Fan noise control
1、 The source of noise
The generation of fan noise mainly includes two aspects: fan and air duct:
The noise of the fan is mainly caused by the vibration of the fan body, the blades, and the high-speed airflow at the fan outlet, combined with the noise generated by transmission components such as motors
And it's done.
2. The noise of the air duct is mainly caused by the vibration of the air duct:
(1) The outlet flow velocity of the primary and secondary air fans is high, and the air flow field in the duct is unstable, causing duct vibration. The outlet duct of the fan is an eccentric expansion.
(2) The vibration of the fan causes resonance and generates noise through pipeline connections. In the case of uneven flow field, the internal pressure generated by the vortex of the airflow is an irregular pulsating pressure. The force exerted by the pulsating pressure on the wall of the air duct is constantly changing, and this constantly changing force causes vibration of the air duct wall. The vibration of the fan body is transmitted to the air duct through a fixed connection.
(3) The rigidity of the fixed support point is poor, and the overall vibration of the air duct is significant.
2、 Measures taken
In response to the causes of the aforementioned noise, the following measures have been taken during the remediation process:
1. Install a fan soundproof cover on the fan body. The soundproof cover can effectively isolate the noise of the fan casing and the inlet and outlet air ducts, as well as the noise of other transmission mechanisms such as motors.
(1) The entire soundproof enclosure is a closed composite structure composed of a steel frame and soundproof components, which is easy to install and disassemble;
(2) The soundproof cover completely covers the entire fan and drive mechanism inside, and the entire soundproof cover is firmly fixed to the ground by a steel frame. The steel frame of the soundproof cover has no steel connection with the fan body, effectively avoiding the propagation of sound;
(3) The sound insulation element is composed of high-quality sound-absorbing materials, coating materials, and perforated steel plates with the best aperture and perforation rate. A specially designed polymer damping and vibration reduction layer is laid on the inner wall of the steel plate of the sound insulation element, effectively avoiding resonance and coincidence effects;
(4) In order to ensure the safe operation of the motor, a ventilation and noise reduction system is installed on the soundproof enclosure.
2. Treat the inlet and outlet air ducts outside the soundproof enclosure.
(1) Install dual stage metal expansion joints in the air duct to eliminate vibration.
(2) Reinforce the fixed support points of the air duct to reduce the impact of fan body vibration on the air duct;
(3) Install GF type fan muffler at the inlet of the fan, which is a series of impedance acoustic flow type products. Based on the spectral data obtained from actual testing of various types of wind turbines operating in power plants, our factory determines the required amount of noise reduction in which spectral ranges are used as the main basis for designing sound-absorbing sheet structures and fluid channels. At the same time, narrow rectangular channels with large sound-absorbing material finishes are used to enhance the absorption effect.
3、 Noise situation after treatment
1. The soundproof cover adopts advanced sound insulation principles and materials, which can reduce noise by 22-30dB (A);
2. By reinforcing the flue, the noise caused by pipeline vibration is basically eliminated;
3. After installing GF type fan muffler at the inlet of the fan, its maximum noise level will not exceed 85 dB (A).
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