Tunnel variable frequency fans are suitable for vertical exhaust systems in tunnel construction such as roads, railway lines, and subway stations. Because the tunnel frequency conversion fan is generally suspended on the top or both sides of the tunnel construction, it does not occupy the total traffic area, and does not need to build additional air ducts. The civil engineering is low-cost, and the installation, operation, and maintenance are simple. It is an economical ventilation method.

   We all know that the reasonable kinetic energy formed by the centrifugal impeller of axial flow fan includes negative pressure and gas pressure. The negative pressure is used to overcome the frictional resistance of the pipeline network, and the gas pressure is used to transport the cyclone; the effective kinetic energy generated by the tunnel inverter fan is only the gas pressure at the inlet and outlet of the centrifugal fan, which is used to drive the cyclone in the tunnel construction.

   The negative pressure generated by the water jet impeller is only suitable for breaking the internal flow resistance of the fan itself, and has nothing to do with improving the ventilation in the tunnel. Generally, the electric power of the frequency conversion fan in the tunnel is the rated power of the motor caused by the centrifugal fan multiplied by the exhaust air volume, while the output power of the fan is only the reasonable gas pressure at the outlet of the centrifugal fan multiplied by the exhaust air volume. Therefore, when designing the aerodynamic force of the tunnel frequency conversion fan, its negative pressure should be reduced as much as possible.