Acoustic liner, power propulsion system and method of designing the same

Abstract

The application provides an acoustic liner, a power propulsion system and a design method thereof. The acoustic liner comprises a perforated panel, a cavity structure and a back plate. The perforated panel is provided with through holes; the cavity structure comprises a plurality of pipes; the perforated panel and the back plate are respectively connected to opposite sides of the cavity structure, so that the perforated panel, the cavity structure and the back plate jointly enclose a plurality of cavities which are open at the top and closed at the bottom; the perforated panel comprises a panel body and a plurality of thickening portions, the thickening portions correspondingly extend to the interiors of the plurality of pipes from the panel body along the thickness direction, and the thickening portions are attached to the pipes, so that the depth of the cavity is defined by the thickening portions and the back plate; and the part of the perforated panel, the pipe and the part of the back plate which jointly enclose a single cavity provide a single sound absorption structure unit, and the thicknesses of the thickening portions of at least two sound absorption structure units are different.

Description

Technical Field

[0001] This application relates to the field of gas turbine technology, specifically to acoustic linings, power propulsion systems, and their design methods. Background Technology

[0002] Power propulsion systems, such as aircraft engines in gas turbines, need to suppress noise in order to reduce noise pollution to the working environment and surrounding areas.

[0003] Acoustic liners are an important means of suppressing mechanical noise from impellers. Generally, an acoustic liner consists of a perforated plate, an intermediate layer with acoustic channels, and a back plate, forming a sound-absorbing structure such as a Helmholtz resonator. A single Helmholtz resonator has excellent sound absorption near its resonant frequency, but its sound absorption bandwidth is relatively narrow. In order to broaden the sound absorption bandwidth, multi-cavity acoustic liners composed of Helmholtz resonators of different depths connected in parallel have been developed in this field.

[0004] However, acoustic liners still need to broaden their sound absorption frequency band and improve their sound absorption capacity; moreover, the thickness of acoustic liners is still relatively large, making it difficult to meet the new requirements for lightweight and thin design; in view of this, this application provides a new acoustic liner, a power propulsion system and its design method to meet at least one or a combination of the above technical requirements. Summary of the Invention

[0005] The first aspect of this application aims to provide a sound liner.

[0006] The second aspect of this application aims to provide a power propulsion system.

[0007] The third aspect of this application aims to provide a design method for acoustic liner.

[0008] According to the first aspect of this application, the acoustic liner includes a perforated plate, a cavity structure, and a back plate; the perforated plate has through holes; the cavity structure includes multiple pipes; the perforated plate and the back plate are respectively connected to opposite sides of the cavity structure, such that the perforated plate, the cavity structure, and the back plate together form multiple cavities that are open at the top and closed at the bottom; wherein, the perforated plate includes a plate body and multiple thickened portions, the thickened portions extending from the plate body along the thickness direction into the interior of the multiple pipes, and the thickened portions are fitted to the pipes, such that the depth of the cavity is defined by the thickened portions and the back plate; and, portions of the perforated plate, the pipes, and the back plate that together form a single cavity provide a single sound-absorbing structural unit, wherein the thickness of the thickened portions of at least two of the sound-absorbing structural units is different.

[0009] Traditional acoustic liners use perforated plates of uniform thickness, with each sound-absorbing structural unit corresponding to a perforated plate of equal thickness. In contrast, the acoustic liner provided in this application increases the thickness of the perforated plate corresponding to each sound-absorbing structural unit through thickening sections. This increases the mass modulus of the sound-absorbing structural unit, shifting the resonant frequency towards lower frequencies, thereby improving the low-frequency sound absorption capability of the acoustic liner. By appropriately setting the thickening sections, the thickness of the perforated plate of each sound-absorbing structural unit can be adjusted individually, thus regulating the mass modulus of each unit and improving the broadband sound absorption performance of the acoustic liner. Furthermore, by parallel coupling of sound-absorbing structural units with thickening sections of different thicknesses, multiple... The sound absorption frequency peak is widened by increasing the sound absorption frequency band. According to the matching relationship between the perforated plate thickness and the cavity depth, the appropriately increased perforated plate thickness is compatible with the significantly reduced cavity depth. The thickening part in the pipe increases both the perforated plate thickness and the cavity depth, which helps to limit the overall thickness of the sound liner. Moreover, compared with the traditional sound liners described above, the sound liner provided in this application is suitable for increasing the perforated plate thickness of each sound absorption structural unit through the design of the thickening part, without having to thicken the perforated plate as a whole, thus saving materials and reducing weight.

[0010] In some embodiments, the plate is flat; the pipes extend in the thickness direction, and at least two of the pipes have different thicknesses; the back plate has walls extending at different positions in the thickness direction to correspondingly connect the cavity structure.

[0011] In some embodiments, at least one of the sound-absorbing structural units satisfies the following relationship:

[0012] ;

[0013] in, The depth of the cavity in the sound-absorbing structural unit. The thickness of the perforated plate in the sound-absorbing structural unit is given. The sound wave number at the resonant frequency of the sound-absorbing structural unit is... This is the mass end correction coefficient for the sound-absorbing structural unit. The aperture of the through hole in the sound-absorbing structural unit is [the diameter of the hole]. The perforation rate is the percentage of the perforated plate portion of the sound-absorbing structural unit.

[0014] In some embodiments, the perforation rate of the perforated plate portion of the sound-absorbing structural unit The value range is 1% to 30%, and the quality end correction coefficient is... Satisfying the relation:

[0015] .

[0016] In some embodiments, the cross-sectional profile of the plate perpendicular to the thickness direction is square, with a side length greater than 0 mm and less than or equal to 1 / 2 of the wavelength of the sound wave at the highest target sound absorption frequency.

[0017] In some embodiments, at least one of the perforated plates of the sound-absorbing structural unit does not include the thickened portion.

[0018] In some embodiments, the cross-sectional profiles of the thickened portions of at least two of the sound-absorbing structural units are different; and / or, the depths of the cavities of at least two of the sound-absorbing structural units are different; and / or, the perforation rates of the perforated plate portions of at least two of the sound-absorbing structural units are different; and / or, the apertures of the through holes of at least two of the sound-absorbing structural units are different; and / or, the shapes of the through holes of at least two of the sound-absorbing structural units are different.

[0019] In some embodiments, the thickness of the thickened portion is greater than 0 mm and less than or equal to 10 mm; and / or, the diameter of the through hole is greater than 0 mm and less than or equal to 3 mm; and / or, the wall thickness of the pipe is greater than or equal to 0.7 mm and less than or equal to 2 mm.

[0020] The power propulsion system according to the second aspect of this application includes an acoustic liner as described in the first aspect.

[0021] According to the design method of the acoustic liner according to the third aspect of this application, which is used to design the acoustic liner as described in the first aspect, it includes: designing the perforated plate to provide the thickened portion. Attached Figure Description

[0022] The above and other features, properties, and advantages of this application will become more apparent from the following description taken in conjunction with the accompanying drawings and embodiments, in which the same reference numerals always denote the same features. It should be noted that these drawings are merely illustrative and are not drawn to scale, and should not be construed as limiting the scope of protection actually claimed by this application, wherein:

[0023] Figure 1 This is a schematic diagram of the structure of a power propulsion system and acoustic liner according to one embodiment.

[0024] Figure 2 This is a schematic diagram of the structure of a perforated plate for an acoustic liner according to one embodiment.

[0025] Figure 3 This is another structural schematic diagram of the perforated plate of the acoustic liner according to one embodiment.

[0026] Figure 4 This is a schematic diagram of the cavity structure of a sound liner according to one embodiment.

[0027] Figure 5This is another schematic diagram of the cavity structure of the acoustic liner according to one embodiment.

[0028] Figure 6 This is a schematic diagram of the sound-absorbing structural unit of the acoustic liner according to one embodiment.

[0029] Figure 7 This is a flowchart illustrating a design method of one embodiment.

[0030] Explanation of reference numerals in the attached figures:

[0031] 1. Acoustic liner; 2. Power propulsion system; 10. Perforated plate; 11. Plate body; 12. Thickened part; 13. Through hole; 20. Cavity structure; 21. Pipe; 30. Back plate; 40. Sound-absorbing structural unit; 41. Cavity. Detailed Implementation

[0032] Reference will now be made in detail to various embodiments of this application, examples of which are shown in the accompanying drawings and described below. Although this application will be described in conjunction with exemplary embodiments, it should be understood that this application is not intended to be limited to those exemplary embodiments. Rather, this application is intended to cover not only these exemplary embodiments, but also various alternatives, modifications, equivalents, and other embodiments that may be included within the spirit and scope of this application as defined by the appended claims.

[0033] This application uses specific terms to describe embodiments of the application. For example, "an embodiment" and / or "one embodiment" refers to a feature, structure, or characteristic associated with at least one embodiment of the application. Therefore, it should be emphasized and noted that "an embodiment" or "one embodiment" mentioned twice or more in different locations in this application does not necessarily refer to the same embodiment. Furthermore, certain features, structures, or characteristics in one or more embodiments of the application can be appropriately combined. In the following description, the orientation or positional relationship indicated by terms such as "upper," "lower," "inner," "outer," "front," "rear," or other directional terms is based on the orientation or positional relationship shown in the accompanying drawings and is only for the convenience of describing the application and simplifying the description, and does not indicate or imply that the device or component referred to must have a specific orientation, be constructed and / or implemented in a specific orientation, and therefore should not be construed as a limitation of the application. In this application, the terms "first," "second," etc., are only used for distinguishing descriptions and should not be construed as indicating or implying positional relationships or order of importance. In the following description, unless otherwise expressly specified or limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly; for example, they can refer to fixed connections or movable connections; they can refer to direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0034] This application uses flowcharts to illustrate the operations performed according to embodiments of this application. It should be understood that, depending on the actual situation, the steps shown in the diagrams are not necessarily performed sequentially, and other operations may be added to these processes, or one or more steps may be removed from these processes.

[0035] It is understood that the acoustic liner, propulsion system and design method provided in this application are particularly applicable to civil aircraft engines, and can also be applied to other applicable occasions, such as auxiliary power systems for civil aircraft, gas turbines for fixed sites, etc., without limitation.

[0036] like Figures 1 to 6 The acoustic liner 1 shown includes a perforated plate 10, a cavity structure 20, and a back plate 30. The perforated plate 10 has through holes 13; the cavity structure 20 includes multiple pipes 21; the perforated plate 10 and the back plate 30 are respectively connected to opposite sides of the cavity structure 20, thus the perforated plate 10, the cavity structure 20, and the back plate 30 together form multiple mutually spaced cavities 41 that are open at the top and closed at the bottom. In other words, the perforated plate 10 and the back plate 30 are respectively connected to the opposite ends of each pipe 21, thus the perforated plate 10, the individual pipe 21, and the back plate 30 form a single cavity 41; the through holes 13 of the perforated plate 10 connect the interior and exterior of the cavity 41, forming an opening at the top of the cavity 41, and the back plate 30 connects to the pipes 21, thus closing the bottom of the cavity 41. The perforated plate 10 includes a plate body 11 and a plurality of thickened portions 12. The thickened portions 12 extend from the plate body 11 along the thickness direction, and each thickened portion 12 corresponds to a single pipe 21 of the cavity structure 20. A through hole 13 passes through the plate body 11 and the thickened portions 12 to connect the interior and exterior of the cavity 41. The plurality of thickened portions 12 extend into the interior of the plurality of pipes 21, and the wall surface of the thickened portion 12 conforms to the wall surface of the pipe 21 to achieve a tight fit. Thus, the depth of the cavity 41 is defined by the thickened portions 12 and the back plate 30. Figure 6 As shown. Furthermore, the portion of the perforated plate 10 that together forms a single cavity 41, the portion of the duct 21 and the portion of the back plate 30 provide a single sound-absorbing structural unit 40, and the thickness of the thickened portion 12 of at least two sound-absorbing structural units 40 is different.

[0037] The design of the thickened part 12, and the configuration of at least two sound-absorbing structural units 40 with different thicknesses of the thickened part 12, is beneficial to improving the low-frequency sound absorption capability of the acoustic liner 1 and widening the sound absorption frequency band. Specifically, it can be understood that a single sound-absorbing structural unit 40 is approximately equivalent to a single Helmholtz resonant cavity, while the entire acoustic liner 1 is approximately equivalent to a multi-cavity structure with multiple Helmholtz resonant cavities coupled in parallel.

[0038] For a single Helmholtz resonator, the acoustic impedance formula is:

[0039] (1)

[0040] (2)

[0041] , (3)

[0042] , (4)

[0043] in, To normalize the acoustic impedance, To normalize the acoustic impedance, For normalized sound resistance, For quality resistance, For volume resistance, For sound wave number, For the thickness of the perforated plate, This is a correction factor for the quality side. The aperture of the perforated plate. The perforation rate of the perforated plate. This refers to the depth of the cavity (or cavity depth). For imaginary numbers; and, For the density of the medium, The speed of sound in the medium is usually given based on the actual situation.

[0044] The formula for the sound absorption coefficient is:

[0045] (5)

[0046] in, The sound absorption coefficient is... Let X be the normalized acoustic impedance and X be the normalized acoustic impedance.

[0047] From formulas (1) to (5), it can be seen that the acoustic impedance and acoustic impedance of a Helmholtz resonator depend on the perforation rate. Perforated plate thickness Aperture Cavity depth Structural parameters; A Helmholtz resonator typically reaches its peak absorption coefficient at only one frequency, which is its resonant frequency;

[0048] For a multi-cavity structure formed by multiple Helmholtz resonators coupled in parallel, the formula for the parallel acoustic impedance is:

[0049] (6)

[0050] in, The total area of ​​the multi-cavity structure. The acoustic impedance of a multi-cavity structure, Let be the area of ​​each Helmholtz resonator. Let be the acoustic impedance of each Helmholtz resonator.

[0051] As can be seen from formula (6), by connecting different Helmholtz resonators in parallel and appropriately setting the acoustic impedance of each Helmholtz resonator, the acoustic impedance of the multi-cavity structure can approach 1 and the acoustic impedance can approach 0 in a wide frequency range. Thus, the multi-cavity structure has a better sound absorption coefficient in a wide frequency range, achieving a wideband noise reduction effect.

[0052] Traditional acoustic liners use perforated plates of uniform thickness, meaning the perforated plate only has a flat surface; the thickness of the perforated plate corresponding to each sound-absorbing structural unit is equal to the thickness of the plate surface. However, the acoustic liner 1 provided in this application has a perforated plate 10 comprising a plate body 11 and a thickened portion 12. The thickness t of the perforated plate includes two parts: the thickness t1 of the plate body 11 and the thickness t2 of the thickened portion 12, as shown below. Figure 6 As shown. Compared to traditional acoustic liners, the thickened portion 12 increases the thickness of the perforated plate of the sound-absorbing structural unit 40, increases its mass modulus, and shifts the resonant frequency towards lower frequencies, thereby improving the low-frequency sound absorption capability of the sound-absorbing structural unit 40 and the acoustic liner 1 as a whole. Furthermore, by setting the thickness of the thickened portion 12, the thickness of the perforated plate of each sound-absorbing structural unit 40 can be adjusted individually, thereby adjusting the mass modulus of each sound-absorbing structural unit 40 to improve the broadband sound absorption performance of the acoustic liner 1. By parallel coupling of sound-absorbing structural units 40 with thickened portions 12 of different thicknesses, multiple sound absorption frequency peaks are provided to broaden the sound absorption frequency band.

[0053] From formulas (3) and (4), it can be derived that, for a single Helmholtz resonant cavity, the matching relationship between the perforated plate thickness and the cavity depth at the resonant frequency is:

[0054] (7)

[0055] in, Because of the depth of the cavity, For sound wave number, For the thickness of the perforated plate, The aperture of the perforated plate. The perforation rate of the perforated plate. This is the quality correction factor.

[0056] As can be seen from formula (7), under the condition that the absolute values ​​of mass resistance and volume resistance are equal, the appropriately increased perforated plate thickness is compatible with the significantly reduced cavity depth. Therefore, using a larger perforated plate thickness can significantly reduce the overall thickness of the acoustic liner. If a larger perforated plate thickness is provided with a traditional acoustic liner, the perforated plate (plate body) needs to be thickened as a whole. However, by setting a thickening part 12 in the pipe 21, the thickness of the perforated plate 10 is increased and the depth of the cavity 41 is reduced. It is not necessary to thicken the perforated plate 10 (plate body 11) as a whole, which is beneficial to save materials and reduce weight.

[0057] In some embodiments, the acoustic liner 1 is configured as a meta-structure liner. A meta-structure liner is an artificial structure based on acoustic metamaterials technology. By periodically or non-periodically arranging structural units with subwavelength scales, it achieves sound absorption characteristics that are difficult to achieve with conventional acoustic liners, making it particularly suitable for applications with high limitations on installation space and weight. Specifically, at the subwavelength scale, the area of ​​the acoustic liner 1 is negligible, and it can be periodically arrayed to form a two-dimensional material laid on the surface of the application object to suppress noise.

[0058] like Figures 1 to 5 As shown, in some embodiments, the plate 11 is flat to reduce the impact on the working performance of the surface of the application object; the pipes 21 extend in the thickness direction, and at least two pipes 21 have different thicknesses; the back plate 30 has walls extending at different positions in the thickness direction to correspondingly connect the cavity structure 20. In short, the cavity structure 20 of the acoustic liner 1 includes pipes 21 of different thicknesses, and the back plate 30 adopts a (non-flat) stepped structure to accommodate pipes 21 of different thicknesses, such as... Figure 5 As shown. It can be understood that although the bottom of the acoustic liner 1 is not flat, it can still be laid on the surface of the application object, such as the surface of the flow channel of an aero-engine, through appropriate connection methods, such as bonding and riveting.

[0059] Single-degree-of-freedom acoustic liners have all tubes of uniform thickness and a flat backing plate. Double-degree-of-freedom acoustic liners also maintain uniformly thick tubes, with acoustic diaphragms installed inside. Because these traditional acoustic liners have uniform resonant cavity depths, they naturally form a structural design with uniform tube thickness, resulting in an acoustic liner designed as a flat panel with perforated plates and a uniform thickness for the central cavity structure. Deeply influenced by traditional design concepts, multi-cavity parallel-coupled acoustic liners are also designed with uniformly thick tubes. However, this design leads to redundancy in the parallel coupling of multiple cavities in the acoustic liner structure, which is not conducive to reducing volume and weight. This is because parallel coupling of multiple cavities typically requires cavities of varying depths to achieve broadband sound absorption. To ensure low-frequency absorption, cavities with relatively large depths are needed, thus requiring a relatively thicker duct. Conversely, to ensure high-frequency absorption, some cavities with relatively small depths are required. If a uniform thickness design is used, baffles must be installed in some ducts to separate cavities with relatively small depths, making other parts of the duct redundant and increasing material and weight. Therefore, by limiting the overall thickness of the acoustic liner 1 through the thickened section 12, and by using a stepped backplate 30 to remove the structural constraints on the thickness of the duct 21, redundancy can be reduced, and volume and weight can be decreased.

[0060] In some embodiments, at least one sound-absorbing structural unit 40 approximately satisfies the following relationship:

[0061] ;

[0062] in, The depth of the cavity in the sound-absorbing structural unit. The thickness of the perforated plate in the sound-absorbing structural unit. The sound wave number at the resonant frequency of the sound-absorbing structural unit. This is the mass end correction coefficient for the sound-absorbing structural unit. The aperture of the through-hole in the sound-absorbing structural unit is [value]. The perforation rate is the percentage of the perforated plate portion of the sound-absorbing structural unit. This design ensures that the resonant frequencies of the perforated plate 10 and the cavity 41 are the same or similar, which helps to guarantee the sound absorption capacity. It can be understood that, furthermore, by appropriately setting the thickness of the thickened portion 12 and the duct 21 of each sound-absorbing structural unit 40, each sound-absorbing structural unit 40 can satisfy this relationship.

[0063] Specifically, in some embodiments, the perforation rate σ of the perforated plate 10 portion of the sound-absorbing structural unit 40 ranges from 1% to 30%, and the mass-end correction coefficient ε satisfies the following relationship:

[0064] ;

[0065] The sound wave number k of the sound-absorbing structural unit 40 at the resonant frequency can be determined according to actual needs and objectives, which will not be elaborated here.

[0066] like Figure 3 , Figure 4 As shown, in some embodiments, the cross-sectional profile of the pipe 21 and the thickened portion 12 perpendicular to the thickness direction is rectangular. The cross-sectional profile of the plate 11 perpendicular to the thickness direction is square, with a side length greater than 0 mm and less than or equal to 1 / 2 of the wavelength of the sound wave at the highest target sound absorption frequency. The highest target sound absorption frequency mentioned here refers to the upper limit of the frequency range at which the acoustic liner 1 is expected to operate effectively, which can be determined according to actual needs; for example, in some embodiments, the acoustic liner 1 is configured to operate effectively in the frequency range of 800 Hz to 5000 Hz to maintain a sound absorption coefficient of 0.85 or higher. Using a square plate 11 with a side length less than or equal to 1 / 2 of the wavelength of the sound wave at the highest target sound absorption frequency can ensure the uniformity of the acoustic impedance on the surface of the acoustic liner 1, thereby configuring the acoustic liner 1 as a locally reactive acoustic liner to ensure the sound absorption effect.

[0067] like Figure 3 As shown, in some embodiments, the perforated plate 10 of at least one sound-absorbing structural unit 40 does not include the thickened portion 12, that is, it only includes the portion of the plate body 11, which is beneficial to broaden the sound absorption frequency band.

[0068] like Figures 2 to 4 As shown, in some embodiments, the cross-sectional profiles of the thickened portions 12 of at least two sound-absorbing structural units 40 are different, for example, they have different shapes and areas; and / or, the depths of the cavities 41 of at least two sound-absorbing structural units 40 are different; and / or, the perforation rates of the perforated plates 10 portions of at least two sound-absorbing structural units 40 are different; and / or, the apertures of the through holes 13 of at least two sound-absorbing structural units 40 are different; and / or, the shapes of the through holes 13 of at least two sound-absorbing structural units 40 are different, for example, they are circular holes, or non-circular holes, such as polygons such as rectangles, ellipses, etc.; the aperture of a circular hole is its diameter; the aperture of a non-circular hole refers to its acoustic equivalent diameter, or is close to its maximum profile size. This design further enhances the coupling effect between various sound-absorbing structural units 40 by setting different structural parameters, and utilizes the acoustic siphon effect to improve the broadband sound absorption performance of the acoustic liner 1.

[0069] In some embodiments, the thickness of the thickened portion 12 is greater than 0 mm and less than or equal to 10 mm, so as to avoid the thickened portion 12 being too thick and unfavorably increasing the weight.

[0070] In some embodiments, the aperture of the through hole 13 is greater than 0 mm and less than or equal to 3 mm; the aperture should not be too large in order to avoid the fluid interacting with the through hole 13 and adversely generating resistance, and to avoid generating secondary sound sources and weakening the sound absorption performance.

[0071] In some embodiments, the wall thickness of the pipe 21 is greater than or equal to 0.7 mm and less than or equal to 2 mm to avoid difficulties in processing due to insufficient wall thickness, or unfavorable weight increase due to excessive wall thickness.

[0072] like Figure 1 As shown, this application also provides a power propulsion system 2, such as an aero engine, an auxiliary power system of an aircraft, or other gas turbines, which includes an acoustic liner 1 for noise control of structures such as flow channels.

[0073] like Figure 7 As shown, this application also provides a design method for an acoustic liner 1, which includes designing a perforated plate 10 to provide a thickening portion 12.

[0074] In some embodiments, the design method specifically includes:

[0075] S1. Determine the design objectives based on the actual situation, including the expected sound absorption frequency range (the range of sound wave number k) for the effective operation of the acoustic liner 1 and the sound absorption coefficient (the target sound absorption coefficient corresponding to each sound wave number k) required to achieve effective operation.

[0076] S2. Set the range of values ​​for structural parameters (including the thickness of the perforated plate, the diameter of the hole, the perforation rate, and the cavity depth of each sound-absorbing structural unit 40), combine the formulas (1) to (6) introduced above, perform optimization calculations on the structural parameters, and obtain the structural parameters of each sound-absorbing structural unit 40 that meet the design objectives.

[0077] S3. Based on the structural parameters of each sound-absorbing structural unit 40, a perforated plate 10 is set to provide a thickened portion 12, a cavity structure 20 is set to provide a pipe 21 extending in the thickness direction, and a stepped back plate 30 is set to seal the cavity 41.

[0078] The design method described above is conducive to achieving wideband and high-efficiency sound absorption, and significantly reduces the thickness and weight of the sound liner 1.

[0079] In summary, the beneficial technical effects of this application include, but are not limited to, at least one of the following:

[0080] Traditional acoustic liners use perforated plates of uniform thickness, with each sound-absorbing structural unit corresponding to a perforated plate of equal thickness. In contrast, the acoustic liner provided in this application increases the thickness of the perforated plate corresponding to each sound-absorbing structural unit through thickening sections. This increases the mass modulus of the sound-absorbing structural unit, shifting the resonant frequency towards lower frequencies, thereby improving the low-frequency sound absorption capability of the acoustic liner. By appropriately setting the thickening sections, the thickness of the perforated plate of each sound-absorbing structural unit can be adjusted individually, thus regulating the mass modulus of each unit and improving the broadband sound absorption performance of the acoustic liner. By parallel coupling of sound-absorbing structural units with thickening sections of different thicknesses, it provides… Multiple sound absorption frequency peaks are used to broaden the sound absorption frequency band. According to the matching relationship between the perforated plate thickness and the cavity depth, an appropriately increased perforated plate thickness is compatible with a significantly reduced cavity depth. A thickening section is provided in the pipe to both increase the perforated plate thickness and reduce the cavity depth, which is beneficial to limiting the overall thickness of the acoustic liner. Furthermore, compared with the traditional acoustic liners described above, the acoustic liner provided in this application is suitable for increasing the perforated plate thickness of each sound absorption structural unit through the design of the thickening section, without having to thicken the perforated plate as a whole, thus saving materials and reducing weight.

[0081] While this application discloses preferred embodiments as described above, it is not intended to limit the scope of this application. Any changes and modifications can be made by those skilled in the art without departing from the spirit and scope of this application. Therefore, any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application, without departing from the content of the technical solution of this application, fall within the protection scope defined by the claims of this application.

Claims

1. A sound liner, characterized in that, Includes perforated plate, cavity structure and back plate; The perforated plate has through holes; the cavity structure includes multiple pipes; the perforated plate and the back plate are respectively connected to opposite sides of the cavity structure, so that the perforated plate, the cavity structure, and the back plate together form multiple cavities that are open at the top and closed at the bottom; wherein... The perforated plate includes a plate body and multiple thickened portions. The thickened portions extend from the plate body along the thickness direction into the interior of the multiple pipes, and are fitted to the pipes. Thus, the depth of the cavity is defined by the thickened portions and the back plate. A portion of the perforated plate, the duct, and the back plate that together form a single cavity provide a single sound-absorbing structural unit, and the thickness of the thickened portions of at least two of the sound-absorbing structural units is different.

2. The acoustic liner according to claim 1, characterized in that, The plate is flat; the pipes extend in the thickness direction, and at least two of the pipes have different thicknesses; the back plate has walls extending at different positions in the thickness direction to correspondingly connect the cavity structure.

3. The acoustic liner according to claim 1, characterized in that, At least one of the sound-absorbing structural units satisfies the following relationship: ； in, The depth of the cavity in the sound-absorbing structural unit. The thickness of the perforated plate in the sound-absorbing structural unit is given. The sound wave number at the resonant frequency of the sound-absorbing structural unit is... This is the mass end correction coefficient for the sound-absorbing structural unit. The aperture of the through hole in the sound-absorbing structural unit is [the diameter of the hole]. The perforation rate is the percentage of the perforated plate portion of the sound-absorbing structural unit.

4. The acoustic liner according to claim 3, characterized in that, The perforation rate of the perforated plate portion of the sound-absorbing structural unit The value range is 1% to 30%, and the quality end correction coefficient is... Satisfying the relation: 。 5. The acoustic liner according to claim 1, characterized in that, The cross-sectional profile of the plate perpendicular to the thickness direction is square, with a side length greater than 0 mm and less than or equal to 1 / 2 of the wavelength of the sound wave at the highest target sound absorption frequency.

6. The acoustic liner according to claim 1, characterized in that, At least one of the perforated plates of the sound-absorbing structural unit does not include the thickened portion.

7. The acoustic liner according to claim 1, characterized in that: At least two of the sound-absorbing structural units have different cross-sectional profiles in the thickened portions; and / or, The cavities of at least two of the sound-absorbing structural units have different depths; And / or, At least two of the sound-absorbing structural units have different perforation rates in portions of the perforated plates; and / or, At least two of the sound-absorbing structural units have different apertures for their through holes; and / or, The through-holes of at least two of the sound-absorbing structural units have different shapes.

8. The acoustic liner according to claim 1, characterized in that: The thickness of the thickened portion is greater than 0 mm and less than or equal to 10 mm; and / or, The diameter of the through hole is greater than 0 mm and less than or equal to 3 mm; and / or, The wall thickness of the pipe is greater than or equal to 0.7 mm and less than or equal to 2 mm.

9. A power propulsion system, characterized in that, Includes the acoustic liner as described in any one of claims 1 to 8.

10. A method for designing a sound liner, characterized in that, For designing an acoustic liner as described in any one of claims 1 to 8, the method includes: designing the perforated plate to provide the thickened portion.

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