Experimental investigation of methane/coal dust explosion under influence of obstacles and ultrafine water mist

Experimental investigations were performed on mitigating methane/coal dust-mixture explosion in the presence of obstacles using ultra-fine water mists to reveal the effects of the obstacles and water mist. The explosion pressure and temperature history were obtained through PCB piezo-electronic pressure transducers and fast-response thermocouples, respectively. A Fastcam Ultima APX high-speed video camera was used to visualize both the explosion process and its mitigation. The LaVision laser diagnostic system was employed to measure the blast flow field considering the obstacles and ultrafine water mist, wherein the coal dust particles were considered the tracer particles. The results show that the explosion is primarily influenced by the number, shape, and installed locations of the obstacles; the reinforcement effect of the square ring is stronger than that of the column ring. The maximum explosion pressure, explosion temperature, and increase rate of pressure decrease by employing the ultrafine water mist, though the obstacles affect the suppression efficiency. In the explosion flow field, the dust particles distribute evenly in the explosion tube when the ultrafine water mist is not employed. The vortex of the flow field is unclear, whereas the vortex of the flow field becomes apparent in the presence of the ultrafine water mist. The results of this study can be helpful in guiding the design of water-mist systems for mitigating the risk of accidents in mines or other related areas and provide valuable data for model development.