Abstract: The author conducts a case study considers a metro station in Wuhan, China, where a smoke exhaust system that integrates rail top fans and large system fans is utilized. The aim is to investigate the changing characteristics of the flow field during train overrun conditions through on-site tests conducted as trains pass over the station. The test results are used to validate the numerical calculation method for the full-size station, where the visibility, CO concentration, and temperature on the platform in the event of a baggage fire are assessed. In addition, the effectiveness of smoke control on the platform during train crossings is evaluated. The results reveal the following: (1) In the absence of a train, the downward wind speed at the escalator ranges from 1.8 to 3.5 m/s. (2) When a train crosses the station at 40 km/h, the downward wind speed at the escalator experiences three phases: an initial decrease, followed by an increase, and then a final decrease, ultimately reaching approximately 0.5 m/s. (3) The train′s passage significantly affects the wind speed at the escalator, with the timing of these changes closely linked to the train′s travel time. The smoke simulation results demonstrate that: (1) In the absence of a train, the smoke control measures are effective. (2) When a train crosses the station at 40 km/h, the collaborative smoke exhaust system performs well, effectively limiting the spread of smoke. However, localized areas near the L5 escalator, which is close to the fire source and constitutes approximately 10% of the platform area, show elevated levels of CO concentration, reduced visibility, and abnormal temperature readings.

Key words: metro platform, platform fire, train passage over station, collaborative smoke exhaust system, numerical simulation, downward wind speed at escalator