Study On Variation Law Of The Critical Velocity In Two-lane Highway Tunnel Fire

In recent years, with continuous development of the highway tunnel construction, the probability of tunnel fire has also showed an increasing trend. Once a fire accident breaks out in a highway tunnel, evacuation, fire fighting and rescue will be faced with challenges, and these may result in serious casualties and property losses. Longitudinal ventilation is the most common form of ventilation in a highway tunnel, and carrying out research on impact factors of the critical velocity will have great significance. the main content of this thesis is the impact factors of the critical velocity for two-lane highway tunnel fire by theoretical analysis and numerical simulation method, the main findings and conclusions can be listed as follows:The CFD numerical simulation software FDS developed by NIST was used in this thesis to simulate the critical velocity of various tunnel fire scenarios, and then the simulated results were compared with previous small-scale and large-scale experiments to verify the reliability of applying FDS to study the critical velocity of tunnel fire.A two-lane highway tunnel models was built by FDS to analysis the effects of the characteristics of fire source (e.g. HRR, location, length and width), blockage ratio and slope on the critical velocity of the tunnel fire, which obtained the relationships between the critical velocity and varied factors.According to contrast with the amplitude of variation in critical velocity about impact factors, the order of importance on the influencing factors those impact on critical velocity was obtained in a highway tunnel fire.Statistical analysis showed in a specific fire scenario the critical velocity ratio has certain corresponding relationship with three-fifths power of the thermodynamic average temperature ratio, and the temperature was acquired at the downstream of the fire source on the vault.The research work on variation law of the critical velocity in two-lane highway tunnel fire, which has been done in the thesis can provide some beneficial reference for the tunnel ventilation exhaust design and enactment on emergency rescue plan of tunnel fire.