火源位置对井巷外因火灾参数影响的数值模拟研究

Numerical simulation study of the influence of fire source location on parameters of external fire in tunnel

为研究正常通风情况下巷道中不同火源位置对火烟蔓延及火灾参数的影响,研究了顶板单一火源、底板单一火源和同时位于顶底板的双火源3种工况下巷道内烟流、温度、CO体积分数的分布情况。结果表明:在烟流厚度上,底板火源和顶底板火源下游烟流沉降明显,而顶板火源无上升羽流现象,烟流更集中于顶部;在烟流逆退距离上,底板火源最短,顶板火源次之,顶板和底板火源最大,其主要影响因素为顶板最大烟流温差;在温度分布上,顶板烟流温度随与火源距离的增加而衰减,火源同时位于顶底板时衰减最快,对于上游顶板烟流温度,顶底板火灾最大,底板火灾最小,而下游则完全相反,此外三者工况下顶板火灾在2 m高处的烟流温度要低于其他2种工况;对于2 m高处CO体积分数,顶板火灾和底板火灾的浓度峰值出现在火烟前锋而底板火灾则出现在火源附近,且前两者工况下火源上游CO体积分数显著大于后者。

In order to study the influence of different fire source positions on fire smoke spread and fire parameters under normal ventilation,the distribution of smoke flow,temperature,and CO concentration in the tunnel under three conditions of single fire source at the roof,single fire source at the floor,and double fire sources at the roof and floor was simulated and analyzed.The results concluded that in terms of smoke thickness,the downstream settling of smoke was significant for fire at the floor and fire at both roof and floor,but no upward plume was observed for fire at the roof,and the smoke flow is more concentrated in the top.In terms of the backflow distance,the fire source in the floor is the shortest,followed by the fire source in the roof,and the fire source in the roof and the floor is the largest;the main influencing factor is the maximum smoke flow temperature difference in the roof.In terms of temperature distribution,the roof smoke flow temperature decreases with the increase of the distance from the fire source,and the fire source is located at the roof and floor at the same time.For the upper roof smoke flow temperature,the roof and floor fire is the largest and the floor fire is the smallest,while the downstream is completely opposite.In addition,the smoke flow temperature of the roof fire at 2 m height is lower than that of the other two conditions.For the CO volume fraction at the height of 2 m,the peak concentration of roof fire and floor fire appears at the front of the fire smoke,while the floor fire appears near the fire source,and the CO volume fraction upstream of the fire source is significantly higher than the latter under the former two working conditions.