Low-frequency ventilation and noise elimination structure of box-type substation

Abstract

The application discloses a low-frequency ventilation and noise elimination structure of a box-type transformer substation, which comprises a shell, multistage side-branch resonant sound-absorbing bodies, a main ventilation channel, a composite sound-absorbing layer and a constraint damping layer. The shell is provided with an air inlet end and an air outlet end. The main ventilation channel is formed in the shell and is arranged through the shell along the airflow direction from the air inlet end to the air outlet end. The multistage side-branch resonant sound-absorbing bodies are arranged on the circumferential or axial outer side of the main ventilation channel and are communicated with the main ventilation channel through neck channels. The composite sound-absorbing layer is arranged on the inner wall side of the main ventilation channel, and the constraint damping layer is arranged on the inner side of the shell. The multistage side-branch resonant sound-absorbing bodies have different cavity volumes, neck cross-sectional areas and equivalent neck lengths so as to correspondingly absorb different low-frequency noises. The low-frequency noise of 50-200 Hz can be multi-peak coupled and eliminated by the application under the premise that the ventilation and heat dissipation channel of the box-type transformer substation is kept through, and the application has the advantages of low pressure loss, compact structure, convenient installation and outdoor operation adaptability.

Description

Technical Field

[0001] This invention relates to a noise reduction structure, specifically a low-frequency ventilation noise reduction structure for a prefabricated substation. Background Technology

[0002] With the rapid development of urban power distribution systems, industrial parks, residential communities, and new energy supporting facilities, prefabricated substations are widely used due to their compact structure, convenient installation, and small footprint. During operation, transformers, high and low voltage switchgear, cooling fans, and related electrical components in prefabricated substations generate continuous noise, and their noise emissions must meet relevant environmental noise control requirements. How to reduce the impact of prefabricated substations on the surrounding acoustic environment while ensuring safe equipment operation and ventilation has become an important issue in power equipment engineering applications.

[0003] Prefabricated substations have highly integrated internal equipment and limited space. The noise generated by equipment such as transformers is typically concentrated in the 50Hz-200Hz range. This noise is characterized by long wavelengths, slow attenuation, and strong penetration. Conventional porous sound-absorbing materials or ordinary resistive silencing structures, with their limited thickness, cannot achieve ideal low-frequency noise reduction. Furthermore, prefabricated substations need to continuously dissipate heat from the equipment during operation. Simply increasing the thickness of the sound-absorbing material or adopting a closed sound insulation structure can easily increase ventilation resistance and affect heat dissipation safety. Existing ventilation and noise reduction devices mostly focus on mid-to-high frequency noise control, or suffer from problems such as large size, complex structure, and insufficient installation adaptability, making it difficult to simultaneously address low-frequency noise reduction, low-pressure-loss ventilation, lightweight design, and outdoor operation requirements. Therefore, it is necessary to develop a low-frequency ventilation and noise reduction structure suitable for the air intake and exhaust locations of prefabricated substations to achieve synergistic effects of low-frequency noise suppression and ventilation / heat dissipation within a limited space. Summary of the Invention

[0004] Purpose of the invention: In order to overcome the problems of insufficient low-frequency noise reduction effect, large ventilation resistance, large structural volume and poor installation adaptability of existing prefabricated substation ventilation and noise reduction structures in limited installation space, this invention provides a low-frequency ventilation and noise reduction structure for prefabricated substations, which improves the noise reduction capability for low-frequency noise of 50~200 Hz while ensuring the ventilation and heat dissipation requirements of the prefabricated substation.

[0005] Technical Solution: The present invention discloses a low-frequency ventilation and noise reduction structure for a prefabricated substation, comprising a shell, a multi-stage side-supported resonant sound absorber, a main ventilation duct, a composite sound-absorbing layer, and a constraint damping layer. The shell has an air inlet and an air outlet. The main ventilation duct is formed inside the shell and extends through the airflow direction from the air inlet to the air outlet. The multi-stage side-supported resonant sound absorber is disposed on the circumferential or axial outer side of the main ventilation duct and is connected to the main ventilation duct through a neck channel. The composite sound-absorbing layer is disposed on the inner wall of the main ventilation duct, and the constraint damping layer is disposed on the inner side of the shell.

[0006] Furthermore, the shell is a cylindrical, square, rectangular, or irregularly shaped cylindrical structure with a length of 180-200 mm and a thickness of 2-3 mm. Preferably, the shell is a cylindrical structure with a length of 200 mm and a thickness of 2 mm.

[0007] Furthermore, the multi-stage side-branch resonant absorber includes several resonant absorbers for different frequency band noises. The resonant absorber includes 1 to 4 side-branch resonant cavity units. The cavity volume, neck channel cross section and equivalent neck length of the side-branch resonant cavity units are different, so as to act on low frequency noise in the range of 50 to 200 Hz respectively.

[0008] Furthermore, the multi-stage side-branch resonant sound absorber has a ring-shaped sound-absorbing structure with an outer diameter of 90-120 mm and an inner diameter of 50-100 mm. Preferably, the outer diameter of the multi-stage side-branch resonant sound absorber is 110 mm and the inner diameter is 74 mm.

[0009] Furthermore, the side-branch resonant cavity unit is a Helmholtz resonant cavity, which is a combination cavity composed of a ring cavity, an arc cavity, a fan-shaped cavity, a cylindrical cavity, or multiple circumferentially distributed cavities, and the number is 1 to 4; the neck channel is an air neck tube, a slit neck, a perforated neck, or a combination thereof. Preferably, the side-branch resonant cavity unit is an arc-shaped Helmholtz resonant cavity, and the number is 4.

[0010] Furthermore, the main ventilation duct is a straight-through, gradually narrowing and expanding, eccentric, bent, or reducing ventilation duct, with a maximum flow diameter of 110 mm, a minimum flow diameter of 74 mm, and an axial length of 80~200 mm. Preferably, the axial length is 200 mm.

[0011] Furthermore, the composite sound-absorbing layer includes a perforated plate, a porous dissipation layer, and a back plate; its outer diameter is 100~140 mm, its inner diameter is 80~120 mm, and its length is 80~200 mm. Preferably, the outer diameter is 140 mm, the inner diameter is 110 mm, and the length is 200 mm.

[0012] Furthermore, the thickness of the perforated plate is 1~1.5 mm, the perforation diameter is 1~5 mm, and the perforation rate is 0.01~1%. Preferably, the thickness of the perforated plate is 1 mm, the perforation diameter is 5 mm, and the perforation rate is 0.05%.

[0013] Furthermore, the porous dissipation layer is a flame-retardant porous fiber material layer, a polyester fiber sound-absorbing cotton layer, a melamine foam layer, a glass fiber cotton layer, or a basalt fiber cotton layer, and the thickness of the porous dissipation layer is 5~50 mm, preferably 29 mm.

[0014] Furthermore, the back panel is a thin metal sheet or a fiber-reinforced composite board with a thickness of 1~2mm.

[0015] Furthermore, the constrained damping layer includes a viscoelastic damping layer, a shear body, and a constraining layer; the viscoelastic damping layer is a silicone-based foamed damping material layer, a butyl damping material layer, or a polyurethane damping material layer, with a thickness of 1~2 mm, preferably 2 mm; the shear body is an origami-type mechanical metamaterial structure with a thickness of 1~5 mm, preferably 4 mm; the constraining layer is a thin metal plate, a fiber-reinforced composite plate, or a flame-retardant polymer plate, with a thickness of 1~5 mm, preferably 2 mm.

[0016] Furthermore, the air inlet and outlet are equipped with connecting flanges, rainproof structures, drainage structures, insect screens, vibration damping pads, or detachable maintenance structures. One end of the low-frequency ventilation and noise reduction structure used in the prefabricated substation is bolted to equipment such as the cooling fan, and the other end is bolted to the rainproof cap.

[0017] Working Principle: When broadband noise from the prefabricated substation enters the low-frequency ventilation and silencing structure vertically, the local resonance and inter-vibration coupling effect of the multi-stage side-supported resonant sound absorbers effectively absorb the low-frequency (50~200 Hz) noise. Through reflection and friction, this noise is converted into heat energy, reducing the total noise energy. Next, mid- and high-frequency noise enters the composite sound-absorbing layer tangentially. Passing through the perforated plate, the viscous damping, heat conduction loss, scattering, and absorption of the porous dissipative layer effectively absorb the mid- and high-frequency noise. When a small amount of low-frequency noise penetrates the constrained damping layer, the synergistic effect of the viscoelastic damping layer's viscoelasticity, deformation energy absorption, and friction effectively reduces structural vibration caused by the low-frequency noise. Simultaneously, the large amount of heat generated by components such as high-voltage switchgear, transformers, and low-voltage distribution equipment in the prefabricated substation is rapidly dissipated through the ventilation duct by a forced-draft silent fan, meeting the engineering requirements for ventilation and heat dissipation while ensuring silencing performance.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0019] 1. Novel structure, light weight, and high degree of integration, meeting the comprehensive requirements of ventilation and noise reduction in prefabricated substations;

[0020] 2. The multi-stage side-branch resonant structure effectively improves the noise reduction performance of low-frequency noise in the 50~200 Hz range;

[0021] 3. By attenuating mid-to-high frequency noise through composite sound-absorbing layers and suppressing low-frequency vibration and secondary sound radiation of the shell through constraint damping layers, the coordinated control of full-frequency band and structural vibration is achieved.

[0022] 4. The noise reduction performance is related to its structural parameters. The noise reduction frequency band and performance can be changed by adjusting the structural parameters. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the present invention;

[0024] Figure 2 This is a front view of the present invention;

[0025] Figure 3 This is a side view of the present invention;

[0026] Figure 4 This is a cross-sectional view of the present invention (AA).

[0027] Figure 5 This is a BB cross-sectional view of the present invention;

[0028] Figure 6 This is a schematic diagram of the structure of the multi-stage side-branch resonant sound absorber 2 of the present invention. Detailed Implementation

[0029] Example 1

[0030] like Figures 1-3 The low-frequency ventilation and noise reduction structure for the prefabricated substation consists of a shell 1, a multi-stage side-supported resonant sound absorber 2, a main ventilation duct 3, a composite sound-absorbing layer 4, and a constraint damping layer 5. Its external dimensions are 150mm (Φ). o )×200mm (L), Φ o L is the outer diameter, and L is the length. The shell 1 contains a constraint damping layer 5 and a composite sound-absorbing layer 4 arranged sequentially. The shell 1 is welded from steel and has a cylindrical shape, but can also be a square, rectangular, or irregularly shaped cylindrical structure, with a length of 200mm and a thickness of 2mm. The main ventilation duct 3 is a straight-through, gradually expanding, eccentric, bent, or variable-diameter ventilation duct formed by the shell 1, multi-stage side-supported resonant sound absorbers 2, and the composite sound-absorbing layer 4; its maximum flow diameter is 110mm, its minimum flow diameter is 74mm, and its flow length is 200mm.

[0031] like Figure 4 The composite sound-absorbing layer 4 consists of a perforated plate 41, a porous dissipation layer 42, and a back plate 43 forming a ring-shaped structure with an external dimension of 140 mm (Φ). o )×110mm (Φ i )×200mm (L), Φ o Φ is the outer diameter. iL is the inner diameter, and L is the length. The perforated plate 41 has a thickness of 1 mm, a perforation diameter of 5 mm, and a perforation rate of 0.05%. The porous dissipation layer 42 is BASF sound-absorbing cotton with a thickness of 29 mm. The porous dissipation layer 42 can be replaced with any one of the following: a flame-retardant porous fiber material layer, a melamine foam layer, a glass fiber cotton layer, or a basalt fiber cotton layer. When noise generated by the cooling fan passes through the perforated plate 41 and enters the porous dissipation layer 42, it effectively absorbs mid- and high-frequency noise through the combined effects of viscous damping, heat conduction loss, and absorption. The back plate 43 is a thin metal plate or a fiber-reinforced composite board with a thickness of 1-2 mm. The constraint damping layer 5 consists of a viscoelastic damping layer 51, a shear body 52, and a constraint layer 53, with a thickness of 6 mm. The viscoelastic damping layer 51 is a silicone-based foamed damping material layer, a rubber-based damping material layer, a butyl damping material layer, or a polyurethane damping material layer, with a thickness of 2 mm. The shear body 52 is a spatially periodically distributed origami-type mechanical metamaterial structure with a thickness of 4 mm. The constraint layer is a fiber-reinforced composite plate, or it can be a thin metal plate or a flame-retardant polymer plate, with a thickness of 2 mm.

[0032] like Figures 5-6 The multi-stage side-branch resonant sound absorber 2 consists of three-stage annular resonant sound absorbers for different frequency bands of noise, specifically a first resonant sound absorber 21, a second resonant sound absorber 22, and a third resonant sound absorber 23, with an external dimension of 110 mm (Φ). o )×134mm (Φ i ), Φ o Φ is the outer diameter. i The inner diameter is defined as follows. The three-stage annular resonant absorbers (first resonant absorber 21, second resonant absorber 22, and third resonant absorber 23) are each composed of four arc-shaped side-branch resonant cavity units (each with different cavity volumes, neck channel cross-sections, and equivalent neck lengths), as shown in Table 1. Due to local resonance, they absorb low-frequency noise at 50–63 Hz, 80–100 Hz, and 125–200 Hz, respectively. The side-branch resonant cavity units are Helmholtz resonant cavities, which can be annular cavities, arc-shaped cavities, fan-shaped cavities, cylindrical cavities, or combinations of multiple circumferentially distributed cavities. The neck channel can be an air neck, a slit neck, a perforated neck, or a combination thereof. Furthermore, due to the long-range and proximity coupling effect between the first resonant sound absorber 21, the second resonant sound absorber 22, and the third resonant sound absorber 23, the sound absorption frequency band is broadened, effectively absorbing low-frequency noise in the 50~200Hz frequency band.

[0033] Table 1. Structural parameters of the three-stage circular resonant sound absorber

[0034]

[0035] Example 2

[0036] This embodiment aims to explore the relationship between noise reduction performance and its structural parameters.

[0037] Based on the low-frequency ventilation and noise reduction structure for the box-type substation described in Example 1, while keeping the overall arrangement of the shell 1, main ventilation duct 3, composite sound-absorbing layer 4, and constraint damping layer 5 unchanged, the structural parameters of the multi-stage side-support resonant sound absorber 2 are adjusted, especially the cavity volume, neck channel cross-section, and equivalent neck length of the arc-shaped resonant cavity unit, as well as the relevant parameters of the composite sound-absorbing layer 4 and constraint damping layer 5, in order to analyze the influence of each parameter on the low-frequency noise reduction frequency point, noise reduction peak value, and noise reduction bandwidth, as shown in Table 2.

[0038] Table 2 Structural parameters of the third-level circular resonant sound absorber

[0039]

[0040] The multi-stage side-branch resonant sound absorber includes a first resonant sound absorber 21, a second resonant sound absorber 22, and a third resonant sound absorber 23, corresponding to low-frequency noise of 50~63Hz, 80~100Hz, and 125~200Hz, respectively. Each stage of the resonant sound absorber is connected to the main ventilation duct 3 through a neck channel, and different resonant frequencies are formed by changing the cavity volume, the cross-sectional area of ​​the neck channel, and the equivalent neck length. The resonant frequency of the arc-shaped resonant cavity unit can be determined by the following formula.

[0041]

[0042] Where f is the resonant frequency, c is the speed of sound in air, S is the equivalent cross-sectional area of ​​the neck channel, V is the equivalent volume of the cavity, and L eff Let V be the equivalent neck length of the cervical passage. As shown in the equation, under otherwise unchanged conditions, increasing the cavity volume V or the equivalent neck length L... eff Increasing the resonant frequency f shifts it towards lower frequencies; increasing the equivalent cross-sectional area S of the neck channel shifts the resonant frequency f towards higher frequencies. Therefore, by adjusting the above structural parameters, the multi-stage side-supported resonant absorber 2 can perform frequency division and noise reduction for low-frequency noise in the 50~200Hz range.

[0043] Furthermore, the perforation diameter and perforation ratio of the perforated plate 41 in the composite sound-absorbing layer 4, and the thickness of the porous dissipation layer 42, affect the mid-to-high frequency noise dissipation and overall acoustic impedance matching. If the perforation ratio is too low, the ability of sound waves to enter the porous dissipation layer 42 is weakened; if the perforation ratio is too high, the acoustic impedance adjustment effect of the perforated plate 41 decreases. Therefore, the perforated plate 41 needs to be optimized in conjunction with the structural dimensions of the main ventilation duct 3 and the target frequency band. Meanwhile, increasing the thickness of the porous dissipation layer 42 is beneficial for enhancing mid-to-high frequency dissipation, but excessive thickness will occupy ventilation space and increase ventilation resistance.

[0044] In addition, the viscoelastic damping layer 51, shear body 52, and constraint layer 53 in the constraint damping layer 5 are used to suppress low-frequency vibrations and secondary sound radiation of the shell 1. When the thickness of the viscoelastic damping layer 51 increases, its energy dissipation capacity is enhanced, but excessive thickness will increase the structural weight; when the thickness and distribution of the shear body 52 change, the shear deformation energy dissipation capacity of the constraint damping layer 5 changes accordingly.

[0045] This embodiment demonstrates that by optimizing the structural parameters of the multi-stage side-supported resonant sound absorber 2, the composite sound-absorbing layer 4, and the constraint damping layer 5, frequency division control and wideband noise reduction of 50~200Hz low-frequency noise can be achieved while maintaining the continuity of the main ventilation duct 3 and meeting the ventilation and heat dissipation requirements of the box-type substation.

Claims

1. A low-frequency ventilation and noise reduction structure for a prefabricated substation, characterized in that: The system includes a shell (1), a multi-stage side-supported resonant sound absorber (2), a main ventilation duct (3), a composite sound-absorbing layer (4), and a constraint damping layer (5). The shell (1) has an air inlet (11) and an air outlet (12). The main ventilation duct (3) runs through the air inlet (11) to the air outlet (12). The multi-stage side-supported resonant sound absorber (2) is located on the circumferential or axial outer side of the main ventilation duct (3) and is connected to the main ventilation duct (3) through a neck channel. The composite sound-absorbing layer (4) is located on the inner wall of the main ventilation duct (3), and the constraint damping layer (5) is located on the inner side of the shell (1). The shell (1) is a cylindrical, square, rectangular or irregular cylindrical structure, with an axial length of 180-200 mm and a wall thickness of 2-3 mm. One end of the low-frequency ventilation and noise reduction structure of the box-type substation is bolted to the cooling fan, and the other end is bolted to the rainproof cap. The multi-stage side-branch resonant sound absorber (2) includes a first resonant sound absorber (21), a second resonant sound absorber (22), and a third resonant sound absorber (23), each composed of four arc-shaped side-branch resonant cavity units. The cavity volume, neck channel cross-section, and equivalent neck length of the side-branch resonant cavity units are different. The first resonant sound absorber (21), the second resonant sound absorber (22), and the third resonant sound absorber (23) absorb low-frequency noise of 50~63Hz, 80~100Hz, and 125~200Hz, respectively. The constraint damping layer (5) includes a viscoelastic damping layer (51), a shear body (52), and a constraint layer (53); the viscoelastic damping layer (51) is a silicone-based foamed damping material layer, a rubber-based damping material layer, a butyl damping material layer, or a polyurethane damping material layer, with a thickness of 1~2 mm; the shear body (52) is an origami-type mechanical metamaterial structure with a thickness of 1~5 mm; the constraint layer (53) is a metal sheet, a fiber-reinforced composite board, or a flame-retardant polymer board with a thickness of 1~5 mm.

2. The low-frequency ventilation and noise reduction structure for a prefabricated substation according to claim 1, characterized in that: The side-branch resonant cavity unit is a Helmholtz resonant cavity, which is a combination cavity composed of a ring cavity, an arc cavity, a fan cavity, a cylindrical cavity, or multiple circumferentially distributed cavities; the neck channel is an air neck tube, a slit neck, a perforated neck, or a combination thereof.

3. The low-frequency ventilation and noise reduction structure for a prefabricated substation according to claim 1, characterized in that: The main ventilation duct (3) is a straight, gradually narrowing and expanding, eccentric, bent or different diameter ventilation duct, with a maximum flow diameter of 110 mm, a minimum flow diameter of 74 mm, and an axial length of 80~200 mm.

4. A low-frequency ventilation and noise reduction structure for a prefabricated substation according to claim 1, characterized in that: The composite sound-absorbing layer (4) includes a perforated plate (41), a porous dissipation layer (42), and a back plate (43); its outer diameter is 100~140 mm, its inner diameter is 80~120 mm, and its length is 80~200 mm.

5. A low-frequency ventilation and noise reduction structure for a prefabricated substation according to claim 4, characterized in that: The thickness of the perforated plate (41) is 1~1.5 mm, the perforation diameter is 1~5 mm, and the perforation rate is 0.01%~1%.

6. A low-frequency ventilation and noise reduction structure for a prefabricated substation according to claim 4, characterized in that: The porous dissipation layer (42) is a flame-retardant porous fiber material layer, a polyester fiber sound-absorbing cotton layer, a melamine foam layer, a glass fiber cotton layer, or a basalt fiber cotton layer, with a thickness of 5~50 mm.

7. The low-frequency ventilation and noise reduction structure for a prefabricated substation according to claim 4, characterized in that: The back plate (43) is a thin metal plate or a fiber-reinforced composite plate with a thickness of 1~2mm.

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