Causes of air-conditioning noise and treatment methods

Causes of air-conditioning noise and treatment methods Definition of noise:

　　1. The definition of noise: From the perspective of physiology and psychology, it refers to all the sounds that people don't need. From an industrial point of view, the sounds emitted by products are noise.

　　 2. Abnormal noise definition: Abnormal noise is the part of the noise emitted by the product that the user cannot accept.

　　 Classification of abnormal noise

According to the characteristics of abnormal noise, it can be divided into:

1. The sound of refrigerant (refrigerant) flowing;

2. Sheet metal vibration sound;

3. High-frequency whistling sound;

4. Collision sound;

5. Friction sound;

6. Abnormal sound of the motor;

7. Abnormal wind noise and other types.

Causes of abnormal noise and treatment methods:

1. The sound of refrigerant (refrigerant) flowing

　(1) Reason:

　　A, the disturbing sound of itself;

　　B, the sound of gasification;

　　C, jet sound (internal friction)

　　 (2) Analysis:

The disturbance sound of

　　 itself cannot be eliminated, but this is not the main noise. The main noises are: vaporization sound and ejection sound. These two kinds of noise involve such a concept: throttling effect.

　　 (There are two types of throttling: A, orifice throttling: sudden change of flow cross section (expansion valve);

　　 B. Friction throttling: extension resistance (capillary tube);

　　 Throttle effect: The generation of throttling effect will accelerate the flow of refrigerant and reduce pressure to gasify. Here again, the concept of Mach number is involved:

Flow velocity/vibration propagation velocity. When the Mach number is greater than 1, it is supersonic. When the Mach number is approximately equal to 1, resonance will occur. When calculating the Mach number, the vibration propagation velocity is constant in the same medium. Larger can only make the Mach number approach and cannot be greater than 1, so the smaller the flow rate, the smaller the chance of resonance.

　　The ejection sound is caused by the violent ejection of the gas-liquid two-phase refrigerant at the throttle outlet after the refrigerant is reduced in pressure by the throttle due to adiabatic expansion and the sudden increase in the cross section of the pipeline. )

　　 (3) Solution:

　　A, reduce the gas-liquid ratio, the specific method: increase the flow cross section to reduce the flow rate;

　　 B. Wrap the sudden change area of ​​the circulation cross section with resistance glue to delay the vaporization time and eliminate the vibration of the pipeline.

　2. Sheet metal vibration

　 (1) Reason:

　　A, compressor vibration drives sheet metal resonance;

　　 B. Fan vibration drives sheet metal resonance.

　　 (2) Analysis:

　　A. Compressor vibration drives sheet metal resonance due to the compressor itself and pipeline vibration;

　　B. Sheet metal resonance driven by fan vibration is caused by unbalanced fan blade assembly, unbalanced motor shaft, and unreasonable motor bracket setting or assembly;

　　 (3) Common solutions:

　　A. If the reason is for the compressor: you can change the rubber pad of the presser foot to reduce vibration;

　　 B. If the cause of pipeline vibration:

　　 Need to optimize the pipeline

　　 (1), reasonably set up shock absorbers;

　　 (2) Properly lengthen the U-shaped part of the pipeline;

　　 (3) Properly adjust the angle between the plane of the lead end of the pipeline and the U-shaped surface.

　　C. If the assembly of the wind wheel is unbalanced and reassemble, replace the fan blade if it fails. The motor shaft is unbalanced and only the motor can be replaced. The motor bracket setting or assembly is unreasonable and needs to be optimized and reassembled.

　　 3. High frequency whistling sound

　　 (1) Reason: Generally, it is generated on the outside machine, mainly reflected in the noise of the compressor itself.

　　 (2) Analysis: This is different from low-frequency electromagnetic sound, but it is generally not easy to handle outside. The image metaphor of "high-frequency howling" is "similar to the sound of running water". If the "flowing water" is too fast, we can branch and drain the water. Then this "high-frequency whistling sound" is the same. This sound is caused by the unreasonable design of the air duct and the vortex of the wind is too rapid, so the air duct structure must be optimized and improved.

　　 (3) Common solution: Use sound absorption and sound insulation methods to reduce the high-frequency sound of the compressor itself.

　　A. The compressor is wrapped near the front sheet metal. The commonly used material is cotton felt or baffle. Its advantage is that the compressor has ideal heat dissipation and does not affect the maximum operation. The disadvantage is that the noise reduction effect is average;

　　B. For wrapping the entire compressor, the commonly used material is also cotton felt or clapboard. The advantage is that the noise reduction effect is much better than the first method. But the disadvantage is that the heat dissipation of the compressor is not good, which affects the maximum operation, especially in window air conditioners;

C. The sound-absorbing material is pasted on the inner side of the sheet metal around the compressor. Commonly used materials are cotton felt, glass fiber or "PU cotton" ("PE cotton" cannot be used). At present, cabinet compressors in the industry use this method to reduce noise. The advantage is that the noise reduction effect is ideal and the heat dissipation effect of the compressor is good, but the disadvantage is that the first and second methods are not convenient for installation.

4. Crash

　　 (1) Reason:

　　A, the pipeline fittings are not installed properly;

　　B, the top of the motor support is deformed;

　　(2) Analysis;

　　A. During transportation;

　　 B, caused during production.

　　 (3) Common solutions:

　　A. If the pipe fittings are not installed properly, adjust the pipe fittings appropriately;

　　 B. If the top of the motor bracket is deformed, correct the motor bracket;

　　C. If PE cotton is not pasted on the top, stick a piece of suitable PE cotton to prevent it from colliding with the top.

　　 5. Friction

　　 (1) Reason:

　　The simple thing is that the distance between objects is too small, resulting in frictional contact.

　　 (2) Analysis:

　　A, the wind wheel assembly is not in place and friction plastic parts;

　　 B, the wind wheel fixing screw is too long to rub the plastic part;

　　 C, the wind blade and the wind guide ring friction.

　　 (3) Common solution: The general simple solution is reassembly.

　　6. ​​Motor noise

　　 (1) Reason: Motor noise is caused by motor vibration, which can be divided into:

　　A, mechanical noise;

　　 B, electromagnetic noise.

　　 (2) Analysis: Mechanical noise is the noise produced by bearings and vibration; electromagnetic noise is the noise produced by the unbalanced or unbalanced magnetic force of the magnetic circuit and the electromagnetic force wave of the air gap.

　　 (3) Common solutions:

A. If the mechanical noise is caused by the eccentricity of the motor shaft, the motor can only be replaced. If the motor shaft is rusty or insufficient lubrication, you can add lubricating oil or replace the motor. If the assembly is not in place and spread to the shell through a certain medium, the rubber can be replaced. Loop or reassemble;

　　 B. Electromagnetic noise can only replace the motor.

　　 7. Abnormal wind noise

　　 (1) Reason:

　　A. The design reason of the wind wheel itself;

　　 B, the wind wheel and the air duct are not in place;

　　 C. The internal distribution of the indoor cabinet is unreasonable.

　　 (2) Analysis:

　　A. Rotating noise: We can use the formula to calculate the frequency of the rotating noise (fan×rotation speed/60). If the peak frequency obtained by the test is near the frequency of the calculated rotating noise, it can be known that the noise is rotating noise;

　　B. Surge sound: (specifically, the speed is unstable and the wind speed is unstable) The surge sound is due to the design problem of the wind wheel and the air duct. The theoretical expression is that the surge sound is produced when the air volume is lower than the design air volume;

　　C, the sound of boiling water: it is caused by the unreasonable internal distribution of the internal machine; it is mainly manifested on the model with a flat front panel;

　　D, impure wind noise: it is mainly caused by burrs or insufficient fan design pressure)

　　 (3) Common solutions:

　　A. There are two ways to solve the rotation noise:

　　 (1) Modification: change the matching size between the wind wheel, the vortex tongue and the water tray,

　　 (2) Change the wind wheel. Choose a wind wheel with uneven blade distribution or a wind wheel with a smaller diameter;

　　 B. To solve the surging sound, the wind resistance must be optimized, the resistance reduced, and the air volume increased;

　　C. To solve the sound of boiling water, only the structure can be improved;

　　D. The impure wind noise of the internal machine can be solved by removing burrs or changing the wind wheel. The impure wind noise of the external machine can be replaced with a fan of the same model from another manufacturer or a motor with a lower speed to meet the design pressure of the fan.

　　 definition of noise:

　　1. The definition of noise: From the perspective of physiology and psychology, it refers to all the sounds that people don't need. From an industrial point of view, the sounds emitted by products are noise.

　　 2. Abnormal noise definition: Abnormal noise is the part of the noise emitted by the product that the user cannot accept.

　　 Classification of abnormal noise

According to the characteristics of abnormal noise, it can be divided into:

1. The sound of refrigerant (refrigerant) flowing;

2. Sheet metal vibration sound;

3. High-frequency whistling sound;

4. Collision sound;

5. Friction sound;

6. Abnormal sound of the motor;

7. Abnormal wind noise and other types.

Causes of abnormal noise and treatment methods:

1. The sound of refrigerant (refrigerant) flowing

　(1) Reason:

　　A, the disturbing sound of itself;

　　B, the sound of gasification;

　　C, jet sound (internal friction)

　　 (2) Analysis:

The disturbance sound of 　　 itself cannot be eliminated, but this is not the main noise. The main noises are: vaporization sound and ejection sound. These two kinds of noise involve such a concept: throttling effect.

　　 (There are two types of throttling: A, orifice throttling: sudden change of flow cross section (expansion valve);

　　 B. Friction throttling: extension resistance (capillary tube);

　　 Throttle effect: The generation of throttling effect will accelerate the flow of refrigerant and reduce pressure to gasify. Here again, the concept of Mach number is involved:

Flow velocity/vibration propagation velocity. When the Mach number is greater than 1, it is supersonic. When the Mach number is approximately 1, resonance will occur. When calculating the Mach number, the vibration propagation velocity is constant in the same medium. Larger can only make the Mach number approach and cannot be greater than 1, so the smaller the flow rate, the smaller the chance of resonance.

　　The ejection sound is caused by the violent ejection of the gas-liquid two-phase refrigerant at the throttle outlet after the refrigerant is throttled and depressurized due to adiabatic expansion and the sudden increase of the pipe cross section. )

　　 (3) Solution:

　　A, reduce the gas-liquid ratio, the specific method: increase the flow cross section to reduce the flow rate;

　　 B. Wrap the sudden change area of ​​the circulation cross section with resistance glue to delay the vaporization time and eliminate the vibration of the pipeline.

　2. Sheet metal vibration

　 (1) Reason:

　　A, compressor vibration drives sheet metal resonance;

　　 B. Fan vibration drives sheet metal resonance.

　　 (2) Analysis:

　　A. Compressor vibration drives sheet metal resonance due to the compressor itself and pipeline vibration;

　　B. Sheet metal resonance driven by fan vibration is caused by unbalanced fan blade assembly, unbalanced motor shaft, and unreasonable motor bracket setting or assembly;

　　 (3) Common solutions:

　　A. If the reason is for the compressor: you can change the rubber pad of the presser foot to reduce vibration;

　　 B. If the cause of pipeline vibration:

　　 Need to optimize the pipeline

　　 (1), reasonably set up shock absorbers;

　　 (2) Properly lengthen the U-shaped part of the pipeline;

　　 (3) Properly adjust the angle between the plane of the lead end of the pipeline and the U-shaped surface.

　　C. If the wind wheel assembly is unbalanced and reassembled, replace the fan blade if it fails. The motor shaft is unbalanced and only the motor can be replaced. The motor bracket setting or assembly is unreasonable and needs to be optimized and reassembled.

　　 3. High frequency whistling sound

　　 (1) Reason: Generally, it is generated on the outside machine, mainly reflected in the noise of the compressor itself.

　　 (2) Analysis: This is different from low-frequency electromagnetic sound, but it is generally not easy to handle outside. The analogy of the "high-frequency whistling sound" is "similar to the sound of running water". If the "flowing water" is too fast, we can branch and drain it. Then this "high-frequency whistling sound" is the same. This sound is caused by the unreasonable design of the air duct and the vortex of the wind is too rapid, so the air duct structure must be optimized and improved.

　　 (3) Common solution: Use sound absorption and sound insulation methods to reduce the high-frequency sound of the compressor itself.

　　A. The compressor is wrapped near the front sheet metal. The commonly used material is cotton felt or baffle. Its advantage is that the compressor has ideal heat dissipation and does not affect the maximum operation. The disadvantage is that the noise reduction effect is average;

　　 B. For wrapping the entire compressor, the commonly used material is cotton felt or baffle plate. The advantage is that the noise reduction effect is much better than the first method. But the disadvantage is that the heat dissipation of the compressor is not good, which affects the maximum operation, especially in window air conditioners;

C. The sound-absorbing material is pasted on the inner side of the sheet metal around the compressor. Commonly used materials are cotton felt, glass fiber or "PU cotton" ("PE cotton" cannot be used). At present, cabinet compressors in the industry use this method to reduce noise. The advantage is that the noise reduction effect is ideal, and the heat dissipation effect of the compressor is good, but the disadvantage is that the first and second methods are not convenient for installation.

4. Crash

　　 (1) Reason:

　　A, the pipeline fittings are not installed properly;

　　B, the top of the motor support is deformed;

　　(2) Analysis;

　　A. During transportation;

　　 B, caused during production.

　　 (3) Common solutions:

　　A. If the pipe fittings are not installed properly, adjust the pipe fittings appropriately;

　　 B. If the top of the motor bracket is deformed, correct the motor bracket;

　　C. If PE cotton is not pasted on the top, stick a piece of suitable PE cotton to prevent it from colliding with the top.

　　 5. Friction

　　 (1) Reason:

　　The simple thing is that the distance between objects is too small, resulting in frictional contact.

　　 (2) Analysis:

　　A, the wind wheel assembly is not in place and friction plastic parts;

　　 B, the wind wheel fixing screw is too long to rub the plastic part;

　　 C, the wind blade and the wind guide ring friction.

　　 (3) Common solution: The general simple solution is reassembly.

　　6. Motor noise

　　 (1) Reason: Motor noise is caused by motor vibration, which can be divided into:

　　A, mechanical noise;

　　 B, electromagnetic noise.

　　 (2) Analysis: Mechanical noise is the noise produced by bearings and vibration; electromagnetic noise is the noise produced by the unbalanced or unbalanced magnetic force of the magnetic circuit and the electromagnetic force wave of the air gap.

　　 (3) Common solutions:

A. If the mechanical noise is caused by the eccentricity of the motor shaft, the motor can only be replaced. If the motor shaft is rusty or insufficient lubrication, you can add lubricating oil or replace the motor. If the assembly is not in place and spread to the shell through a certain medium, the rubber can be replaced. Loop or reassemble;

　　 B. Electromagnetic noise can only replace the motor.

　　 7. Abnormal wind noise

　　 (1) Reason:

　　A. The design reason of the wind wheel itself;

　　 B, the wind wheel and the air duct are not in place;

　　 C. The internal distribution of the indoor cabinet is unreasonable.

　　 (2) Analysis:

　　A. Rotating noise: We can use the formula to calculate the frequency of the rotating noise (fan×rotation speed/60). If the peak frequency obtained by the test is near the frequency of the calculated rotating noise, it can be known that the noise is rotating noise;

　　B. Surge sound: (specifically, the speed is unstable and the wind speed is unstable) The surge sound is due to the design problem of the wind wheel and the air duct. The theoretical expression is that the surge sound is produced when the air volume is lower than the design air volume;

　　C, the sound of boiling water: it is caused by the unreasonable internal distribution of the internal machine; it is mainly manifested on the model with a flat front panel;

　　D, impure wind noise: it is mainly caused by burrs or insufficient fan design pressure)

　　 (3) Common solutions:

　　A. There are two ways to solve the rotation noise:

　　 (1) Modification: change the matching size between the wind wheel, the vortex tongue and the water tray,

　　 (2) Change the wind wheel. Choose a wind wheel with uneven blade distribution or a wind wheel with a smaller diameter;

　　 B. To solve the surging sound, the wind resistance must be optimized, the resistance reduced, and the air volume increased;

　　C. To solve the sound of boiling water, only the structure can be improved;

　　D. The impure wind noise of the internal machine can be solved by removing burrs or changing the wind wheel. The impure wind noise of the external machine can be replaced with a fan of the same model from another manufacturer or a motor with a lower speed to meet the design pressure of the fan.