Characteristics and mechanism of mine-associated oil-type gas explosion suppressed by CO₂ inerting

To reveal the explosion risk and inerting characteristics of mine-associated oil-type gas, this study systematically investigates the properties and mechanisms of carbon dioxide (CO₂) in suppressing the explosion of mine-associated oil-type gas by combining experimental tests, numerical calculations and theoretical analysis. A 20 L spherical explosion test system was adopted to determine the explosion limits and explosion pressure of oil-type gas, as well as the variation of explosion pressure and critical inerting volume fraction under CO₂ inerting. Based on the USC Mech 2.0 model, the distribution of adiabatic flame temperature and reaction kinetic mechanism of oil-type gas explosion under CO₂ inerting were analyzed. The results show that the lower explosion limit of the tested oil-type gas is only 4.55%. The Le Chatelier model can accurately predict the lower flammability limit, while the predicted upper flammability limit is 55.84% lower than the experimental value. Within the measured explosion limit range, the peak overpressure and maximum overpressure rise rate of oil-type gas reach 0.79 MPa and 25 MPa/s, respectively. The corresponding total combustion duration t_c and rapid explosion duration t_b are 127.6 ms and 93.2 ms. With the increase of the equivalence ratio of oil-type gas, the critical inerting volume fraction of CO₂ required for complete explosion suppression decreases. When the equivalence ratio is 1.4, the critical explosion-suppression volume fraction of CO₂ is 8%, which is 65.21% lower than the value（the critical explosion-suppression volume fraction of 23%） at an equivalence ratio of 1.0. The addition of CO₂ inhibits the laminar burning velocity and adiabatic flame temperature of oil-type gas, reduces the chemical reaction rate and macroscopic pressure parameters, and the explosion suppression effect is enhanced with the rise of equivalence ratio. Increasing CO₂ concentration lowers the adiabatic flame temperature and heat release rate of key elementary reactions of the mixture, and also leads to a decrease in concentration of critical free radicals such as H, O and OH during explosion, thereby achieving the inerting effect.