Ventilation and noise reduction structure and equipment

Abstract

The invention relates to the field of noise and vibration control service in the advanced environmental protection industry, in particular to a ventilation and noise reduction structure and equipment. The ventilation and noise reduction structure comprises N bent pipeline sets, N is larger than or equal to 1, and each bent pipeline set comprises a first bent pipeline, a second bent pipeline and a third bent pipeline, a second bending path of which the inlet area is S2 and the path length is L2 is formed on the inner side of the second bending pipeline; a direct flow path is formed on the inner side of the straight-through pipeline; wherein the N bent pipeline groups and the direct-current channel are symmetrical about the longitudinal central plane SL of the ventilation and noise reduction structure, and the first bent pipeline and the second bent pipeline meet the requirement of # imgabs0 #. According to the ventilation and noise reduction structure, the path length and the frequency shift hole in the ventilation pipeline are reasonably arranged, so that transmission peaks in different modes are eliminated, and then the sound insulation frequency band of the ventilation and noise reduction structure is expanded.

Description

Technical Field

[0001] The present invention relates to the fields of noise and vibration control services in the advanced environmental protection industry, and particularly to a structure and device for ventilation and noise reduction. Background Art

[0002] With the development of technology and society, metamaterials with ventilation and noise functions have received increasing attention in the fields of architecture and transportation. The core lies in achieving effective regulation of sound waves through specially designed material structures, thereby reducing noise transmission while ensuring air circulation.

[0003] Currently, the research mechanism in this field mainly stems from the local resonance principle, and metamaterials with low-frequency broadband noise suppression capabilities have been designed. For example, mode resonance ventilation is utilized on the sidewall as a soft boundary (low impedance surface) to achieve strong reflection and transmission loss. Or multiple Helmholtz resonators are used to modulate the loss and acoustic reactance of the resonator to achieve strong sound absorption or strong dissipation. Although the resonators on the sidewall can ensure ventilation, the narrowband nature of Helmholtz resonance results in resonance transmission hindering broadband noise reduction.

[0004] Another form is to adopt a bent path in the pipeline based on the mechanism of multiple scattering resonance. Only when resonance occurs can sound be transmitted, and other frequencies cannot be transmitted due to impedance mismatch, resulting in strong reflection. However, the bent path will reduce the ventilation performance. Therefore, some studies have improved the ventilation by configuring a bent pipeline in parallel with a straight pipeline. This will introduce the Fano resonance mechanism and still achieve low transmission between resonance frequencies. However, its resonant characteristics still limit the broadening of the frequency band. Further, some studies utilize the resonance of two channels to construct degenerate modes of monopoles and dipoles to eliminate the transmission peak and achieve the splicing of low-transmission bands. In theory, parallelly connecting more resonant channels can further broaden the broadband sound insulation, but this will lead to a decline in ventilation performance.

[0005] However, in the process of implementing the present invention, the applicant found that the above-mentioned prior art has the following technical defects: the resonant transmission characteristics of the bent pipeline limit the broadening of the frequency band of the ventilation and noise reduction structure. Summary of the Invention

[0006] I. Technical Problems to be Solved

[0007] The present invention expects to at least partially solve one of the above-mentioned technical problems.

[0008] II. Technical Solutions

[0009] The first aspect of the present invention provides a ventilation and noise reduction structure. The ventilation and noise reduction structure includes:

[0010] N groups of bent pipeline groups, N≥1, and each bent pipeline group includes:

[0011] The first bent pipe, with a first bent path formed on its inner side, having an inlet area of S1 and a path length of L1;

[0012] The second bent pipe, with a second bent path formed on its inner side, having an inlet area of S2 and a path length of L2;

[0013] The straight pipe, with a direct current path formed on its inner side;

[0014] Among them, N groups of bent pipe groups and the direct current channels are all symmetric about the longitudinal central plane SL of the ventilation and noise reduction structure, and the first and second bent pipes satisfy:

[0015] The second aspect of the present invention provides a ventilation and noise reduction device. The ventilation and noise reduction device includes: one or more of the above ventilation and noise reduction structures, which are used in the air duct machine of the air conditioning system or the telescopic pipe of the range hood.

[0016] III. Beneficial effects

[0017] From the above technical solutions, it can be seen that the present invention has at least one of the following beneficial effects compared with the prior art:

[0018] (1) In some embodiments of the present invention, the second-order transmission peak of the first bent pipe and the third-order transmission peak of the second bent pipe have equal frequencies, and the third-order mode is a dipole mode, and the second-order mode is a monopole mode. Therefore, a degenerate mode is generated, resulting in the disappearance of the transmission peak, thereby generating a wider sound insulation frequency band.

[0019] (2) In some embodiments of the present invention, frequency-shifting holes are provided on the baffle between the pipes. The position of the frequency-shifting holes is at the symmetric center of the bent pipe, so as to ensure that the holes are at the modal nodes, affecting the modal frequency of one bent pipe and not affecting the other modal frequency, causing the two modal frequencies to approach, realizing the degenerate coupling mode and eliminating the transmission peak..

[0020] (3) In some embodiments of the present invention, frequency-shifting holes - hole 1 and hole 2 are provided on both baffles between the pipes. The function of the two frequency-shifting holes is to adjust the first-order mode of the bent pipe L1 and the second-order mode of the bent pipe L2 to form a degenerate mode and eliminate the transmission peak. Another function of hole 2 is to adjust the third-order mode of the bent pipe L2 and the second-order mode of the bent pipe L1 to form a degenerate mode and eliminate the transmission peak. By setting like this, it is possible to eliminate four transmission peaks caused by resonance. The connection of three low-transmission intervals is realized, and the ventilation and sound insulation frequency band is broadened.

[0021] (4) In some embodiments of the present invention, two or more sets of bent pipe groups are provided. Compared with only one set of bent pipe groups, the multi-bent channel groups increase the design freedom of the structure, provide more adjustable parameters, so that more degenerate modes can be achieved, more transmission peaks can be eliminated, and the sound insulation performance can be further improved.

[0022] (5) In summary, by reasonably setting the path length and frequency shift holes in the ventilation duct, the present invention achieves the elimination of transmission peaks in different modes, and further realizes the expansion of the sound insulation frequency band of the ventilation noise reduction structure. Description of the Drawings

[0023] Figure 1 It is the sound transmission coefficient curve and the structural schematic diagram of the first embodiment of the ventilation noise reduction structure of the present invention.

[0024] Figure 2 and Figure 3 respectively are Figure 1 the sound transmission coefficient curve and the structural schematic diagram of the shown ventilation noise reduction structure without the first bent pipe and without the second bent pipe.

[0025] Figure 4 It is the sound transmission coefficient curve and the structural schematic diagram of the second embodiment of the ventilation noise reduction structure of the present invention.

[0026] Figure 5 It is the sound transmission coefficient curve and the structural schematic diagram of the third embodiment of the ventilation noise reduction structure of the present invention.

[0027] Figure 6 It is the structural schematic diagram of the fourth embodiment of the ventilation noise reduction structure of the present invention. Detailed Embodiments

[0028] By reasonably setting the path length and frequency shift holes in the ventilation duct, the present invention achieves the elimination of transmission peaks in different modes, and further realizes the expansion of the sound insulation frequency band of the ventilation noise reduction structure.

[0029] To make the purpose, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the specific embodiments and with reference to the drawings.

[0030] The first aspect of the present invention provides a ventilation noise reduction structure. Figure 1 It is the sound transmission coefficient curve and the structural schematic diagram of the first embodiment of the ventilation noise reduction structure of the present invention. Figure 2 and Figure 3 respectively are Figure 1 the sound transmission coefficient curve and the structural schematic diagram of the shown ventilation noise reduction structure without the first bent pipe and without the second bent pipe.

[0031] As Figure 1As shown in the middle right figure, the ventilation and noise reduction structure of this embodiment includes: a straight-through pipe formed in the overall pipe and a group of bent pipe groups. The cross-sectional area of the overall pipe is S0.

[0032] Among them, for the straight-through pipe, a direct current path with an inlet area of S3 and a path length of L3 is formed on its inner side.

[0033] Among them, the bent pipe group includes:

[0034] ① The first bent pipe, on its inner side, a first bent path with an inlet area of S1 and a path length of L1 is formed;

[0035] ② The second bent pipe, on its inner side, a second bent path with an inlet area of S2 and a path length of L2 is formed;

[0036] Among them, the bent pipe group and the direct current channel are both symmetric about the longitudinal central plane SL of the ventilation and noise reduction structure, and the first and second bent pipes satisfy:

[0037] The following will respectively describe in detail each component of the ventilation and noise reduction structure of this embodiment.

[0038] As Figure 1 shown, the first bent pipe and the second bent pipe are separated by a baffle between pipes; the straight-through pipe and the adjacent bent pipe are separated by a baffle between pipes. Inside the first bent pipe and the second bent pipe, a plurality of path baffles extending alternately from the upper and lower surfaces towards the opposite side form the corresponding bent paths. And, the straight-through pipe is symmetric about the longitudinal central plane SL; the path baffles within the same bent pipe are symmetric about the longitudinal central plane SL.

[0039] In this embodiment, the longitudinal cross-section of the straight-through pipe is rectangular. For the first bent pipe and the second bent pipe, their longitudinal cross-sections are also rectangular, and moreover, the heights of the first and second bent pipes are different from that of the straight-through pipe. In the two bent channels, the path baffles are also rectangular. However, the present invention is not limited to this. In other embodiments of the present invention, the longitudinal cross-sectional shapes of the straight-through pipe and the bent pipe can also be other shapes, such as: circular or elliptical, and the path baffles match the longitudinal cross-sectional shapes of the pipes, such as: semi-circular, semi-elliptical, triangular, etc.

[0040] In this embodiment, the height l of the path baffle satisfies: The thickness t of the path baffle satisfies: And the spacing between adjacent path baffles within the same bent pipe is the same, but the present invention is not limited to this. In other embodiments of the present invention, the height l of the path baffle satisfies: The thickness t of the path baffle and the baffle between pipes satisfies: The distances between adjacent path baffles within the same bent pipe are different. As long as the path baffles within the same bent pipe are symmetric about the longitudinal central plane SL, although the effects of these cases are slightly inferior to those of this embodiment, the present invention can still be achieved and is also within the protection scope of the present invention.

[0041] As Figures 1 to 3 shown, the first and second bent paths are formed by connecting the central positions of the ventilation areas on the pipe longitudinal section that are not blocked by the path baffles. The path length L1 of the first bent pipe satisfies: The path length L2 of the second bent pipe satisfies: where M and N respectively represent the numbers of path baffles within the first and second bent pipes, and l m is the height of the m-th path baffle in the first bent pipe, and l n is the height of the n-th path baffle in the second bent pipe.

[0042] In this embodiment, the inlet areas of the straight pipe, the first bent pipe, and the second bent pipe satisfy However, the present invention is not limited thereto. Through experiments, the applicant has confirmed that deviating from the above values within a certain range can also achieve the present invention. The specific range is:

[0043] The technical effects of the ventilation and noise reduction structure of this embodiment will be described below.

[0044] It should be particularly noted that the ventilation and noise reduction structure of this embodiment is composed of two bent pipes and a straight pipe connected in parallel. The overall model structure has symmetry and is symmetric about the longitudinal central plane SL. The distances between adjacent path baffles can be different, but they must satisfy left-right symmetry about the longitudinal central plane. The acoustic mode of the pipe is related to the bent pipe. Through symmetry about the longitudinal central plane SL, it is beneficial to adjust the structural parameters of the bent pipe to achieve the degenerate coupling mode and eliminate the resonance peak. The following will be described in detail.

[0045] The sound transmission coefficient is calculated by establishing a finite element model, which represents the acoustic performance of the structure. The lower the value, the better the acoustic performance. The sound transmission coefficient can be obtained through calculation. Among them, the first - order and second - order represent resonance modes. When noise propagates in a bent pipe, resonance will cause the appearance of transmission peaks, and the frequency where the transmission peak is located is the resonance frequency. The resonance frequencies of a bent pipe appear in integer multiples, which is an inherent property of resonance transmission. Resonance modes can be divided into two categories. The sound wave phases on both sides of the structural resonance transmission are different for the dipole mode and the same for the monopole mode. When the two modes occur at the same frequency, a monopole - dipole degenerate coupling mode (degenerate mode) will be formed. The transmission characteristics of the monopole and dipole resonance modes are that the sound pressure magnitudes of the two in the transmission field are the same and the phases are opposite. When they occur at the same frequency, the sound waves passing through the structure will cancel each other out, eliminating the noise, and thus the transmission peak disappears. In this way, the third - order resonance frequency of the first bent pipe is equal to the second - order modal frequency of the second pipe.

[0046] As Figure 2 shown, when there are only the first bent pipe and the straight pipe, the first - order mode of the first bent pipe causes the Figure 1 first - order transmission peak. As Figure 3 shown, when there are only the second bent pipe and the straight pipe, the second - order mode of the second bent pipe causes the Figure 1 second - order transmission peak. The second - order transmission peak of the first bent pipe and the third - order transmission peak of the second bent pipe have the same frequency, and the third - order mode is the dipole mode and the second - order mode is the monopole mode. Therefore, a degenerate mode is generated, resulting in the disappearance of the transmission peak, thus generating a wider sound insulation frequency band, as shown in the left figure of Figure 1 .

[0047] The transmission peak is caused by modal resonance. The frequency of the transmission peak is equal to the resonance frequency. The relationship between the resonance frequency and the pipe path length is that for the first bent pipe, f1 = n1c0 / 2L1, and for the second bent pipe, the resonance frequency f2 = n2c0 / 2L2, where c0 represents the speed of sound, and n1 and n2 represent the modal orders of the first bent channel and the second bent channel. To achieve the degenerate mode, it is necessary to make the frequency of the third - order mode (n1 = 3) of the first bent pipe equal to the frequency of the second - order mode (n2 = 2) of the second bent pipe. The third - order mode is the dipole resonance mode, and the second - order mode is the monopole resonance mode. If f1 = f2, then L1 / L2 = 1.5 is required to satisfy this relationship. When S2 / S1 = L1 / L2, the sound transmission coefficient can be less than 0.1 to achieve the optimal noise reduction performance. Therefore, S2 / S1 = 1.5.

[0048] Based on the above, in this embodiment, the sound transmission coefficients of the straight pipe, the first bent pipe, the second bent pipe and the ventilation noise reduction structure satisfy:

[0049]

[0050] where α n = S n / S0, ψ n = -i / sin(k0L n ), φ n = -i cot(k0L n ), k0 = ω / c0, n = 1, 2, 3; i is the imaginary unit, ω is the angular frequency, c0 = 343 m / s is the speed of sound.

[0051] Figure 4 It is the sound transmission coefficient curve and the structural schematic diagram of the second embodiment of the ventilation and noise reduction structure of the present invention. This embodiment is improved on the basis of the ventilation and noise reduction structure shown in Figure 1 , and the difference lies in that: a frequency shift hole is opened on the baffle between the two bent pipes to further expand the sound insulation frequency band.

[0052] As shown in the right figure of Figure 4 , a first frequency shift hole - hole 1 is opened on the baffle between the first bent pipe and the second bent pipe. This hole 1 is a circular hole; its area is: It is located at the middle position of the baffle between the pipes and is symmetric about the longitudinal central plane SL.

[0053] In this embodiment, hole 1 is a circular hole, but the present invention is not limited thereto. In other embodiments of the present invention, the shape of the frequency shift hole can also be regular polygons such as triangles and squares, or circles and ellipses. The area size of hole 1 can be: The position of hole 1 on the baffle between the pipes can deviate within a certain range, and this range is aL3, 0.49 ≤ a ≤ 0.51. These above deformation methods can also achieve the present invention and are also within the protection scope of the present invention.

[0054] In this embodiment, 1 frequency shift hole is opened on the baffle between the two bent pipes, but the present invention is not limited thereto. In other embodiments of the present invention, 2, 3 or more frequency shift holes can also be opened on the baffle between the two bent pipes, and the diameter of the frequency shift hole can also be adjusted as needed, as long as it is symmetric about the longitudinal central plane SL, the present invention can also be achieved and is also within the protection scope of the present invention.

[0055] It should be particularly noted that the position of the frequency shift hole is at the symmetric center of the bent pipe, so as to ensure that the hole is at the modal node, affecting the modal frequency of one of the bent pipes and not affecting the other modal frequency, resulting in the two modal frequencies approaching, realizing the degenerate coupling mode and eliminating the transmission peak.

[0056] According to the acoustic propagation theory, the structural characteristics of the frequency-shifting holes of the baffle between pipes determine that if the frequency-shifting holes are at the modal nodes, that is, at the spatial position where the sound pressure is zero, the frequency-shifting holes will not affect the mode; if they are at the modal nodes, the resonance frequency will be changed. The larger the diameter of the frequency-shifting hole, the higher the resonance frequency will shift towards the high-frequency range, and the diameter of the frequency-shifting hole is affected by the size of the modal node. Connecting two bent pipes, the structural symmetry determines that when the frequency-shifting holes are at the center position of the bent pipes, the following effects will occur: for the first-order mode of the first bent pipe, the frequency-shifting holes are not at the modal nodes, so the first-order resonance frequency shifts towards the high-frequency range, approaching the second-order mode of the second bent pipe, as shown in Figure 4 the left middle figure. Setting the frequency-shifting holes can increase the damping effect. By shifting the resonance frequency, the noise energy dissipation can be improved, which can assist in enhancing the acoustic performance.

[0057] According to Professor Ma Dayou's perforated plate theory, for the working principle of the holes, a large sound pressure difference is required on both sides of the holes to modulate the frequency towards the high-frequency range. When the frequency-shifting holes are on the longitudinal center plane SL, for the dipole resonance mode, one side of the frequency-shifting hole is at the position of the maximum sound pressure and the other side has a smaller sound pressure, so the sound pressure difference between the two sides of the frequency-shifting hole is large; while for the monopole resonance mode, the frequency-shifting holes are at the modal nodes, and the sound pressure at the modal nodes is very small, and the sound pressure on the other side is also small, so the sound pressure difference between the two sides is small, and the frequency-shifting holes do not work. Therefore, at non-modal nodes, the change in the diameter of the frequency-shifting holes will cause the transmission peak frequency to shift towards the high-frequency range, increasing with the increase in the area of the frequency-shifting holes; while at modal nodes, the presence of the frequency-shifting holes has no significant effect on the transmission peak frequency, and this characteristic is only related to whether the position of the frequency-shifting holes is at the modal nodes or not.

[0058] The position of the frequency-shifting holes needs to be opened at the modal nodes to break the resonant transmission characteristics, so that only the dipole resonance mode can be adjusted to shift towards the high-frequency range and has no influence on the monopole resonance mode, so that the two resonance modes can form a degenerate mode. Therefore, it is necessary to find the opening at the modal nodes. If the structure has symmetry, then the position of the modal nodes is on the longitudinal center plane SL. Therefore, the position and structural model of the frequency-shifting holes need to satisfy symmetry about the SL plane. If the structure has no symmetry, then the modal nodes cannot be found. For the frequency-shifting holes that are not at the modal nodes, the characteristic of shifting both resonance modes towards the high-frequency range cannot achieve the function of modulating the frequency to form a degenerate mode and eliminating the transmission peak.

[0059] The shape of the frequency-shifting holes does not affect the characteristic of adjusting the modal frequency towards the high-frequency range, so it only needs to satisfy symmetry about the longitudinal center plane SL. Therefore, the shape of the frequency-shifting holes can be regular polygons or circles.

[0060] Taking the circular frequency-shifting holes as an example, the optimal diameter of the frequency-shifting holes for adjusting the mode is about 1 mm, and the corresponding cross-sectional area S0 of the pipe is 1600 mm 2, so the optimal size of the frequency shift hole area is Such a proportional relationship is more conducive to achieving degenerate mode elimination of transmission peak.

[0061] When the aperture of the frequency-shifting hole is too large, even though the frequency-shifting hole is located at the center of the model and at the modal node, i.e., on the symmetry plane SL, the transmission peak caused by the monopole resonance mode still moves toward the high frequency direction. Because when the aperture exceeds the modal node size, the frequency-shifting hole structure will interfere with the modal vibration shape, and the sound pressure on one side of the frequency-shifting hole will increase, thus generating a sound pressure difference on both sides, which will affect the originally unmodulated mode. An overly large aperture, whether it is a monopole or dipole resonance mode, will destroy its inherent characteristics, causing all transmission peaks to move toward high frequencies, making it impossible to achieve degenerate coupled modes. This shows that the matching relationship between the aperture and the modal node size needs to be comprehensively considered during the modal control process.

[0062] Figure 5 The sound transmission coefficient curve and structural diagram of the third embodiment of the ventilation noise reduction structure of the present invention are shown in FIG. Figure 4 The improvement is based on the ventilation and noise reduction structure shown in the figure, and the difference is that in addition to hole 1, a second frequency shift hole - hole 2 is also opened between the second bent pipe and the straight pipe to further expand the sound insulation frequency band.

[0063] If the frequency shift hole in the middle of the curved pipe is not enough to adjust the resonant frequencies of the two modes to be equal, you can open another hole between the curved pipe and the straight pipe. The modulation effects of these two holes are superimposed. Figure 5 As shown in the middle right figure, in addition to hole 1, a second frequency shift hole, hole 2, is also opened between the second curved pipe and the straight pipe. This hole 2 is also a circular hole, and its area is: It is located in the middle of the inter-pipe baffle between the second bent pipe and the straight pipe, and is symmetrical about the longitudinal center plane SL.

[0064] about Figure 4 The deformation of the shape, area and position of the frequency shift hole in the example shown is also applicable to this embodiment and will not be described in detail here.

[0065] It should be noted that the holes of the second curved pipe and the straight pipe must be opened at the center position so as not to affect the second-order mode of the curved pipe.

[0066] According to the acoustic propagation theory, the function of hole 1 and hole 2 is to adjust the first-order mode of the curved duct L1 and the second-order mode of the curved duct L2 to form a degenerate mode and eliminate the transmission peak. Another function of hole 2 is to adjust the third-order mode of the curved duct L2 and the second-order mode of the curved duct L1 to form a degenerate mode and eliminate the transmission peak. By setting it in this way, it is possible to eliminate four transmission peaks caused by resonance. The connection of three low-transmission intervals is realized, which broadens the ventilation sound insulation frequency band, such asFigure 5 as shown

[0067] Figure 6 This is a schematic structural view of the fourth embodiment of the ventilation and noise reduction structure of the present invention. This embodiment is improved on the basis of the Figure 5 ventilation and noise reduction structure as shown, and the difference lies in: 2 groups of bent pipe groups - the first bent pipe group and the second bent pipe group.

[0068] The first bent pipe group includes:

[0069] ① The first bent pipe, the inner side of which forms a first bent path with an inlet area of S11 and a path length of L11;

[0070] ② The second bent pipe, the inner side of which forms a second bent path with an inlet area of S21 and a path length of L21;

[0071] The second bent pipe group includes:

[0072] ① The first bent pipe, the inner side of which forms a first bent path with an inlet area of S12 and a path length of L12;

[0073] ② The second bent pipe, the inner side of which forms a second bent path with an inlet area of S22 and a path length of L22;

[0074] Figure 6 The ventilation and noise reduction structure model as shown is symmetric about the central plane SL. Regarding the relevant parameters of each bent pipe and frequency shift hole in the first bent pipe group and the second bent pipe group, reference can be made to the relevant descriptions above. Hole 1 is between the bent pipes L11 and L21, hole 2 is between the bent pipe L21 and the straight pipe L3, hole 3 is between the straight pipe L3 and the bent pipe L12, and hole 4 is between the straight pipes L12 and L22. All the holes are located at L' = aL3, where 0.49 ≤ a ≤ 0.51. The cross-sectional area of the hole is 0.9 ≤ a ≤ 1.1.

[0075] In addition to this, the bent pipes in the first bent pipe group and the second bent pipe group also need to satisfy:

[0076]

[0077] wherein, S21 and L21 are respectively the inlet area and path length of the second bent pipe in the first bent pipe group, and S12 and L12 are respectively the inlet area and path length of the first bent pipe in the second bent pipe group.

[0078] It should be noted that this embodiment can also have many deformation methods, for example:

[0079] ① The number of bent pipe groups

[0080] In this embodiment, there are 2 groups of bent pipe groups, but the present invention is not limited thereto. In other embodiments of the present invention, there may also be 3 groups, 4 groups, 5 groups or more groups of bent pipe groups.

[0081] ② Position of the straight pipe

[0082] In this embodiment, the straight pipe is located between 2 groups of bent pipe groups, but the present invention is not limited thereto. In other embodiments of the present invention, the straight pipe group may also be located above or below the 2 groups of bent pipe groups.

[0083] ③ Number of straight pipes

[0084] In this embodiment, there is 1 straight pipe, but the present invention is not limited thereto. In other embodiments of the present invention, there may also be 2, 3 or more straight pipes.

[0085] ④ Arrangement of frequency shift holes

[0086] In this embodiment, frequency shift holes are provided on each baffle between pipes, but the present invention is not limited thereto. In other embodiments of the present invention, frequency shift holes may also be selectively provided on some baffles between pipes.

[0087] For Figure 6 In the shown ventilation and noise reduction structure, the bent pipe L11 will generate multiple transmission peaks due to resonance. The functions of holes 1 and 2 are to adjust the first-order modal frequency of the bent pipe L21 to be close to the second-order modal of L11, so as to generate a degenerate mode and eliminate the transmission peaks. In addition, hole 1 can adjust the third-order modal of the bent pipe L11 to move to a higher frequency to form a degenerate mode with the second-order modal of the bent pipe L12, thereby eliminating the transmission peaks. Hole 2 can adjust the third-order modal of the bent pipe L21 to form a degenerate mode with the fourth-order modal of the bent pipe L1 to eliminate the transmission peaks. The functions of holes 3 and 4 are to adjust the first-order modal of the bent pipe L22 to form a degenerate mode with the second-order modal of the bent pipe L12 to eliminate the transmission peaks.

[0088] Compared with only 1 group of bent pipe groups, the multi-bent channel group in this embodiment increases the design freedom of the structure, provides more adjustable parameters, so as to be able to achieve more degenerate modes, eliminate more transmission peaks, and further improve the sound insulation performance.

[0089] The second aspect of the present invention provides a ventilation and noise reduction device. In an exemplary example of the present invention, the ventilation and noise reduction device includes: one or more ventilation and noise reduction structures as above, which are used in the air duct machine of the air conditioning system or the telescopic pipe of the range hood.

[0090] So far, the various embodiments of the present invention have been introduced. Based on the above description, those skilled in the art should have a clear understanding of the present invention.

[0091] It should be noted that for some implementation manners, if they are not the key content of the present invention and are well-known to those of ordinary skill in the art, due to space limitations, they are not described in detail in the specification drawings or the text. In this case, reference may be made to the relevant prior art for understanding.

[0092] For the numerical values and numerical ranges mentioned in the present invention, unless clearly indicated to the contrary, the numerical parameters in the specification and claims of the present invention may be approximate values and can be changed according to the content of the present invention. Specifically, all the numbers indicating the content of the composition, reaction conditions, etc. recorded in the specification and claims should be understood to be modified by the term "about" in all cases, and the meaning expressed is that it includes a change of ±10% of a specific quantity in some embodiments.

[0093] For the ordinal numbers used in the present invention, such as "first", "second", as well as Arabic numerals, letters, etc., which are used to modify the corresponding elements, their original intention is only to clearly distinguish one element with a certain name from another element with the same name, and does not mean that the element has any ordinal number, nor does it represent the order of one element and another element.

[0094] For the directional terms mentioned in the present invention, such as "center", "lateral", "longitudinal", "upper", "lower", "front", "rear", "left", "right", "inner", "outer", etc., the indicated orientation or positional relationship is only based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation on the present invention. And throughout the drawings, the same elements are represented by the same or similar reference numerals. And the shapes and sizes of the components in the drawings do not reflect the actual sizes and proportions, but only illustrate the content of the embodiments of the present invention.

[0095] Those skilled in the art should understand that in the claims and the specification of the present invention, the word "comprising" does not exclude the existence of elements (or steps) not listed in the claims. The word "a" or "an" before an element (or step) does not exclude the existence of a plurality of such elements (or steps).

[0096] Moreover, the purpose of providing the above embodiments is only to make the present invention meet the legal requirements, and the present invention can be implemented in many different forms and should not be construed as limited to the embodiments described herein.

[0097] Similarly, it should be understood that, for the sake of streamlining the present invention, in the above description of the exemplary embodiments of the present invention, various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, the method of the invention should not be construed as reflecting the intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as reflected by the claims, the various aspects of the invention lie in less than all the features of the preceding single embodiment. Also, the embodiments may be used in combination with each other or with other embodiments based on considerations of design and reliability, i.e., the technical features in different embodiments can be freely combined to form more embodiments. Therefore, the claims following the specific embodiments are hereby expressly incorporated into the specific embodiments, where each claim itself serves as a separate embodiment of the present invention.

[0098] In the above specific embodiments, the purpose, technical means, and beneficial effects of the present invention have been described in detail. It should be understood that the purpose of the detailed description is for those skilled in the art to understand the present invention more clearly and is not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A ventilation and noise reduction structure, characterized in that, Including: N sets of bent pipe groups, where N≥1, and each bent pipe group includes: A first bent pipe, with a first bent path having an inlet area of S1 and a path length of L1 formed on its inner side; A second bent pipe, with a second bent path having an inlet area of S2 and a path length of L2 formed on its inner side; A straight-through pipe, with a straight-through path formed on its inner side; Among them, the N groups of bent pipe groups and the DC channels are both symmetric about the longitudinal central plane SL of the ventilation and noise reduction structure, and the first and second bent pipes satisfy:

2. The ventilation and noise reduction structure according to claim 1, wherein Adjacent bent pipes are separated by baffles between pipes; The straight-through pipe and adjacent bent pipes are separated by baffles between pipes; The straight-through pipe is symmetric about the longitudinal center plane SL; Inside the bent pipe, a plurality of path baffles extending alternately from the upper and lower surfaces towards the opposite side form corresponding bent paths. The distance between adjacent path baffles in the same bent pipe is the same or different, and the path baffles in the same bent pipe are symmetric about the longitudinal center plane SL. The bent pipe is the first bent pipe or the second bent pipe.

3. The ventilation and noise reduction structure according to claim 2, wherein A straight-through path with an inlet area of S3 and a path length of L3 is formed inside the straight-through pipe; The N sets of bent pipe groups and the straight-through pipe are formed inside an overall pipe, and the cross-sectional area of this overall pipe is S0; The inlet area S3 of the straight-through pipeline satisfies:

4. The ventilation and noise reduction structure according to claim 3, wherein, The sound transmission coefficients of the straight-through pipe, the first bent pipe, the second bent pipe and the ventilation and noise reduction structure satisfy: where α n = S n / S0, ψ n = -i / sin(k0L n ), φ n = -i cot(k0L n ), k0 = ω / c0, n = 1, 2, 3; i is the imaginary unit, ω is the angular frequency, c0 = 343 m / s is the speed of sound.

5. The ventilation and noise reduction structure according to claim 3, wherein The height l of the described path baffle satisfies: And / or, the thickness t of the path baffle and the pipe baffle satisfies: And / or, the path length L1 satisfies: The path length L2 satisfies: where M and N respectively represent the number of path baffles in the first and second bent pipes, l m is the height of the m-th path baffle in the first bent pipe, l n is the height of the n-th path baffle in the second bent pipe.

6. The ventilation and noise reduction structure according to claim 5, wherein The longitudinal section of the pipe is one of the following shapes: rectangular, circular, elliptical; And / or, the shape of the path baffle is one of the following shapes: rectangular, semi-circular, triangular; And / or, the bent path is formed by connecting the central positions of the ventilation areas not covered by the path baffle on the longitudinal section of the pipe, and the path is the first bent path or the second bent path.

7. The ventilation and noise reduction structure according to claim 1, wherein N = 1, where a set of bent pipe group and the straight-through pipe are formed inside an overall pipe; or, N = 2; where two sets of bent pipe groups and the straight-through pipe are formed inside an overall pipe; Satisfied: Wherein, S21 and L21 are respectively the inlet area and path length of the second bent pipe in the first bent pipe group, and S12 and L12 are respectively the inlet area and path length of the first bent pipe in the second bent pipe group.

8. The ventilation and noise reduction structure according to claim 1, characterized in that, A frequency shifting hole is opened at one of the following positions: ① The baffle between the first bent pipe and the second bent pipe; ② The baffle between the straight-through pipe and the adjacent bent pipe; Wherein, the position L' of the frequency shifting hole on the baffle between pipes satisfies: L' = a×L3, 0.45≤a≤0.

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9. The ventilation and noise reduction structure according to claim 8, wherein The frequency shifting hole is a regular polygon or a circle; And / or, the frequency shifting hole is located at the middle position of the baffle between pipes and is symmetric about the longitudinal center plane SL; And / or, frequency shifting holes are opened at both of the following two positions: ① The baffle between the first bent pipe and the second bent pipe; ② The baffle between the straight-through pipe and the adjacent bent pipe; And / or, the area S' of the frequency shift hole satisfies:

10. A ventilation and noise reduction device, characterized in that, Including: One or more ventilation and noise reduction structures according to any one of claims 1 to 9, for use in the air duct machine of an air conditioning system or the telescopic pipe of a range hood.

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