates. In addition, computational predictions for burning velocities and their comparison with experimental results and detailed flame structures have been presented. Sensitivity analysis was carried out to identify important reactions and their contribution to the laminar burning velocity. The computational predictions are in reasonably good agreement with the present experimental data (especially for N2 dilution case). The burning velocity maxima was observed for slightly rich mixtures and this maxima was found to shift to higher equivalence ratios (Ф) with a decrease in the dilution. The effect of CO2 dilution was more profound than N2 dilution in reducing the burning velocity of mixtures at higher temperatures.