Numerical Simulation Of Water Mist Restraining Fire Spread In Highway Tunnel

Since the beginning of the 21st century,China’s comprehensive strength has been continuously improved,at the same time,the development and use of underground space have got the unprecedented rapid development and has shifted from a large nation of tunnels to power tunnels.The rapid development of highway tunnel brings convenience to people’s travel and social economy,but the burning place has movability,The fire spread quickly,fire Smoke Flow and security assistance is tough,thus,the occurrence of tunnel fire is often acco MPanied by serious casualties,high economic losses and bad social influence.Nowadays,the tunnel fire safety technology has put forward more severe and demanding requirements.As a new water-based fire extinguishing technology,water mist fire extinguishing system has the advantages of saving water consumption,small water loss,strong cooling and cooling ability,thermal radiation barrier ability,electrical insulation ability,smoke harmful components cleaning ability,so it is widely used in various fire fields.Therefore,this paper uses the water mist fire extinguishing system as the fire extinguishing equipment of tunnel fire,and numerical simulation was used to explore its effect on suppressing fire spread in highway tunnel.This paper uses FDS fire simulation software to establish a 1:1 interval tunnel model,three kinds of highway tunnels with different sections are taken as the research objects,the water mist fire extinguishing system is used as the tunnel fire extinguishing method.By setting up three factors affecting the water mist fire suppression efficiency of different longitudinal wind speed,the spacing of spray nozzle,and spray cone angle,the changes of temperature,heat radiation and carbon monoxide concentration in the tunnel after fire were simulated.Analyze and select the best water mist arrangement scheme.In this paper,the best layout scheme of the fine water mist system is simulated in detail when a30MW fire occurs in the tunnel:For a tunnel with a cross-sectional area of 79m~2,the nozzle arrangement form of the single-row top spray,the spray cone angle of 90°and nozzle spacing of 2m are most suitable;For a tunnel with a cross-sectional area of 154m~2,the double row side spray nozzle layout,the spray cone angle of 90°and nozzle spacing of 2m should be adopted;For a tunnel with a cross-sectional area of 191m~2,the single-row top spray and double row side spray nozzle layout,the spray cone angle of 90°and nozzle spacing of 2m should be adopted.At this time,those can not only effectively reduce the tunnel ceiling smoke layer temperature to the concrete fire resistance limit below,protect the tunnel structure is not damaged,but also can effectively reduce the fire heat radiation value.To the maximum extent to protect other vehicles around the fire source is not ignited,avoid the spread of flame.According to the optimal arrangement scheme of the fine water mist system,the influence of the longitudinal wind speed on the fire spread of the highway tunnel is simulated and analyzed.The most suitable longitudinal wind speed of 79m~2 of two-lane highway tunnel with large section and 154m~2of three-lane highway tunnel with large section is 3m/s.The critical wind speed of 191m~2 of four-lane highway tunnel with very large section is 2m/s.At this time,the coupling effect between the water mist extinguishing system and the longitudinal wind is the best in the reduction of the temperature of the flue gas layer,radiant heat flux and carbon monoxide concentration.Figure 57 Table 19 Reference 67...