Numerical Simulation Of Smoke Flow In Subway Fires

As an important part of the modern urban transportation facilities,subway is playing a more and more important role in our daily life.Subway system can provide convenient transportation for citizens,however,tragedy of subway fire is horrified.With the rapid development of the subway in recent years,the characteristics of subway fire are more complex than that of conventional building fire,furthermore,because of the frequent occurrence of terrorist attacks,it is necessary for the governments pay more attention to the subway fire.In view of this,based on the numerical simulation method of computational fluid dynamics,sections are set at the middle of the train or platform and 1.6 meter which is the general height of adults' nasal is adopted as the test height.Furthermore,three test points along the evacuation routes are chosen to obtain temperature,CO2 concentration and soot concentration,including the end of the carriage,the platform screen door(PSD),the middle of platform and stairs in side-platform subway station analyze the smoke flow distribution,temperature field,visibility and velocity field.Based on the comparison between the measured data and the relevant specifications,the merits of the smoke control effect are analyzed,and suggestions of subway fire safety and optimal solution of human evacuation are provided in the thesis.The main research works and achievements are as follows:1.When the carriage on fire and parked in the platform,the smoke control effect of platform ceiling ventilation under air supply pattern and smoke exhaust pattern are investigated.The results show that smoke control effect of smoke exhaust pattern is better for smoke control and human evacuation.Additionally,the relations between temperature at PSD and heat release rates under smoke exhaust pattern are analyzed.2.When the fire on the passenger waiting area near the PSD and parked in the platform,the smoke control effect of platform ceiling ventilation under air supply pattern and smoke exhaust pattern are investigated.The results show that smoke exhaust pattern is better for smoke control in the carriage at initial stage of subway fire.The air supply pattern is better for smoke control in the carriage at later stage of the fire.Therefore,at initial stage of subway fire,smoke exhaust pattern should be adopted.After the train leaves the platform,the platform ceiling ventilation should change to air supply pattern,so that most of smoke can be discharged by tunnel exhaust device.3.When the carriage on fire and parked in the platform,smoke screen in joints of two carriages is installed to compare the effect on smoke flow in carriage.The results show that smoke screen can effectively inhibit the smoke flow.Additionally,under different heat release rates,the relations of temperature at the end of the carriages with and without the smoke screen are analyzed,and temperatures in different heights of the carriage with smoke screen are compared.To be concluded that,the lower the heat release rate of fire is,the better control effect of smoke screen has.If the distance is much farther from the smoke screen,then the effect of smoke suppression will be better.