Research On Smoke Prevention And Control Of Tunnel Fire Under The Cooperation Of Water Curtain And Smoke Exhaust System

With the continuous development of social economy and the continuous improvement of people's living standards,China's highway transportation network has developed rapidly,and the number and length of highway tunnels are constantly increasing.The development of traffic tunnels has effectively alleviated traffic pressure and gives people travel.It brings great convenience,but at the same time the frequency and scale of tunnel fires are also expanding.Due to the special narrow structure of highway tunnels,tunnel fire safety has always been a concern of people in the event of fire and ineffective control resulting in casualties,direct and indirect economic losses and adverse social impacts.According to statistics,more than 85%of the deceased in the fire are killed by the inhalation of smoke and toxic gases.Therefore,it is of great significance to carry out economic and effective flue gas prevention and control measures in the tunnel.In order to explore the influence of fire source power and water curtain linear spray intensity on flue gas characteristic parameters and water curtain smoke insulation ability,the full-size tunnel is taken as the research object,and the FDS numerical simulation method is used to restore and verify the small size used by the predecessors and to study the change regulations of smoke characteristic parameters under 20 sets of conditions.The results show that:(1)The simulation results of the large-scale model restored under the similarity principle under the same conditions are basically the same as the small-scale ones;(2)The effect of water curtain system on reducing the smoke shading rate and the total heat of tunnel section increases with the increase of linear water jet intensity,when the linear water spray intensity increases to a certain extent,there is no obvious change in the shading rate and heat insulation efficiency,and for medium and large scales fire,the effective time of the water curtain decreases;(3)For the small,medium and large-scale fire sources with the power of 5?20and30MW,considering the economic and water curtain effects,it is recommended that the linear water spray intensity of the water curtain be chosen to be 8?14 and 16 L/(s?m);For the same water spray intensity,the change trend of the shading rate of the smoke is different for different scale tunnel fires,and the failure process of the water curtain is different.Flue gas prevention and control is an important aspect of tunnel fire safety.In order to select the best smoke control method under the action of water curtain and mechanical smoke exhaust system and to explore the effect of fire source position on the two,the FDS numerical simulation method is used to explore the effect of smoke exhaust rate,water curtain exhaust port spacing and fire source position on the distribution of smoke flow.Through the study of the change regulation of smoke exhaust efficiency and smoke characteristic parameters under18 sets of simulated working conditions,the results show that:(1)When the fire source power is 20MW,the smoke extraction rate is 60m~3/s and the water curtain exhaust port spacing is12.5m,the exhaust efficiency is higher and the flue gas characteristic parameters meet the safety requirements,considering the effectiveness and economy of smoke control,the working condition is selected as the optimal combination of smoke prevention and exhaust method.(2)When the side wall acts alone,the lateral change of the fire source position has less influence on the CO concentration and temperature of the outer wall of the water curtain than that of the longitudinal change of the water curtain acts alone,and has a greater influence on the exhaust efficiency;The influence of the longitudinal position of the fire source under the joint action of the side wall and the water curtain on the CO concentration is smaller than that of the separate action of the water curtain,and the influence on the temperature is greater.(3)When the side wall and the water curtain work together,the influence of the change of the lateral position of the fire source on the temperature is greater than that of the side wall acts alone,and the effect on the exhaust efficiency is smaller.(4)The influence of the longitudinal change of the fire source position on the radiant heat flux outside the water curtain is greater than that of the lateral change;When the fire source changes laterally near the water curtain,the radiant heat flux near side wall of the water curtain is significantly higher than that at the far side wall,and gradually increases as the distance between the fire source and the near side wall decreases.