Study on the effects of hydrogen addition ratio and diluent gas concentration on the explosion characteristics of methane/hydrogen gas-mixtures

The widespread application of CH₄/H₂/air mixtures in the low-carbon energy transition has elevated their fire and explosion risks to a central safety challenge. A thorough examination of the explosion behaviors of these mixtures, coupled with the implementation of effective preventive measures, is crucial to proactively prevent and minimize catastrophic accidents that could result in severe casualties. This study delved into the CH₄/H₂/air explosion pressure, deflagration time and flame propagation behaviours in a N₂ and CO₂ atmosphere via experiment and simulation. The results demonstrated that CO₂ and N₂ reduced the maximum explosion pressure (P_max) by 34 % and 24 %, respectively; the deflagration time parameters were significantly prolonged with higher diluent gas concentrations. At 30 vol% concentration, CO₂ and N₂ decreased the flame propagation velocity by 46 % and 34 %, respectively. Additionally, CO₂ exhibited remarkable inhibitory effects on the molar fractions of H•, •O and •OH radicals at a 5 vol% concentration threshold, whereas N₂ required concentrations exceeding 15 vol% to achieve comparable suppression. Finally, this study concludes with a comprehensive analysis of the inerting and suppression mechanisms of N₂ and CO₂, examining both thermodynamic and kinetic perspectives. The research findings can provide guidelines for the safe utilization of CH₄/H₂ mixtures and facilitate the industrialization of hydrogen energy applications.