Study On Ventilation Network Simulation Of Urban Traffic Link Tunnel Under Fire

With the rapid development of urbanization in our country, the problem of traffic jams becomes increasingly serious. Transportation roads cannot satisfy the need of rapid growth of vehicles. On the basis of existing national resources our country considers environment and economic performance and cost of investment and develops transportation network systems in many cities such as subway, highway tunnel and fast track. A novel type of underground transportation network system is called urban traffic link tunnel.Urban traffic link tunnel consists of main loop tunnel and several access tunnels with large slope. Main loop of UTLT is mainly used to connect underground garages and access tunnels connect with high streets, which alleviates traffic congestion of traffic peak areas. Complex structure of urban traffic link tunnel makes it require a more complex ventilation system under fire.Urban traffic link tunnel ventilation system under fire has many problems to be solved. The problems include determination of the tunnel actual flow directions and calculation of air volume value, temperature and pressure and selection of fan equipment matching scheme. In order to solve the above problems, we need to transform urban traffic link tunnel ventilation system into network diagram on the basis of graph theory, and then build ventilation network mathematic models of urban traffic link tunnel under fire and write network ventilation programs, which is a new method of the quantitative description of ventilation network system of urban traffic link tunnel under fire.This paper studies the concrete contents include:(1) Establish urban traffic link tunnel ventilation network mathematic models under fire such as ventilation dynamics model, temperature model, heat source model and heat transfer model of envelope.(2) Adopt the combination of CFD and network simulation method to calculate local resistance coefficients of complicated local structures of urban traffic link tunnel. And make local resistance coefficients as the input parameters of the network simulation solver.(3) Transform ventilation network mathematical models of urban traffic link tunnel under fire into the calculating program by matlab. Calculate the tunnel parameters such as airflow, temperature and pressure and determine pressure and flow rate which ventilation equipments can provide in different ventilation schemes of urban traffic link tunnel under fire, such as jetting longitudinal ventilation system, shaft longitudinal ventilation system, half-transverse ventilation system and natural ventilation system. Then optimize ventilation schemes of urban traffic link tunnel under fire.By urban traffic link tunnel ventilation network simulation under fire, the accurate parameters of tunnel such as airflow, temperature and pressure are calculated, which helps to determine the tunnel concrete scheme of ventilation and smoke control. The research provides a calculation method to determine the tunnel concrete scheme of ventilation and smoke control of other similar urban traffic link tunnel under fire. And it offers help for safety and reliability analysis of urban traffic link tunnel ventilation schemes.