Numerical simulation on the characteristics of smoke exhaust effect with different sets of smoke vent in deep buried inclined channel fire

Abstract

Deep buried metro stations require longer and more inclined exit passages to connect with the outside. The fire characteristics of these inclined and narrow passages are significantly different from those of above-ground or shallow buried metro station exit passages, and at the same time fires in those inclined channels have a greater risk. This paper takes a channel of deep buried tunnel station in Chongqing as an example and simplifies the actual passage to establish a 3D model to study the smoke spread characteristics along the passage with different smoke vent characteristics including shape and location by FDS, as well as temperature distribution characteristic under different working conditions. The results show that: after a fire, smoke will spread upwards rapidly under the action of thermal buoyancy, and mechanical smoke exhaust plays a certain role in controlling smoke, which is more obvious at the beginning of the fire; there are differences in the smoke exhaust efficiency of different smoke extraction openings shape, but the differences are small, and square smoke vents have a slightly better effect on smoke control than other shapes of smoke vents; changing the location of smoke outlets has a greater impact on the environment in the tunnel. When the smoke vent is located directly above the fire source, the mechanical smoke control effect is significantly better than other positions, and as the distance between smoke vent and fire source increases, the average temperature along the passage increases. At the same time, because of the pressure difference after the fire, the emergency staircase and the upstream of the fire source are basically unaffected by smoke.