Research on Smoke Diffusion Law of Tunnel Fire under the Influence of Blockage Effect
Long-distance highway tunnels are characterized by their length and high traffic volume,and fire hazards within the tunnels can lead to significant safety accidents and economic losses.In this paper,the smoke and temperature distribution under fire conditions in a long-distance highway tunnel are studied through FDS numerical simulation,and the influence of traffic jam on smoke and temperature distribution is explored.The results show that,when there is traffic jam,the blocked vehicles occupy the space in the tunnel,causing the smoke to sink more quickly.Due to the consistent power of the fire source,traffic jam has almost no effect on the temperature distribution in the early stages of the fire.When the initial fire source ignites the surrounding vehicles,the temperature in the tunnel increases significantly,and the high-temperature zone expands.Under the critical wind speed condition of 3 m/s,the smoke spreads downstream of the fire without any backflow.The CO concentration distribution in the plane at a height of z=1.7 m shows a wave-shaped low-concentration area in the middle of the plane and a high-concentration area on the tunnel side wall.Visibility is a factor that affects personnel evacuation earlier than temperature.Under traffic congestion,the time required for smoke to sink to the 1.7 m plane is about 8.4％less than that without congestion.
tunnel firelongitudinal ventilationsmoke diffusiontemperature distribution
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