A vibration-damping and noise-reducing intra-pipeline superstructure

Abstract

This invention proposes a vibration-reducing and noise-reducing superstructure within a pipeline, comprising cells mounted on the inner wall of the pipeline. Each cell consists of two layers. The outer ring of the first layer is interference-fitted with the inner wall of the pipeline, which neither damages the inner wall nor compromises its integrity. The inner wall transfers its deformation to the first layer, causing shear strain and stress. This shear strain and stress cause the first layer to dissipate the energy generated by vibration, thus reducing vibration and noise. The second layer is a mass block, fixedly connected to the first layer. During pipeline vibration, it generates inertial force, which reacts on the inner wall of the pipeline, further reducing vibration and noise. The cell possesses the bandgap of a locally resonant phononic crystal, which can suppress some lower-frequency vibrations and noise within the pipeline. The structure formed by the cell and the inner wall of the pipeline possesses the bandgap of a Bragg scattering phononic crystal, which can suppress other higher-frequency vibrations and noise within the pipeline.

Description

Technical Field

[0001] This invention relates to the field of vibration and noise control technology, specifically to a superstructure within a pipeline for vibration reduction and noise reduction. Background Technology

[0002] When a ship is sailing at low speeds, the mechanical radiated noise from main engines, shafting, propulsion, and piping systems is high, severely impacting acoustic stealth performance. Regarding noise from external vibrations, the piping structure is primarily supported by supports on the hull. The inlet and outlet of the sea-through piping are directly connected to the hull via cup-shaped pipe sections. Vibrations from pumps and nearby machinery directly connected to the sea-through piping are transmitted through the piping to the supports or cup-shaped pipe sections, and then to the hull, causing noise. Regarding noise from internal vibrations, fluid vibrations within the sea-through piping cause fluid noise, which in turn excites flow-induced vibrations in the pipe walls, ultimately transmitting to the hull. Simultaneously, fluid vibrations within the sea-through piping also generate structural noise that propagates along the flow medium, resulting in radiated underwater noise. Therefore, reducing the radiated noise from the piping structure requires controlling both external structural vibrations and internal fluid vibrations.

[0003] With the application of vibration isolation measures such as floating rafts, rubber vibration isolators, and flexible joints, external noise caused by mechanical equipment through machine feet and bases has been effectively suppressed. However, noise within the pipeline structure has not been well suppressed, becoming the primary channel for noise transmission. Therefore, there is an urgent need for a vibration reduction and noise reduction device for pipeline structures that can reduce noise and vibration inside and outside the pipeline and improve acoustic stealth performance. Summary of the Invention

[0004] In view of this, the present invention provides a superstructure for reducing vibration and noise inside pipelines, which can reduce noise and vibration inside and outside pipelines and improve acoustic stealth performance.

[0005] The technical solution to achieve the purpose of the invention is as follows:

[0006] A vibration-damping and noise-reducing internal superstructure for pipelines includes multiple cells installed on the inner wall of the pipeline, with the cells spaced apart.

[0007] The cell consists of two layers. The first layer is an outer ring and a support strip installed inside the outer ring. The outer ring is interference-fitted with the inner wall of the pipe. The second layer is a mass block, which is fixedly connected to the inner side of the outer ring of the second layer via the support strip.

[0008] The cell has a local resonant phononic crystal band gap I, and the structure composed of the cell and the inner wall of the pipe has a Bragg scattering phononic crystal band gap II. The lower limit of band gap I is the lower limit of the vibration reduction frequency, the upper limit of band gap I is the lower limit of band gap II, and the upper limit of band gap II is the upper limit of the vibration reduction frequency.

[0009] Furthermore, the number of support bars is determined based on the vibration reduction frequency of the pipeline, and the support bars include either spokes or springs.

[0010] Furthermore, the mass block is a sphere or a circular plate.

[0011] Furthermore, when the mass block is a sphere, the sphere can be a hollow sphere or a solid sphere; when the mass block is a circular plate, it can be a circular plate with holes.

[0012] Furthermore, the impedance difference between the material of the outer ring and the material of the inner wall of the pipe is greater than the minimum impedance difference, and the impedance difference between the material of the outer ring and the material of the mass block is greater than the minimum impedance difference.

[0013] Furthermore, the spacing between two adjacent cells is determined by the pipe length and the total number of cells.

[0014] Furthermore, the total number of cells satisfies the noise reduction target, cost constraints, and minimum flow velocity constraints within the pipe.

[0015] A vibration-damping and noise-reducing pipeline internal superstructure includes multiple cells installed on the inner wall of the pipeline, with the cells spaced apart. Each cell comprises two layers: the first layer is an outer ring and a support strip installed on the inner side of the outer ring, with the outer ring and the inner wall of the pipeline having an interference fit; the second layer is a mass block, which is fixedly connected to the inner side of the outer ring of the second layer via the support strip; the first and second layers constitute a tuned mass damper; the inner wall of the pipeline, the first and second layers constitute a constraint damping layer.

[0016] Beneficial effects:

[0017] 1. This invention proposes a vibration-reducing and noise-reducing superstructure within a pipeline, comprising cells installed on the inner wall of the pipeline. Each cell comprises two layers. The outer ring of the first layer is interference-fitted with the inner wall of the pipeline, which neither damages the inner wall nor prevents a tight connection between the first layer and the inner wall. The inner wall of the pipeline transfers its deformation to the first layer, causing shear strain and stress in the first layer. This shear strain and stress cause the first layer to dissipate the energy generated by vibration, thereby reducing vibration and noise. The second layer is a mass block, fixedly connected to the first layer. When the pipeline vibrates, it generates inertial force, which reacts on the inner wall of the pipeline, further reducing vibration and noise. The cell has the bandgap of a localized resonant phononic crystal, which can suppress some lower-frequency vibrations and noise within the pipeline. The structure formed by the cell and the inner wall of the pipeline has the bandgap of a Bragg scattering phononic crystal, which can suppress other higher-frequency vibrations and noise within the pipeline.

[0018] 2. Support bars include either springs or spokes, and their total number is determined by the frequency of pipeline vibration; more bars are needed for higher frequencies, and fewer bars are needed for lower frequencies. To suppress lower frequency vibrations, the number of support bars is reduced to increase the impedance difference between the first and second layers, thus lowering the lower bandgap frequency limit. To suppress higher frequency vibrations, the number of support bars is increased to decrease the impedance difference between the first and second layers, thus raising the upper bandgap frequency limit.

[0019] 3. The mass block is a hollow sphere or a perforated circular plate, which can reduce the mass of the mass block, and the perforated circular plate can also reduce the flow resistance, thereby increasing the fluid flow velocity.

[0020] 4. The impedance difference between two adjacent layers of material is greater than the minimum impedance difference, making it easy to obtain the bandgap frequency band required by this invention.

[0021] 5. The total number of cells is determined based on vibration reduction and noise reduction requirements, cost, and minimum flow velocity in the pipe, to complete the task of vibration reduction and noise reduction while ensuring normal operation of the pipeline.

[0022] 6. This invention proposes a vibration reduction and noise reduction pipeline internal superstructure, comprising cells installed on the inner wall of the pipeline, each cell comprising two layers. The first layer and the second layer constitute a tuned mass damper with multiple degrees of freedom, which can suppress some low-frequency vibrations and torsional vibrations within the pipeline, as well as fluid noise; the inner wall of the pipeline, the first layer, and the second layer constitute a constrained damping layer, which can suppress high-frequency bending vibrations of the pipeline. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the present invention.

[0024] Figure 2 This is a structural diagram of a single cell from two different viewing angles.

[0025] Figure 3 This is a schematic diagram of the structure of this embodiment.

[0026] Figure 4 The diagram shows the structure of the cell element in this embodiment from two different viewing angles.

[0027] Figure 5 An isometric drawing of the piping installation.

[0028] Figure 6 This is a front view of the piping installation in this embodiment.

[0029] Figure 7 This is the cell front view of this embodiment.

[0030] Among them, 1-superstructure, 2-cell, 3-inner wall of pipeline, 4-outer ring, 5-support strip, 6-mass block. Detailed Implementation

[0031] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0032] This invention provides, for example Figure 1 The illustrated superstructure 1 for vibration and noise reduction within the pipeline is installed on the inner wall 3 of the pipeline. It can reduce vibration and noise inside and outside the pipeline, improving the acoustic stealth performance of the pipeline. The smallest component of the superstructure 1 is the cell 2, the total number of which is determined by the vibration and noise reduction requirements, cost, and minimum flow velocity inside the pipeline. Experiments have verified that too many cells 2 affect the flow velocity of the fluid inside the pipeline and increase the cost, while too few cells 2 cannot meet the vibration and noise reduction requirements. Therefore, the total number of cells 2 must meet the requirements of vibration and noise reduction, cost constraints, and minimum flow velocity constraints inside the pipeline. The spacing between cells 2 depends on the pipeline length and the total number of cells 2; in this invention, they are evenly spaced.

[0033] like Figure 2 As shown, each cell 2 includes two layers. The first layer consists of an outer ring 4 and a support strip 5 installed inside the outer ring 4. The outer ring 4 is completely covered by the inner wall 3 of the pipeline, and the two form an interference fit. The second layer is a mass block 6, which is fixedly connected to the inner side of the outer ring 4 of the first layer via the support strip 5. The preferred fixing method is a centripetal connection between the support strip 5 and the mass block 6. The support strip 5 includes either spokes or springs, and its number is determined by the vibration damping frequency of the pipeline; higher frequencies require more support strips, and lower frequencies require fewer. Figure 3 As shown, this is cell 2 when support bar 5 is a spring. Mass block 6 is a sphere (e.g., Figure 1 , 2 (as shown) or circular plate (such as) Figure 3 , 4 (As shown). To reduce weight, a hollow sphere can be chosen; similarly, a porous circular plate can be chosen. For example... Figure 4 As shown, using a perforated circular plate can also reduce flow resistance, thereby increasing the fluid velocity. Figure 5 , 6 Figures 7 and 8 are respectively the axonometric view, the front view, and the front view of cell 2 when the support bar 5 is a spoke and the mass block 6 is a solid sphere.

[0034] From the perspective of phononic crystal principles, this invention possesses the bandgap frequencies of both local resonant phononic crystals and Bragg scattering phononic crystals, and can be referred to as superstructure 1. Cell 2 possesses bandgap frequency I of a local resonant phononic crystal, and the structure formed by cell 2 and the inner wall 3 of the pipeline possesses bandgap frequency II of a Bragg scattering phononic crystal. The lower limit of bandgap frequency I is the lower limit of the vibration reduction frequency, the upper limit of bandgap frequency I is the lower limit of bandgap frequency II, and the upper limit of bandgap frequency II is the upper limit of the vibration reduction frequency. The structure of cell 2 can be considered as a local resonant phononic crystal with a low-frequency bandgap (5Hz to 500Hz), which can suppress low-frequency lateral, longitudinal, and torsional vibrations in the pipeline, thereby suppressing fluid noise. The structure formed by the inner wall 3 of the pipeline and cell 2 can be considered as a Bragg scattering phononic crystal with a high-frequency bandgap (500Hz to 10000Hz), which can suppress high-frequency vibrations in the pipeline and the resulting bending deformation of the inner wall 3 of the pipeline.

[0035] From the perspective of shape, the outer contour of the first layer of cell 2 is the same as that of the inner wall 3 of the pipeline. In this invention, the outer contour of cell 2 and the cross-section of the inner wall 3 of the pipeline are both circular.

[0036] From a structural perspective, this invention designs the cell 2 based on the composition of a tuned mass damper and a constrained damping layer. The first and second layers are a combination of an outer ring 4 (damping element), a support bar 5 (stiffness element), and a mass block 6 (inertial mass element). Its structure is similar to the composition of the damping element, stiffness element, and inertial mass element of a tuned mass damper, possessing multiple degrees of freedom. It can suppress low-frequency lateral (direction of pipe cross-sectional diameter), longitudinal (fluid flow direction), and torsional vibrations of the pipeline, as well as fluid noise. When the pipeline generates low-frequency (5Hz to 500Hz) and torsional vibrations, causing fluid noise, it will cause the connected cell 2 to vibrate. The mass block 6 in cell 2 generates inertial force during vibration, which is transmitted to the outer ring 4 via the support bar 5. The outer ring 4 then reacts to the inner wall 3 of the pipeline. Under the tuning effect of cell 2, the vibration of the pipeline is reduced, and the fluid noise is also weakened, achieving the effect of vibration reduction and noise reduction during low-frequency and torsional vibrations.

[0037] The structure consisting of the inner wall of the pipeline, the first layer (damping layer), and the second layer (constraint layer) is similar to a constrained damping layer, which can suppress high-frequency bending vibrations of the pipeline. During high-frequency (500Hz to 10000Hz) vibrations of the pipeline, the bending of the inner wall can cause the first layer to elongate or compress. At this time, the second layer prevents the first layer from elongating or compressing, thus preventing deformation. Shear strain and stress are generated within the first layer under the action of the second layer. This shear strain and stress cause the first layer to dissipate the energy generated by vibration, achieving the effect of vibration reduction and noise reduction during high-frequency vibrations.

[0038] From the perspective of the connection method of each layer, the outer ring 4 forms an interference fit with the inner wall 3 of the pipe, that is, the outer diameter of the first layer of cell 2 is slightly larger than the diameter of the inner wall 3 of the pipe. During installation, the interference fit between the outer ring 4 and the inner wall 3 of the pipe generates elastic pressure, thereby achieving a tight connection. At the same time, the interference fit does not damage the surface of the inner wall 3 of the pipe; in one embodiment, bolts were used to fix the outer ring 4 and the inner wall 3 of the pipe. Although this also achieved a tight connection, experiments showed that damage to the inner wall 3 of the pipe reduced the vibration reduction and noise reduction effect. The interference fit method avoids this problem.

[0039] From a materials perspective, the impedance difference between the material of the outer ring 4 and the material of the inner wall 3 of the pipe is greater than the preset minimum impedance difference, and the impedance difference between the material of the outer ring 4 and the material of the mass block 6 is also greater than the preset minimum impedance difference. Since the inner wall 3 of the pipe is an elastic material, this invention selects a viscoelastic material as the material of the outer ring 4 and metal as the material of the mass block 6. The greater the impedance difference, the easier it is to obtain the bandgap frequency band required by this invention. Furthermore, the number of support bars 5 can also affect the bandgap frequency band. The support bars 5 include either spokes or springs, and their number is determined by the vibration damping frequency of the pipe; more bars are needed for higher frequencies, and fewer bars for lower frequencies. To suppress lower frequency vibrations, the number of support bars 5 is reduced to widen the impedance difference between the first and second layers, lowering the lower limit of the bandgap frequency; to suppress higher frequency vibrations, the number of support bars 5 is increased to narrow the impedance difference between the first and second layers, raising the upper limit of the bandgap frequency.

[0040] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A vibration-damping and noise-reducing internal superstructure for pipelines, characterized in that, It includes multiple cells installed on the inner wall of the pipeline, the cells being spaced apart; The cell unit comprises two layers: The first layer consists of an outer ring and a support strip installed inside the outer ring. The outer diameter of the outer ring is slightly larger than the inner diameter of the pipe. The outer ring is interference-fitted with the inner wall of the pipe and is tightly connected to the inner wall of the pipe. The inner wall of the pipe is made of an elastic material, and the outer ring is made of a viscoelastic material. The second layer is a mass block, which is fixedly connected to the inner side of the outer ring of the first layer via support strips; The cell has a bandgap I of a local resonant phononic crystal, and the structure formed by the cell and the inner wall of the pipe has a bandgap II of a Bragg scattering phononic crystal; the lower limit of bandgap I is the lower limit of the vibration reduction frequency, the upper limit of bandgap I is the lower limit of bandgap II, and the upper limit of bandgap II is the upper limit of the vibration reduction frequency. The first and second layers form a tuned mass damper with multiple degrees of freedom, used to suppress some low-frequency lateral, longitudinal, and torsional vibrations, as well as fluid noise, within the pipeline; the inner wall of the pipeline, the first and second layers form a constrained damping layer, used to suppress high-frequency bending vibrations of the pipeline.

2. The pipeline superstructure as described in claim 1, characterized in that, The number of support bars is determined according to the vibration reduction frequency of the pipeline, and the support bars include one of spokes and springs.

3. The pipeline superstructure as described in claim 1, characterized in that, The mass block is a sphere or a circular plate.

4. The pipeline superstructure as described in claim 1 or 3, characterized in that, When the mass block is a sphere, the sphere is either hollow or solid; when the mass block is a circular plate, it is a circular plate with holes.

5. The pipeline superstructure as described in claim 4, characterized in that, The impedance difference between the material of the outer ring and the material of the inner wall of the pipe is greater than a preset impedance difference, and the impedance difference between the material of the outer ring and the material of the mass block is greater than a preset impedance difference.

6. The pipeline superstructure as described in claim 5, characterized in that, The spacing between two adjacent cells is determined by the pipe length and the total number of cells.

7. The pipeline superstructure as described in claim 6, characterized in that, The total number of cells meets the noise reduction target, cost constraints, and minimum flow velocity constraints within the tube.

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