Pipeline high-frequency reactive muffler based on Helmholtz resonator and design method thereof

Abstract

The pipeline high-frequency reactive muffler based on the Helmholtz resonators comprises an outer pipeline, the interior of the outer pipeline is connected with a circular pipe through a plurality of perforated plate cavity structures, and the outer pipeline and the circular pipe form a concentric nested structure; the perforated plate cavity structures are parallel to the axis of the circular pipe and are uniformly arranged in the circumferential direction of the circular pipe, and an annular cavity formed between the outer pipeline and the circular pipe is divided into a plurality of sub-cavities with the same size by the perforated plate cavity structures; two ends of the outer pipeline are connected with flanges. The invention further discloses a design method of the pipeline high-frequency reactive muffler based on the Helmholtz resonator. The pipeline high-frequency reactive muffler based on the Helmholtz resonator can effectively reduce high-frequency noise of the pipeline.

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 reactive muffler based on a Helmholtz resonator and a design method thereof. Background Art

[0002] As the core carrier of fluid transmission, pipeline systems are widely used in industrial fields such as automobile manufacturing, chemical production, and building heating and ventilation. However, the accompanying noise pollution problem is becoming increasingly prominent. Among them, high-frequency noise (above 2000 Hz) is prone to generate complex acoustic-vibration coupling effects with pipeline systems due to its wide frequency domain distribution and low attenuation rate. When the structural resonance frequency caused by fluid excitation coincides with the main frequency of the noise, it can accelerate material fatigue damage and shorten the service life of the pipeline under mild working conditions; in extreme cases, the mechanical vibration caused by resonance will significantly reduce the measurement accuracy of instruments and even induce chain failures of key equipment such as pump-valve systems and pressure vessels. Workers in industrial sites are exposed to the high-frequency noise environment of pipeline systems for a long time, which can cause noise-induced hearing damage and pathological changes in the non-auditory system. The current high-frequency noise control mainly relies on porous resistive sound-absorbing materials (such as melamine foam or glass fiber cotton), and its noise reduction mechanism depends on the viscous-thermal dissipation effect, with problems such as poor environmental tolerance, risk of material degradation, and potential for secondary pollution. To address the above problems, a reactive muffler device can be integrated at key nodes of the pipeline system, which has the characteristics of controllable acoustic performance, strong environmental adaptability, and safety throughout the life cycle. Summary of the Invention

[0003] The purpose of the present invention is to provide a pipeline high-frequency reactive muffler based on a Helmholtz resonator, which can effectively reduce pipeline high-frequency noise.

[0004] Another purpose of the present invention is to provide a design method for the above-mentioned pipeline high-frequency reactive muffler based on a Helmholtz resonator.

[0005] The technical solution adopted by the present invention is that a pipeline high-frequency reactive muffler based on a Helmholtz resonator includes an outer pipeline, and a circular pipe is connected inside the outer pipeline through a plurality of perforated plate cavity structures, and the outer pipeline and the circular pipe form a concentric nested structure; the plurality of perforated plate cavity structures are parallel to the axis of the circular pipe and are evenly arranged along the circumferential direction of the circular pipe, and the plurality of perforated plate cavity structures divide the annular cavity formed between the outer pipeline and the circular pipe into a plurality of sub-cavities of the same size; flanges are connected to both ends of the outer pipeline.

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

[0007] A plurality of Helmholtz resonators are arranged along the length direction on the inner wall of the outer pipeline and the inner wall of the circular pipe; the Helmholtz resonators are designed in parallel on the inner wall of the outer pipeline and the inner wall of the circular pipe to form a Helmholtz resonator parallel system.

[0008] The Helmholtz resonator includes a neck and a closed cavity, and the connection between the neck of its upstream part and the outer pipe or circular pipe is beveled.

[0009] Both ends of the circular pipe are in the shape of inverted rounded corners.

[0010] Both ends of the perforated plate cavity structure are in the shape of inverted rounded corners, and the middle section is in the shape of a hollow cuboid; two opposite outer wall surfaces of the middle section of the perforated plate cavity structure are respectively connected to the outer pipe and the circular pipe; among the other two outer wall surfaces, one outer wall surface is provided with a plurality of round holes, and the plurality of round holes are distributed in a triangular or rectangular array; the perforated outer wall surfaces of the plurality of perforated plate cavity structures are all arranged on the same side.

[0011] The pipe diameter of the connection part between the outer pipe and the perforated plate cavity structure is larger than the pipe diameters at both ends thereof, the length of its large-diameter section is equal to the length of the middle section of the perforated plate cavity structure, and it is uniformly transitionally connected to the small-diameter section; the length of the circular pipe is equal to the length of the perforated plate cavity structure.

[0012] Another technical solution adopted by the present invention is a design method for a pipeline high-frequency resistance muffler based on a Helmholtz resonator, including a design method for a perforated plate cavity structure and a design method for a parallel system of Helmholtz resonators.

[0013] The characteristics of another technical solution of the present invention also lie in:

[0014] The design method for the perforated plate cavity structure is specifically as follows:

[0015] The sound absorption coefficient is the ratio of the sound energy absorbed by the perforated plate cavity structure to the incident sound energy, and the calculation formula for the sound absorption coefficient is:

[0016]

[0017]

[0018]

[0019] In the formula, is the perforated plate cavity structure constant, ω = 2πf is the angular frequency, d, t, σ, r, ωm are respectively the perforation aperture, thickness, perforation rate, sound resistance ratio, and sound reactance ratio of the perforated plate cavity structure; h is the wall surface spacing of the perforated plate cavity structure, η is the viscosity coefficient of the sound medium, and c is the sound velocity;

[0020] After calculating the sound absorption coefficient of the perforated plate cavity structure, then optimize the perforation aperture d, the perforation rate σ, and the wall surface spacing h based on the genetic algorithm to maximize the sound absorption coefficient; define the average transmission loss within the calculated frequency range as the fitness function obj1(x), which is expressed as follows:

[0021]

[0022] 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;

[0023] The variable constraint conditions are determined according to the pipe diameter of the work site supervisor, the high-frequency noise reduction frequency band, and the processing and manufacturing capabilities.

[0024] The design method of the parallel system of Helmholtz resonators is specifically as follows:

[0025] The resonance frequency f of a single Helmholtz resonator r The calculation formula is:

[0026]

[0027] l' c = l c + δ1 + δ2 (6)

[0028] Where: c is the speed of sound, S c is the cross-sectional area of the neck; V = S v l v is the volume of the cavity, S v is the cross-sectional area of the cavity, l v is the height of the cavity; l' c is the acoustic length of the neck, l c is the length of the neck, δ1 and δ2 are the end correction lengths at the connections between the neck and the main pipe and the resonance cavity, δ1 is taken as the wall thickness of the main pipe, and δ2 = 1.7r c , r c is the equivalent radius of the neck;

[0029] Calculate the transmission loss of the parallel system of Helmholtz resonators:

[0030] Use the transfer matrix method to divide the complex system into several acoustic units. The relationship between the inlet and outlet of each acoustic unit is represented by a transfer matrix. Multiply all the transfer matrices to obtain the transfer matrix of the entire system, thereby calculating the system loss. Specifically:

[0031]

[0032]

[0033] Where p i , u i and p o , u o are the sound pressure and particle velocity between the inlet and outlet of the muffler device respectively; [T] = [T1][T2][T3]…[T o is the transfer matrix of the entire parallel system of Helmholtz resonators;

[0034] The transmission loss of the parallel system of Helmholtz resonators is as follows:

[0035]

[0036] In the formula, S i , ρ i , c i , M i and S o , ρ o , c o , M o are respectively the cross-sectional areas, medium density, sound speed and flow Mach number of the inlet and outlet of the muffler device;

[0037] The acoustic units in the parallel system of Helmholtz resonators include Helmholtz resonators and equal-section pipes between adjacent Helmholtz resonators;

[0038] For the equal-section pipe, its transfer matrix is:

[0039]

[0040] In the formula, is the imaginary unit; M is the uniform flow Mach number in the main pipe; k c = k / (1 - M 2 ), k = ω / c is the wave number, ω = 2πf is the circular frequency, f represents the frequency; l is the length of the equal-section;

[0041] The transfer matrix of the Helmholtz resonator is:

[0042]

[0043] In the formula, S is the cross-sectional area of the main pipe;

[0044] Optimizing the parameters of the parallel system of Helmholtz resonators based on the genetic algorithm:

[0045] After establishing the theoretical model of the transmission loss of the Helmholtz resonator system using the above process, then optimize the variables based on the genetic algorithm to maximize the transmission loss, and define the average transmission loss within the calculated frequency range as the fitness function obj2(y):

[0046]

[0047] In the formula, y 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;

[0048] According to the number of Helmholtz resonator arrangements, there are multiple optimization variables, which are respectively the cross-sectional areas S c , S v; The height l of the neck and the closed cavity c 、l v ; The radii R1 and R2 of the outer pipe and the circular pipe; and the distance l between the Helmholtz resonators; the constraint conditions of each variable are determined according to the pipe diameter of the work site supervisor, the high-frequency noise reduction frequency band, the installation space of the muffler, and the processing and manufacturing capabilities.

[0049] The beneficial effects of the present invention are:

[0050] 1. The high-frequency resistance muffler of the pipe based on the Helmholtz resonator of the present invention has excellent noise reduction performance in the high-frequency band. The present invention uses a perforated partition to change the structure of the inner cavity of the pipe. The inside of the perforated partition is a cavity, and circular holes are arranged in an array on one side of the outer wall. At the same time, Helmholtz resonators are arranged in parallel to increase the noise reduction frequency range and improve the noise reduction performance.

[0051] 2. The high-frequency resistance muffler of the pipe based on the Helmholtz resonator of the present invention is applicable to complex environments such as high temperature and humidity. The materials of the present invention are selected as hard materials such as structural steel, overcoming the disadvantages that noise reduction materials are prone to failure in environments such as high temperature, humidity, and corrosion.

[0052] 3. The high-frequency resistance muffler of the pipe based on the Helmholtz resonator of the present invention can change parameters to reduce noise in a specified frequency band. The perforation rate, aperture of the perforated partition, and the structural dimensions of the Helmholtz resonator in the present invention have great adjustability and can be reasonably selected according to the specific frequency range that needs to be noise-reduced.

[0053] 4. The high-frequency resistance muffler of the pipe based on the Helmholtz resonator of the present invention has a simple structure and is easy to manufacture, install, and disassemble. Description of the Drawings

[0054] Figure 1 is a schematic structural diagram of the high-frequency resistance muffler of the pipe based on the Helmholtz resonator of the present invention;

[0055] Figure 2 is a cross-sectional view of the high-frequency resistance muffler of the pipe based on the Helmholtz resonator of the present invention;

[0056] Figure 3 is a sectional view of the high-frequency resistance muffler of the pipe based on the Helmholtz resonator of the present invention;

[0057] Figure 4 is a side view of the high-frequency resistance muffler of the pipe based on the Helmholtz resonator of the present invention;

[0058] Figure 5 is a structural diagram of the Helmholtz resonator in the high-frequency resistance muffler of the pipe based on the Helmholtz resonator of the present invention.

[0059] In the figure, 1. Outer pipe; 2. Circular pipe; 3. Perforated plate cavity structure; 4. Flange. Detailed implementation manners

[0060] The present invention will be described in detail below with reference to the accompanying drawings and specific implementation manners.

[0061] The high-frequency resistance muffler for pipelines based on Helmholtz resonators of the present invention, as Figure 1 shown, includes an outer pipeline 1. Inside the outer pipeline 1, a circular pipe 2 is connected through a plurality of perforated plate cavity structures 3, and the outer pipeline 1 and the circular pipe 2 form a concentric nested structure; the plurality of perforated plate cavity structures 3 are parallel to the axis of the circular pipe 2 and are uniformly arranged along the circumferential direction of the circular pipe 2. The plurality of perforated plate cavity structures 3 divide the annular cavity formed between the outer pipeline 1 and the circular pipe 2 into a plurality of sub-cavities with the same size; both ends of the outer pipeline 1 are connected with flanges 4, which is convenient for installation and disassembly.

[0062] Combined with Figures 2 to 4 shown, Helmholtz resonators are arranged on the inner walls of the outer pipeline 1 and the circular pipe 2 along their lengths, that is, annular grooves are opened on the inner walls of the outer pipeline 1 and the circular pipe 2. Each annular groove includes a neck and a closed cavity, forming a Helmholtz resonator. A plurality of annular grooves are opened along the lengths of the outer pipeline 1 and the circular pipe 2, respectively forming a plurality of Helmholtz resonators.

[0063] The Helmholtz resonator is a structure that uses the resonance principle to eliminate noise. It is composed of a neck and a closed cavity connected to the main pipeline. The noise elimination principle is based on the acoustic wave resonance effect. When the frequency of the external acoustic wave is consistent with the natural frequency of the resonator, the resonator will strongly absorb the acoustic energy and convert it into heat energy or other forms of energy, thereby achieving the noise elimination effect. By changing the sizes of the neck and the closed cavity, the suppression of noise with different frequencies can be realized. Connecting multiple Helmholtz resonators with different structural sizes in parallel can cover a wider noise elimination frequency range and improve the noise elimination performance. The number and structural sizes of the Helmholtz resonators are designed according to the noise frequency. The Helmholtz resonators are designed in parallel on the inner wall of the outer pipeline 1 and the inner wall of the circular pipe 2 to form a Helmholtz resonator parallel system, covering a wider noise elimination frequency range and achieving better noise elimination performance. As Figure 5 shown, the right angle at the connection between the upstream part of the neck of the Helmholtz resonator structure and the outer pipeline 1 or the circular pipe 2 is modified to be beveled, so that the air flow gradually changes direction, which can improve the flow characteristics, reduce the energy loss and secondary noise.

[0064] As Figure 2 and Figure 4 shown, the middle section of the perforated plate cavity structure 3 is in the shape of a hollow cuboid, and both ends are in the shape of inverted round corners; two opposite outer wall surfaces of the middle section are respectively connected to the outer pipeline 1 and the circular pipe 2; among the other two outer wall surfaces, a plurality of round holes are opened on one outer wall surface, and the plurality of round holes are distributed in a triangular or rectangular array. The perforated outer wall surfaces of the plurality of perforated plate cavity structures 3 are all arranged on the same side, as Figure 4As shown in the figure, the sub-cavity formed by the two outer wall surfaces of two adjacent perforated plate cavity structures 3, the outer pipe 1, and the round pipe 2 has only one outer wall surface perforated. While ensuring the structural strength, the single-side wall opening enables sound waves to enter the cavity through the round holes to form resonance, ultimately achieving effective suppression of noise in a specific frequency band.

[0065] As Figure 3 shown in the figure, after the two ends of the round pipe 2 are rounded, the sharp parts will cause air flow separation and form vortex noise. The rounding makes the air flow transition smoothly, avoiding secondary noise generated by air flow separation and vortex shedding. At the same time, it reduces the air flow resistance and pressure loss, can effectively suppress impact and vibration, and prolongs the service life of the device. The length of the round pipe 2 is equal to the length of the perforated plate cavity structure 3. In order to ensure that the net flow area of the pipe in the pipe partition section is the same as that of the main pipe, the diameter of the connecting part of the outer pipe 1 and the perforated plate cavity structure 3 is larger than the diameters of its two ends, and the length of its large-diameter section is equal to the length of the middle section of the perforated plate cavity structure 3, and it is uniformly transitionally connected to the small-diameter section.

[0066] The perforated plate cavity structure 3 of the present invention and the connection between the perforated plate cavity structure 3, the outer pipe 1, and the round pipe 2 use welding connection or are integrally formed by 3D printing technology. The materials of the perforated plate cavity structure 3, the outer pipe 1, and the round pipe 2 are selected as hard materials such as structural steel, and are applicable to various environments.

[0067] The design method of the pipeline high-frequency resistance muffler based on the Helmholtz resonator of the present invention includes the design method of the perforated plate cavity structure and the design method of the Helmholtz resonator parallel system.

[0068] The design method of the perforated plate cavity structure is specifically as follows:

[0069] The sound absorption coefficient is the ratio of the sound energy absorbed by the perforated plate cavity structure to the incident sound energy. The calculation formula of the sound absorption coefficient is:

[0070]

[0071]

[0072]

[0073] In the formula, is the perforated plate cavity structure constant, ω = 2πf is the angular frequency, d, t, σ, r, ωm are respectively the perforation aperture, thickness, perforation rate, sound resistance ratio, and sound reactance ratio of the perforated plate cavity structure; h is the wall surface spacing of the perforated plate cavity structure, η is the viscosity coefficient of the sound medium, and c is the sound speed;

[0074] After calculating the sound absorption coefficient of the perforated plate cavity structure, the perforation diameter d, the perforation rate σ, and the wall spacing h are optimized based on the genetic algorithm to maximize the sound absorption coefficient. The average transmission loss within the calculated frequency range is defined as the fitness function obj1(x) and is expressed as follows:

[0075]

[0076] where x is the row vector of the independent variables of the objective function; f1 and f2 are the lower and upper limits of the calculated frequency; Δf is the calculated frequency step size;

[0077] The constraint conditions for each variable are determined according to the pipe diameter of the work site supervisor, the high-frequency noise reduction frequency band, and the processing and manufacturing capabilities.

[0078] The design method of the parallel system of Helmholtz resonators is specifically as follows:

[0079] The resonance frequency f of a single Helmholtz resonator r The calculation formula is:

[0080]

[0081] l' c = l c + δ1 + δ2 (6)

[0082] where: c is the speed of sound, S c is the cross-sectional area of the neck; V = S v l v is the volume of the cavity, S v is the cross-sectional area of the cavity, l v is the height of the cavity; l' c is the acoustic length of the neck, l c is the length of the neck, δ1 and δ2 are the end correction lengths at the connections between the neck and the main pipe and the resonance cavity, take δ1 as the wall thickness of the main pipe, δ2 = 1.7r c r c is the equivalent radius of the neck;

[0083] Calculate the transmission loss of the parallel system of Helmholtz resonators;

[0084] Using the transfer matrix method, the complex system is divided into several acoustic units. The relationship between the inlet and outlet of each acoustic unit is represented by a transfer matrix. Multiply all the transfer matrices to obtain the transfer matrix of the entire system, and thus calculate the system loss. Specifically:

[0085]

[0086]

[0087] where, p i, u i and p o , u o are respectively the sound pressure and the particle vibration velocity between the inlet and the outlet of the noise elimination device; [T] = [T1][T2][T3]…[T o is the transfer matrix of the entire parallel system of Helmholtz resonators;

[0088] The transmission loss of the parallel system of Helmholtz resonators is:

[0089]

[0090] In the formula, S i , ρ i , c i , M i and S o , ρ o , c o , M o are respectively the cross-sectional areas, the medium density, the sound velocity and the airflow Mach number at the inlet and the outlet of the noise elimination device;

[0091] The acoustic units in the parallel system of Helmholtz resonators include Helmholtz resonators and the equal-section pipes between adjacent Helmholtz resonators;

[0092] For the equal-section pipe, its transfer matrix is:

[0093]

[0094] In the formula, is the imaginary unit; M is the uniform flow Mach number in the main pipe; k c = k / (1 - M 2 ), k = ω / c is the wave number, ω = 2πf is the circular frequency, f represents the frequency; l is the length of the equal-section;

[0095] The transfer matrix of the Helmholtz resonator is:

[0096]

[0097] In the formula, S is the cross-sectional area of the main pipe;

[0098] Optimizing the parameters of the parallel system of Helmholtz resonators based on the genetic algorithm:

[0099] After establishing the theoretical model of the transmission loss of the Helmholtz resonator system by using the above process, then optimize the variables based on the genetic algorithm to maximize the transmission loss, and define the average transmission loss in the calculation frequency range as the fitness function obj2(y):

[0100]

[0101] where y 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 step size of the calculated frequency;

[0102] According to the number of Helmholtz resonator arrangements, there are multiple optimization variables, which are respectively the cross-sectional areas S c 、S v of the neck and the closed cavity of the Helmholtz resonator; the heights l c 、l v of the neck and the closed cavity; the radii R1 and R2 of the outer pipe and the circular pipe; and the distance l between the Helmholtz resonators; the constraint conditions of each variable are determined according to the diameter of the main pipe at the work site, the high-frequency noise reduction frequency band, the installation space of the muffler, and the processing and manufacturing capabilities.

[0103] Example 1

[0104] This example provides a high-frequency resistance muffler for pipes based on Helmholtz resonators. As Figure 1 shown, it specifically includes an outer pipe 1. Inside the outer pipe 1, a circular pipe 2 is connected through a plurality of perforated plate cavity structures 3, and the outer pipe 1 and the circular pipe 2 form a concentric nested structure; the plurality of perforated plate cavity structures 3 are parallel to the axis of the circular pipe 2 and are uniformly arranged along the circumferential direction of the circular pipe 2. The plurality of perforated plate cavity structures 3 divide the annular cavity formed between the outer pipe 1 and the circular pipe 2 into a plurality of sub-cavities of the same size; flanges 4 are connected to both ends of the outer pipe 1.

[0105] Example 2

[0106] On the basis of Example 1, a number of Helmholtz resonators are arranged along the length directions of the inner wall of the outer pipe 1 and the inner wall of the circular pipe 2; the Helmholtz resonators are designed in parallel on the inner wall of the outer pipe 1 and the inner wall of the circular pipe 2 to form a Helmholtz resonator parallel system. The Helmholtz resonator includes a neck and a closed cavity, and the connection part of the neck in its upstream part with the outer pipe 1 or the circular pipe 2 is beveled. Both ends of the circular pipe 2 are in the shape of inverted rounded corners.

[0107] Example 3

[0108] On the basis of Example 2, both ends of the perforated plate cavity structure 3 are in the shape of inverted rounded corners, and the middle section is in the shape of a hollow cuboid; two opposite outer wall surfaces in the middle section of the perforated plate cavity structure 3 are respectively connected to the outer pipe 1 and the circular pipe 2; among the other two outer wall surfaces, one outer wall surface is provided with a number of round holes, and the number of round holes is distributed in a triangular or rectangular array; the perforated outer wall surfaces of the plurality of perforated plate cavity structures 3 are all arranged on the same side.

[0109] The diameter of the connection part between the outer pipe 1 and the perforated plate cavity structure 3 is larger than the diameters of its two ends, the length of its large-diameter section is equal to the length of the middle section of the perforated plate cavity structure 3, and it is uniformly transitionally connected to the small-diameter section; the length of the circular pipe 2 is equal to the length of the perforated plate cavity structure 3.

[0110] Example 4

[0111] This embodiment provides a design method for a high-frequency resistance muffler for pipelines based on Helmholtz resonators, a design method for a perforated plate cavity structure, and a design method for a parallel system of Helmholtz resonators.

[0112] Example 5

[0113] Based on Example 4, the design method for the perforated plate cavity structure is specifically as follows:

[0114] The sound absorption coefficient is the ratio of the sound energy absorbed by the perforated plate cavity structure to the incident sound energy. The calculation formula for the sound absorption coefficient is:

[0115]

[0116]

[0117]

[0118] In the formula, is the perforated plate cavity structure constant, ω = 2πf is the angular frequency, d, t, σ, r, ωm are respectively the perforation aperture, thickness, perforation rate, sound resistance ratio, and sound reactance ratio of the perforated plate cavity structure; h is the wall spacing of the perforated plate cavity structure, η is the viscosity coefficient of the sound medium, and c is the speed of sound;

[0119] After calculating the sound absorption coefficient of the perforated plate cavity structure, the perforation aperture d, the perforation rate σ, and the wall spacing h are optimized based on the genetic algorithm to maximize the sound absorption coefficient; the average transmission loss within the calculated frequency range is defined as the fitness function obj1(x), which is expressed as follows:

[0120]

[0121] 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;

[0122] The constraint conditions for each variable are determined according to the main pipe diameter at the work site, the high-frequency noise reduction frequency band, and the processing and manufacturing capabilities.

[0123] Example 6

[0124] Based on Example 4, the design method for the parallel system of Helmholtz resonators is specifically as follows:

[0125] The resonance frequency f of a single Helmholtz resonator r The calculation formula is:

[0126]

[0127] l' c = lc +δ1 + δ2 (6)

[0128] Where: c is the speed of sound, S c is the cross-sectional area of the neck; V = S v l v is the volume of the cavity, S v is the cross-sectional area of the cavity, l v is the height of the cavity; l' c is the acoustic length of the neck, l c is the length of the neck, δ1 and δ2 are the end correction lengths at the connections between the neck and the main duct and the resonance cavity. Take δ1 as the wall thickness of the main duct, δ2 = 1.7r c , r c is the equivalent radius of the neck;

[0129] Calculate the transmission loss of the parallel system of Helmholtz resonators:

[0130] Use the transfer matrix method to divide the complex system into several acoustic units. The relationship between the inlet and outlet of each acoustic unit is represented by a transfer matrix. Multiply all the transfer matrices to obtain the transfer matrix of the whole system, and then calculate the system loss. Specifically:

[0131]

[0132]

[0133] Where, p i , u i and p o , u o are the sound pressure and particle velocity between the inlet and outlet of the muffler respectively; [T] = [T1][T2][T3]…[T o is the transfer matrix of the whole parallel system of Helmholtz resonators;

[0134] The transmission loss of the parallel system of Helmholtz resonators is:

[0135]

[0136] Where, S i , ρ i , c i , M i and S o , ρ o , c o , M o are the cross-sectional areas, medium density, speed of sound and flow Mach number at the inlet and outlet of the muffler respectively;

[0137] The acoustic unit in the parallel system of Helmholtz resonators includes Helmholtz resonators and equal - cross - section pipes between adjacent Helmholtz resonators;

[0138] For the equal - cross - section pipe, its transfer matrix is:

[0139]

[0140] In the formula, is the imaginary unit; M is the Mach number of the uniform flow in the main pipe; k c = k / (1 - M 2 ), k = ω / c is the wave number, ω = 2πf is the circular frequency, f represents the frequency; l is the length of the equal - cross - section;

[0141] The transfer matrix of the Helmholtz resonator is:

[0142]

[0143] In the formula, S is the cross - sectional area of the main pipe;

[0144] Optimizing the parameters of the parallel system of Helmholtz resonators based on the genetic algorithm:

[0145] After establishing the theoretical model of the transmission loss of the Helmholtz resonator system using the above process, then optimize the variables based on the genetic algorithm to maximize the transmission loss, and define the average transmission loss in the calculation frequency range as the fitness function obj2(y):

[0146]

[0147] In the formula, y 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;

[0148] According to the number of Helmholtz resonators arranged, there are multiple optimization variables, which are the cross - sectional areas S c 、S v of the neck and the closed cavity of the Helmholtz resonator; the heights l c 、l v of the neck and the closed cavity; the outer pipe and circular pipe radii R1, R2; and the distance l between Helmholtz resonators; the constraint conditions of each variable are determined according to the main pipe diameter at the work site, the high - frequency noise reduction frequency band, the installation space of the muffler, and the processing and manufacturing capacity.

Claims

1. A high frequency reactive muffler for pipes based on a Helmholtz resonator, characterized in that: The invention comprises an outer pipe (1), wherein the outer pipe (1) is connected to a circular pipe (2) via a plurality of perforated plate cavity structures (3), wherein the outer pipe (1) and the circular pipe (2) form a concentric nested structure; the plurality of perforated plate cavity structures (3) are parallel to the axis of the circular pipe (2) and are evenly arranged along the circumference of the circular pipe (2); the plurality of perforated plate cavity structures (3) divide the annular cavity formed between the outer pipe (1) and the circular pipe (2) into a plurality of sub-cavities of the same size; and flanges (4) are connected at both ends of the outer pipe (1).

2. The pipeline high frequency resistance muffler based on the Helmholtz resonator according to claim 1 is characterized in that: The inner wall of the outer pipe (1) and the inner wall of the circular pipe (2) are both provided with a plurality of Helmholtz resonators along their length directions; the Helmholtz resonators are connected in parallel on the inner wall of the outer pipe (1) and the inner wall of the circular pipe (2) to form a Helmholtz resonator parallel system.

3. The pipeline high frequency resistance muffler based on Helmholtz resonator according to claim 2 is characterized in that: The Helmholtz resonator comprises a neck and a closed cavity, and the connection between the neck of the upstream part and the outer pipe (1) or the round pipe (2) is in a beveled shape.

4. The pipeline high frequency resistance muffler based on the Helmholtz resonator according to claim 3 is characterized in that: Both ends of the circular tube (2) are in a rounded shape.

5. The pipeline high frequency resistance muffler based on Helmholtz resonator according to claim 4, characterized in that: The two ends of the perforated plate cavity structure (3) are in a chamfered shape, and the middle section is in a hollow rectangular shape; the two opposite outer wall surfaces of the middle section of the perforated plate cavity structure (3) are respectively connected to the outer pipe (1) and the circular pipe (2); one of the other two outer wall surfaces is provided with a plurality of circular holes, and the plurality of circular holes are distributed in a triangular or rectangular array; the perforated outer wall surfaces of the plurality of perforated plate cavity structures (3) are all arranged on the same side.

6. The pipeline high frequency resistance muffler based on Helmholtz resonator according to claim 5, characterized in that: The diameter of the connecting portion of the outer pipe (1) and the perforated plate cavity structure (3) is larger than the diameters of the two ends thereof, the length of the large diameter section is equal to the length of the middle section of the perforated plate cavity structure (3), and is evenly transitionally connected to the small diameter section; the length of the circular pipe (2) is equal to the length of the perforated plate cavity structure (3).

7. The design method of the pipeline high-frequency reactive muffler based on the Helmholtz resonator according to claim 6 is characterized in that: It includes the design method of perforated plate cavity structure and the design method of Helmholtz resonator parallel system.

8. The pipeline high frequency resistance muffler based on Helmholtz resonator according to claim 7, characterized in that: The design method of the perforated plate cavity structure is as follows: The sound absorption coefficient is the ratio of the sound energy absorbed by the perforated plate cavity structure to the incident sound energy. The sound absorption coefficient calculation formula is: In the formula, is the perforated plate cavity structure constant, ω=2πf is the angular frequency, d, t, σ, r, ωm are the perforation aperture, thickness, perforation rate, acoustic resistance ratio, and acoustic reactance ratio of the perforated plate cavity structure respectively; h is the wall spacing of the perforated plate cavity structure, η is the viscosity coefficient of the acoustic medium, and c is the sound velocity; After calculating the sound absorption coefficient of the perforated plate cavity structure, the perforation aperture d, perforation rate σ and wall spacing h are optimized based on the genetic algorithm to maximize the sound absorption coefficient; the average transmission loss within the calculation frequency range is defined as the fitness function obj1(x), which is expressed as follows: 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 constraints of each variable are determined based on the main pipe diameter at the work site, the high-frequency silencing band, and the processing and manufacturing capabilities.

9. The pipeline high frequency resistance muffler based on Helmholtz resonator according to claim 7, characterized in that: The design method of the Helmholtz resonator parallel system is as follows: The resonance frequency of a single Helmholtz resonator is f r The calculation formula is: l c '=l c +δ1+δ2 (6) Where: c is the speed of sound, S c is the cross-sectional area of ​​the neck; V = S v l v is the volume of the cavity, S v is the cross-sectional area of ​​the cavity, l v is the height of the cavity; l c ' is the acoustic length of the neck, l c is the neck length, δ1 and δ2 are the end correction lengths of the neck and the main pipe and the resonance cavity. δ1 is the main pipe wall thickness, δ2 = 1.7r c , r c is the equivalent radius of the neck; Calculate the transmission loss of a parallel system of Helmholtz resonators: The transfer matrix method is used to divide a complex system into several acoustic units. The relationship between the import and export of each acoustic unit is expressed by the transfer matrix. All transfer matrices are multiplied to obtain the transfer matrix of the entire system, so as to calculate the system loss, which is: In the formula, p i 、u i and p o 、u o are the sound pressure and particle vibration velocity between the inlet and outlet of the silencer, respectively; [T] = [T1] [T2] [T3]… [T o ] is the transfer matrix of the entire Helmholtz resonator parallel system; The transmission loss of the parallel system of Helmholtz resonators is: In the formula, S i , i 、c i 、M i and S o , o 、c o 、M o are the cross-sectional areas of the inlet and outlet of the muffler, medium density, sound speed and airflow Mach number; The acoustic unit in the parallel Helmholtz resonator system includes a Helmholtz resonator and a pipe of equal cross-section between adjacent Helmholtz resonators; For a pipe with a uniform cross section, the transfer matrix is: In the formula, is an imaginary unit; M is the uniform flow Mach number in the main pipe; k c = k / (1-M 2 ), k = ω / c is the wave number, ω = 2πf is the circular frequency, f represents the frequency; l is the length of the equal section; The Helmholtz resonator transfer matrix is: Where S is the cross-sectional area of ​​the main pipeline; Parameter optimization of Helmholtz resonator parallel system based on genetic algorithm: After establishing the theoretical model of the transmission loss of the Helmholtz resonator system using the above process, the variables are optimized based on the genetic algorithm to maximize the transmission loss, and the average transmission loss within the calculation frequency range is defined as the fitness function obj2(y): Where y 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; According to the number of Helmholtz resonators, there are several optimization variables, namely, the cross-sectional area S of the Helmholtz resonator neck and the closed cavity. c , S v ; Height of neck and closed cavity l c , l v ; The radii of the outer pipe and the circular pipe R1, R2; and the distance l between the Helmholtz resonators; the constraints of each variable are determined according to the main pipe diameter at the work site, the high-frequency silencer frequency band, the silencer installation space, and the processing and manufacturing capabilities.

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