Sound absorption and noise reduction composite structure of aero-engine

Abstract

The invention relates to the field of aviation equipment, in particular to the technical field of sound absorption composite structures for noise control of aero-engines. The sound absorption and noise reduction composite structure of the aero-engine comprises a back plate (1); the honeycomb core (2) is different from a traditional regular hexagonal honeycomb core and is composed of semi-concave hexagonal honeycombs. The position, close to the back plate, of the honeycomb core is filled with porous sound absorption material graphene sponge, three-section equal-height filling is carried out according to density gradient change, and the filling height of each section is one fourth of the height of the honeycomb core; and the perforated plate (4) is bonded with the honeycomb core through an adhesive film. The problems that a traditional regular hexagonal honeycomb core is prone to saddle type deformation during curved surface integral forming, so that the honeycomb core deforms, and the mechanical impact resistance is poor are solved and improved, and meanwhile the sound absorption performance of the composite structure is further improved through the porous sound absorption materials filled in the honeycomb core in a gradient mode; and the sound absorption and noise reduction frequency band width of the whole composite structure is expanded.

Description

Technical Field

[0001] The present invention relates to the use of aviation equipment, and in particular to the technical field of sound-absorbing composite structures for controlling noise of aviation engines. Background Art

[0002] Aircraft engine fan noise is the main source of aircraft noise, which can be controlled by placing acoustic lining structures at engine inlets, walls and other locations. Traditional acoustic lining mainly adopts a micro-perforated plate-honeycomb cavity-backboard structure, which is a single-degree-of-freedom acoustic lining, as well as the double-degree-of-freedom acoustic lining and even three-degree-of-freedom acoustic lining developed from it. The principle is to use Helmholtz resonance to absorb single-frequency noise. However, this type of traditional acoustic lining structure is limited by factors such as limited perforation rate, acoustic lining structural strength, and fixed structural resonance frequency, resulting in a narrow frequency range of sound absorption and noise reduction for this type of acoustic lining. Although double-degree-of-freedom and three-degree-of-freedom acoustic linings can increase the frequency range of sound absorption and noise reduction to a certain extent, they also increase the weight and size of the acoustic lining. In addition, since the honeycomb core of the traditional acoustic lining structure is composed of regular hexagonal honeycombs with a positive Poisson's ratio, saddle-shaped deformation is prone to occur during the manufacturing process of curved integrated molding, thereby affecting the overall acoustic performance and structural strength of the acoustic lining, especially for acoustic linings used in the nacelles of small business jets with small diameters, this problem is more likely to occur. Summary of the invention

[0003] In view of the deficiencies of the prior art described in the above background technology, the present invention aims to provide an aircraft engine sound absorption and noise reduction composite structure, which combines a gradient-filled porous sound-absorbing material to broaden the spectrum range of sound absorption and noise reduction, and at the same time improves the overall structural strength of the composite structure and maintains its stable acoustic performance through a semi-concave hexagonal honeycomb structure.

[0004] The technical solution of the present invention is as follows:

[0005] Provided is an aircraft engine sound absorption and noise reduction composite structure, comprising a back plate, the back plate is used to provide an acoustic hard wall environment; a honeycomb core, the honeycomb core is composed of semi-concave hexagonal honeycombs, and the honeycomb core is fixedly connected to one side of the back plate; a porous sound absorbing material, the porous sound absorbing material is filled in the honeycomb core in three sections close to the back plate according to a gradient with gradually decreasing density, the filling thickness of the three sections remains consistent at one quarter of the height of the honeycomb core, and the total filling height is three quarters of the height of the honeycomb core; a perforated plate, the surface of the perforated plate is perforated, and one side of the perforated plate is fixedly connected to the other side of the honeycomb core.

[0006] Furthermore, the perforations on the surface of the perforated plate are circular, approximately every three circular holes correspond to a single hole in the honeycomb core, and the area of ​​the circular hole is approximately 3-4% of the area of ​​the single hole in the honeycomb core.

[0007] Furthermore, the thickness of the perforated plate is less than or equal to 1 mm.

[0008] Furthermore, the perforated plate is composed of fibers interwoven with each other, and the fibers are pre-impregnated with thermoplastic resin, and the warp or weft direction of the fibers is the same as the airflow direction of the aircraft engine inlet duct.

[0009] Furthermore, the honeycomb core is made of NOMEX.

[0010] Furthermore, the honeycomb core is composed of semi-concave hexagons, and each honeycomb hole shares edges with other six adjacent honeycomb holes.

[0011] Furthermore, the porous sound-absorbing material is composed of graphene sponge.

[0012] Furthermore, the porous sound absorbing material is filled in the honeycomb core in a gradient from high to low density near the back plate, and the porous sound absorbing material near the back plate has the highest density, and the density is preferably 9 mg / cm 3 , 4mg / cm 3 and 2mg / cm 3 .

[0013] Furthermore, the porous sound absorbing material is filled in three sections according to the density from large to small, the filling height of each section is one quarter of the height of the honeycomb core, and the porous sound absorbing material is connected to the back plate.

[0014] Furthermore, the back panel is made of interwoven fibers, and the fibers are pre-impregnated with thermoplastic resin, and the warp or weft direction of the fibers is the same as the airflow direction of the aircraft engine inlet duct.

[0015] Furthermore, the thickness of the back plate is less than or equal to 0.5 mm.

[0016] The beneficial effects of the present invention are as follows:

[0017] (1) The aircraft engine sound absorption and noise reduction composite structure of the present invention is a porous sound absorption material filled perforated plate-honeycomb composite structure. The porous material is filled in the honeycomb core according to the density gradient, and a gap is left in the honeycomb core cavity, which is at a certain distance from the perforated plate. The porous sound absorption material, as a porous material with a gradient change in flow resistivity, greatly improves the absorption capacity of high-frequency noise, which helps to ensure that the aircraft engine sound absorption and noise reduction composite structure has a high sound absorption coefficient at the target single-tone noise frequency, while broadening the sound absorption frequency range of the overall composite structure.

[0018] (2) The honeycomb core is composed of semi-concave hexagonal honeycombs, which is a zero Poisson structure. Compared with the regular hexagonal honeycombs used in traditional sound lining structures, it has better in-plane mechanical properties and can avoid the saddle-shaped deformation caused by the regular hexagonal honeycomb structure under bending stress. The concave hexagonal honeycomb configuration of the honeycomb core can suppress the Poisson's ratio effect in the non-deformation direction, avoid the distortion of the honeycomb core unit structure, ensure the stability of the acoustic performance, and provide the perforated plate with sufficient out-of-plane stiffness to carry the aerodynamic load.

[0019] (3) The aircraft engine sound absorption and noise reduction composite structural material obtained by the method of the present invention can adjust the frequency corresponding to the sound absorption peak, the average sound absorption coefficient and the sound absorption frequency range within a wide frequency range by changing the density gradient and filling height H-h1 of the porous sound absorption material, the perforation diameter d of the perforated plate and the thickness t of the perforated plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of the present application, and do not constitute an improper limitation of the present invention. In the drawings:

[0021] Figure 1 A schematic diagram of the installation position of the aircraft engine sound absorption and noise reduction composite structure provided according to an embodiment of the present invention;

[0022] Figure 2 A schematic diagram of a composite structure for sound absorption and noise reduction of an aircraft engine provided according to an embodiment of the present invention;

[0023] Figure 3 A schematic diagram of the perforated plate structure in the aircraft engine sound absorption and noise reduction composite structure provided according to an embodiment of the present invention;

[0024] Figure 4 A schematic diagram showing a comparison of deformation characteristics of a semi-concave hexagonal honeycomb core in an aircraft engine sound absorption and noise reduction composite structure provided according to an embodiment of the present invention and a regular hexagonal honeycomb core in a traditional sound liner structure under bending stress;

[0025] Figure 5 It is a schematic partial cross-sectional view of an aircraft engine sound absorption and noise reduction composite structure provided according to an embodiment of the present invention.

[0026] The reference numerals in the accompanying drawings are described as follows:

[0027] 1- Back panel;

[0028] 2- Honeycomb core;

[0029] 3-Porous sound absorbing material;

[0030] 4- Perforated plate;

[0031] 5-Circular holes in the perforated plate;

[0032] 6- The third section is porous sound absorbing material, with the lowest density;

[0033] 7-Second section of porous sound absorbing material, with medium density;

[0034] 8-The first section of porous sound-absorbing material has the highest density;

[0035] 9-Aerospace engine sound absorption and noise reduction composite structure. DETAILED DESCRIPTION

[0036] The present invention is described in detail below according to the accompanying drawings and preferred embodiments, and the purpose and effect of the present invention will become more clear. It should be understood that the specific embodiment described herein is an embodiment of the present invention, not all embodiments, and is only used to explain the present invention, not to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. In the drawings, the same symbols throughout represent the same elements.

[0037] In the description of the present invention, it should be understood that the terms "left", "right", "upper", "lower", "near", "inner" and the like indicating directions or positional relationships are based on the convenience of describing the present invention only, and do not indicate that the elements or structures referred to must have a specific direction, be constructed and installed in a specific direction, and therefore cannot be understood as limiting the scope of protection of the present invention.

[0038] In order to overcome the shortcomings of the existing sound liner, such as the narrow sound absorption frequency range and the easy deformation of the honeycomb core structure during the curved surface integral molding, the present invention provides an aircraft engine sound absorption and noise reduction composite structure, which not only achieves a wider sound absorption frequency range, but also can ensure that the manufacturing process of the curved surface integral molding does not have saddle-shaped deformation, thereby ensuring the low flow resistance and structural strength of the inner wall of the pipeline of the overall composite structure under high-speed airflow and stable and uniform acoustic performance.

[0039] like Figure 1 As shown, an aircraft engine sound absorption and noise reduction composite structure (9) provided by an embodiment of the present invention is arranged on the inner surface of the aircraft engine nacelle air inlet and outer duct, and the back plate (4), porous sound absorption material (3), honeycomb core (2) and perforated plate (1) can form an arc columnar acoustic bushing together. Specifically comprising: Figure 2As shown, a back plate (1), the back plate (1) is used to provide an acoustic hard wall environment; a honeycomb core (2), the honeycomb core is composed of a semi-concave hexagonal honeycomb, and the honeycomb core is fixedly connected to one side of the back plate; a porous sound absorbing material (3), the porous sound absorbing material is close to the back plate (1) and is filled in the honeycomb core (2) in three sections with a gradually decreasing density, the three sections of filling thickness remain the same as one quarter of the height of the honeycomb core (2), and the total filling height is three quarters of the height of the honeycomb core (2); a perforated plate (4), the surface of the perforated plate (4) is perforated, and one side of the perforated plate (4) is fixedly connected to the other side of the honeycomb core (2). The perforated plate (4) is flush with the inner surface of the aircraft engine nacelle air inlet or the outer duct, thereby ensuring that it does not affect the intake airflow while being in full contact with the aircraft engine noise.

[0040] In this embodiment, the connection between the back plate (1) and the honeycomb core (2), the connection between the porous sound absorbing material and the back plate (1), and the connection between the honeycomb core (2) and the perforated plate (4) are all bonded. The porous sound absorbing material is filled in the honeycomb core (2) close to the back plate (1), leaving a gap between the porous sound absorbing material and the perforated plate (4).

[0041] In this embodiment, if Figure 3 As shown, the surface perforations of the perforated plate (4) are circular, and approximately every three circular holes correspond to a single hole of the honeycomb core (2), and the area of ​​the circular hole (5) is approximately 3-4% of the area of ​​the single hole of the honeycomb core. The diameter of the circular hole (5) can be set according to actual conditions. For example, in other alternative embodiments, the area of ​​the circular hole (5) is 3.5% of the area of ​​the single hole in the honeycomb core (2). Further, it can be understood that the area of ​​the circular hole (5) on the perforated plate (4) can be set to a non-integer percentage of the area of ​​the single hole of the honeycomb core (2), and the percentage is set between 3-4%. Moreover, the change in the area and number of the circular holes (5) can change the acoustic impedance of the composite structure. For example, increasing the number of the circular holes (5) on the perforated plate (4), that is, the perforation rate, can increase the acoustic impedance of the aircraft engine sound absorption and noise reduction composite structure (9) and improve the noise dissipation performance.

[0042] It is understood that the thickness of the perforated plate (4) is less than or equal to 1 mm. Furthermore, the perforated plate (4) may be 0.5 mm, 0.8 mm or 1 mm in some embodiments. The change in thickness of the perforated plate (2) may change the acoustic impedance of the aircraft engine sound absorption and noise reduction composite structure (9), thereby changing the sound absorption coefficient of the structure within the sound absorption frequency band.

[0043] In this embodiment, the perforated plate (2) is composed of fibers interwoven with each other, and the fibers are pre-impregnated with thermoplastic resin, and the warp or weft direction of the fibers is the same as the airflow direction of the aircraft engine air intake. Furthermore, the types of fibers used in the perforated plate (2) include any commonly used materials known in the art, such as carbon fiber, glass fiber, nylon and polyethylene fiber. In addition, the fiber material can be formed by any other suitable material known in the art, all of which are within the spirit and scope of the present disclosure. The aforementioned circular hole (5) is formed by machining after the fiber is solidified. The perforated plate (4) covers the entire aircraft engine sound absorption and noise reduction composite structure (9) and is in direct contact with the airflow.

[0044] In this embodiment, the honeycomb core is made of NOMEX. Furthermore, in other alternative embodiments, the honeycomb core (2) can be made of other materials, such as aluminum, carbon fiber honeycomb. In addition, the material of the honeycomb core (2) can be formed of any other suitable material known in the art, all of which are within the spirit and scope of the present disclosure. Furthermore, as Figure 4 As shown, the honeycomb core (2) is composed of semi-concave hexagonal honeycombs, wherein each honeycomb shares edges with six adjacent honeycombs. Changing the side length L, angle α and angle β of a single semi-concave hexagonal honeycomb topological configuration can affect the in-plane bending stiffness of the entire honeycomb core (2), thereby changing the overall structural strength. The arrangement configuration of the honeycomb core (2) is specifically shown in Figure 4 For a single semi-recessed hexagonal honeycomb, the left and right sides of a set of parallel sides are two semi-recessed hexagonal honeycombs "in the same direction" as itself, and the upper and lower sides are four semi-recessed hexagonal honeycombs "in the opposite direction" to itself. It can be understood that the semi-recessed hexagonal honeycomb core avoids the saddle-shaped deformation of the traditional regular hexagonal honeycomb core during manufacturing (see Figure 4 ), the symmetry of the parallel honeycomb structure is greatly guaranteed, which improves the structural strength of the entire composite structure and the stability and uniformity of the acoustic performance.

[0045] In this embodiment, the porous sound absorbing material (3) is composed of graphene sponge, which is filled in the honeycomb core (2) with a density gradient from high to low near the back plate (1), leaving a gap away from the perforated plate (2). The density of the porous sound absorbing material near the back plate is the highest, and the density is preferably 9 mg / cm 3 , 4mg / cm 3 and 2mg / cm 3 It should be understood that the three-stage gradient change value of the density of the porous sound-absorbing material (3) is not limited to 9 mg / cm 3 , 4mg / cm 3 and 2mg / cm 3 , can be other values, such as 9 mg / cm3 , 6mg / cm 3 and 3mg / cm 3 The gradient filling is to provide a porous sound-absorbing material with a gradually changing flow resistivity, which matches the air acoustic impedance as much as possible, so that the sound energy is gradually dissipated and absorbed by the porous sound-absorbing material after entering the honeycomb core (2) from the perforated plate (4). Further, as Figure 5 As shown, the porous sound absorbing material (3) is filled in three sections in descending order of density, and the filling height of each section is one-fourth of the height of the honeycomb core (2), and is bonded to the back plate (1). It is understandable that the filling height can be set according to actual conditions. For example, in other alternative embodiments, it can be filled to four-fifths of the height of the honeycomb core (2), and at the same time, the filling height of each section becomes four-fifteenths of the height of the honeycomb core (2).

[0046] In this embodiment, the gap between the porous sound absorbing material (3) and the perforated plate (4) is one quarter of the height of the honeycomb core (2), so as to allow the airflow to carry sound energy and fully enter the honeycomb core (2), ensuring that the porous sound absorbing material (3) filled in the honeycomb core (2) can fully exert its absorption effect on high-frequency noise, so that the composite structure (9) can achieve the noise reduction requirements in a wide sound absorption frequency band in a targeted manner, alleviating the defect of the narrow sound absorption frequency band of the traditional single-degree-of-freedom sound liner. It can be understood that the gap distance between the porous sound absorbing material (3) and the perforated plate (4) can be set according to actual conditions.

[0047] In this embodiment, the back panel (1) is made of interwoven fibers, and the fibers are pre-impregnated with thermoplastic resin, and the warp or weft direction of the fibers is the same as the airflow direction of the aircraft engine inlet. It is understood that the types of fibers used in the back panel (1) include any commonly used materials known in the art, such as carbon fiber, glass fiber, nylon and polyethylene fiber. In addition, the fiber material can be formed from any other suitable material known in the art, all of which are within the spirit and scope of the present disclosure. The back panel (1) is away from the end of the airflow carrying noise. Furthermore, the thickness of the back panel is less than or equal to 0.5 mm.

[0048] It can be understood that by changing the thickness t of the perforated plate (4) and the diameter d of the holes, the height H of the honeycomb core (2), the filling height H-h1 of the porous sound-absorbing material and the gradient density, the acoustic impedance of the composite structure can be adjusted to achieve the frequency corresponding to the sound absorption peak, the average sound absorption coefficient and the sound absorption frequency range within a wide frequency range.

[0049] Finally, it should be noted that although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An aircraft engine sound absorption and noise reduction composite structure, characterized in that: Include, A back panel (1), the back panel (1) being used to provide an acoustic hard wall environment; A honeycomb core (2), the honeycomb core (2) being fixedly connected to one side of the back plate (1); A porous sound absorbing material (3), wherein the porous sound absorbing material is filled in the honeycomb core (2) near the back plate (1); A perforated plate (4), wherein circular holes (5) are perforated on the surface of the perforated plate (4), and one side of the perforated plate (4) is fixedly connected to the other side of the honeycomb core (2).

2. The aircraft engine sound absorption and noise reduction composite structure according to claim 1, characterized in that: The surface perforations of the perforated plate (4) are circular holes, and every three of the circular holes correspond to a single hole of the honeycomb core. The area of ​​the circular holes (5) is 3-4% of the area of ​​the single hole of the honeycomb core.

3. The aircraft engine sound absorption and noise reduction composite structure according to claim 2, characterized in that: The thickness of the perforated plate (4) is less than or equal to 1 mm.

4. The aircraft engine sound absorption and noise reduction composite structure according to claim 2, characterized in that: The perforated plate (4) is composed of interwoven fibers, and the fibers are pre-impregnated with thermoplastic resin, and the direction of the warp or weft of the interwoven fibers is the same as the direction of the airflow in the air intake duct of the aircraft engine.

5. The aircraft engine sound absorption and noise reduction composite structure according to claim 1, characterized in that: The honeycomb core (2) is made of NOMEX.

6. The aircraft engine sound absorption and noise reduction composite structure according to claim 5, characterized in that: The honeycomb core (2) is composed of semi-concave hexagonal honeycombs, which is different from the honeycomb core composed of a traditional regular hexagonal honeycomb structure. Each concave hexagonal honeycomb unit is adjacent to the other six concave hexagonal honeycomb units around it and has a common edge.

7. The aircraft engine sound absorption and noise reduction composite structure according to claim 1, characterized in that: The porous sound absorbing material (3) is filled in the honeycomb core (2), starting from a position close to the back plate (1), and the filling height is three quarters of the height of the honeycomb core (2).

8. The aircraft engine sound absorption and noise reduction composite structure according to claim 7, characterized in that: The porous sound absorbing material (3) is filled in the honeycomb core (2) in three stages according to a gradient from high to low density. The density of the porous sound absorbing material (3) filled near the back plate (1) is the highest. The density is preferably 9 mg / cm 3 , 4mg / cm 3 and 2mg / cm 3 The filling height of each section is one quarter of the height of the honeycomb core (2).

9. The aircraft engine sound absorption and noise reduction composite structure according to claim 1, characterized in that: The porous sound-absorbing material is a graphene sponge, and the inside of the graphene sponge is a disordered porous structure.

10. The aircraft engine sound absorption and noise reduction composite structure according to claim 1, characterized in that: The back plate (1) is composed of mutually interwoven fibers, and the warp or weft lines of the mutually interwoven fibers are in the same direction as the airflow direction of the aircraft engine air inlet.

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