Influence of obstacle blockage on methane/air explosion characteristics affected by side venting in a duct

To study the influence of obstacle blockage on explosion venting, a small sized experimental duct containing an obstacle with different blockages in different positions was built, and the methane/air explosion characteristics affected by side venting in the duct were studied. The explosion characteristics, including flame propagation, propagation velocity and overpressure profile, were analysed. The experimental results indicated that as the flame propagates upstream of an obstacle, flame propagation is little affected by the obstacle; when the flame passes the obstacle, flame propagation velocity and overpressure will always increase due to the incentive effect of the obstacle. Enlarging the blockage ratio increases the promoting effect of the obstacle. The relative position of a side vent and an obstacle affects side venting effect and the incentive effect of the obstacle. For a side vent in front of an obstacle, the explosion can be effectively discharged through the side vent before the flame reaches the obstacle, thus greatly weakening explosion intensity and decreasing the sensitivity of the explosion to the obstacle blockage. Whereas a side vent behind an obstacle is a disadvantage for the side vent to discharge the explosion, and the explosion intensity is very sensitive to the obstacle blockage.