Study on the smoke layer height in subway platform fire under natural ventilation

The smoke layer height under fire scenario is a vital parameter for emergency evacuation. Aiming at the effects of fire locations and heat release rate in a subway platform, series of numerical simulations were conducted under natural ventilation, and the temperature and visibility in the platform were measured. Results showed that the distinguishing characteristics of smoke layer height were presented in different regions (named Region Ⅰ ∼ Ⅳ) of the platform space, and the decreasing process could be divided into two stages: the first stage (0.6＜ Z1*≤1) and the second stage (Z2*≤0.6). For the first stage, the prediction model of smoke layer height in the four regions was uniformly proposed. Smoke layer height changed exponentially with time, and the attenuation factor at every position was basically the same but increased linearly with dimensionless heat release rate. For the second stage, the smoke layer height in the Region Ⅰ, Ⅱ, Ⅳ and Region Ⅲ decreased with time exponentially and linearly respectively, and the prediction models in different regions were developed separately. This work may provide guidance for personnel evacuation under fire emergency, and also provide reference for ventilation design in such a metro building engineering.