Slit type multi-temperature acoustic metamaterial based on porous matrix

Abstract

The invention discloses a slit type multi-temperature acoustic metamaterial based on a porous substrate, and particularly relates to the technical field of metamaterials, the metamaterial is a three-dimensional structure formed by combining and arranging a plurality of unit cell structures, and the edge part of the metamaterial is a half unit cell structure; the unit cell structure comprises an inner base body and an outer base body, a slit type perforation channel is formed between the inner base body and the outer base body, and the inner base body and the outer base body are of a unit cell structure. The slit-type multi-temperature acoustic metamaterial based on the multi-scale design of the porous matrix has the advantage of good designability, the geometrical shape and the material of the metamaterial can be customized and designed to a certain extent according to requirements, and the physical geometrical parameters of the metamaterial can be adjusted according to specific requirements, so that the reasonable and excellent sound absorption effect in different temperature environments can be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of metamaterials, and in particular to a slit-type multi-temperature acoustic metamaterial based on a porous matrix. Background Art

[0002] Nowadays, the rapid development of industrialization has made the noise problem more and more prominent. Noise pollution has always been a major challenge faced by people. Solving the noise problem is urgent. Among them, low-frequency noise has become a hot topic for researchers due to its long propagation distance and difficulty in dissipation. However, traditional sound-absorbing materials cannot meet the dissipation capacity of low-frequency sound waves. Therefore, people have put forward new requirements for acoustic noise reduction. Nowadays, the introduction of acoustic metamaterials has brought new ideas for low-frequency noise reduction. Porous materials have great application potential in controlling noise propagation. In traditional porous material noise reduction, most of them use a single-hole porous material matrix, which is a structure containing a large number of pores and has a certain blocking effect on high-frequency sound waves. However, its performance is still limited in the face of low-frequency and long-wavelength sounds.

[0003] In order to overcome the shortcomings of the above-mentioned traditional porous materials in low-frequency sound absorption, a lot of improvement work has been carried out. Composite structures based on porous materials have been proposed to achieve low-frequency sound absorption performance. At the same time, multi-scale designs based on porous materials have also been studied and discussed. Straight seam perforations and open hole perforations on the microporous material matrix can improve low-frequency sound absorption performance and reduce the peak frequency of sound absorption.

[0004] In addition to the above research work at room temperature, in fact, in many cases, equipment must absorb energy and reduce noise when working in a high temperature environment, such as aircraft engine sound insulation gaskets and aircraft hot end silencer elements. The impact of temperature on mechanical equipment is very significant, especially in a high temperature environment. In this case, the properties of air and materials will also change greatly due to temperature changes. For air, temperature affects its density and sound speed. For rigid porous skeleton materials, temperature affects its static flow resistivity and ultimately affects its acoustic properties. Therefore, the design of acoustic materials should match the working environment temperature. Summary of the invention

[0005] In order to solve the problem of low-frequency noise in high-temperature environments, it is crucial to study the acoustic performance of sound-absorbing materials in high-temperature environments. Whether at room temperature or high temperature, traditional porous materials have poor absorption capacity for low-frequency sound waves, and multi-scale design based on porous material matrix can solve the defects of traditional porous materials in this regard. Therefore, multi-scale design is a method worth learning from to adapt to multi-temperature acoustic environments for energy absorption and noise reduction.

[0006] To this end, the present invention provides a slit-type multi-temperature acoustic metamaterial based on a porous matrix to solve the problems raised in the background technology.

[0007] In order to achieve the above-mentioned purpose, the present invention provides the following technical solution: a slit-type multi-temperature acoustic metamaterial based on a porous matrix, wherein the metamaterial is a three-dimensional structure arranged in combination of multiple unit cell structures, and its edge portion is a half unit cell structure; the unit cell structure includes an inner matrix and an outer matrix, a slit-type perforated channel is formed between the inner matrix and the outer matrix, and the inner matrix and the outer matrix are a unit cell structure.

[0008] Preferably, the inner matrix and the outer matrix are both made of high flow resistance matrix materials.

[0009] Preferably, in the vertical direction, the metamaterial is symmetrical up and down.

[0010] Preferably, the inner matrix adopts an inner cylindrical porous matrix, the outer matrix adopts an outer cylindrical perforated porous matrix, the slit-type perforated channel is a circular slit-type perforated channel, and the metamaterial arranges M unit cell structures in parallel in a lateral regularity; the adjacent sides are arranged in parallel in a longitudinal regularity as (M-1) unit cell structures, which are respectively arranged in the middle of the adjacent unit cell structures on the upper and lower sides, and finally N units are arranged according to this periodic rule to form an overall structure; wherein M and N are both positive integers not less than 1.

[0011] Preferably, the diameter d of the inner cylindrical porous matrix is ​​28 mm, the diameter D of the outer cylindrical perforated porous matrix is ​​49 mm, the overall height H is 60 mm, and the thickness b of the annular slit-type perforated channel is 1 mm.

[0012] Preferably, the slit-type perforated channel can effectively absorb low-frequency sound waves less than 500 Hz at a normal temperature of 20°C.

[0013] Preferably, the slit-type perforated channel can achieve effective sound absorption of low-frequency sound waves less than 500 Hz in high temperature environments of 200° C., 300° C., and 500° C.

[0014] The present invention has the following advantages:

[0015] (1) The present invention utilizes the advantages of the designed annular slit-type perforated channel to achieve effective sound absorption of low-frequency sound waves (≤500Hz) at room temperature (20°C), and utilizes the porous characteristics of the material itself to effectively absorb sound waves in the medium and high frequency ranges, achieving excellent noise reduction performance.

[0016] (2) The present invention utilizes the advantages of the designed annular slit-type perforated channel to achieve effective sound absorption of low-frequency sound waves (≤500Hz) in a high-temperature environment (200°C, 300°C, 500°C), and utilizes the porous characteristics of the material itself to effectively absorb sound waves in the medium and high frequency ranges, achieving excellent noise reduction performance.

[0017] (3) The slit-type multi-temperature acoustic metamaterial designed by the present invention based on the multi-scale design of the porous matrix is ​​usually relatively light and has excellent mechanical properties. When subjected to external pressure or impact, the overall cylindrical distribution configuration can effectively disperse the stress and improve the overall strength and rigidity.

[0018] (5) The slit-type multi-temperature acoustic metamaterial based on the multi-scale design of the porous matrix designed in the present invention has the advantage of good designability. Its geometric shape and material can be customized according to certain needs, and its physical geometric parameters can be adjusted according to specific needs to achieve reasonable and excellent sound absorption effects under different temperature environments.

[0019] (6) Based on metamaterial design technology, the process of manufacturing the circular slit-shaped perforated porous matrix is ​​relatively simple and can adapt to different design requirements and production processes. The cost of raw materials is low, which makes it economical in commercial applications. It can also be combined with other functions, such as fire prevention and dehumidification, to meet complex application requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A two-dimensional simplified schematic diagram of a unit cell structure of a slit-type multi-temperature acoustic metamaterial based on a multi-scale design of a porous matrix according to the present invention;

[0021] Figure 2-3 Model diagrams of the three-dimensional unit cells of the slit-type multi-temperature acoustic metamaterial based on the multi-scale design of the porous matrix before and after the assembly of the present invention;

[0022] Figure 4-5 The three-dimensional overall front and side views of the circular slit-type high-temperature perforated porous metamaterial for sound absorption and noise reduction at room temperature (20°C) or high temperature (200°C, 300°C, 500°C) are arranged according to the combination arrangement rules;

[0023] Figure 6 The sound absorption coefficient curve of the circular slit-type perforated high-temperature porous metamaterial for sound absorption and noise reduction at room temperature (20°C) or high temperature (200°C, 300°C, 500°C) is obtained by arranging according to the parallel combination rule;

[0024] Figure 7 The sound absorption curves of unit cells of three different configurations (APM): a porous matrix without perforations; CRPM: a cylindrical perforated porous matrix; CRPPM: a cylindrical porous matrix added to CRPM to form a circular slit-type perforated porous matrix) at different temperatures. DETAILED DESCRIPTION

[0025] The following is a description of the implementation of the present invention by specific embodiments. People familiar with the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Example: Figure 1 As shown, since the metamaterial has the characteristic of freely designing size parameters, the metamaterial is a slit-type acoustic metamaterial based on a porous matrix multi-scale, which is composed of an inner cylindrical porous matrix b and an outer cylindrical perforated porous matrix a. When a certain size of sound is transmitted into the metamaterial through the outside air, for medium and high frequency sound waves, due to the short wavelength of the sound wave, the micropores on the top of the metamaterial matrix are easy to couple and resonate with the sound wave with a shorter wavelength, resulting in thermal viscous dissipation, converting the violent dissipation of sound energy into internal energy, and achieving the goal of medium and high frequency sound absorption. For low frequency sound waves, the wavelength is short, and they will not directly interact with the micropores on the top of the porous matrix, but enter the bottom of the metamaterial through the annular slit perforated channel, and then produce a pressure diffusion effect at the interface between the annular slit perforated channel and the inner cylindrical porous matrix b or the outer cylindrical perforated porous matrix a, thereby achieving effective sound absorption of low frequency sound waves. Based on this principle, when stimulated by external sound waves at normal or high temperature environments, most of the energy of the external sound waves can be consumed, thereby achieving the goal of sound absorption and noise reduction.

[0027] The diameter d of the inner cylindrical porous substrate b is 28 mm, the diameter D of the outer cylindrical perforated porous substrate a is 49 mm, the overall height H is 60 mm, and the thickness b of the annular slit-type perforated channel is 1 mm.

[0028] like Figure 2-3 As shown, the slit-type multi-temperature acoustic metamaterial structure based on the multi-scale design of the porous matrix includes: a circular slit-type perforated channel, an inner cylindrical porous matrix b, and an outer cylindrical perforated porous matrix a. The circular slit-type perforated porous metamaterial can be regarded as a combination of the outer cylindrical perforated porous matrix a and the inner cylindrical porous matrix b.

[0029] like Figure 4-5 As shown, the slit-type multi-temperature acoustic metamaterial structure based on the multi-scale design of the porous matrix is ​​arranged according to the final parallel combination rule.

[0030] The metamaterial has M unit cell structures arranged in parallel in a lateral pattern; (M-1) unit cell structures are arranged in parallel on adjacent sides in a longitudinal pattern, respectively arranged in the middle of the adjacent unit cell structures on the upper and lower sides, and finally N units are arranged according to this periodic pattern to form an overall structure; wherein M and N are both positive integers not less than 1.

[0031] like Figure 6 As shown in the figure, a dual-pore theoretical model and a high-temperature model of the porous matrix are established, and the sound absorption coefficient of the circular slit perforated porous material under four different temperature conditions is numerically simulated by combining the numerical simulation software COMSOL. It can be seen that the sound absorption peak frequencies corresponding to the theoretical and numerical sound absorption curves of the structure at different temperatures (20℃, 100℃, 300℃ and 500℃) are 295Hz, 330Hz, 412Hz and 485Hz, respectively, indicating that the metamaterial has good sound absorption ability for low-frequency sound waves at different temperatures. With the increase of ambient temperature, the sound absorption bandwidth of the material (sound absorption coefficient>0.5) continues to widen. This is attributed to the fact that the circular slit provides an additional propagation path for low-frequency sound waves, thereby generating energy dissipation at the bottom of the material through the pressure diffusion effect. It shows that in actual specific applications, for different high-temperature environments, the structure can effectively absorb low-frequency sound waves and achieve the expected noise reduction range.

[0032] like Figure 7 As shown in the figure, the sound absorption performance at different temperatures is given respectively. For these three types of configurations, the theoretical calculation and numerical results at different temperatures are well matched in the figure. Compared with the other two materials, CRPPM has excellent high-temperature and low-frequency sound absorption performance at different temperatures, while APM has poor sound absorption performance at different temperatures. Compared with CRPPM, CPPM has better broadband sound absorption performance.

[0033] In order to meet the actual needs of the project and meet the different high-temperature environments of equipment operation, the porous matrix is ​​simply designed with circular slit perforations and parallel combinations to achieve the expected noise reduction range that meets different high-temperature environments. In this way, a circular slit-type perforated acoustic porous metamaterial with good high-temperature and low-frequency sound absorption performance is obtained.

[0034] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A slit-type multi-temperature acoustic metamaterial based on a porous matrix, characterized by: The metamaterial is a three-dimensional structure composed of a plurality of unit cell structures, and its edge portion is a half unit cell structure; the unit cell structure comprises an inner matrix and an outer matrix, a slit-type perforated channel is formed between the inner matrix and the outer matrix, and the inner matrix and the outer matrix are a unit cell structure.

2. The porous matrix-based slit-type multi-temperature acoustic metamaterial according to claim 1, characterized in that: The inner matrix and the outer matrix are both made of high flow resistance matrix materials.

3. The porous matrix-based slit-type multi-temperature acoustic metamaterial according to claim 1, characterized in that: In the vertical direction, the metamaterial is symmetrical up and down.

4. The porous matrix-based slit-type multi-temperature acoustic metamaterial according to claim 1, characterized in that: The inner matrix adopts an inner cylindrical porous matrix (b), the outer matrix adopts an outer cylindrical perforated porous matrix (a), the slit-type perforated channel is a circular slit-type perforated channel, and the metamaterial arranges M unit cell structures in parallel in a lateral regularity; the adjacent sides are arranged in parallel in a longitudinal regularity as (M-1) unit cell structures, which are respectively arranged in the middle of the adjacent unit cell structures on the upper and lower sides, and finally N units are arranged according to this periodic regularity to form an overall structure; wherein M and N are both positive integers not less than 1.

5. The porous matrix-based slit-type multi-temperature acoustic metamaterial according to claim 4, characterized in that: The diameter d of the inner cylindrical porous matrix (b) is 28 mm, the diameter D of the outer cylindrical perforated porous matrix (a) is 49 mm, the overall height H is 60 mm, and the thickness b of the annular slit-type perforated channel is 1 mm.

6. The porous matrix-based slit-type multi-temperature acoustic metamaterial according to claim 4, characterized in that: The slit-type perforated channel can effectively absorb low-frequency sound waves less than 500 Hz at a normal temperature of 20°C.

7. The porous matrix-based slit-type multi-temperature acoustic metamaterial according to claim 4, characterized in that: The slit-type perforated channel can effectively absorb low-frequency sound waves less than 500 Hz in high temperature environments of 200° C., 300° C., and 500° C.

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