Experimental Analysis And Numerical Simulation Of Radiation Ignition Behavior Of Subway Cables

In recent years,the rapid development of the world economy and the acceleration of urbanization,the traffic of many large cities is overwhelmed,and the development of public transportation has become an important task in many countries in the world at this stage.Therefore,more and more cities are beginning to build subways.As a highefficiency,low-energy,low-pollution mode of transportation,the subway has gradually become an important part of urban transportation.In the rapid development of the subway,the safety of the subway has become a concern in many fields such as sociology and fire science.In recent years,major subway fire accidents around the world have also caused people's awareness of subway fire safety..After a fire in a subway tunnel,if it cannot be effectively controlled within a certain period of time,the fire will cause irreversible serious consequences.In subway fires,fire loads are mainly divided into two types,fixed and mobile loads.Mobile loads are mainly subway trains,passengers in trains,etc.,which have large uncertainties and are difficult to quantify.The fixed load mainly includes the subway cable,equipment and facilities in the subway tunnel.It is in the same state for a long time after the subway is established.It will not change frequently,and the cable has the characteristics of continuous laying.Once ignited,the flame will Spreading inside the tunnel caused the expansion of the fire.Therefore,the author chooses two types of power cables radiated from the Beijing subway,FS/FY S-WDZA YJY6 35 kv cable and FS/FY-WDZA EYYR 1500 v cable as research objects.With cone calorimeter,45kw/m2 and Radiation power of 50kw/m2 is used to conduct radiation ignition test on the cable,and the data such as ignition time,heat release rate,smoke generation rate,mass loss rate and carbon monoxide concentration are obtained.After research,it is found that:(1)The ignition time,heat release rate,smoke generation rate and carbon monoxide concentration of the same cable are greatly affected by the radiant heat change,while the mass loss rate is not significant;(2)Under the same conditions of ignition and radiant heat,the ignition time,heat release rate,mass loss rate,smoke generation rate and carbon monoxide concentration of the two cables are different.Taking the above experimental data as the boundary condition of FDS simulation,and setting two different ventilation conditions of 2m/s and 3m/s respectively,the cable fire simulation of some sections of the tunnel is found:(1)After the cable in the tunnel is ignited,it will continue to burn,and at the same time,due to the existence of the exhaust system,it will continue to spread downward;(2)When the ventilation speed in the tunnel is 2m/s,the flue gas will reflow;(3)Under different ventilation conditions,the spread of fire,the spread of smoke,visibility and temperature changes are all different.The experimental phenomena,data and simulation results studied in this paper are expected to provide reference for the evacuation and ventilation and smoke design of subway tunnels.