Effect of side vent size on a methane/air explosion in an end-vented duct containing an obstacle

To reduce loss and damage caused by gas explosions in ducts, the effect of side vent size on explosion characteristics was studied in a 1000 x 100 x 100 mm end-vented duct containing an obstacle. Explosion characteristics including the flame propagation process, propagation velocity and overpressure were analyzed. The experimental results showed that when a side vent with length of 60 mm is located in front of an obstacle, the existence of the obstacle promotes the flame to be released through the side vent, thus causing a better deceleration effect on flame propagation than that of the configuration without an obstacle. Whereas for a side vent with length of 100 mm, the influence of the obstacle on flame propagation is relatively small. Furthermore, the discharge effects of side vents with different vent sizes are obviously affected by the relative positions of the obstacle and the side vent. For a side vent in front of an obstacle, the side vent has a perfect effect on flame propagation deceleration and overpressure discharging, and the discharging effect is less sensitive to vent size. However, for a side vent behind an obstacle, only a side vent with length of 100 mm has a considerable discharging effect, and the discharging effect is very sensitive to vent size. The experimental results strongly suggest that in practical applications, the side vent should be placed near the flammable point and set up in front of potential obstacles to play an ideal role of safety relief.