What is the mechanism of roots fan noise?
Noise sources of roots fans:
Roots fans contain a variety of noise sources. The main parts of their radiation noise are:
(1) aerodynamic noise radiated from air inlets and outlets;
(2) Mechanical noise radiated by the casing, electric idea, and bearings;
(3) Structure-borne sound of root radiation vibration. Among these local noises, the aerodynamic noise (referred to as aerodynamic noise) radiated from the inlet and outlet parts is the strongest. Others such as mechanical noise and electromagnetic noise are unnecessary under the premise of normal operation of the fan. According to the spectrum analysis of the noise generated by the roots fan, its characteristics are low-frequency broadband. The aerodynamic noise of the fan is mainly composed of two parts: torsional noise and eddy current noise.
The torsional noise is noise caused by the blades scattered evenly on the task wheel attacking the surrounding gas medium, causing the surrounding gas pressure pulsations. When the airflow flows through the blade, it forms a surface layer on the surface of the blade, especially the suction side. The surface layer is easily thickened and many vortices occur. At the trailing edge of the blade, the attachment layer of the suction side and pressure side forms the so-called wake area. In the wake zone, the pressure and velocity of the airflow are much lower than those in the main airflow zone. Therefore, when the task wheel twists the elbow, the airflow in the blade exit area is highly uneven. This uneven airflow periodically affects the surrounding medium, and pressure pulsations occur to form noise. The more uneven the airflow, the greater the noise.
Eddy current noise is also called vortex noise or turbulence noise. It is mainly due to the turbulent surface layer and vortex and vortex detachment when the air flows through the blade. The pulsations that cause pressure on the blades are formed. There are four reasons for this:
One is that after the airflow on the surface of the object forms a turbulent cladding layer, the pressure pulses of the airflow in the cladding layer are used for the blades, the inner and outer surfaces of the volute, and parts of the outer surface.
The second is that when the airflow flows through the object, the vortex will fall and fall because the cladding layer develops to a certain level, leaving the vortex will form a large pulsation;
The third is because the turbulence of the incoming flow causes the pulsation of the effect force of the blade to form noise;
The fourth is the noise caused by the secondary eddy current.
Share address: (From: Roots blower, Roots blower, biogas blower, compact Roots blower,)
Contact Sanniu Roots Fan
Name: Shandong Sanniu Machinery Co., Ltd.
Customer Service: 0531-83826888
Address: North Industrial Park, Xianggongzhuang Town, Zhangqiu City