Research on the Prediction of Piston Air Exchange Rate during Train Operation in Subway Tunnels

At present, the research on characteristics of piston wind flow in subway tunnel is mostly based on in-situ measurement or CFD simulations, but the conclusion lacks universality. A one-dimensional simulation model of ventilation network system related to one-station two-sectional tunnel was established by using the software of IDA tunnel, based on parameters of an actual subway line in practice to investigate the impact of five factors, including train length (60 m ~ 360 m), travel speed (10 m/s ~ 100 m/s), departure interval (120 s ~ 600 s), tunnel length (1000 m ~ 10000 m), and blockage ratio (0.1 ~ 0.9), on dynamic piston wind speed and ventilation rates within the tunnel. The correctness of the simulation results was verified. Finally, grey correlation analysis was conducted to reveal the influential intensity of each factor on the ventilation rates. Fitting correlation formulae of the maximum piston wind speed and of the piston wind ventilation rates of the tunnel were obtained by multiple regression analysis method. The results indicate that: The influential intensity of blockage ratio, train speed, tunnel length, train length and departure time interval on the ventilation rates decreases in order; The proposed fitting relationship has a good agreement with the simulated calculation values and previous research results, indicating that the fitting correlation is reliable.