Several fire tests were performed in a 1/7 model tunnel to explore the potentially reflash issue after blocking tunnel fire, and the temperature right above fire source, temperature distribution inside tunnel and radiant heat flux near tunnel portal were acquired. Results show that the occurrence conditions of tunnel fire reflash is mainly related to the amount of combustible vapor accumulated in the internal space and temperature level near fire source. Improper portal-opening moment will induce the reflash in such channel-like structure fire scenarios. In current experiment, when the both portals were suddenly opened, the ceiling temperature right above fire source of not less than 280 ^oC and liquid pool area of not less than 0.35 m² are one of the necessary conditions for the reflash occurrence. For the cases with large liquid fuel pool, the obvious thermal plume and flame will overflow out portals when reflash occurred. Within the scope of current test, maximum radiant heat flux near portals induced by reflash reaches 505.5 W/m². This work can provide some reference for the understanding of reflash feature of large-area fire and the corresponding emergency treatment of inside channel-like structure.

在1/7模型隧道中进行了多次火灾试验，探讨了隧道火灾阻塞后潜在的复燃问题，获取了火源正上方温度、隧道内温度分布和隧道口附近的辐射热通量。结果表明，隧道火灾复燃的发生条件主要与内部空间积聚的可燃蒸气量和火源附近的温度水平有关。在这种通道状结构火灾场景中，不适当的门户打开时刻会导致重新闪燃。在本次实验中，当两个入口突然打开时，火源正上方的天花板温度不低于280 ^o C，液池面积不低于0.35 m ²是复燃发生的必要条件之一。对于液体燃料池较大的情况，当发生再闪时，明显的热羽流和火焰会溢出入口。在目前的测试范围内，由复燃引起的入口附近的最大辐射热通量达到505.5 W/m ²。该工作可为了解大面积火灾的复燃特征及内部通道状结构的相应应急处理提供一定的参考。