Influence Analysis of Effects of Longitudinal Induced Velocity on the Smoke Control under Central Smoke Extraction System in Tunnel Fire

In order to analyze the influence of longitudinal induced velocity on the effects of smoke control under central smoke extraction system in tunnel and to further determine the reasonable longitudinal induced velocity, the Fire Dynamics Simulator (FDS) was utilized to build numerical analysis models and an array oflikely induced fire scenarios were designed, aiming at the engineering application of the central smoke extraction system in a highway tunnel. Visibility at a distance of 2 m above the ground along the tunnel, distance of smoke propagation and efficiency of smoke extraction in variation of induced velocities were respectively investigated for 50MW fire scenarios which different smoke extraction modes were taken into consideration, such as two-way balanced smoke exhaust or one-way smoke exhaust towards the upstream or the downstream. On this basis, the reasonable longitudinal induced velocity of different fire simulation conditions was identified. The results show that the influence of different longitudinal induced velocity on the effects of smoke control under central smoke extraction system is significant. For the specific size of fire, the reasonable longitudinal induced velocity may have little difference when different smoke extraction modes are respectively taken.