Fan muffler

Fan silencers have the same form as exhaust pipe silencers and drum induced draft fan silencers, both of which use the principle of resistive sound absorption and noise reduction, which has good effects on medium and high frequency broadband characteristics, and the principle of resistive sound reduction, which has good effects on low, medium frequency, and pulsation characteristics, as well as micro perforated silencers and impedance composite silencers.

Resistive muffler is a type of absorption muffler produced, which is generally divided into straight pipe type, sheet type, folded plate type, honeycomb type, acoustic flow type, labyrinth type, and elbow type according to the structure of the airflow channel. A resistive muffler utilizes the frictional and viscous resistance of sound waves propagating through porous sound-absorbing materials to convert sound energy into heat energy and dissipate it, thereby achieving the purpose of noise reduction. It is the most widely used type of muffler among all mufflers.

The principle of noise reduction for a resistant muffler is different from that of a resistive muffler. It cannot directly absorb sound energy, but instead uses a sudden interface or adjacent resonant cavity on the pipeline to reflect or interfere with certain frequency sound waves propagating along the pipeline at the sudden interface, thereby achieving the purpose of noise reduction. Divided into expansion chamber type muffler and resonance type muffler.

In practical noise control engineering, noise is mostly in the wideband. Therefore, resistive sound absorption and noise reduction structures are usually combined to control high-intensity wideband noise.

Fan silencers are divided into centrifugal fan silencers, Roots fan silencers, blower silencers, and axial flow fan silencers. Fan silencers are mainly used to reduce aerodynamic noise from various fan outlets, ducts, and enclosed machine room air intakes.

According to the different inlet and outlet structures of the fan, it can be divided into circular and rectangular structures.

(1) The circular structure is divided into two types: A and B. The A type has flange plates at both ends and is directly connected to the pipeline (i.e. pipeline muffler), while the B type has a flange at one end and a direct atmospheric exhaust at the other end (can be equipped with a rainproof hood). It is only suitable for installation at the end of outdoor pipelines and at the inlet of enclosed computer rooms.

(2) The thickness of the resistive muffler in a circular structure is generally 100mm and 150mm, with a noise reduction of 15-30dB. Under the condition of wind speed of 5-12m/s, the applicable air volume is 1000-50000m3/h. In its structure, impedance is used to eliminate high-frequency noise and low-frequency noise, in order to maximize the width of the noise reduction frequency band.