Opposing Propagation Characteristics of Methane-Air Deflagrations in an End-to-End Pipe

Propagation characteristics of methane-air deflagrations through an end-to-end pipe were investigated using the AutoReaGas software. The results indicate that the maximum overpressure first decreases and then increases with increasing distance from ignition source, and the overpressure minimum occurs at approximately 3.4 m. When shockwaves from the intake and return airways meet, a positive superposition effect forms, generating maximum overpressure, density, and combustion rate values that are larger than the same values at adjacent points. The explosion parameters along the intake airway are similar to the parameters along the return airway. A 50% filling ratio causes nearly the same level of explosion violence as a 100% filling ratio. The characteristics of explosion propagation are similar whether the ignition source is located at the upper corner of the coal face or at the centre of the coal face. Some preventive measures may be taken to reduce the losses caused by gas explosions near superposition areas in underground coal mines