Study On Smoke Characteristics Of Emergency Rescue Station In Extra Long Double Tunnel Single Track Railway Tunnel

In recent years,the increasing number of long tunnels in China has brought great convenience to people’s transportation.However,due to the narrow and long tunnel closed structure and limited ventilation conditions,if a fire accident occurs and is not effectively controlled,it is more likely to cause serious casualties and property losses,resulting in huge social impact.The research shows that the casualties in the tunnel fire accidents are mainly due to the inhalation of a large number of smoke leading to poisoning,coma and even suffocation.Therefore,it is more and more important and urgent to study the characteristics of smoke and the safety evacuation of people under various ventilation modes when a tunnel fire occurs.Rescue stations should be set up in long tunnels in China.The rescue station refers to the setting of multiple cross channels within a certain range of the super long railway tunnel,with short distance between the cross channels,which connect the fire tunnel with the parallel tunnel or service tunnel.It can make the train stop in this range after the fire in the tunnel,and the personnel can enter the safety area through the cross channel.Xinguanjiao tunnel,with an altitude of 3324.05-3494.45 meters,is the longest railway tunnel in China and the longest plateau railway tunnel in the world.Taking Xinguanjiao tunnel as an example,this paper studies and analyzes that the original ventilation mode of Xinguanjiao tunnel in case of fire is to set two jet fans in each cross passage to ensure that the wind speed in the opposite direction to the direction of personnel escape reaches 2m/s,and 14 groups of jet fans about 15 km from both ends of the tunnel respectively provide certain wind pressure for the tunnel.Limited wind pressure provided by fans due to the long distance,there is still a certain risk in case of fire with high power.The way of smoke exhaust is to set up a shaft every 100 m in the tunnel emergency rescue station,and set up a smoke exhaust channel at the top to connect with No.6 inclined shaft.The ventilation mode designed in this paper is that the jet fans at both ends of the tunnel do not need to be opened and the jet fans do not need to be set in the cross passage.The jet fans are set at both ends of the rescue station,In case of a fire,this ventilation mode can not only ensure that the positive pressure in the cross passage and the wind speed in the opposite direction of the escape direction reach 2m / s,but also provide the wind pressure to control the smoke within a certain range,so as to ensure that the indexes at the characteristic height of the human eye during the escape reach the safety limit.It can also further reduce the number of jet fans and energy consumption.So in this paper,the location,quantity and direction of the jet fans at both ends of the rescue station are simulated under different working conditions,and the optimal ventilation mode for different working conditions is obtained.In view of the above ideas,this paper takes xinguanjiao tunnel as an example to establish a geometric model,analyzes and compares the characteristics of fire smoke under different working conditions and different ventilation conditions,obtains the optimal ventilation mode under each working condition,and provides reasonable suggestions for the safe evacuation of people and the design of tunnel ventilation mode.The following are the main conclusions of this paper:(1)When the power of the fire source is 15 MW and located in the middle of the rescue station,through analysis and comparison,it is concluded that the eighth ventilation mode[the jet fans on the right side of the fire tunnel in the rescue station supply air to the inside,and the jet fans on the left side(two on the outside)supply air to the inside] can better meet the safety limit requirements and is more conducive to the safe evacuation of people;(2)When the power of the fire source is 50 MW and located in the middle of the rescue station,through numerical simulation and analysis,it can be concluded that: under the fourth ventilation mode[the jet fans on the right side of the fire tunnel in the rescue station supply air to the inside,and the jet fans on the left side(two on the outside)supply air to the inside],each index can better meet the safety requirements and save energy consumption;(3)When the power of the fire source is 15 MW and located on the right side of the third cross passage of the rescue station,the four ventilation modes are compared and analyzed.The indexes of the second ventilation mode[the jet fans on the right side of the fire tunnel in the rescue station(two on the outside)supply air to the inside,and the jet fans on the left side supply air to the inside]and the third ventilation mode[the jet fans on the right side of the fire tunnel in the rescue station supply air to the inside,and the jet fans on the left side(two on the outside)supply air to the inside]basically meet the safety requirements,and they are all better and optional schemes;(4)When the power of the fire source is 50 MW and located on the right side of the third cross passage of the rescue station,the third ventilation mode[the jet fans on the right side of the fire tunnel in the rescue station supply air to the inside,and the jet fans on the left side(two on the outside)supply air to the inside]is better under this condition;(5)When the fire source is located on the left side of the third cross passage on the right side of the rescue station,the second ventilation mode[the jet fans on the right side of the fire tunnel in the rescue station(two on the outside)supply air to the inside,and the jet fans on the left side supply air to the inside]is better than other ventilation modes,whether the fire source power is 15 MW or 50 MW.This paper provides reference and suggestions for the design of ventilation mode and the safe evacuation of personnel in extra long railway tunnel.