Abstract: The cable fire risk of underground pipe gallery is extremely high. FDS software is used to simulate the flame spread of cable inside the underground pipe gallery under three conditions, namely, the combined action of liquid nitrogen and mechanical smoke exhaust, only mechanical smoke exhaust, and no liquid nitrogen or mechanical smoke exhaust. The smoke spread and temperature distribution in the underground pipe gallery after cable fire are analyzed. It is concluded that the combined action of liquid nitrogen and mechanical smoke exhaust can quickly extinguish the fire and reduce the risk of serious consequences caused by the cable fire. The effects of different nitrogen injection speeds and mechanical smoke exhaust speeds on extinguishing cable fires in the underground pipe gallery are analyzed, and it is concluded that an appropriate increase in nitrogen injection speed and smoke exhaust speed is beneficial to extinguishing cable fires.

Key words: cable fire;numerical simulation, liquid nitrogen fire extinguishing, mechanical smoke exhaust, smoke spread, temperature field