Low noise muffler cover based on multi-layer composite structure

Abstract

The present invention relates to the technical field of steam turbine silencers, specifically a low-noise silencer shell based on a multi-layer composite structure, comprising a top plate, side plates, edge plates, composite noise reduction strips, and noise interference sheets. Two of the side plates are symmetrically mounted below the top plate, two of the side plates are mounted between the two ends of the side plates, and the top of the side plates is bonded to the top plate, and a plurality of composite noise reduction strips are evenly spaced and bonded between the side plates and the inner wall of the top plate. The present invention accelerates the speed of sound waves after the noise passes through the noise interference sheet, and then the accelerated sound waves interfere with the noise passing through the noise interference sheet under the refraction and reflection of the composite noise reduction strips, thereby significantly reducing the intensity of the sound waves. The present invention also uses a method in which a magnetic sheet vibrates due to the transmission of sound waves, thereby solving the problem in the prior art of silencer shells that the sound absorption effect of the sound-absorbing material cannot be effectively guaranteed for a long time due to large mechanical vibrations, and that regular replacement is required, resulting in high cost of steam turbine silencer.

Description

Technical Field

[0001] The invention relates to the technical field of steam turbine silencer covers, in particular to a low-noise silencer cover based on a multi-layer composite structure. Background Art

[0002] Steam turbines generate high noise levels during operation. Long-term exposure to this high-noise environment can severely damage the hearing of operators and surrounding personnel, potentially leading to permanent hearing loss. To mitigate the adverse effects of high noise levels during steam turbine operation, a silencer enclosure is typically installed on the outside of the turbine. This enclosure effectively reduces noise levels, keeping them within a safe range and protecting personnel's hearing.

[0003] Existing low-noise steam turbine silencer enclosures mostly use steel sections (such as channel steel and rectangular square steel) as the frame, with cold-rolled steel plates on the exterior and perforated plates on the interior. The space between the two plates is filled with sound-absorbing material (such as glass wool). In actual use, it has been found that due to the limited lifespan of the sound-absorbing material and the high-frequency vibrations generated by steam turbine operation, long-term mechanical vibrations can cause the glass fibers to loosen and deform, thereby reducing the sound absorption effectiveness of the glass fiber sound-absorbing material. This not only fails to effectively guarantee sound absorption, but also requires regular replacement of the sound-absorbing material inside the silencer enclosure, resulting in high sound absorption costs for the steam turbine.

[0004] Therefore, a low-noise silencer cover based on a multi-layer composite structure is proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a low-noise sound-absorbing cover based on a multi-layer composite structure. The speed of the sound wave is accelerated after the noise passes through the noise interference plate. The accelerated sound wave then interferes with the noise passing through the noise interference plate under the refraction and reflection of the composite noise reduction strip, thereby greatly reducing the intensity of the sound wave. The magnetic plate is vibrated by the transmission of the sound wave, which solves the problem of high cost of turbine silencer due to the large mechanical vibration of the sound-absorbing cover in the prior art and the inability to effectively guarantee the sound absorption effect of the sound-absorbing material for a long time, requiring regular replacement. The present invention has the advantages of not only effectively extending the service life of the sound-absorbing cover, but also greatly improving the noise reduction effect of the steam turbine.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A low-noise sound-absorbing cover based on a multi-layer composite structure includes a top panel, side panels, edge panels, composite noise reduction strips and noise interference sheets. The two side panels are symmetrically installed below the top panel, the two side panels are installed between the two ends of the two side panels, and the top of the side panels is attached to the top panel. A plurality of composite noise reduction strips are evenly spaced between the side panels and the inner wall of the top panel. The side walls of the composite noise reduction strips are all attached with a plurality of equally spaced noise interference sheets, and the interior of the noise interference sheet is a high-pressure chamber. The noise emitted by the turbine is initially reduced after passing through the noise interference sheet. The noise transmitted to the composite noise reduction strip after reduction interferes with the noise passing through the noise interference sheet under the reflection action of the composite noise reduction strip.

[0008] Preferably, the inner wall of the side plate is constructed with a plane and a wedge-shaped groove, and the plane and the wedge-shaped groove are arranged alternately.

[0009] Preferably, the side panel includes a first spliced ​​panel, a second spliced ​​panel and a semicircular groove, the side walls of the first spliced ​​panel and the second spliced ​​panel are in contact with each other, and the top of the first spliced ​​panel and the second spliced ​​panel are in contact with the top panel, and the semicircular groove is constructed below the first spliced ​​panel.

[0010] Preferably, the composite noise reduction strip includes an arc-shaped fitting frame, a noise reduction frame, a first inclined surface, a second inclined surface and a vacuum cavity. The arc-shaped fitting frame is installed at the corner of the inner wall of the top plate, and the two noise reduction frames are respectively installed at both ends of the arc-shaped fitting frame. The first inclined surface and the second inclined surface are staggered on the side of the noise reduction frame that is not fitted with the top plate or the side plate, and the edge of the first inclined surface is flush with the edge of the second inclined surface. The vacuum cavity is arranged inside the noise reduction frame, and the vacuum cavity is connected to the interior of the arc-shaped fitting frame. The noise reduction frame is arranged to coincide with the position of the plane.

[0011] Preferably, the noise reduction frame includes a first bending piece, a side piece and a second bending piece. The first bending piece and the second bending piece are arranged in parallel, and the top and bottom of the first bending piece and the second bending piece are aligned respectively. The two side pieces are respectively attached between the side walls on the same side of the first bending piece and the second bending piece.

[0012] Preferably, a rotating seat is installed on the inner wall of the side piece, and magnetic pieces are installed between the rotating seats at the same horizontal height, and the magnetism of adjacent sides of the magnetic pieces is arranged in an opposite direction.

[0013] Preferably, the side wall of the first bending piece is configured with a slot located between the first inclined surface and the adjacent second inclined surface.

[0014] Preferably, the noise interference piece includes a first silencer frame, a second silencer frame and an insert block, the bottom of the first silencer frame is fitted with the top of the second silencer frame, the insert block is respectively installed on the side walls of the first silencer frame and the second silencer frame, and the insert block is adapted to the slot.

[0015] Preferably, the first silencer frame includes a first frame body, a sealing strip and a first magnetic block, the first frame body is attached to the side wall of the first bending piece, and the edge of the first frame body is adjacent to the second inclined surface, and the side wall of the first frame body is arranged parallel to the first inclined surface, the sealing strip is attached to the bottom of the first frame body, and the first magnetic block array is attached to the inside of the first frame body.

[0016] Preferably, the second silencer frame includes a second frame body, a second magnetic block and a docking groove, the second frame body is attached to the side wall of the first bending piece, the second magnetic block array is attached to the inner side of the second frame body, and the second magnetic block and the first magnetic block are arranged vertically, the docking groove is opened above the second frame body, and the docking groove is adapted to the sealing strip.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. When the present invention is in use, the noise emitted by the operation of the steam turbine directly passes through the noise interference sheet without being attenuated and is initially reduced. Moreover, since the interior of the noise interference sheet is in a high-pressure state, the propagation speed of the sound wave is accelerated, the wavelength becomes longer, and the frequency is reduced. At the same time, the sound wave collides with the gas molecules more frequently during the propagation process, resulting in faster attenuation of the sound wave energy. The high-pressure environment will also increase the viscosity of the gas, further consuming the energy of the sound wave and reducing the intensity of the sound wave, thereby achieving a better noise reduction effect. In addition, the noise passing through the noise interference sheet to the composite noise reduction strip is reflected and refracted by the composite noise reduction strip, interfering with the noise passing through the noise interference sheet, thereby further consuming the energy of the sound wave and greatly improving the noise reduction effect.

[0019] 2. By setting up the composite noise reduction strip, a part of the noise transmitted to the first bent piece is continuously reflected and refracted between the first bent piece and the noise interference piece under the action of the first inclined surface and the second inclined surface, thereby greatly reducing the intensity of the sound wave. When the sound wave enters the vacuum state of the noise reduction frame, the sound wave with greatly weakened intensity is blocked by the wall of the vacuum chamber of the noise reduction frame and cannot continue to propagate, thereby achieving effective blocking of the sound wave and achieving the purpose of noise reduction, thereby greatly improving the noise reduction effect of the steam turbine.

[0020] 3. The noise interference sheet is in a high-pressure state inside, which can accelerate the initially generated sound waves with a high intensity. The first and second silencer frames, the first and second inclined surfaces form a diamond-shaped space with a notch, which can continuously reflect and refract the sound waves, further reducing the intensity of the sound waves and fully ensuring the noise reduction effect of the silencer cover.

[0021] 4. By setting up the composite noise reduction strips and noise interference sheets, under the joint action of the magnetic sheet, the first magnetic block and the second magnetic block, the sound waves will drive them to vibrate together when passing through them, thereby converting the energy of the sound waves into the internal energy of the magnetic sheet, the first magnetic block and the second magnetic block, which can further deeply reduce the noise intensity and at the same time reduce the vibration amplitude of the silencer cover, which is conducive to ensuring the sealing of the silencer cover after installation, further extending the service life cycle of the silencer cover, and effectively ensuring the sound insulation and noise reduction effect of the silencer cover. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0023] Figure 2 is a cross-sectional view of the side plate of the present invention;

[0024] Figure 3 It is a structural schematic diagram of the side panel of the present invention;

[0025] Figure 4 This is a schematic structural diagram of the composite noise reduction strip and noise interference sheet of the present invention;

[0026] Figure 5 Schematic diagram of the structure of the noise reduction frame of the present invention;

[0027] Figure 6 It is a structural schematic diagram of the side panel of the present invention;

[0028] Figure 7 Schematic diagram of the structure of the first muffler frame of the present invention;

[0029] Figure 8 Schematic diagram of the structure of the second muffler frame of the present invention.

[0030] In the figure: 1. Top plate; 2. Side plate; 21. Plane; 22. Wedge-shaped groove; 3. Side plate; 31. First joint plate; 32. Second joint plate; 33. Semicircular groove; 4. Composite noise reduction strip; 41. Arc-shaped fitting frame; 42. Noise reduction frame; 421. First bending piece; 4211. Slot; 422. Side plate; 4221. Magnetic piece; 4222. Rotating seat; 423. Second bending piece; 43. First inclined plane; 44. Second inclined plane; 45. Vacuum cavity; 5. Noise interference piece; 51. First silencer frame; 511. First frame body; 512. Sealing strip; 513. First magnetic block; 52. Second silencer frame; 521. Second frame body; 522. Second magnetic block; 523. Docking slot; 53. Insert block. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] See also Figures 1 to 8 The present invention provides a low-noise sound-absorbing cover based on a multi-layer composite structure, and the technical solution is as follows:

[0033] Reference Figure 1 and Figure 2 The low-noise sound-absorbing cover based on the multi-layer composite structure includes a top panel 1, a side panel 2, a side panel 3, a composite noise reduction strip 4 and a noise interference sheet 5. The two side panels 2 are symmetrically installed under the top panel 1, and the two side panels 2 are centrally symmetrically arranged about the central axis of the two side panels 3. The two side panels 3 are installed between the two ends of the two side panels 2, and the upper part of the side panels 3 is fitted with the top panel 1. The fitting parts between the top panel 1, the side panels 2 and the side panels 3 are all sealed to ensure that sound waves will not leak from the connection parts of the top panel 1, the side panels 2 and the side panels 3. Multiple composite noise reduction strips 4 are evenly spaced between the side panels 2 and the inner wall of the top panel 1, and the side walls of the composite noise reduction strips 4 are all fitted with multiple noise interference sheets 5 distributed at equal intervals, and the interior of the noise interference sheet 5 is a high-pressure chamber. The noise emitted by the turbine is initially reduced after passing through the noise interference sheet 5. The noise transmitted to the composite noise reduction strip 4 after reduction interferes with the noise passing through the noise interference sheet 5 under the reflection of the composite noise reduction strip 4.

[0034] Reference Figure 3 As an embodiment of the present invention, specifically, the inner wall of the side panel 2 is constructed with a plane 21 and a wedge-shaped groove 22. The plane 21 and the wedge-shaped groove 22 are arranged alternately. The sound waves propagating between the composite noise reduction strips 4 are continuously refracted and reflected in the wedge-shaped grooves 22 under the action of the wedge-shaped grooves 22, thereby achieving a strong reduction effect. The reduced sound waves enter the composite noise reduction strips 4 and can be blocked by the vacuum chamber.

[0035] Reference Figure 2 and Figure 3As an embodiment of the present invention, specifically, the side panel 3 includes a first spliced ​​panel 31, a second spliced ​​panel 32 and a semicircular groove 33. The side walls of the first spliced ​​panel 31 and the second spliced ​​panel 32 are in contact with each other, and the upper parts of the first spliced ​​panel 31 and the second spliced ​​panel 32 are both in contact with the top panel 1. The semicircular groove 33 is configured below the first spliced ​​panel 31. The shape of the semicircular groove 33 can be adjusted according to the installation position of the steam turbine to ensure that the first spliced ​​panel 31 can be tightly fitted to the end of the steam turbine, thereby making the enclosed space formed by the top panel 1, the side panel 2 and the side panel 3 surround the steam turbine. Thus, by enclosing the steam turbine, a better noise reduction effect is achieved on the noise generated by the operation of the steam turbine.

[0036] Reference Figure 4 As an embodiment of the present invention, specifically, the composite noise reduction strip 4 includes an arc-shaped fitting frame 41, a noise reduction frame 42, a first inclined surface 43, a second inclined surface 44 and a vacuum inner cavity 45. The arc-shaped fitting frame 41 is installed at the inner wall corner of the top plate 1. A threaded groove is provided on the outside of the arc-shaped fitting frame 41. The arc-shaped fitting frame 41 can be fixed to the top plate 1 by using a screw to penetrate the top plate 1 and screw into the threaded groove. The noise reduction frame 42 is respectively installed at both ends of the arc-shaped fitting frame 41. The end of the noise reduction frame 42 that is not connected to the arc-shaped fitting frame 41 is a closed structure. After the noise reduction frame 42 is connected to the arc-shaped fitting frame 41, a closed inner cavity can be formed. The first inclined surface 43 and the second inclined surface 44 are staggered on the side of the noise reduction frame 42 that is not fitted with the top plate 1 or the side plate 2. Under the action of the inclined surface 43 and the second inclined surface 44, the sound waves propagating thereto can be reflected and refracted at a higher frequency, thereby reducing the intensity of the sound waves and achieving a better noise reduction effect. The edge of the first inclined surface 43 is flush with the edge of the second inclined surface 44. The vacuum cavity 45 is arranged inside the noise reduction frame 42, and the vacuum cavity 45 is connected to the interior of the arc-shaped fitting frame 41. After the arc-shaped fitting frame 41 and the noise reduction frame 42 are fitted together, the closed cavity is equivalent to the vacuum cavity 45. The noise reduction frame 42 is arranged to coincide with the position of the plane 21. The sound waves propagating between adjacent noise reduction frames 42 will propagate into the wedge-shaped groove 22 and guide the sound waves to continuously refract and reflect through the wedge-shaped groove 22, thereby greatly reducing the intensity of the sound waves by utilizing the wedge-shaped groove 22 designed on the inner wall of the side panel 2.

[0037] Reference Figure 5As an embodiment of the present invention, specifically, the noise reduction frame 42 includes a first bent piece 421, a side piece 422, and a second bent piece 423. The first bent piece 421 and the second bent piece 423 are arranged in parallel. There are multiple spaces with isosceles triangle cross-sections between the side wall of the second bent piece 423 and the plane 21 of the side panel 2. The sound waves propagating between the side pieces 422 will enter between the second bent piece 423 and the side panel 2 under the action of the wedge-shaped groove 22, and the sound wave intensity is reduced by guiding the refraction and reflection of the sound waves, thereby improving the overall noise reduction effect. The first bent piece 421 and the second bent piece 423 are aligned above and below, respectively, and the two side pieces 422 are respectively attached between the side walls on the same side of the first bent piece 421 and the second bent piece 423.

[0038] Reference Figure 6 As an embodiment of the present invention, specifically, a rotating seat 4222 is installed on the inner wall of the side piece 422, and a magnetic piece 4221 is installed between the rotating seat 4222 at the same horizontal height. The magnetism of the adjacent sides of the magnetic piece 4221 is set with opposite poles. Under the action of the rotating seat 4222 and the magnetic piece 4221, when the sound wave passes through the magnetic piece 4221 and the side piece 422, the sound wave causes the side piece 422, the first bent piece 421 and the second bent piece 423 to vibrate, which will drive the magnetic piece 4221 to swing. Since the adjacent sides of the magnetic piece 4221 are set with opposite poles, when a single magnetic piece 4221 swings, it will attract the adjacent magnetic pieces 4221 to swing together through magnetic force, so that multiple magnetic pieces 4221 can swing together, thereby greatly reducing the swing amplitude of the magnetic piece 4221, thereby effectively reducing the swing amplitude of the composite noise reduction strip 4, which is beneficial to maintaining the overall sealing of the sound insulation cover.

[0039] Reference Figure 5 As an embodiment of the present invention, specifically, the side wall of the first bent piece 421 is constructed with a slot 4211 located between the first inclined surface 43 and the adjacent second inclined surface 44. Under the action of the slot 4211, the noise interference sheet 5 is conveniently installed on the side wall of the first bent piece 421.

[0040] Reference Figure 4 As an embodiment of the present invention, specifically, the noise interference piece 5 includes a first silencer frame 51, a second silencer frame 52 and an insert 53. The bottom of the first silencer frame 51 is fitted with the top of the second silencer frame 52. The insert 53 is respectively installed on the side walls of the first silencer frame 51 and the second silencer frame 52, and the insert 53 is adapted to the slot 4211. The first silencer frame 51 and the second silencer frame 52 in the same noise interference piece 5 are fitted with each other, and a closed space is formed inside the first silencer frame 51 and the second silencer frame 52. The first silencer frame 51 and the second silencer frame 52 are installed and connected to the first bent piece 421 through the insert 53.

[0041] Reference Figure 7and Figure 8 As an embodiment of the present invention, specifically, the first muffler frame 51 includes a first frame body 511, a sealing strip 512 and a first magnetic block 513. The first frame body 511 is attached to the side wall of the first bending piece 421, and the edge of the first frame body 511 is adjacent to the second inclined surface 44, and the side wall of the first frame body 511 is arranged parallel to the first inclined surface 43. The sealing strip 512 is attached to the bottom of the first frame body 511, and the first magnetic block 513 array is attached to the inner side of the first frame body 511. The second muffler frame 52 includes a second frame body 521, a second magnetic block 522 and a docking groove 523. The second frame body 521 is attached to the side wall of the first bending piece 421, and the second magnetic block 52 2 array is attached to the inner side of the second frame 521, and the second magnetic block 522 is arranged perpendicular to the first magnetic block 513. The docking groove 523 is opened above the second frame 521 and is adapted to the sealing strip 512. Under the action of the first frame 511 and the second frame 521, it forms a space with a diamond-shaped cross-section in side view with the first inclined surface 43 and the second inclined surface 44. In addition, there is a gap between the end of the first frame 511 and the end of the second frame 521 in the middle part of the diamond-shaped space away from the side plate 2. The gap is used for sound waves to propagate into the diamond-shaped space, and the diamond-shaped space guides the sound waves to continuously refract and reflect, thereby significantly reducing the intensity of the sound waves.

[0042] Working principle: Assemble and fix the top plate 1, side plate 2 and side plate 3 in sequence, assemble the noise interference piece 5 on the composite noise reduction strip 4, and then install the composite noise reduction strip 4 between the inner wall of the top plate 1 and the side plate 2 to form a complete silencer shell. When the assembled silencer shell is installed on the outside of the steam turbine, align the semicircular groove 33 with the two ends of the steam turbine, and then seal the bottom of the silencer shell with the installation part. When the steam turbine is running, the noise emitted by the steam turbine directly diffuses to the inner wall of the top plate 1, side plate 2 and side plate 3. The noise needs to pass through the noise interference piece 5 first. The noise passing through the noise interference piece 5 is preliminarily reduced, and under the action of the high-pressure chamber inside the noise interference piece 5, the sound wave intensity is reduced. The sound waves are reduced, but the speed of sound increases and the wavelength lengthens, and then the sound waves propagate toward the side of the composite noise reduction strip 4. A part of the sound waves is continuously refracted and reflected between the composite noise reduction strip 4 and the noise interference sheet 5. During the refraction process, the intensity of the sound waves gradually decreases. In addition, the sound waves will interfere with the sound waves passing through the noise interference sheet 5, thereby further reducing the intensity of the sound waves. When the sound waves with sufficiently reduced intensity enter the composite noise reduction strip 4 with a vacuum chamber inside, they will be blocked by the wall of the vacuum chamber and cannot continue to propagate, thereby effectively blocking the sound waves and achieving the purpose of noise reduction. In addition, when the sound waves pass through the composite noise reduction strip 4 and the noise interference sheet 5, the vibration amplitude of the silencer shell caused by the sound waves can be effectively reduced.

[0043] Specifically, the noise generated by the steam turbine first propagates between the first silencer frame 51 and the second silencer frame 52. A portion of the sound waves is continuously refracted and reflected in the V-shaped space formed by the first frame 511 and the second frame 521, and the intensity of the sound waves is initially reduced. Then the sound waves enter the first frame 511 and the second frame 521. Since the interior of the first frame 511 and the second frame 521 is a high-pressure chamber, the speed of the sound waves is increased. However, due to the high density of gas molecules in the high-pressure chamber, the sound waves collide with the gas molecules more frequently during propagation, resulting in faster attenuation of the sound wave energy, thereby reducing the intensity of the sound waves. In addition, when the sound waves pass through the first magnetic block 513 and the second magnetic block 522, they drive the first magnetic block 513 and the second magnetic block 522 to vibrate slightly together, further reducing the intensity of the sound waves.

[0044] When the sound wave propagates to the composite noise reduction strip 4 after passing through the noise interference piece 5, it is continuously refracted and generated between the first bending piece 421, the first frame 511 and the second frame 521 under the action of the first inclined surface 43, the second inclined surface 44, the first frame 511 and the second frame 521, and interferes with the higher intensity sound waves that have passed through the noise interference piece 5 and the sound waves that have not passed through the noise interference piece 5, thereby further reducing the intensity of the sound wave. The sound wave with greatly reduced intensity then enters the noise reduction frame 42 of the composite noise reduction strip 4. The noise reduction frame 42 with a vacuum chamber inside has a better isolation effect on the sound waves. At the same time, under the action of the magnetic sheet 4221 and the rotating seat 4222 between the side pieces 422, the vibration amplitude of the arc-shaped fitting frame 41 and the noise reduction frame 42 driven by the sound wave can be greatly reduced by the magnetic sheet 4221, thereby ensuring the sealing of the sound insulation cover after installation.

[0045] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. Low-noise muffler cover based on multi-layer composite structure, characterized by: The invention comprises a top plate (1), a side plate (2), a side plate (3), a composite noise reduction strip (4) and a noise interference sheet (5), wherein two side plates (2) are symmetrically installed below the top plate (1), two side plates (3) are installed between the two ends of the side plates (2), and the top of the side plates (3) is attached to the top plate (1), a plurality of composite noise reduction strips (4) are evenly spaced and attached between the side plates (2) and the inner wall of the top plate (1), the side walls of the composite noise reduction strips (4) are all attached with a plurality of noise interference sheets (5) distributed at equal intervals, and the interior of the noise interference sheet (5) is a high-pressure chamber, and the noise emitted by the steam turbine is initially reduced after passing through the noise interference sheet (5), and the noise transmitted to the composite noise reduction strip (4) after reduction interferes with the noise passing through the noise interference sheet (5) under the reflection action of the composite noise reduction strip (4); The composite noise reduction strip (4) includes an arc-shaped fitting frame (41), a noise reduction frame (42), a first inclined surface (43), a second inclined surface (44) and a vacuum cavity (45), wherein the arc-shaped fitting frame (41) is installed at the inner wall corner of the top plate (1), and the two noise reduction frames (42) are installed at both ends of the arc-shaped fitting frame (41), respectively, and the first inclined surface (43) and the second inclined surface (44) are staggered on the side of the noise reduction frame (42) that is not fitted with the top plate (1) or the side plate (2), and the edge of the first inclined surface (43) is flush with the edge of the second inclined surface (44), and the vacuum cavity (45) is arranged inside the noise reduction frame (42), and the vacuum cavity (45) is communicated with the interior of the arc-shaped fitting frame (41), and the noise reduction frame (42) is arranged to coincide with the position of the plane (21); The noise reduction frame (42) comprises a first bending piece (421), a side piece (422) and a second bending piece (423), wherein the first bending piece (421) and the second bending piece (423) are arranged in parallel, and the upper and lower parts of the first bending piece (421) and the second bending piece (423) are respectively aligned, and the two side pieces (422) are respectively attached between the side walls on the same side of the first bending piece (421) and the second bending piece (423); A rotating seat (4222) is installed on the inner wall of the side piece (422), and magnetic pieces (4221) are installed between the rotating seats (4222) at the same horizontal height, and the magnetism of adjacent sides of the magnetic pieces (4221) is arranged in opposite directions.

2. The low-noise sound-absorbing cover based on a multi-layer composite structure according to claim 1 is characterized in that: The inner wall of the side plate (2) is constructed with a plane (21) and a wedge-shaped groove (22), and the plane (21) and the wedge-shaped groove (22) are arranged alternately.

3. The low-noise sound-absorbing cover based on a multi-layer composite structure according to claim 1 is characterized in that: The side plate (3) comprises a first spliced ​​plate (31), a second spliced ​​plate (32) and a semicircular groove (33); the side walls of the first spliced ​​plate (31) and the second spliced ​​plate (32) are in contact with each other, and the tops of the first spliced ​​plate (31) and the second spliced ​​plate (32) are in contact with the top plate (1); and the semicircular groove (33) is constructed below the first spliced ​​plate (31).

4. The low-noise sound-absorbing cover based on a multi-layer composite structure according to claim 1 is characterized in that: The side wall of the first bent piece (421) is configured with a slot (4211) located between the first inclined surface (43) and the adjacent second inclined surface (44).

5. The low-noise sound-absorbing cover based on the multi-layer composite structure according to claim 4 is characterized in that: The noise interference piece (5) comprises a first silencer frame (51), a second silencer frame (52) and an insert (53), wherein the lower portion of the first silencer frame (51) is fitted with the upper portion of the second silencer frame (52), and the insert (53) is respectively mounted on the side walls of the first silencer frame (51) and the second silencer frame (52), and the insert (53) is adapted to the slot (4211).

6. The low-noise sound-absorbing cover based on the multi-layer composite structure according to claim 5 is characterized in that: The first muffler frame (51) includes a first frame body (511), a sealing strip (512) and a first magnetic block (513), wherein the first frame body (511) is attached to the side wall of the first bending piece (421), and the edge of the first frame body (511) is adjacent to the second inclined surface (44), and the side wall of the first frame body (511) is arranged parallel to the first inclined surface (43), the sealing strip (512) is attached to the bottom of the first frame body (511), and the array of the first magnetic blocks (513) is attached to the inner side of the first frame body (511).

7. The low-noise sound-absorbing cover based on the multi-layer composite structure according to claim 6 is characterized in that: The second silencer frame (52) includes a second frame body (521), a second magnetic block (522) and a docking groove (523), wherein the second frame body (521) is attached to the side wall of the first bending piece (421), the second magnetic block (522) array is attached to the inner side of the second frame body (521), and the second magnetic block (522) and the first magnetic block (513) are perpendicular to each other, and the docking groove (523) is opened above the second frame body (521), and the docking groove (523) is adapted to the sealing strip (512).

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