How to noise the fan
The author:AdminPopularity:414release
time:2017-08-09
The fan is actually a positive displacement compressor, which consists of a pair of interlocking waist-shaped leaf impeller relative high-speed rotation to transport the gas. When the fan unit is working, the noise is mainly the dynamic noise of the air (ie, the air noise), the noise of the transmission gear, the noise of the motor and the noise of the regulating valve are some, and the strength is the highest and the influence is the aerodynamic noise. It contains periodic exhaust noise that occurs when the fan pulsator rotates periodically by the outwardly vented gas, and the eddy current noise caused by gas vortices at the fan impeller interface. The intensity of the exhaust gas is mainly related to the speed of the impeller, the flow rate of the fan exhaust and the static pressure, and the noise spectrum is often low frequency and accompanied by a certain noise peak. The eddy current noise depends on the shape of the fan impeller, air flow relative to the body flow and flow, generally have a continuous spectrum of high-frequency noise.
When working in a certain working condition, the high-intensity noise is radiated from the inlet, the exhaust port, the casing and the pipe of the fan. In the actual application conditions, the fan's exhaust port is often connected with the gas pipeline closed. Therefore, the noise of the intake port is the most intense, the most serious interference to the environment. Measured by the measured, the air blown out of the fan noise, the "A" file noise level of up to 105 ~ 135 dB or so, and "C" file noise level was 110 ~ 140 dB or so.
The fan is not only high in noise intensity, but also has a chaotic and continuous frequency component. In order to quantitatively describe the distribution of its noisy energy over the entire audio range, the octave filter is often used in the noise measurement to perform spectral analysis of the noise at eight octave bands of 63 Hz to 800 Hz to obtain sound The noise spectrum characteristic curve of the source, that is, the frequency curve of the frequency of the octave sound pressure level. The noise spectrum features are:
First, the noise spectrum is wide, that is, in a wide frequency range are high noise, and low-IF noise as the main component, when the static pressure is low, that is, the load is small, the peak frequency is often low frequency 125 Hz At the mercy of 500 Hz will also show a new noise peak. This shows that the fan work pressure, the high frequency noise will be significantly increased.
Fan noise intensity and spectral characteristics in addition to the size of the static pressure with the fan work, but also with the fan flow, speed has a great relationship. As with the increase in traffic, the noise is correspondingly higher, and when the speed doubles, the fan noise can increase 5 ~ 10 dB or so, especially in the high frequency noise is more obvious.
Fan noise management approach:
Fan noise reduction In addition to considering the outlet noise, according to the scene conditions, the fan body noise and oscillation of the solid sound transmission should also be noted.
As the axial fan work to announce a lot of noise, and fan noise also followed by air volume and wind pressure increases and progress. General handling fan noise problems are the following ways:
1) The noise of the case and the motor can be handled by installing the acoustic hood, and the fan is placed in the independent fan insulation, and the sound absorption and sound insulation are carried out in the fan.
2) In the fan exhaust outside the device muffler, built-in silencer insert, so that noise through the special structure of the muffler cut. Muffler is a useful way to reduce the noise emitted by the aerodynamic equipment into or out of the air.
3) the ground side of the blinds as much as possible the use of silencer blinds.
4) fan hanging selection damping anchor hanger shock absorber.