无纵向通风曲线隧道和直线隧道火灾烟气特性数值模拟

Numerical simulation on fire smoke spread characteristics of curved tunnel and straight tunnel without longitudinal ventilation

基于数值模拟的方法,采用PyroSim软件搭建半径分别为250、300、400、500、600 m的曲线隧道模型及长度为130.8 m的直线模型,模拟隧道火灾发生后无纵向通风时的烟气运动,对比分析两种模型中心线上不同高度的烟气温度。模拟分析得到:火灾前期,直线模型中烟气蔓延时基本关于隧道中心线对称,而曲线模型中烟气运动时在上游偏向凹壁下游偏向凸壁;达到稳定状态时,直线模型中火源正上方温度高于曲线模型,无论近火源区还是远火源区,直线模型温度纵向分布关于火源位置均具有很好的对称性,而曲线模型中表现为近火源区波动较大,远火源区温度衰减梯度大于直线模型,1.6 m高度上游温度衰减梯度大于下游;提出曲线模型中顶棚温度纵向衰减指数模型。

Based on the numerical simulation method,PyroSim software was used to build a curved tunnel model with a radius of 250,300,400,500 m and 600 m and a straight tunnel model with a length of 130.8 m,respectively,to simulate the smoke spread in the condition of no longitudinal ventilation.Smoke temperatures at different heights of the center line of the two models were compared and analyzed.The simulation analysis shows that in the early stage after the fire,the smoke spread in the straight tunnel is basically symmetrical about the center line of the tunnel,while the smoke movement in the curved tunnel is inclined to the concave wall in the upstream and to the convex wall in the downstream.Under the stable state,the temperature above the fire in the straight tunnel is higher than the curved tunnel;no matter near-fire or away-fire zone,in the straight tunnel longitudinal temperature distribution has good symmetry with respect to the location of the fire source,and in the curved tunnelthe fluctuation of the near fire source is large,the temperature attenuation gradient of the far fire source is greater than that of the straight tunnel,and the temperature attenuation gradient of the upstream is greater than that of the downstream at 1.6 m height.The longitudinal attenuation index curve model of ceiling temperature in curved tunnel is put forward.