Effect of roadway turnings on gas explosion propagation characteristics in coal mines

In order to reveal the effect of turnings on explosion propagation,experiments were performed in three different pipes (single bend,U-shaped pipe and Z-shaped pipe).Flame and pressure transducers were used to track the velocity at the explosion front.When the pipes were filled with methane,the explosion strength was significantly enhanced due to the turbulence induced by increasing the number of turnings,while the flame speed (Sf) and peak overpressure (△Pmax) increased dramatically.In addition,the strength of the explosion increased in violence as a function of the number of turnings.However,when the bend was without methane,the turnings weakened the strength of the explosion compared with the ordinary pipe,shown by the decrease in the values of △Pmax and Sf.In addition,the propagation characteristics in a U-shaped pipe were similar to those in a Z-shaped pipe and the values of △Pmax and Sf were also close.The results show that the explosion propagation characteristics largely depend on gas distribution in the pipes and the number of turnings.The different directions of the turnings had no effect.