| Summary: | 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.
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