Research on the explosion suppression effect of foam fire extinguishing agents on methane/air explosions under obstacle current limiting conditions

To investigate the suppression effects on gas explosion under the synergistic action of obstacles with varying blockage rates and foam extinguishing agents, a series of experimental studies were conducted. The comparison and analysis of blast mitigation performance were carried out by varying the spray positions of different foam extinguishing agents under blockage rates of 25 %, 50 %, and 75 %. The results indicate that due to the throttling compression effect of obstacles on explosion flames and their retention blockage effect on foam, better blast mitigation is achieved when foam extinguishing agents are sprayed downstream of the obstacles, with greater blockage rates and shorter distances between the spray nozzles and the obstacles. When foamed fire extinguishing agents are sprayed upstream of obstacles, a higher blockage rate of the obstacle and a greater distance from the nozzle to the obstacle result in a broader foam suppression zone, more effective interaction between the foam agents and the explosive flame, and better explosion suppression performance. Additionally, the foam agents can absorb the high temperatures generated by the explosion, effectively reducing overpressure and the peak rate of pressure rise. However, the position where the foam fire extinguishing agents are sprayed significantly influences the rate of flame propagation during the explosion; when sprayed upstream of the obstacle, the suspended foam causes earlier turbulence in the explosive flame, increasing the flame propagation rate. Conversely, spraying downstream of the obstacle can effectively lower the flame propagation rate.