隧道列车火灾的顶棚射流平均温度分布

Average Temperature Distribution of the Ceiling Jet in Train Fires in Tunnels

列车着火并停留在隧道内时,容易产生夹带火焰的顶棚射流。通过建立列车中部着火时火焰顶棚射流的一维单元控制体模型,考虑火焰烟气与隧道壁面和列车壁面之间的换热,导出列车火灾火焰顶棚射流平均温度的迭代计算公式。并通过隧道列车火灾的1∶8缩尺模型实验和数值模拟计算,确定了迭代公式中的待定系数。由该公式经过迭代运算后得到的平均温度值与实测值吻合较好,最大误差不超过7%,验证了公式的可靠性。结果表明:列车上方和离开列车进入隧道的火焰顶棚射流的平均温度均沿隧道纵向呈指数形式变化,但变化的程度不同。通过分段拟合的方法,分别给出了两段顶棚射流的平均温度沿隧道纵向变化的预测公式。对隧道列车火灾的报警参数选择及装置设置、乘客安全疏散,以及分析火灾对隧道衬砌结构的破坏作用等均具有一定的参考价值。

The flame ceiling jet is easily formed while the on-fire train stops in the tunnel.The iterative formula is derived to calculate the average temperature of the flame ceiling jet when the fire source is set on the center of the train by establishing a one-dimensional model of the unit control volume,and the heat exchange is considered among the flame smoke and the wall of the tunnel and the train.Undetermined coefficients in the iterative formula are determined by small-scale model experiments with the scale factor of 1：8 and numerical simulation.The calculated values of temperature by the iterative formula are consistent well with the measured values,and the maximum error of calculation is no more than 7%,which indicates that the iterative formula is reliable.The results show that the distributions of the average temperature of flame ceiling jet are in the exponential form,but there are some differences between that above the train and that in the tunnel.Two prediction formulas for the flame ceiling jet average temperature changing along the longitudinal tunnel are obtained by the sub-fitting method.The results can provide reference for the alarm parameter selection,device settings in tunnel,safety evacuation of the passenger,as well as the analysis of the destructive effects on the tunnel lining structure caused by tunnel fire.