Axial fans are widely used in Chinese enterprises. According to the recommendations of the international organization for standardization, noise in industrial areas should not exceed 85dB. However, the axial noise of the axial-flow fan 1m can reach 90 to 110dB in the absence of sound insulation. The industrial noise produced by axial flow fan during the actual operation will have adverse effects on the production environment and the physical and mental health of the operators.
The main noise of axial fan is aerodynamic noise, in addition, mechanical noise and electromagnetic noise are secondary in axial fan.
The aerodynamic noise of axial fan mainly consists of two parts: rotating noise and eddy current noise.
The rotational noise exhibits discrete peaks in the noise spectrum. The rotation noise depends on the load of the blade or the node flow of the fan. When the blade load in the large flow area is relatively small, the rotating noise accounts for the major part of noise.
Eddy current noise, also known as turbulence noise, is represented as a wide-band continuous spectrum in the noise spectrum. The eddy current noise depends on the relative velocity of the rotor blades, the clearance between the housing and the blade, and the dynamic load. When the blade works in a small flow area and the load is relatively large, eddy noise is the dominant component.
Because the rotation noise is dominant in large flow, vortex noise is dominant in small flow, so the minimum noise appears between these two ranges. The intensity of two kinds of noise, rotating noise and eddy current noise, depends on the geometry of the blade and the operating conditions.