چكيده به لاتين
Tunnels are one of common instruments for Development of cities. One of the most important events in tunnels is fire. When a fire occurs in a tunnel, the environment of tunnel gets unsafe and injures the health of passengers. Simulation of fire in tunnel is a branch of science that many researchers are working in it. The goal of researchers is defining ways for protecting passengers from hazards and safe evacuating them from tunnel to environment. A usual way for safe evacuation is emergency ventilation in tunnel. Emergency ventilation divides tunnel to two regions, upstream and downstream, by creating critical ventilation velocity. The critical ventilation velocity is minimum velocity of ventilation in tunnel that prevents from smoke back layering and diffusion of toxic emissions of fire in upstream region. In this research emergency ventilation scenarios at fire mode have been designed for Tehran-Tabriz railway tunnel. The length of this tunnel is 8 km and it has 4 rail tracks. Different location of train and the optimized operation of fans at emergency ventilation mode are defined by CFD simulation. Simulation of fire scenarios have been done by pyrosim software that is a user graphical interface for FDS . This software is a professional tool for simulating fire and can animate the results. An innovation in this research is simulating many species of gases from a passenger train fire same as carbon dioxide, nitrogen dioxide, hydrogen cyanide, hydrogen chloride. Also the distribution of temperature and carbon monoxide are defined. The effects of many parameters same as transverse location of fire in tunnel, damper of ventilation station, separation wall in tunnel, start time of emergency ventilation and distribution of gases and temperature in tunnel height are analyzed in this research. From results the maximum allowed time for evacuation of passengers from train and tunnel are defined. Another innovation in this research is determination of concentration of all gases in some points in tunnel. Furthermore the effect of ventilation conditions on species concentration is simulated in this work. When the tunnel ventilation system is off, the train burns at under ventilated conditions and when the ventilation system is on, burning is at well ventilated conditions. At under ventilated mode, the rate of toxic species generation from fire source is greater. At last the emergency ventilation scenarios have been designed and emergency exit instruction has been defined.
