A sound-absorbing structure suitable for air outlets of heating and ventilation systems

Abstract

The present invention discloses a muffler structure suitable for the air outlet of a heating and ventilation system, wherein the muffler structure is formed by enclosing a plurality of muffler units, and the center of the enclosed unit is the air outlet; the muffler unit comprises an outer layer sound absorbing structure and an inner layer sound absorbing structure arranged in the outer layer sound absorbing structure; the outer layer sound absorbing structure comprises a closed shell, a first back cavity is formed in the closed shell, and a micro-perforated plate is formed on the side of the closed shell close to the air outlet; the inner layer sound absorbing structure comprises a plurality of semi-closed shells which are distributed at intervals and open toward the air outlet, a slit is formed between adjacent semi-closed shells, and a plurality of semi-closed shells are located on the side of the micro-perforated plate and are provided with a closed plate for forming a second back cavity. The present invention has a compact structure, and can maintain the original ventilation effect while achieving high-performance muffler.

Description

Technical Field

[0001] The invention relates to the technical field of sound insulation, and in particular to a sound insulation structure suitable for an air outlet of a heating and ventilation system. Background Art

[0002] The air outlets of the HVAC system will be accompanied by noise, which affects the indoor environment. The noise reduction measures taken for the air outlets (such as ventilation silencers) should ensure the effective ventilation section of the original air flow channel as much as possible, and reduce the pressure loss caused by the noise reduction measures to ensure the ventilation effect. Existing ventilation silencer technologies mostly use resistive silencers made of porous sound-absorbing materials, which are installed at the inlet and exhaust outlets or in the air flow channel to reduce the noise at the inlet and exhaust outlets. The sound attenuation in the medium and high frequency bands is relatively high, but the sound attenuation in the low frequency band is obviously insufficient. At the same time, the length of the silencer is relatively large. In recent years, the development of acoustic metamaterials has provided new ideas for noise control, especially low-frequency noise control.

[0003] The patent specification with publication number CN109243419A discloses a ventilation sound insulation structure consisting of a central ventilation hole and multiple labyrinth-shaped walkways around it. By designing sound cavity flow channels of different lengths, sound insulation performance in a wide frequency range is achieved, but the labyrinth walkways in this structure occupy a large space and the ventilation performance is poor. The patent specification with publication number CN112435646A discloses a U-shaped sound insulator consisting of a central ventilation hole and a shell structure with a cavity on the periphery. The side wall of the central ventilation channel is composed of a film equipped with multiple weights. By selecting the eigenfrequency of the film, the propagation of sound waves in the channel is blocked. However, the film material has problems such as easy wear, limited structural strength and difficulty in maintaining stress for a long time. The patent specification with publication number CN110822206A discloses a highly efficient ventilation sound absorption structure, including two split tube resonant cavities arranged side by side and symmetrically, which is suitable for efficient absorption of low-frequency sound, but the sound absorption frequency band is narrow. Summary of the invention

[0004] In view of the deficiencies in the prior art, an object of the present invention is to provide a compact silencer structure suitable for air outlets of HVAC systems, which can achieve high-performance silencer while maintaining the original ventilation effect.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A noise reduction structure suitable for an air outlet of a heating and ventilation system, wherein the noise reduction structure is formed by enclosing a plurality of noise reduction units, and the center of the enclosed unit is the air outlet;

[0007] The muffler unit comprises an outer layer sound absorbing structure and an inner layer sound absorbing structure arranged inside the outer layer sound absorbing structure; the outer layer sound absorbing structure comprises a closed shell, a first back cavity is formed inside the closed shell, and a side of the closed shell close to the vent is a micro-perforated plate;

[0008] The inner layer sound absorbing structure comprises a plurality of semi-enclosed shells which are distributed at intervals and open toward the vents, and slits are formed between adjacent semi-enclosed shells. A plurality of semi-enclosed shells are provided with a closed plate on the side of the micro-perforated plate to form a second back cavity.

[0009] According to the spectrum characteristics of airflow noise, the silencer unit is designed. The structural parameters include the thickness, aperture and perforation rate of the micro-perforated plate, the depth of the first back cavity, the width and length of the slit structure, the depth of the second back cavity, etc. The width and length of the slit structure can be adjusted by changing the spacing and height of the semi-enclosed shell. By adjusting the structural parameters of the silencer unit, the natural frequencies of the above two resonance sound absorption results (micro-perforated plate sound absorption structure and slit sound absorption structure) are close to the frequency of the airflow noise to be controlled.

[0010] When sound waves are incident on the silencer unit, the air columns in the perforated hole neck and the slit of the micro-perforated plate vibrate strongly due to resonance. The air columns rub against the side walls of the hole neck and the slit to consume sound energy, thereby achieving efficient silencer of noise at two frequency points and their nearby frequencies.

[0011] Preferably, the inner layer sound absorbing structure comprises a plurality of rows of semi-enclosed shells spaced apart from each other, the slits are also formed between adjacent semi-enclosed shells in adjacent rows, and the second back cavities corresponding to the rows are in communication with each other.

[0012] Preferably, the top of the semi-enclosed shell is recessed downward to form a groove with an opening facing away from the micro-perforated plate.

[0013] The depth of the groove is similar to or the same as the height of the semi-enclosed shell, so that multiple curled channels can be formed. The sound waves incident from the microporous plate propagate to different grooves with different sound paths, and are reflected by the grooves to form reflected waves. The reflected waves formed by the same groove and propagating in different directions meet in the first back cavity or meet with the incident waves of the corresponding wavelengths. When the difference in the sound path between the two columns of sound waves is 1 / 2 of the wavelength corresponding to the target frequency, the sound energy of the sound waves of the corresponding frequency can be consumed by the eddy current formed by destructive interference. At the same time, the groove depth is designed to be 1 / 4 of the wavelength corresponding to the noise frequency to be controlled, and the sound wave enters the groove through the groove opening. If the sound path difference experienced by the sound wave when it is reflected at the bottom of the groove and returns to the opening is exactly 1 / 2 of the wavelength corresponding to the target frequency, the sound wave of this frequency will produce destructive interference at the groove opening, and the sound energy will be reduced, which can further improve the sound elimination performance of the sound elimination unit and broaden its sound elimination frequency band.

[0014] Preferably, the opening of the semi-enclosed shell can be closed by a bottom plate arranged at the opening position, and one or more through holes are arranged on the bottom plate.

[0015] The semi-enclosed shell is specifically a rectangular parallelepiped or other closed shape structure, and the surface opening near the ventilation port can additionally introduce a plurality of parallel Helmholtz resonance cavities to further improve its sound-absorbing performance.

[0016] Preferably, a partition is provided at the vent to evenly divide the vent, and the partition is composed of silencer units stacked back to back.

[0017] Specifically, partitions can be added according to the actual size of the vents to increase the upper cutoff frequency of the sound-absorbing structure.

[0018] Preferably, the inner sound absorbing structure is equidistant from each inner wall of the closed shell.

[0019] Preferably, the outer sound absorbing structure and the inner sound absorbing structure are both made of aluminum alloy, stainless steel or plastic; such as rigid materials such as steel plates or acrylic plates.

[0020] Beneficial effects of the present invention:

[0021] This noise reduction structure can achieve high-performance noise reduction while hardly reducing the original ventilation effect (ventilation volume and wind speed) of the air outlet. At the same time, the noise reduction structure is compact, and the noise reduction unit integrates a micro-perforated plate resonance sound absorption structure, multiple parallel slit resonance sound absorption structures, multiple curled acoustic channels with different sound paths, multiple parallel Helmholtz resonance cavities, etc., to achieve broadband noise reduction while ensuring low-frequency noise reduction effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of the present invention;

[0023] Figure 2 It is a structural schematic diagram of the muffler unit of the present invention;

[0024] Figure 3 is a cross-sectional view of the muffler unit of the present invention;

[0025] Figure 4 A schematic diagram of a groove built into a semi-enclosed shell;

[0026] Figure 5 A schematic diagram of an inner layer sound absorbing structure including multiple rows of semi-enclosed shells;

[0027] Figure 6 It is a schematic diagram of a two-degree-of-freedom mass-spring system;

[0028] Figure 7 is the noise spectrum at the heating vent;

[0029] Figure 8 It is a schematic diagram of the simulation calculation results of the sound absorption coefficient of the sound-absorbing structure of the present invention; DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] like Figure 1-3 As shown, a silencer structure suitable for the air outlet of a heating and ventilation system is shown. The silencer structure is composed of four silencer units 1 that are surrounded in a U-shape, and the center of the enclosed structure is the air outlet.

[0032] The sound-absorbing unit 1 includes an outer sound-absorbing structure and an inner sound-absorbing structure disposed inside the outer sound-absorbing structure; the outer sound-absorbing structure includes a closed shell 11, a first back cavity 111 is formed inside the closed shell 11, and a micro-perforated plate 112 is provided on one side of the closed shell 11 close to the vent;

[0033] The inner layer sound absorption structure includes a number of semi-enclosed shells 12 that are spaced apart and open toward the vents, a slit 121 is formed between adjacent semi-enclosed shells 12, a number of semi-enclosed shells 12 are provided with a closing plate 122 on the side of the micro-perforated plate 112, and a second back cavity 123 is formed between the closing plate 122 and the number of semi-enclosed shells 12; specifically, the closing plate 122 can extend downward through the side walls of the semi-enclosed shells 12 on both sides and then extend inward to close, and the front and rear sides are closed with the help of the inner wall of the closed shell 11; or an outer frame is provided outside the number of semi-enclosed shells 12 (except the top) to form the second back cavity 123. Among them, the outer layer sound absorption structure and the inner layer sound absorption structure can be made of rigid materials such as steel plates or acrylic plates.

[0034] In some embodiments, Figure 4 As shown, the top of the semi-enclosed shell 12 is recessed downward to form a groove 124 with an opening facing away from the micro-perforated plate 112, so that a plurality of curled channels can be formed, which can further improve the sound-absorbing performance of the sound-absorbing unit 1 and widen its sound-absorbing frequency band. The width d of the groove 124 is greater than 5 mm.

[0035] In some embodiments, the opening of the semi-enclosed shell 12 is closed by a bottom plate (not shown) arranged at the opening position, and one or more through holes are arranged on the bottom plate, so that multiple parallel Helmholtz resonance cavities can be additionally introduced to further improve its sound absorption performance.

[0036] In some embodiments, Figure 5As shown, the inner sound-absorbing structure includes a plurality of rows of semi-enclosed shells 12 that are spaced apart from each other, and slits 121 are formed between adjacent semi-enclosed shells 12 in adjacent rows, so that the second back cavities 123 corresponding to each row are connected. Specifically, the second back cavities 123 are connected by setting an outer frame. Alternatively, an independent outer frame is set outside each row of semi-enclosed shells 12, so that the second back cavities 123 corresponding to each row are independent.

[0037] In some embodiments, partitions can be added according to the actual size of the vents to evenly divide the vents, and the partitions are composed of back-to-back stacked silencer units 1 to increase the upper cutoff frequency of the silencer structure.

[0038] The muffler unit 1 can be equivalent to a classic two-degree-of-freedom mass-spring system, such as Figure 6 As shown, the equivalent stiffness is K 1 and K 2 , the equivalent masses are M 1 and M 2 Assume that K 1 =K 2 =2K 0 , K 0 is the equivalent stiffness of the single-degree-of-freedom mass-spring system, and the natural frequency of the system is f i (i=1, 2) can be expressed as

[0039]

[0040]

[0041] When the incident sound wave frequency is equal to the system natural frequency f i When the pressures are equal, the air columns in the hole neck and between the slits vibrate violently due to resonance. During the vibration, the air columns rub against the side walls of the hole neck and the slits to consume sound energy.

[0042] According to the actual measured noise spectrum at the heating and ventilation vents, such as Figure 7 As shown in the figure, the noise radiated from the air outlet is mainly medium and low frequency noise, and the sound pressure level reaches a peak value near 1kHz. To reduce the noise, the noise reduction structure parameters are designed. Figure 3 As shown, the micro-perforated plate 112 has a thickness t of 0.5 mm and a perforated hole diameter r 2 The width L of the first back cavity 111 is 200 mm, and the depth D 1 The width r of the semi-enclosed shell 12 is 60 mm. 1 is 18 mm, and the height l is 20 mm; the depth D of the second back cavity 123 is 2 The inner sound absorbing structure is equidistant from the inner walls of the closed shell 11, and the spacing s is 10 mm. The height of the muffler unit 1 is 70 mm.

[0043] In order to verify the noise reduction performance of this noise reduction structure, COMSOL Multiphysics 5.5 was used to simulate the noise reduction unit 1. The calculation results are shown in Figure 8 .Depend on Figure 8 It can be seen that the sound-absorbing structure has good sound-absorbing performance in the medium and low frequency range, and has a high sound absorption coefficient near 400 Hz and 1 kHz, and the sound absorption coefficient is greater than 0.95. It can be seen that the sound-absorbing structure can effectively reduce the medium and low frequency noise at the air outlet in a wide frequency range.

[0044] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A noise reduction structure suitable for the air outlet of a HVAC system. Features: The noise reduction structure is formed by a plurality of noise reduction units, and the center of the unit is a vent. The muffler unit comprises an outer layer sound absorbing structure and an inner layer sound absorbing structure arranged inside the outer layer sound absorbing structure; the outer layer sound absorbing structure comprises a closed shell, a first back cavity is formed inside the closed shell, and a side of the closed shell close to the vent is a micro-perforated plate; The inner layer sound absorbing structure comprises a plurality of semi-enclosed shells which are distributed at intervals and open toward the vents, and slits are formed between adjacent semi-enclosed shells. A plurality of semi-enclosed shells are provided with a closed plate on the side of the micro-perforated plate to form a second back cavity.

2. The sound-absorbing structure for the air outlet of a heating and ventilation system according to claim 1, Features: The inner layer sound absorbing structure comprises a plurality of rows of semi-enclosed shells spaced apart from each other, the slits are also formed between adjacent semi-enclosed shells in adjacent rows, and the second back cavities corresponding to the rows are in communication with each other.

3. The sound-absorbing structure for the air outlet of a heating and ventilation system according to claim 1, Features: The inner layer sound absorbing structure comprises a plurality of rows of semi-enclosed shells which are spaced apart from each other, and the second back cavities corresponding to the rows are independent.

4. The sound-absorbing structure for the air outlet of a heating and ventilation system according to claim 1, Features: The top of the semi-enclosed shell is recessed downward to form a groove with an opening facing away from the micro-perforated plate.

5. The sound-absorbing structure for the air outlet of a heating and ventilation system according to claim 1, Features: The opening of the semi-enclosed shell is closed by a bottom plate arranged at the opening position, and the bottom plate is provided with one or more through holes.

6. The sound-absorbing structure for the air outlet of a heating and ventilation system according to claim 1, Features: The vents are provided with partitions for evenly dividing the vents, and the partitions are composed of back-to-back stacked sound-absorbing units.

7. The sound-absorbing structure for the air outlet of a heating and ventilation system according to claim 1, Features: The inner layer sound absorbing structure is spaced equidistant from each inner wall of the closed shell.

8. The sound-absorbing structure for the air outlet of a heating and ventilation system according to claim 1, Features: The outer layer sound absorbing structure and the inner layer sound absorbing structure are both made of aluminum alloy, stainless steel or plastic.

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