双火源隧道火灾数值模拟

Numerical simulation on double fire source tunnel

为了给隧道内双火源事故风险评估和人员疏散提供参考,构建了隧道双火源火灾FDS数值模型,开展不同火源宽度和间距下的双火源隧道火灾模拟,研究了隧道内近顶板纵向温度、火源中心火场温度、隧道流场以及火场附近热辐射的分布规律。研究结果表明:隧道双火源火灾由于火源间相互影响,火场内会形成热量和烟气的积聚;随着火源宽度增加,火源的单位面积热释放速率减小,隧道内最高温度迅速减小,隧道开口处温度基本保持不变,因此,远端纵向温度衰减因子逐渐减小;双火源之间靠近地面的温度呈现“凹”形分布,且大部分区间温度基本保持稳定,稳定温度随火源宽度增加呈现上升趋势;隧道内烟气最大流速出现在火羽流内部,受火源间距影响小,而受宽度影响大;伴随宽度增加,隧道内最大流速减小,浮力效应减弱,烟气层厚度增加,烟气沉降效应明显;双火源间近地面位置处的辐射受火源间距影响大,而受宽度影响小;随着火源间距增加,辐射强度迅速下降,但仍会对救援人员造成较大伤害。

A tunnel double fire source FDS numerical model was built in order to provide reference for the risk assessment and evacuation.The double fire source simulation in tunnel at different fire widths and fire spacings was carried out.The distribution law of ceiling longitudinal temperature,temperature in the fire field at the center of the fire source,flow field and heat radiation intensity near the fire field were studied.The results show that in a double fire source tunnel,heat and smoke will accumulate in the fire site due to the mutual influence of the fire sources.As the width of the fire source increases,heat release rate per unit area of the fire source decreases,the maximum temperature in the tunnel decreases rapidly and the temperature at the opening of the tunnel remains basically unchanged,so the longitudinal temperature attenuation factor at the far end gradually decreases.The temperature between the double fire sources near the ground shows a"concave"distribution,the temperature in the most of the intervals remains basically stable and the stable temperature shows an upward trend with the increase of the fire source width.The maximum flow velocity of smoke in the tunnel appears inside the fire plume,which is less affected by the fire source spacing and greatly affected by the fire source width.With the increase of the fire source width,the maximum flow velocity in the tunnel decreases,the buoyancy effect weakens,the thickness of the smoke layer increases and the smoke deposition process becomes more obvious.The radiation intensity near the ground between double fire sources is greatly affected by the distance between the fire sources and it is less affected by the width.As the distance between fire sources increases,the radiation intensity drops rapidly,but it still causes great harm to rescuers.