Study On Flowing Mechanism Of Fire Fume Considering Coupling Effect Of Running Fire Train And Piston Wind In Rescue Station

Based on the Gaoligongshan super-long tunnel in Dali-Ruili Railway,this paper studies the distribution of flow field and the flowing mechanism of fire fume when the fire train is speeding to and stopping at the rescue station in the middle of the tunnel.The theoretical analysis,numerical simulation,laboratory model test and other methods are applied.The research results could provide a theoretical basis for solving the problems of fire characteristics and smoke control and evacuation in the long railway tunnel,and they have important guiding function and practical significance to guarantee the safe evacuation of personnel in the long railway tunnel fires.The main research results are as follows:(1)Based on the theory of fluid mechanics,the mechanism of the piston effect during the emergency travel of the train running to the rescue station is explored.The piston effect force at different positions of the tunnel at different operating stages of the train is analyzed,and the fluid flow control equations for running fire train-piston wind coupling is established;(2)A laboratory model test platform based on fire train motion-piston wind coupling was established.During the evacuation process of the extra-long tunnel fire train and stopping at the rescue station,the airflow field,pressure field and smoke propagation law in the tunnel were analyzed,and the dynamic mesh technology of Fluent software was used for numerical simulation.The model test results and the numerical simulation results have the same trend,and the degree of coincidence is good.It can be proved that the two methods of model test and numerical simulation can more accurately describe the flow of smoke flow in the rescue station based on the motion-piston-wind coupling of fire trains;(3)The theoretical calculation formula of the piston wind in the rescue station during the train running to and stopping at the rescue station is proposed.The numerical simulation method is used to reveal the change law of the flow field in the tunnel.The results reveal the influence of train length and train speed on the piston wind in the tunnel;(4)The numerical simulation method is used to analyze the smoke characteristics in the tunnel during the train running to and stopping at the rescue station,reveal the smoke diffusion law in the rescue station,and reveal the impact of the fire on the piston wind flow field in the tunnel.The research method is applied to engineering examples,and the distribution law of smoke flow in the rescue station of the example tunnel is studied;(5)Based on the critical Froude number principle of tunnel fires,the theoretical analysis of the smoke control in evacuated transverse alleyways after the fire train stops at the rescue station is carried out,and the theoretical calculation formula of the critical velocity for suppressing the smoke intrusion in evacuated transverse alleyways is derived.With the method of small scale model test,the smoke control effect using two modes was studied.On this basis,a reasonable smoke control strategy when the fire train stops at the rescue station is put forward.