Thermal characteristics of ghosting flame in coal mine dead-end roadway pool fires affected by fire locations

As an important phenomenon in the evolution of fire, the ghosting flame exhibits dynamic and irregular behavior in environments with limited ventilation. By ghosting flame, we mean the phenomenon where the flame separates from the fuel surface under certain conditions. This study investigates the combustion characteristics of the ghosting flame in pool fires within a coal mine dead-end roadway by small-scale experiments. Results indicate that the ghosting flame appears more readily and earlier when the fire source is closer to the heading face or when the oil pan size is larger. Additionally, the fire source's location significantly influences the type of ghosting flame observed. When the fire source is near the heading face, the flame predominantly exhibits horizontal-type ghosting flame; however, when the fire source is at the entrance of the roadway, only the edge-type ghosting flame occurs. Furthermore, dead-end roadway fires easily transition to ventilation-controlled conditions, leading to a continuous increase in the mass loss rate. The occurrence of a ghosting flame does not result in a sudden change in the mass loss rate. Moreover, the transient oxygen volume fraction when the ghosting flame occurs is related to the ghosting flame type and is also affected by ventilation conditions, fuel types, roadway structure, and the location of measurement points. Importantly, the root cause for the occurrence of the ghosting flame lies in the pressure differential generated by the temperature disparity between the two sides of the fire source.