Numerical investigation on cooperative platform smoke exhaust technology of rail-top exhaust system in subway station fires

Subway platform fires have the characteristics of rapid smoke spread, difficulties in smoke exhaust and in evacuating personnel. To investigate the impact of collaborative smoke exhaust design with rail-top system on the smoke exhaust performance during subway platform fires, a series of full-scale numerical simulations were conducted by taking a real subway station as an example. The variation patterns of downward velocity at stairway, as well as temperature, CO concentration and visibility at the clear height were revealed. The results indicate that the downward velocity at stairway gradually increases as the rail-top exhaust system airflow increases. The relationship between downward velocity and rail-top exhaust system velocity was proposed. When the rail-top exhaust system velocity reaches 70 m 3 /s, it can meet the requirement of a 1.5 m/s downward velocity at stairway. Based on the result of temperature, CO concentration, visibility indicators and the calculated smoke exhaust volume of the exhaust system according to specifications, using a rail-top fan airflow of 70 m 3 /s (252,000 m 3 /h) for collaborative smoke exhaust can meet the requirements for personnel evacuation. The results can give insights for the emergency evacuation planning, smoke control and firefighting activities in subway stations.