In the vicinity of the inlet centrifugal "24V DC Cooling Fan" in front of the fan impeller, a group set up adjustable guide vane angle (stationary vanes) to adjust the fan running for traffic. This guide vanes called inlet guide vanes or inlet diffuser, or the leader leaves. Common "24V DC Cooling Fan" inlet guide vanes with axial guide and simple deflector two inlet guide vane adjustment method is widely used in the centrifugal fan. Maximum with minimum loss of energy; for the impeller vanes, as well as the kinetic energy is converted into rotational movement of the pressure energy effect. After setting the impeller vanes, said after the wicket. After wicket set Axial "24V DC Cooling Fan" fans and axial commonly used. Set in front of the impeller vanes called leading leaf. Currently, medium and small axial fan is often used leading leaf devices.