Ventilation, noise reduction and dust removal composite structure of pipeline

Abstract

The application discloses a pipeline composite structure for ventilation, noise reduction and dust removal, which comprises a plurality of composite structure units arranged obliquely along the inner cavity of the pipeline, and the composite structure units are arranged in an array in a periodic manner; the composite structure unit is a shell structure with a parallelogram cross section and a cavity in the interior, a plurality of cylindrical through holes are formed in one side of the shell of the composite structure unit in a periodic arrangement, activated carbon backings are arranged in the shell of the unit opposite to the through holes, and the shell of the unit is arranged at equal intervals by air flow areas. The structure can block the sound energy carried by the incident sound wave by the composite structure, generate high transmission loss, and achieve the noise reduction effect; the air flow areas are arranged between the units of the composite structure, the problem that the traditional sound insulation structure cannot be ventilated is solved, the activated carbon backings have the dust removal effect, and the structure has wide application prospects in the design of ventilation windows, exhaust pipelines and ventilation sound barriers.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of vibration and noise reduction, and particularly relates to a pipeline composite structure for ventilation, noise reduction and dust removal. BACKGROUND

[0002] In today's society with continuous economic development, ventilation equipment such as air conditioners and exhaust fans can be seen everywhere in living and office areas, and large mechanical equipment such as engines, cranes and air blowers is also increasing in industrial production. The environmental noise generated by the above equipment not only harms human hearing and psychology, but also causes acoustic fatigue of key components, endangers safety, and shortens service life. An important source of environmental noise is pipeline noise. Pipeline noise in industrial noise mainly comes from the intake and exhaust noise of compressors and air blowers, pipeline noise in building noise mainly comes from heating, ventilation and air conditioning pipeline noise, and pipeline noise in traffic noise mainly comes from the engine and exhaust pipe noise of tools such as cars and airplanes. Insulating or attenuating the propagation of noise in the pipeline is an important measure for noise reduction, and installing pipeline silencing equipment is the most commonly used method to block the propagation of noise in the pipeline.

[0003] Traditional pipeline silencing technology includes reactive silencers and resistive silencers. In actual application scenarios, reactive silencers are composed of reactive silencing elements, including expansion chambers, Helmholtz resonators, and Herstel-Kunkle tubes. Although reactive silencers have complex structures, they can all be decomposed into combinations of the above reactive silencing elements. The silencing principle of the expansion chamber is to introduce impedance mismatch by using the cross-section mutation at the inlet and outlet of the pipeline, thereby making the sound propagate. The principle of the Helmholtz resonator is to have a high silencing amount at the resonance frequency, which can specifically eliminate noise in a specific frequency band. The principle of the Herstel-Kunkle tube is to connect a bypass tube in parallel with the main pipeline, and the length of the bypass tube and the length of the main pipeline connected in parallel are different, thereby forming sound wave cancellation interference.

[0004] Resistive silencers are silencers that use sound waves to propagate in porous sound-absorbing materials or sound-absorbing structures, convert sound energy into heat energy due to friction, and dissipate it, so that the noise propagating along the pipeline attenuates with distance, thereby achieving the purpose of silencing. Resistive silencers are effective for eliminating high and medium frequency noise, but not very effective for eliminating low frequency noise. The silencing amount is related to the structure of the silencer, the shape and area of the air passage cross section, the air flow velocity, the length of the silencer, and the type, density and thickness of the sound-absorbing material.

[0005] The main function of the pipeline is ventilation and heat dissipation, and some pipelines contain dust, insects and other impurities. It is of utmost importance to meet the basic requirements of the pipeline while considering the functions of noise reduction and dust removal.

[0006] Therefore, designing a duct silencer for ventilation, noise reduction, and dust removal that simultaneously fulfills the three functions of ventilation, noise reduction, and dust removal, thereby improving duct noise and enhancing people's quality of life, has become an urgent technical problem to be solved in this field. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a composite duct structure for ventilation, noise reduction, and dust removal. This structure comprises several hollow shell units with parallelogram cross-sections arranged periodically within the duct, with hollow areas between the units. This design achieves excellent noise reduction against broadband duct noise while minimizing sound transmission loss. Airflow areas between the units in the composite structure facilitate ventilation, while activated carbon backing within the hollow shells enables dust removal.

[0008] The present invention is achieved through the following technical solution.

[0009] According to one aspect of the present invention, a duct composite structure for ventilation, noise reduction and dust removal is provided, comprising a plurality of composite structural units arranged obliquely along the axial direction of the duct cavity, the composite structural units being arranged in an array according to a periodic arrangement;

[0010] The composite structural unit is a shell structure with a parallelogram cross-section and an internal cavity. Several cylindrical through holes are opened on one side of the composite structural unit shell in a periodic arrangement. An activated carbon backing is applied inside the unit shell on the side opposite to the through holes. The unit shells are arranged at equal intervals with air flow areas.

[0011] Preferably, the longitudinal section of the composite structural unit is arranged at an angle of 45 to 55° along the horizontal plane of the pipe cavity.

[0012] Preferably, the composite structural units arranged in a periodic manner serve as the noise inlet and outlet in the pipe cavity along the direction of the airflow area.

[0013] Preferably, the adjacent composite structural units arranged in a periodic manner are spaced at equal intervals, and the spacing between them is the same as the wall thickness of the composite structural unit.

[0014] Preferably, the cylindrical through holes are arranged periodically at a ratio of (2-3)×17 on one side of the composite structure unit shell.

[0015] Preferably, the cylindrical through hole is arranged obliquely along the side wall of the composite structure unit shell, and the axis of the cylindrical through hole is at an angle of 80 to 90 degrees to the plane of the composite structure unit shell.

[0016] Preferably, the composite structural unit is made of aluminum alloy plate or acrylic plate.

[0017] Preferably, the two sides of the composite structure unit shell are welded to the pipe wall.

[0018] Preferably, the composite structural unit shell and the activated carbon backing are bonded together with adhesive.

[0019] The present invention, by adopting the above technical solution, has the following beneficial effects:

[0020] 1. The composite structural unit of the present invention has an internal cavity with a parallelogram cross section. Several cylindrical through holes arranged periodically are arranged on the left side of the unit shell. Activated carbon backing is laid in the cavity. The composite structural unit can produce a resistive noise reduction effect, which can block the transmission of incident noise in the pipe and form a large sound transmission loss.

[0021] 2. The space between the composite structural units in this invention can be used for air circulation in the pipe to form ventilation and heat dissipation conditions. The shell material of the composite unit is aluminum alloy, which also has good thermal conductivity, and can further provide heat dissipation function in addition to noise reduction function.

[0022] 3. Activated carbon is applied as a backing material to the inner surface of the cavity shell of the unit where the through holes are opened. It can adsorb harmful particles in the pipes and achieve a dust removal effect. Attached Figure Description

[0023] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, do not constitute an undue limitation of the invention. In the drawings:

[0024] Figure 1 This is a three-dimensional structural diagram of a ventilation, noise reduction, and dust removal pipeline composite structure installed in a pipeline according to the present invention.

[0025] Figure 2 This is a schematic diagram of the xz section of a duct composite structure for ventilation, noise reduction, and dust removal installed in a duct according to the present invention.

[0026] Figure 3 This invention relates to a composite pipe structure for ventilation, noise reduction, and dust removal.

[0027] Figure 4 This is a schematic diagram of the xz section of a duct composite structure unit for ventilation, noise reduction, and dust removal according to the present invention.

[0028] Figure 5 This is a schematic diagram of the yz section of a duct composite structure unit for ventilation, noise reduction, and dust removal according to the present invention.

[0029] Figure 6 This is a finite element calculation mesh diagram of a duct composite structure for ventilation, noise reduction, and dust removal according to the present invention.

[0030] Figure 7The sound transmission loss in the frequency range of 10-1429Hz is described in Embodiment 1 of a duct composite structure for ventilation, noise reduction, and dust removal according to the present invention.

[0031] Figure 8 The continuous power spectral density of a duct composite structure for ventilation, noise reduction, and dust removal according to the present invention is shown in the frequency range of 10 to 1429 Hz.

[0032] Figure 9 Example 2 of the duct composite structure for ventilation, noise reduction and dust removal of the present invention shows the sound transmission loss at a frequency of 10 to 1000 Hz;

[0033] Figure 10 Example 2 of the duct composite structure for ventilation, noise reduction and dust removal of the present invention is the continuous power spectral density at a frequency of 10 to 1000 Hz.

[0034] Figure 11 Example 3 of the duct composite structure for ventilation, noise reduction and dust removal of the present invention shows the sound transmission loss at a frequency of 10-850Hz.

[0035] Figure 12 Example 3 of the duct composite structure for ventilation, noise reduction and dust removal of the present invention is the continuous power spectral density at a frequency of 10 to 850 Hz;

[0036] Figure 13 The sound pressure modal cloud diagram at 600Hz is shown for Embodiment 1 of the duct composite structure for ventilation, noise reduction and dust removal of the present invention.

[0037] Figure 14 The sound pressure modal cloud diagram at 1200Hz is shown for Embodiment 1 of the duct composite structure for ventilation, noise reduction and dust removal of the present invention.

[0038] Figure 15 The sound pressure modal cloud diagram at 600Hz is shown for Embodiment 2 of the duct composite structure for ventilation, noise reduction and dust removal of the present invention.

[0039] Figure 16 The sound pressure modal cloud diagram at 300Hz is shown for Embodiment 2 of the duct composite structure for ventilation, noise reduction and dust removal of the present invention.

[0040] Figure 17 The sound pressure modal cloud diagram at 600Hz is shown for Embodiment 3 of the duct composite structure for ventilation, noise reduction and dust removal of the present invention.

[0041] Figure 18 The sound pressure modal cloud map at 1200Hz is shown for embodiment 3 of the ventilation, noise reduction and dust removal pipeline composite structure of the present invention.

[0042] The labels in the attached diagram are as follows: 1-Composite structural unit; 1-1-Upper structure of unit; 1-2-Left structure of unit; 1-3-Right structure of unit; 1-4-Lower structure of unit; 2-1-Upper cylindrical through hole; 2-2-Lower cylindrical through hole; 2-Cylindrical through hole; 3-Activated carbon backing; 4-Internal cavity; 5-1~5-5-Upper ventilation opening of composite structure; 6-1~6-5-Lower ventilation opening of composite structure; 7-Pipe. Detailed Implementation

[0043] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0044] like Figure 1 , Figure 2 As shown, the ventilation, noise reduction, and dust removal duct composite structure of the present invention is installed inside the duct, as... Figure 2 As shown, the ventilation, noise reduction, and dust removal duct composite structure unit of the present invention includes: a composite structure unit 1, cylindrical through holes 2, activated carbon backing 3, an internal cavity 4, upper vents 5-1 to 5-5 on the composite structure, and lower vents 6-1 to 6-5 on the composite structure. Several composite structure units 1 are arranged obliquely along the axial direction of the inner cavity of the duct 7, forming an array in a horizontally periodic pattern. Each composite structure unit is a shell structure with an internal cavity 4 and a parallelogram cross-section. Several periodically arranged cylindrical through holes 2 are opened on one side of the shell of the composite structure unit. Activated carbon backing 3 is laid inside the internal cavity 4 and the shell of the unit opposite to the opening side. The shells of the composite structure units 1 are arranged equidistantly in airflow areas.

[0045] The composite structural units, arranged periodically, serve as both noise inlet and outlet within the duct cavity, with the airflow direction acting as both the noise inlet and outlet. Sound incident direction is perpendicular to the arrangement of the silencing units within the duct cavity, and is transmitted through the airflow area of ​​the ventilation, noise reduction, and dust removal composite structure to the bottom surface of the porous composite structure. Cylindrical through-holes are located on the sides of the units, allowing sound waves to propagate through these holes into the internal cavity of the structural unit shell, where resonance reduces duct noise. The composite structure effectively creates a variable cross-section for the duct, causing impedance mismatch during sound wave transmission, increasing sound wave reflection and interference, and blocking sound energy transfer.

[0046] In this embodiment, the composite structural unit is welded to the pipeline on both sides.

[0047] In this invention, the pipe dimensions are 120mm×120mm to 200mm×200mm, and the pipe wall thickness is 0.5mm. The composite structure unit for ventilation, noise reduction, and dust removal consists of five identical units. The ventilation width of the upper ventilation openings 5-1 to 5-4 and the lower ventilation openings 6-1 to 6-5 of the composite structure is 4mm, and the maximum ventilation width of the upper ventilation opening 5-5 is 24mm. The overall composite structure has a height of 30mm and a width of 120mm.

[0048] like Figure 3 In the illustrated embodiment, the ventilation, noise reduction, and dust removal duct composite structure unit has two rows of periodically arranged cylindrical through holes 2 on one side. The cylindrical through holes 2 are arranged periodically in a 2×17 pattern. The interior is an internal cavity 4 formed by stretching a parallelogram cross-section. Activated carbon backing 3 is applied to the side of the internal cavity 4 opposite to the side with the cylindrical through holes 2. The unit shells are arranged at equal intervals in airflow areas. The spacing between adjacent composite structure units is equal, and the spacing is the same as the side wall thickness of the composite structure unit.

[0049] like Figure 4 As shown, the cylindrical through-hole 2 of the ventilation, noise reduction, and dust removal duct composite structure unit of the present invention is arranged obliquely along the noise inlet direction of the side wall of the composite structure unit, and the axis of the cylindrical through-hole is at an angle of 80-90° with the plane of the composite structure unit shell. This allows more sound waves to enter the cavity.

[0050] like Figure 4 , Figure 5 As shown, in this embodiment, the thickness of the upper structure 1-1 of the unit is 2mm, the thickness of the lower structure 1-4 of the unit is 2mm, the horizontal width of the left structure 1-2 of the unit is 4mm, and the horizontal width of the right structure 1-3 of the unit is 4mm. The longitudinal section of the composite structure unit is arranged at an angle of 45-55° along the horizontal plane of the inner cavity of the pipe, preferably 53.756° in this embodiment. The width of the lower bottom surface 1-4 of the composite structure unit shell is 16mm, the horizontal width of the internal cavity 4 of the shell is 6mm and the height is 26mm, the horizontal width of the activated carbon backing 3 is 2mm and the height is 26mm, and the radius of the upper cylindrical through hole 2-1 and the lower cylindrical through hole 2-2 is 2.2mm.

[0051] The vertical distance from the intersection of the central axis of the upper cylindrical through hole 2-1 and the left side of the internal cavity 4 to the bottom of the lower structure 1-4 of the shell is 22mm. The vertical distance from the intersection of the central axis of the cylindrical through hole 2-2 and the left side of the cavity 4 to the bottom of the lower structure 1-4 of the shell is 13.3mm. The horizontal width of the airflow area between the composite structural units is 4mm.

[0052] In this embodiment, the shell material of the ventilation, noise reduction, and dust removal duct composite structure unit is made of aluminum alloy plate or acrylic plate. The aluminum alloy plate used is model 3003H18 with a density of 2730 kg / m³. 3 The Young's modulus is 69 GPa and the Poisson's ratio is 0.33.

[0053] In this embodiment, the material inside the cavity is air with a density of 1.29 kg / m³. 3 The speed of sound is 343 m / s.

[0054] The composite structure unit shell is connected to the activated carbon backing by adhesive bonding.

[0055] In this embodiment, the geometric dimensions of the impedance gradient unit and the cavity unit can be specifically designed according to the required noise reduction frequency.

[0056] The working principle of this invention is as follows: Below the pipe cutoff frequency, sound waves are transmitted in the form of plane waves. When the sound waves are incident on the composite structure for ventilation, noise reduction, and dust removal, the cross-section of the sound wave transmission changes. Simultaneously, influenced by the structural impedance and the effect of the tilted ventilation, noise reduction, and dust removal unit, impedance mismatch occurs when the sound waves reach the composite structure, resulting in reflection and interference. This reduces the sound energy radiated outward from the silencer. Furthermore, the tilted unit structure is an aluminum alloy or acrylic cavity with cylindrical through holes, a special Helmholtz resonant cavity that provides a sound absorption effect. The activated carbon backing design helps to adsorb dust.

[0057] When sound waves from inside the pipe are incident on the surface of the composite structure unit shell for ventilation, noise reduction, and dust removal, the incident sound wave impedance is mismatched with the characteristic impedance of the composite structure due to the surface impedance of the tilted unit. This causes the sound propagation mode to change to a mixture of incident, reflection, scattering, interference, and other propagation modes, thereby reducing the sound energy radiated from the pipe to the outside. Furthermore, the interior of the tilted unit structure is a cavity with cylindrical holes. The physical essence of the sound attenuation effect of this cavity is the Helmholtz resonance effect. Influenced by factors such as the arrangement of the through holes, the shape of the cavity, and the structural materials, this cavity has a broadband sound attenuation effect.

[0058] Considering the problem that traditional sound insulation structures cannot be used under conditions that ensure air circulation, the composite structural unit shells are arranged at equal intervals in the air circulation area. This can produce a broadband sound attenuation effect in the pipe, ensuring the allowable air circulation area, thereby playing an auxiliary role in heat dissipation in the pipe and preventing adverse effects such as thermal fatigue of the pipe shell and mechanical connection parts and accelerated aging of testing instruments in the pipe.

[0059] Using activated carbon as a backing in a hollow structure allows for dust adsorption. When air containing fine particulate matter serves as the sound wave propagation medium, the incident sound waves enter the internal cavity of the composite structure unit through the cylindrical holes on the unit shell surface. Due to the well-developed pore structure of activated carbon, the numerous molecules on the pore walls generate strong intermolecular forces, thereby attracting the fine particulate matter in the air into the pores. In addition to carbon, activated carbon contains functional groups of oxygen and hydrogen on its surface, such as carboxyl, hydroxyl, phenols, lactones, quinones, and ethers. Therefore, the oxides and complexes on the surface of activated carbon can chemically react with the adsorbed fine particulate matter, further purifying the air.

[0060] The following simulation model is established using the acoustic-structure interaction module in Comsol Mutiphysics 6.2 finite element simulation software to calculate the continuous power spectral density and sound transmission loss of the duct composite structure for ventilation, noise reduction, and dust removal.

[0061] like Figure 6 The figure shows the finite element simulation mesh generation diagram of the duct composite structure for ventilation, noise reduction, and dust removal. In the finite element simulation settings, the incident sound pressure amplitude is 1 Pa, and the sound wave is a plane wave incident perpendicularly along the duct. The incident surface is the top of the composite structure, and the sound wave transmission surface is the bottom of the composite structure. Here, the incident port and the exit port are defined as ports. The sound power at the incident port is obtained from the finite element simulation results as W. in The acoustic power at the output port is W. out Here, the transfer function method is used to theoretically analyze sound wave transmission, and the transmission loss TL is used to evaluate the acoustic performance of the muffler.

[0062] The propagation loss TL is

[0063]

[0064] The unit of transport loss TL is dB.

[0065] Power spectral density (PSD) is

[0066]

[0067] In the formula, ω = 2πf, T = N / f s Representing the entire measurement period, the discrete-time variable in the COMSOL simulation is u. ω (n), the unit of PSD is W / Hz.

[0068] According to duct acoustics theory, for a square ventilation duct, the cutoff frequency f0 of the duct acoustic mode is...

[0069]

[0070] Where c0 is the air speed of sound, and l is the width of the longer side of the square pipe cross-section. This invention uses plane waves for simulation calculations and only considers the transmission loss of the duct composite structure for ventilation, noise reduction, and dust removal within the cutoff frequency range.

[0071] The following are different embodiments of 120mm×120mm ventilation ducts and 160mm×160mm ventilation ducts.

[0072] Example 1

[0073] Five composite unit structures for ventilation, noise reduction and dust removal are installed in a 120mm×120mm ventilation duct. Each unit shell has 2×17 cylindrical through holes on its side. The horizontal distance between each unit is 4mm. The length of the composite structure is 120mm.

[0074] like Figure 7 As shown, in Example 1, the pipe size is 120mm×120mm and the cutoff frequency is 1429Hz. The average transmission loss of the ventilation, noise reduction and dust removal pipe composite structure is 19.8dB in the frequency range of 10 to 1429Hz, and the transmission loss is greater than 10dB in the frequency range of 85 to 1429Hz. The transmission loss is 29.1dB at 1429Hz.

[0075] like Figure 8 As shown, in Example 1, the average continuous power spectral density from 10 to 1429 Hz is 3 W / Hz, and the power spectral density at 1420 Hz is 5.35 W / Hz.

[0076] like Figure 13 , Figure 14 The figures show the sound pressure modal cloud diagrams of the pipeline composite structure in Example 1 at 600Hz and 1200Hz. As can be seen from the figures, the sound wave is transmitted in the form of a plane wave inside the pipeline. When the sound wave passes through the ventilation, noise reduction and dust removal pipeline composite structure, the sound wave is reflected and interfered with. The sound energy is blocked by the composite structure and cannot be transmitted to the noise outlet, thus significantly reducing the sound pressure and attenuating the sound energy transmitted to the noise outlet, thereby achieving a noise reduction effect while meeting the ventilation requirements.

[0077] Example 2

[0078] In a 160mm×160mm ventilation duct, seven ventilation, noise reduction and dust removal unit structures are installed. Each unit shell has 2×17 cylindrical through holes on its side. The horizontal distance between each unit is 4mm, and the composite structure is 160mm long.

[0079] like Figure 9As shown, in Example 2, the cutoff frequency is 1071.875Hz. The average sound transmission loss of the ventilation, noise reduction and dust removal duct composite structure is 17.6dB in the frequency range of 10 to 1000Hz, and the sound transmission loss is greater than 10dB in the frequency range of 85 to 1000Hz. The sound transmission loss is 24.76dB at 1000Hz.

[0080] Figure 10 As shown, in Example 2, the average value of the continuous power spectral density from 10 to 1000 Hz is 2.2 W / Hz, and the power spectral density at 1000 Hz is 4.15 W / Hz. The overall continuous power spectral density is slightly smaller than that in Example 1.

[0081] like Figure 15 , Figure 16 The figures show the sound pressure modal cloud diagrams at 600Hz and 300Hz for Example 2 of the pipeline composite structure. As can be seen from the figures, the noise reduction effect of the composite structure is obvious after the ventilation, noise reduction and dust removal pipeline composite structure is slightly lower than that of Example 1.

[0082] Example 3

[0083] Five ventilation, noise reduction and dust removal unit structures are installed in the 120mm×120mm ventilation duct. Each unit shell has 3×17 cylindrical through holes on its side. The horizontal distance between each unit is 4mm. The composite structure is 120mm long.

[0084] like Figure 11 As shown, in Example 3, the pipe size is 120mm×120mm, the pipe cutoff frequency is 850Hz, and the average sound transmission loss of the ventilation, noise reduction and dust removal pipe composite structure is 20dB in the frequency range of 10 to 1429Hz. In the frequency range of 85 to 1429Hz, the sound transmission loss is greater than 10dB, and the sound transmission loss at 1429Hz is 27dB.

[0085] like Figure 12 As shown, in Example 3, the average value of the continuous power spectral density from 10 to 1429 Hz is 2.6 W / Hz, and the power spectral density at 1429 Hz is 4.6 W / Hz. The overall continuous power spectral density is slightly less than that of Example 1 and slightly greater than that of Example 2.

[0086] like Figure 17 , Figure 18 The figures show the sound pressure modal cloud diagrams of Example 3 of the pipeline composite structure at 600Hz and 1200Hz. It can be seen from the figures that the sound attenuation effect of the composite structure is obvious. At 1200Hz, the sound attenuation effect of Example 3 is slightly higher than that of Example 1. At 600Hz, the sound attenuation effect of Example 3 is slightly higher than that of Example 2 and slightly lower than that of Example 1.

[0087] As can be seen from the above embodiments, the structure of the present invention can block the acoustic energy carried by the incident sound wave, resulting in a high transmission loss and achieving a noise reduction effect; the units of the composite structure have air circulation areas, overcoming the problem of ventilation in traditional sound insulation structures, and the activated carbon backing has a dust removal function. Therefore, the structure of the present invention has broad application prospects in the design of ventilation windows and exhaust ducts, and ventilation sound barriers.

[0088] This invention is not limited to the above embodiments. Based on the technical solutions disclosed in this invention, those skilled in the art can make some substitutions and modifications to some of the technical features without creative effort, and all such substitutions and modifications are within the protection scope of this invention.

Claims

1. A composite duct structure for ventilation, noise reduction, and dust removal, characterized in that, It includes several composite structural units arranged obliquely along the axial direction of the pipe cavity, and the composite structural units are arranged in an array according to a periodic arrangement; The composite structural unit is a shell structure with a parallelogram cross-section and an internal cavity. Several cylindrical through holes are opened on one side of the composite structural unit shell in a periodic arrangement. An activated carbon backing is applied inside the unit shell opposite to the through holes. The unit shells are arranged at equal intervals with air flow areas. The cylindrical through hole is arranged obliquely along the side wall of the composite structure unit shell. The composite structural units arranged in a periodic pattern serve as the noise inlet and outlet in the pipe cavity, with the airflow direction as the noise inlet.

2. The duct composite structure for ventilation, noise reduction, and dust removal according to claim 1, characterized in that, The longitudinal section of the composite structural unit is arranged at an angle of 45° to 55° along the horizontal plane of the inner cavity of the pipe.

3. The duct composite structure for ventilation, noise reduction, and dust removal according to claim 1, characterized in that, The adjacent composite structural units arranged in a periodic pattern are spaced at equal intervals, and the spacing between them is the same as the wall thickness of the composite structural unit.

4. The duct composite structure for ventilation, noise reduction, and dust removal according to claim 1, characterized in that, The cylindrical through holes are arranged periodically in a pattern of (2~3)×17 on one side of the composite structural unit shell.

5. The duct composite structure for ventilation, noise reduction, and dust removal according to claim 1, characterized in that, The axis of the cylindrical through hole is at an angle of 80 to 90 degrees to the plane of the composite structure unit shell.

6. The duct composite structure for ventilation, noise reduction, and dust removal according to claim 1, characterized in that, The composite structural unit is made of aluminum alloy plate or acrylic plate.

7. The duct composite structure for ventilation, noise reduction, and dust removal according to claim 1, characterized in that, The two sides of the composite structure unit shell are welded to the pipe wall.

8. The duct composite structure for ventilation, noise reduction, and dust removal according to claim 1, characterized in that, The composite structure unit shell and the activated carbon backing are bonded together with adhesive.

9. A duct composite structure for ventilation, noise reduction, and dust removal as described in any one of claims 1-8, used in ventilation equipment for engines, cranes, and blowers.

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