In order to study the suppression effect of CO2 and water mist on fire and explosion of transformer oil in underground substation and its chemical kinetic mechanism,the influence of water mist and CO2 with different volume fractions on the explosion of 20%H2-CH4-air mixture at stoichiometric ratio is studied by using experiments and Chemkin numerical simulations.Experimental and simulation results show that:the suppression effect on flame structure and expolosion pressure of H2-CH4-air mixture is more obvious with the increase of volume fraction of water mist.Water vapor molecules produced by evaporation of water mist and CO2 in the reaction system mainly play a stable role as a third body,thus slowing down the development of explosion chain reaction.In addition,since CO2 is the main product of methane oxidation reactions,the addition of CO2 will weaken the elementary reaction of methane oxidation.The addition of water mist to reaction system will inhibit the heating of reaction system through reducing the temperature sensitivity of elementary reaction,and the addition of CO2 will promote the generation of elementary reaction to consume·H radicals.This is the reason why the combined suppression effect of CO2 and water mist is better than that of water mist alone.The above results can provide a theoretical basis for the development of prevention technologies for fire and explosion of transformer oil in underground substations.
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