Full-scale experimental study on water mist fire suppression in a railway tunnel rescue station: Temperature distribution characteristics

Rescue stations are essential for emergency evacuation in super-long railway tunnels. However, the deficiency of related studies aiming at improving the fire suppression performance of water mist system in fire scenarios limits its application significantly. In this work, 20 sets of full-scale water mist fire suppression experiments were conducted to examine the impacts of water mist system on smoke temperature characteristics, including water mist activation time (denoted by t), working pressure (P), k-factor (K) and longitudinal wind speed. Results show that when t = 3 min, P = 12 MPa, and K = 0.5, the best performance of temperature control could be achieved. Although there are violent temperature fluctuations in the train side, the smoke temperature could be easily restrained. Moreover, it is found that longitudinal ventilation is helpful to improve the visibility at platform and reduce smoke temperature. When P = 12 MPa, the coupling effect of water mist and longitudinal ventilation on cooling smoke is better. In addition, the non-dimensional maximum temperature rise is found to show a great cubical dependency on vertical height, and decreases along with a larger longitudinal distance for all cases. Also, under longitudinal ventilation, the non-dimensional maximum temperature rises are lower than that without longitudinal ventilation in the coverage area of water mist. Results of this work can provide a significant reference for the design of water mist system in railway tunnel rescue stations. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.