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Where does the noise of DC centrifugal fans come from?

Where does the noise of DC centrifugal fans come from?
 
We all know that noise is a kind of sound harmful to our health, and this is a problem that we must deal with. But so far, there is no way to completely eradicate noise. Next, follow the centrifugal fan manufacturer——Ruiapple to understand the related problems of the noise origin of the DC centrifugal fan.
 
How does the noise of the DC centrifugal fan come from? The total noise level of the DC centrifugal fan is proportional to the sixth power of the blade speed. According to analysis, the noise source of centrifugal fan is basically dipole. It can be further concluded that the noise is caused by the effect of the blade on the pulsating force of the air flowing through the fan. It can be considered that there are two discrete frequency noise sources of centrifugal fans, one is the propeller-like noise caused by the pressure field following the movement of the rotor blades; the other is the blade pulse dynamic noise caused by aerodynamics. The spacing between the moving and static blades of a centrifugal fan is an important factor of dryness and noise.
 
When this interval is small, changes in the potential flow and wake will both have an impact, and the blades may also act as sound barriers to strengthen the sound radiation generated by the lift pulses on the blades of the nearby blade row. This effect depends on the ratio of the wavelength of the sound wave related to the lift pulsation to the size of the blade as a barrier. In the frequency range where the ratio is greater than 2, the change in radiation intensity caused by this effect is the most significant. Therefore, when the upstream and downstream of a noise-radiating blade have the same number of blades, and each blade in the two rows of blades meets a rotor blade together to form a sound barrier on both sides of the source, this effect will be stronger. When the interval between the moving and stationary blades increases, the potential flow stem and the influence decrease much faster than the influence of the wake speed change, the effect of the blade as a sound barrier will also decrease with the increase of the interval.
 
It can be seen that at least two factors affect the noise level of dry and DC centrifugal fans:
1. The shape of the blade of the velocity field waveform (that is, the blade load);
2. The spacing between the blade rows and the radiating area of ??the blade as the sound source: a very small distance may have two acoustic effects. If the force pulsation established by the static blade stem and the field on the moving blade makes the moving blade a sound source, The static leaf is a sound barrier.
 
Shenzhen Ruiapple Electronics Co., Ltd. is a professional fan manufacturer (manufacturing plant Mianyang Anpu Electric Co., Ltd. was established in 2009 with China Electronic Technology City Mianyang Economic Development Zone, Sichuan), with 20 years of R&D, production and sales experience. Our research and development, quality control and production always pay close attention to new technologies and new methods to pursue the goal of zero defects, continuously improve product quality and stability, improve products, innovate products, and lean production. Our product quality and production technology have always been at the forefront of the industry, with complete product specifications and comprehensive market competitive advantages.
 
Shenzhen Ruiapple Electronics Co., Ltd. has a strong R&D team, which has been dedicated to product research and development for many years, providing customers with complete heat dissipation solutions, striving for perfection, improving technology, and optimizing performance. It is targeted at consumer goods, office equipment, aerospace industry, automotive electronics, Ventilation system, machinery equipment, communication equipment and other industries conduct special research and provide products for the industry characteristics of the application of heat dissipation and ventilation products.