Research On The Smoke Flow Mechanism Of The Fire Train Entering The Rescue Station At The Tunnel Portals

With the development of Sichuan Tibet railway construction,a large number of extra long railway tunnels and tunnels have emerged in China.By the end of 2020,the number of extra long railway tunnels(groups)with a length of more than 20 km has increased to 11,with a total mileage of more than 262 km.Tunnel entrance emergency rescue station is an important rescue and evacuation place in case of fire in tunnel group of special long railway.It is an important way to explore the smoke spread law and control strategy of fire train when emergency stop at tunnel entrance rescue station is an important way to ensure that the passenger train can carry out evacuation rescue quickly,safely and effectively in case of fire accident in tunnel group.In this paper,the three-dimensional dynamic grid model of tunnel mouth emergency rescue station is established to study the influence of different stop positions and length of open section on the development characteristics,smoke spread and temperature field distribution of the fire compartment under the influence of piston wind.In addition,the paper studies the air supply and exhaust strategies of rescue station when the fire compartment stops in the upstream and downstream driving tunnels by numerical analysis.The specific conclusions are as follows:(1)When the fire compartment of the train stops in the upstream driving tunnel,the smoke concentration in the upstream rescue station is higher in the early stage of parking.Under the action of piston wind,the smoke of the driving tunnel spreads to the downstream of the fire source within 45 s.However,with the decrease of piston wind speed,the fire source smoke will appear in the upstream tunnel after 170 s of parking,and the upstream rescue station will be filled with high concentration smoke within 6min after stopping;When the fire compartment of the train stops in the middle of the open section,some of the cars still stop in the tunnel,and the smoke in the tunnel can be discharged within 60 s under the action of piston wind,and there is no phenomenon of smoke reverse flow at the tunnel entrance at the upstream and downstream;When the fire compartment of the train stops in the downstream tunnel,the direction of piston air flow of the downstream tunnel is to blow to the downstream of the fire source,and the smoke from the fire source will spread downstream.When the train stops for 30 s,it will be covered by high concentration smoke,which will hinder the evacuation and rescue work of the personnel.(2)The results show that the shorter the length of the open section of the tunnel exit rescue station,the more serious the smoke intrusion is in the downstream driving tunnel.If the open section is less than 100 m,the smoke in the open section of the train will be blocked by the suction of the smoke in the downstream driving tunnel under the action of piston wind.(3)By establishing a numerical model,this paper analyzes the air supply and exhaust strategies under the two situations of the train fire carriage parking in the upstream and downstream tunnels for rescue and evacuation,and puts forward the corresponding more reasonable air supply and exhaust schemes,which are as follows: when the train fire carriage parking in the upstream tunnel for evacuation and rescue,158m~3/s fresh air is pressed into the opening of the open section of the safe tunnel,The fresh air volume of 316m~3/s at the exit of the safety tunnel can meet the requirements of evacuation in 60s;When the train on fire stops in the downstream tunnel for evacuation and rescue,156m~3/s fresh air is pressed into the entrance of the open section of the safety tunnel,and 260m~3/s fresh air is pressed into the entrance of the safety tunnel,which can meet the requirements of personnel evacuation in 30 seconds.