Study On The Fire Smoke Characteristics Of Long Railway Tunnel Under Consideration Of Train Blockage Effect And Fire Source Location

In recent years,China has invested hugely in railway construction,and there have been a large number of railway tunnels under operation,construction and planning.Meanwhile,the rapid development of railway tunnels has also brought serious fire safety problems.Especially for a number of railway lines with relatively long tunnels in the plateau areas,such as the Sichuan-Tibet railway,the smoke in the tunnel is difficult to discharge quickly during the fire,so the fire safety problem is more prominent,which will cause serious accidents easily.In view of the serious consequences caused by tunnel fire accidents in various countries and the speciality of space in the long railway tunnels,at present,the researches on fire safety of long railway tunnels are still relatively lacking,so the characteristics of fire smoke movement in long tunnels still need to be studied in depth.This paper,focusing on the fires in the section of the long tunnels and the smoke spread laws and control effect of the long railway tunnels,carried out relatively comprehensive test studies and full-scale numerical simulation verification on some typical fire conditions,for example,equipment fire and train section fire in the tunnel,including the fire outside and inside the train.The researches of this paper provide data support for fire smoke control,personnel evacuation and rescue design in extralong railway tunnels,which has practical value and promotion significance to fire safety in extra-long railway tunnels.In this paper,several methods,including data research,model test,numerical simulation,and theoretical analysis,are comprehensively used,through smoke temperature field,smoke spread distance,critical wind speed and other parameters to quantize the fire smoke spread characteristics,to carry out in-depth analysis on the following different fire scenes.The main researches and results are as follows.The law of the fire smoke maximum temperature rise and longitudinal attenuation of the vaults is studied under the conditions of lateral locations of different fire sources,in the center of the tunnel and on one side of the tunnel.It is found that the maximum temperature of the fire source in the center is higher than the source on one side in the tunnel without longitudinal ventilation,and the difference between the two locations is increasing with the increasing of the heat release rate.under the longitudinal ventilation,the maximum temperature in both locations is basically same.By introducing the wind speed Froude Number to characterize the influence of longitudinal ventilation on the maximum temperature,the model of the highest smoke temperature,coupling the longitudinal ventilation and the fire source lateral location,is established.Based on the relationship between the newly proposed longitudinal temperature attenuation coefficient and the Froude Number of the longitudinal wind speed,a new tunnel vault temperature attenuation formula under the condition of ventilation is established.(Chapter 3)The smoke spread laws of tunnel fires under different fire source location and different train lengths are studied.It is found that,under the same heat release rate,longitudinal ventilation rate and train length,the highest temperature rise and the reverse flow length of the smoke in the carriages of center trains are higher than theirs in the carriages of end trains.The influence mechanism of fire position and train length on the fire smoke spread distance and maximum temperature of the tunnel is analyzed.Combined with the classic models of the former,the dimensionless relationship between the tunnel fire smoke backflow length,the maximum temperature and heat release rate,and the longitudinal ventilation wind speed is established under the conditions of different train carriage fire positions and train lengths.(Chapter 4)Focusing on tunnel fire smoke spread characteristics in the train carriage,the tunnel fire shrinkage tests are carried out under various conditions such as different train carriage door and window opening types under the condition of fire in the carriage.The law of fire in the carriage are found under different opening types of door and window on the smoke spread of the tunnel fire.The model of the highest temperature rise of the tunnel fire,and the dimensionless relationship between the heat release rate and the longitudinal ventilation wind speed are established under the condition of different door and window opening types in the carriage.In addition,the laws of temperature distribution in the tunnel under the conditions of non-blocking,train blocking and carriage internal fire are compared and analyzed as well.(Chapter 5)Based on background of single-hole and single-track railway tunnels,full-scale numerical models are built by the FDS software,and full-scale numerical simulation researches are carried out on two common fires,train end fire and carriage fire.Further,studying the basic law of smoke spread in tunnel fire.Meanwhile,the effects of train length on the smoke backflow length are studied by setting up different lengths of general-speed trains.At the same time,compared with the test data of shrinkage size,the theoretical model of shrinkage size test is verified,providing the theory and data support to actual tunnel fire smoke control as well.(Chapter 6)...