发布时间：2022-07-28 14:40:15 人气：75 点赞：0
What are the sources of industrial fan noise
Generally, the noise of industrial fans is between 60-90 DB! And the national "urban regional noise standard" stipulates that the noise in industrial areas greater than 55 dB is regarded as noise nuisance! Therefore, many factories should consider how to reduce the noise of industrial fans when purchasing or installing industrial fans! Today, let's analyze the sources of industrial fan noise! According to our experience in manufacturing fans, aerodynamic noise is the strongest among industrial fans, followed by mechanical noise and electromagnetic noise. Aerodynamic noise includes rotating noise, eddy current noise and resonance noise. The analysis shows that the noise peak of axial flow fan exists in the low-frequency stage, while the medium and high-frequency stage decreases with the increase of frequency. When the noise absorbed by the atmosphere is lower than 100Hz, the natural attenuation of low-frequency noise is very slow. In addition, the longer the low-frequency noise band, the stronger the diffraction ability of obstacles, the farther the wind sound propagation distance, and the larger the pollution range.
Rotating noise: also known as blade noise, it is because the blade rotation periodically hits the air quality point, resulting in air pressure pulsation. Its pressure size is related to the speed and the number of blades. The relative motion between rotating blades and stationary supports will also cause air pulsation and noise. If the number of blades is the same as the number of supports, synchronous disturbance may occur, resulting in superposition of pressure fluctuations and increased noise. In order to avoid this phenomenon, the method of unequal number of supports and blades or unequal pitch can be adopted.
The distance between the blade and the fixed support also directly affects the sound power of the rotating noise, and the distance between the blade top and the air duct shell. For a single chip, it changes periodically; For multiple pieces, the spacing cannot be completely consistent. Therefore, in this gap, the air flow pulsation is periodic and irregular, so the noise level is closely related to the manufacturing quality of the tower and the installation accuracy of blades.
Vortex noise: also known as turbulent noise, is due to the boundary separation of the surrounding air flow when the blade rotates. Vortices are most likely to form on the back of the blades, producing a whistling sound of air flow. In order to reduce noise, blades need appropriate width and streamlined shape. The frequency of vortex noise depends on the relative velocity between the blade and the air flow. When the impeller rotates, the turnover speed around the blade changes with the wheelbase, and the relative speed of the air flow from the blade root to the blade top also changes constantly, so the eddy current noise obviously has the characteristics of continuous spectrum.
Resonance noise: noise caused by rotating noise and eddy current noise. In the design, it should be noted that the inner joint between the air duct and the industrial fan shell should be flat to avoid tearing sound caused by uneven roughness. Sometimes, the air duct is covered with damping materials.
Manufacturers analyze how to quickly reduce the noise of industrial fans
How to reduce the noise of industrial fans?
Resistive silencing device.
The resistive silencing device adopts sound-absorbing materials for silencing, and the sound-absorbing materials are installed in the air duct according to a certain law to form a resistive silencing device, which can effectively achieve the purpose of noise reduction of industrial fans. It is applicable to the elimination of medium and high frequency noise, and is mostly used to eliminate the noise with small gas flow such as ordinary fan equipment and gas turbine. For example, the industrial roots blower will be equipped with a silencer as standard when it leaves the factory!
Anti silencing device.
The resistant silencing device realizes silencing by controlling the acoustic reactance, that is, connecting the pipe section with sudden change in the cross-sectional area of the air duct or connecting the resonant cavity by the side, changing the acoustic impedance, so that the sound waves of some frequencies can reflect, interfere, and counteract the sudden change in the cross-sectional area of the acoustic impedance, so as to achieve the purpose of noise reduction of industrial fans. It is suitable for eliminating the medium and low frequency noise generated under high airflow conditions such as air compressors, internal combustion engines, automobile exhaust, etc.
Impedance compound silencing device.
The impedance composite silencing device can be simply considered as the combination of the first two silencers. Because the resistance and resistance silencing devices have different noise silencing frequency bands, high, medium and low-frequency noises can be eliminated after a certain structural compound. It is suitable for noise elimination in blower, gale tunnel, test bench and other fields, and can better reduce the noise of industrial fans. In Roots blower, the commonly used is sound proof room!
The above is the source and reduction method of industrial fan noise analyzed by Shanghai Ruizhe environmental protection, an industrial Roots fan manufacturer! I hope I can help you solve your noise problems!