Full-scale experimental study on fire suppression performance of a designed water mist system for rescue station of long railway tunnel

Rescue stations have been newly designed in some super-long mountain railway tunnels of China such as over 30 km long, as a new type of strategic counteract design for fire accident in tunnels. Water mist fire suppression systems are needed to be installed in such rescue stations to control the train fire. However, there is no design engineering experience for it. In this article, a full-scale experimental facility was built to study the fire suppression performance of water mist system in such railway tunnel rescue station. A series of full-scale tests was preliminarily conducted considering the fire position was on top of, inside, and under the train carriage with gasoline pool fire and wood crib fire used as fire sources. A design of water mist suppression system for such a fire scenario was presented, and its performance was tested. Experimental data on temperature, CO concentration, and radiation flux were collected and analyzed. The results showed that the water mist system could control fires, cool the air temperature in the rescue station, and strongly reduce the radiant heat flux in the vicinity of the fire source under various ventilation conditions. However, the visibility of the rescue station was much deteriorated after the injection of water mist, so that emergency lights and evacuation lights are necessary for personnel evacuation. The changes of fire extinguishing time with longitudinal ventilation velocities showed that longitudinal ventilation could provide both favorable and unfavorable conditions for water mist fire extinguishment. So, to achieve efficient fire suppression performance of water mist system, attention might be paid to the controls of tunnel ventilation system in the event of a fire in a railway tunnel rescue station. The design of the water mist system and the full-scale experimental data on the fire suppression performance presented in this article may serve as a reference for such engineering applications.