Real-vehicle Testing and Numerical Simulation of Dynamic Ventilation Characteristics of Metro Trains

［Objective］The airflow variation of metro train operating in tunnels affects the air quality and ventilation efficiency within the compartments. Therefore, it is necessary to study the ventilation characteristics of metro train compartments when operating in tunnels. ［Method］Through real-vehicle testing, the dynamic variation of the ventilation parameters such as fresh air volume, exhaust volume in train operation state is studied, and the dynamic performance of the ventilation system is analyzed. Based on the in-situ test data, numerical simulations of the train ventilation system working state at different operating speeds are conducted to further analyze the ventilation characteristics of metro trains during operation. ［Result & Conclusion］The supply and return air in a same compartment are uneven. The supply and exhaust air volumes of each compartment are unbalanced, with the supply air volume decreasing from the train front to the rear, and the return air volume increasing in the same direction. As the train accelerates, the return air volume in the air duct gradually increases, while the fresh air volume gradually decreases. When the train speed reaches 40 km/h, a significant reverse fresh air phenomenon occurs in the air duct. During train acceleration, the fresh air inlet exhibits a larger and continuously decreasing negative pressure, while the return air inlet exhibits a smaller and less fluctuating negative pressure. The increased pressure difference between the fresh air inlet and the return air inlet is the cause for the fresh air reversion.