Three-Dimensional Numerical Simulation Study On Fire Ventilation In Long Highway Tunnel

To meet the urgent need of fire safety system research for the long highway tunnels, this thesis presents numerical simulation of the longitudinal ventilation control on fire smoke flow in Qingling Zhongnanshan King-size Highway Tunnel.Based on the conservation laws and chemical reaction laws a three-dimensional mathematical model of the smoke movement in tunnel fires was established. The model consisted of continuity equations, momentum equations, energy equations and species equations. A k-ε model with buoyancy modification was employed to model turbulent flow.Finite volume method was used to discretize the governing equations and the SIMPLE algorithm was employed to solve the discretized equations.Numerical results coincided well with those of scale model fire experiments of Qingling Zhongnanshan King-size Highway Tunnel, which indicated the proposed fire model was reasonable and valid.The model was then applied to predict fire cases in Qingling Zhongnanshan King-size Highway Tunnel. The steady and unsteady conditions of the fire in this tunnel were simulated. The affects of ventilation velocities, ventilation directions and tunnel slopes on fire smoke flows were investigated.The thesis presented a thorough analysis on fire smoke flows in tunnels and summarized their characters, which included velocity, temperature and concentration distributions, the affects of ventilation conditions on them and the heat transfer process in tunnels during fires. The thesis also discussed the influence of the tunnel slopes on smoke flows.The thesis investigated influence of the tunnel cross section's geometry on the temperature distributions during fires and put forward proposals on fire experiment research and the tunnel cross section's construction design.Aiming at this tunnel's fire safety design, the thesis provided following suggestions: the construction design should enhance the fire-resistant grade of the building material for the upper part of tunnel and provide fire-proof and heat-proof protection for the ventilation equipments at the top; the corner of the ground is suitable for the installation of the relevant equipments.The fire smoke flow model of this thesis can offer comprehensive information hence it can be served as a reference for the further research on the tunnel fire and ventilation in China.The research findings in this thesis provide not only direct guidance for the formulation of the scheme concerning the Qingling Highway Tunnel's disaster prevention and disaster relief, but also relevant reference for the other long tunnel fire safety projects.