Composite shock-absorbing and noise-reducing air pipe for ship
Patent Information
- Application Number
- CN202611194974.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-07
- Publication Date
- 2026-10-16
Smart Images
Figure CN122920243A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of duct technology, and in particular to a composite vibration damping and noise reduction duct for ships. Background Technology
[0002] Shipboard ventilation ducts are critical components for cabin environmental control, and their vibration reduction, noise reduction, insulation, and sealing performance directly affect crew comfort and the ship's concealment. Unlike air ducts in land-based buildings, shipboard ventilation ducts face more stringent comprehensive requirements: they must isolate structural sound transmission from rotating equipment such as fans and propulsion systems; they must attenuate airborne sound propagation within the duct to control cabin noise below limits set by IMO A.468(XII) resolutions; they must withstand extreme temperature differences between the engine room and living quarters and prevent condensation; and their connections must have reliable sealing. Furthermore, due to ship stability constraints, the duct walls must be as thin as possible, making it difficult to improve performance by increasing wall thickness. More importantly, military ships and food storage areas have strict restrictions on fiber materials. Traditional fiber sound-absorbing materials such as glass wool and rock wool pose a risk of shedding, which, if they enter the ventilation system, could damage equipment or pose health hazards to personnel. Therefore, fiber sound-absorbing solutions widely used in land-based silencers are not suitable for ships.
[0003] Existing ship ventilation duct solutions have the following structural deficiencies: First, they are functionally limited. A single-layer metal pipe wall or a single-layer damping layer can only provide sound insulation or vibration reduction, making it difficult to meet all four requirements within the same thin wall. Second, the materials are unsuitable. Adhesive fiber sound-absorbing layers are prone to aging and detachment in high-temperature, high-humidity, and salt spray environments, and do not meet the fiber ban constraint. Third, existing solutions are mostly designed only for airborne sound, without axial end seals or enclosed shells. They cannot block the structural sound transmission path from connected pipes and the ship's hull structure, nor can they form an axial seal, while the vibration reduction effect is limited.
[0004] To address the aforementioned issues, there is an urgent need for a structural solution for air supply ducts that can simultaneously meet the requirements of vibration reduction, noise reduction, heat preservation, and sealing under thin-walled conditions, while also complying with the fiber ban constraints for ships. To this end, this application proposes a composite vibration-damping and noise-reducing air duct for ships. Application content
[0005] Based on this, it is necessary to address the technical problems of existing ship ventilation ducts, such as their single-function design, difficulty in simultaneously meeting vibration reduction, noise reduction, heat insulation, and sealing requirements with a single-layer duct wall, the aging and shedding of fiber sound-absorbing materials in the high-temperature, high-humidity, and salt spray environment of ships, failure to meet the fiber ban constraints of military ships and food storage and transportation compartments, and the fact that existing solutions only address airborne sound design, lack axial end seals and enclosed shells, and cannot block the axial structural sound transmission path from connected pipelines and the ship's hull structure. A composite vibration-damping and noise-reducing duct for ships should be provided. This duct achieves broadband attenuation of structural and airborne sound in the radial direction through the synergistic effect of the radial constraint layer, damping composite layer, and Helmholtz resonant cavity. Furthermore, the axial interlocking and crushing energy absorption of the axial positioning damping ring and the annular foam aluminum end seal blocks the axial structural sound transmission path. Vibration reduction, noise reduction, sealing, and heat insulation functions are integrated into the same thin-walled duct. At the same time, zero-fiber materials such as foam aluminum and rubber replace traditional fiber sound-absorbing materials such as glass wool, meeting the fiber ban constraints of ships, significantly reducing the noise level of ship cabins, and extending the service life of the duct in marine corrosive environments.
[0006] The first aspect of this invention provides a composite vibration damping and noise reduction duct for ships, comprising: a composite wall, which has a tubular structure, wherein a first foamed aluminum layer, a cavity layer, a second foamed aluminum layer, and a perforated plate are sequentially arranged radially from the outside to the inside of the composite wall, and the cavity layer is filled with a rubber pad; an outer shell, which is fitted onto the outer surface of the composite wall; a cover, which is disposed at both axial ends of the outer shell, and the sidewalls of the cover are bent and fitted to the outer wall of the outer shell and connected to each other by connectors; an axial positioning damping ring, which is disposed at both axial ends of the composite wall and is enclosed in the outer shell, and the axial positioning damping ring is provided with annular grooves for positioning the first foamed aluminum layer, the cavity layer, the second foamed aluminum layer, and the perforated plate; and an annular foamed aluminum end seal, which is located at both axial ends of the axial positioning damping ring and is enclosed in the cover and the outer shell, wherein the composite wall forms a sandwich structure of "constraint layer - damping layer - constraint layer" radially, and the first foamed aluminum layer and the second foamed aluminum layer are connected to the outer shell. The aluminum foam layer, acting as a high-rigidity constraint layer, sandwiches the rubber pad solid layer, causing it to undergo shear deformation during bending vibrations and dissipate mechanical energy. Simultaneously, the air gaps retained within the cavity layer, in conjunction with the porous plate, form a Helmholtz resonant cavity, absorbing noise at specific frequencies and achieving radial structural sound attenuation and airborne sound absorption. The axial positioning damping ring precisely limits the end faces of each functional layer through annular grooves, preventing interlayer movement caused by ship swaying vibrations. Its own damping elastomer forms a flexible barrier along the vibration transmission path. The annular aluminum foam end seal seals the end cavity opening axially, guiding axial structural sound from adjacent pipe sections via flanges into the aluminum foam pores, where it is dissipated through pore wall friction and crushing, preventing structural sound radiation into the duct. Combined with the enclosed outer shell and cover, this achieves a fully sealed axial enclosure. Overall, a radial-axial integrated composite vibration reduction and noise reduction system is constructed within the same thin-walled pipe section.
[0007] In other embodiments, the rubber pad solid layer is bonded to the first aluminum foam layer and the second aluminum foam layer through an adhesive layer, so that the rubber pad solid layer serves as a viscoelastic damping core layer and the first and second aluminum foam layers serve as constraint layers, together forming a radial constraint layer damping composite layer. The thickness of the rubber pad solid layer is less than the radial depth of the cavity layer, so that an air gap is retained in the cavity layer. This air gap is connected to the airflow channel in the duct through the through holes on the porous plate, forming a resonant cavity. The adhesive bonding and consolidation allow the two aluminum foam constraint layers to form an effective shear constraint on the middle rubber pad solid layer. During vibration, the rubber layer undergoes shear deformation, converting mechanical energy into heat energy for dissipation. Its loss factor is much higher than that of the free damping layer. At the same time, the retained air gap and the through holes on the porous plate together form a Helmholtz resonant cavity, so that the broadband energy dissipation of the constraint layer damping and the frequency selective sound absorption of the resonant cavity are superimposed radially, maintaining a low noise radiation level over a wide frequency band.
[0008] In other embodiments, the first aluminum foam layer and / or the second aluminum foam layer are gradient aluminum foam, which has increasing porosity and decreasing relative density radially from the side closer to the outer shell to the side closer to the cavity layer, forming an acoustic impedance gradient. The acoustic impedance of the gradient aluminum foam changes continuously from the high density on the outer shell side to the low density on the cavity layer side, so that the reflection of sound waves at each layer interface is gradient dispersed, and the incident sound waves can penetrate deeper and be absorbed more smoothly layer by layer, significantly improving the broadband sound absorption coefficient in the mid-low frequency range. At the same time, the high density on the outer shell side ensures the radial support stiffness of the composite wall as a whole, realizing stiffness-damping matching of outer rigidity and inner flexibility.
[0009] In other embodiments, the porous plate is a micro-perforated plate with a pore diameter of 0.2mm to 1mm and a perforation rate of 0.5% to 3%. The micropores are not filled with fibers. The sub-millimeter-level micropores generate strong sound loss due to the viscosity and thermal conduction effect of the air at the pore walls when sound waves are incident. This achieves clean, wide-band sound absorption without the need for any fiber filling material, avoiding the defects of traditional fiber sound-absorbing materials such as glass wool, which are prone to aging and shedding in shipboard salt spray environments and do not meet fiber-free constraints. Furthermore, the smooth inner wall does not accumulate dust or breed microorganisms, meeting the hygiene requirements of clean areas such as food storage and transportation compartments.
[0010] In other embodiments, the axial positioning damping ring includes a metal skeleton and a damping elastomer covering the metal skeleton. The damping elastomer at least forms the groove wall of the annular groove, the side of the axial positioning damping ring facing the annular aluminum foam end seal, and the outer edge facing the outer shell. The metal skeleton provides the overall stiffness required for the positioning ring and the shape retention capability of the annular groove, ensuring that the positioning accuracy of each functional layer does not loosen due to long-term vibration. The damping elastomer covers the groove wall, side, and outer edge of the skeleton, forming elastic contact with the end faces of each layer in the annular groove to avoid rigid compression damage. It forms a flexible vibration isolation interface at the side and outer edge, so that the metal skeleton does not directly and rigidly contact the annular aluminum foam end seal and the outer shell, blocking the rigid transmission of vibration through the metal skeleton to the composite wall or end seal. This allows the axial positioning damping ring to perform positioning functions while also having axial and radial vibration isolation functions.
[0011] In other embodiments, the axial positioning damping ring has an annular shoulder on the side opposite to the composite wall, and the inner edge of the annular aluminum foam end seal has an annular groove. The annular shoulder is embedded in the annular groove, so that the axial positioning damping ring and the annular aluminum foam end seal are axially interlocked. The embedded cooperation of the annular shoulder and the annular groove constitutes an axial mechanical interlock structure, so that the axial positioning damping ring and the annular aluminum foam end seal are engaged with each other in the axial direction. This not only restricts the axial movement and circumferential rotation of the end seal relative to the positioning ring, but also keeps the end seal stably in the design position without the aid of additional fasteners. At the same time, it smoothly guides the axial structural noise from the pipeline through the flange to the crushing energy absorption zone of the aluminum foam end seal, avoiding its rigid impact on the composite wall.
[0012] In other embodiments, the annular aluminum foam end seal is bonded to the end of the composite wall and the outer shell. The bonding and consolidation make the annular aluminum foam end seal, the end of the composite wall and the outer shell axially integrated, forming an integral axial energy-absorbing ring that cannot be disassembled. When the axial structural sound or impact energy transmitted along the pipeline reaches the end seal, the porous aluminum foam absorbs a large amount of vibration energy through buckling and plastic crushing of the pore walls. The residual vibration is further attenuated by the axial positioning damping ring, realizing the dual treatment of "absorption-blocking" of axial vibration. Moreover, the crushing energy absorption process does not invade the inner cavity of the air duct and does not affect the airflow organization.
[0013] In other embodiments, the outer circumferential surface of the first aluminum foam layer is polygonal, and its inner circumferential surface is circular; the cavity layer, the rubber pad solid layer, the second aluminum foam layer, and the perforated plate are all circular rings. The polygonal outer circumferential surface of the first aluminum foam layer, after being fitted into the circular outer shell, forms several discontinuous contact interfaces between the corners and the inner wall of the outer shell, blocking the rigid sound transmission path of the outer shell vibration directly coupled to the aluminum foam through the continuous bonding surface. At the same time, it facilitates the radial clamping and positioning of the outer shell on the composite wall and prevents circumferential free rotation. The circular inner circumferential surface and each inner layer ensure that the air gap of the cavity layer is of uniform thickness along the circumference and the cross-section of the air duct is regular, so as to minimize the airflow resistance and ensure that the characteristics of each unit of the Helmholtz resonator are consistent. The hybrid cross-section of "outer square and inner circle" takes into account both the reliability of assembly positioning and acoustic uniformity.
[0014] In other embodiments, flange connectors are also included, which are respectively disposed at both ends of the axial direction of the duct and are used to connect with the air supply duct or ventilation equipment pipeline. An annular elastic shock-absorbing element is provided between the flange connector and the connected pipeline. The flange connector serves as a standard detachable connection interface between the duct and the upstream and downstream pipelines, which facilitates modular installation, maintenance and replacement in the ship's pipeline system. The annular elastic shock-absorbing element is sandwiched between the flange and the connected pipeline and is compressed and fitted under the pre-tightening force of the flange bolts to form a flexible acoustic barrier. This allows structural noise from the air supply fan or adjacent pipe sections to be significantly attenuated before it enters the duct through the flange, preventing the rigid flange from directly "short-circuiting" the vibration into the composite wall. At the same time, it compensates for the axial and angular offset caused by thermal expansion and contraction and hull deformation of the ship's pipeline and absorbs installation errors.
[0015] The second aspect of this invention provides a method for manufacturing a composite vibration-damping and noise-reducing duct for ships, used to manufacture a composite vibration-damping and noise-reducing duct for ships as described in any of the preceding claims, comprising the following steps: sequentially installing a first aluminum foam layer, a cavity layer, a second aluminum foam layer, and a perforated plate radially from the outside to the inside to form a composite wall with a tubular structure, and embedding a rubber pad solid layer into the cavity layer; installing axial positioning damping rings at both axial ends of the composite wall, such that the annular grooves on the axial positioning damping rings respectively accommodate and position the end faces of the first aluminum foam layer, the cavity layer, the second aluminum foam layer, and the perforated plate; fitting a shell onto the outer surface of the composite wall, such that the axial positioning damping rings are enclosed within the shell; and installing axial positioning damping rings at their axial... Annular aluminum foam end seals are installed at both ends; a cover is installed at both axial ends of the outer shell, and the sidewalls of the cover are bent and attached to the outer wall of the outer shell and connected to each other by connectors, so that the annular aluminum foam end seals are covered by the cover and the outer shell. This method provides a clear and repeatable assembly process: first, the radial composite wall is formed, then the axial end components are positioned, then the outer shell is assembled, and finally the cover is sealed. This ensures the coaxiality and clearance of each layer in the radial direction, and also ensures that the axial positioning damping ring and the end seal are aligned before sealing. This avoids the process contradiction of sealing the shell first and then having difficulty filling the internal components. It is suitable for the standardized and modular production of marine pipelines, facilitates quality inspection and traceability, and also facilitates section replacement at the shipyard or maintenance base. Attached Figure Description
[0016] Figure 1 This is a three-dimensional structural diagram of the present invention.
[0017] Figure 2 This is the main view and a partial sectional view of the present invention.
[0018] Figure 3 for Figure 2 A magnified view of part B in the middle.
[0019] Figure 4 for Figure 2 A sectional view of section AA in the middle.
[0020] in: 100. Composite wall; 110. First aluminum foam layer; 120. Cavity layer; 121. Rubber pad solid layer; 130. Second aluminum foam layer; 140. Perforated plate; 141. Through hole; 200. Outer shell; 300. Cover; 400. Axial positioning damping ring; 410. Annular groove; 420. Metal skeleton; 430. Damping elastomer; 500. Annular aluminum foam end seal; 600. Flange connector. Detailed Implementation
[0021] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.
[0022] In the description of this application, it should be understood that if terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.
[0023] Furthermore, where the terms "first" and "second" appear, these terms are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, where the term "multiple" appears, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.
[0024] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.
[0025] In this application, unless otherwise expressly specified and limited, the use of descriptions such as "above" or "below" the second feature indicates that the first and second features are in direct contact or indirect contact via an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. Similarly, "below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.
[0026] It should be noted that if an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. If an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. If so, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this application are for illustrative purposes only and do not represent the only possible implementation.
[0027] In the enclosed compartments of ships, especially naval vessels and offshore engineering platforms, ventilation and air conditioning duct systems are a significant source of noise. Vibrations generated by fans and air conditioning units during operation propagate along the ducts as structural noise through flanges and supporting structures. Turbulence and eddies in the high-speed airflow within the ducts further excite wall vibrations, generating secondary radiated noise. Simultaneously, conventional single-layer metal ducts have high wall stiffness and low damping, limiting their ability to isolate broadband noise. Furthermore, due to the lack of damping in the axial direction, structural noise can be transmitted to adjacent compartments with almost no attenuation. The composite vibration-damping and noise-reducing duct provided in this embodiment is designed to address these technical challenges. Through the synergistic effect of multiple damping and constraint layers in the radial direction, and the vibration isolation and energy absorption in the axial direction by the axial positioning damping ring 400 and the annular aluminum foam end seal 500, a radial-axial integrated composite noise reduction system is constructed. This system is suitable for low-noise ventilation scenarios in various types of ships, including compartment ventilation, engine room ventilation, and special compartments.
[0028] Specifically, such as Figures 1-4 As shown in the figure, this embodiment discloses a composite vibration damping and noise reduction duct for ships, including a composite wall 100, an outer shell 200, a cover 300, an axial positioning damping ring 400, and an annular foam aluminum end seal 500. It is used for the pipeline connection between the air supply duct and the ventilation equipment in the ship's ventilation system. While transporting airflow, it performs radial and axial composite vibration damping and noise reduction treatment on the structural noise and aerodynamic noise generated by the pipeline system, blocking the path of vibration and noise radially radiating along the duct wall and axially transmitting to the cabin, thereby significantly reducing the noise level of the ship's cabin.
[0029] like Figures 1-4 As shown, the composite wall 100 in this embodiment has a tubular structure. The composite wall 100 is arranged radially from the outside to the inside as follows: a first foam aluminum layer 110, a cavity layer 120, a second foam aluminum layer 130, and a perforated plate 140. The cavity layer 120 is filled with a rubber pad solid layer 121. As the core noise reduction unit of the air duct, the composite wall 100, arranged radially from the outside to the inside as follows, forms a "constraint-damping-constraint" sandwich structure with the first foam aluminum layer 110, the cavity layer 120, the second foam aluminum layer 130, and the perforated plate 140. The innermost perforated plate 140 defines the airflow channel wall inside the air duct. The aluminum foam is arranged in two layers and placed on both sides of the cavity layer 120. This allows for constraint on the rubber pad layer 121 from both the outside and inside, enabling the rubber pad layer 121 to withstand shear strain during vibration deformation. This efficiently converts the mechanical energy of vibration into the internal heat energy of the viscoelastic material, which is then dissipated. The cavity layer 120 provides space for elastic deformation and the air volume required for acoustic resonance. This layered tubular structure is coaxially nested and has an overall rotational shape, facilitating pipe laying along a predetermined path within the limited space of a ship. Furthermore, each layer is a continuous annular band, avoiding sound leakage at the joints. Compared to a single-layer homogeneous pipe wall, this composite wall 100 improves both low-frequency structural acoustic isolation and mid-to-high-frequency airborne sound absorption, while being significantly lighter than a solid metal wall of the same stiffness, which is beneficial for the lightweighting and center of gravity control of the ship.
[0030] like Figures 1-4 As shown, in this embodiment, the outer shell 200 is fitted onto the outer surface of the composite wall 100. The outer shell 200 is preferably a thin-walled metal cylinder, fitted over the outermost first aluminum foam layer 110 of the composite wall 100. On one hand, it serves as an overall protective and binding component for the composite wall 100, radially clamping and positioning each functional layer to prevent relative misalignment between layers. On the other hand, the outer shell 200, together with the cover 300 and the composite wall 100, encloses a closed mounting cavity, allowing the axial positioning damping ring 400 and the annular aluminum foam end seal 500 to be completely covered, preventing the aluminum foam material from absorbing moisture or being corroded by sea winds in the humid salt spray environment of a ship, thus preventing performance degradation. The outer shell 200 also bears part of the load from external pipeline supports and hull deformation, and transmits this load to adjacent pipe sections through the cover 300 and connectors, thereby protecting the internal damping layer from being crushed. In terms of manufacturing and maintenance, the outer shell 200 can be pulled out as a whole, which facilitates the assembly and replacement of the composite wall 100 assembly. Its outer surface can also be provided with an anti-corrosion coating or an anodized layer to further improve its durability in marine environments.
[0031] like Figures 1-3As shown, in this embodiment, the cover 300 is disposed at both axial ends of the outer shell 200, and the sidewalls of the cover 300 are bent and attached to the outer wall of the outer shell 200 and connected to each other by connectors. The cover 300 has a cap-shaped structure and is fastened to the ports at both axial ends of the outer shell 200. Its sidewalls are stamped or rolled to form folded edges and are tightly attached to the outer wall of the outer shell 200. Then, the two sides of the cover 300 and the outer shell 200 are fastened together by bolts, rivets or clamps evenly distributed along the circumference, thereby enclosing the axial end of the composite wall 100, the axial positioning damping ring 400 and the annular foam aluminum end seal 500 in the end cavity formed by the outer shell 200 and the cover 300. By using a bending and bonding method instead of welding or penetrating fastening, the connector only acts on the overlapping and bonding surfaces of the outer shell 200 and the cover 300, without piercing the internal first foam aluminum layer 110 and cavity layer 120, thus not damaging the continuity and airtightness of the radial damping layer; at the same time, the split cover 300 structure facilitates partial disassembly and assembly during maintenance without damaging the main body of the composite wall 100.
[0032] like Figure 3 As shown, the axial positioning damping ring 400 in this embodiment is disposed at both ends of the composite wall 100 and enclosed in the outer shell 200. The axial positioning damping ring 400 is provided with annular grooves 410 for positioning the first aluminum foam layer 110, the cavity layer 120, the second aluminum foam layer 130, and the perforated plate 140. The axial positioning damping rings 400 are arranged in pairs at both ends of the composite wall 100. Multiple annular grooves 410 are sequentially opened radially on the ring body and respectively correspond to and fit into the end faces of the first aluminum foam layer 110, the cavity layer 120, the second aluminum foam layer 130, and the perforated plate 140. This allows for precise positioning of each functional layer in both axial and circumferential dimensions, preventing axial movement or radial misalignment between layers caused by swaying, bumping, and vibration during ship navigation, and ensuring that each damping layer always maintains the stacking sequence and gap size required by the design. Because the positioning ring is enclosed within the outer shell 200 and between the cover 300 and the annular aluminum foam end seal 500, it serves both as a mechanical positioning reference and, with the help of its own damping elastic body 430, forms a flexible barrier on the vibration transmission path, allowing vibrations inside the composite wall 100 to be partially absorbed before propagating to both axial ends. The groove shape and depth of the annular groove 410 are designed to match the thickness tolerances of each layer's end face, enabling gapless press-fitting and reducing the impact of cumulative assembly errors on radial damping performance.
[0033] like Figure 3As shown, in this embodiment, the annular aluminum foam end seal 500 is located at both ends of the axial positioning damping ring 400 and is enclosed within the housing 300 and the outer shell 200. The annular aluminum foam end seal 500 is arranged on the side of the axial positioning damping ring 400 away from the composite wall 100, that is, in the inner cavity of the housing 300 at the outermost axial end of the duct, axially adjacent to the axial positioning damping ring 400 and jointly enclosed and sealed by the housing 300 and the outer shell 200. This end seal blocks the openings of the two end cavities in the axial direction, preventing external foreign objects, salt spray, and condensate from entering the internal cavity of the composite wall 100. It also serves as a soft endpoint on the axial sound transmission path, guiding the axial structural sound transmitted from adjacent pipe sections via flanges into the porous structure of its own porous aluminum foam. The vibration energy is dissipated through pore wall friction and material crushing, preventing the structural sound from directly penetrating the composite wall 100 and radiating into the duct. Because it is located outside the axial positioning damping ring 400 and interlocked with the positioning ring shoulder through the annular groove, the end seal, positioning ring, composite wall 100, and outer shell 200 form a continuous energy absorption-vibration isolation chain in the axial direction, so that both ends of the entire duct have vibration reduction sealing capabilities, solving the problem that the ends of traditional ducts become sound bridges and lack axial vibration isolation.
[0034] In this embodiment, the rubber pad solid layer 121 is bonded to the first aluminum foam layer 110 and the second aluminum foam layer 130 through an adhesive layer, so that the rubber pad solid layer 121 serves as a viscoelastic damping core layer, and the first aluminum foam layer 110 and the second aluminum foam layer 130 serve as constraint layers, together forming a radial constraint layer damping composite layer; the thickness of the rubber pad solid layer 121 is less than the radial depth of the cavity layer 120, so that an air gap is retained in the cavity layer 120. This air gap is connected to the airflow channel in the duct through the through hole 141 on the perforated plate 140, forming a resonant cavity. Specifically... The working principle is as follows: when the composite wall 100 is subjected to bending vibration, the rubber pad solid layer 121 sandwiched between two high-stiffness aluminum foam constraint layers is forced to undergo shear deformation. The viscoelastic rubber converts the vibration mechanical energy into heat energy dissipation in the reciprocating shear. Its loss factor is much higher than that of the free damping layer, so it can obtain better vibration attenuation under the same surface density. The first aluminum foam layer 110 and the second aluminum foam layer 130, with their high specific stiffness and porous skeleton, provide sufficient constraint stiffness on the one hand, and also have a certain sound absorption and scattering ability on the other hand. Meanwhile, because the thickness of the solid rubber pad 121 is less than the radial depth of the cavity layer 120, the cavity layer 120 is not completely filled, leaving an annular air gap. This air gap is connected to the air duct through the through-holes 141 of the perforated plate 140, forming a set of circumferentially distributed Helmholtz resonant cavities. When sound waves of a specific frequency are incident in the air duct, the air column in the air gap resonates with the micropores of the perforated plate 140, converting sound energy into viscous loss within the cavity for absorption, thus providing a good notch effect for narrowband peak noise. The radial constraint layer damping and the Helmholtz resonant cavity are complementary in mechanism—the former dissipates energy over a wide frequency range, while the latter absorbs sound selectively. The combination of the two ensures that the air duct maintains a low noise radiation level over a wide frequency range.
[0035] In this embodiment, the first aluminum foam layer 110 and / or the second aluminum foam layer 130 are gradient aluminum foam, with increasing porosity and decreasing relative density radially from the side near the outer shell 200 to the side near the cavity layer 120, forming an acoustic impedance gradient. Conventional homogeneous aluminum foam has a single acoustic impedance within the layer, and sound waves are easily reflected at the layer interface, thus limiting the absorption efficiency. In this embodiment, gradient aluminum foam with radially varying porosity is used, which smoothly transitions from the high-density side near the outer shell 200 to the high-porosity side near the cavity layer 120. The equivalent acoustic impedance of the material changes continuously accordingly, and the wave impedance difference with the adjacent medium is gradient-dispersed, thereby significantly reducing sound reflection at the layer and interlayer interfaces, allowing incident sound waves to smoothly penetrate layer by layer and be gradually absorbed, significantly improving the broadband sound absorption coefficient in the mid-low frequency range. Furthermore, the higher relative density near the outer shell 200 ensures that the composite wall 100 as a whole still possesses sufficient radial support stiffness and impact resistance, while the high porosity near the cavity layer 120 provides a larger specific surface area and viscous energy dissipation space, achieving a stiffness-damping match of external rigidity and internal flexibility, thus balancing the dual requirements of structural load-bearing and acoustic energy dissipation. In manufacturing, gradient aluminum foam can achieve continuous control of porosity through foaming processes or powder metallurgy layered sintering.
[0036] In this embodiment, the perforated plate 140 is a micro-perforated plate with a pore diameter of 0.2mm to 1mm and a perforation rate of 0.5% to 3%. Since there is no fiber filling in the micropores, and the plate thickness is much smaller than the wavelength and the pore diameter is on the sub-millimeter scale, the air at the pore wall experiences strong loss due to viscosity and thermal conduction when sound waves enter the micropores. This allows for wide-bandwidth and clean sound absorption without porous fiber fillers. In this embodiment, the perforated plate 140 is set as a micro-perforated plate with a pore diameter of 0.2mm to 1mm and a perforation rate of 0.5% to 3%. This parameter range balances high-frequency micropore damping with low-frequency neck mass effect: the smaller pore diameter increases the specific surface area of the pore wall and enhances viscous dissipation, extending the sound absorption frequency band to higher frequencies; the 0.5% to 3% perforation rate ensures sufficient acoustic quality to resonate with the rear air gap, achieving effective absorption of the target frequency band. The micropores are not filled with fibrous material, keeping the inner wall of the duct smooth, dust-free, and free from microbial growth. This perfectly meets the requirements of air cleanliness and food hygiene in enclosed ship compartments. Furthermore, the micro-perforated panel is corrosion-resistant, resistant to high and low temperatures, and non-flammable, maintaining long-term stability in the high-temperature and salt spray environment of the engine room. This avoids the drawbacks of traditional fiber-based sound-absorbing materials such as glass wool and rock wool, which are prone to detachment and require regular replacement. The micro-perforated panel also acts as the "neck" of the resonant cavity, working in conjunction with the 120° air gap in the cavity layer to achieve Helmholtz resonance.
[0037] In this embodiment, the axial positioning damping ring 400 includes a metal skeleton 420 and a damping elastomer 430 covering the metal skeleton 420. The damping elastomer 430 at least forms the groove wall of the annular groove 410, the side of the axial positioning damping ring 400 facing the annular aluminum foam end seal 500, and the outer edge facing the outer shell 200. The damping elastomer 430 elastically contacts the end faces of the first aluminum foam layer 110, the cavity layer 120, the second aluminum foam layer 130, and the porous plate 140 on one hand, and forms a flexible vibration isolation interface on the side and the outer edge on the other hand, so that the metal skeleton 420 does not directly and rigidly contact the annular aluminum foam end seal 500 and the outer shell 200. The metal skeleton 420 is preferably a ring-shaped component made of steel or aluminum alloy, providing the overall rigidity required for the positioning ring and the shape retention capability of the annular groove 410, ensuring that the positioning accuracy of each functional layer does not loosen due to long-term vibration. The damping elastomer 430 is made of viscoelastic material with both high damping and aging resistance, such as butyl rubber, silicone rubber, or polyurethane, and is coated on the groove wall, side, and outer edge of the metal skeleton 420 by injection molding or vulcanization. The above-mentioned flexible vibration isolation interface plays a role in both the axial and radial directions: In the axial direction, the damping elastomer 430 is located between the metal skeleton 420 and the annular aluminum foam end seal 500, absorbing and buffering the structural vibration from the end seal side, preventing the metal skeleton 420 from rigidly transmitting the vibration to the interior of the composite wall 100; In the radial direction, the outer edge of the damping elastomer 430 is in elastic contact with the inner wall of the outer shell 200, so that the positioning ring and the outer shell 200 form a flexible support rather than a rigid hard contact, blocking the radial coupling of vibration through the outer shell 200 to the composite wall 100. Therefore, while performing its mechanical positioning function, the axial positioning damping ring 400 itself constitutes a two-way axial-radial damping and vibration isolation element, which complements the radial constraint layer damping composite layer in function and together constitutes the composite noise reduction skeleton of the present invention.
[0038] In this embodiment, the axial positioning damping ring 400 has an annular shoulder on the side opposite to the composite wall 100, and the inner edge of the annular aluminum foam end seal 500 has an annular groove. The annular shoulder is embedded in the annular groove, so that the axial positioning damping ring 400 and the annular aluminum foam end seal 500 are axially interlocked. The embedded cooperation of the annular shoulder and the annular groove constitutes an axial mechanical interlock structure, so that the axial positioning damping ring 400 and the annular aluminum foam end seal 500 are engaged with each other in the axial direction. This not only restricts the axial movement and circumferential rotation of the end seal relative to the positioning ring, but also keeps the end seal stably in the design position without the aid of additional fasteners, thus avoiding the loss of axial energy absorption function due to long-term vibration of the ship causing the end seal to loosen or shift. When transmitting axial loads, the interlocking interface smoothly guides the axial structural noise from the pipeline via the flange to the crushing energy absorption zone of the aluminum foam end seal, rather than the rigid impact composite wall 100. Simultaneously, this structure provides self-positioning and guiding during assembly; installers only need to align the positioning ring shoulder with the end seal groove and press it in to complete the alignment, reducing the requirements for assembly accuracy and the rework rate. The mating surface between the shoulder and the groove can preferably be designed as a bevel or a rounded transition to disperse contact stress and prevent stress concentration at the corners of the aluminum foam, thus preventing localized crushing cracks.
[0039] In this embodiment, the annular aluminum foam end seal 500 is bonded to the end of the composite wall 100 and the outer shell 200 to form an axial energy absorption ring. This ring guides the axial structural sound from the pipeline and the outer shell 200 into the aluminum foam crushing energy absorption zone and blocks its transmission to the airflow channel inside the duct. Specifically, the bonding can be achieved by using epoxy structural adhesive or polyurethane adhesive to form a continuous adhesive layer between the end face of the composite wall 100, the corresponding area of the inner wall of the outer shell 200 and the end seal. After the adhesive layer is cured, the three are bonded together to form an integral axial energy absorption ring that cannot be disassembled. This consolidation method integrates the axial positioning damping ring 400, the annular aluminum foam end seal 500, the composite wall 100, and the outer shell 200 axially. When the air supply system starts or stops, or when the ship encounters an impact, the axial structural noise and impact energy transmitted along the pipeline first reach the aluminum foam end seal. Under pressure, the porous aluminum foam undergoes buckling of the pore walls and plastic crushing, absorbing a large amount of impact kinetic energy through irreversible plastic deformation. The residual vibration is further attenuated by the damping elastic body 430 of the axial positioning damping ring 400, thus achieving a dual treatment of "absorption-isolation" for axial vibration. Since the aluminum foam end seal is located at the outermost end of the airflow channel and is separated from the air duct by the composite wall 100 and the porous plate 140, its crushing energy absorption process does not intrude into the inner cavity of the air duct, does not affect the airflow organization, and does not radiate secondary noise into the air duct, ensuring the cleanliness and quietness of the ventilation function.
[0040] In this embodiment, the outer peripheral surface of the first aluminum foam layer 110 is polygonal, and its inner peripheral surface is circular; the cavity layer 120, the rubber pad solid layer 121, the second aluminum foam layer 130, and the perforated plate 140 are all circular rings, making the airflow channel inside the duct circular and the air gap in the cavity layer 120 uniform along the circumference. Setting the outer peripheral surface of the first aluminum foam layer 110 as a polygon (in this embodiment, a nonagonal polygon matching the cross-section of the inner wall of the outer shell 200) and keeping the inner peripheral surface circular is for the dual considerations of fitting with the inner wall of the outer shell 200 and acoustic optimization: the outer edge of the polygon can, after being fitted into the circular outer shell 200, have a corner that meets the inner wall of the outer shell 200. Several longitudinal micro-air cavities or line contact supports are naturally formed, which facilitates the radial clamping and positioning of the outer shell 200 on the composite wall 100 and prevents the composite wall 100 from circumferentially rotating inside the outer shell 200. It also creates a discontinuous contact interface between the outer surface of the first aluminum foam layer 110 and the outer shell 200, blocking the rigid sound transmission path of the outer shell 200 vibration directly coupled to the aluminum foam through the continuous bonding surface. The inner circumferential surface and each inner layer remain circular, which ensures that the air gap of the cavity layer 120 is of uniform thickness along the circumference and that the cross-section of the air duct is a regular circle, minimizing airflow resistance and ensuring that the characteristics of each unit in the Helmholtz resonator are consistent, avoiding sound leakage or eddy noise caused by local gaps. This hybrid cross-section of "outer square and inner circle" takes into account both the reliability of assembly positioning and acoustic uniformity. Moreover, the processing technology of the circular inner layer and the forming technology of the perforated plate 140 are mature, which facilitates mass production and quality control.
[0041] In this embodiment, flange connectors 600 are also included, which are located at both ends of the axial direction of the duct and are used to connect with the air supply duct or ventilation equipment pipeline. An annular elastic shock-absorbing element is provided between the flange connector 600 and the pipeline to which it is connected. The flange connector 600 is located at both ends of the axial direction of the duct and is connected to the ends of the cover 300 and the outer shell 200. It serves as a standard detachable connection interface between the duct and the upstream air supply fan outlet, downstream branch pipe or cabin air outlet, which facilitates modular installation, maintenance and replacement in the ship's pipeline system. The annular elastic shock-absorbing element sandwiched between the flange and the pipeline is compressed and fitted under the pre-tightening force of the flange bolts to form a flexible acoustic barrier: the structural noise from the air supply fan or adjacent pipe section is greatly attenuated by the elastic shock-absorbing element before it enters the duct through the flange, avoiding the rigid flange from directly "short-circuiting" the vibration into the composite wall 100; at the same time, the element can also compensate for the axial and angular offset of the ship's pipeline caused by thermal expansion and contraction and hull deformation, absorb installation errors, and prevent additional stress from being introduced at the flange due to forced alignment. In some embodiments, the elastic shock-absorbing element 700 can be further designed as a rubber damping ring with a cavity or a composite shock-absorbing pad with an internal metal skeleton 420 to take into account both pressure resistance and high-frequency vibration isolation; the flange connection surface can also be provided with a sealing groove to install an O-ring to ensure the airtightness and watertightness of the connection of the air duct in the humid environment of the ship.
[0042] Example 2 This embodiment discloses a manufacturing method for a composite vibration-damping and noise-reducing duct for ships, used to manufacture the composite vibration-damping and noise-reducing duct for ships described in Embodiment 1. Through a clear and repeatable assembly process, the aforementioned core components, such as the radial constraint layer damping composite layer, the axial positioning damping ring 400, and the annular aluminum foam end seal 500, are sequentially integrated into the outer shell 200 and the cover 300, so that the final product fully possesses the radial-axial composite noise reduction performance described in Embodiment 1. The method's steps have been optimized: first, the radial composite wall 100 is formed; then, the axial end components are positioned; next, the outer shell 200 is assembled; and finally, the cover 300 is sealed. This ensures the coaxiality and clearance of each layer in the radial direction, and also ensures that the axial positioning damping ring 400 and the end seal are aligned before sealing, avoiding the process contradiction of sealing the shell first and then having difficulty filling the internal components. This process is suitable for the standardized and modular production of ship piping. Each component can be prefabricated and inspected before final assembly, facilitating quality inspection and traceability, and also enabling segmented replacement at the shipyard or maintenance base.
[0043] Specifically, it includes the following steps: A first aluminum foam layer 110, a cavity layer 120, a second aluminum foam layer 130, and a porous plate 140 are sequentially nested radially from the outside to the inside to form a composite wall 100 with a tubular structure. A rubber pad solid layer 121 is embedded in the cavity layer 120. Each layer can be nested sequentially from the inside to the outside using a mandrel tooling. Coaxiality is ensured by using small interference fits or temporary positioning fixtures between each layer. If the first aluminum foam layer 110 and the second aluminum foam layer 130 are gradient aluminum foam, it is necessary to ensure that the direction of increasing porosity is inward to form the correct acoustic impedance gradient. The cavity layer 120 can be pre-made into an open annular sleeve for embedding the rubber pad solid layer 121. Before embedding, the rubber pad solid layer 121 can be pre-bonded to the aluminum foam on both sides by coating an adhesive layer to form a prefabricated sandwich of "constraint-damping-constraint". Then, it is nested together with the porous plate 140 to ensure that the rubber, as a viscoelastic core layer, is evenly sandwiched between the two layers of aluminum foam without air bubbles or missing glue. This prefabrication process can be completed in a cleanroom to ensure that the inner surface of the micro-perforated plate is not contaminated and that the micropores are unobstructed, thereby ensuring the sound absorption performance of the subsequent resonant cavity.
[0044] Axial positioning damping rings 400 are installed at both ends of the composite wall 100. The annular grooves 410 on the axial positioning damping rings 400 respectively accommodate and position the end faces of the first aluminum foam layer 110, the cavity layer 120, the second aluminum foam layer 130, and the perforated plate 140. During installation, the axial positioning damping rings 400, which are formed by covering the metal skeleton 420 and the damping elastomer 430, are pushed into the composite wall 100 from both ends. The multiple annular grooves 410 on the ring are aligned with and fit the end faces of the first aluminum foam layer 110, the cavity layer 120, the second aluminum foam layer 130, and the perforated plate 140. The elasticity of the damping elastomer 430 is used to flexibly hold and position the end faces of each layer. This step is completed before the outer casing 200 is assembled. It temporarily locks the layers at both ends of the composite wall 100 to prevent misalignment during subsequent handling and assembly with the outer casing 200, ensuring that the end faces of each layer are flush on the same axial reference plane. This provides a precise assembly reference for the smooth insertion of the outer casing 200 and the closure of the cover 300. For longer ducts, an auxiliary support ring can also be added in the middle of the composite wall 100 to suppress radial deflection during assembly.
[0045] The outer shell 200 is fitted onto the outer surface of the composite wall 100, so that the axial positioning damping ring 400 is enclosed within the outer shell 200. The outer shell 200 slides along the left or right end of the composite wall 100 axially to the outside of the composite wall 100. During the fitting process, the inner wall of the outer shell 200 elastically contacts the outer edge of the damping elastic body 430 of the axial positioning damping ring 400, tightening the positioning ring together with the composite wall 100 and enclosing it within the cavity of the outer shell 200. The outer shell 200 thus becomes the outer protective sleeve and radial bundle of the composite wall 100 and the positioning ring. During fitting, the coaxiality of the outer shell 200 and the composite wall 100 should be controlled to maintain a design clearance between the inner wall of the outer shell 200 and the polygonal outer edge of the first foam aluminum layer 110, avoiding the outer shell 200 directly and rigidly pressing against the foam aluminum, which would damage the radial damping clearance. After fitting, a mark can be pre-made at the joint between the outer shell 200 and the cover 300 to facilitate the subsequent alignment and installation of the cover 300. After this process is completed, the radial noise reduction body of the duct is sealed, leaving only the axial openings at both ends to await end sealing and enclosure 300 encapsulation.
[0046] Annular aluminum foam end seals 500 are installed at both ends of the axial positioning damping ring 400. The pre-fabricated annular aluminum foam end seals 500 are inserted from the outside of the axial positioning damping ring 400, with their inner annular grooves aligned with the annular shoulder of the positioning ring, pressing them into place to complete axial interlocking. Subsequently, structural adhesive is applied to the end faces of the end seals and the composite wall 100, and to the corresponding areas of the inner wall of the outer shell 200, and then cured under pressure, solidifying the end seals, the ends of the composite wall 100, and the outer shell 200 into a unified axial energy-absorbing ring. This step connects the axial positioning damping ring 400—annular aluminum foam end seal 500—composite wall 100—outer shell 200 in the axial direction into a continuous energy-absorbing and vibration-isolating chain. The end seals are securely confined outside the positioning ring and inside the shell 300, preventing axial detachment and allowing the aluminum foam to crush and absorb energy during impact. Bonding and curing can be carried out in a constant temperature environment under tooling clamping to ensure the strength and long-term reliability of the adhesive layer.
[0047] Covers 300 are installed at both axial ends of the outer shell 200. The sidewalls of the cover 300 are bent and fitted to the outer wall of the outer shell 200 and connected to each other by connectors. The annular aluminum foam end seal 500 is covered inside the cover 300 and the outer shell 200. Finally, the two covers 300 are fastened to the axial ends of the outer shell 200, so that their folded edges are tightly fitted to the outer wall of the outer shell 200. Connectors evenly distributed along the circumference fasten the cover 300 and the outer shell 200. The connection only acts on the overlapping and fitting surface of the outer shell 200 and the cover 300, without piercing the internal aluminum foam and the cavity layer 120, thereby completely sealing the end cavity and covering the annular aluminum foam end seal 500 and the axial positioning damping ring 400 in the closed cavity formed by the cover 300 and the outer shell 200, so that the entire duct is formed. After the casing 300 is closed, the duct should be randomly inspected for airtightness, coaxiality, and vibration transmission characteristics to confirm that each layer is secure, the end seals and positioning rings are properly interlocked, and the flange anti-vibration components are correctly installed. At this point, the composite vibration-damping and noise-reducing duct of Example 1 is complete. Its radial constraint layer damping composite layer, Helmholtz resonant cavity, gradient aluminum foam, axial positioning damping ring 400, and annular aluminum foam end seal 500 have all been integrated according to the design, achieving the expected broadband vibration reduction and noise reduction effect.
[0048] The above description is an explanation of the invention, not a limitation thereof. The scope of the invention is defined in the claims. Within the scope of protection of the invention, any form of modification may be made.
Claims
1. A composite vibration damping and noise reduction duct for ships, characterized in that, include: The composite wall has a tubular structure, and the composite wall is provided with a first foamed aluminum layer, a cavity layer, a second foamed aluminum layer, and a porous plate in a radial direction from the outside to the inside. The cavity layer is filled with a rubber pad solid layer. The outer shell is fitted onto the outer surface of the composite wall; The cover is provided at both axial ends of the outer shell, and the side walls of the cover are bent and attached to the outer wall of the outer shell and connected to each other by connectors. An axial positioning damping ring is provided at both ends of the composite wall and is enclosed in the outer shell. The axial positioning damping ring is provided with annular grooves for positioning the first aluminum foam layer, the cavity layer, the second aluminum foam layer, and the porous plate. The annular aluminum foam end seal is located at both ends of the axial positioning damping ring and is enclosed within the cover and outer shell.
2. The composite vibration damping and noise reduction duct for ships as described in claim 1, characterized in that, The solid rubber pad layer is bonded to the first aluminum foam layer and the second aluminum foam layer through an adhesive layer, so that the solid rubber pad layer acts as a viscoelastic damping core layer and the first aluminum foam layer and the second aluminum foam layer act as constraint layers, together forming a radial constraint layer damping composite layer; the thickness of the solid rubber pad layer is less than the radial depth of the cavity layer, so that an air gap is retained in the cavity layer, and the air gap is connected to the airflow channel in the duct through the through hole on the porous plate, forming a resonant cavity.
3. The composite vibration damping and noise reduction duct for ships as described in claim 1, characterized in that, The first aluminum foam layer and / or the second aluminum foam layer are gradient aluminum foam, which have increasing porosity and decreasing relative density radially from the side closer to the outer shell to the side closer to the cavity layer, forming an acoustic impedance gradient.
4. The composite vibration damping and noise reduction duct for ships as described in claim 1, characterized in that, The porous plate is a micro-perforated plate with a pore diameter of 0.2mm to 1mm, a perforation rate of 0.5% to 3%, and no fiber filling at the micropores.
5. The composite vibration damping and noise reduction duct for ships as described in claim 1, characterized in that, The axial positioning damping ring includes a metal skeleton and a damping elastomer covered on the metal skeleton; the damping elastomer at least forms the groove wall of the annular groove, the side of the axial positioning damping ring facing the annular aluminum foam end seal, and the outer edge facing the outer shell.
6. The composite vibration damping and noise reduction duct for ships as described in claim 1, characterized in that, The axial positioning damping ring has an annular shoulder on the side opposite to the composite wall, and the inner edge of the annular aluminum foam end seal has an annular groove. The annular shoulder is embedded in the annular groove, so that the axial positioning damping ring and the annular aluminum foam end seal are axially interlocked.
7. The composite vibration damping and noise reduction duct for ships as described in claim 1, characterized in that, The annular aluminum foam end seal is bonded to the end of the composite wall and the outer shell.
8. The composite vibration damping and noise reduction duct for ships as described in claim 1, characterized in that, The outer circumferential surface of the first aluminum foam layer is polygonal, and its inner circumferential surface is circular; the cavity layer, the rubber pad solid layer, the second aluminum foam layer, and the porous plate are all circular rings.
9. The composite vibration damping and noise reduction duct for ships as described in claim 1, characterized in that, It also includes flange connectors, which are located at both ends of the axial direction of the air duct and are used to connect with air supply ducts or ventilation equipment pipelines. An annular elastic shock-absorbing element is provided between the flange connector and the pipeline to which it is connected.
10. A method for manufacturing a composite vibration-damping and noise-reducing duct for ships, used to manufacture the composite vibration-damping and noise-reducing duct for ships as described in any one of claims 1 to 9, characterized in that, Includes the following steps: A first aluminum foam layer, a cavity layer, a second aluminum foam layer, and a porous plate are sequentially nested radially from the outside to the inside to form a composite wall with a tubular structure, and a rubber pad solid layer is embedded in the cavity layer. Axial positioning damping rings are installed at both ends of the composite wall, so that the annular grooves on the axial positioning damping rings can respectively accommodate and position the end faces of the first aluminum foam layer, the cavity layer, the second aluminum foam layer, and the porous plate. The outer shell is fitted onto the outer surface of the composite wall, so that the axial positioning damping ring is enclosed within the outer shell; Annular aluminum foam end seals are installed at both ends of the axial positioning damping ring. Covers are installed at both axial ends of the outer shell, and the sidewalls of the cover are bent and attached to the outer wall of the outer shell and connected to each other by connectors, and the annular aluminum foam end seal is covered inside the cover and the outer shell.