Metro trains running in tunnels cause piston wind, and when a metro train stops in a tunnel due to a fire, the effect of the piston wind on smoke propagation characteristics cannot be ignored. In this paper, a theoretical model based on the unsteady flow theory of the Bernoulli equation was established to describe the change in piston wind speed under fire conditions. The characteristics of the smoke propagation in tunnel fires under the effect of the piston wind were analysed by means of numerical simulation. The result indicates that the piston wind has a significant effect on the characteristics of smoke distribution. In a longitudinally ventilated tunnel, whether the direction of piston wind is the same as that of longitudinal ventilation could seriously affect the control of fire smoke. When the direction is the same, the piston wind could enhance the smoke control effect of the longitudinal ventilation. Otherwise, the smoke control effect could be significantly diminished, and the smoke control by the critical wind speed of longitudinal ventilation would fail. The findings could contribute to a better understanding of the characteristics of tunnel fire to control smoke spread under the influence of piston wind.

在隧道中行驶的地铁会产生活塞风，当地铁因火灾停在隧道中时，活塞风对烟气传播特性的影响不容忽视。本文基于伯努利方程的非定常流动理论建立了一个理论模型来描述着火条件下活塞风速的变化。通过数值模拟分析了在活塞风作用下隧道火灾中烟气的传播特征。结果表明，活塞风对烟气分布特征有显着影响。在纵向通风的隧道中，活塞风的方向是否与纵向通风的方向相同，会严重影响火烟的控制。当方向相同时 活塞风可以增强纵向通风的排烟效果。否则，烟雾控制效果可能会大大降低，并且纵向通风的临界风速无法控制烟雾。这些发现可能有助于更好地了解隧道火灾的特征，以控制在活塞风的影响下散发的烟雾。