Variable back cavity acoustic liner sound absorption structure coupled with mechanical impedance

Abstract

The invention relates to a variable back cavity acoustic liner sound absorption structure coupled with mechanical impedance, and belongs to the technical field of vibration noise control such as combustion chamber unstable combustion suppression and fairing noise elimination. Comprising a back cavity fixing plate, an N-shaped thin plate and a perforated plate, the perforated plate is arranged on the surface, making contact with the working environment, of the front portion of the back cavity fixing plate, and the N-shaped thin plate is arranged between the wall face of the top of the back cavity fixing plate and the perforated plate. By coupling the N-shaped thin plate in the acoustic liner, multi-band sound absorption optimization can be realized in a limited space. The low-frequency-band sound absorption performance is improved through resonance of the thin plate, meanwhile, the depth of the back cavity can be changed, the back cavities of different sizes are separated, and the sound absorption effect under multiple frequency bands is achieved in one sound liner structure. The variable back cavity acoustic liner sound absorption structure coupled with the mechanical impedance is easy to install, a thin plate with proper elasticity and damping needs to be selected, and the variable back cavity acoustic liner sound absorption structure coupled with the mechanical impedance is suitable for working conditions without flow and with flow and high-temperature working conditions.

Description

Technical Field

[0001] The invention relates to the technical field of vibration noise control such as combustion chamber unstable combustion suppression and fairing silencing, and in particular to a variable back cavity sound liner sound absorption structure coupled with mechanical impedance. Background Art

[0002] The impact of noise is not limited to the harm to the physiological and psychological systems of the human body, but also has harm to environmental optimization and system stability. The design and use of acoustic linings are derived from the needs of noise control and acoustic performance optimization. With the advancement of industrial technology and the enhancement of environmental protection awareness, its application scope continues to expand. In the aviation and automotive industries, the application of acoustic linings can significantly reduce the noise generated by engine combustion, airflow, structural vibration, etc., and provide passengers with a more comfortable environment and riding experience. At the same time, there is an unstable state in the combustion system in the engine, and the cause may be the coupling of combustion noise and heat release pulsation. Therefore, setting a specific structure of acoustic lining in the system can realize the regulation of acoustic performance and avoid structural vibration damage caused by unstable combustion. The application of acoustic linings usually works based on the principle of Helmholtz resonance or impedance matching, which is of great significance to reducing equipment noise.

[0003] The structural forms of acoustic liners are varied and are usually matched according to application requirements and noise reduction targets. The design concept is to absorb sound waves and control and optimize acoustic performance through the combination of materials and structural optimization. Traditional engine acoustic liners are mainly composed of perforated plates and back cavities, and different sound absorption characteristics are controlled by changing the structural parameters. However, due to the application scenarios, traditional structural acoustic liners are highly dependent on spatial structures. Combining the principle of mechanical impedance to achieve sound absorption through resonance, mechanical impedance thin plates are coupled to the traditional acoustic lining structure to break the fixed structure, and use their damping and elastic properties to improve and regulate the sound absorption performance of the acoustic lining in a limited space.

[0004] Therefore, it is necessary to develop a variable back cavity sound absorbing structure with coupled mechanical impedance to solve the above problems. Summary of the invention

[0005] The object of the present invention is to provide a variable back cavity sound liner sound absorption structure coupled with mechanical impedance, which introduces mechanical impedance by adding an "N"-shaped thin plate to achieve low-frequency sound absorption and sound liner sound absorption frequency band regulation.

[0006] In order to achieve the above object, the present invention provides the following technical solutions: A variable back cavity sound liner sound absorption structure with coupled mechanical impedance includes a back cavity fixing plate, an "N"-shaped thin plate and a perforated plate. The perforated plate is arranged on the surface of the front part of the back cavity fixing plate that contacts the working environment, and the "N"-shaped thin plate is arranged between the top wall connecting the back cavity fixing plate and the perforated plate.

[0007] Furthermore, the “N”-shaped thin plates are staggered between the perforated plates and the back cavity top plate, which can separate the sound lining back cavity, thereby having a sound absorption effect on multiple frequency bands.

[0008] Furthermore, the “N”-shaped thin plate constructs a plurality of back cavities, and the combined resonance of the perforated plate and the back cavities can be used to dissipate acoustic energy in different frequency bands.

[0009] Furthermore, one end of the "N"-shaped thin plate is fixed to the back cavity fixing plate, and the other end of the "N"-shaped thin plate is connected to a perforated plate. Under the action of airflow, the elasticity of the perforated plate can be used to adjust the upper and lower positions of the perforated plate to change the back cavity depth.

[0010] Furthermore, the distortion angle of the “N”-shaped thin plate can be adjusted to adapt to the floating of different depths of the back cavity.

[0011] Furthermore, the “N”-shaped thin plate can be replaced with different physical properties and structures according to airflow conditions to achieve changes in different back cavity depths and weaken the sound energy in the target frequency band.

[0012] The beneficial effects of the present invention are: 1. A variable back cavity sound liner sound absorption structure coupled with mechanical impedance disclosed by the present invention can weaken the noise in the medium and low frequency bands by utilizing the resonance of the "N"-shaped thin plate; 2. A variable back cavity sound liner sound absorption structure coupled with mechanical impedance disclosed by the present invention can be applied to both flow and no flow conditions and can be arranged circumferentially on the outside of the cylinder; 3. A variable back cavity sound lining sound absorption structure coupled with mechanical impedance disclosed by the present invention can achieve sound absorption in multiple frequency bands by adjusting the structural parameters of the perforated plate and the thin plate, that is, forming multiple sound absorption peaks to cope with noise under different operating conditions; 4. The variable back cavity sound lining sound absorption structure coupled with mechanical impedance disclosed by the present invention can realize the variation and adjustment of the back cavity depth by utilizing the "N"-shaped elastic change under the action of airflow, thereby effectively broadening the target sound absorption frequency band; 5. The present invention discloses a variable back cavity sound absorbing structure with coupled mechanical impedance. The structure can be made of metal material and can withstand the scorching of high-temperature gas. It absorbs sound by structural changes and does not use traditional porous sound absorbing materials such as fiber. It is environmentally friendly and durable.

[0013] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, some of the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0015] Figure 1 It is a side sectional view of the device of the present invention.

[0016] Figure 2 This is a bottom view of the device.

[0017] Figure 3 It is a top view of the device.

[0018] Among them, 1. Back cavity fixing plate; 2. "N" type thin plate; 3. Perforated plate. DETAILED DESCRIPTION

[0019] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. Example

[0020] A variable back cavity sound liner sound absorption structure coupled with mechanical impedance, which introduces mechanical impedance by adding an "N" type thin plate to achieve low-frequency sound absorption and sound liner sound absorption frequency band regulation, fixes the thin plate between the perforated plate and the back plate of the back cavity, divides the back cavity into multiple areas, and adjusts its damping and elasticity by changing the thickness, shape and material of the thin plate for different sound absorption frequency bands. When the sound wave passes through the perforated plate, the air column in the neck of the small hole reciprocates like a piston under the action of the sound wave pressure, and has a certain air mass. The movement is continuous friction with the wall of the small hole, consuming part of the sound energy. The air in the cavity is elastic and can hinder the pressure change in the cavity caused by the movement of the hole neck column. The air column at the hole neck is regarded as mass and the air in the cavity is regarded as a spring, forming an elastic vibration system. When the frequency of the external sound wave is equal to its resonant frequency, it will cause the air column in the hole neck to resonate. At this time, the vibration displacement is the largest, the vibration speed is the largest, the friction loss of the hole wall is also the largest, and the sound energy dissipation is the strongest. At the same time, since the wall panels separating different back cavities are also elastic, the system, under the original resonance dissipation effect, couples the mechanical impedance of the thin plate. The sound waves entering different back cavities force the thin plates of the corresponding resonance frequencies to resonate, first converting the sound energy into elastic potential energy, which is then dissipated using the damping of the thin plate, thereby achieving regulation of the sound absorption performance in the target frequency band. Example

[0021] The sound absorbing structure of the sound liner of the present invention improves the low-frequency sound absorption performance of the sound liner by adding a thin plate structure, uses an "N"-shaped thin plate to construct a special-shaped back cavity area to match different target sound absorption frequency bands, and separates back cavities of different sizes through reasonable arrangement. Combined with the perforated plate, it can be regarded as a plurality of Helmholtz resonators in parallel. The difference is that the separated thin plates are elastic, and together with the elasticity of the air layer and the mass of the thin plates, a resonance system is formed, which has a greater sound absorption effect near the resonance frequency of the system, realizing the dissipation of sound energy. At the same time, the back cavity depth can be changed under the action of airflow, further broadening the sound absorption frequency band of the sound liner. Example

[0022] The present invention realizes the low-frequency sound absorption performance of the sound liner in a small spatial scale range by coupling the mechanical impedance of the thin plate. The traditional sound liner improves the low-frequency sound absorption performance by deepening the back cavity depth and increasing the perforation diameter, which is difficult to apply to mechanical equipment with compact space such as engines. The back cavity is separated by a thin plate with appropriate damping and elasticity, and the resonance of the thin plate can be used to dissipate the energy of the low-frequency sound wave, thereby broadening and improving the sound absorption performance of the low-frequency part. Example

[0023] According to the application scenarios and space limitations, based on the traditional multi-degree-of-freedom sound lining structure, that is, multiple layers of perforated plates are connected in series, and "N"-shaped thin plates are arranged between adjacent perforated plates, which are regarded as the impedances of multiple back cavities connected in parallel and then in series, so as to cope with the noise frequency bands of the engine under different working conditions and realize multi-modal sound absorption regulation. The elastically connected perforated plates adjust the back cavity depth during the up and down reciprocating motion of the "N"-shaped thin plates, broaden the sound absorption frequency band, and at the same time convert the vibration energy of the engine into elastic potential energy dissipation, effectively weakening the vibration noise during the operation of the engine.

[0024] In summary, the present invention provides a variable back cavity sound absorbing structure coupled with mechanical impedance. The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0025] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A variable back cavity sound absorbing structure coupled with mechanical impedance, characterized in that: It includes a back cavity fixing plate, an "N"-shaped thin plate and a perforated plate. The perforated plate is arranged on the surface of the front of the back cavity fixing plate that contacts the working environment, and the "N"-shaped thin plate is arranged between the top wall connecting the back cavity fixing plate and the perforated plate.

2. A variable back cavity sound absorbing structure with coupled mechanical impedance as claimed in claim 1, characterized in that: The "N"-shaped thin plates are arranged alternately between the perforated plates and the back cavity top plate.

3. A variable back cavity sound absorbing structure with coupled mechanical impedance as claimed in claim 1, characterized in that: The "N"-shaped thin plates construct multiple back cavities.

4. A variable back cavity sound absorbing structure with coupled mechanical impedance as claimed in claim 1, characterized in that: One end of the "N"-shaped thin plate is fixed to the back cavity fixing plate, and the other end of the "N"-shaped thin plate is connected to a perforated plate.

5. The variable back cavity sound absorbing structure with coupled mechanical impedance as claimed in claim 1, characterized in that: The distortion angle of the "N"-shaped thin plate is adjustable.

6. A variable back cavity sound absorbing structure with coupled mechanical impedance as claimed in claim 1, characterized in that: The "N"-shaped thin plate can be replaced with different physical properties and structures according to airflow conditions.

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