Corrugated composite silencer for low-frequency noise reduction in transformer

Abstract

The invention relates to the field of noise reduction control of power equipment, in particular to a corrugated composite silencer used for reducing low-frequency noise in a transformer. The corrugated composite silencer structurally comprises a corrugated expansion cavity, a high-frequency sound absorption layer, a backflow cavity, an internal perforated plate and a hard wall, the corrugated expansion cavity is a main body part of the silencer and is directly connected with the inlet side and the outlet side of the silencer; the high-frequency sound absorption layer is attached to the outer side of the corrugated expansion cavity and is separated from the corrugated expansion cavity by an internal perforated plate; the backflow cavity is located on the outer side of the high-frequency sound absorption layer and is separated from the high-frequency sound absorption layer through a hard wall and an internal perforated plate. Wherein the corrugated expansion cavity adopts a corrugated wall surface and is used for improving the equivalent acoustic impedance of the silencer structure and improving the low and medium frequency noise reduction effect of the silencer; the high-frequency sound absorption layer is filled with high-frequency sound absorption materials such as glass fiber cotton so as to improve the medium-high frequency noise reduction capacity of the structure. And the backflow cavity is used for specifically absorbing noise with specific frequency at low and medium frequencies. The corrugated wall surface is combined with the backflow cavity, the corrugated composite silencer structure for low-frequency noise reduction in the transformer is designed, and the actual noise reduction requirements of most transformers can be met.

Description

Technical field:

[0001] The present invention relates to the field of noise reduction control of electric power equipment, and in particular to a corrugated composite muffler structure for reducing medium and low frequency noise of a transformer. Background technology:

[0002] With the rapid development of society, the economy, and the power industry, the demand for electric energy is increasing year by year. Substations, as an essential component of the power system, perform crucial functions such as changing voltage, receiving, and distributing electrical energy. As electricity demand continues to rise, the number of substations being built is also increasing, with a trend toward embedding them in urban areas. Against this backdrop, the noise generated by transformer operation is becoming increasingly acute.

[0003] Transformer noise primarily comes from electromagnetic noise, mechanical noise, and cooling system noise. Electromagnetic noise primarily arises from the magnetostrictive effect of the iron core and the vibration of the silicon steel laminations under electromagnetic force, resulting in transformer noise at both the power frequency and higher harmonic frequencies. Mechanical noise primarily originates from winding vibration and loose fasteners. Cooling system noise is also contributed by vibration from the fan assembly and transformer oil pump. Low-frequency components (<1000Hz) of these noises have wavelengths far greater than those of common obstacles, exhibiting strong penetration and long-range propagation characteristics. These components are easily transmitted through the air and building structures to residential areas, causing noise pollution.

[0004] Traditional noise reduction technologies, such as acoustic enclosures, can block high-frequency noise through enclosed structures, but their effectiveness is limited by the diffraction effect of low-frequency sound waves. Furthermore, fully enclosed designs hinder the natural heat dissipation of transformers, necessitating the addition of forced ventilation systems, significantly increasing construction and maintenance costs. Vibration reduction measures can suppress the transmission of vibrations through solid structures, but their attenuation of airborne noise is minimal. Active noise reduction technology, which counteracts noise through the principle of phase interference, performs well in laboratory environments, but its complex algorithms, high-precision sensor requirements, and high cost limit its industrial-scale application. Mufflers, as a propagation path control technology, have attracted widespread attention due to their directional attenuation characteristics and engineering adaptability. While traditional reactive mufflers offer good broadband sound insulation at mid- and high-frequency frequencies, they are ineffective against transformer low-frequency noise. Against this backdrop, we propose a corrugated composite muffler to address the insufficient low-frequency noise reduction capabilities of traditional mufflers. Summary of the invention:

[0005] To address the inadequate low-frequency noise reduction capabilities of conventional resistive mufflers, the applicant has improved the structure of these mufflers. By leveraging the influence of the corrugated wall on acoustic impedance and the acoustic energy loss effect of the return cavity at specific frequencies, the applicant has innovatively invented a corrugated composite muffler. This muffler can meet the multiple noise reduction requirements of the main frequency bands of transformer noise.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A corrugated composite muffler, comprising:

[0008] outer cylinder;

[0009] The corrugated expansion chamber is arranged in the outer cylinder and is connected to the air inlet and outlet of the muffler, mainly used to improve the acoustic impedance of the structure;

[0010] The internal perforated plate is set on the wall of the corrugated expansion cavity, which is mainly used to increase the sound wave energy dissipation in the low-frequency range and improve the noise reduction;

[0011] The high-frequency sound-absorbing layer is arranged outside the corrugated expansion cavity and is mainly used to absorb the high-frequency part of the sound wave energy;

[0012] The reflux cavity is located on the outer layer of the high-frequency sound-absorbing layer and is mainly used to absorb sound wave energy of a specific frequency;

[0013] It is further characterized by:

[0014] The wall of the corrugated expansion chamber is corrugated rather than simply straight. The corrugation is not fixed to a certain shape, but can take many tortuous shapes:

[0015] The high-frequency sound absorbing layer is filled with cylindrical high-frequency sound absorbing material;

[0016] The high-frequency sound-absorbing material is mainly composed of glass fiber cotton;

[0017] The corrugated expansion cavity and the high-frequency sound absorbing layer are separated by an internal perforated plate;

[0018] The high-frequency sound absorbing layer is separated from the reflow cavity by a hard wall, and part of the hard wall is replaced by an internal perforated plate in the first section of the reflow cavity to allow the sound wave energy to enter the reflow cavity;

[0019] The internal perforated plate is provided with a plurality of small holes, and the internal perforated plate is described by plate thickness, perforation diameter, and porosity parameters.

[0020] The beneficial effects of the present invention are as follows:

[0021] The present invention has a simple structure, a reasonable design, and is easy to operate. Pipeline noise enters the corrugated expansion chamber through the muffler inlet, effectively changing the acoustic impedance of the sound wave. The noise is then reduced by the high-frequency sound-absorbing layer and the reflux chamber, ultimately achieving broadband noise reduction. The muffler significantly improves the noise reduction effect in the 100-500Hz noise frequency band of the transformer. Furthermore, the muffler has a number of adjustable parameters, allowing the corrugated wall surface of the corrugated expansion chamber to be modified according to actual conditions, as well as parameters such as the aperture of the internal perforated plate to adapt to the noise reduction requirements of different situations.

[0022] Attached drawings:

[0023] Figure 1 This is a structural diagram of a corrugated composite muffler for transformer noise reduction provided by the present invention.

[0024] Figure 2 yes Figure 1 Schematic diagram of a single-stage muffler with a medium corrugated composite muffler

[0025] Figure 3 yes Figure 2 Cross-sectional diagram of a medium corrugated composite muffler

[0026] Figure 4 yes Figure 1 Sound transmission loss diagram of medium corrugated composite muffler

[0027] The numbers in the attached figure are as follows: 1, inlet side 2, outlet side 3, outer tube 4, corrugated expansion cavity 5, reflux cavity 6, high frequency sound absorption layer 7, internal perforated plate 8, glass fiber wool 9, hard wall Specific implementation method:

[0028] In order to more clearly explain the purpose of the embodiment of the present invention and the features and advantages of the technical solution, the technical solution of the embodiment of the present invention is now described in detail and completely in conjunction with the drawings of the patent of the present invention. It should be noted that the embodiments described below are only part of the embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0029] like Figure 1 The figure shows a corrugated composite muffler for transformer noise reduction, comprising an inlet 1, an outlet 2, and an outer tube 3. The corrugated composite muffler is composed of three single-stage corrugated composite mufflers of different lengths and is cylindrical in shape. The inlet 1 and outlet 2 are located on either side of the muffler body, serving as gas inflow and outflow channels.

[0030] like Figure 2 The figure shows the single-pole part of the corrugated composite muffler. Figure 3The figure shows a cross-sectional schematic diagram of the single-pole composite silencer. It includes a corrugated expansion chamber 4, a recirculation chamber 5, a high-frequency sound-absorbing layer 6, an internal perforated plate 7, and glass fiber wool 8. The surface of the corrugated expansion chamber 4 is corrugated, with a certain corrugation pattern controlled by a sine function. The high-frequency sound-absorbing layer 6 is located outside the corrugated expansion chamber 4, and the interior of the high-frequency sound-absorbing layer 6 is filled with glass fiber wool 8. The high-frequency sound-absorbing layer 6 is separated from the corrugated expansion chamber 4 by an internal perforated plate 7, while the recirculation chamber 5 is separated from the high-frequency sound-absorbing layer 6 by a hard wall 9 and the internal perforated plate 7. It should be noted that the internal perforated plate 7 between the recirculation chamber 5 and the high-frequency sound-absorbing layer 6 serves as a necessary channel for sound wave energy to enter the recirculation chamber 5. The internal perforated plate 7 is provided with small holes on its wall, which are controlled by porosity and pore size. The hard wall 9 is used to prevent the random diffusion of sound wave energy and the formation of the recirculation chamber 5, and no small holes are provided on the hard wall 9.

[0031] The corrugated expansion chamber 4, the recirculation chamber 6, and the high-frequency sound-absorbing layer 7 together form a corrugated resonance structure. Adjusting the corrugated wall surface of the corrugated expansion chamber 4 can alter the internal equivalent acoustic impedance of this structure, thereby varying the noise reduction effect of the muffler. Furthermore, the internal perforated plate 7 has three adjustable parameters: plate thickness, pore diameter, and porosity. By varying these three values, the muffler's peak noise reduction performance can be shifted to suit different operating conditions.

[0032] In at least one embodiment, the corrugated composite muffler is composed of three single-stage composite mufflers.

[0033] In at least one embodiment, the equivalent radius of the corrugated expansion chamber 4 should be larger than the expansion chamber at the muffler inlet, and preferably exceeds 5-10 cm.

[0034] In at least one embodiment, the inlet side 1 , the outlet side 2 , the corrugated expansion cavity 4 , the high-frequency sound absorbing layer 6 and the reflow cavity 5 should be equivalent to concentric cylinders.

[0035] In at least one embodiment, the corrugated wall surface of the corrugated expansion chamber 4 is characterized by a sine function.

[0036] In at least one embodiment, the amplitude of the sine function corresponding to the corrugated wall should be smaller than the thickness of the high-frequency sound absorbing layer, and should also be smaller than the difference between the equivalent radius of the corrugated wall and the inlet side radius to ensure the ventilation performance of the muffler.

[0037] In at least one embodiment, the thickness of the reflow cavity 5 should be less than or equal to the thickness of the high-frequency sound absorbing layer 6 to ensure a compact structure of the entire muffler.

[0038] In at least one embodiment, the porosity of the internal perforated plate 7 is controlled to be 0.1-0.3, the perforation diameter is controlled to be 0.4-1.0 mm, and the thickness of the perforated plate is controlled to be 1.0-2.0 mm.

[0039] In at least one embodiment, the high-frequency sound absorbing material filled in the high-frequency sound absorbing layer is glass fiber wool.

[0040] In at least one embodiment, single-stage corrugated composite mufflers of different lengths are separated by hard walls, and the corrugated expansion chamber 4 is a directly connected portion.

[0041] In at least one embodiment, the length of the single-stage corrugated composite muffler is controlled between 0.5-1.0 m.

[0042] It is understood that after the sound wave enters the muffler from the inlet side 1, it first reaches the corrugated expansion chamber 4. Since there is no obstruction in the corrugated expansion chamber 4, the sound wave will diffuse in all directions, most of which will enter the high-frequency sound absorption layer 6 through the internal perforated plate 7. Since the wall surface of the corrugated expansion chamber 4 is corrugated, the acoustic impedance of the corresponding internal structure is increased. Therefore, compared with traditional structures, the sound wave energy loss is greater and the sound elimination effect is more excellent. When the sound wave energy enters the high-frequency sound absorption layer 6, since the high-frequency sound absorption layer 6 is filled with glass fiber wool 8, the mid- and high-frequency portions of the sound wave energy will be partially absorbed, thus ensuring the mid- and high-frequency noise reduction capability of the muffler. After the sound wave energy continues to propagate through the internal perforated plate 7 of the second layer, it will enter the reflux chamber 5 of the muffler. The design of the reflux chamber 5 is derived from the 1 / 4 wavelength tube theory in the field of acoustics. When the length of the wavelength tube is properly designed, the absorption of sound wave energy of any frequency can be achieved. Therefore, the reflux chamber 5 is mainly used to absorb sound wave energy at low frequencies, which can achieve low-frequency noise reduction of the muffler.

[0043] In this example, the corrugated composite muffler consists of three single-stage corrugated composite mufflers. After the sound wave energy is dissipated within the first single-stage muffler, it enters the next two single-stage mufflers for further attenuation. These three single-stage mufflers are of different lengths, and according to the 1 / 4 wavelength management theory mentioned above, they correspond to different primary noise reduction bands in the low-frequency range. Therefore, after being processed by these three single-stage corrugated composite mufflers, the sound wave energy emerges from outlet side 2. At this point, the noise has undergone multiple stages of processing, and the sound wave energy has been significantly reduced.

[0044] A simulation experiment was conducted on one of the embodiments. The 10-1000Hz noise generated by the transformer was simulated in the simulation software. A plane wave radiation with an amplitude of 1Pa was set at the inlet side 1 of the corrugated composite silencer. The sound transmission loss (STL) was used to evaluate the silencer effect. By simulating and calculating the silencer model, the transmission loss curve of the structure was finally obtained. Figure 4 As shown in the figure, the horizontal axis is the sound wave frequency and the vertical axis is the sound wave transmission loss.

[0045] Calculations show that the corrugated composite silencer achieves an average sound insulation of 58.81dB in the 20-1000Hz range, with the most significant noise reduction effect at 300-700Hz. Furthermore, at the transformer's main low-frequency noise points of 100Hz, 200Hz, and 300Hz, the silencer achieves noise reduction effects of 49.05dB, 51.35dB, and 75.59dB, respectively. The silencer also features a relatively smooth transmission loss curve, fully meeting the noise reduction requirements of most transformers.

[0046] The above description is merely a preferred embodiment of the present invention and is not to be construed as limiting the scope of protection of the present invention. It should be emphasized that any improvement, modification, or substitution based on the inventive concept of the present invention, or its direct or indirect application in other related technical fields, falls within the scope of protection of the present invention.

Claims

1. A corrugated composite muffler structure for low-frequency noise reduction in transformers, characterized in that: include: outer cylinder; The corrugated expansion chamber is arranged in the outer cylinder, and the corrugated expansion chamber includes a corrugated wall surface and a rigid support frame. The corrugated wall surface is provided with small holes corresponding to the internal perforated plate; The high-frequency sound-absorbing layer is arranged inside the outer cylinder, outside the corrugated expansion cavity and covers the corrugated expansion cavity, and is used to fill the high-frequency sound-absorbing material; The reflux cavity is arranged in the outer tube, outside the high-frequency sound absorbing layer and covers the high-frequency sound absorbing layer, and is used to reduce low-frequency noise of a specific frequency; High-frequency sound-absorbing material is arranged inside the high-frequency sound-absorbing layer to absorb medium and high-frequency noise; Internal perforated plates are installed at the separation between the corrugated expansion cavity and the high-frequency sound absorbing layer and at the sound wave transmission channel between the reflow cavity and the high-frequency sound absorbing layer to increase the sound wave energy loss and reduce the noise in the low-frequency range; The hard wall is provided at the dividing point between the recirculation cavity and the high-frequency sound absorbing layer and at the boundary of the single-stage corrugated composite muffler to form recirculation cavities of different lengths; The inlet side is placed at the front end of the entire muffler device to guide the noise into the muffler; The outlet side, at the end of the entire muffler device, is used to emit the processed noise.

2. The corrugated composite muffler structure for transformer low-frequency noise reduction according to claim 1, characterized in that: The reflow cavity is separated from the high-frequency sound absorbing layer by a hard wall, but the reflow cavity near the inlet side is an internal perforated plate instead of a hard wall, for air to propagate and enter the reflow cavity; The length ratio of the perforated plate to the hard wall is about 1:4; The perforated plate and the hard wall should be of the same thickness.

3. The corrugated composite muffler structure for transformer low-frequency noise reduction according to claim 1, characterized in that: The high-frequency sound-absorbing material is mainly glass fiber cotton, which can be replaced by other high-frequency sound-absorbing materials such as foam according to actual needs.

4. The corrugated composite muffler structure for transformer low-frequency noise reduction according to claim 1, characterized in that: The corrugated wall surface of the corrugated expansion cavity is a regular corrugated shape controlled by a sine function.

5. The corrugated composite muffler structure for transformer low-frequency noise reduction according to claim 4, characterized in that: The corrugated wall surface is not strictly required to be a sinusoidal corrugated wall surface, and can be replaced by square wave, tooth-shaped or other non-simple straight wall surfaces as needed.

6. The corrugated composite muffler structure for transformer low-frequency noise reduction according to claim 1, characterized in that: The muffler is cylindrical as a whole.

7. The corrugated composite muffler structure for transformer low-frequency noise reduction according to claim 6, characterized in that: The corrugated composite muffler is composed of three single-stage corrugated composite mufflers in cascade, and the number of actual cascades can be changed according to specific needs; The length of the single-stage composite muffler should be changed according to the frequency band required for actual noise reduction; The radius and other specifications of each part of the three single-stage composite mufflers should be the same and match each other.

8. The corrugated composite muffler structure for transformer low-frequency noise reduction according to claim 1, characterized in that: The thickness of the reflow cavity should be less than or equal to the equivalent thickness of the high-frequency sound absorbing layer; The radius of the inlet side should be smaller than the minimum radius of the corrugated wall of the corrugated expansion cavity.

9. The corrugated composite muffler structure for transformer low-frequency noise reduction according to claim 1, characterized in that: Small holes are provided on the internal perforated plate, the porosity of the internal perforated plate is controlled at 0.1-0.3, the perforation diameter is controlled at 0.4-1.0 mm, and the thickness of the perforated plate is controlled at 1.0-2.0 mm.

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