| With the development of economic,China’s tunnel engineering construction projects are increasing year by year,constantly expanding the urban network radiation area,accelerating the advancement of the national modernization project,followed by the tunnel traffic fire accidents are also increasing year by year.In case of tunnel fire,there are two key issues.One is how to make up the air effectively to prevent the fire smoke from spreading to the evacuation passageway.The other is eliminating the smoke as soon as possible.Therefore,this paper studies the flow characteristics of fire smoke and the control method of supplementary air smoke in highway tunnel through the fire simulation software FDS.Firstly,the author investigates some large tunnel fire accidents at home and abroad,analyzes the characteristics,causes and harmfulness of the accidents.The paper introduces the basic theory of tunnel fire development,and determines the safety standard of personnel escape.Secondly,in order to ensure the safety of evacuation in case of fire,this paper puts forward the use of breathing area air supplement,and makes a comparative analysis with the current commonly used tunnel air supplement mode.It is found that the combined air supplement mode of breathing area air supplement+ upward air supplement can create a safer escape passage with zero smoke than the current air supplement mode,when the air supplement is the same,and can control the smoke discharge well.Compared with natural ventilation system,the concentration of CO in the safe smoke free escape passage is only 0.5% of he natural ventilation system.Finally,according to the air supplement mode of the combination of the air supplement in the breathing area air supplement + upward air supplement,the layout of the smoke exhaust outlet is determined to effectively control the smoke spread.The results show that,under the condition of a certain amount of smoke exhaust,with the increase of the area of the exhaust outlet,the exhaust efficiency of each exhaust outlet is increasing,and the total efficiency is also increasing.The smoke vent above the fire source plays a major role in the smoke exhaust system,which greatly improves the smoke exhaust efficiency of the system.The width of the exhaust outlet has a significant effect on the exhaust efficiency,while the length of the exhaust outlet has little effect on the exhaust efficiency.When the air supply in the breathing area is turned on,it is better that the exhaust outlet is set at 2m×1.5m and arranged every ten meters,which can effectively gather smoke and prevent the spread of smoke,and the total smoke exhaust efficiency can reach 75.77%.The air supply and smoke exhaust method proposed in this paper is expected to provide a theoretical basis for the design of tunnel smoke control system.The air supply and smoke exhaust method proposed in this paper is expected to provide a theoretical basis for the design of tunnel smoke control system. |
