Experimental investigation on the effect of sealing speed on mine roadway fire behavior with longitudinal ventilation

Sealing both ends of the fire source is an effective method for controlling roadway fires. To better understand the impact of the sealing speed on the fire behavior of longitudinal ventilation roadway, a dynamic sealing method was proposed. A series of 1/10 scaled experiments were conducted at four different sealing speeds, and the variations in flame shape, mass loss rate (MLR), self-extinction time, smoke component concentrations near the fire source, and the ceiling temperature directly above the fire source (T_c) were investigated. The results indicate that in the early stage, the flame exhibits a significant downstream tilt, which gradually decreases as the sealing ratio increases. The time from ignition to self-extinction (t₁) shows a monotonically increasing linear relationship with sealing speed, and there is an overall decreasing trend between the time from complete sealing to self-extinction (t₂) and sealing speed. For oil pan sizes of 12.8 cm × 12.8 cm and 18.1 cm × 18.1 cm, the fuel MLR exhibits “single peak” and “double peaks” trends, and the concentrations of O₂ and CO almost reach the peak values at the same time. The limit oxygen concentrations corresponding to self-extinction are 15.2 %–15.5 % and 13.3 %–13.8 %, respectively, and the impact of sealing speed on the limit oxygen concentration, CO concentration and maximum T_c is not significant. Additionally, when the oil pan size is large, the slow sealing speeds may lead to fuel boiling overflow, which is detrimental to fire extinguishing. This study provides guidance for fire risk assessment during the mine roadway fire sealing process and contributes to the scientific development of sealing strategies.