The weakening and suppression effects of cavities on the propagation of gas explosions in pipes

To reduce the hazard of gas explosions, the weakening and inhibiting effects of additional cavities and obstacle deflectors on the propagation of gas explosions in straight pipes were investigated by means of comparative experiments in a self-constructed experimental platform. The results show that an additional cavity in the straight pipe can reduce the intensity of the gas explosion. Moreover, the obstacle deflector in front of the cavity can further weaken the intensity of the gas explosion. When the obstacle was located 0 m and 0.1 m in front of the cavity, the explosion flame and shockwave were deflected to hit the inner wall of the cavity, then rebounded, and sufficiently diluted by the air in cavity, thus the subsequent development of the explosion was restricted. The second peak overpressure was reduced by 5.15% and 27.82%, respectively, compared to that of the pipe only with a cavity, and the explosion flame was diverted and quenched in the cavity. When the obstacle was located 0.2 m in front of the cavity, the intensity of the gas explosion increased, and the flame quickly crossed through the cavity and rushed out of the pipe end. An obstacle in the middle of the vertical direction is more effective at reducing the strength of the gas explosion than an obstacle located at the bottom. The minimum amount of ABC dry powder (containing 75% ammonium dihydrogen phosphate and 15% ammonium sulfate) needed to prevent gas explosions is reduced by the additional cavity in the straight pipe. When the obstacle is located in front of the cavity, the minimum amount of ABC dry powder available for explosion prevention is further reduced. The reduction in the amount of ABC dry powder required for explosion prevention also intuitively reflects the weakening effect of the cavity and obstacle deflector on the gas explosion.