The working principle of tunnel axial fan and jet fan is different. When the impeller rotates, the gas enters the impeller axially from the inlet, is pushed by the blade of the impeller and makes the energy of the gas rise, and then flows into the guide vane. The guide vane changes the deflected air flow into axial flow, at the same time, the gas is introduced into the diffuser, and the kinetic energy of the gas is further converted into pressure energy, and then introduced into the working line. Generally, the blades of axial flow fans can rotate at an Angle. Most axial flow fans are equipped with a set of blade hydraulic regulation devices. When the fan is running, the installation Angle of the blade can be adjusted through the blade hydraulic regulating device, and kept at a certain Angle, so that it still has a high efficiency in variable working conditions. The jet fan is usually hung on the top of the tunnel or installed on the side wall of the tunnel. The tunnel itself is used as the air duct. When the fan works, it can generate a higher thrust from the given energy.