Influence of mechanical ventilation-shaft connecting location on subway tunnel ventilation performance

Subways are widely used for public transportation in major cities and require efficient ventilation systems to maintain indoor air quality in the subway tunnel. A subway tunnel was investigated to understand the airflow inside the tunnel, and to improve its ventilation system. The steady three-dimensional airflow in the tunnel was analyzed using ANSYS CFX software to solve Reynolds-averaged Navier–Stokes equations. The ventilation performance in the subway tunnel was investigated with respect to the connecting location of the mechanical ventilation shaft by analyzing mass flow rate through the ventilation-shafts and the airflow in the tunnel. The airflow in the tunnel and the mass flow rate in the shafts were investigated when the guide-vane, the porous zone and the air-curtain were installed in the subway tunnel system. The discharged-air was higher at ventilation-shaft 2 which was connected to the top wall of the tunnel than that of the ventilation-shaft 1 which was connected to the side wall of the tunnel. The numerical results suggested the connecting location of shaft 2 as the optimum connecting location.