터널火災에서 제트팬方式과 均一排氣方式의 制煙效率에 관한 數値硏究

Abstract

In order to investigate the efficiency of smoke control systems in tunnel fires, numerical simulations were carried out for 5MW, 20MW, 30MW kerosene fires in a tunnel of 1km long, using the Fire Dynamics Simulator(FDS). Firstly, FDS was applied to a pool fire in a room, of which dimensions were 1.8m × 1.8m × 1.38m with an opening of 0.45m×1.2m doorway, to evaluate the numerical method. Secondly, a underground room fire was simulated to investigate the smoke extraction. A room of 6m×6m×2.5m with a door of 0.9×2.0m and a 0.5MW polystyrene fire in the room were considered. Finally, numerical simulations of a tunnel fire were carried out for 15.81kW, 63.25kW and 94.87kW kerosene pool fires in a 1/10 scale down tunnel of 100m×1.0m×0.6m. The smoke control systems considered include two types: the vent type with 198 vents at the ceiling and the jet fan type with 12 jet fans. The exhaust velocity at the vent is 0.208m/sec and the exhaust velocity of each jet fan is 9.487m/sec. The following conclusions could be drawn from this study. (1) In a room fire, FDS predicted a very rapid fire growth compared with the experiment for all the three fire sizes. The temperature distributions, heights of hot gas layers, and the locations of neutral planes in quasi-steady state were in reasonable agreement with the measurements. It was confirmed that the fire growth rate was adjustable by using the ramp function. (2) In a underground room fire, it showed that increasing exhaust velocity decreased room temperature and volume fraction of CO and soot. From these results, it was found that the vent type ventilation system is useful for the underground room. (3) In the tunnel fires, the values of time-averaged temperature, visibility, and CO volume fraction at z=0.15m of the vent type were not affected by the fire, showing a good efficiency in smoke control. (4) Compared with the vent type, the jet fan type yielded higher temperature and shorter visibility. Therefore, it was confirmed that the jet fan type may cause problems in to evacuation and fire-fighting. (5) The efficiency of smoke exhaust of the vent type is better than the jet fan type. Accordingly, it was recommended that the jet fan type be used to maintain the critical velocity in the tunnel and the vent type be used to exhaust smoke.