Classification and principle of silencer for air conditioner

The muffler is a device that uses the principle of sound absorption, reflection, interference and interference to reduce airflow noise in the system of low ventilation and air conditioning. According to the principle of noise elimination, the difference can be divided into resistance, resistance, resonance and composite type.

Resistance silencer

The dissipative muffler is anechoic by sound absorption of sound absorbing material. The layout is the sound absorption material on the inner wall of pipeline flow firmly, or press definitely essentials in the pipeline or shell structure in mufflers, sound-absorbing materials can probably put the incident thereon from Department of energy going out. The energy of sound can be absorbed because of the porosity and looseness of sound absorbing material. When sound waves enter the pores, pores caused by atmosphere and material produce tiny vibration, due to friction and viscous resistance. A sound energy into heat energy sector and be absorbed going out.

It is good for high frequency and intermediate frequency noise, but it has poor noise performance for low frequency noise.

1. tube muffler tube muffler is one of the most simple muffler, it is only in the pipe wall with a layer of sound absorption material, it is also known as "pipe lining."". The utility model has the advantages of convenient manufacture and little resistance, but is only applicable to smaller air ducts, and the diameter is no more than 400mm wind pipes. The tube type silencer has only definite attenuation function for medium and high frequency sound absorption, which is very bad to low frequency performance.

The 2. type and pattern of tube muffler muffler on the low frequency performance is poor, the high rate of noise, and easy to train, and when the pipeline section area is large, will affect the results of noise elimination of the noise, which is due to the high frequency sound waves (short wavelength) with narrow beam spread in the tube, when the pipe with large area the acoustic absorption material, and pipe wall fight eliminated, so that the high-frequency sound attenuation eliminated, so the large section duct section can be divided into several grids, this is the type and pattern of muffler. The type of silencer is widely used, the layout is simple, the pattern muffler should ensure that the effective section area is not less than the cross section of the air duct, so the volume is larger, the size of each grid should be controlled at 200mm * 200mm or so. The chip spacing of the muffler is as common as in the 100~200mm range. When the chip spacing increases, the noise reduction will fall correspondingly.

Two resonant silencer

Sound absorption materials are usually of low frequency noise absorption capacity is very low, only increase the thickness of the material to improve the sound absorption results are not economic, in order to improve the sound absorption of low frequency noise, usually adopt resonance type silencer. The situation is the use of resonance type silencer pipe hole and the cavity is connected with atmosphere column and cavity hole in the atmosphere constitute the elastic resonance system, when the external noise frequency and natural frequency of the ray resonance system at the same time, the atmosphere column hole in resonance and intense friction with the hole wall friction to consume energy, so as to achieve the purpose of eliminating the.

This kind of muffler has a strong frequency selectivity, that is, the effective frequency range is very narrow, so it is possible to produce larger attenuation when it is used to deal with low frequency noise elimination. The air flow resistance is small, but the resonance cavity causes the layout to be too big.

Three. Resistance Muffler

The resistance muffler is connected by a tube and a small chamber, and the silencer makes the acoustic wave shift back to the sound source by utilizing the sudden change of the cross section of the air duct and plays the role of silencing.

The silencer has better sound attenuation effect for medium and low noise, and has a simple layout, and is not affected by high temperature and corrosive gas because of bad luck using sound-absorbing material. Eliminate low frequency noise with positive results. - marine air conditioning

In order to ensure the sound attenuation, the expansion ratio of the muffler (the ratio of big to small) should be greater than 4. Therefore, in the construction room of the computer room, the application is limited in the smaller place.

Four, composite muffler

The compound muffler meets the advantages of the resistance and expansion muffler, and has good noise elimination results in the low frequency to high frequency area. The layout is shown in figure 14.5. If the composite muffler is 1.2m long and the low frequency noise level of 10~20dB, the use of air conditioning system can not deal with other fiber acoustic materials (such as cleaning air conditioning engineering), metal (aluminum) layout of micro perforated panel can get good results.

Five. Other examples of mufflers

In addition to the examples of mufflers discussed above, in actual engineering, proper handling of some duct components can also serve as a means of eliminating noise. In addition, they have the benefits of saving space for building.

The commonly used silencer components are: 1. noise elimination elbow, when the engine room area is narrow or needs to improve the noise elimination result to the original construction, may accept the noise elimination elbow. There are two kinds of muffler elbow. The ordinary noise reducing elbow is made of sound absorbing material affixed to the inside. The elbow is usually made of inner arc edge paste sound-absorbing materials, sound-absorbing material length should not be less than 4 times the width of the elbow. Another kind of noise reduction elbow is called resonance type noise reduction elbow, and its outer edge accepts perforated plate, sound absorption material and cavity. The resonance sound absorption layout is used to improve the noise reduction effect of ordinary noise reduction elbow on low frequency noise.

A static pressure box with a sound absorbing material is arranged in front of the fan outlet or the air distributor, and the air pressure can be stabilized and the noise can be eliminated, the 2. silencing static pressure box is arranged in front of the fan outlet or the air distributor. The noise of the silencing static pressure box is related to the performance of sound absorbing material, the area of the sound absorption material in the box, and the area of the cross wind pipe of the exit. The silencing static pressure box can also be used as a wind separating static pressure box.

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