Flame evolution and explosion characteristics of methane‐air premixed gas: Coupling of venting duct position and aspect ratio

Abstract This study examines the combined effects of venting duct position (S) and length‐to‐diameter ratio (L/D) on methane/air mixture explosion venting. A dedicated test system was constructed, and experiments were conducted with different S (0.25, 0.5, and 0.75 m) and L/D (6.25, 8.3, 12.5, 16.7, 25) values. The venting duct significantly influenced flame structure, categorized into four stages: venting, backflow, re‐venting, and strengthening. Smaller aspect ratios and closer proximity to the ignition end resulted in lower maximum explosion overpressure, rise rate, and dynamic pressure. Secondary explosions were more prevalent at larger S and smaller L/D ratios, with a peak pressure of 90.43 kPa. Conversely, secondary burstings in the main tube were more likely at larger S and L/D values, reaching 70.6 kPa. An empirical formula correlating P_max with S and L/D was derived to elucidate their coupled effect on methane/air mixture explosion behavior.