A bellows noise reduction device for fresh air cabinet and its use method

Abstract

The present invention discloses a bellows noise reduction device for a fresh air cabinet and a method for using the same. In the device, along the direction of airflow, a first sound-absorbing material, a second sound-absorbing material and an air outlet filter are sequentially provided in the bellows shell. A first inner tube is provided in the middle of the first sound-absorbing material, and a second inner tube is provided in the middle of the second sound-absorbing material. The first inner tube and the second inner tube are in a connected inclined structure and are distributed with a number of sound-absorbing through holes. A pressure diffusion and speed reduction zone is left between the second sound-absorbing material and the air outlet filter. The method for using the bellows noise reduction device is to place the bellows noise reduction device on the upper part of the fresh air cabinet. After the air enters the fresh air cabinet from the return air box, it first passes through a full heat exchange core for temperature adjustment, and then is sent into the bellows noise reduction device by the fan. Noise is reduced by the inclined impedance composite noise reduction structure and the reflection silencer principle, and the fresh air finally formed is sent out from the air outlet. The present invention can take into account both low-frequency and high-frequency noise reduction, and better achieve a balance between large air volume and low noise.

Description

Technical Field

[0001] The present invention relates to the technical field of fresh air cabinet manufacturing, and in particular to a bellows noise reduction device for a fresh air cabinet and a method of using the device. Background Art

[0002] As the guardian of indoor air quality, fresh air cabinet units are receiving more and more attention, especially in the context of people paying more and more attention to air quality and respiratory health. The basic requirements of people when choosing and using fresh air cabinet units are large air volume and low noise. Especially for public places such as schools and hospitals, the requirements for air volume and noise are extremely strict. However, for fresh air cabinet units, large air volume often means high speed, and high speed will bring high noise, so there is a contradiction between large air volume and low noise. At present, the space that fresh air cabinet units can provide for noise reduction is very limited. In this case, a reasonable and efficient noise reduction structure design is very important.

[0003] In existing fresh air cabinets, noise reduction is generally achieved by stacking sound-absorbing cotton, but the design of the noise reduction space is not reasonable. In actual use, the following obvious defects still exist: (1) While the noise is reduced, the air flow loss is large, making it difficult to achieve an effective balance between noise reduction and air volume; (2) Existing products only achieve noise reduction by stacking sound-absorbing cotton, and their space utilization is unreasonable, the noise reduction amount is small, and the noise reduction effect is poor, making it difficult to meet people's demand for silent cabinet products; (3) The noise reduction structure is complex and the equipment manufacturing cost is high, making it difficult to improve its market competitiveness. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a bellows noise reduction device for fresh air cabinet, which can take into account both low-frequency and high-frequency noise reduction, and greatly improve the bellows noise reduction effect while ensuring that the air volume loss is small, thereby achieving a better balance between large air volume and low noise.

[0005] Another object of the present invention is to provide a method for using the bellows noise reduction device for the above-mentioned fresh air cabinet.

[0006] The technical solution of the present invention is: a bellows noise reduction device for a fresh air cabinet, comprising a bellows shell, a first sound-absorbing material, a first inner tube, a second sound-absorbing material, a second inner tube and an air outlet filter; along the airflow direction, the first sound-absorbing material, the second sound-absorbing material and the air outlet filter are sequentially arranged in the bellows shell, a first inner tube is arranged in the middle of the first sound-absorbing material, and a second inner tube is arranged in the middle of the second sound-absorbing material, the first inner tube and the second inner tube are in a connected inclined structure, and a plurality of sound-absorbing through holes are respectively distributed on the first inner tube and the second inner tube; a pressure diffusion and speed reduction zone is left between the second sound-absorbing material and the air outlet filter, one end of the first inner tube serves as an air inlet, and an air outlet is provided on the bellows shell located outside the air outlet filter. The inclined first and second inner tubes, along with the first and second sound-absorbing materials surrounding them, form an integrated, tilted impedance composite noise reduction structure, which reduces both low- and high-frequency noise, enhancing the noise reduction effect. Furthermore, the tilted structure offsets the inlet and outlet axes of the internal air duct, increasing the wind path while preventing sound waves from passing through the noise reduction cavity in a narrow beam, thereby increasing the sound attenuation. Furthermore, the combination of the sound-absorbing through-holes and the outer sound-absorbing materials creates a sound-absorbing structure that eliminates the frequencies of sound passing through while significantly reducing air volume loss. The expansion and deceleration zone reduces wind speed, reduces impact noise on the filter, and increases the airflow area of ​​the outlet filter (reducing flow resistance). Furthermore, the principle of reflective sound attenuation is employed, leveraging the flow resistance characteristics of the outlet filter and the reflection of sound waves caused by the non-outlet portion of the bellows housing to form a highly efficient reflective sound absorption system with the sound-absorbing materials, enhancing the sound attenuation.

[0007] The first and second inner tubes are interconnected circular or square tubes; along the airflow direction, the axial cross-section of the first and second inner tubes is inclined, straight, or flared. The first and second inner tubes can be integrated or connected, with the angles being adjustable and selectable based on the actual needs of the fresh air cabinet and the specific placement of the air inlet and outlet.

[0008] The first sound-absorbing material and the first inner tube form a primary noise reduction structure; a cavity structure is left between the outer side of the first sound-absorbing material and the inner wall of the bellows shell, and the cavity structure between the primary noise reduction structure and the outer wall of the bellows forms a first noise reduction cavity.

[0009] The first inner insert tube includes a first connecting section, a second connecting section and a third connecting section connected in sequence along the airflow direction, wherein the outer circumference of the third connecting section is wrapped with a first sound-absorbing material, the second connecting section and the third connecting section extend out of the first sound-absorbing material, and sound-absorbing through holes are respectively distributed on the tube walls of the second connecting section and the third connecting section, and the tube wall of the first connecting section is a smooth closed tube wall or an open tube wall with sound-absorbing through holes.

[0010] The second sound-absorbing material and the second inner tube form a secondary noise reduction structure;

[0011] A cavity structure is also left between the outer side of the second sound-absorbing material and the inner wall of the bellows shell, and the air structure between the secondary noise reduction structure and the outer wall of the bellows forms a second noise reduction cavity;

[0012] Alternatively, the outer side of the second sound absorbing material is in contact with the inner wall of the bellows shell.

[0013] When a cavity structure is also left between the outer side of the second sound-absorbing material and the inner wall of the bellows shell, the second inner insert tube includes a fourth connecting section, a fifth connecting section, and a sixth connecting section arranged in sequence along the airflow direction, wherein the outer circumference of the fourth connecting section is wrapped with the second sound-absorbing material, the fifth connecting section and the sixth connecting section extend outside the second sound-absorbing material, sound-absorbing through holes are respectively distributed on the tube walls of the fourth connecting section and the fifth connecting section, and the tube wall of the sixth connecting section is a smooth closed tube wall or an open tube wall distributed with sound-absorbing through holes;

[0014] When the outer side of the second sound absorbing material is in contact with the inner wall of the bellows shell, the outer periphery of the entire second inner tube is wrapped with the second sound absorbing material, and sound absorbing through holes are distributed on the tube wall of the entire second inner tube.

[0015] As a preferred solution, the aperture of the sound-absorbing through-hole is 2-6 mm, and the perforation rate of the sound-absorbing through-hole is 20-40%. That is, on the connecting sections where the sound-absorbing through-holes are distributed (including the connecting sections of the first inner insert tube and the connecting sections of the second inner insert tube), the distribution rate of the sound-absorbing through-holes in the corresponding connecting sections is 20-40%.

[0016] The first sound absorbing material and the second sound absorbing material are respectively made of a density of 30-40 kg / m 3 Polyester fiber sound-absorbing material.

[0017] The air outlet is located in the middle of the top surface of the bellows housing, and the area of ​​the air outlet occupies 1 / 8 to 1 / 2 of the area of ​​the top surface of the bellows housing. To ensure the sound attenuation effect and the air volume output, the area ratio between the air outlet and the top surface of the bellows housing on which it is located should not be too large or too small. If it is too large, it is difficult to achieve the ideal sound attenuation effect, while if it is too small, it is difficult to ensure that the air volume reaches the target value. Therefore, after testing, the area of ​​the air outlet occupies 1 / 8 to 1 / 2 of the area of ​​the top surface of the bellows housing as a more optimal numerical range.

[0018] The present invention provides a method for using the bellows noise reduction device for the fresh air cabinet, specifically comprising: the bellows noise reduction device is arranged on the upper part of the fresh air cabinet, the air inlet is connected to the fan outlet in the fresh air cabinet, and the air outlet serves as the fresh air outlet of the entire fresh air cabinet;

[0019] Inside the fresh air cabinet, under the action of the fan, after the air enters the fresh air cabinet from the return air box, it first passes through the full heat exchange core for temperature adjustment, and then is sent into the bellows noise reduction device by the fan; in the bellows noise reduction device, noise reduction is first performed through the inclined impedance composite noise reduction structure, and then the principle of reflection silencer is used to further improve the noise reduction effect, and finally the formed fresh air is sent out from the air outlet.

[0020] When the bellows noise reduction device for the above-mentioned fresh air cabinet is used, its noise reduction principle is:

[0021] First, the inclined arrangement of the first and second inner tubes and the surrounding first and second sound-absorbing materials form a primary and secondary noise reduction structure, so that the internal cavity of the bellows shell on the periphery forms an impedance composite noise reduction cavity. The first and second inner tubes are arranged in an inclined manner, so that the inlet and outlet axes of the air duct formed by their connection are staggered. This not only increases the airflow path, but also prevents sound waves from passing through the noise reduction cavity in the form of a narrow sound beam, thereby improving the sound attenuation.

[0022] Second, sound-absorbing holes are provided on the walls of the middle sections of the first and second inner tubes (i.e., the second and fifth connecting sections). This can reduce the loss of airflow resistance while maintaining the change in acoustic impedance caused by the sudden change in the radial cross-section of the air duct. Furthermore, between the connecting sections at both ends of the first inner tube and between the connecting sections at both ends of the second inner tube (i.e., between the first and third connecting sections, and between the fourth and sixth connecting sections), the phases of the sound waves encountering different cross-sections of the air duct are 180° different from the phases of the reflected sound waves. This results in opposite phases between the connecting sections, causing interference between the two ends, thereby eliminating their passing frequencies.

[0023] Third, by providing a cavity structure between the outer surface of the sound-absorbing material (including the first sound-absorbing material or the first sound-absorbing material and the second sound-absorbing material) and the inner wall of the bellows housing, the sound-absorbing effect of the sound-absorbing material at low frequencies can be further enhanced;

[0024] Fourth, after the air passes through the above-mentioned inner insert and sound-absorbing material to reduce noise, it enters the pressure expansion and velocity reduction zone formed between the air outlet filter and the second sound-absorbing material. After the pressure expansion and velocity reduction in this zone, when the airflow reaches the air outlet filter, its flow rate is reduced, the impact on the air outlet filter is weakened, the regeneration noise is reduced, and the wind flow area of ​​the air outlet filter is increased, thereby improving the utilization rate and service life of the air outlet filter. At the same time, when the airflow passes through the air outlet filter, due to the resistance of the filter itself, the sound waves will be reflected. The reflected sound waves enter the second sound-absorbing material or the second sound-absorbing material and the second noise reduction cavity around it, and their energy is consumed and converted into heat energy, thereby achieving a further effect of sound attenuation and noise reduction;

[0025] Fifth, after passing through the air outlet filter, the air enters the space between the air outlet filter and the inner wall of the bellows housing on its outside. Since the area of ​​the air outlet is smaller than the area of ​​the top surface of the bellows housing in which it is located, when the sound waves reach the top surface of the bellows housing, except for a part of the sound waves that directly enter the atmospheric environment from the air outlet, the rest of the sound waves will be reflected. In this process, some of the sound waves are reflected multiple times and interfere with each other to cancel each other out, while the other part of the sound waves pass through the filter and re-enter the second sound-absorbing material or the second sound-absorbing material and the second noise reduction cavity around it to be absorbed and consumed;

[0026] Through the synergistic effect of the noise reduction principles mentioned above, a good noise reduction effect can be achieved, and a larger air volume output can be better guaranteed, thereby achieving a balance between large air volume and low noise.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] In the bellows noise reduction device for the fresh air cabinet and its use method, the synergistic effect of the inclined impedance composite noise reduction structure and the reflection silencer principle is utilized to achieve substantial noise reduction of the fresh air cabinet under the condition of low flow loss, especially taking into account the noise reduction requirements of the low, medium and high frequency bands. While ensuring that the air volume loss is small, the bellows noise reduction effect is greatly improved, and a better balance between large air volume and low noise is achieved. In addition, the device has a compact structure and low production cost, can bring consumers a more comfortable sound quality experience, and has good market promotion prospects.

[0029] When the bellows noise reduction device for the fresh air cabinet is applied to the fresh air cabinet, it is easy to install and flexible to use; in addition, the first-level noise reduction structure composed of the first sound-absorbing material and the first inner tube, and the second-level noise reduction structure composed of the second sound-absorbing material and the second inner tube can be diversified and can be selected for use according to the actual needs of the fresh air cabinet. Its structure is flexible and changeable and can adapt to the use of a variety of different fresh air cabinets.

[0030] In the bellows noise reduction device used for the fresh air cabinet, the length, diameter or width, specific shape, tilt angle and other data of the inclined first inner tube and the second inner tube can be selected or adjusted according to the actual needs of the fresh air cabinet. It is flexible to use and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a structural diagram of Example 1 of the bellows noise reduction device.

[0032] Figure 2 for Figure 1 Schematic diagram of the structure in which the first inner insert tube and the second inner insert tube are connected.

[0033] Figure 3 for Figure 1 The diagram shows the structure of the bellows noise reduction device when it is applied to the fresh air cabinet.

[0034] Figure 4 This is a structural diagram of Example 2 of the bellows noise reduction device.

[0035] Figure 5 for Figure 4 Schematic diagram of the structure in which the first inner insert tube and the second inner insert tube are connected.

[0036] Figure 6 for Figure 4 The diagram shows the structure of the bellows noise reduction device when it is applied to the fresh air cabinet unit.

[0037] In the above figures, the components indicated by the reference numerals are as follows:

[0038] 1 is the bellows shell, 2 is the first sound-absorbing material, 3 is the first inner tube, 3-1 is the first connecting section, 3-2 is the second connecting section, 3-3 is the third connecting section, 4 is the second sound-absorbing material, 5 is the second inner tube, 5-1 is the fourth connecting section, 5-2 is the fifth connecting section, 5-3 is the sixth connecting section, 6 is the air outlet filter, 7 is the sound-absorbing through hole, 8 is the pressure expansion and speed reduction area, 9 is the air inlet, 10 is the air outlet, 11 is the first noise reduction cavity, and 12 is the second noise reduction cavity.

[0039] 13 is the upper air box, 14 is the fan, 15 is the full heat exchange core, 16 is the primary filter, and 17 is the return air box. DETAILED DESCRIPTION

[0040] The present invention will be further described in detail below with reference to the examples, but the embodiments of the present invention are not limited thereto.

[0041] Example 1

[0042] This embodiment provides a bellows noise reduction device, such as Figure 1As shown, it includes a bellows shell 1, a first sound-absorbing material 2, a first inner tube 3, a second sound-absorbing material 4, a second inner tube 5 and an air outlet filter 6; along the airflow direction, the first sound-absorbing material, the second sound-absorbing material and the air outlet filter are sequentially arranged in the bellows shell, the first inner tube is provided in the middle of the first sound-absorbing material, the second inner tube is provided in the middle of the second sound-absorbing material, the first inner tube and the second inner tube are connected in an inclined structure, and a plurality of sound-absorbing through holes 7 are distributed on the first inner tube and the second inner tube respectively; a pressure diffusion and speed reduction zone 8 is left between the second sound-absorbing material and the air outlet filter, one end of the first inner tube is used as an air inlet 9, and an air outlet 10 is provided on the bellows shell located outside the air outlet filter. Among them, an integral inclined impedance composite noise reduction structure is formed between the inclined first inner tube, the second inner tube and the first sound-absorbing material and the second sound-absorbing material on the periphery thereof, which can take into account the noise reduction effects of both low and high frequencies and improve the noise reduction effect; in addition, the inclined structure staggers the inlet and outlet axes of the internal air duct, which increases the wind path while preventing sound waves from passing through the noise reduction cavity in the form of a narrow sound beam, thereby increasing the sound attenuation; in addition, the combination of the sound-absorbing through-hole and the sound-absorbing material on its outer side forms a good sound-absorbing structure, which can eliminate the sound frequencies passing through while significantly reducing the loss of air volume. The setting of the pressure-expanding and speed-reducing zone utilizes the principle of reflective sound absorption, and with the help of the flow resistance characteristics of the air outlet filter and the reflection of sound waves caused by the non-air outlet part of the bellows shell, forms a high-efficiency reflective sound absorption system with the sound-absorbing material to improve the sound attenuation. In this embodiment, if Figure 2 As shown, the first inner tube and the second inner tube are connected square tubes, and along the airflow direction, the axial section of the first inner tube and the second inner tube connected is an inclined straight tube. According to the actual needs of the fresh air fan, the first inner tube and the second inner tube can adopt a connected one-piece structure or a connected split splicing structure, and the specific inclination angles of the first inner tube and the second inner tube can also be adjusted and selected according to the actual needs of the fresh air cabinet used and the specific position settings of the air inlet and the air outlet.

[0043] like Figure 1 As shown, the first sound-absorbing material and the first inner tube form a primary noise reduction structure; a cavity structure is left between the outer side of the first sound-absorbing material and the inner wall of the bellows shell, and the cavity structure between the primary noise reduction structure and the outer wall of the bellows forms a first noise reduction cavity 11; the second sound-absorbing material and the second inner tube form a secondary noise reduction structure, but the outer side of the second sound-absorbing material is connected to the inner wall of the bellows shell, leaving no cavity structure. Figure 2As shown, the first inner tube includes a first connecting section 3-1, a second connecting section 3-2 and a third connecting section 3-3 connected in sequence along the airflow direction, wherein the outer periphery of the third connecting section is wrapped with a first sound-absorbing material, the second connecting section and the third connecting section extend out of the first sound-absorbing material, and sound-absorbing through holes are respectively distributed on the tube walls of the second connecting section and the third connecting section, and the tube wall of the first connecting section is a smooth closed tube wall; the outer periphery of the entire second inner tube is wrapped with a second sound-absorbing material, and sound-absorbing through holes are distributed on the tube wall of the entire second inner tube.

[0044] The noise reduction principle of the above-mentioned bellows noise reduction device is: first, the inclined first inner tube, the second inner tube and the first sound-absorbing material and the second sound-absorbing material on their periphery are used to form a primary noise reduction structure and a secondary noise reduction structure, so that the internal cavity of the bellows shell on its periphery forms an impedance composite noise reduction cavity. Since the first inner tube and the second inner tube adopt an inclined structural form, the inlet and outlet axes of the air duct formed by their connection are staggered, which not only increases the wind path, but also prevents the sound waves from passing through the noise reduction cavity in the form of a narrow sound beam, thereby improving the sound attenuation; second, in the first inner tube Sound-absorbing holes are provided on the wall of the middle section of the intubation tube and the second inner intubation tube, which can reduce the loss of airflow resistance while maintaining the change of acoustic impedance caused by the sudden change of the radial cross-section of the air duct. The two connecting sections at the ends of the first inner intubation tube (i.e., between the first connecting section and the third connecting section) can respectively make the sound waves encounter different cross-sections of the air duct and the reflected sound waves have a phase difference of 180 degrees, so that the phases between the two connecting sections are opposite and interfere with each other, thereby eliminating their passing frequency. Thirdly, by providing a cavity structure between the outer surface of the first sound-absorbing material and the inner wall of the bellows shell, further Enhance the sound absorption effect of the sound-absorbing material at low frequencies; Fourth, after the air passes through the above-mentioned inner insert tube and the sound-absorbing material for noise reduction, it enters the pressure expansion and speed reduction zone formed between the air outlet filter and the second sound-absorbing material. After the pressure expansion and speed reduction in this area, when the airflow reaches the air outlet filter, its flow rate is reduced, the impact on the air outlet filter is weakened, the regeneration noise is reduced, and the wind flow area of ​​the air outlet filter is increased, thereby improving the utilization rate and service life of the air outlet filter. At the same time, when the airflow passes through the air outlet filter, due to the resistance of the filter itself, the sound waves will be reflected, and the reflected sound waves enter the second sound-absorbing material. In the sound-absorbing material, its energy is consumed and converted into heat energy, thereby achieving the effect of further attenuating and reducing noise. Fifth, after passing through the air outlet filter, the air enters the space between the air outlet filter and the inner wall of the bellows shell on its outer side. Since the area of ​​the air outlet is smaller than the area of ​​the top surface of the bellows shell in which it is located, when the sound waves reach the top surface of the bellows shell, except for some sound waves that directly enter the atmosphere from the air outlet, the rest of the sound waves will be reflected. In this process, some sound waves are reflected multiple times, interfering with each other and canceling each other out, while other sound waves pass through the filter and re-enter the second sound-absorbing material to be absorbed and consumed. Through the synergistic effect of the noise reduction principles in the above multiple aspects, a good noise reduction effect can be achieved, which can better ensure a large air volume output, thereby achieving a balance between large air volume and low noise.

[0045] When the above-mentioned bellows noise reduction device is applied to the fresh air cabinet, Figure 3 As shown, the main structure of the fresh air cabinet includes: an upper air box 13 (i.e., the above-mentioned air box noise reduction device), a fan 14, a full heat exchange core 15, a primary filter 16, and a return air box 17; wherein, the specific structure of the upper air box is the above-mentioned air box noise reduction device, and its air inlet 9 is connected to the fan outlet in the fresh air cabinet, and the air outlet 10 serves as the fresh air outlet of the entire fresh air cabinet; inside the fresh air cabinet, under the action of the fan, after the air enters the fresh air cabinet from the return air box, it first passes through the full heat exchange core for temperature adjustment, and then is sent to the air box noise reduction device by the fan; in the air box noise reduction device, noise reduction is first performed through a tilted impedance composite noise reduction structure, and then the principle of reflection silencing is used to further improve the noise reduction effect, and finally the formed fresh air is sent out from the air outlet. The noise reduction process is as follows:

[0046] In the primary noise reduction structure, the lengths of the first connecting section and the second connecting section of the first inner tube are respectively approximately 1 / 4 of the entire first inner tube, and the length of the third connecting section is approximately 1 / 2 of the entire first inner tube. The entire first inner tube adopts a structure in which the inlet and outlet axes are staggered, that is, the first inner tube is arranged as a whole at an angle, thereby increasing the wind path while preventing sound waves from passing through the noise reduction cavity in the form of a narrow sound beam, thereby improving the sound attenuation. In the second connecting section, the aperture of the sound-absorbing through-hole is 2-6 mm, and the perforation rate is 20%-40%. It can reduce the resistance loss while maintaining the change in acoustic impedance caused by the sudden change in cross-section. The phase between the first connecting section and the third connecting section can make the sound waves encounter different cross-sections of the tube 180° different from the reflected sound waves, so that the two have equal amplitudes and opposite phases, interfere with each other, and thus eliminate their passing frequency. In the third connecting section, the aperture of the sound-absorbing through-hole is 2-6 mm, and the perforation rate is 20%-40%. It is wrapped with a first sound-absorbing material with a density of 30-40 kg / m 3 The preferred density is 40kg / m 3 , a polyester fiber sound-absorbing material with a thickness of 10 cm; in addition, a cavity (i.e., the above-mentioned first noise reduction cavity) is left between the outer surface of the first sound-absorbing material and the inner surface of the bellows shell, further enhancing the sound-absorbing effect of the sound-absorbing material at low frequencies;

[0047] In the secondary noise reduction structure, air passes through the first noise reduction cavity and then enters the secondary noise reduction structure. The secondary noise reduction structure is composed of a second sound-absorbing material and a second inner tube. The density of the second sound-absorbing material is 30-40 kg / m 3 The preferred density is 40kg / m 3 2. A polyester fiber sound-absorbing material with a thickness of 10 cm. When air passes through the secondary noise reduction structure, the air passes through the sound-absorbing holes on the second inner insert tube and enters the second sound-absorbing material. Part of the sound waves are absorbed and dissipated, and converted into heat energy.

[0048] Then the air enters the pressure expansion and speed reduction zone. After the pressure expansion and speed reduction, the flow rate of the airflow when it reaches the air outlet filter is reduced, the impact on the air outlet filter is weakened, the regeneration noise is reduced, and the wind flow area of ​​the air outlet filter is increased, thereby improving the utilization rate and service life of the air outlet filter. When the airflow passes through the air outlet filter, due to the resistance of the air outlet filter itself, the sound waves will be reflected. The reflected sound waves enter the second sound-absorbing material, and the energy is consumed and converted into heat energy, thereby achieving the effect of sound absorption and noise reduction. After the airflow passes through the air outlet filter, part of it enters the atmosphere from the top air outlet. Since the air outlet is located on the bellows shell At the middle position of the top surface, its area a is smaller than the area b of the top surface of the bellows shell. After the sound waves reach the top surface of the bellows shell, except for a part that directly enters the atmospheric environment, the rest of the sound waves are reflected, pass through the air outlet filter, and enter the second sound-absorbing material downward. Some of the sound waves are reflected multiple times and interfere with each other to cancel each other out, while the energy of another part of the sound waves is consumed in the porous gaps of the second sound-absorbing material and converted into heat energy. In order to ensure the sound insulation effect and the air volume, the ratio between the air outlet area and the top surface area of ​​the bellows shell should not be too small or too large, and the preferred ratio is 1 / 2>a / b>1 / 8. A comparative test was conducted on the air volume and noise reduction effect of the fresh air cabinet before and after the use of the above-mentioned bellows noise reduction device. The test methods and standards for the fresh air cabinet without the above-mentioned bellows noise reduction device and the fresh air cabinet with the above-mentioned bellows noise reduction device are consistent, and the data are averaged after multiple measurements. The comparison found that: after using the above-mentioned bellows noise reduction device, the noise of the fresh air cabinet was reduced from 45.8dB(A) to 41.5dB(A), and the noise reduction amount can reach 4.3dB(A), while the air volume changed very little, from 631m 3 / h becomes 630m 3 / h, only reduces 1m 3 / h (and this value is within the normal measurement error range). It can be seen that after the above-mentioned bellows noise reduction device is applied to the fresh air cabinet, it can better achieve a balance between large air volume and low noise.

[0049] Example 2

[0050] This embodiment provides a bellows noise reduction device, such as Figure 4As shown, it includes a bellows shell 1, a first sound-absorbing material 2, a first inner tube 3, a second sound-absorbing material 4, a second inner tube 5 and an air outlet filter 6; along the airflow direction, the first sound-absorbing material, the second sound-absorbing material and the air outlet filter are sequentially arranged in the bellows shell, the first inner tube is provided in the middle of the first sound-absorbing material, the second inner tube is provided in the middle of the second sound-absorbing material, the first inner tube and the second inner tube are connected in an inclined structure, and a plurality of sound-absorbing through holes 7 are distributed on the first inner tube and the second inner tube respectively; a pressure diffusion and speed reduction zone 8 is left between the second sound-absorbing material and the air outlet filter, one end of the first inner tube is used as an air inlet 9, and an air outlet 10 is provided on the bellows shell located outside the air outlet filter. Among them, an integral inclined impedance composite noise reduction structure is formed between the inclined first inner tube, the second inner tube and the first sound-absorbing material and the second sound-absorbing material on the periphery thereof, which can take into account the noise reduction effects of both low and high frequencies and improve the noise reduction effect; in addition, the inclined structure staggers the inlet and outlet axes of the internal air duct, which increases the wind path while preventing sound waves from passing through the noise reduction cavity in the form of a narrow sound beam, thereby increasing the sound attenuation; in addition, the combination of the sound-absorbing through-hole and the sound-absorbing material on its outer side forms a good sound-absorbing structure, which can achieve the noise reduction effect while significantly reducing the loss of air volume. The setting of the pressure-expanding and speed-reducing zone utilizes the principle of reflective sound absorption, and with the help of the flow resistance characteristics of the air outlet filter and the reflection of sound waves caused by the non-air outlet part of the bellows shell, forms a high-efficiency reflective sound absorption system with the sound-absorbing material to improve the sound attenuation. In this embodiment, if Figure 5 As shown, the first inner tube and the second inner tube are connected square tubes, and along the airflow direction, the axial section of the first inner tube and the second inner tube connected is an inclined straight tube. According to the actual needs of the fresh air fan, the first inner tube and the second inner tube can adopt a connected one-piece structure or a connected split splicing structure, and the specific inclination angles of the first inner tube and the second inner tube can also be adjusted and selected according to the actual needs of the fresh air cabinet used and the specific position settings of the air inlet and the air outlet.

[0051] like Figure 4 As shown, the first sound-absorbing material and the first inner tube form a primary noise reduction structure; a cavity structure is left between the outer side of the first sound-absorbing material and the inner wall of the bellows shell, and the cavity structure between the primary noise reduction structure and the outer wall of the bellows forms a first noise reduction cavity 11; the second sound-absorbing material and the second inner tube form a secondary noise reduction structure, and a cavity structure is also left between the outer side of the second sound-absorbing material and the inner wall of the bellows shell, and the air structure between the secondary noise reduction structure and the outer wall of the bellows forms a second noise reduction cavity 12. Figure 5As shown, the first inner insert tube includes a first connecting section 3-1, a second connecting section 3-2 and a third connecting section 3-3 connected in sequence along the airflow direction, wherein the outer circumference of the third connecting section is wrapped with a first sound-absorbing material, the second connecting section and the third connecting section extend out of the first sound-absorbing material, and sound-absorbing through holes are respectively distributed on the tube walls of the second connecting section and the third connecting section, and the tube wall of the first connecting section is a smooth closed tube wall; the second inner insert tube includes a fourth connecting section 5-1, a fifth connecting section 5-2 and a sixth connecting section 5-3 arranged in sequence along the airflow direction, wherein the outer circumference of the fourth connecting section is wrapped with a second sound-absorbing material, the fifth connecting section and the sixth connecting section extend out of the second sound-absorbing material, sound-absorbing through holes are respectively distributed on the tube walls of the fourth connecting section and the fifth connecting section, and the tube wall of the sixth connecting section is a smooth closed tube wall.

[0052] The noise reduction principle of the above-mentioned bellows noise reduction device is: first, the first inner tube, the second inner tube and the first sound-absorbing material and the second sound-absorbing material arranged obliquely and arranged thereon are used to form a primary noise reduction structure and a secondary noise reduction structure, so that the internal cavity of the bellows shell on its periphery forms an impedance composite noise reduction cavity. Since the first inner tube and the second inner tube adopt an obliquely arranged structural form, the inlet and outlet axes of the air duct formed by their connection are staggered, so that not only the wind path can be increased, but also the sound waves can not pass through the noise reduction cavity in the form of a narrow sound beam, thereby improving the sound attenuation; second, in the middle section of the first inner tube and the second inner tube (that is, the second connecting section and the fifth connecting section) The sound-absorbing through holes are provided on the wall of the first inner tube (including the first and second inner tubes), which can reduce the loss of airflow resistance while maintaining the change of acoustic impedance caused by the sudden change of the radial cross-section of the air duct. The sound waves between the two end connecting sections of the first inner tube and between the two end connecting sections of the second inner tube (that is, between the first and third connecting sections, and between the fourth and sixth connecting sections) can respectively make the phases of the sound waves encountering different cross-sections of the air duct differ by 180 degrees from the reflected sound waves, so that the phases between the two end connecting sections are opposite and interfere with each other, thereby eliminating their passing frequencies. Thirdly, by providing a sound-absorbing material (including the first and second sound-absorbing materials) between the outer surface of the sound-absorbing material and the inner wall of the bellows shell, The cavity structure (forming the first noise reduction cavity and the second noise reduction cavity) can further enhance the sound absorption effect of the sound-absorbing material at low frequencies; Fourth, after the air passes through the above-mentioned inner tube and the sound-absorbing material for noise reduction, it enters the pressure expansion and speed reduction zone formed between the air outlet filter and the second sound-absorbing material. After the pressure expansion and speed reduction in this area, when the airflow reaches the air outlet filter, its flow rate is reduced, the impact on the air outlet filter is weakened, the regeneration noise is reduced, and the wind flow area of ​​the air outlet filter is increased, thereby improving the utilization rate and service life of the air outlet filter. At the same time, when the airflow passes through the air outlet filter, the sound waves will be reflected due to the resistance of the filter itself, and the reflected sound waves enter the first The energy of the second sound-absorbing material and the second noise reduction cavity around it is consumed and converted into heat energy, thereby achieving a further effect of sound attenuation and noise reduction. Fifth, after the air passes through the air outlet filter, it enters the space between the air outlet filter and the inner wall of the bellows shell outside it. Since the area of ​​the air outlet is smaller than the area of ​​the top surface of the bellows shell where it is located, when the sound waves reach the top surface of the bellows shell, except for a part that directly enters the atmospheric environment from the air outlet, the rest of the sound waves will be reflected. In this process, some sound waves are reflected multiple times and interfere with each other to cancel each other out, while the other part of the sound waves pass through the filter and re-enter the second sound-absorbing material and the second noise reduction cavity around it to be absorbed and consumed. Through the synergistic effect of the noise reduction principles in the above multiple aspects, a good noise reduction effect can be achieved, and a large air volume output can be better guaranteed, thereby achieving a balance between large air volume and low noise.

[0053] When the above-mentioned bellows noise reduction device is applied to the fresh air cabinet, Figure 6As shown, the main structure of the fresh air cabinet includes: an upper air box 13 (i.e., the above-mentioned air box noise reduction device), a fan 14, a full heat exchange core 15, a primary filter 16, and a return air box 17; wherein, the specific structure of the upper air box is the above-mentioned air box noise reduction device, and its air inlet 9 is connected to the fan outlet in the fresh air cabinet, and the air outlet 10 serves as the fresh air outlet of the entire fresh air cabinet; inside the fresh air cabinet, under the action of the fan, after the air enters the fresh air cabinet from the return air box, it first passes through the full heat exchange core for temperature adjustment, and then is sent to the air box noise reduction device by the fan; in the air box noise reduction device, noise reduction is first performed through a tilted impedance composite noise reduction structure, and then the principle of reflection silencing is used to further improve the noise reduction effect, and finally the formed fresh air is sent out from the air outlet. The noise reduction process is as follows:

[0054] In the first-level noise reduction structure, the first noise reduction cavity is an impedance composite noise reduction cavity containing an inner tube. The lengths of the first connecting section and the second connecting section of the first inner tube are respectively about 1 / 4 of the entire first inner tube, and the length of the third connecting section is about 1 / 2 of the entire first inner tube. The entire first inner tube adopts a structure with staggered inlet and outlet axes, that is, the first inner tube is arranged as a whole at an angle, thereby increasing the wind path while preventing sound waves from passing through the noise reduction cavity in the form of a narrow sound beam, thereby improving the sound attenuation; in the second connecting section, the aperture of the sound-absorbing through hole is 2-6mm, The perforation rate is above 20%-40%, which can reduce resistance loss while maintaining the change in acoustic impedance caused by the sudden change in cross-section. The first connecting section and the third connecting section can make the sound waves encounter different cross-sections of the tube and the reflected sound waves 180 degrees out of phase, so that the two have equal amplitudes and opposite phases, interfering with each other, thereby eliminating their passing frequency. In the third connecting section, the aperture of the sound-absorbing through hole is 2-6mm, the perforation rate is 20%-40%, and the outside is wrapped with a first sound-absorbing material with a density of 30-40kg / m 3 The preferred density is 40kg / m 3 , a polyester fiber sound-absorbing material with a thickness of 10 cm; in addition, a cavity (i.e., the above-mentioned first noise reduction cavity) is left between the outer surface of the first sound-absorbing material and the inner surface of the bellows shell, further enhancing the sound-absorbing effect of the sound-absorbing material at low frequencies;

[0055] In the secondary noise reduction structure, air enters the secondary noise reduction structure after passing through the first noise reduction cavity. The second noise reduction cavity is also an impedance composite noise reduction cavity containing an inner tube. The length of the fourth connecting section of the second inner tube is about 1 / 2 of the entire second inner tube, and the lengths of the fifth connecting section and the sixth connecting section are respectively about 1 / 4 of the entire second inner tube. The entire second inner tube adopts a structure with staggered inlet and outlet axes, that is, the second inner tube is arranged as a whole at an angle, thereby increasing the wind path while preventing sound waves from passing through the noise reduction cavity in the form of a narrow sound beam, thereby improving the sound attenuation. The perforation rate in the connecting section is 20%-40%, which can reduce resistance loss while maintaining the change in acoustic impedance caused by the sudden change in cross-section. The fourth and sixth connecting sections allow the sound waves encountering different cross-sections of the tube to have a phase difference of 180° with the reflected sound waves, making the two waves have equal amplitudes but opposite phases, interfering with each other and thus eliminating their passing frequencies. The sound-absorbing holes in the fourth connecting section have a diameter of 2-6 mm and a perforation rate of 20%-40%. The second sound-absorbing material is wrapped on the outside, and the density of the second sound-absorbing material is 30-40 kg / m 3 The preferred density is 40kg / m 3 , a polyester fiber sound-absorbing material with a thickness of 10 cm; in addition, a cavity (i.e., the aforementioned second noise reduction cavity) is left between the outer surface of the second sound-absorbing material and the inner surface of the bellows shell, further enhancing the sound-absorbing effect of the sound-absorbing material at low frequencies;

[0056] Then, the airflow enters the diffusion and speed reduction zone, where it speeds down and expands, reducing the air resistance loss through the outlet filter and increasing the air flow area of ​​the outlet filter, thereby improving the utilization rate and service life of the outlet filter, and finally the air is discharged from the outlet.

[0057] Example 3

[0058] This embodiment is a bellows noise reduction device, which is different from the embodiment 2 in that:

[0059] In the first inner tube, the first connecting section of the tube wall is an open tube wall with sound-absorbing holes distributed throughout. This means that the entire tube wall of the first inner tube is covered with sound-absorbing holes, and the entire outer circumference of the first inner tube is wrapped with a first sound-absorbing material. In the second inner tube, the sixth connecting section of the tube wall is an open tube wall with sound-absorbing holes distributed throughout. This means that the entire tube wall of the second inner tube is also covered with sound-absorbing holes, and the entire outer circumference of the second inner tube is wrapped with a second sound-absorbing material. This structure further enhances the noise reduction effect of the entire bellows noise reduction device.

[0060] As described above, the present invention can be better implemented. The above embodiments are only preferred embodiments of the present invention and are not intended to limit the scope of implementation of the present invention. That is, all equivalent changes and modifications made based on the content of the present invention are covered by the scope of protection required by the claims of the present invention.

Claims

1. A bellows noise reduction device for a fresh air cabinet, characterized in that: The bellows shell comprises a first sound-absorbing material, a first inner insert, a second sound-absorbing material, a second inner insert, and an air outlet filter. The first sound-absorbing material, the second sound-absorbing material, and the air outlet filter are sequentially arranged in the bellows shell along the airflow direction. The first inner insert is arranged in the middle of the first sound-absorbing material, and the second inner insert is arranged in the middle of the second sound-absorbing material. The first inner insert and the second inner insert are connected in an inclined structure, and a plurality of sound-absorbing through holes are distributed on the first inner insert and the second inner insert, respectively. A pressure expansion and speed reduction zone is left between the second sound-absorbing material and the air outlet filter. One end of the first inner insert serves as an air inlet, and an air outlet is arranged on the bellows shell outside the air outlet filter. The first sound-absorbing material and the first inner tube form a primary noise reduction structure; a cavity structure is left between the outer side of the first sound-absorbing material and the inner wall of the bellows shell, and the cavity structure between the primary noise reduction structure and the outer wall of the bellows forms a first noise reduction cavity; The second sound-absorbing material and the second inner tube form a secondary noise reduction structure; the outer side of the second sound-absorbing material is connected to the inner wall of the bellows shell; The first inner insert tube includes a first connecting section, a second connecting section, and a third connecting section sequentially connected along the airflow direction, wherein the outer periphery of the third connecting section is wrapped with a first sound-absorbing material, the second connecting section and the third connecting section extend outside the first sound-absorbing material, and sound-absorbing through holes are distributed on the tube walls of the second connecting section and the third connecting section respectively, and the tube wall of the first connecting section is a smooth closed tube wall or an open tube wall distributed with sound-absorbing through holes; When the outer side of the second sound absorbing material is in contact with the inner wall of the bellows shell, the outer periphery of the entire second inner tube is wrapped with the second sound absorbing material, and sound absorbing through holes are distributed on the tube wall of the entire second inner tube.

2. The bellows noise reduction device for a fresh air cabinet according to claim 1, characterized in that: The first inner tube and the second inner tube are connected circular tubes or square tubes; along the airflow direction, the axial section where the first inner tube and the second inner tube are connected is in an inclined straight tube shape or an expanded shape.

3. The bellows noise reduction device for a fresh air cabinet according to claim 1, characterized in that: The aperture of the sound-absorbing through hole is 2-6 mm, and the perforation rate of the sound-absorbing through hole is 20-40%.

4. The bellows noise reduction device for a fresh air cabinet according to claim 1, characterized in that: The first sound absorbing material and the second sound absorbing material are respectively made of a density of 30-40 kg / m 3 Polyester fiber sound-absorbing material.

5. The bellows noise reduction device for a fresh air cabinet according to claim 1, characterized in that: The air outlet is arranged in the middle of the top surface of the bellows shell, and the area of ​​the air outlet accounts for 1 / 8 to 1 / 2 of the area of ​​the top surface of the bellows shell.

6. A method for using the bellows noise reduction device for a fresh air cabinet according to any one of claims 1 to 5, characterized in that: The bellows noise reduction device is installed on the upper part of the fresh air cabinet, the air inlet is connected to the fan outlet in the fresh air cabinet, and the air outlet serves as the fresh air outlet of the entire fresh air cabinet; Inside the fresh air cabinet, under the action of the fan, after the air enters the fresh air cabinet from the return air box, it first passes through the full heat exchange core for temperature adjustment, and then is sent into the bellows noise reduction device by the fan; in the bellows noise reduction device, noise reduction is first performed through the inclined impedance composite noise reduction structure, and then the principle of reflection silencer is used to further improve the noise reduction effect, and finally the formed fresh air is sent out from the air outlet.

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