Quantitative study on the inhibitory effect of carbon dioxide on hydrogen explosion and the production of carbon monoxide

This study experimentally and numerically determined the effect of CO2 on H-2/air explosion. The results indicated that CO2 can effectively reduce the maximum explosion pressure, the maximum explosion pressure rise rate and flame propagation speed of hydrogen explosion. Numerical simulations have confirmed that adiabatic flame temperature, laminar burning velocity, free radical concentration and the rate of product gradually decrease of hydrogen explosion with the increase of CO2 concentration. Among them, the changing trend of H radicals and laminar burning velocity is most closely related. Further analysis of the formation of H radicals found that as the CO2 concentration increases, reaction R31:CO + OH=CO2+H(Delta H = -203.5 kJ/mol) gradually proceeds in the reverse direction. While removing H radicals, the system temperature is absorbed, but a certain amount of CO is produced. In addition, analysis found that the physical inhibition effect of CO2 is significantly greater than the chemical inhibition effect. When phi = 0.6, physical inhibition effect accounts for 77 % of the total inhibition effect, and chemical inhibition effect accounts for 23 % of the total inhibition effect. When phi > 0.8, as the equivalence ratio and CO2 concentration increase, the proportion of physical inhibition effects gradually increases, and the proportion of chemical inhibition effects gradually decreases. The reason for the increase in the proportion of physical inhibition is that the dilution effect gradually shifts from promotion to inhibition.