| With the rapid development of transportation industry,a large number of highway tunnels have been built at home and abroad.Although the emergence of tunnel is conducive to people’s travel,there are also many problems.Tunnel fire accident is one of them.Once tunnel fire accident occurs,it will cause great harm and economic losses to the country and society.In recent years,tunnel fire accidents at home and abroad have brought great disasters to people,which has also sounded the safety alarm of people all over the world.Therefore,the study of smoke diffusion law in highway tunnel fire is of great significance to fire prevention and control,and the study of smoke exhaust effect in tunnel fire can not be ignored.This paper takes the highway tunnel as the research object.Firstly,the theoretical knowledge is analyzed,and the tunnel experimental platform built in the laboratory is used for research.Finally,the tunnel fire is simulated by FDS numerical software,including flue gas temperature,flue gas countercurrent length,temperature at 2 m height and visibility at 2 m height.The main research work is as follows:The semi-transverse smoke exhaust experimental tunnel built in the laboratory is used for small-scale experimental research,and the fire smoke diffusion law of different power is studied with the help of FDS simulation software.The higher the power of the fire source,the higher the ceiling temperature in the tunnel,with the increase of the distance from the fire source,the temperature of the flue gas gradually decreases,and the temperature below the smoke exhaust outlet decreases sharply.After crossing the smoke exhaust outlet,the temperature first increases and then decreases.The temperature behind the smoke exhaust outlet is still less than the temperature in front of the smoke exhaust outlet,and the flue gas temperature shows a downward trend as a whole.The variation laws of temperature and flue gas temperature at each measuring point of numerical simulation are consistent with small-scale experiments,and the numerical model is reliable.The influencing factors of smoke countercurrent length in highway tunnel fire under semi-transverse smoke exhaust are studied.The flue gas countercurrent length increases with the increase of fire source power,decreases with the increase of smoke exhaust speed,decreases with the increase of smoke exhaust outlet area and decreases with the increase of smoke exhaust outlet spacing.The relationship between flue gas countercurrent length and four factors is obtained by curve fitting of numerical simulation results,and the dimensionless relationship of flue gas countercurrent length is obtained.The smoke exhaust effects of different smoke exhaust modes,different semi-transverse smoke exhaust volume and different layout forms of smoke exhaust outlets in the tunnel are studied,and compared and analyzed in combination with smoke spread distance,temperature at 2 m height and visibility index at 2 m height.Under the conditions of longitudinal smoke exhaust and semi-transverse smoke exhaust,longitudinal smoke exhaust is conducive to the escape of personnel in the upstream of the tunnel and causes great harm to the escape of personnel in the downstream.Semi-transverse smoke exhaust is conducive to the escape and rescue of personnel in the whole tunnel;Under different smoke exhaust volume,the greater the smoke-exhaust volume,the less the smoke exhaust volume in the tunnel.The smoke exhaust volume is 140 m3/s,which can meet personnel escape and fire rescue,under different layout forms of smoke exhaust openings,the smoke exhaust effect of smoke exhaust openings arranged on both sides of the tunnel is higher than that arranged on one side and in the middle,which is more conducive to fire rescue and personnel escape.Figure[42]table[8]reference[71]... |
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