Effect Of Blockage Ratio On Subway Tunnel Fire Smoke Flow Characteristics

Study on subway tunnel fire smoke flow characteristics is great significance to ensure the safety of tunnel fire and evacuation. Currently many researches about subway tunnel fire smoke flow characteristics is conducted. In practical engineering, the blockage ratio of train is mostly discussed in road tunnel, but it is little analyzed in subway tunnel. When a fire occurs in the subway tunnel, the train needs to stop nearby, that is, the train does not move and blocking in the tunnel. The previous research also shows that the impact of the blockage of train on the fire smoke flow. So it is necessary to study the influence of the blockage ratio on the smoke flow characteristics in subway tunnel.Firstly, through summarizing and analyzing the domestic and foreign relevant research achievements of smoke flow characteristics of tunnel fire, this paper are targeted to make an investigation of No. 6 subway line in Chongqing about the form of tunnel section, the train models, formation and so on.Secondly, small-scale experiment and the numerical simulation FDS were carried out. The small-scale experiment verify the reliability of the numerical simulation, and a reliable FDS tunnel model was built by reasonable grid structures and boundary conditions.Thirdly, the effect of train blockage ratio on the maximum temperature, temperature distribution, backlayering length and critical velocity of subway tunnel fire under the condition of different section shape and the different longitudinal ventilation velocity is studied by FDS.The main research work and results of this paper are as follows:1)Blockage ratio coefficient is introduced to modify the prediction model of the maximum temperature beneath the tunnel celling that proposed by Kurioka et al.2) The modified prediction model of the temperature distribution along the longitudinal distance beneath the celling is introduced with blockage ratio coefficient.3) Blockage ratio coefficient is introduced to modify the prediction model of the non-dimensional smoke backlayering length and critical velocity based on the study of Weng MC et al.