CN112951190B - A low-frequency broadband vibration damping device for variable-section pipeline based on acoustic metamaterials - Google Patents

Abstract

The purpose of the present invention is to provide a low-frequency broadband vibration damping device for variable-section pipelines based on acoustic metamaterials, including a first variable-section pipeline, a straight pipeline, and a second variable-section pipeline. The two ends are respectively connected to the first variable-section section pipeline and the second variable-section section pipeline, and the diameters of the first variable-section section pipeline and the second variable-section section pipeline increase in the direction away from the straight section pipeline to form The minimum section near one end of the straight pipe section pipeline and the maximum section at one end away from the straight section pipeline, the outer wall of the straight section pipeline is provided with a local oscillator along the circumferential direction, and the local oscillator includes a local oscillator mass unit and a local oscillator elastic unit, The local oscillator elastic unit is sandwiched between the straight pipe section pipeline and the local oscillator mass unit. The local oscillator elastic unit is combined with the local oscillator mass unit to form a broadband low frequency band gap. The elastic unit and the mass unit are arranged radially and axially, which can reduce torsional vibration, radial vibration and axial vibration.

Description

A low-frequency broadband vibration damping device for variable-section pipelines based on acoustic metamaterials

technical field

The invention relates to a vibration damping device, in particular to a pipeline vibration damping device.

Background technique

The study of acoustic metamaterials originated from local resonance phononic crystals. The concept of local resonance phononic crystals was first proposed in 2000. A simple local resonance phononic crystal model can be constructed by artificially arranging the local resonance units periodically in the elastic medium. Through research, it is found that it can form a low frequency band gap in some special ranges. It was only in 2004 that the concept of acoustic metamaterials was first proposed. A new type of phononic crystal formed by burying a soft silicone rubber scatterer in water can exhibit special acoustic parameter characteristics in a certain frequency range, and the equivalent mass density and equivalent bulk modulus will be negative. . It can generate a low-frequency local resonance band gap in the sub-wavelength band of the structure size, which can realize the control of low-frequency vibration and noise through a small-sized structure. At present, the most common way to construct acoustic metamaterials is to regularly or periodically arrange structural units that can produce local resonance effects in the matrix material.

In the pipeline system, the vibration and noise of medium and high frequency can be well controlled according to the current technology, such as installing a muffler at the downstream position of the pipeline. In addition, adding buffers, setting orifice plates, filters, etc. can also be used to suppress pipeline vibration. However, the low-frequency vibration noise has long propagation distance, small attenuation and too concentrated energy, so it is quite difficult to control the low-frequency vibration noise. Traditional sound-absorbing and sound-insulating materials are not very effective in controlling low-frequency vibration and noise. However, as a new type of lightweight sound-insulating material, acoustic metamaterials can solve the problem that low-frequency vibration and noise are difficult to control to a certain extent.

To sum up, at present, there is a certain research basis for the medium and high frequency vibration of pipelines, but the low frequency vibration reduction effect is not ideal. The traditional equal-section acoustic metamaterials have a narrow local resonance bandgap bandwidth and a small frequency range of vibration and noise that can be effectively controlled, which seriously limits the wide application of acoustic metamaterials in engineering.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide an acoustic metamaterial based on the combination of the vibration damping mechanism of the acoustic metamaterial and the vibration control problem of the pipeline system, and applying this periodic structure to the variable section pipeline to realize the low frequency vibration control below 100Hz. The variable-section pipeline low-frequency broadband vibration damping device.

The object of the present invention is achieved in this way:

The invention is a low-frequency broadband vibration damping device for variable-section pipelines based on acoustic metamaterials, which is characterized in that it includes a first variable-section pipeline, a straight pipeline, and a second variable-section pipeline. The two ends are respectively connected to the first variable section pipeline and the second variable section pipeline, and the three are coaxial. The direction increases to form the smallest section near one end of the straight pipe section and the largest section away from the end of the straight pipe section. The outer wall of the straight pipe section is provided with a local oscillator along the circumferential direction, and the local oscillator includes a local oscillator mass unit and a local oscillator. The local oscillator elastic unit is sandwiched between the straight pipe section pipeline and the local oscillator mass unit.

The present invention can also include:

1. The material of the first variable section section pipeline and the second variable section section pipeline is aluminum, the straight section pipeline material is rubber, the first variable section section pipeline and the second variable section section pipeline and the straight section pipeline The material of the local vibrator elastic unit is rubber, and the material of the local vibrator mass unit is copper.

2. The length of the elastic unit of the local vibrator in the axial direction is less than the length of the straight pipe section along the axial direction, and the local vibrator is arranged in the middle of the straight pipe section.

3. The pipeline length of the first variable section section and the straight section pipeline are equal to the pipeline length of the second variable section section; the outer diameter of the local oscillator mass element is the same as the first variable section pipeline and the second variable section pipeline. Outer diameters are equal.

The advantages of the present invention are:

1. Since the local resonance type acoustic metamaterial has low frequency characteristics, in the present invention, the local oscillator elastic unit is combined with the local oscillator mass unit to form a broadband low frequency band gap.

2. The present invention can realize vibration reduction in multiple frequency bands.

3. The variable-section pipeline in the present invention can be used to change the mass flow.

4. The elastic unit and the mass unit are arranged radially and axially, which can reduce torsional vibration, radial vibration, axial vibration, etc. The wave form in any direction cannot propagate within the band gap range.

Description of drawings

Fig. 1 is the structural representation of the present invention;

Figure 2 shows the energy band diagram of the variable-section pipeline vibration damping device when the width of the vibrator is 0.1 m calculated by the numerical method.

Detailed ways

The present invention will be described in more detail below in conjunction with the accompanying drawings:

1-2, the present invention includes a straight pipe section pipeline 1, a variable section section pipeline 2, and a local oscillator 3, wherein the local oscillator 3 includes a local oscillator mass unit 31 and a local oscillator elastic unit 32. The variable-section pipeline 2 is arranged at both ends of the straight-pipe pipeline 1, and the variable-section pipeline 2 is coaxial with the straight-pipe pipeline 1, and the diameter of the variable-section pipeline 2 is along the The direction away from the straight pipe section pipeline 1 is increased to form a minimum cross section near one end of the straight pipe section pipeline 1 and a maximum cross section away from the straight pipe section pipeline 1 end. The local oscillator elastic unit 32 is sandwiched between the straight pipe section 1 and the local oscillator mass unit 31 . The length of the local oscillator elastic unit 32 in the axial direction is the same as the length of the local oscillator mass unit 31 in the axial direction. The length of the local oscillator elastic unit 32 in the axial direction is smaller than the length of the straight pipe section pipeline 1 in the axial direction.

The local vibrator 3 is installed in the straight pipe section in the variable cross-section piping system, and the position is centered, and the local vibrator is composed of an elastic unit externally connected to a mass unit.

The length of the variable-section pipeline on the left is L1, the length of the straight pipe in the middle is L2, and the length of the variable-section pipeline on the right is L3, L1=L2=L3;

The diameter of the smallest section of the pipeline of the variable section section is the same as the diameter of the pipeline of the straight section.

The local oscillator elastic unit and the local oscillator mass unit have the same length in the axial direction, both are L, and the whole is located in the center of the straight pipe section, that is, the center of the overall variable-section pipeline;

The outer diameter of the local oscillator mass element is R6, the outer diameter of the local oscillator elastic element is R5, the outer diameter of the straight pipe section is R4, the inner diameter of the straight section pipe is R3, the outer diameter of the variable section pipe is R2, and the inner diameter of the variable section pipe is R1, R6 = R2;

The three-section pipeline is coaxial with the local vibrator.

The pipe wall has a certain thickness.

In order to better reduce the vibration of the pipeline, periodic boundary conditions are set at both ends of the variable-section pipeline, so that periodically arranged vibration-damping structural units are realized.

Both the local oscillator mass element and the local oscillator elastic element have different dimensions. The vibration damping structure of the present invention is based on the local resonance mechanism, which can simplify the local oscillator elastic unit and the local oscillator mass unit in the structure into a vibration system composed of a mass and a spring, and different resonances can be generated due to the different sizes of the elastic unit and the mass unit. frequency, so multiple frequency points can be damped.

In this embodiment, the pipeline material of the variable section section is aluminum, the pipeline material of the straight section is rubber, the pipeline of the variable section section and the pipeline of the straight section are bonded, the elastic element of the local oscillator is rubber, and the local oscillator is rubber. The material of the mass unit is copper, the local oscillator elastic unit and the local oscillator mass unit are bonded to form a local resonance unit, the local oscillator is installed in the center of the straight pipe section, and the interior of the pipeline is an air domain.

The low-frequency broadband effect of the device is achieved through the interaction of the local resonance bandgap and the Bragg bandgap. When the pipe material and structural parameters are fixed, the width and radius of different local oscillators, as well as the elastic unit of the local oscillator and the local oscillator can be designed. The material of the vibrator mass unit can also realize the low-frequency broadband effect of the device's band gap.

The structural dimensions of the device are selected as shown in the table below.

The frequency range of the band gap of the present invention is calculated by commercial finite element software as 30-41 Hz, 43-52 Hz, the total bandwidth is 20 Hz, and the energy band diagram is shown in FIG. 2 .

Claims (5)

1. A variable cross-section pipeline low-frequency broadband vibration damper based on acoustic metamaterial is characterized in that: the local oscillator comprises a first variable cross-section pipeline, a straight pipe section pipeline and a second variable cross-section pipeline, wherein two ends of the straight pipe section pipeline are respectively connected with the first variable cross-section pipeline and the second variable cross-section pipeline, the first variable cross-section pipeline and the second variable cross-section pipeline are coaxial, the diameters of the first variable cross-section pipeline and the second variable cross-section pipeline are increased along the direction departing from the straight pipe section pipeline so as to form a minimum cross section close to one end of the straight pipe section pipeline and a maximum cross section far away from one end of the straight pipe section pipeline, a local oscillator is arranged on the outer wall of the straight pipe section pipeline along the circumferential direction, the local oscillator comprises a local oscillator quality unit and a local oscillator elastic unit, and the local oscillator elastic unit is clamped between the straight pipe section pipeline and the local oscillator quality unit.

2. The variable cross-section pipeline low-frequency broadband vibration damper based on the acoustic metamaterial as claimed in claim 1, wherein: the first variable cross-section pipeline and the second variable cross-section pipeline are made of aluminum, the straight pipe section pipeline is made of rubber, the first variable cross-section pipeline and the second variable cross-section pipeline are bonded with the straight pipe section pipeline, the local oscillator elastic unit is made of rubber, and the local oscillator mass unit is made of copper.

3. The variable cross-section pipeline low-frequency broadband vibration damping device based on the acoustic metamaterial according to claim 1 or 2, wherein: the length of the local oscillator elastic unit along the axial direction is smaller than that of the straight pipe section pipeline along the axial direction, and the local oscillator is arranged in the middle of the straight pipe section pipeline.

4. The variable cross-section pipeline low-frequency broadband vibration damping device based on the acoustic metamaterial according to claim 1 or 2, wherein: the length of the first variable cross-section pipeline and the length of the straight pipe section pipeline are equal to the length of the second variable cross-section pipeline; the outer diameter of the local oscillator mass unit is equal to the outer diameters of the first variable cross-section pipeline and the second variable cross-section pipeline.

5. The variable cross-section pipeline low-frequency broadband vibration damper based on the acoustic metamaterial as claimed in claim 3, wherein: the length of the first variable cross-section pipeline and the length of the straight pipe section pipeline are equal to the length of the second variable cross-section pipeline; the outer diameter of the local oscillator mass unit is equal to the outer diameters of the first variable cross-section pipeline and the second variable cross-section pipeline.

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