When a tunnel fire occurs, the response speed of the ceiling-mounted smoke or thermal detector is of great significance for controlling the fire. The information on the ceiling jet flow is important for detector installation and design. In this paper, a series of numerical simulations and experiments are conducted to investigate the jet flow velocity in tunnel fire during different stages. The ceiling jet flows velocities in the development stage and the stable stage are presented. When the growth rate of the fire source is very fast, the ceiling jet flow velocity in these two stages can be supposed as the same. A simple correlation of the velocity is developed and the predicted results are in good agreement with numerical values and experimental values. The gas flow driven by the thermal expansion at the beginning of the tunnel fire is also discussed. A prediction model of the gas expansion velocity is proposed.

当发生隧道火灾时，吊顶式烟雾探测器或热探测器的响应速度对于控制火灾具有重要意义。天花板射流的信息对于探测器的安装和设计很重要。本文进行了一系列数值模拟和实验，以研究不同阶段隧道火灾中的射流流速。介绍了在发展阶段和稳定阶段的顶棚射流速度。当火源的增长速度非常快时，这两个阶段的天花板射流流速可以假定为相同。建立了速度的简单相关性，预测结果与数值和实验值非常吻合。还讨论了隧道火灾开始时由热膨胀驱动的气流。提出了气体膨胀速度的预测模型。