Effects of mesh obstacles on flame propagation and explosion overpressure characteristics of methane/hydrogen mixtures in a semi-confined space

In industrial environments, ventilation grilles, protective railings, and mesh floor slabs are widely present, and such mesh obstacles can significantly influence flame development and overpressure evolution during gas explosions. This study employed numerical simulations to investigate flame propagation characteristics and explosion overpressure responses under varying axial locations (D = 0.025–0.50 m) and blockage ratios (BR = 0–0.70) of mesh obstacles. As the obstacle (BR = 0.36) was shifted downstream from the ignition end toward the outlet, both the flame propagation velocity and the peak overpressure first increased and then decreased, reaching their maximum values at an intermediate disturbance location (D = 0.2 m). The influence of the blockage ratio on flame propagation dynamics is strongly modulated by the axial position of the obstacle. During the intermediate disturbance stage, an optimal blockage ratio (BR = 0.36) was identified, at which turbulent disturbances in the vicinity of the flame front were maximally enhanced without completely suppressing the main flow passage. During the early disturbance stage (D = 0.05 m), the disturbance intensity introduced by the obstacle was relatively limited, and the effects of flame front segmentation and flame surface area enlargement were not pronounced. Under this condition, the highest blockage ratio (BR = 0.70) resulted in the maximum flame propagation velocity and peak overpressure, which increased by 18.65% and 48.19%, respectively, compared with the unobstructed case. These findings provide a theoretical basis for explosion risk assessment and the optimization of protective structures in semi-confined spaces.