Numerical Simulation Study of Methane–Air Explosion Suppression by Nonpremixed Nitrogen in a Closed Tube

ABSTRACT To study the explosion suppression mechanism of nonpremixed inert gas, this paper uses CFD software Simtec to simulate the suppression process of methane explosion by nonpremixed nitrogen in a square tube. The closed square tube includes three sections: ignition section, suppression section, and combustible gas mixture section. The results show that the critical explosion suppression length increases first and then decreases with the increase of methane concentration. When the methane concentration is 11%, the critical explosion suppression length is the biggest, which is 1.6 m. With the increase of the length of the suppression section, the overpressure curve first changes from a high‐pressure single peak to a double peak and finally to a low‐pressure single peak. After ignition, the nitrogen in the suppression section moves to the right with the flame under the driving effect of thermal expansion of combustion products. When the flame propagates near the suppression section, the nitrogen section stops moving right. Then, under the disturbance of the explosion wave, the suppression section is stretched. When the length of the suppression section is less than the critical explosion suppression length, the flame passes through the suppression section to ignite the combustible mixture, causing a secondary explosion. If the suppression length is greater than the critical explosion suppression length, the flame will gradually extinguish in the suppression section. The feasibility of suppression explosion by nonpremixed inert gas was verified, and the suppression mechanism of nonpremixed inert gas is inertial isolation rather than dilution.