Evacuation Study Of Middle Train Fire In Tunnel Under Longitudinal Ventilation

Longitudinal ventilation mode is widely used in railway tunnel ventilation because of its simplicity and ease of implementation.The critical wind velocity can effectively control the backflow of smoke and ensure safe evacuation to the upstream.However,when the middle of the train is on fire,the longitudinal critical wind velocity ventilation mode may destroy the stratification of smoke,so that the entire section downstream of the tunnel is filled with smoke,causing people downstream unsafe.Therefore,it is necessary to study the evacuation safety when the middle of the train is on fire under the longitudinal ventilation mode,to explore the reasonable smoke control mode to meet the safe evacuation requirement.Based on the safe evacuation criterion,this paper uses methods of theoretical study and numerical simulation to analyze the evacuation safety when the middle of the train is on fire in tunnel.According to the smoke distribution,the reasonable smoke control mode is discussed to meet the safe evacuation requirement.The evacuation process is studied,and the evacuation strategy is put forward.Firstly,the evacuation time model is established for the parking mode of evacuation in tunnel.The safe evacuation criteria is determined to provide a basis for safety analysis.Secondly,a three-dimensional calculation model of smoke flow in tunnel fire is established.The feasibility and effectiveness of longitudinal smoke control mode based on limiting wind speed for fire evacuation in the middle of trains are presented and verified,through the analysis of the smoke distribution and the available safe evacuation time(ASET)in the tunnel with different running speed of train and different ventilation control conditions.At last,the evacuation time of the tunnel fire is theoretically calculated and the evacuation model is established to verify the accuracy of the theoretical calculation and model simulation results.The simulation calculation model is corrected according to the calculation results of the tunnel smoke distribution.And through simulation analysis,the evacuation strategy is further proposed when the fire located in the middle of the train and the train was forced to stop in the tunnel.