PET composite folded plate type periodic structure air inlet noise reduction pipeline

Abstract

The invention discloses a PET composite folded plate type periodic structure air inlet noise reduction pipeline which comprises a noise reduction pipeline body, noise reduction areas are circumferentially distributed on the noise reduction pipeline body, acoustic cavities protruding outwards are formed in the noise reduction areas, and each acoustic cavity is correspondingly provided with a folded plate type periodic acoustic crystal structure. The folded plate type periodic acoustic crystal structure comprises a plurality of acoustic cells which are sequentially arranged in the axial direction, each acoustic cell is composed of a scatterer and a base body, the scatterer is fixed to the front face of the base body, and the back face of the base body is fixedly connected with the acoustic cavity; and the base body in the axial direction is periodically folded. The problem that a traditional single-layer PET noise reduction pipeline is low in transmission loss at the low and medium frequency of 1000 Hz or below is solved, a folded plate type periodic acoustic crystal structure is additionally arranged on the basis of a traditional PET pipeline, the traditional pipeline and the acoustic crystal structure are fully combined, the traditional pipeline solves the high and medium frequency problem, the acoustic crystal solves the low frequency problem, and the noise reduction effect is good. Therefore, the full-band transmission loss is obviously improved.

Description

Technical Field

[0001] The invention relates to a noise reduction air intake pipeline in an automobile engine air intake system, in particular to an air intake noise reduction pipeline with a PET composite folded plate type periodic structure. Background Art

[0002] The engine is the main noise source of the car, which directly affects the comfort of the whole vehicle. Among them, the nozzle noise of the intake system is the most critical part of controlling engine noise. At present, the conventional intake noise reduction pipeline is PET noise reduction pipe, such as Figure 1 As shown, it is composed of an upper PET tube 1 and a lower PET tube 2. The PET molding process is hot molding. The upper PET tube 1 and the lower PET tube 2 are assembled by vibration friction welding. The transmission loss is shown in Figure 2 .

[0003] The utility model patent with publication number CN214221371U discloses a noise reduction pipeline for automobiles, which is a traditional PET noise reduction pipe, wherein the upper shell 30 of the noise reduction pipe and the lower shell 40 of the noise reduction pipe are made of ordinary single-layer PET material.

[0004] Traditional PET noise reduction pipes have the following disadvantages: PET raw materials are resistive materials, which are natural acoustic materials and follow the law of sound absorption quality, that is, the sound absorption coefficient gradually increases with the increase of thickness. Due to the limitations of engine compartment space and pipeline flow resistance, the thickness cannot be increased infinitely. This limits its noise reduction effect. Due to the limitations of the inherent characteristics of natural materials, the sound absorption coefficient of medium and low frequencies is low.

[0005] For noise in the 0-1000Hz frequency band, the current traditional solution has a sound transmission loss of about 10dB, which cannot meet the 0-1000Hz sound transmission loss of more than 25dB, and cannot meet the requirements of the vehicle's pipe outlet order noise. Adjusting the ratio and gram weight of traditional PET materials cannot meet the sound transmission requirements of the intake pipe at medium and low frequencies. In addition, adding silencers and other silencer components can increase the center frequency to more than 25dB, but the bandwidth does not cover 0-1000Hz, and due to the limitation of the engine compartment space, it is impossible to arrange more large-volume resonant cavities.

[0006] The invention application with publication number CN115972648A further studies and proposes a method for manufacturing a partially immersed waterproof PET noise reduction tube with an acoustic metamaterial structure. This solution has the following problems:

[0007] 1. The technical solution focuses on solving the problem of "low frequency band, especially 450Hz center frequency not meeting the standard".

[0008] 2. The array cells in this technical solution are acoustic crystals with a resonant cavity structure. The parameters that affect the key noise reduction frequency band are the diameter of the connecting tube of the cell resonant cavity, the volume of the cavity, and the number of cavities. The overall size of the acoustic cell is very small, only a few millimeters. During the molding process, if the process parameters including the pressure of the press during PET tube molding, the holding time, and the temperature of the mold are abnormal, it will directly affect the key size, thereby affecting the noise reduction frequency band designed in the early stage, that is, the noise reduction frequency band will be offset, affecting the NVH effect. This structure has high requirements for production processes and production equipment, and the production cost is high.

[0009] 3. This technical solution has high requirements on the strength of the mold. Due to the small size of the cavity, the size of the part corresponding to the cavity in the PET tube molding mold is small. The huge pressure during the molding process will cause damage to the cavity mold. Once the cavity is damaged, the number and size will change, which will directly lead to the offset of the noise reduction frequency band and affect the NVH performance. Therefore, the material of the cavity must use high-strength steel that needs to be quenched and fat-adjusted. There are also high requirements for the processing accuracy of the cavity, which leads to an increase in the cost of the mold.

[0010] In summary, under the premise of convenient production, how to improve the low-frequency sound transmission loss of the traditional PET noise reduction pipeline and increase the intake noise in the 0-1000Hz frequency band to more than 25dB at the center frequency is an urgent problem that technical personnel in this field need to solve. Summary of the invention

[0011] The purpose of the present invention is to provide a PET composite folded plate type periodic structure air intake noise reduction pipeline.

[0012] To achieve the above object, the present invention adopts the following technical solution:

[0013] A PET composite folded plate-type periodic structure air intake noise reduction pipeline, comprising a noise reduction pipeline body, wherein noise reduction areas are circumferentially distributed on the noise reduction pipeline body, and an acoustic cavity protruding outward is provided at the noise reduction area, and a folded plate-type periodic acoustic crystal structure is correspondingly provided at each acoustic cavity;

[0014] The folded plate-type periodic acoustic crystal structure includes a plurality of acoustic cells arranged in sequence along the axial direction. The acoustic cells are composed of a scatterer and a matrix. The scatterer is fixed on the front side of the matrix, and the back side of the matrix is ​​fixedly connected to the acoustic cavity. The matrix in the axial direction is periodically folded.

[0015] Furthermore, the scatterer includes a rigid block and a soft block, the rigid block is fixed on the front side of the soft block, and the back side of the soft block is fixedly connected to the substrate.

[0016] Furthermore, the rigid block and the soft block are in the shape of cylinders with equal diameters, and the base is in the shape of a rectangular plate.

[0017] Furthermore, the base is fixedly embedded in the frame, and the frame is fixedly connected to the bottom of the acoustic cavity;

[0018] Furthermore, a mounting plane is provided at the bottom of the acoustic cavity, and the frame and the base are fixed on the corresponding mounting plane.

[0019] Furthermore, more than two acoustic cavities and folded plate-type periodic acoustic crystal structures are distributed circumferentially in the noise reduction zone, and adjacent acoustic cavities are connected.

[0020] Furthermore, the noise reduction pipeline body is composed of an upper noise reduction pipe and a lower noise reduction pipe, and noise reduction areas are respectively provided at relative positions of the upper noise reduction pipe and the lower noise reduction pipe.

[0021] Furthermore, the upper noise reduction tube and the lower noise reduction tube are PET tubes; the rigid block is a lead block or a tin block; the soft block is a silicone rubber or nitrile rubber material; the matrix is ​​made of epoxy resin material; and the skeleton is made of plastic material.

[0022] Furthermore, the rigid block and the soft block are fused together through a vulcanization process to form a scatterer; the scatterer is embedded in the matrix through a secondary vulcanization process, the matrix is ​​embedded in the skeleton through an injection molding process, and the skeleton is welded to the upper noise reduction pipe / noise reduction pipe at the bottom of the acoustic cavity.

[0023] Furthermore, the parameters of the folded plate periodic acoustic crystal structure are selected according to the following method:

[0024] S1: Perform 3D modeling based on customer input boundaries, acoustic requirements, and minimum pipe cross-sectional area to derive the pipe shape and direction;

[0025] S2: Look up the table to obtain the parameters of the scatterer and base material, including:

[0026] λ is the elastic modulus, μ is the Poisson's ratio, and ρ is the mass density;

[0027] S3: According to the calculation method of the minimum cutoff frequency of the two-dimensional local resonance structure, determine the following parameters:

[0028] a is the height of the scatterer, b is the width of the scatterer, and c is the lattice constant, which represents the distance between two acoustic cells;

[0029] S4: According to the parameters obtained in S3, the entire integrated body is meshed using software, and finite element software is used to calculate the eigenfrequency model of the above-mentioned multi-bandgap. The calculation method is as follows

[0030] According to the formula

[0031] X-axis vector component:

[0032] The y-axis vector:

[0033] According to formula ①②, we can get the inverse lattice vector:

[0034] According to formula ③, we can obtain the second-order derivative G″④ and the first-order derivative G′⑤ of the reciprocal lattice vector.

[0035] By utilizing the periodicity of the structure, the elastic modulus λ, Poisson's ratio μ, and mass density ρ are expanded according to the Fourier series and combined with the Bloch theorem, the elastic wave equation is expanded in the form of plane wave superposition in the reciprocal lattice vector space, and then the wave equation is converted into the eigenvalue solution to obtain the elastic wave band structure of the integrated body; the specific equation is as follows, the Fourier expansion is substituted into the Bloch theorem and then into the XYZ direction eigenelastic wave equation, ④ and ⑤ are substituted into ⑥Z direction eigenequation ⑦X direction eigenequation and Y direction eigenequation ⑧,

[0036] Z direction

[0037]

[0038]

[0039]

[0040] Where: ω is the center frequency, k is the wave vector, and u is the displacement;

[0041] In the above equations ⑥⑦⑧, ω is the dependent variable, k is the independent variable, and u is the independent variable, forming a binary function; as the center frequency changes, the wave vector and displacement are constantly changing. When the wave vector is 0, that is, the acceleration is 0, a bandgap area will be generated, and the propagation of sound waves in this frequency band will be suppressed, thereby achieving the effect of low-frequency noise reduction;

[0042] S5: Output frequency, wave vector and transmission loss curve to see if the requirement of more than 25dB is met below 1000Hz. If so, end. If not, return to step S2 to adjust the parameters, that is, adjust the material parameters λ, μ, ρ of the scatterer and substrate, or fine-tune the dimensions of a, b, c, and then repeat step S4 for simulation until a bandgap appears below 1000Hz.

[0043] Beneficial effects of the present invention:

[0044] (1) Compared with the traditional PET noise reduction pipeline, the present invention improves the sound transmission loss at the center frequency of the intake noise in the frequency band of 0 to 1000 Hz from about 10 dB to more than 25 dB.

[0045] (2) The present invention solves the problem of low transmission loss in medium and low frequencies below 1000 Hz in traditional single-layer PET noise reduction pipelines. A folded plate periodic acoustic crystal structure is added to the traditional PET pipeline, which fully combines the traditional pipeline and the acoustic crystal structure. The traditional pipeline solves the medium and high frequency problems, and the acoustic crystal solves the low frequency problems, thereby significantly improving the transmission loss in the entire frequency band. In addition, compared with traditional resistive silencers, this invention has the advantages of lower cost and smaller space occupation.

[0046] (3) The acoustic cell of the present invention adopts a folded plate-type vibration structure. The noise reduction frequency band has basically no requirements on the molding parameters of the PET tube. As long as the basic requirements of the PET tube such as wall thickness and outline size are met, the fault tolerance rate is high. The folded plate structure adopts a vulcanization process, which is relatively simple. The cell size is large and the tolerance is large. The key parameter for the offset of the noise reduction frequency band is the material parameter rather than the structural size. The structural size plays a role of fine-tuning.

[0047] (4) The parameters for adjusting the noise reduction frequency band in the present invention are material parameters, which are relatively stable compared to structural parameters. The molding process is relatively simple, the process control points are small, and the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a schematic diagram of a conventional PET pipeline in the prior art;

[0049] Figure 2 This is the transmission loss test data diagram of the traditional PET pipeline;

[0050] Figure 3 It is a schematic diagram of the structure of the present invention;

[0051] Figure 4 is an exploded view of the present invention;

[0052] Figure 5 This is a front view of the upper noise reduction tube / lower noise reduction tube of the present invention;

[0053] Figure 6 yes Figure 5 AA section view;

[0054] Figure 7 It is a schematic diagram of the parameter calculation process of the folded plate periodic acoustic crystal structure;

[0055] Figure 8 This is a schematic diagram of COMSOL Multiphysics simulation results;

[0056] Fig. 9 It is a comparison chart of transmission loss test data between the scheme of the present invention and the traditional PET pipeline.

[0057] The drawings are only used for illustrative purposes and should not be construed as limitations on this patent. In order to better illustrate this embodiment, some parts of the drawings may be omitted, enlarged, or reduced, and do not represent the size of the actual product. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted. DETAILED DESCRIPTION

[0058] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0059] like Figures 3 to 6 As shown, this embodiment provides a PET composite folded plate periodic structure air intake noise reduction pipeline, including a noise reduction pipeline main body, the noise reduction pipeline main body is composed of an upper noise reduction pipe 1 and a lower noise reduction pipe 6, and the upper noise reduction pipe 1 and the noise reduction pipe 6 are PET tubes.

[0060] The upper noise reduction tube 1 and the lower noise reduction tube 6 are provided with noise reduction areas at their relative positions, and an acoustic cavity protruding outward is provided at the noise reduction area, and a folded plate-type periodic acoustic crystal structure is provided at each acoustic cavity. The folded plate-type periodic acoustic crystal structure includes a plurality of acoustic cells arranged in sequence along the axial direction, and the acoustic cell is composed of a scatterer and a matrix 3, the scatterer is fixed on the front side of the matrix 3, and the back side of the matrix 3 is fixedly connected to the acoustic cavity; the matrix 3 in the axial direction is periodically folded.

[0061] In this embodiment, two acoustic cavities and a folded plate-type periodic acoustic crystal structure are distributed along the circumferential direction in each of the upper and lower noise reduction zones, and adjacent acoustic cavities are connected.

[0062] The scatterer includes a rigid block 5 and a soft block 4. The rigid block 5 is fixed to the front of the soft block 4, and the back of the soft block 4 is fixedly connected to the substrate 3. In this embodiment, the rigid block 5 and the soft block 4 are cylindrical in shape with equal diameters, and the substrate 3 is a rectangular plate.

[0063] In order to weld the folded plate type periodic acoustic crystal structure to the PET tube shell, a frame 2 is also provided. The matrix 3 is fixedly embedded in the frame 2, and the frame 2 is fixedly connected to the bottom of the acoustic cavity. The bottom of the acoustic cavity is provided with a matching mounting plane, and the frame 2 and the matrix 3 are fixed on the corresponding mounting plane.

[0064] In this embodiment, the rigid block 5 is a metal block such as a lead block or a tin block; the soft block 4 can be made of silicone rubber or nitrile rubber; the base 3 is made of epoxy resin; the skeleton 2 can be made of plastic materials such as PP, PA6, PA66, etc.

[0065] The molding process of the PET composite folded plate periodic structure intake noise reduction pipeline of this embodiment is as follows: the rigid block 5 and the soft block 4 are fused into one through a vulcanization process to form a scatterer, and then the scatterer is embedded into the matrix 3 through a secondary vulcanization process, thus forming a folded plate periodic acoustic crystal structure, which is then embedded into the plastic skeleton 2 through an injection molding process, and then welded to the PET tube shell, and then the upper noise reduction pipe 1 and the lower noise reduction pipe 6 are welded into one through vibration friction.

[0066] In this embodiment, Figure 7 As shown, the parameter selection of the folded plate periodic acoustic crystal structure is carried out in the following way:

[0067] S1: According to CFD fluid analysis, the pipe cross-sectional area is less than 3800mm 2 Otherwise, the air intake resistance will be too large, affecting the engine power. The pipeline needs to maintain a safe distance of more than 10mm from the surrounding components. UG 8.0 is used to perform three-dimensional modeling based on the above constraint points to obtain the shape and direction of the pipeline.

[0068] S2: Look up the table to obtain the parameters of the scatterer and the base material (the rigid block 5 is made of lead, the soft block 4 is made of silicone rubber, and the base 3 is made of epoxy resin material); including:

[0069] λ is the elastic modulus, μ is the Poisson's ratio, and ρ is the mass density;

[0070] Table 1 Material parameters

[0071] Material parameters <![CDATA[Mass density / (kg / m 3 )]]> <![CDATA[Elastic modulus / 10 10 GPa]]> Poisson's ratio Lead weight 11600 4.08 0.369 Rubber layer 1300 <![CDATA[1.17x10 -5 ]]> 0.468 Epoxy resin layer 1180 0.435 0.371

[0072] S3: According to the vulcanization process (the material shape should be as regular as possible, such as a cuboid) and the welding process (the combination of the integrated body and the pipeline, try to choose a flat surface with a welding plane of 0°), choose the flat surface of the pipeline to weld the integrated body, such as 3 to Figure 6 As shown, the middle position of the pipeline is selected for welding the integrated body. According to the theory of acoustic metamaterials, the more acoustic cells there are, the more elastic wave bandgap areas there are, the wider the transmission loss band is, and the greater the transmission loss amplitude is. However, due to space limitations, the upper noise reduction tube 1 / noise reduction tube 6 is defined as 16 acoustic cells each. According to the minimum calculation method of the cutoff frequency of the two-dimensional local resonance structure, the following parameters are determined:

[0073] a is the height of the scatterer, b is the width of the scatterer, and c is the lattice constant, which represents the distance between two acoustic cells;

[0074] Table 2 Structural parameters

[0075] a / mm b / mm c / mm 10 15 25

[0076] S4: Based on the parameters obtained in S3, the entire integrated body is meshed using the Hyper mesh software, and the finite element software COMSOL Multiphysics is used to calculate the eigenfrequency model of the above-mentioned multi-bandgap. The calculation method is as follows:

[0077] According to the formula

[0078] X-axis vector component:

[0079] The y-axis vector:

[0080] According to formula ①②, we can get the inverse lattice vector:

[0081] According to formula ③, we can obtain the second-order derivative G″④ and the first-order derivative G′⑤ of the reciprocal lattice vector.

[0082] By utilizing the periodicity of the structure, the elastic modulus λ, Poisson's ratio μ, and mass density ρ are expanded according to the Fourier series and combined with the Bloch theorem, the elastic wave equation is expanded in the form of plane wave superposition in the reciprocal lattice vector space, and then the wave equation is converted into the eigenvalue solution to obtain the elastic wave band structure of the integrated body; the specific equation is as follows, the Fourier expansion is substituted into the Bloch theorem and then into the XYZ direction eigenelastic wave equation, ④ and ⑤ are substituted into ⑥Z direction eigenequation ⑦X direction eigenequation and Y direction eigenequation ⑧,

[0083] Z direction

[0084]

[0085]

[0086]

[0087] Where: ω is the center frequency, k is the wave vector, and u is the displacement;

[0088] The X-axis, Y-axis, and Z-axis represent the displacement of the spatial scatterer caused by vibration due to the influence of elastic waves (sound waves), which is decomposed into displacements in three directions.

[0089] In the above equations ⑥⑦⑧, ω is the dependent variable, k is the independent variable, and u is the independent variable, forming a binary function; as the center frequency changes, the wave vector and displacement are constantly changing. When the wave vector is 0, that is, the acceleration is 0, a bandgap area will be generated, and the propagation of sound waves in this frequency band will be suppressed, thereby achieving the effect of low-frequency noise reduction;

[0090] S5: Output frequency, wave vector and transmission loss curve, according to COMSOL Multiphysics simulation results as shown below Figure 8 As shown: the horizontal axis is the wave vector and the vertical axis is the frequency.

[0091] It can be seen from the figure that there are multiple forbidden bands below 1000Hz, and the propagation of sound waves in this frequency band is suppressed, and the corresponding transmission loss reaches the maximum, which is as expected. If there is no forbidden band below 1000Hz, or the transmission loss amplitude is small, return to step S2, adjust the material parameters λ, μ, ρ of the scatterer and the substrate by looking up the table, or fine-tune the dimensions of a, b, and c, and repeat step S4 for simulation until a forbidden band appears below 1000Hz.

[0092] The sound transmission loss of the PET composite folded plate periodic structure air intake noise reduction pipeline in this embodiment is tested as follows: Fig. 9 As shown, the low-frequency transmission loss is significantly improved compared with that shown, which met expectations.

[0093] Compared with the traditional PET noise reduction pipeline, the transmission loss of the center frequency of the intake noise in the frequency band of 0-1000Hz is increased from about 10dB to more than 25dB. The pipeline of the present invention has the noise reduction characteristics of the impedance composite silencer and is more targeted. The transmission loss of the pipeline in the full frequency band is greatly improved compared with the traditional PET pipeline.

[0094] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention is described in detail with reference to the above embodiments, those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

[0095] If the words "first", "second", etc. are used in this document to limit components, those skilled in the art should know that the use of "first" and "second" is only to facilitate the description of the present invention and simplify the description. Unless otherwise stated, the above words have no special meaning.

[0096] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0097] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

Claims

1. A PET composite folded plate type periodic structure air intake noise reduction pipeline, comprising a noise reduction pipeline body, characterized in that: The main body of the noise reduction pipeline is provided with a noise reduction area distributed on the circumference, and an acoustic cavity protruding outward is provided in the noise reduction area, and a folded plate-type periodic acoustic crystal structure is correspondingly provided in each acoustic cavity; The folded plate-type periodic acoustic crystal structure includes a plurality of acoustic cells arranged in sequence along the axial direction. The acoustic cells are composed of a scatterer and a matrix. The scatterer is fixed on the front side of the matrix, and the back side of the matrix is ​​fixedly connected to the acoustic cavity. The matrix in the axial direction is periodically folded.

2. The PET composite folded plate periodic structure air intake noise reduction pipeline according to claim 1 is characterized in that: The scatterer comprises a rigid block and a soft block, wherein the rigid block is fixed on the front side of the soft block, and the back side of the soft block is fixedly connected to the base body.

3. The PET composite folded plate periodic structure air intake noise reduction pipeline according to claim 2 is characterized in that: The rigid block and the soft block are in the shape of cylinders with equal diameters, and the base is in the shape of a rectangular plate.

4. The PET composite folded plate type periodic structure air intake noise reduction pipeline according to claim 3 is characterized by: The base is fixedly embedded in the frame, and the frame is fixedly connected to the bottom of the acoustic cavity.

5. The PET composite folded plate type periodic structure air intake noise reduction pipeline according to claim 4 is characterized in that: The bottom of the acoustic cavity is provided with a matching mounting plane, and the frame and the base are fixed on the corresponding mounting plane.

6. The PET composite folded plate type periodic structure air intake noise reduction pipeline according to claim 4 or 5, characterized in that: More than two acoustic cavities and folded plate-type periodic acoustic crystal structures are distributed in the noise reduction area along the circumferential direction, and adjacent acoustic cavities are connected.

7. The PET composite folded plate periodic structure air intake noise reduction pipeline according to claim 6, characterized in that: The noise reduction pipeline body is composed of an upper noise reduction pipe and a lower noise reduction pipe, and noise reduction areas are respectively arranged at relative positions of the upper noise reduction pipe and the lower noise reduction pipe.

8. The PET composite folded plate periodic structure air intake noise reduction pipeline according to claim 7, characterized in that: The upper noise reduction tube and the lower noise reduction tube are PET tubes; the rigid block is a lead block or a tin block; the soft block is a silicone rubber or nitrile rubber material; the matrix is ​​made of epoxy resin material; and the frame is made of plastic material.

9. The PET composite folded plate type periodic structure air intake noise reduction pipeline according to claim 8, characterized in that: The rigid block and the soft block are integrated into one by a vulcanization process to form a scatterer; the scatterer is embedded in the matrix by a secondary vulcanization process, the matrix is ​​embedded in the skeleton by an injection molding process, and the skeleton is welded to the upper noise reduction pipe / noise reduction pipe at the bottom of the acoustic cavity.

10. The PET composite folded plate type periodic structure air intake noise reduction pipeline according to any one of claims 2 to 9, characterized in that: The parameter selection of the folded plate type periodic acoustic crystal structure is carried out according to the following method: S1: Perform 3D modeling based on customer input boundaries, acoustic requirements, and minimum cross-sectional area of ​​the pipeline to derive the pipeline shape and direction; S2: Look up the table to obtain the parameters of the scatterer and base material, including: λ is the elastic modulus, μ is the Poisson's ratio, and ρ is the mass density; S3: According to the calculation method of the minimum cutoff frequency of the two-dimensional local resonance structure, determine the following parameters: a is the height of the scatterer, b is the width of the scatterer, and c is the lattice constant, which represents the distance between two acoustic cells; S4: According to the parameters obtained in S3, the entire integrated body is meshed using software, and finite element software is used to calculate the eigenfrequency model of the above-mentioned multi-bandgap. The calculation method is as follows According to the formula X-axis vector component: The y-axis vector: According to formula ①②, we can get the inverse lattice vector: According to formula ③, we can obtain the second-order derivative G″④ and the first-order derivative G′⑤ of the reciprocal lattice vector. By utilizing the periodicity of the structure, the elastic modulus λ, Poisson's ratio μ, and mass density ρ are expanded according to the Fourier series and combined with the Bloch theorem, the elastic wave equation is expanded in the form of plane wave superposition in the reciprocal lattice vector space, and then the wave equation is converted into the eigenvalue solution to obtain the elastic wave band structure of the integrated body; the specific equation is as follows, the Fourier expansion is substituted into the Bloch theorem and then into the XYZ direction eigenelastic wave equation, ④ and ⑤ are substituted into ⑥Z direction eigenequation ⑦X direction eigenequation and Y direction eigenequation ⑧, Z direction Where: ω is the center frequency, k is the wave vector, and u is the displacement; In the above equations ⑥⑦⑧, ω is the dependent variable, k is the independent variable, and u is the independent variable, forming a binary function; as the center frequency changes, the wave vector and displacement are constantly changing. When the wave vector is 0, that is, the acceleration is 0, a bandgap area will be generated, and the propagation of sound waves in this frequency band will be suppressed, thereby achieving the effect of low-frequency noise reduction; S5: Output frequency, wave vector and transmission loss curve to see if the requirement of more than 25dB is met below 1000Hz. If so, end. If not, return to step S2 to adjust the parameters, that is, adjust the material parameters λ, μ, ρ of the scatterer and substrate, or fine-tune the dimensions of a, b, c, and then repeat step S4 for simulation until a bandgap appears below 1000Hz.

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