Impedance combined type noise elimination structure parameter design method

Abstract

The invention discloses an impedance combined type noise elimination structure parameter design method, which comprises the following steps of: firstly, determining target noise reduction quantity and target sound absorption center frequency of a resistive noise elimination section and a resonant cavity resistance noise elimination section according to noise source characteristics, and then iteratively adjusting structural parameters of the resistive noise elimination section and parameters of the resonant cavity resistance noise elimination section; and until the deviation between the sound absorption center frequency of the resonant cavity and the target sound absorption center frequency is within an allowable range, and the noise reduction amounts of the resistive noise elimination section and the resonant cavity resistant noise elimination section respectively reach the corresponding target noise reduction amounts. According to the method, parameters of the impedance combined type silencing structure can be effectively, rapidly and reasonably determined, and the problem that an existing impedance combined type silencer lacks a systematic method for coordinating multi-target constraints such as silencing performance, airflow resistance and structural strength is effectively solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of noise reduction technology, more particularly to a parameter design method of impedance combined muffler structure. BACKGROUND

[0002] With the accelerating process of industrialization and urbanization, the problem of low-frequency noise pollution generated in the operation of mechanical equipment, power system and electric power equipment is becoming increasingly serious, which has a significant impact on the health of residents, the stability of equipment and the comfort of the environment. As the core component of noise control, the performance of the muffler directly determines the noise reduction effect and the adaptability of the application scene.

[0003] Traditional muffler structures are mainly divided into two categories: resistive mufflers and reactive mufflers. The resistive muffler dissipates sound energy through porous sound-absorbing materials, which is effective for high-frequency noise, but insufficient for low-frequency noise and easily affected by airflow erosion. The reactive muffler reflects sound waves based on the principle of acoustic impedance mismatch, which is effective for low-frequency noise, but has the problems of narrow frequency band and large structure size.

[0004] In recent years, impedance combined muffler structures have shown significant advantages in widening the noise reduction frequency band and improving the compactness of the structure by integrating resistive and reactive muffling mechanisms, utilizing stepwise matching of acoustic impedance and multi-modal coupling effects.

[0005] However, the design of impedance combined mufflers in the prior art still has the following problems:

[0006] (1) Lack of systematic methods to coordinate multiple target constraints such as noise reduction performance, airflow resistance and structural strength, resulting in insufficient noise reduction efficiency and engineering applicability under actual working conditions;

[0007] (2) For wide-frequency variable-condition noise (such as rotating machinery, internal combustion engine exhaust, etc.), the existing design process relies on a large number of experimental iterations, resulting in long development cycles and high costs.

[0008] Therefore, how to overcome the above problems is a problem that needs to be solved by those skilled in the art. SUMMARY

[0009] Therefore, the present application provides a parameter design method of impedance combined muffler structure, which aims to effectively, quickly and accurately determine the impedance combined muffler structure parameters suitable for actual working conditions.

[0010] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0011] A parameter design method of impedance combined muffler structure, comprising,

[0012] determining the target noise reduction amount and the target sound absorption center frequency of the resistive muffler section and the resonant cavity reactive muffler section according to the characteristics of the noise source,

[0013] The structural parameters of the resistive noise reduction section and the parameters of the reactive noise reduction section of the resonant cavity are iteratively adjusted until the deviation between the sound absorption center frequency of the resonant cavity and the target sound absorption center frequency is within the allowable range, and the noise reduction of the resistive noise reduction section and the reactive noise reduction section of the resonant cavity respectively reaches the corresponding target noise reduction.

[0014] In one optional embodiment, determining the target noise reduction amount of the resistive noise reduction section and the resonant cavity reactive noise reduction section based on the characteristics of the noise source includes:

[0015] Determine the sound pressure level of the noise source, and use the difference in sound pressure level between the inlet and outlet of the impedance-combined silencing structure as the total noise reduction;

[0016] Based on the total noise reduction, the noise reduction amount of the resistive noise reduction section and the noise reduction amount of the resonant cavity reactive noise reduction section are determined respectively using the following formulas;

[0017] ΔJ1+ΔJ2=ΔJ0

[0018] ΔJ1=β*ΔJ0

[0019] In the formula, ΔJ1 is the noise reduction of the resistive noise reduction section, ΔJ2 is the noise reduction of the reactive noise reduction section of the resonant cavity, ΔJ0 is the total noise reduction, and β is the relationship coefficient. Preferably, it is 0.8 to 0.9.

[0020] In one optional embodiment, determining the target sound absorption center frequency based on noise source characteristics includes:

[0021] The frequency distribution characteristics of the noise source are analyzed, and the target sound absorption center frequency is determined based on the frequency distribution characteristics of the sound source.

[0022] In one optional embodiment, the structural parameters of the resistive silencing section include the normal incident sound absorption coefficient α, the perimeter P of the sound-absorbing veneer, the cross-sectional area S, and the length L;

[0023] The noise reduction of the resistive noise reduction section is:

[0024]

[0025] In one optional embodiment, the parameters of the resonant cavity resistive noise reduction section include the microporous plate aperture d, plate thickness l, porosity k, resonant cavity volume V, and airflow channel cross-sectional area A;

[0026] The noise reduction of the resonant cavity reactive anechoic section is:

[0027]

[0028] In an optional embodiment, the sound absorption center frequency of the resonant cavity is calculated using the following formula:

[0029]

[0030] In the formula, A is the cross-sectional area of ​​the airflow channel of the resonant cavity, k is the porosity, l is the plate thickness, d is the pore diameter of the microporous plate, and V is the volume of the resonant cavity.

[0031] In one optional embodiment, the deviation between the resonant cavity absorption center frequency and the target absorption center frequency is allowed to be no more than 10%.

[0032] In one optional embodiment, the noise reduction of the resistive noise reduction section and the resonant cavity reactive noise reduction section respectively reaches the corresponding target noise reduction, including the noise reduction of the resistive noise reduction section and the resonant cavity reactive noise reduction section exceeding the corresponding target noise reduction by 20% to 50% respectively.

[0033] As can be seen from the above technical solution, the present invention discloses a method for designing impedance-combined noise reduction structure parameters. By analyzing the characteristics of the noise source, calculating the sound pressure level and frequency distribution of the sound source, determining the overall noise reduction amount and the sound absorption center frequency, further determining the noise reduction target values ​​and constraints of the resistive noise reduction section and the resonant cavity reactive noise reduction section, and setting the initial resistive noise reduction section structure parameters and the resonant cavity reactive noise reduction section parameters, calculating the noise reduction amount and sound absorption center frequency of each section, and judging whether the noise reduction requirements are met. If not, the method returns to continue adjusting the parameters until the noise reduction requirements are met.

[0034] Compared with the prior art, the advantages of this application are as follows:

[0035] 1. By establishing a coupling equation for the noise reduction of the resistive and reactive sections, over-design of a single section is avoided while ensuring the overall noise reduction. Combined with precise locking of the sound absorption center frequency, the reactive section focuses on the low-frequency main energy region, while the resistive section covers the mid-to-high frequencies, thereby achieving a balanced distribution of noise reduction across the entire frequency band.

[0036] 2. Automatic execution of iterative optimization transforms the traditional trial-and-error process that relies on manual adjustments into an algorithm-driven process, which can effectively shorten the development cycle and reduce costs;

[0037] This invention can effectively, quickly, and reasonably determine the structural parameters of impedance combination silencers, effectively solving the problem that current impedance composite silencers lack a systematic method to coordinate multiple objectives such as silencer performance, airflow resistance, and structural strength. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0039] Figure 1This is a schematic diagram of the impedance combination noise reduction structure of the present invention;

[0040] Figure 2 This is a flowchart illustrating the impedance combination silencing structure parameter design method of the present invention. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0043] To address the shortcomings of existing technologies, this application provides a method for designing parameters of an impedance-combined noise reduction structure. The impedance-combined noise reduction structure is as follows: Figure 1 As shown, it includes a resistive noise reduction section and a resonant cavity reactive noise reduction section.

[0044] In one embodiment, the method includes the following steps:

[0045] The target noise reduction amount and target sound absorption center frequency of the resistive silencing section and the resonant cavity reactive silencing section are determined based on the characteristics of the noise source.

[0046] The structural parameters of the resistive noise reduction section and the parameters of the reactive noise reduction section of the resonant cavity are iteratively adjusted until the deviation between the sound absorption center frequency of the resonant cavity and the target sound absorption center frequency is within the allowable range, and the noise reduction of the resistive noise reduction section and the reactive noise reduction section of the resonant cavity respectively reaches the corresponding target noise reduction.

[0047] In some implementation schemes, the steps are as follows Figure 2 As shown, noise source characteristics are first analyzed, and the total noise reduction is determined by the sound pressure level of the sound source. That is, the difference in sound pressure level between the inlet and outlet of the impedance combination silencer structure is the total noise reduction. In one embodiment, the sound pressure level of the sound source is the A-weighted sound pressure level, and the total noise reduction is the difference in A-weighted sound pressure level between the inlet and outlet of the silencer, in dB(A).

[0048] Then, based on the total noise reduction, the noise reduction amount of the resistive noise reduction section and the noise reduction amount of the resonant cavity reactive noise reduction section are determined respectively according to the following formula;

[0049] ΔJ1+ΔJ2=ΔJ0

[0050] ΔJ1=β*ΔJ0

[0051] In the formula, ΔJ1 is the noise reduction of the resistive noise reduction section, ΔJ2 is the noise reduction of the reactive noise reduction section of the resonant cavity, ΔJ0 is the total noise reduction, and β is the relationship coefficient; preferably 0.8 to 0.9.

[0052] Furthermore, the frequency distribution characteristics of the noise source are analyzed to determine the sound absorption center frequency, which refers to the sound absorption center frequency of the reactive resonant cavity. In this embodiment, the frequency distribution characteristics are analyzed by octave band, and the center frequency points are: 31.5Hz, 63Hz, 125Hz, 250Hz, 500Hz, 1000Hz, 2000Hz, 4000Hz, and 8000Hz.

[0053] In some implementation schemes, initial parameters are set for the resistive silencing section structure and the resonant cavity reactive silencing section, and the noise reduction amount and sound absorption center frequency of each section are calculated to further determine whether the noise reduction requirements are met. If so, the parameter adjustment ends; otherwise, the adjustment of the silencer parameters continues.

[0054] This application uses the above iterative adjustments until the deviation between the sound absorption center frequency of the resonant cavity and the target sound absorption center frequency is within the allowable range, and the noise reduction of the resistive noise reduction section and the reactive noise reduction section of the resonant cavity respectively reaches the corresponding target noise reduction.

[0055] In this embodiment, the structural parameters of the resistive noise reduction section include the normal incident sound absorption coefficient α; the perimeter P of the sound-absorbing surface portion (in meters); the cross-sectional area S of the sound-absorbing surface portion (in square meters); and the length L of the sound-absorbing surface portion along the airflow direction (in meters).

[0056] The parameters for the resonant cavity reactive anechoic section include: microporous plate orifice diameter d (m); microporous plate thickness l (m); microporous plate porosity k (%); and resonant cavity volume V (m³). 3 The cross-sectional area A of the airflow channel in the resonant cavity is in square meters.

[0057] When setting the above initial parameters in this application, the actual constraints of the project should be taken into account and the parameters should be set reasonably.

[0058] Furthermore, the noise reduction amount and sound absorption center frequency of each segment are calculated and compared with the target value to determine whether the noise reduction requirements are met. If not, the process returns to continue adjusting the parameters until the noise reduction requirements are met.

[0059] The noise reduction of the resistive noise reduction section is:

[0060]

[0061] The noise reduction of the resonant cavity reactive anechoic section is:

[0062]

[0063] The center frequency of sound absorption in the resonant cavity is:

[0064]

[0065] To further optimize the above technical solution, in this embodiment, the calculated noise reduction value needs to have a certain margin compared with the target design value to ensure a certain tolerance capability. The preferred range for the noise reduction is 20% to 50%, and the frequency deviation is ≤10%.

[0066] In one specific implementation, noise reduction design is carried out for a 110kV indoor substation. The main noise sources include low-frequency noise from the transformer and mid- and high-frequency noise from the exhaust fan. First, the characteristics of the noise sources in the main transformer room are analyzed. The A-weighted sound pressure level and octave band analysis results are shown in Table 1 below.

[0067] Table 1

[0068]

[0069] In this embodiment, according to the "Emission Standard for Environmental Noise at the Boundary of Industrial Enterprises" (GB 12348-2008), the nighttime noise at the factory boundary should be less than 50 dB(A), and the indoor sound source size is 76.2 dB(A). To ensure that the noise at the factory boundary meets the standard, the overall noise reduction of the silencer ΔJ0 should be at least 30 dB(A). If β is taken as 0.80, then the noise reduction of the resistive silencer section ΔJ1 is 24 dB(A), and the noise reduction of the resonant cavity reactive silencer section ΔJ2 is 6 dB(A).

[0070] According to the spectral characteristics in Table 1, the sound absorption center frequency of the resonant cavity should be in the range of 250Hz to 500Hz, with a value of 400Hz.

[0071] In this embodiment, the resistive silencing section adopts a sheet-type silencing structure, with the following initial parameters: the thickness h of the silencing sheet is 0.1m, the width w of the silencing sheet is 0.7m, the length L of the silencing sheet along the airflow direction is 1m, and the sound-absorbing material inside the silencing sheet is commercially available ultrafine glass wool, with an average sound absorption coefficient α of approximately 0.7. Therefore, the perimeter P of the sound-absorbing surface part is P = 2*(w+h) = 1.6m, and the cross-sectional area S of the sound-absorbing surface part is S = w*h = 0.07m². 2 .

[0072] Substitute the parameters above to calculate the noise reduction ΔJ1 of the resistive noise reduction section:

[0073]

[0074] In this embodiment, considering the deviation between actual engineering and theoretical calculation, the theoretical calculation value of noise reduction should have a certain margin. In this embodiment, the design value of noise reduction of the resistive noise reduction section is 24dB(A), and the theoretical calculation value is 29dB(A), leaving a margin of 5dB(A), which is about 20%, which is acceptable.

[0075] Furthermore, the parameters for the resonant cavity's reactive silencing section are set as follows: microporous plate hole diameter d is 8mm; microporous plate thickness l is 2mm; microporous plate opening ratio k is 10%; resonant cavity volume V is 0.056m³. 3 The cross-sectional area A of the airflow channel in the resonant cavity is 0.14 m². 2 .

[0076] The noise reduction ΔJ2 of the resonant cavity reactive anechoic section is calculated using the following formula:

[0077]

[0078] The center frequency f of the resonant cavity absorption r It can be calculated using the following formula:

[0079]

[0080] In this implementation, the design value for noise reduction of the resistive anechoic section is 6 dB(A), the theoretical calculation value is 7.6 dB(A), leaving a margin of about 26%, and the calculated value of the center frequency deviates by about 4.5%, which meets the design requirements.

[0081] This embodiment, through automatic iterative optimization of impedance combination silencing structure parameters, can significantly shorten the development cycle and reduce costs, thereby effectively, quickly, and reasonably determining the impedance combination silencing structure parameters.

[0082] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0083] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for designing parameters of an impedance-combined noise reduction structure, characterized in that, The target noise reduction amount and target sound absorption center frequency of the resistive silencing section and the resonant cavity reactive silencing section are determined based on the characteristics of the noise source. The structural parameters of the resistive noise reduction section and the parameters of the reactive noise reduction section of the resonant cavity are iteratively adjusted until the deviation between the sound absorption center frequency of the resonant cavity and the target sound absorption center frequency is within the allowable range, and the noise reduction of the resistive noise reduction section and the reactive noise reduction section of the resonant cavity respectively reaches the corresponding target noise reduction.

2. The method for designing impedance-combined noise reduction structure parameters according to claim 1, characterized in that, The target noise reduction amount for the resistive silencing section and the resonant cavity reactive silencing section is determined based on the characteristics of the noise source, including: Determine the sound pressure level of the noise source, and use the difference in sound pressure level between the inlet and outlet of the impedance-combined silencing structure as the total noise reduction; Based on the total noise reduction, the noise reduction amount of the resistive noise reduction section and the noise reduction amount of the resonant cavity reactive noise reduction section are determined respectively using the following formulas; ΔJ1+ΔJ2=ΔJ0 ΔJ1=β*ΔJ0 In the formula, ΔJ1 is the noise reduction of the resistive noise reduction section, ΔJ2 is the noise reduction of the reactive noise reduction section of the resonant cavity, ΔJ0 is the total noise reduction, and β is the relationship coefficient.

3. The method for designing impedance-combined noise reduction structure parameters according to claim 1, characterized in that, Determining the target sound absorption center frequency based on the characteristics of the noise source includes: The frequency distribution characteristics of the noise source are analyzed, and the target sound absorption center frequency is determined based on the frequency distribution characteristics of the sound source.

4. The method for designing impedance-combined noise reduction structure parameters according to claim 1, characterized in that, The structural parameters of the resistive silencing section include the normal incident sound absorption coefficient α, the perimeter P of the sound-absorbing veneer, the cross-sectional area S, and the length L; The noise reduction of the resistive noise reduction section is:

5. The method for designing impedance-combined noise reduction structure parameters according to claim 1, characterized in that, The parameters of the resonant cavity resistive silencing section include the micro-perforated plate diameter d, plate thickness l, porosity k, resonant cavity volume V, and airflow channel cross-sectional area A; The noise reduction of the resonant cavity reactive anechoic section is:

6. The method for designing impedance-combined noise reduction structure parameters according to claim 1, characterized in that, The formula for calculating the sound absorption center frequency of the resonant cavity is: In the formula, A is the cross-sectional area of ​​the airflow channel of the resonant cavity, k is the porosity, l is the plate thickness, d is the pore diameter of the microporous plate, and V is the volume of the resonant cavity.

7. The method for designing impedance-combined noise reduction structure parameters according to claim 1, characterized in that, The deviation between the resonant cavity absorption center frequency and the target absorption center frequency is allowed to be no more than 10%.

8. The method for designing impedance-combined noise reduction structure parameters according to claim 1, characterized in that, The noise reduction of the resistive noise reduction section and the resonant cavity reactive noise reduction section respectively reaches the corresponding target noise reduction, including the noise reduction of the resistive noise reduction section and the resonant cavity reactive noise reduction section exceeding the corresponding target noise reduction by 20% to 50% respectively.

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