Thermal convection noise reduction device based on embedded neck

Abstract

The present invention discloses a thermal convection noise reduction device based on an embedded neck type, including a multi-layer overlapping working area and a central through hole running through the multi-layer working area from the center of the working area, each layer of the working area is provided with a plurality of Helmholtz resonant cavities of the same size, and the inner wall of each Helmholtz resonant cavity is provided with an extended neck connecting the Helmholtz resonant cavity and the central through hole, and the sequence composed of the length values ​​of the multiple extended necks in the bottom layer of the working area is an arithmetic progression, and the length of the extended neck of the upper layer of the working area is equal to the length of the extended neck of the next layer plus d, where d is a positive or negative number. The device can reduce noise for ultra-wideband (440-1600Hz), has a thin thickness, a small volume, saves manufacturing materials, and is easy to install and use. In addition, the device has good heat dissipation and thermal convection performance, paving the way for more complex life scenarios and industrial needs, such as noise reduction in heat conduction of warm air pipes, heat dissipation and noise reduction in large industries, and so on.

Description

Technical Field

[0001] The invention belongs to the field of noise reduction equipment, in particular to a thermal convection noise reduction device based on an embedded neck type. Background Art

[0002] Traditional porous noise reduction materials can be modeled using uniform effective medium theory to analyze their absorption performance, and their dissipation rate is proportional to the square of the frequency. This, combined with the mass law of sound insulation, leads to a practical problem. Low-frequency noise reduction projects usually require large rigid plates and sponges, which hinder the transfer of air and heat. Therefore, people are in urgent need of supporting the process of heat and fluid transfer to reduce noise. In fact, various noises are generated, such as warm air ducts, fan noise, engine noise, and machine noise, all because we want to maintain fluid transfer while having good heat dissipation performance in daily and professional applications. In addition, the noise frequency in daily life is often complex and changeable. Absorption or sound insulation at a specific frequency is not enough to fill people's needs. Previous studies have caused anti-resonance at other frequencies while achieving low-frequency absorption, making it impossible to achieve broadband sound insulation. In summary, it is urgent to achieve ultra-wideband noise reduction while maintaining complete convection and keeping the device ultra-thin.

[0003] At present, using a Helmholtz resonator to absorb noise is a new research direction for noise reduction, but a single Helmholtz resonator can only absorb noise in a narrow frequency range. It is well known that changing the volume and neck size of the Helmholtz resonator can change the frequency of noise absorption. Current research mainly expands the noise absorption frequency range by changing the volume or neck size of the resonant cavity, such as the applicant's prior applications for CN202011512167.8-Low-frequency ultra-open ventilated adaptive high-efficiency sound absorber, CN202011512169.7-Non-single low-frequency ultra-open ventilated adjustable sound absorbing unit and CN202011509417.2-Finite element simulation and demonstration verification method of ventilated adaptive low-frequency high-efficiency sound absorber, which increases the noise absorption frequency by pulling the adjustable inner frame to adjust the volume of the inner and outer cavities. In addition, the invention patent with application number 201810144163.5 uses COMSOL and resonant cavity model to process low-frequency noise, CN111105774A-Helmholtz resonator and low-frequency broadband sound absorption and noise reduction structure based on it, CN111561252A-A broadband ventilation sound insulation window unit structure and its application, and CN112854990A-A broadband ventilation sound insulation window unit structure and its application, etc. all increase the absorption frequency by changing the cavity volume, resulting in complex structure and large volume of the equipment, making it difficult to achieve heat convection. In addition, CN111030507A-A dual-cavity coupled noise generator and power generation method adjusts the frequency of noise absorption by setting extended necks of different sizes in the cavity, and CN107589178B-A method for controlling the wavefront of sound waves by using a metasurface composed of Helmholtz resonators changes the speed of sound waves in the metasurface by adjusting the width of the rectangular gap in the microstructure unit. The volume of this noise reduction device after array is also relatively large, and its application is limited. In addition, it is difficult to ensure the heat dissipation performance when used for fluid noise reduction. Summary of the invention

[0004] The object of the present invention is to provide a thermal convection noise reduction device based on an embedded neck type, which has a thin thickness, a small volume, realizes broadband noise reduction, and has good heat dissipation.

[0005] The object of the present invention is achieved as follows: a thermal convection noise reduction device based on an embedded neck type includes multiple overlapping working areas and a central through hole running through the multiple working areas from the center of the working area, each layer of the working area is provided with multiple Helmholtz resonant cavities of the same size, and the inner wall of each Helmholtz resonant cavity is provided with an extended neck connecting the Helmholtz resonant cavity and the central through hole, the sequence composed of the length values ​​of the multiple extended necks of the bottom working area is an arithmetic progression, and the length of the extended neck of the upper working area is equal to the length of the extended neck of the lower working area plus d, where d is a positive or negative number.

[0006] Furthermore, the working area is rectangular, the central through hole is a rectangular hole, and each layer of the working area is provided with four trapezoidal Helmholtz resonant cavities.

[0007] Furthermore, the thickness of each layer of the working area is 10 mm.

[0008] Furthermore, the working area has 5 floors.

[0009] Furthermore, the width of all the extension necks is 6 mm, the minimum length of the extension neck in the lowermost working area is 5 mm, and d is 2.5 mm.

[0010] Furthermore, the side length of the central through hole is 65mm*65mm, and the side length of the working area is 145mm*145mm.

[0011] Furthermore, the extended neck is spiral-shaped.

[0012] Furthermore, the multi-layer overlapping working area is produced by 3D printing.

[0013] The beneficial effects of the present invention are as follows: by setting a multi-layer working area, each layer of the working area is provided with a plurality of Helmholtz resonant cavities, more Helmholtz resonant cavities can be arranged in a smaller space, thereby reducing the volume. In addition, the thickness of each layer of the working area of ​​the device can reach λ (noise wavelength) / 15, and the thickness is very small, which prevents the volume from being too large while achieving the overlap of the multi-layer working area. By setting the extended neck in each Helmholtz resonant cavity to a different length, each Helmholtz resonant cavity can absorb noise of different frequencies. Under the coupling effect of multiple Helmholtz resonant cavities, the absorption frequency range of noise is greatly increased, and a good noise reduction effect is guaranteed. In addition, the fluid (gas or water, etc.) flows through the device through the central through hole, which can realize thermal convection without affecting the transfer of heat, and is particularly suitable for noise reduction of various cold and hot fluids, such as warm air pipes, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is an overall cross-sectional schematic diagram of the present invention;

[0015] Figure 2 It is a schematic plan view of a single-story work area;

[0016] Figure 3 is a schematic diagram of measuring the reflection transmission coefficient using the four-microphone method;

[0017] Figure 4 It is comsol that simulates the reflection, transmission and absorption spectra of metamaterials;

[0018] Figure 5 It is to experimentally verify the reflection, transmission and absorption spectra of metamaterials;

[0019] Figure 6 It is a comparison between the experiment with a wind speed of 1.5m / s and that with no wind speed;

[0020] Figure 7 yes Figure 3 The schematic diagram after adding the fan;

[0021] Figure 8 This is a schematic diagram of the heat flow experiment when no sample is placed;

[0022] Fig. 9 This is a schematic diagram of thermal imaging of the surface of the BK sonic tube when no sample is placed;

[0023] Fig.10 This is a schematic diagram of the sample placement for the heat flow experiment;

[0024] Fig.11 This is a thermal imaging diagram of the surface of the BK sonic tube when the sample is placed;

[0025] Fig.12 This is a schematic diagram of the heat flow experiment when placing the traditional noise reduction sponge;

[0026] Fig.13 This is a thermal imaging diagram of the surface of the BK sonic tube when a traditional noise reduction sponge is placed. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0028] like Figure 1 and Figure 2 As shown, the embedded neck-type heat convection noise reduction device of the present invention comprises a plurality of overlapping working areas 1 and a central through hole 2 penetrating the plurality of working areas 1 from the center of the working area 1, each layer of the working area 1 is provided with a plurality of Helmholtz resonant cavities 3 of the same size, and the inner wall of each Helmholtz resonant cavity 3 is provided with an extended neck 4 connecting the Helmholtz resonant cavity 3 and the central through hole 2, the sequence composed of the length values ​​of the plurality of extended necks 4 of the bottom layer of the working area 1 is an arithmetic progression, and the length of the extended neck 4 of the upper layer of the working area 1 is equal to the length of the extended neck 4 of the lower layer plus d, where d is a positive or negative number.

[0029] Each layer of the working area 1 is composed of a shell and an internal partition, and the partition divides the inner cavity of the working area 1 into a plurality of Helmholtz resonant cavities 3 of the same size. The number of Helmholtz resonant cavities 3 in each layer of the working area 1 is the same, which simplifies the structure of the device and facilitates manufacturing. The extended neck 4 is used to control the noise absorption frequency of each Helmholtz resonant cavity 3. By setting the extended necks 4 of different lengths, different Helmholtz resonant cavities 3 can absorb noise of different frequencies. By setting the length values ​​of the multiple extended necks 4 of each layer of the working area 1 to an arithmetic progression, and the length value of the extended neck 4 increases linearly with the increase of the number of layers, each Helmholtz resonant cavity 3 is coupled to each other to jointly construct a sub-wavelength broadband sound absorption superstructure, and at the same time, the anti-resonance is not obvious in the medium and low frequency range, and finally has an ultra-wideband sound insulation function. The general extended neck 4 is in a straight line shape. When the length of the extended neck 4 in some Helmholtz resonant cavities 3 is large, in order to control the Helmholtz resonant cavity 3 to a smaller size and make the extended neck 4 reach a set length, the extended neck 4 can be set to a spiral shape, a wave shape, or other curved shapes.

[0030] The number of Helmholtz resonant cavities 3 in each layer and the number of layers in the working area 1 are determined according to the frequency range of the noise. If the noise absorption frequency range needs to be increased, the total number of Helmholtz resonant cavities 3 is increased. For example, if the structure of the present invention is used to reduce noise in the frequency range of 440-1600 Hz, 4 Helmholtz resonant cavities 3 can be set in each layer of the working area 1. The working area 1 has a total of 5 layers, with a total of 20 Helmholtz resonant cavities 3.

[0031] The working area 1 can be cylindrical in shape, and the central through hole 2 can be designed as a circular hole. Preferably, the working area 1 is rectangular, and the central through hole 2 is a rectangular hole. Each layer of the working area 1 is provided with 4 trapezoidal Helmholtz resonant cavities 3, and a total of 5 layers of working areas 1 are provided, which can reduce noise for ultra-wideband (440-1600Hz), have a wide noise reduction frequency, and can absorb 90% of the noise, and have a good noise reduction effect. In addition, under this structure, the thickness of each layer of the working area 1 can be less than or equal to λ / 15, λ is the wavelength of noise, generally about 20mm, and the thickness of the working area 1 can be controlled at 10mm during actual manufacturing, which is very small. The total thickness of the 5 layers of working areas 1 is only 50mm, and the thickness of the entire noise reduction device is small, which saves manufacturing materials and is easy to install and use.

[0032] As a preferred embodiment, the width w of all the extended necks 4 is 6mm, the minimum length of the extended neck 4 of the bottom working area 1 is 5mm, and d is 2.5mm, that is, if the lengths of the four extended necks 4 of the bottom working area 1 are 5mm, 5.5mm, 6mm, and 6.5mm, respectively, then the lengths of the four extended necks 4 of the second working area 1 are 7.5mm, 8mm, 8.5mm, and 9mm, respectively, and the lengths of the four extended necks 4 of the third working area 1 are 10mm, 10.5mm, 11mm, and 11.5mm, and so on. The side length of the central through hole 2 is 65mm*65mm, and the side length of the working area 1 is 145mm*145mm.

[0033] The multi-layer overlapping working area 1 of the present invention can be made by 3D printing. A sample is prepared according to the size of the above preferred embodiment and the sample is placed in the middle of the BK acoustic wave tube. Figure 3 As shown in the figure, the reflection transmission coefficient is measured using the four-microphone method and the sound absorption coefficient is calculated. The measurement results are compared with the results of COMSOL simulation, as shown in Figures 4 to 6 From the noise reduction schematic diagram shown, it can be seen that the measurement results are consistent with the results of COMSOL simulation, which proves that the ultra-wideband noise reduction effect of the present invention is significant.

[0034] Add a fan at the right end of the BK sonic tube, such as Figure 7 As shown, the fan is running to make the air flow in the BK sonic tube, and the reflection transmission coefficient is measured again using the four-microphone method and the sound absorption coefficient is calculated. The results are compared with the measurement results when the fan is not set, and it is found that the absorption efficiency and noise reduction effect are unchanged. It can be concluded that the present invention can be used in an environment full of fluids, which provides the possibility for future applications in more fluid fields.

[0035] In order to verify the situation of heat convection, a heater is set at the right end of the BK sonic tube to simulate the heat flow experiment in the pipeline. The temperatures of three locations, position 1, position 2 and position 3, in the BK sonic tube are selected for comparison and then tested:

[0036] 1. If Figure 8 As shown, no sample is placed in the BK sonic tube. After the heater runs for 5 minutes, the thermal imaging of the surface of the BK sonic tube is as follows: Fig. 9 As shown, the measured temperatures at positions 1, 2, and 3 are 53.6°C, 35.6°C, and 44.6°C, respectively;

[0037] 2. If Fig.10 As shown, a sample is placed at the thermometer 2. After the heater runs for 5 minutes, the thermal imaging of the BK sonic tube surface is as follows: Fig.11 As shown, the measured temperatures at positions 1, 2, and 3 are 51.8°C, 45.6°C, and 44.6°C, respectively;

[0038] 3. If Fig.12 As shown, a general noise reduction foam is placed at the thermometer 2. After the heater runs for 5 minutes, the thermal imaging of the BK sonic tube surface is as follows: Fig.13 As shown, the measured temperatures at position 1, position 2, and position 3 are 42.8°C, 32.5°C, and 23.7°C, respectively.

[0039] It can be seen that ordinary noise reduction foam has almost no heat conduction effect, while placing the sample does not affect heat convection. This paves the way for more complex life scenarios and industrial needs, such as noise reduction in heat conduction of warm air pipes, heat dissipation and noise reduction in large industries, etc.

[0040] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A thermal convection noise reduction device based on an embedded neck type, characterized in that: The invention comprises a plurality of overlapping working areas (1) and a central through hole (2) penetrating the plurality of working areas (1) from the center of the working areas (1). Each layer of the working areas (1) is provided with a plurality of Helmholtz resonant cavities (3) of the same size. The number of the Helmholtz resonant cavities (3) in each layer of the working areas (1) is the same. The inner wall of each Helmholtz resonant cavity (3) is provided with an extended neck (4) connecting the Helmholtz resonant cavity (3) and the central through hole (2). The sequence composed of the length values ​​of the plurality of extended necks (4) in the bottom layer of the working area (1) is an arithmetic progression, and the length of the extended neck (4) in the upper layer of the working area (1) is equal to the length of the extended neck (4) in the lower layer plus d, where d is a positive number or a negative number.

2. The heat convection noise reduction device based on the embedded neck type according to claim 1 is characterized in that: The working area (1) is rectangular, the central through hole (2) is a rectangular hole, and each layer of the working area (1) is provided with four trapezoidal Helmholtz resonant cavities (3).

3. The heat convection noise reduction device based on the embedded neck type according to claim 1 or 2, characterized in that: The thickness of each layer of the working area (1) is 10 mm.

4. The heat convection noise reduction device based on the embedded neck type according to claim 1 or 2, characterized in that: The working area (1) has 5 floors.

5. The heat convection noise reduction device based on the embedded neck type according to claim 4 is characterized in that: The width of all the extension necks (4) is 6 mm, the minimum length of the extension neck (4) of the bottommost working area (1) is 5 mm, and d is 2.5 mm.

6. The heat convection noise reduction device based on the embedded neck type according to claim 2 is characterized in that: The side length of the central through hole (2) is 65 mm*65 mm, and the side length of the working area (1) is 145 mm*145 mm.

7. The heat convection noise reduction device based on the embedded neck type according to claim 1 is characterized in that: The extended neck (4) is spiral-shaped.

8. The heat convection noise reduction device based on the embedded neck type according to claim 1 is characterized in that: The multi-layer overlapping workspace (1) is produced by 3D printing.

Images