Abstract: In order to study the effectiveness of low-pressure water mist fire extinguishing in urban underground integrated pipe corridor cable fire and to identify the key factors influencing its efficiency, a scaled-down test platform for low-pressure water mist fire extinguishing in utility tunnels was constructed, and a serial of fire extinguishing tests were conducted. The test results demonstrate that low-pressure water mist can rapidly and effectively extinguish cable fires in utility tunnels, with the quickest fire extinguishing time of 7 s. Within 50 s of activating the system, the internal temperature of the tunnel can be reduced from 650 ℃ to 40 ℃. The changes in pressure and nozzle flow coefficient have a significant impact on the fire extinguishing efficiency of low-pressure fine water mist. The fire extinguishing time is shortened by up to 75% and 66.7% respectively, and the average cooling rate is highest at 8.2 ℃/s and 7.43 ℃/s; The change in nozzle spacing has a relatively small impact on fire extinguishing efficiency, with a maximum reduction of 47.3% in fire extinguishing time and an average cooling rate of 6.1 ℃/s.

Key words: low-pressure water mist, utility tunnel, cable fire, fire extinguishing efficiency