不同断面形状隧道火灾下通风因子及中性层高度分析

Analysis of ventilation factor and neutral layer height for tunnel fire under different section shapes

考虑通风条件对火源热释放速率及烟气流动的影响,从隧道开口助燃空气的供应情况这一角度出发,分析隧道开口的空气流动状况。结合隧道断面的基本形状特征,利用伯努利流动方程和质量守恒方程等,对自然通风条件下圆弧形、矩形和拱形3种断面类型隧道的通风因子和空气流入速率进行了理论推导和计算。研究结果表明:不同截面形状隧道的通风因子和中性层高度变化规律并不相同,但其也有着内在的联系。通过对计算结果进行拟合分析,获取3种断面下通风因子的近似计算公式,并得到3种截面隧道的通风因子和中性层的变化规律曲线,为隧道火灾分析与工程应用提供参考。

In order to study the development of tunnel fire,considering the impact of ventilation on fire heat re-lease rate and flue gas flow,the air flow conditions of tunnel opening have been analyzed from the angle of the combustion air supply condition in this paper.Combining tunnel section shape features,the ventilation factor and air flow rate of tunnel in three kinds of cross-sections,arc,rectangle and arch,were derived and calculated in theory using the Bernoulli equation and mass conservation equations.Results show that the variation of the venti-lation factor and neutral layer height of different cross-sectional tunnel is not the same,but it is also intrinsical-ly linked.Based on the fitting and analysis of calculation results,the approximate ventilation factor formulas,the changing curves of ventilation factor and neutral layer of the three sections are obtained to provide some reference for fire analysis and engineering application of tunnels.