A low-frequency broadband acoustic impedance mismatched silencer for liquid lines

Abstract

The application relates to a liquid pipeline low-frequency broadband acoustic impedance mismatch silencer, comprising a liquid pipeline low-frequency broadband acoustic impedance mismatch silencer, which comprises an outer cylinder, a silencing inner flow channel, an elastic resonance cavity and an acoustic impedance mismatch layer; the silencing inner flow channel is arranged in the outer cylinder, the silencing inner flow channel comprises an inner flow channel pipe wall and a support framework, the inner flow channel pipe wall is provided with a cavity diameter opening, and the support framework is coated with an elastic wall surface; the elastic resonance cavity is arranged at the cavity diameter opening of the inner flow channel pipe wall and is used for low-frequency broadband silencing; the acoustic impedance mismatch layer is arranged outside the elastic wall surface and is used for medium-low frequency broadband silencing; wherein the elastic resonance cavity comprises a first layer cavity, a second layer cavity and a cavity diameter; the application combines inner wall acoustic impedance adjustment and elastic resonance, innovatively invents a pressure self-adaptive low-frequency broadband acoustic impedance mismatch silencing structure, realizes low-frequency silencing of a small-size structure, and can meet multiple requirements of water medium pipeline silencing and pressure resistance.

Description

Technical Field

[0001] This invention relates to the field of pipeline noise reduction technology, and in particular to a low-frequency broadband acoustic impedance mismatch silencer for liquid pipelines. Background Technology

[0002] Noise reduction in pipelines mainly utilizes theories such as expansion cavities and Helmholtz resonant cavities. Expansion cavity mufflers, expansion resistive mufflers filled with sound-absorbing cotton, Helmholtz resonant cavity mufflers for low-frequency line spectrum noise reduction, and HQ tubes for low-frequency line spectrum noise reduction in automotive engines are widely used in air silencing. However, research on mufflers has never ceased both domestically and internationally, with efforts focused on optimizing muffler structures, reducing muffler size, and improving low-frequency noise reduction effects. Water-medium pipelines are widely used in various fields and industries, relying on pumps and other equipment to provide head to drive the flow of water, while simultaneously transmitting the vibration noise from these devices. For example, the noise from water pumps in pressurized water supply systems of high-rise buildings can be transmitted along the fluid from the ground floor to the upper floors, causing low-frequency noise pollution in residents' rooms along the transmission path. Ship systems utilize numerous water pumps; the high noise generated when these pumps drive water can be transmitted from the stern to the bow, causing low-frequency noise interference in crew living quarters, affecting their lives and rest. Furthermore, the noise from ship pumps radiates outwards through the drainage system, causing noise pollution to marine fish and the environment. Because the acoustic impedance of water is 3600 times greater than that of air, and the wavelength of sound waves in water is more than four times longer than that in air, it is virtually impossible to achieve low-frequency noise reduction and attenuation in water pipelines using air-based silencing design methods. Even if low-frequency noise reduction were to be achieved, the size of the silencer would inevitably increase significantly, easily constrained by installation space.

[0003] To address the low-frequency noise reduction problem in water-medium pipelines, Harbin Engineering University and other institutions have researched airbag-type water silencers. These silencers utilize airbags arranged on the sidewalls of the flow channels within the pipe. The contact between the airbag walls and the water medium attenuates fluid pressure pulsations and noise, thus reducing noise and suppressing its propagation in the water-medium pipeline. However, to adapt to the pump head and the pressure of the medium within the pipe, this airbag-type silencer structure requires a high-pressure inflation interface and inflation device, as well as gas cylinders or high-pressure gas stations. Based on Helmholtz's silencing theory, the China Shipbuilding Scientific Research Center proposed an elastic resonance silencing method, addressing the incompressibility and strong coupling characteristics of water. Their invention patent, "Pressure-Adaptive Low-Frequency Broadband Elastic Resonance Silencer Device" (ZL201310295322.9), presents an elastic resonance silencing structure unit and multiple silencing units connected in series and parallel to reduce noise in water-medium pipelines. While this silencing structure offers the advantage of flexible assembly, it still suffers from issues such as large size and the need for further improvement in low-frequency silencing performance.

[0004] To address this, we propose a low-frequency broadband acoustic impedance mismatch silencer for liquid pipelines. Summary of the Invention

[0005] In response to the shortcomings of the existing production technology, the applicant provides a low-frequency broadband acoustic impedance mismatch silencer for liquid pipelines. By utilizing the combination of inner wall acoustic impedance adjustment and elastic resonance, an innovative pressure-adaptive low-frequency broadband acoustic impedance mismatch silencer structure is invented, achieving low-frequency silencer in a small-size structure that can meet the multiple requirements of silencer and pressure resistance for water medium pipelines.

[0006] The technical solution adopted in this invention is as follows: A low-frequency broadband acoustic impedance mismatch silencer for liquid pipelines, comprising: outer cylinder; The silencing inner flow channel is set inside the outer cylinder. The silencing inner flow channel includes the inner flow channel wall and the supporting frame. The inner flow channel wall has a cavity opening, and the supporting frame is covered with an elastic wall surface. An elastic resonant cavity is set at the opening in the cavity diameter of the inner flow channel wall for low-frequency broadband noise reduction. An acoustic impedance mismatch layer is placed outside the elastic wall surface for mid-to-low frequency wideband noise reduction. The elastic resonant cavity includes a first cavity layer, a second cavity layer, and a cavity diameter. The first cavity layer and the second cavity layer are separated by an elastic resonant plate. An internal acoustic impedance mismatch layer is provided inside the elastic resonant cavity to improve the coupling resonance of the elastic resonant plate.

[0007] Its further features are: The acoustic impedance mismatch layer includes an elastomer, within which a radial cavity is provided, and a skin is provided on the surface of the radial cavity to seal the radial cavity, so that the low-frequency acoustic impedance is less than 5e5.

[0008] The acoustic impedance mismatch layer includes an elastomer, in which a circumferential skeleton is embedded, and a circumferential air cavity is provided in the circumferential skeleton.

[0009] The acoustic impedance mismatch layer is installed in a circular shape.

[0010] One end of the outer cylinder is provided with a mounting flange, and the other end of the outer cylinder is provided with a flange. The mounting flange has a boss inside the outer cylinder for fixing the acoustic impedance mismatch layer, and the sound-absorbing inner flow channel is fixed by a positioning ring.

[0011] The inner flow channel wall is provided with a connecting hole to ensure pressure balance in the flow channel and the muffler cavity.

[0012] The cavity is provided with multiple small orifice cavities, and the small orifice cavities are provided with micro-orifice cavities to increase flow resistance loss.

[0013] The diameter of the small pore is on the order of centimeters, and the diameter of the micropore is on the order of millimeters.

[0014] The sound-absorbing inner flow channel has multiple cross sections arranged with elastic resonant cavities.

[0015] Each cross section of the silencing inner flow channel is arranged with multiple elastic resonant cavities.

[0016] The beneficial effects of this invention are as follows: This invention features a compact and rational structure, and is easy to operate. The fluid and noise in the pipeline are transmitted to the elastic resonant cavity cross-section of the silencer's inner flow channel. Multiple elastic resonant cavities of the same or different sizes are combined in parallel circumferentially and in series directionally within the cross-section of the silencer's inner flow channel. This achieves low-frequency broadband noise reduction, with a low-frequency acoustic impedance less than 5e5. It can also achieve mid-to-low frequency broadband noise reduction. This invention has a small structural size, a wide-band noise reduction frequency range covering several hertz to several kilohertz, and can be quantitatively optimized based on the peak values ​​of the pump shaft frequency, blade frequency, and other line spectra, achieving both broadband noise reduction and suppression of line spectra peaks. Furthermore, this invention can meet the noise reduction requirements of pipelines from low pressure to high pressure, and can also satisfy the noise reduction requirements of harsh environments such as high temperature and high radiation.

[0017] In addition, the present invention also has the following advantages: (1) The first cavity, the second cavity, the elastic resonant plate and the cavity diameter form an elastic resonant system. The sound absorption peak and frequency band of the elastic resonant cavity can be adjusted by adjusting the thickness or material of the elastic resonant plate. The elastic resonant plate has low stiffness and the sound absorption frequency shifts to low frequency, thereby generating a low frequency sound absorption impedance boundary at the cavity opening of the pipe. It can be quantitatively designed according to the noise line spectrum peak of the pipeline, and low frequency broadband noise reduction can be achieved.

[0018] (2) Since the silencing frequency of the elastic resonant cavity is less affected by the cavity volume, the silencing frequency band can be easily adjusted by changing the material and thickness of the elastic resonant plate. In order to increase the flow resistance loss of the cavity diameter, the traditional single cavity diameter is divided into multiple small cavity diameters, and micro-orifice cavity diameters are arranged in the middle of the small cavity diameters. The micro-orifice cavity diameters can increase the flow resistance friction damage and also filter the pipeline impurities from entering the elastic resonant cavity.

[0019] (3) The acoustic impedance mismatch layer is designed as a combination of elastomer, radial cavity, and skin. By combining the radial cavity and elastomer, the low-frequency acoustic impedance is less than 5e5, which can achieve mid-low frequency wideband noise reduction. Another implementation scheme for the acoustic impedance mismatch layer is to use a circumferential skeleton to form a circumferential cavity, or to use a composite material tube, and to pre-embed the composite material in the elastomer for sealing. Attached Figure Description

[0020] Figure 1 This is a cross-sectional view of the structure of the present invention.

[0021] Figure 2 This is a schematic diagram of the noise-absorbing internal flow channel of the present invention.

[0022] Figure 3 for Figure 2 Schematic diagram of the AA section.

[0023] Figure 4 for Figure 2 Schematic diagram of the BB cross section.

[0024] Figure 5 for Figure 2 Schematic diagram of the CC section.

[0025] Figure 6 This is a diagram showing the arrangement of the elastic resonant cavity of the present invention within the sound-absorbing inner flow channel.

[0026] Figure 7 This is a cross-sectional view of one of the elastic resonant cavity schemes of the present invention.

[0027] Figure 8 This is a cross-sectional view of the second elastic resonant cavity scheme of the present invention.

[0028] Figure 9 This is a schematic diagram of the parallel combination structure of the porous cavity at the cavity inlet of the elastic resonant cavity of the present invention.

[0029] Figure 10 This is one of the acoustic impedance mismatch layer schemes in the silencer of the present invention.

[0030] Figure 11 This is the second solution for the acoustic impedance mismatch layer in the muffler of the present invention.

[0031] The components are: 1. Mounting flange; 2. Outer cylinder; 3. Flange; 4. Positioning ring; 5. Silencing inner flow channel; 51. Inner flow channel wall; 52. Cavity opening; 53. Support frame; 54. Elastic wall; 55. Connecting hole; 6. Elastic resonant cavity; 61. First cavity layer; 62. Second cavity layer; 63. Elastic resonant plate; 64. Cavity diameter; 65. Micropore cavity diameter; 66. Small hole cavity diameter; 67. Intracavity acoustic impedance mismatch layer; 7. Acoustic impedance mismatch layer; 71. Elastomer; 72. Radial cavity; 73. Skin; 74. Circumferential frame. Detailed Implementation

[0032] The specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0033] like Figures 1-11 As shown, a low-frequency broadband acoustic impedance mismatch silencer for a liquid pipeline includes an outer cylinder 2, a positioning ring 4, a silencing inner flow channel 5, an elastic resonant cavity 6, and an acoustic impedance mismatch layer 7. One end of the outer cylinder 2 is provided with a mounting flange 1, and the other end of the outer cylinder 2 is provided with a flange 3. The silencing inner flow channel 5 is disposed within the outer cylinder 2, and both ends of the silencing inner flow channel 5 are fixed by the positioning ring 4.

[0034] The fluid and noise from the pipeline are transmitted to the cross-section of the elastic resonant cavity 6 in the silencer's inner flow channel 5. The elastic resonant cavity 6 includes a first cavity 61, a second cavity 62, an elastic resonant plate 63, a cavity diameter 64, a micro-orifice diameter 65, a small orifice diameter 66, and an internal acoustic impedance mismatch layer 67. The first cavity 61 and the second cavity 62 are separated by the elastic resonant plate 63. The cavity diameter 64 is located on one side of the first cavity 61, and multiple small orifice diameters 66 are provided in the cavity diameter 64. Micro-orifice diameters 65 are arranged in the middle of the small orifice diameters 66. An internal acoustic impedance mismatch layer 67 is provided in the elastic resonant cavity 6 to improve the coupling resonance of the elastic resonant plate 63. The design method is the same as that of the acoustic impedance mismatch layer 7. Both the first cavity 61 and the second cavity 62 are hollow cylinders and can be machined from metal parts. Due to the balance of internal and external pressure, the wall thickness can be determined only to meet the thickness of the mounting bolts. The elastic resonant plate 63 can be a thin metal plate, a rubber elastic plate, or a composite material plate, and its design can be determined based on the modal resonant frequency. It connects to the conduit and the first-layer cavity 61 via a cavity diameter 64. The small-aperture cavity diameter 66 is on the order of centimeters, and the micro-aperture cavity diameter 65 is on the order of millimeters.

[0035] The first cavity 61, the second cavity 62, the elastic resonant plate 63, and the cavity diameter 64 constitute an elastic resonant system. By adjusting the thickness or material of the elastic resonant plate 63, the sound absorption peak value and frequency band of the elastic resonant cavity 6 can be adjusted. The elastic resonant plate 63 has low stiffness, and the sound absorption frequency shifts to lower frequencies, thereby generating a low-frequency sound absorption impedance boundary at the cavity opening of the pipe. Quantitative design can be performed based on the peak value of the pipe's noise spectrum. By combining multiple elastic resonant cavities 6 of the same or different sizes in parallel circumferentially and in series circumferentially within the silencing inner flow channel 5, low-frequency broadband silencing can be achieved.

[0036] Since the silencing frequency of the elastic resonant cavity 6 is less affected by the cavity volume, the silencing band can be easily adjusted by changing the material and thickness of the elastic resonant plate 63. In order to increase the flow resistance loss of the cavity diameter 64, the traditional single cavity diameter 64 is divided into multiple small-hole cavity diameters 66, and micro-hole cavity diameters 65 are arranged in the middle of the small-hole cavity diameters 66. The micro-hole cavity diameters 65 can increase the flow resistance friction damage and also filter the pipeline impurities from entering the elastic resonant cavity 6.

[0037] The silencing inner flow channel 5 includes an inner flow channel wall 51, a support frame 53, and an elastic wall surface 54. Multiple support frames 53 are provided, spaced apart, and all are connected to the inner flow channel wall 51. The elastic wall surface 54 is fitted over the outer side of the support frames 53. The inner flow channel wall 51 has multiple openings 52 and small connecting holes 55 for water passage. The silencing inner flow channel 5 is divided into front and rear ends. The front end is the inner flow channel wall 51, used to install the elastic resonant cavity 6. The rear end consists of multiple support frames 53, with the elastic wall surface 54 installed on the outer side of each support frame 53. The diameter of the openings 52 is the same as the diameter 64 of the elastic resonant cavity 6. The elastic wall surface 54 is made of elastic material or a thin metal plate and covers the surface of the support frames 53, forming the silencing flow channel.

[0038] The mid-to-high frequency noise reduction section of the silencing inner flow channel 5 is mainly composed of a support frame 53 and an elastic wall 54. The support frame 53 forms a ring within the silencing inner flow channel 5, and also serves as a constraint boundary for the elastic wall 54. Flow noise within the pipe excites coupled vibration of the elastic wall 54. The bending vibration mode of the elastic wall 54 modulates the wall boundary impedance of the plane wave within the pipe, causing the plane wave propagation of noise within the pipe to be converted into higher-order wave loss. To control the broadband noise within the pipe from tens of hertz to several kilohertz, the length and circumferential spacing of the support frame 53, as well as the material and thickness of the elastic wall 54, can be changed. Higher-order sound waves penetrate the wall and enter the liquid cavity between the elastic wall 54 and the outer cylinder 2. The cavity thickness and boundary impedance constrain the coupled resonance of the elastic wall 54; increasing the cavity thickness increases the noise reduction of the coupled vibration of the elastic wall 54.

[0039] However, increasing the internal thickness inevitably leads to an excessively large silencer size, reducing its applicability. To address this issue, an acoustic impedance mismatch layer 7 is provided on the outer circumference of the elastic wall 54. The equivalent impedance of the acoustic impedance mismatch layer 7 is closer to that of air, which is preferable. However, considering the boundary sealing and pressure resistance issues between air and water media, the acoustic impedance mismatch layer 7 includes an elastomer 71, radial cavities 72, and a skin 73. Multiple radial cavities 72 are provided within the elastomer 71, and a skin 73 is provided on the surface of each radial cavity 72 to seal it and make it watertight. The acoustic impedance mismatch layer 7 is designed as a combination of the elastomer 71, radial cavities 72, and skin 73. This combination of radial cavities 72 and elastomer 71 results in a low-frequency acoustic impedance less than 5e5, enabling wideband silencing in the mid-to-low frequency range. The elastomer 71 is made of rubber or polyurethane, and its shape can be semi-circular or fully circular. The radial cavities 72 are cylindrical or conical cavities, allowing the elastomer 71 to contain gas. The circumferential skeleton 74 is made of rubber or thin composite material, and the interior of the circumferential skeleton 74 forms a circumferential air cavity.

[0040] The circumferential skeleton 74 is embedded in the elastomer 71. In the pump-driven pipeline, the pump has a head and the pipeline has a certain pressure. Some connecting holes 55 are opened on the inner flow channel wall to balance the pressure inside and outside the silencer and adapt to various pressure environments in the pipeline. Through the individual or combined control of the above three mechanisms, the low-frequency broadband and line spectrum noise of the pipeline can be effectively reduced.

[0041] Based on the frequency characteristics of the noise inside the pipeline, the frequency band and peak value of the line spectrum that need to be eliminated are determined. By analyzing the number of elastic resonant cavities 6 installed, the resonant frequency of the elastic resonant plate 63, and the length of the elastic wall 54, the length of the silencing inner flow channel 5 can be determined. The length of the silencing inner flow channel 5 is usually between 300mm and 500mm. If the installation space is limited, it can be appropriately reduced.

[0042] The dimensions of mounting flanges 1 and 3 are determined by the piping system interface and can be designed according to general specifications. However, to secure the acoustic impedance mismatch layer 7 within the cavity, a boss can be designed inside mounting flange 1. The inner diameter of the outer cylinder 2 is determined by the installation height of the elastic resonant cavity 6, and its thickness is determined based on the piping pressure. Since the silencing frequency of the elastic resonant cavity 6 is less affected by the cavity volume, the height of the elastic resonant cavity 6 can be controlled to around 5cm to meet the requirements for low-frequency silencing at tens of hertz.

[0043] The silencing inner flow channel 5 is generally made of a thin-walled pipe of the same material as the pipeline. Multiple elastic resonant cavities 6 are installed at one end, and an elastic wall surface 54 is installed at the other end. The two ends of the silencing inner flow channel 5 are fixed by positioning rings 4. To ensure pressure balance within the flow channel and the silencer cavity, and to ensure the cavity is filled with water, connecting holes 55 can be drilled at both ends of the silencing inner flow channel 5. This pressure balance also avoids the pressure resistance requirement of the elastic resonant cavities 6; only the four walls of the elastic resonant cavities 6 need to be rigid boundaries to satisfy the plane wave resonance within the cavity.

[0044] A cavity opening 52 is provided at a certain cross-section of the anechoic inner channel 5, and a single elastic resonant cavity 6 is installed there. Each elastic resonant cavity 6 generates sound absorption impedance at the cavity opening 52. Four or n resonant units are arranged in each cross-section, producing an n-fold sound absorption impedance effect. Arranging the same elastic resonant cavity 6 or different elastic resonant cavities 6 in multiple cross-sections can form a better sound absorption peak or sound absorption bandwidth.

[0045] To increase the acoustic impedance loss of the cavity diameter 64, the elastic resonant cavity 6 is divided into multiple small aperture 66, with a diameter of approximately centimeters. Millimeter-sized micro-apertures 65 are arranged between the small aperture 66. These micro-apertures 65 increase flow resistance and friction loss, and also filter impurities from the pipeline from entering the elastic resonant cavity 6.

[0046] Since the elastic resonant cavity 6 is installed inside the silencer cavity and is surrounded by water, the acoustic impedance of the wall boundary of the second cavity 62 has a significant impact on the sound absorption resonance. To reduce the penetration effect of underwater sound, an internal acoustic impedance mismatch layer 67 is designed on the wall of the second cavity 62. An inflatable airbag is optimal for the internal acoustic impedance mismatch layer 67, but considering pressure resistance, other shapes such as multiple cylindrical cavities, cones, or spheres can be arranged within the elastic material to make the equivalent acoustic impedance of the internal acoustic impedance mismatch layer 67 lower than 5e5.

[0047] One end of the silencing inner channel 5 can be cut into several supporting frames 53 using wire cutting or other methods, and an elastic wall 54 can be wrapped around the ribs. The elastic wall 54 can be made of high-loss damping rubber or polyurethane sleeves of a few millimeters, or a thin metal plate of a few tenths of a millimeter, or a combination of both. The specific thickness can be determined according to the silencing frequency. The elastic wall 54 has a low bending vibration frequency and good low-frequency silencing effect, but the silencing effect will be reduced in the mid-to-high frequency range.

[0048] An acoustic impedance mismatch layer 7 is arranged on the inner wall of the muffler cavity. The equivalent impedance of the acoustic impedance mismatch layer 7 is closer to that of air medium, which is better. However, considering the boundary sealing and pressure resistance issues between air medium and water medium, the first embodiment of the acoustic impedance mismatch layer 7 is a combination of elastomer 71, radial cavity 72, and skin 73. By combining radial cavity 72 and elastomer 71, its low-frequency acoustic impedance is less than 5e5, which can achieve mid-low frequency wideband noise reduction.

[0049] Another implementation of the acoustic impedance mismatch layer 7 is to use a circumferential skeleton 74 to form a circumferential cavity, or to use a composite material tube to pre-embed the composite material in the elastomer 71 for sealing.

[0050] The acoustic impedance mismatch layer 7 can be installed in the muffler in a full circular pattern, or it can be installed in the inner wall of the muffler in the form of two semicircles or multiple arcs.

[0051] The main silencing components, after assembly, consist of two main parts: the silencing inner flow channel 5 and the acoustic impedance mismatch layer 7. The acoustic impedance mismatch layer 7 is first installed and fixed inside the silencer, and then the silencing inner flow channel 5 is installed. The connection between the inner flow channel 5 and the mounting flange 1 constitutes the low-frequency broadband acoustic impedance mismatch silencer structure for the liquid pipeline.

[0052] In practical use, the acoustic impedance mismatch layer 7 is installed in the outer cylinder 2, the elastic resonant cavity 6 is installed on the silencing inner flow channel 5, and then the silencing inner flow channel 5 is installed in the outer cylinder 2, and fixed by the positioning ring 4. The pipeline fluid and noise are transmitted to the cross-section of the elastic resonant cavity 6 in the silencing inner flow channel 5 of the silencer. By combining multiple elastic resonant cavities 6 of the same or different sizes in parallel circumferentially and in series flow direction in the cross-section of the silencing inner flow channel 5, low-frequency broadband silencing can be achieved, with a low-frequency acoustic impedance of less than 5e5. It can also achieve mid-to-low frequency broadband silencing. This invention features a small structural size, a silencing frequency band covering several hertz to several kilohertz, and can be quantitatively optimized according to the peak values ​​of the pump shaft frequency, blade frequency, etc., achieving both broadband noise reduction and suppression of peak values. Furthermore, this invention can meet the noise reduction requirements of pipelines from low pressure to high pressure, and can also meet the noise reduction requirements of harsh environments such as high temperature and high radiation.

[0053] The above description is an explanation of the present invention and not a limitation thereof. The scope of the present invention is defined by the claims. Within the scope of protection of the present invention, any form of modification may be made.

Claims

1. A low-frequency broadband acoustic impedance mismatch silencer for liquid pipelines, characterized in that, include: outer cylinder (2); The silencing inner flow channel (5) is set inside the outer cylinder (2). The silencing inner flow channel (5) includes an inner flow channel wall (51) and a support frame (53). The inner flow channel wall (51) is located at the front end of the silencing inner flow channel (5), and the support frame (53) is located at the rear end of the silencing inner flow channel (5). Multiple support frames (53) are provided, and the multiple support frames (53) are spaced apart. All multiple support frames (53) are connected to the inner flow channel wall (51). The inner flow channel wall (51) is provided with a cavity opening (52), and the support frame (53) is covered with an elastic wall surface (54). An elastic resonant cavity (6) is set at the cavity opening (52) of the inner flow channel wall (51) for low-frequency broadband noise reduction; An acoustic impedance mismatch layer (7) is placed outside the elastic wall (54) for mid-to-low frequency wideband noise reduction; The elastic resonant cavity (6) includes a first cavity (61), a second cavity (62) and a cavity diameter (64). The first cavity (61) and the second cavity (62) are separated by an elastic resonant plate (63). An internal acoustic impedance mismatch layer (67) is provided in the elastic resonant cavity (6) to improve the coupling resonance of the elastic resonant plate (63).

2. The low-frequency broadband acoustic impedance mismatch silencer for liquid pipelines as described in claim 1, characterized in that: The acoustic impedance mismatch layer (7) includes an elastomer (71), a radial cavity (72) is provided inside the elastomer (71), and a skin (73) is provided on the surface of the radial cavity (72) for sealing the radial cavity (72).

3. The low-frequency broadband acoustic impedance mismatch silencer for liquid pipelines as described in claim 1, characterized in that: The acoustic impedance mismatch layer (7) includes an elastomer (71), in which a circumferential skeleton (74) is embedded, and a circumferential air cavity is provided in the circumferential skeleton (74).

4. A low-frequency broadband acoustic impedance mismatch silencer for liquid pipelines as described in claim 2 or 3, characterized in that: The acoustic impedance mismatch layer (7) is installed in a circular shape.

5. A low-frequency broadband acoustic impedance mismatch silencer for liquid pipelines as described in claim 4, characterized in that: One end of the outer cylinder (2) is provided with a mounting flange (1), and the other end of the outer cylinder (2) is provided with a flange (3). The mounting flange (1) has a boss inside the outer cylinder (2) for fixing the acoustic impedance mismatch layer (7) and fixing the sound-absorbing inner flow channel (5) by the positioning ring (4).

6. A low-frequency broadband acoustic impedance mismatch silencer for liquid pipelines as described in claim 1, characterized in that: A connecting hole (55) is provided on the inner flow channel wall (51) to ensure pressure balance in the flow channel and the silencer cavity.

7. A low-frequency broadband acoustic impedance mismatch silencer for liquid pipelines as described in claim 1, characterized in that: The cavity diameter (64) is provided with multiple small hole cavities (66), and the small hole cavities (66) are provided with micro-hole cavities (65) to increase flow resistance loss.

8. A low-frequency broadband acoustic impedance mismatch silencer for liquid pipelines as described in claim 7, characterized in that: The size of the small aperture (66) is in the centimeter range, and the size of the micro-aperture (65) is in the millimeter range.

9. A low-frequency broadband acoustic impedance mismatch silencer for liquid pipelines as described in claim 1, characterized in that: The multiple cross sections of the silencing inner flow channel (5) are arranged with elastic resonant cavities (6).

10. A low-frequency broadband acoustic impedance mismatch silencer for a liquid pipeline as described in claim 1, characterized in that: Each cross section of the silencing inner flow channel (5) is arranged with multiple elastic resonant cavities (6).

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