Evaluation of Fire Suppression Performance for Multiple-Fire-Source Fire Using Water Mist-Type Fire-Suppression Equipment for Railway Passenger Cabin

The fire suppression performance of a mist fire-extinguishing system in railway passenger cabin was evaluated using a performance evaluation method based on multiple fire sources. Scenarios were analyzed for a simulated space in the railway vehicle cabin of the Daegu Urban Railway Line 3 using automatic fire-suppression system methods based on railway-vehicle technical standards. Three n-heptane fire pools were positioned inside the test space. When the spray fire-extinguishing equipment was operated at 10 and 20 bar after 30 s of ignition, the variations in the temperature of the test space and the fire-extinguishing characteristics, such as the time taken to stop the fire-extinguishing equipment, were analyzed. The experimental results showed that the internal temperature of the cabin initially increased after ignition. However, when the fire- extinguishing equipment was operated 30 s after ignition, the internal temperature of the cabin stopped increasing and started to decrease, satisfying the fire safety standard that the fire must be completely extinguished within 5 min. The temperature decreased more rapidly when the operating pressure was 20 bar than when it was 10 bar. In addition, the vertical temperature distribution analysis showed that the temperature of the upper part was higher than that of the lower part, owing to thermal buoyancy. However, the design of the nozzle location is critical because the temperature decreases more slowly far from the nozzle of the mist fire-extinguishing system, which can be dangerous.