Pipeline high-frequency silencer based on acoustic mode modulation and perforated pipe and design method thereof

Abstract

The invention discloses a pipeline high-frequency silencer based on acoustic mode modulation and a perforated pipe. The pipeline high-frequency silencer comprises a shell, and the interior of the shell is connected with a cylindrical inner pipe through a plurality of partition plates; the partition plates are parallel to the axial direction of the inner pipe and evenly arranged in the circumferential direction of the inner pipe. The partition plates divide an annular cavity formed between the shell and the inner pipe into a plurality of sub-cavities of the same size. Flanges are connected to two ends of the shell. The invention further discloses a design method of the pipeline high-frequency silencer based on acoustic mode modulation and the perforated pipe. The design method comprises a perforated design method of the inner layer of the shell and / or the inner layer of the inner pipe and a design method of the partition plate. According to the pipeline high-frequency silencer based on acoustic mode modulation and the perforated pipe, the problem that in the prior art, a sound absorption material which is prone to losing efficacy and harms human health is used for achieving high-frequency noise suppression is solved. High-frequency noise elimination is achieved through the partition plate and the perforated pipe, the structure is simple, and disassembly and replacement are convenient.

Description

Technical Field

[0001] The present invention belongs to the technical field of pipeline high-frequency noise suppression devices, and particularly relates to a pipeline high-frequency muffler based on acoustic mode modulation and perforated pipes. The present invention also relates to a design method for the above-mentioned pipeline high-frequency muffler based on acoustic mode modulation and perforated pipes. Background Art

[0002] Pipelines are widely used in fields such as oil and gas transportation, automobiles, nuclear power, and ships. Currently, with the widespread use of impeller machinery such as turbocharged engines, gas turbines, centrifugal fans, and axial fans, the medium and high-frequency noise presented inside or at the outlet of the pipeline is significant, which not only affects environmental comfort and the health of surrounding personnel, but may also cause the equipment to fail due to acoustic fatigue in severe cases.

[0003] Currently, the suppression of high-frequency noise in pipelines mainly uses resistive muffling structures containing sound-absorbing materials. However, they are prone to failure in harsh working conditions such as high temperature, high humidity, dust, oil mist, and corrosive gases. At the same time, the fibers of the sound-absorbing materials are very fine and can easily enter the human body through the respiratory tract in high-speed airflows, endangering human health. Summary of the Invention

[0004] The purpose of the present invention is to provide a pipeline high-frequency muffler based on acoustic mode modulation and perforated pipes, which solves the problem of using sound-absorbing materials that are prone to failure and harmful to human health in the prior art to achieve high-frequency noise suppression. The present invention uses partitions and perforated pipes to achieve high-frequency noise reduction, with a simple structure and convenient disassembly and replacement.

[0005] The technical solution adopted by the present invention is that a pipeline high-frequency muffler based on acoustic mode modulation and perforated pipes includes a housing, and a cylindrical inner pipe is connected inside the housing through a plurality of partitions; the plurality of partitions are parallel to the axial direction of the inner pipe and are evenly arranged along the circumferential direction of the inner pipe, and the plurality of partitions divide the annular cavity formed between the housing and the inner pipe into a plurality of sub-cavities of the same size; flanges are connected to both ends of the housing.

[0006] The characteristics of the present invention also lie in that:

[0007] The housing is a double-layer structure; the inner pipe is a double-layer cylindrical structure, in the shape of an airfoil-like "round in the front and pointed in the back"; the inner layers of the housing and the inner pipe are both vertically divided into two sections in the axial direction, with a plurality of micro-holes evenly distributed in one section and a plurality of ordinary holes evenly distributed in the other section; the micro-holes and the ordinary holes are evenly distributed.

[0008] The aperture range of the micro-holes is 0.1 mm to 1 mm, and the aperture range of the ordinary holes is 1 mm to 5 mm; the perforation rates of the micro-holes and the ordinary holes are both 0.1% to 15%.

[0009] The diameter of the part of the housing in contact with the partition is larger than the diameters of both ends of the housing.

[0010] The partition is a rectangular metal plate that connects the inner layer of the outer shell and the outer layer of the inner tube.

[0011] The number of partitions is at least 3, and the length of the partition is equal to the length of the perforated part of the inner layer of the inner tube.

[0012] Another technical solution adopted by the present invention is a design method of a high-frequency duct muffler based on acoustic mode modulation and perforated tubes, including a perforation design method for the inner layer of the outer shell and / or the inner layer of the inner tube and a design method for the partition.

[0013] Another feature of the technical solution of the present invention is that:

[0014] The perforation design method for the inner layer of the outer shell and / or the inner layer of the inner tube is designed with the transmission loss as an index, specifically:

[0015] For a perforated tube with a length of l p , the sound pressure p1(0), the sound particle velocity u1(0) at the inlet x = 0, and the sound pressure p1(l p ), the sound particle velocity u1(l p ) at the outlet x = l p ) have the following relationship:

[0016]

[0017] In the formula, ρ0 and c are the medium density and the sound speed respectively, and [T] is the transfer matrix;

[0018] When the airflow parameters and the cross-sectional area at the inlet and outlet sections of the perforated tube are the same, the transmission loss TL of the perforated tube is:

[0019]

[0020] The values of the elements of the transfer matrix [T] are expressed as:

[0021]

[0022] In the formula, [R] is a 4×4 square matrix, that is l c1 and l c2 respectively represent the axial lengths of the unperforated parts at both ends of the muffler; k = ωc is the wave number, ω = 2πf is the angular frequency, and f represents the frequency; is the imaginary unit;

[0023] The square matrix [R] is obtained by transforming another 4×4 operator square matrix [Q], which is expressed as:

[0024] [R] = [Q(0)][Q(l p )] -1 (4);

[0025] The square matrix [Q(x)] is obtained through the following process:

[0026] For the outer shell or the inner tube, its inner layer, i.e., the perforated wall, divides it into two parts: the perforated tube and the expansion cavity. The sound pressure p1 inside the perforated tube and the sound pressure p2 inside the expansion cavity satisfy the following relationship:

[0027]

[0028] In the formula, D is the partial derivative operator; α1 to α8 are coefficients, expressed as follows:

[0029]

[0030]

[0031] In the formula, M1 and M2 respectively represent the average gas flow Mach numbers inside the perforated tube and inside the expansion cavity; the inner diameter of the perforated tube is d p , the outer diameter of the perforated tube is d pe , the outer diameter of the perforated outer shell is d r ; ξ is the average acoustic impedance rate of the perforated tube. For a perforated tube containing micropores and ordinary holes, it is obtained by parallel processing of the acoustic impedance rates of two sections:

[0032]

[0033] In the formula: Q1 and Q2, φ1 and φ2 respectively represent the axial length ratios and perforation rates of the ordinary hole perforation section and the micropore perforation section;

[0034] For the ordinary hole perforation section, without considering the transverse flow in the holes, the formula for the acoustic impedance rate ξ1 under the action of the average flow is:

[0035]

[0036] In the formula, μ is the dynamic viscosity of the fluid medium, t w is the wall thickness of the perforated tube, d h1 is the aperture of the ordinary hole;

[0037] For the micropore perforation section, the formula for the acoustic impedance rate ξ2 is:

[0038]

[0039] In the formula, is the perforation constant; η is the viscosity coefficient of the medium; d h2 is the aperture of the micropore; J0 and J1 are the zero-order and first-order Bessel functions respectively; Q is a semi-empirical constant, taking 0.15; F γ is the influence coefficient of gas flow on the acoustic reactance of the perforated tube, expressed as:

[0040]

[0041] Equation (5) is a coupled equation. The matrix eigenvalue decomposition method needs to be used to decouple the equations. The coefficient matrix [B] is introduced:

[0042]

[0043] Performing eigenvalue decomposition on the matrix [B], 4 eigenvectors and the corresponding 4 eigenvalues λ i , i = 1 to 4, are obtained. Let [Ψ] be a 4×4 square matrix composed of the eigenvectors of the matrix [B], and we get:

[0044]

[0045] After establishing the theoretical model of the transmission loss of the perforated pipe using the above process, the variables are then optimized based on the genetic algorithm to maximize the transmission loss. The average transmission loss within the calculated frequency range is defined as the fitness function obj:

[0046]

[0047] where: x is the row vector of the independent variable of the objective function; f1 and f2 are the lower and upper limits of the calculated frequency; Δf is the calculated frequency step size;

[0048] The variables include the micropore diameter d h1 and the ordinary pore diameter d h2 , the ordinary pore perforation rate φ1 and the micropore perforation rate φ2, the thickness t w and the length l p , and the constraint conditions for each variable are as follows: 0.1 mm ≤ d h1 ≤ 1 mm, 1 mm ≤ d h2 ≤ 5 mm, 0.001 ≤ φ1, φ2 ≤ 0.15, t w and l p are determined according to the on-site space size and processing capacity.

[0049] The design method of the baffle is as follows:

[0050] At the highest noise reduction frequency f max , the corresponding maximum inner diameter R max of the circular pipe is obtained by inverse calculation from the plane wave cut-off frequency formula of the circular cross-section pipe:

[0051]

[0052] When designing the baffle, each annular sector sub-cavity is regarded as a circular pipe with the same size, and the equivalent radius of the circular pipe is determined according to the principle of equal area, ensuring that both the equivalent radius and the inner perforated pipe radius do not exceed the maximum inner diameter R max of the circular pipe.

[0053] The beneficial effects of the present invention are:

[0054] The high-frequency muffler for pipelines based on acoustic mode modulation and perforated pipes of the present invention uses a partition plate to change the structure of the inner cavity of the pipeline, modulates the high-order acoustic modes in the original pipeline into plane waves in the sub-channels, and adopts a combined hole form of micro-holes and ordinary holes, effectively reducing the high-frequency aerodynamic noise of the pipeline and achieving the suppression of high-frequency noise in the pipeline. At the same time, the device of the present invention has a simple structure, is convenient to disassemble, and has a wide range of usage scenarios. Brief Description of the Drawings

[0055] Figure 1 is a schematic structural diagram of the high-frequency muffler for pipelines based on acoustic mode modulation and perforated pipes of the present invention;

[0056] Figure 2 is a sectional view of the high-frequency muffler for pipelines based on acoustic mode modulation and perforated pipes of the present invention;

[0057] Figure 3 is a sectional view at the partition plate of the high-frequency muffler for pipelines based on acoustic mode modulation and perforated pipes of the present invention;

[0058] Figure 4 is a plan view of the outer shell and the inner pipe of the high-frequency muffler for pipelines based on acoustic mode modulation and perforated pipes of the present invention.

[0059] In the figure: 101, outer shell; 102, inner pipe; 103, partition plate; 104, flange. Detailed Description of the Invention

[0060] The present invention will be described in detail below in conjunction with the drawings and specific embodiments.

[0061] The high-frequency muffler for pipelines based on acoustic mode modulation and perforated pipes of the present invention, as Figure 1 shown, includes an outer shell 101, and a cylindrical inner pipe 102 is connected inside the outer shell 101 through a plurality of partition plates 103; the plurality of partition plates 103 are axially parallel to the inner pipe 102 and are evenly arranged along the circumferential direction of the inner pipe 102, and the plurality of partition plates 103 divide the annular cavity formed between the outer shell 101 and the inner pipe 102 into a plurality of sub-cavities of the same size; both ends of the outer shell 101 are connected with flanges 104, and the setting of the flanges 104 facilitates the connection and disassembly of the muffler of the present invention with the pipeline.

[0062] As Figure 2 shown, the outer shell 101 is of a double-layer structure, and the diameter of the part of the outer shell 101 in contact with the partition plate 103 is larger than the diameters at both ends to ensure that the flow area remains unchanged when the fluid flows through the muffler, as Figure 4As shown in the figure. There is a certain distance between the inner layer and the outer layer of the outer shell 101. The inner layer of the outer shell 101 is perforated. Specifically, it is divided into two sections in the vertical axial direction. In one section, a number of micro-holes are evenly distributed, and in the other section, a number of ordinary holes are evenly distributed; the micro-holes and the ordinary holes are evenly distributed. The aperture range of the micro-holes is 0.1 mm to 1 mm, and the aperture range of the ordinary holes is 1 mm to 5 mm; the perforation rates of both the micro-holes and the ordinary holes are 0.1% to 15%. The inner layer perforation treatment is used to reduce the high-frequency noise of the pipeline. The advantage of the combined holes compared with the single holes is that a better broadband effect can be obtained.

[0063] The inner pipe 102 is a double-layer cylindrical structure, adopting an airfoil-like structure of "round in the front and pointed in the back", and its inner layer adopts the same perforation treatment as the inner layer of the outer shell 101. When the fluid passes through the pipeline mutation, part of the energy will be converted into heat energy or other forms of energy, resulting in energy loss. At the same time, a series of eddy currents will be formed at the mutation. These eddy currents interact with each other during the flow process, generating secondary noise. The streamline treatment of the inner pipe 102 is to reduce the flow loss at the pipeline mutation and avoid generating secondary noise.

[0064] The partition plate 103 is a rectangular metal plate, used to connect the inner layer of the outer shell 101 and the outer layer of the inner pipe 102, as Figure 3 shown in the figure. The length of the partition plate 103 is equal to the length of the perforated part of the inner layer of the inner pipe 102, and the number is at least set to 3, which is specifically determined by the target noise reduction frequency band and the pipeline noise cut-off frequency. In the high-frequency range, the original pipeline contains multiple high-order acoustic modes. The partition plates 103 are evenly distributed along the circumferential direction of the inner pipe 102, and the cavity in the outer shell 101 is divided into multiple sub-cavities, including a central cavity and multiple peripheral cavities. The cross-sectional area of the sub-cavities is smaller than that of the original cavity, and the cut-off frequency becomes larger. The high-frequency noise in the target frequency band is all plane waves when passing through the sub-cavities, thereby improving the noise reduction effect of the perforated pipe and effectively suppressing the noise in a specific high-frequency band.

[0065] Among them, the perforation design method of the inner layer of the outer shell 101 and / or the inner layer of the inner pipe 102 is designed with the transmission loss as an index. Specifically:

[0066] For a perforated pipe with a length of l p , the sound pressure p1(0), the sound particle velocity u1(0) at the inlet x = 0, and the sound pressure p1(l p ), the sound particle velocity u1(l p ) at the outlet x = l p ) have the following relationship:

[0067]

[0068] In the formula, ρ0 and c are the medium density and the sound speed respectively, and [T] is the transfer matrix;

[0069] When the airflow parameters and cross-sectional areas at the inlet and outlet of the perforated pipe are the same, the transmission loss TL of the perforated pipe is:

[0070]

[0071] The values of the elements of the transfer matrix [T] are expressed as:

[0072]

[0073] In the formula, [R] is a 4×4 square matrix, that is l c1 and l c2 respectively represent the axial lengths of the unperforated parts at both ends of the muffler; k = ωc is the wave number, ω = 2πf is the angular frequency, and f represents the frequency; is the imaginary unit;

[0074] The square matrix [R] is obtained by transforming another 4×4 operator square matrix [Q], expressed as:

[0075] [R] = [Q(0)][Q(l p )] -1 (4);

[0076] The square matrix [Q(x)] is obtained as follows:

[0077] For the outer shell 101 or the inner pipe 102, its inner layer, i.e., the perforated wall, divides it into a perforated pipe and an expansion chamber. By coupling the continuity equation, momentum equation, and gas isentropic relation inside the perforated pipe and the expansion chamber, it is obtained that the sound pressure p1 inside the perforated pipe and the sound pressure p2 inside the expansion chamber satisfy the following relationship:

[0078]

[0079] In the formula, D is the partial derivative operator; α1 to α8 are coefficients, expressed as follows:

[0080]

[0081]

[0082] In the formula, M1 and M2 respectively represent the average airflow Mach numbers inside the perforated pipe and inside the expansion chamber; the inner diameter of the perforated pipe is d p , the outer diameter of the perforated pipe is d pe , and the outer diameter of the perforated outer shell is d r ; ξ is the average acoustic impedance rate of the perforated pipe. For a perforated pipe containing micropores and ordinary holes, it is obtained by parallel processing of the acoustic impedance rates of two sections:

[0083]

[0084] Where: Q1 and Q2, φ1 and φ2 respectively represent the axial length ratio and perforation rate of the perforated section of the ordinary hole and the micro-hole perforated section;

[0085] For the perforated section of the ordinary hole, without considering the transverse flow in the hole, the formula for the acoustic impedance rate ξ1 under the action of the average flow is:

[0086]

[0087] Where μ is the dynamic viscosity of the fluid medium, t w is the wall thickness of the perforated pipe, d h1 is the aperture of the ordinary hole;

[0088] For the micro-hole perforated section, the formula for the acoustic impedance rate ξ2 is:

[0089]

[0090] Where is the perforation constant; η is the viscosity coefficient of the medium; d h2 is the aperture of the micro-hole; J0 and J1 are the zero-order and first-order Bessel functions respectively; Q is a semi-empirical constant, taking 0.15; F γ is the influence coefficient of gas flow on the acoustic reactance of the perforated pipe, expressed as:

[0091]

[0092] Equation (5) is a coupling equation. The matrix eigenvalue decomposition method needs to be used to decouple the system of equations. The coefficient matrix [B] is introduced:

[0093]

[0094] Performing eigenvalue decomposition on the matrix [B], 4 eigenvectors and the corresponding 4 eigenvalues λ i , i = 1 to 4, let be the 4×4 square matrix composed of the eigenvectors of the matrix [B], and we get:

[0095]

[0096] After establishing the theoretical model of the transmission loss of the perforated pipe using the above process, the variables are optimized based on the genetic algorithm to maximize the transmission loss. The average transmission loss within the calculated frequency range is defined as the fitness function obj:

[0097]

[0098] Where: x is the row vector of the independent variable of the objective function; f1 and f2 are the lower and upper limits of the calculated frequency; Δf is the calculated frequency step;

[0099] The optimizable variables include six variables, specifically the micropore diameter d h1 and the ordinary pore diameter d h2 , the perforation rate φ1 of ordinary pores and the perforation rate φ2 of micropores, the thickness t of the perforated pipe w and the length l p . The constraint conditions for each variable are as follows: 0.1mm ≤ d h1 ≤ 1mm, 1mm ≤ d h2 ≤ 5mm, 0.001 ≤ φ1, φ2 ≤ 0.15, t w and l p are determined according to the on-site space size and processing capacity.

[0100] The design method of the partition 103 is as follows:

[0101] At the highest noise reduction frequency f max , the corresponding maximum inner diameter R of the circular pipe is inversely calculated from the plane wave cut-off frequency formula of the circular cross-section pipe max :

[0102]

[0103] When designing the partition, each ring-sector sub-cavity is regarded as a circular pipe with the same size, and the equivalent radius of the circular pipe is determined according to the principle of equal area, ensuring that both the equivalent radius and the inner radius of the perforated pipe do not exceed the maximum inner diameter R of the circular pipe max .

[0104] Example 1

[0105] This example provides a high-frequency muffler for pipes based on acoustic mode modulation and perforated pipes. As Figures 1 to 4 shown, there is a housing 101, and a cylindrical inner pipe 102 is connected inside the housing 101 through a number of partitions 103; the number of partitions 103 is axially parallel to the inner pipe 102 and evenly arranged along the circumferential direction of the inner pipe 102. The number of partitions 103 divides the annular cavity formed between the housing 101 and the inner pipe 102 into several sub-cavities of the same size; flanges 104 are connected to both ends of the housing 101.

[0106] Example 2

[0107] On the basis of Example 1, the housing 101 is of a double-layer structure; the diameter of the part of the housing 101 in contact with the partition 103 is larger than the diameters of both ends of the housing 101. The inner pipe 102 is of a double-layer cylindrical structure, in the shape of a wing-like "front-round and rear-pointed"; the inner layer of the housing 101 and the inner layer of the inner pipe 102 are both vertically axially divided into two sections of regions. In one section of the region, a number of micropores are evenly distributed, and in the other section of the region, a number of ordinary pores are evenly distributed; the micropores and ordinary pores are evenly distributed. The pore diameter range of the micropores is 0.1mm to 1mm, and the pore diameter range of the ordinary pores is 1mm to 5mm; the perforation rates of the micropores and ordinary pores are both 0.1% to 15%.

[0108] Example 3

[0109] On the basis of Example 2, the partition plate 103 is a rectangular metal plate, connecting the inner layer of the outer shell 101 and the outer layer of the inner tube 102. The number of partition plates 103 is at least 3, and the length of the partition plate 103 is equal to the length of the inner perforated part of the inner tube 102.

[0110] Example 4

[0111] This example provides a design method for a high-frequency muffler for pipelines based on acoustic mode modulation and perforated tubes, including a perforation design method for the inner layer of the outer shell 101 and / or the inner layer of the inner tube 102 and a design method for the partition plate 103.

[0112] Example 5

[0113] On the basis of Example 4, the perforation design method for the inner layer of the outer shell 101 and / or the inner layer of the inner tube 102 is designed with the transmission loss as an index. Specifically:

[0114] For a perforated tube with a length of l p , the sound pressure p1(0), the sound particle velocity u1(0) at the inlet x = 0, and the sound pressure p1(l p ), the sound particle velocity u1(l p ) at the outlet x = l p ) have the following relationship:

[0115]

[0116] In the formula, ρ0 and c are the medium density and the sound speed respectively, [T] is the transfer matrix;

[0117] When the airflow parameters and the cross-sectional area at the inlet and outlet sections of the perforated tube are the same, the transmission loss TL of the perforated tube is:

[0118]

[0119] The values of the elements of the transfer matrix [T] are expressed as:

[0120]

[0121] In the formula, [R] is a 4×4 square matrix, that is l c1 and l c2 respectively represent the axial lengths of the unperforated parts at both ends of the muffler; k = ωc is the wave number, ω = 2πf is the angular frequency, and f represents the frequency; is the imaginary unit;

[0122] The square matrix [R] is obtained by transforming another 4×4 operator square matrix [Q], expressed as:

[0123] [R] = [Q(0)][Q(l p )] -1 (4);

[0124] The square matrix [Q(x)] is obtained through the following process:

[0125] For the outer shell 101 or the inner tube 102, its inner layer, i.e., the perforated wall, divides it into two parts: a perforated tube and an expansion cavity. The sound pressure p1 inside the perforated tube and the sound pressure p2 inside the expansion cavity satisfy the following relationship:

[0126]

[0127] In the formula, D is the partial derivative operator; α1 to α8 are coefficients, expressed as follows:

[0128]

[0129]

[0130] In the formula, M1 and M2 respectively represent the average flow Mach numbers inside the perforated tube and inside the expansion cavity; the inner diameter of the perforated tube is d p , the outer diameter of the perforated tube is d pe , the outer diameter of the perforated outer shell is d r ; ξ is the average acoustic impedance rate of the perforated tube. For a perforated tube containing micropores and ordinary holes, it is obtained by parallel processing of the acoustic impedance rates of two sections:

[0131]

[0132] In the formula: Q1 and Q2, φ1 and φ2 respectively represent the axial length ratios and perforation rates of the ordinary hole perforation section and the micropore perforation section;

[0133] For the ordinary hole perforation section, without considering the transverse flow in the holes, the formula for the acoustic impedance rate ξ1 under the action of the average flow is:

[0134]

[0135] In the formula, μ is the dynamic viscosity of the fluid medium, t w is the wall thickness of the perforated tube, d h1 is the aperture of the ordinary hole;

[0136] For the micropore perforation section, the formula for the acoustic impedance rate ξ2 is:

[0137]

[0138] In the formula, is the perforation constant; η is the viscosity coefficient of the medium; d h2is the micropore diameter; J0 and J1 are the zero-order and first-order Bessel functions respectively; Q is a semi-empirical constant, taking 0.15; F γ is the influence coefficient of gas flow on the acoustic reactance of the perforated pipe, expressed as:

[0139]

[0140] Equation (5) is a coupling equation. The matrix eigenvalue decomposition method needs to be used to decouple the equations. The coefficient matrix [B] is introduced:

[0141]

[0142] Performing eigenvalue decomposition on the matrix [B], 4 eigenvectors and the corresponding 4 eigenvalues λ i , i = 1 to 4, let [Ψ] be the 4×4 square matrix composed of the eigenvectors of the matrix [B], and we get:

[0143]

[0144] After establishing the theoretical model of the transmission loss of the perforated pipe using the above process, the variables are then optimized based on the genetic algorithm to maximize the transmission loss. The average transmission loss within the calculated frequency range is defined as the fitness function obj:

[0145]

[0146] In the formula: x is the row vector of the independent variable of the objective function; f1 and f2 are the lower and upper limits of the calculated frequency; Δf is the calculated frequency step size;

[0147] The variables include the micropore diameter d h1 and the ordinary hole diameter d h2 , the ordinary hole perforation rate φ1 and the micropore perforation rate φ2, the thickness t w and the length l p ; The constraint conditions for each variable are as follows: 0.1mm ≤ d h1 ≤ 1mm, 1mm ≤ d h2 ≤ 5mm, 0.001 ≤ φ1, φ2 ≤ 0.15, t w and l p are determined according to the on-site space size and processing capacity.

[0148] Example 6

[0149] Based on Example 5, the design method of the partition 103 is specifically:

[0150] At the highest noise reduction frequency f max , the corresponding maximum circular pipe inner diameter R max is inversely calculated from the circular cross-section pipe plane wave cut-off frequency formula:

[0151]

[0152] When designing the partition plate, each annular sector sub-chamber is regarded as a circular tube with the same size, and the equivalent radius of the circular tube is determined according to the principle of equal area, ensuring that both the equivalent radius and the radius of the inner perforated tube do not exceed the inner diameter R of the largest circular tube max 。

Claims

1. A high frequency pipe muffler based on acoustic mode modulation and perforated pipe, characterized in that: The invention comprises an outer shell (101), wherein the inner part of the outer shell (101) is connected to a cylindrical inner tube (102) via a plurality of partitions (103); the plurality of partitions (103) are axially parallel to the inner tube (102) and are evenly arranged along the circumference of the inner tube (102); the plurality of partitions (103) divide the annular cavity formed between the outer shell (101) and the inner tube (102) into a plurality of sub-cavities of the same size; and flanges (104) are connected to both ends of the outer shell (101).

2. The pipeline high-frequency silencer based on acoustic mode modulation and perforated pipe according to claim 1 is characterized in that: The outer shell (101) is a double-layer structure; the inner tube (102) is a double-layer cylindrical structure, which is an airfoil-like shape with a "round front and pointed rear" shape; the inner layer of the outer shell (101) and the inner layer of the inner tube (102) are both divided into two regions perpendicular to the axial direction, one region is evenly distributed with a plurality of micropores, and the other region is evenly distributed with a plurality of ordinary pores; the micropores and ordinary pores are evenly distributed.

3. The pipeline high-frequency silencer based on acoustic mode modulation and perforated pipe according to claim 2 is characterized in that: The aperture range of the micropores is 0.1 mm to 1 mm, and the aperture range of the common holes is 1 mm to 5 mm; the perforation rates of the micropores and the common holes are both 0.1% to 15%.

4. The pipeline high-frequency silencer based on acoustic mode modulation and perforated pipe according to claim 1 is characterized in that: The diameter of the contact portion of the shell (101) and the partition (103) is larger than the diameters of both ends of the shell (101).

5. The pipeline high-frequency silencer based on acoustic mode modulation and perforated pipe according to claim 1 is characterized in that: The partition (103) is a rectangular metal plate, connecting the inner layer of the outer shell (101) and the outer layer of the inner tube (102).

6. The pipeline high-frequency silencer based on acoustic mode modulation and perforated pipe according to claim 1 is characterized in that: The number of the partitions (103) is at least 3, and the length of the partitions (103) is equal to the length of the inner layer perforated portion of the inner tube (102).

7. The design method of a pipeline high-frequency silencer based on acoustic mode modulation and perforated pipe according to any one of claims 1 to 6, characterized in that: The invention comprises a perforation design method of the inner layer of the outer shell (101) and / or the inner layer of the inner tube (102) and a design method of the partition (103).

8. The design method of a pipeline high-frequency silencer based on acoustic mode modulation and perforated pipe according to claim 7 is characterized in that: The perforation design method of the inner layer of the outer shell (101) and / or the inner layer of the inner tube (102) is designed based on the transmission loss as an index, specifically: For a length of l p The perforated tube has the following characteristics: the sound pressure p1(0) at the inlet x=0, the sound particle velocity u1(0) ​​and the outlet x=l p The sound pressure p1(l p ), sound particle speed u1(l p ) has the following relationship: Where ρ0 and c are the medium density and sound speed respectively, [T] is the transfer matrix; When the air flow parameters and cross-sectional area of ​​the perforated tube inlet and outlet sections are consistent, the perforated tube transmission loss TL is: The values ​​of each element of the transfer matrix [T] are expressed as: In the formula, [R] is a 4×4 square matrix, that is l c1 and l c2 They represent the axial lengths of the unperforated parts at both ends of the muffler respectively; k = ωc is the wave number, ω = 2πf is the angular frequency, and f represents the frequency; is an imaginary unit; The square matrix [R] is transformed from another 4×4 operator square matrix [Q] and is expressed as: [R]=[Q(0)][Q(l p )] -1 (4); The square matrix [Q(x)] is obtained as follows: For the outer shell (101) or the inner tube (102), the inner layer, i.e., the perforated wall, divides it into two parts, namely, the perforated tube and the expansion cavity. The sound pressure p1 inside the perforated tube and the sound pressure p2 inside the expansion cavity satisfy the following relationship: Where D is the partial derivative operator; α1~α8 are coefficients, expressed as follows: Where M1 and M2 represent the average airflow Mach numbers in the perforated tube and the expansion chamber, respectively; the inner diameter of the perforated tube is d p , the outer diameter of the perforated tube is d pe , the outer diameter of the perforated shell is d r ξ is the average acoustic impedance of the perforated tube. For a perforated tube containing micropores and ordinary holes, the following is obtained by parallel processing of the two acoustic impedances: Where: Q1 and Q2, φ1 and φ2 represent the axial length proportion and perforation rate of the common hole perforation section and micro hole perforation section respectively; For the perforated section of the common hole, ignoring the lateral flow in the hole, the formula of the acoustic impedance ratio ξ1 under the action of the average flow is: Where μ is the dynamic viscosity of the fluid medium, t w is the wall thickness of the perforated tube, d h1 is the normal hole diameter; For the micro-hole perforated section, the acoustic impedance ξ2 formula is: In the formula, is the perforation constant; η is the viscosity coefficient of the medium; d h2 is the micropore diameter; J0 and J1 are zero-order and first-order Bessel functions, respectively; Q is a semi-empirical constant, which is 0.15; F γ is the influence coefficient of gas flow on the acoustic reactance of the perforated pipe, expressed as: Equation (5) is a coupled equation, and the matrix eigenvalue decomposition method is required to decouple the equation group and introduce the coefficient matrix [B]: Performing eigenvalue decomposition on the matrix [B], we can obtain 4 eigenvectors and the corresponding 4 eigenvalues ​​λ i , i = 1 ~ 4, let [Ψ] be the 4 × 4 square matrix composed of the eigenvectors of the matrix [B], and we get: After the perforated pipe transmission loss theoretical model is established using the above process, the genetic algorithm is used to optimize the variables to maximize the transmission loss, and the average transmission loss within the calculation frequency range is defined as the fitness function obj: Where: x is the row vector of the independent variable of the objective function; f1 and f2 are the lower and upper limits of the calculation frequency; Δf is the calculation frequency step; The variables include the micropore diameter d h1 and the common hole diameter d h2 , ordinary hole perforation rate φ1 and micro hole perforation rate φ2, perforated tube thickness t w and length l p ; The constraints of each variable are as follows: 0.1mm≤d h1 ≤1mm、1mm≤d h2 ≤5mm, 0.001≤φ1,φ2≤0.15, t w and l p Determined according to the site space size and processing capacity.

9. The design method of a pipeline high-frequency silencer based on acoustic mode modulation and perforated pipe according to claim 8 is characterized in that: The design method of the partition (103) is specifically as follows: At the highest noise reduction frequency f max Under this condition, the corresponding maximum inner diameter R of the circular pipe can be obtained by inversely calculating the cutoff frequency formula of the plane wave of the circular cross-section pipe. max : When designing the partition, each annular sector cavity is regarded as a circular tube of the same size. The equivalent radius of the circular tube is determined according to the principle of area consistency, ensuring that the equivalent radius and the radius of the inner perforated tube do not exceed the maximum inner diameter R of the circular tube. max .

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