Study On The Influence Of Lateral Smoke Exhaust Layout On Fire Smoke Movement Characteristics

With the development of cities and the improvement of transportation needs,the construction of highway tunnels has become more and more extensive.The construction of various long tunnels not only improves travel efficiency,but also brings challenges to the safe operation of tunnels.Once a tunnel fire occurs,it is easy to have catastrophic consequences.Therefore,tunnel fire is the focus of tunnel disaster prevention security research.In this paper,reduced scale model tunnel experiments are conducted.The smoke flow field,temperature distribution,air entrainment and heat exhaust efficiency are analyzed,and the influence of height position and opening Angle of lateral smoke exhaust on the effect of smoke extraction efficiency are obtained.The conclusions are as follows:(1)When the heat release rate and smoke exhaust rate are constant,the air entrainment coefficient increases with the increase of the distance between the exhaust vent and the tunnel roof.The air entrainment increases first and then decreases with the increase of Angle.(2)In the upstream of the smoke exhaust vent,the larger the distance between the exhaust vent and the tunnel roof,the smaller the roof temperature.In the downstream of the smoke exhaust vent,the smaller the distance between the exhaust vent and the tunnel roof,the smaller the roof temperature.When the distance between the exhaust vent and the tunnel roof is constant,the larger the smoke exhaust rate is,the lower the roof temperature is.When the distance between the exhaust vent and the tunnel roof is the minimum,the change of smoke exhaust rate has a significant impact on the temperature of the roof downstream of the smoke exhaust vent,but smoke exhaust vents at other heights are not.Changing the smoke exhaust Angle did not make the roof temperature decrease compared with the traditional smoke exhaust method(90°).When the smoke exhaust Angle is constant,the larger the smoke exhaust rate is,the lower the roof temperature is.(3)The greater the distance between the exhaust vent and the tunnel roof,the more the hot smoke in the upper layer will settle down.Therefore,within a certain height of the tunnel from the bottom,the greater the distance between the exhaust vent and the tunnel roof,the higher the vertical temperature.When the distance between the exhaust vent and the tunnel roof is constant,the temperature rise above the exhaust vent increases sharply with the rise of the height.When the opening Angle of the smoke vent is different,the vertical temperature rise rule is the same.(4)When the heat release rate and smoke exhaust rate are the same,the greater the distance between the exhaust vent and the tunnel roof,the lower the exhaust efficiency.And the exhaust efficiency decreases first and then increases with the increase of Angle.There is little difference between the exhaust efficiency when the exhaust Angle is 45° and 90°。A prediction model of heat exhaust efficiency under the influence of smoke vent height change is established and well verified.Conclusions of this thesis about smoke flow characteristics of the lateral smoke exhaust system can provide a reference for the design of the lateral smoke exhaust system in tunnel.