| In recent years,China’s high-speed railway industry has made remarkable achievements and ensuring the safety of train operation is the basic requirement and primary task of railway transportation.Fire is one of the most common,dangerous and destructive disasters for high-speed trains running in tunnels.When the interior of high-speed train is on fire,the window glass may be broken by passengers or heated to break,forming a vent,and then forming an fire overflow.Combined with the effect of longitudinal ventilation of the tunnel,it is easy to cause greater casualties and structural damage of the tunnel,Therefore,the research on the behavior characteristics of high-speed train fire overflow in tunnel can provide theoretical guidance and basis for the emergency disposal and rescue of high-speed train,and play a positive role in ensuring the safety of high-speed train.In this thesis,the accuracy of FDS numerical simulation method is verified by comparing the results of numerical simulation and small-scale model experiment.Taking the process of high-speed train compartment fire and window opening as the research object,the evolution law of high-speed train compartment fire overflow under the effect of tunnel longitudinal ventilation is studied by theoretical analysis and numerical simulation,and the influence mechanism of wind field characteristics on high-speed train compartment fire overflow smoke spread is revealed,The critical velocity and length of the countercurrent,and the temperature distribution of the smoke inside the carriage and on the ceiling and vertical wall of the tunnel were obtained.When the heat release rate of fire source increases to a certain value,the critical wind speed tends to be steady.The prediction model of fire HRR and critical wind speed is established: when the fire HRR is small,the dimensionless fire HRR and dimensionless critical wind speed are power function distribution;When the dimensionless fire HRR is greater than 0.16,the dimensionless critical wind speed is steady at 0.40.The countercurrent length of smoke induced by fire overflow at the opening of high-speed train in tunnel decreases with the increase of longitudinal wind speed,and increases with the increase of fire HRR;The relationship between dimensionless longitudinal wind speed and dimensionless countercurrent length of flue gas satisfies exponential distribution;The dimensionless evolution model of fire HRR,critical wind speed and countercurrent length are established.Through the research on the temperature distribution of smoke inside the carriage,tunnel ceiling and vertical wall,it is found that the maximum temperature of tunnel ceiling increases with the increase of fire HRR;When the ventilation in the tunnel reaches the critical wind speed,the temperature at the ceiling downstream of the tunnel first increases and then decreases with the distance from the fire source;For the temperature of the interior ceiling,the temperature decreases with the increase of the distance from the fire source,and presents a power exponential distribution law;The temperature of tunnel wall increases with the increase of heat release rate of fire source,and reaches the maximum at the height of about 3m;The maximum temperature at the tunnel wall is exponentially related to the fire HRR,opening size and characteristic length.This study focuses on the characteristics of smoke flow and temperature distribution induced by fire overflow in high-speed train fire accidents in tunnels,enriches the research results of high-speed train fire safety in tunnels,and provides a reference for fire safety and personnel rescue of high-speed train fire in tunnels,which is of great significance. |
