Effect of square-aperture and solid rectangular obstacles on pressure evolution and flame dynamics in methane-air continuous explosion
Chengcai Wei, Minggao Yu, Haitao Li, Jiachen Wang, Guang-yue Hu, Yihao Yao, Shoutong Diao
Abstract
In underground coal mines, obstacles with square apertures or solid rectangular geometries are commonly encountered, yet their influence on methane-air continuous explosions remains poorly understood. This study experimentally investigates how obstacle shape and blockage ratio affect explosion dynamics using a custom-designed pipeline platform. Results show that both perforated and solid obstacles intensify explosion severity by enhancing turbulence and flow disturbances. Increased blockage ratio correlates with faster flame propagation. Compared to solid obstacles, square-aperture structures promote high-speed axial jets that facilitate rapid flame acceleration. In contrast, solid obstacles force the flame to detour, generating large-scale vortices and unburned gas accumulation, which reduce combustion efficiency. Flame behavior is governed by coupled instability mechanisms. Density gradients between burned and unburned gases induce Darrieus–Landau instability, amplifying flame surface perturbations. Flow separation near obstacles leads to Kelvin-Helmholtz instability, forming vortical structures. Reflected shock waves interacting with flame fronts trigger Richtmyer–Meshkov instability, causing flame reversal, secondary deflagration, and oscillatory propagation. These findings clarify the role of obstacle-induced instabilities in continuous explosions and highlight the importance of obstacle geometry in shaping flame dynamics.