Pipe high-frequency resistance muffler based on helmholtz resonator and design method thereof

Abstract

The application discloses a pipeline high-frequency resistance muffler based on a Helmholtz resonator, which comprises an outer pipeline, a circular pipe connected to the inner part of the outer pipeline through a plurality of perforated plate cavity structures, and a concentric nested structure formed by the outer pipeline and the circular pipe; the plurality of perforated plate cavity structures are parallel to the axis of the circular pipe and are uniformly arranged along the circumference 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 with the same size; flanges are connected to both ends of the outer pipeline. The application further discloses a design method of the pipeline high-frequency resistance muffler based on the Helmholtz resonator. The pipeline high-frequency resistance muffler based on the Helmholtz resonator can effectively reduce the high-frequency noise of the pipeline.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of pipeline high-frequency noise suppression devices, and particularly relates to a pipeline high-frequency resistance muffler based on a Helmholtz resonator and a design method thereof. BACKGROUND

[0002] Pipeline systems are widely used in the industrial fields of automobile manufacturing, chemical production, building heating and ventilation, etc. as the core carriers for fluid transmission. However, the noise pollution problem caused thereby is increasingly prominent. High-frequency noise (above 2000 Hz) is easy to cause complex sound-vibration coupling effects with the pipeline system due to the characteristics of wide frequency domain distribution and low attenuation rate. When the structural resonance frequency caused by fluid excitation coincides with the main frequency of noise, material fatigue damage can be accelerated under light working conditions, and the service cycle of the pipeline is shortened. In extreme cases, mechanical vibration caused by resonance can significantly reduce the measurement accuracy of instruments, and even induce chain failures of key equipment such as pump valve systems and pressure vessels. Long-term exposure of workers in industrial sites to the high-frequency noise environment of the pipeline system can cause noise-induced hearing loss and pathological changes in non-auditory systems. The current high-frequency noise control mainly relies on porous resistive sound-absorbing materials (such as melamine foam or glass fiber cotton), and the noise reduction mechanism thereof depends on the viscous-heat dissipation effect, which has poor environmental tolerance, material degradation risk and secondary pollution hazards. In view of the above problems, a resistance muffler can be integrated at the key nodes of the pipeline system, which has the characteristics of controllable acoustic performance, strong environmental adaptability and full life cycle safety. SUMMARY

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

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

[0005] The technical solution adopted by the present application is that the pipeline high-frequency resistance muffler based on a Helmholtz resonator comprises an outer pipeline, a circular pipe 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 uniformly arranged along the circumference 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 present application is also characterized in that:

[0007] A plurality of Helmholtz resonators are arranged on the inner wall of the outer pipeline and the inner wall of the circular pipe along the length direction thereof; and 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 consists of a neck and a closed cavity, with the upstream part of the neck connecting to the outer tube or round tube in an oblique shape.

[0009] The two ends of the round tube are rounded.

[0010] The perforated plate cavity structure has rounded corners at both ends and a hollow cuboid shape in the middle section. The two opposite outer walls of the middle section of the perforated plate cavity structure are connected to the outer pipe and the round pipe, respectively. One of the other two outer walls has several round holes, which are distributed in a triangular or rectangular array. The perforated outer walls of several perforated plate cavity structures are all located on the same side.

[0011] The diameter of the pipe connecting the outer pipe to the perforated plate cavity structure is larger than the diameters at both ends. The length of the larger diameter section is equal to the length of the middle section of the perforated plate cavity structure, and it is uniformly transitioned to the smaller diameter section. The length of the circular pipe is equal to the length of the perforated plate cavity structure.

[0012] Another technical solution adopted in this invention is a design method for a high-frequency reactive silencer for pipelines based on Helmholtz resonators, including a design method for a perforated plate cavity structure and a design method for a parallel system of Helmholtz resonators.

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

[0014] The design method for the perforated plate cavity structure is 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. The formula for calculating the sound absorption coefficient is:

[0016]

[0017]

[0018]

[0019] In the formula, Let ω = 2πf be the structural constant of the perforated plate cavity, d, t, σ, r, and ωm be the perforation diameter, thickness, perforation rate, acoustic impedance ratio, and acoustic impedance ratio of the perforated plate cavity structure, respectively; h be the wall spacing of the perforated plate cavity structure; η be the viscosity coefficient of the acoustic medium; and c be the sound velocity.

[0020] After calculating the sound absorption coefficient of the perforated plate cavity structure, the perforation diameter d, perforation rate σ, and wall spacing h are optimized using a 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), as follows:

[0021]

[0022] In the formula, x is the row vector of the independent variable of the objective function; f1 and f2 are the lower limit and upper limit of the calculation frequency; and Δf is the calculation frequency step;

[0023] The variable constraint condition is determined according to the working site supervisor pipe diameter, high-frequency sound absorption frequency band and processing manufacturing capacity.

[0024] The design method of the Helmholtz resonator parallel system specifically comprises the following steps:

[0025] The resonant frequency f of the single Helmholtz resonator r The calculation formula is as follows:

[0026]

[0027] l' c =l c +δ1+δ2 (6)

[0028] In the formula, c is the sound speed, 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 of the neck and the main pipe and the resonant cavity, δ1 is the wall thickness of the main pipe, δ2=1.7r c , r c is the equivalent radius of the neck;

[0029] The transmission loss of the Helmholtz resonator parallel system is calculated as follows:

[0030] The complex system is divided into several acoustic units by using the transfer matrix method, the relationship between the inlet and outlet of each acoustic unit is represented by a transfer matrix, and the transfer matrix of the entire system is obtained by multiplying all the transfer matrices, so that the system loss is calculated, and the specific process is as follows:

[0031]

[0032]

[0033] In the formula, 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; [T]=[T1][T2][T3]…[T o ] is the transfer matrix of the entire Helmholtz resonator parallel system;

[0034] The transmission loss of the Helmholtz resonator parallel system is:

[0035]

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

[0037] The acoustic unit in the Helmholtz resonator parallel system includes a Helmholtz resonator and an equal cross-section pipeline between adjacent Helmholtz resonators;

[0038] For the equal cross-section pipeline, the transfer matrix is:

[0039]

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

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

[0042]

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

[0044] Based on the genetic algorithm, the parameters of the Helmholtz resonator parallel system are optimized:

[0045] After the theoretical model of the transmission loss of the Helmholtz resonator system is established by using the above process, the genetic algorithm is used to optimize the variables to maximize the transmission loss, and the average transmission loss in the calculation frequency range is defined 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 limit and upper limit of the calculation frequency; and Δf is the calculation frequency step;

[0048] According to the number of Helmholtz resonators, there are multiple optimization variables, which are the cross-sectional areas S c , S v; neck and the height of the closed cavity l c 、 v ; outer pipe and pipe radius R1, R2; and the distance between Helmholtz resonator l; each variable constraint condition is determined according to the working site main pipe diameter, high frequency sound absorption frequency band, muffler installation space, processing and manufacturing capacity.

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

[0050] 1, the present application based on the Helmholtz resonator pipe high frequency resistance muffler in high frequency band excellent sound absorption performance. The present application uses the perforated partition to change the pipe cavity structure, the perforated partition is empty cavity, the outer wall single side sets up the round hole and distributes according to array, simultaneously introduces Helmholtz resonator to arrange in parallel form, increases the sound absorption frequency range, and improves the sound absorption performance.

[0051] 2, the present application based on the Helmholtz resonator pipe high frequency resistance muffler is applicable to high temperature, humidity and other complex environment. The present application material selects structural steel and other hard materials, which overcomes the shortcomings that the sound absorption material is easy to fail in high temperature, humidity, corrosion and other environments.

[0052] 3, the present application based on the Helmholtz resonator pipe high frequency resistance muffler can change the parameter to the designated frequency band sound absorption. The perforation rate, aperture of the perforated partition and the structure size of the Helmholtz resonator in the present application have great adjustability, and reasonable selection is carried out according to the frequency range of the specific need sound absorption.

[0053] 4, the present application based on the Helmholtz resonator pipe high frequency resistance muffler, simple structure, easy to manufacture, install and disassemble. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 is the structure diagram of the present application based on the Helmholtz resonator pipe high frequency resistance muffler;

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

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

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

[0058] Figure 5 is the structure diagram of the Helmholtz resonator in the present application based on the Helmholtz resonator pipe high frequency resistance muffler.

[0059] In the drawing, 1 is an outer pipe, 2 is a circular pipe, 3 is a perforated plate cavity structure, and 4 is a flange. Detailed Implementation

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

[0061] This invention relates to a high-frequency reactive silencer for pipelines based on a Helmholtz resonator, such as... Figure 1 As shown, it includes an outer pipe 1, and a circular pipe 2 is connected inside the outer pipe 1 through several perforated plate cavity structures 3. The outer pipe 1 and the circular pipe 2 form a concentric nested structure. The several 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 several perforated plate cavity structures 3 divide the annular cavity formed between the outer pipe 1 and the circular pipe 2 into several sub-cavities of the same size. Flanges 4 are connected to both ends of the outer pipe 1 for easy installation and disassembly.

[0062] Combination Figures 2 to 4 As shown, several Helmholtz resonators are arranged along the length of both the inner wall of the outer pipe 1 and the inner wall of the circular pipe 2. That is, annular grooves are formed on the inner walls of the outer pipe 1 and the circular pipe 2, and each annular groove includes a neck and a closed cavity, forming a Helmholtz resonator. Several annular grooves are formed along the length of the outer pipe 1 and the circular pipe 2, respectively forming several Helmholtz resonators.

[0063] A Helmholtz resonator is a structure that uses the principle of resonance to reduce noise. It consists of a neck connected to the main duct and a closed cavity. The noise reduction principle is based on the sound wave resonance effect. When the frequency of the external sound wave matches the resonator's natural frequency, the resonator strongly absorbs the sound energy and converts it into heat energy or other forms of energy, thereby achieving a noise reduction effect. Different frequencies of noise can be suppressed by changing the dimensions of the neck and the closed cavity. Connecting multiple Helmholtz resonators with different structural dimensions in parallel covers a wider range of noise reduction frequencies and improves noise reduction performance. The number and structural dimensions of the Helmholtz resonators are designed according to the noise frequency. A parallel design of Helmholtz resonators on the inner wall of outer duct 1 and inner wall of circular duct 2 forms a parallel Helmholtz resonator system, covering a wider range of noise reduction frequencies and achieving better noise reduction performance. Figure 5 As shown, the right angle at the connection between the neck of the upstream part of the Helmholtz resonator structure and the outer pipe 1 or the circular pipe 2 is modified into an oblique shape, so that the airflow gradually changes direction, which can improve the flow characteristics and reduce energy loss and secondary noise.

[0064] like Figure 2 and Figure 4 As shown, the middle section of the perforated plate cavity structure 3 is a hollow cuboid shape with rounded corners at both ends; the two opposite outer walls of the middle section are connected to the outer pipe 1 and the circular pipe 2, respectively; one of the other two outer walls has several circular holes, which are arranged in a triangular or rectangular array. All the perforated outer walls of the perforated plate cavity structures 3 are located on the same side, such as... Figure 4As shown, the sub-cavity formed by the two outer walls of two adjacent perforated plate cavity structures 3, the outer pipe 1, and the circular pipe 2 has only one perforated outer wall. The single-sided wall opening ensures structural strength while allowing sound waves to enter the cavity through the circular hole to form resonance, ultimately achieving effective suppression of noise in a specific frequency range.

[0065] like Figure 3 As shown, after the ends of the circular tube 2 are rounded, the sharp parts will cause airflow separation and form vortex noise. The rounded corners make the airflow transition smoothly, avoiding secondary noise caused by airflow separation and vortex shedding. At the same time, it reduces airflow resistance and pressure loss, effectively suppressing impact and vibration, and extending the service life of the device. The length of the circular tube 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 outer pipe 1 at the connection with the perforated plate cavity structure 3 is larger than the diameter 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 transitioned to the small diameter section.

[0066] The perforated plate cavity structure 3 of the present invention and the perforated plate cavity structure 3, the outer pipe 1, and the round pipe 2 are integrally formed by welding or 3D printing technology. The materials of the perforated plate cavity structure 3 and the outer pipe 1 and the round pipe 2 are selected from rigid materials such as structural steel, which are suitable for various environments.

[0067] This invention relates to a design method for a high-frequency reactive silencer for pipelines based on Helmholtz resonators, including a design method for a perforated plate cavity structure and a design method for a parallel system of Helmholtz resonators.

[0068] The design method for the perforated plate cavity structure is 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 formula for calculating the sound absorption coefficient is:

[0070]

[0071]

[0072]

[0073] In the formula, Let ω = 2πf be the structural constant of the perforated plate cavity, d, t, σ, r, and ωm be the perforation diameter, thickness, perforation rate, acoustic impedance ratio, and acoustic impedance ratio of the perforated plate cavity structure, respectively; h be the wall spacing of the perforated plate cavity structure; η be the viscosity coefficient of the acoustic medium; and c be the sound velocity.

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

[0075]

[0076] In the formula, x is the row vector of the independent variable of the objective function; f1 and f2 are the lower limit and upper limit of the calculation frequency; and Δf is the calculation frequency step;

[0077] The variable constraint conditions are determined according to the working site main pipe diameter, high-frequency muffling frequency band and processing and manufacturing capacity.

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

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

[0080]

[0081] l' c = l c + δ1 + δ2 (6)

[0082] In the formula, c is the sound velocity, S c is the neck cross-sectional area; 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 resonant cavity, δ1 is the wall thickness of the main pipe, and δ2 = 1.7r c , r c is the equivalent radius of the neck;

[0083] The transmission loss of the Helmholtz resonator parallel system is calculated;

[0084] The complex system is divided into a plurality of acoustic units by using the transfer matrix method, the relationship between the inlet and outlet of each acoustic unit is expressed by a transfer matrix, the transfer matrices of all acoustic units are multiplied to obtain the transfer matrix of the whole system, and then the system loss is calculated, and the specific process is as follows:

[0085]

[0086]

[0087] In the formula, 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 Helmholtz resonator and parallel system;

[0088] The transfer loss of the Helmholtz resonator and parallel system is:

[0089]

[0090] In the formula, S i , ρ i , c i , M i and S o , ρ o , c o , M o are the cross-sectional area, medium density, sound speed and Mach number of airflow at the inlet and outlet of the muffler, respectively;

[0091] The acoustic unit in the Helmholtz resonator and parallel system includes a Helmholtz resonator and an equal cross-section pipeline between adjacent Helmholtz resonators;

[0092] For the equal cross-section pipeline, the transfer matrix is:

[0093]

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

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

[0096]

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

[0098] Based on the genetic algorithm, the parameters of the Helmholtz resonator and parallel system are optimized:

[0099] After the theoretical model of the transfer loss of the Helmholtz resonator system is established by using the above process, the genetic algorithm is used to optimize the variables to maximize the transfer loss, and the average transfer loss in the calculation frequency range is defined as the fitness function obj2(y):

[0100]

[0101] In the formula, y is a row vector of the independent variables of the objective function; f1 and f2 are the lower limit and upper limit of the calculation frequency; and Δf is the calculation frequency step;

[0102] According to the number of Helmholtz resonators, there are multiple optimization variables, which are the cross-sectional areas S of the necks and closed cavities of the Helmholtz resonators c v ; the heights l of the necks and closed cavities c 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 main pipe diameter of the working site, the high-frequency muffler frequency band, the muffler installation space, and the manufacturing capacity.

[0103] Embodiment 1

[0104] The embodiment provides a pipe high-frequency resistance muffler based on a Helmholtz resonator, as shown in the figure, specifically comprising an outer pipe 1, a circular pipe 2 connected inside the outer pipe 1 through a plurality of perforated plate cavity structures 3, and the outer pipe 1 and the circular pipe 2 forming a concentric nested structure; the plurality of perforated plate cavity structures 3 are parallel to the axis of the circular pipe 2 and uniformly arranged along the circumference of the circular pipe 2, and 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 to both ends of the outer pipe 1. Figure 1 Embodiment 2

[0105] On the basis of embodiment 1, a plurality of Helmholtz resonators are arranged along the length direction 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 comprises a neck and a closed cavity, and the upstream part of the neck is connected to the connection part of the outer pipe 1 or the circular pipe 2 in a bevel shape. The two ends of the circular pipe 2 are in a rounded corner shape.

[0106] Embodiment 3

[0107] On the basis of embodiment 2, the two ends of the perforated plate cavity structure 3 are in a rounded corner shape, and the middle segment is in a hollow cuboid shape; two opposite outer wall surfaces of the middle segment of the perforated plate cavity structure 3 are connected to the outer pipe 1 and the circular pipe 2, respectively; one of the other two outer wall surfaces is provided with a plurality of round holes, and the plurality of round holes are arranged in a triangular or rectangular array; and the perforated outer wall surfaces of the plurality of perforated plate cavity structures 3 are arranged on the same side.

[0108] The pipe diameter of the connection part of the outer pipe 1 and the perforated plate cavity structure 3 is greater than the pipe diameters of the two ends, the length of the large pipe diameter segment is equal to the length of the middle segment of the perforated plate cavity structure 3, and the large pipe diameter segment is uniformly and transitionally connected to the small pipe diameter segment; and the length of the circular pipe 2 is equal to the length of the perforated plate cavity structure 3.

[0109]

[0110] ​​​Example 4

[0111] This embodiment provides a design method for a high-frequency reactive silencer for pipelines based on a Helmholtz resonator, 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 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 formula for calculating the sound absorption coefficient is:

[0115]

[0116]

[0117]

[0118] In the formula, Let ω = 2πf be the structural constant of the perforated plate cavity, d, t, σ, r, and ωm be the perforation diameter, thickness, perforation rate, acoustic impedance ratio, and acoustic impedance ratio of the perforated plate cavity structure, respectively; h be the wall spacing of the perforated plate cavity structure; η be the viscosity coefficient of the acoustic medium; and c be the sound velocity.

[0119] After calculating the sound absorption coefficient of the perforated plate cavity structure, the perforation diameter d, perforation rate σ, and wall spacing h are optimized using a 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), 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 step size of the calculated frequency.

[0122] The constraints of each variable are determined based on the main pipe diameter, high-frequency noise reduction band, and processing and manufacturing capabilities at the work site.

[0123] Example 6

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

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

[0126]

[0127] l' c =lc + δ1+ δ2 (6)

[0128] Where: c is sound velocity, S c is cross-sectional area of neck; V = S v l v is volume of cavity, S v is cross-sectional area of cavity, l v is height of cavity; l' c is acoustic length of neck, l c is length of neck, δ1and δ2are end correction lengths of neck and main pipe, resonant cavity, δ1= main pipe wall thickness, δ2= 1.7r c , r c is equivalent radius of neck;

[0129] Calculate the transmission loss of Helmholtz resonator and system:

[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 expressed by the transfer matrix, multiply all the transfer matrices to obtain the transfer matrix of the whole system, and then calculate the system loss, which is:

[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 Helmholtz resonator and system;

[0134] The transmission loss of Helmholtz resonator and system 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 area, medium density, sound velocity and Mach number of airflow at the inlet and outlet of the muffler respectively;

[0137] The acoustic unit in the Helmholtz resonator parallel system comprises a Helmholtz resonator and an equal cross-section pipeline between adjacent Helmholtz resonators;

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

[0139]

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

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

[0142]

[0143] wherein, S is the cross-sectional area of the main pipeline.

[0144] Based on the genetic algorithm, the parameters of the Helmholtz resonator parallel system are optimized:

[0145] After the theoretical model of the transfer loss of the Helmholtz resonator system is established by using the above process, the genetic algorithm is used to optimize the variables to maximize the transfer loss, and the average transfer loss in the calculation frequency range is defined as the fitness function obj2(y):

[0146]

[0147] wherein, y is a row vector of the independent variables of the objective function; f1 and f2 are the lower limit and the upper limit of the calculation frequency; and Δf is the calculation frequency step.

[0148] According to the number of the Helmholtz resonators, there are multiple optimization variables, which are the cross-sectional areas S c , S v of the necks and the closed cavities of the Helmholtz resonators; the heights l c , l v of the necks and the closed cavities; the radii R1 and R2 of the outer pipelines and the circular pipelines; and the distance l between the Helmholtz resonators; and the constraint conditions of the variables are determined according to the main pipeline diameter, the high-frequency muffler frequency band, the muffler installation space, and the manufacturing capacity.

Claims

1. A high-frequency reactive silencer for pipelines based on a Helmholtz resonator, characterized in that, The system includes an outer pipe (1), inside which a circular pipe (2) is connected by 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 circumference of the circular pipe (2), and 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); Several Helmholtz resonators are arranged along the length of both 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 parallel Helmholtz resonator system. The Helmholtz resonator includes a neck and a closed cavity, and the connection between the neck of its upstream portion and the outer pipe (1) or the round pipe (2) is obliquely cut. The perforated plate cavity structure (3) has rounded corners at both ends and a hollow cuboid shape in the middle section; the two opposite outer walls of the middle section of the perforated plate cavity structure (3) are connected to the outer pipe (1) and the round pipe (2) respectively; one of the other two outer walls is provided with several round holes, and the several round holes are distributed in a triangular or rectangular array; the perforated outer walls of the several perforated plate cavity structures (3) are all located on the same side.

2. The high-frequency reactive silencer for pipelines based on a Helmholtz resonator according to claim 1, characterized in that, The two ends of the circular tube (2) are rounded.

3. The high-frequency reactive silencer for pipelines based on a Helmholtz resonator according to claim 1, characterized in that, The diameter of the outer pipe (1) connected to the perforated plate cavity structure (3) is greater than the diameter 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 connected to the small diameter section. The length of the round pipe (2) is equal to the length of the perforated plate cavity structure (3).

4. The design method for a high-frequency reactive silencer for pipelines based on a Helmholtz resonator as described in any one of claims 1-3, characterized in that, This includes design methods for perforated plate cavity structures and design methods for parallel Helmholtz resonator systems.

5. The design method for a high-frequency reactive silencer for pipelines based on a Helmholtz resonator as described in claim 4, characterized in that, The design method for 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 calculation formula is: （1） （2） （3） In the formula, The structural constant of the perforated plate cavity is... Angular frequency, These are the perforation diameter, thickness, perforation rate, acoustic impedance ratio, and acoustic impedance ratio of the perforated plate cavity structure, respectively. Indicates the density of the medium; The distance between the walls of the perforated plate cavity structure. The viscosity coefficient of the acoustic medium, Speed ​​of sound; After calculating the sound absorption coefficient of the perforated plate cavity structure, the perforation aperture is then determined based on a genetic algorithm. Perforation rate and wall spacing Optimize to maximize the sound absorption coefficient; define the average transmission loss within the calculation frequency range as the fitness function. , means as follows: （4） In the formula, Let be the row vector of the independent variables of the objective function; and To calculate the lower and upper limits of the frequency; To calculate the frequency step size; The constraints of each variable are determined based on the main pipe diameter, high-frequency noise reduction band, and processing and manufacturing capabilities at the work site.

6. The design method for a high-frequency reactive silencer for pipelines based on a Helmholtz resonator as described in claim 4, characterized in that, The design method for a parallel Helmholtz resonator system is as follows: Resonance frequency of a single Helmholtz resonator The calculation formula is: （5） （6） In the formula: For the speed of sound, This refers to the cross-sectional area of ​​the neck. It is the volume of the cavity. Let be the cross-sectional area of ​​the cavity. The height of the cavity; The acoustic length of the neck. Neck length and The length of the end at the connection between the neck and the main pipe / resonance cavity is adjusted accordingly. The thickness of the main pipe wall. , The equivalent radius of the neck; Calculate the transmission loss of a parallel Helmholtz resonator system: The transfer matrix method is used to divide a complex system into several acoustic units. The relationship between the inlet and outlet of each acoustic unit is represented by a transfer matrix. Multiplying all transfer matrices yields the transfer matrix of the entire system, from which the system loss can be calculated. Specifically: （7） （8） In the formula, and These are the sound pressure and particle velocity between the inlet and outlet of the silencer, respectively. The transfer matrix for the entire parallel Helmholtz resonator system; Helmholtz resonator parallel system transmits losses for: （9） In the formula, and These are the cross-sectional area, medium density, sound velocity, and airflow Mach number of the inlet and outlet of the silencer, respectively. The acoustic unit in a parallel Helmholtz resonator system includes a Helmholtz resonator and a pipe of equal cross-section between adjacent Helmholtz resonators. For a pipe with a constant cross-section, its transfer matrix for: （10） In the formula, The imaginary unit; The Mach number for uniform flow within the main pipe; , For wave number, It is the angular frequency. Indicates frequency; The cross-sectional length is constant. Helmholtz resonator transfer matrix for: （11） In the formula, The cross-sectional area of ​​the main pipe; Parameter optimization of a parallel Helmholtz resonator system based on a genetic algorithm: After establishing the theoretical model of the transmission loss of the Helmholtz resonator system using the above process, the variables are then optimized based on a genetic algorithm to maximize the transmission loss. The average transmission loss within the calculation frequency range is defined as the fitness function. : （12） In the formula, Let be the row vector of the independent variables of the objective function; and To calculate the lower and upper limits of the frequency; To calculate the frequency step size; Depending on the number of Helmholtz resonators, there are several optimization variables, namely the cross-sectional areas of the Helmholtz resonator neck and the enclosed cavity. The height of the neck and the closed cavity ; Radius of external pipes and circular pipes ; and the distance between Helmholtz resonators ; The constraints of each variable are determined based on the main pipe diameter, high-frequency silencing band, silencer installation space, and processing and manufacturing capabilities at the work site.

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