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Cooling fan manufacturers tell you the source and solution of noise

Time：2022-03-11Views：0

The cooling fan manufacturer Chengda tells you about the solution to the noise of the DC blower. We know that many electronic products will generate noise, especially equipment used in industry, many will have it. Noise is a kind of sound that is harmful to our health, and this is a problem that we must solve. But so far, there is no way to completely eliminate noise. Let us first understand the related issues:

How does the noise of the DC blower come from? The editor will answer it for you: the total noise level of the fan is proportional to the sixth power of the blade speed. According to the analysis, the noise source of the fan is basically of dipole nature. It can be further deduced that the noise is caused by the pulsating force of the blades acting on the air flowing through the fan. It can be considered that there are two discrete frequency noise sources of the fan, one is the propeller-type noise caused by the pressure field with the rotor blade movement, and the other is the blade pulsation noise caused by aerodynamic interference. The distance between the moving and stationary blades of the fan is an important factor in the interference noise.

When this distance is small, both potential flow and wake changes have an effect, and it is also possible for the blades to act as a sound barrier, enhancing the acoustic radiation generated by lift pulsations on blades adjacent to the blade row. This effect depends on the ratio of the wavelength of the sound wave associated with the lift pulsation to the size of the blade acting as a barrier. In the frequency range where the ratio is greater than 2, the change in radiation intensity due to this effect is most pronounced. Therefore, the effect will be stronger when there is the same number of blades upstream and downstream of a noise radiating blade, and each blade in the two rows of blades meets a rotor blade at the same time to form a sound barrier on both sides of the source.

When the distance between the moving and stationary blades increases, the effect of the potential flow interference decreases much faster than the effect of the wake velocity change, and the effect of the blades as a sound barrier also decreases with the increase of the distance. It can be seen that at least three parameters affect the magnitude of the interference noise: the blade shape of the velocity field waveform (that is, the blade load), the distance between the blade rows, and the blade radiation area as a sound source. Very small spacing can have two acoustic effects. If the force pulsation created by the interference field of the vane on the moving vane makes the moving vane a sound source, and the vane is a sound barrier.

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Cooling fan manufacturers tell you the source and solution of noise