Study On Three Dimensional Numerical Simulation Of Ventilation And Fire In Subway Station

Subway station is important construct which has large proportion in subway investment. Temperature and velocity of air has great effect on human comfort and energy cost of environment control. Considered the characteristics of low Reynolds flow in subway station, based on Navier-Stokes equation, Renormalization Group k-8 turbulence model is introduced. By Renormalization Group approach, kinematics equation and kinematics dissipate equation are developed and turbulence coefficients are acquired. Computational fluid dynamic model suitable for the turbulent flow field and temperature field in subway station are established. For the complex geometry of subway station, unstructured meshes are constructed by Delaunay triangulation method. By properly choosing temporal and spatial difference format, correctly dealing with source term and boundary conditions, control equations are discretized over unstructured meshes. To overcome the reduced convergence speed of iteration method, multigrid method is introduced and algebraic multigrid is adopted to solve discretized equations because of its higher effectiveness. Using above methods, three kinds of typical indoor flow field, natural convection, forced convection and hybrid convection are calculated by standard k-e turbulence model and RNG k-e turbulence model. The results are compared with experimental data in document and fine agreement is achieved, both of two model. For some special index, the results of RNG k-s turbulence model are better than standard k-ε turbulence model's, which proved that the method presented in this thesis is correct and practicable.Based on above study, a simplified model of a subway station which awaits build is established. Normal operations include idle state, train draw up at one side, train dwell at the station, are simulated as well as congestion mode of emergency state. Temperature field and velocity field are obtained and the variation of these two fields is analyzed. The comfort of passenger on platform is valued dynamicly by relative warm index. Four scheme of ventilation, platform center return sysytem, under platform exhaust system, over track exhaust system and UPE/OTE exhaust system, were simulated. In the temperature, velocity and air age of view, these schemes were compared and analyzed. As the temperature in the waiting hall when four ventilation scheme described above were adopted dissatisfied the standard,platform screen door scheme was simulated and analyzed.The case of fire in subway station is probably the worst situation. Simulation of fire on train which stops at platform is also performed. Three fire locations of the train were considered. Discrete transfer method is applied to count radiation caused by high temperature of the fire. Exhuast only and push-pull ventilation strategy were compared. Code for the design of metro and NFPA 130 standard were introduced to evaluate the circumstance on the platform. Visibility was achieved as well as temperature and velocity. The influence on velocity field and smoke concentration brought by the strategy of environment control and construct of platform is analyzed. The possibility of rescue and evacuation under all fire location of the train is assessed separately. Methods and results presented in this dissertation provide good reference to subway construction.