Influence of Gradually Inflated Obstructions on Flame Propagation in a Tube Closed at One End

Abstract

Rapid suppression is a must in the mitigation of ventilation air methane (VAM) explosions. Flame suppression proves to be much more challenging than prevention of flame initiation due to the small physics timescale (~1 s). This study numerically investigates the effect of spherical obstructions on flame propagation dynamics in a tube closed at one end. Obstructions with an inflating geometry, installed at different locations, were examined. Noticeably, in the presence of a single or multiple obstructions that partially block the tube, flame and pressure waves propagate faster upstream than in an empty tube; this phenomenon is more pronounced when the obstruction is located further away from the ignition point. In scenarios of a full blockage of the tube, the high pressure builds up inside the blocked region, e.g., surging up to 7.5 bar in less than 0.1 s at a location 10 m away from the ignition point (tube diameter: 0.456 m). Obstructions located closer to the ignition point experience more tearing in terms of duration and strength.