"Axial Fan" rotating stall reverse the direction of rotation of the impeller angular velocity is less than the rotation of the impeller angular velocity (speed of about 30% -80%), and blade stall is still very high frequency effects. At the same time, the role of the blade back and forth off the flow of pressure there is a certain variation width. Thus, in addition to affecting the fan rotating stall work, its performance fell outside; also due to the blade by a high-frequency alternating forces have a certain amplitude, leaving the blade fatigue damage; when the alternating force when the frequency is equal to or near the natural frequency of the blade, the blade will resonate even the blade fracture. In order to prevent axial fans produce a rotating stall, the fan should ensure that the selection and operation of the fan into the fan operating point is not unstable work area.