Effect of inert gas injection parameters on explosion suppression of H₂-CH₄ mixtures

To investigate the effect of inert gas injection parameters on the explosion characteristics of H₂-CH₄ mixtures, experiments were carried out in a horizontal pipeline to study the suppression of H₂-CH₄ mixture explosions by N₂ and CO₂. The effects of N₂ and CO₂ injection positions and injection angles on explosion pressure, flame propagation speed, and flame front temperature of H₂-CH₄ mixtures were examined. The results showed that N₂ and CO₂ significantly reduced explosion pressure, flame propagation speed, and flame front temperature, and that the suppression effect of CO₂ on H₂-CH₄ mixture explosions was stronger than that of N₂. The suppression ability of inert gas was better when injected at the near-flame end than at the far-flame end. As the injection angle of inert gas increased, the maximum explosion pressure, flame propagation speed, and flame front temperature gradually decreased, and the suppression effect on H₂-CH₄ mixtures gradually increased. Chemkin-Pro simulations indicated that, with the addition of CO₂, the peak molar fractions of H radicals and OH radicals decreased by 14.2% and 9.9%, respectively, compared with the condition without suppression; whereas with the addition of N₂, the molar fractions of H radicals and OH radicals were almost unchanged compared with the condition without suppression. The combined injection mode of "near-flame end + large angle" could maximize the synergistic suppression effect of CO₂ in terms of radical consumption, physical heat absorption, and combustible gas dilution, while the combined injection mode of "far-flame end + small angle" weakened the suppression efficiency of inert gas due to the dual limitations of diffusion delay and gas mixing non-uniformity.