Study On Smoke Exhaust Effect And Alternative Ways Of OTE System In Metro

For shielded door subway stations,almost all domestic underground station tunnels are designed with semi-horizontal ventilation,that is,a track-top exhaust system is set up to provide normal operation ventilation and fire smoke exhaust for the track area.There are a series of problems such as tight construction periods,difficult implementation,and safety.From the perspective of its functionality,if the track-top air duct is canceled,the burden of smoke exhaustion can be solved by other means,there is no need to set up the track-top air duct.This paper selects a standard underground two-story side subway station,and uses numerical simulation to study the fire smoke characteristics and the safety of evacuation passageway for trains in rail-traveled areas with and without track-top air ducts.In this paper,first,domestic and foreign relevant subway design standards are used to formulate the control parameters of smoke parameters during a fire in the track area.According to the general structure of a standard shield door subway station,a 3D model of a side station is established using PyroSim software.Based on the existing design conditions,the smoke diffusion characteristics and the safety of the evacuation passageway at different fire positions of the train when the track-top air duct is set are analyzed,and the smoke control effect of the track-top air duct is evaluated.After canceling the track-top air duct,this article proposes a bilateral smoke exhaust scheme by using tunnel ventilation fans.When a fire occurs,the three shielded doors closest to the fire source are closed,and the other shielded doors are opened.The cross-section of the track area under different train speeds and the smoke generation rate were selected for research,and the safety of the evacuation passageway during a train fire in the track area under the new smoke exhaust method was analyzed.At the end of the article,a one-dimensional simulation method was used to establish a standard subway line without track-top air duct.Based on the model,the air volume of the tunnel mouth under different ventilation modes was calculated,and the above-mentioned calculation results are used to determine the configuration of the tunnel ventilation system under the cross-sections of different track areas.The results show that:(1)For fires at different locations of the train in rail area,the smoke control effect of the existing track-top smoke exhaust is quite different.When a fire occurs outside the train,the existing smoke exhaust system can effectively control the smoke diffusion,and the evacuation passageway are not affected;When a fire occurs inside the train,the area near the fire source of the platform does not meet the conditions for safe evacuation of personnel,and the smoke control effect is not good.When the fire is located in the middle of the train,the track-top air duct plays a major role in exhausting smoke.When the fire is located at the end of the train,the smoke exhaust effect of tunnel ventilation fan is more obvious.(2)When the track-top air duct is canceled,the safe evacuation condition can be satisfied in the escape passageway when the amount of smoke discharged at the tunnel entrance reaches a certain value under the new smoke exhaust mode.When the smoke production rate of fire source is 0.042kg/kg,the minimum smoke emission at the tunnel entrance satisfying the requirements of safe evacuation under each section should be greater than 28 m~3/s;when the smoke production rate of fire source is 0.1 kg/kg,the minimum smoke emission at the tunnel entrance under different sections of rail track area should be in the range of 30 m~3/s to 45 m~3/s.(3)Under the condition of train fire in rail track area,the minimum smoke emission at tunnel entrance can be achieved by increasing the air volume of tunnel ventilation fan,opening adjacent tunnel ventilation fan and adding jet fan.In practical engineering design,the influence of platform structure,train type and tunnel structure on ventilation system should be considered comprehensively,and the ventilation configuration mode should be reasonably selected.