Impact of the Heat Release Rate to the Flow Characteristics of Fire Smoke in Subway Tunnel Under the Effect of Piston Wind

Once a running metro train catches fire, it should try to get to the front platform for evacuation. But it does not exclude one extreme situation that the train stops in the tunnel when it is damaged too badly to keep running. Thus, this paper established a precise model of subway train, tunnel and platform using the dynamic mesh method for the simulation of the train movement with the train blocking effect being considered, to study the impact of heat release rate (HRR) of fire load to smoke flow characteristics in tunnel when the fire source located in the bottom of the first carriage. Train runs at 19.5m/s (nearly 70km/h) then slows down to stop in the center of tunnel when a fire occurs, the HRR is chosen to be 2.5MW, 5MW, 7.5MW, 10.5MW, respectively. By comparing the influence of piston wind after deceleration, this paper investigates the velocity field and temperature field in tunnel. The research results show that with the same running speed, as the HRR increased by 2.5MW: 1. the piston wind downstream of the tunnel would increase less than 1m/s; 2. the smoke front would reach 60m further if HRR is greater than 5MW; 3. temperature in car1-roof increases nearly 89%, 257%, 441% relative to 2.5MW; 4. the moment backflow to upstream side of fire source advance from 212s to 180s, 163s, 150s respectively; 5. the temperature at the same position of the tunnel increases nearly 190 degrees C.