Multi-frequency bending-torsion coupling vortex-induced vibration energy collection device based on piezoelectric effect

Abstract

The invention is suitable for the technical field of fluid power generation, and provides a piezoelectric effect-based multi-frequency bending-torsion coupling vortex-induced vibration energy acquisition device, which comprises a cantilever beam, a piezoelectric plate, a bluff body and a beam end connecting block, one end of the cantilever beam is a fixed end used for being fixed to a supporting body, the other end of the cantilever beam is a free end, the piezoelectric plate is connected to the cantilever beam and located between the fixed end and the free end, the free end is connected with the beam end connecting block, and the upper end of the bluff body is connected to the lower end of the beam end connecting block. And the extension direction of the bluff body is perpendicular to the extension direction of the cantilever beam. According to the device, the extension direction of the bluff body is perpendicular to the extension direction of the cantilever beam, so that the overall shape is L-shaped, the device can obtain two frequency lock intervals in adjacent flow velocity ranges, the width and the number of energy harvesting frequency bands are increased, and the energy harvesting efficiency is improved. The problems that a vortex-induced vibration energy collecting device based on a linear resonance mode is generally single in working frequency band, narrow and the like are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of fluid power generation, and in particular relates to a multi-frequency bending-torsion coupling vortex-induced vibration energy harvesting device based on piezoelectric effect. Background Art

[0002] The traditional paddle-type hydroelectric generator drives the blades to rotate through the impact of water flow. The rotating blades are connected to the traditional electromagnetic generator through the gear shaft, and the mechanical energy is converted into electrical energy through electromagnetic induction. It can continuously output energy for fluids with higher flow rates, but it is large in size, complex in structure, requires a certain starting flow rate, and cannot collect energy contained in low-flow fluids. Although the existing linear vibration mode vortex-induced vibration energy harvesting device is small in size and can resonate with the vortex detached from the fluid at a very low flow rate to collect energy, it only has a high energy output in the frequency lock range, and only has a single frequency lock range, and the energy capture frequency band is single and narrow. Summary of the invention

[0003] The purpose of an embodiment of the present invention is to provide a multi-frequency bending-torsion coupled vortex-induced vibration energy harvesting device based on piezoelectric effect, aiming to solve the problem that the linear vibration mode vortex-induced vibration energy harvesting device in the prior art has only a single frequency locking interval and a single and narrow energy capture frequency band.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions: A multi-frequency bending-torsion coupled vortex-induced vibration energy harvesting device based on piezoelectric effect, comprising a cantilever beam, a piezoelectric sheet, a bluff body and a beam end connecting block; one end of the cantilever beam is a fixed end for fixing on a support body, the other end of the cantilever beam is a free end, the piezoelectric sheet is connected to the cantilever beam and is located between the fixed end and the free end, the free end is connected to the beam end connecting block, the upper end of the bluff body is connected to the lower end of the beam end connecting block, and the extension direction of the bluff body is perpendicular to the extension direction of the cantilever beam.

[0005] Furthermore, the beam end connecting blocks are connected to opposite sides of the free end.

[0006] Furthermore, the cross section of the bluff body is circular, rectangular or triangular.

[0007] Furthermore, the bluff body has a concentrated mass block.

[0008] Furthermore, the bluff body has a containing cavity therein, and the concentrated mass block is installed at the bottom of the containing cavity.

[0009] Furthermore, the material of the bluff body is acrylic.

[0010] Furthermore, a beam end mass block is connected to a side of each beam end connecting block facing away from the free end.

[0011] Furthermore, the beam end mass blocks are symmetrically arranged with respect to the cantilever beam, and the beam end connecting blocks are also symmetrically arranged with respect to the cantilever beam.

[0012] Furthermore, the cantilever beam is a long steel sheet.

[0013] Furthermore, the piezoelectric sheet is bonded to the surface of the cantilever beam, and the piezoelectric sheet is a piezoelectric ceramic.

[0014] Compared with the prior art, the embodiments of the present invention have the following beneficial effects: the multi-frequency bending-torsion coupled vortex-induced vibration energy harvesting device based on piezoelectric effect provided by the present invention fixes the fixed end of the cantilever beam, connects the free end of the cantilever beam to the upper end of the blunt body through the beam end connecting block, and makes the extension direction of the blunt body and the extension direction of the cantilever beam perpendicular to each other, so that the overall shape is "L" shaped, so that the device can obtain two frequency locking intervals within the adjacent flow velocity range, broadens the width and number of energy capture frequency bands, and solves the problems of single and narrow working frequency bands commonly existing in vortex-induced vibration energy harvesting devices based on linear resonance modes. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the three-dimensional structure of a multi-frequency bending-torsion coupled vortex-induced vibration energy harvesting device provided by an embodiment of the present invention; Figure 2 yes Figure 1 A side structural schematic diagram of a multi-frequency bending-torsion coupled vortex-induced vibration energy harvesting device shown; Figure 3 yes Figure 2 A schematic diagram of the top view of the multi-frequency bending-torsion coupled vortex-induced vibration energy harvesting device shown; Figure 4 yes Figure 1 The main structural schematic diagram of the multi-frequency bending-torsion coupled vortex-induced vibration energy harvesting device shown; Figure 5 yes Figure 1 The vibration principle diagram of the multi-frequency bending-torsion coupled vortex-induced vibration energy harvesting device shown; Figure 6 It is an amplitude-frequency response diagram of a nonlinear vibration system based on bending-torsion coupling of a multi-frequency bending-torsion coupled vortex-induced vibration energy harvesting device based on piezoelectric effect of the present invention.

[0016] The reference numerals in the figures are: 1. Blunt body; 11. Accommodating cavity; 2. Concentrated mass block; 3. Beam end mass block; 4. Beam end connecting block; 5. Cantilever beam; 51. Fixed end; 52. Free end; 6. Piezoelectric sheet. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0018] In the description of the present invention, it should be noted that if the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the accompanying drawings, or is the orientation or position relationship in which the product of the invention is usually placed when used. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0019] like Figures 1 to 5 As shown, an embodiment of the present invention provides a multi-frequency bending-torsion coupled vortex-induced vibration energy harvesting device based on piezoelectric effect. The multi-frequency bending-torsion coupled vortex-induced vibration energy harvesting device comprises a cantilever beam 5, a piezoelectric sheet 6, a blunt body 1 and a beam end connection block 4; one end of the cantilever beam 5 is a fixed end 51 for fixing on a support body, and the other end of the cantilever beam 5 is a free end 52, the piezoelectric sheet 6 is connected to the cantilever beam 5, and the piezoelectric sheet 6 is located between the fixed end 51 and the free end 52 of the cantilever beam 5, specifically, the cantilever beam 5 is an elastic flat long strip, and the piezoelectric sheet 6 is attached to the surface of the flat long strip. The free end 52 of the cantilever beam 5 is connected to a beam end connection block 4, and the beam end connection block 4 can balance the forces on both sides of the cantilever beam 5. The upper end of the bluff body 1 is connected to the middle position of the lower end of the beam end connection block 4, and the lower end of the bluff body 1 is used to be immersed in a fluid (such as a water flow). The extension direction of the bluff body 1 is perpendicular to the extension direction of the cantilever beam 5, so that after the cantilever beam 5 is connected to the bluff body 1 through the beam end connection block 4, the cantilever beam 5 and the bluff body 1 form an "L"-shaped structure. The cantilever beam 5 and the bluff body 1 have different materials, lengths and cross-sections, so that the multi-frequency bending-torsion coupled vortex-induced vibration energy harvesting device has two adjacent natural frequencies in the low-frequency range, so that it can obtain two adjacent resonant frequencies, so as to obtain adjacent energy capture frequency bands in the fluid, such as Figure 6 shown.

[0020] As an implementation method, see Figure 3 and Figure 4 As shown, two opposite sides of the free end 52 of the cantilever beam 5 are connected with beam end connecting blocks 4, and the two beam end connecting blocks 4 are symmetrically arranged with respect to the free end 52 of the cantilever beam 5. The upper end of the bluff body 1 is connected to the lower ends of the two beam end connecting blocks 4, so that the free end 52 of the cantilever beam 5 is located in the middle position directly above the bluff body 1.

[0021] In this embodiment, the cross-section of the bluff body 1 is circular. In order to make the device suitable for fluids with different flow rates, a bluff body 1 with a rectangular or triangular cross-section may also be used. The change in shape only affects the position of the energy capture frequency band of the device in the fluid, and does not change the overall technical effect.

[0022] As an implementation mode, the material of the bluff body 1 is acrylic, which has the characteristics of being light, easy to process, impact-resistant, and having strong chemical stability.

[0023] As an implementation method, see Figure 2 As shown, the bluff body 1 is provided with a concentrated mass block 2 for counterweighting the bluff body 1. The concentrated mass block 2 is arranged at the lower end of the bluff body 1. Specifically, the bluff body 1 is provided with a receiving cavity 11, and the concentrated mass block 2 is installed at the bottom of the receiving cavity 11. In this embodiment, a lower cover is threadedly connected to the lower end of the bluff body 1, and a sealing ring is arranged between the lower cover and the lower end of the bluff body 1. After removing the lower cover, the concentrated mass block 2 can be placed in the receiving cavity 11, and the lower cover is threadedly locked to the lower end of the bluff body, so that the receiving cavity 11 is closed, and then the concentrated mass block 2 with different masses can be replaced according to actual conditions.

[0024] As an implementation method, a beam end mass block 3 is connected to the side of each beam end connecting block 4 facing away from the free end 52 of the cantilever beam 5, and the beam end mass blocks 3 are also symmetrically arranged with respect to the cantilever beam 5, so that the cantilever beam 5 is subjected to balanced forces on the left and right sides in the bending vibration direction.

[0025] As an implementation method, see Figure 3 As shown, the cantilever beam 5 is a long steel sheet with good elasticity and low cost. The piezoelectric sheet 6 can be bonded to the surface of the cantilever beam 5 by glue, and the piezoelectric sheet 6 is preferably piezoelectric ceramic.

[0026] The working principle of the multi-frequency bending-torsion coupling vortex-induced vibration energy harvesting device based on piezoelectric effect provided by the present invention is as follows: The fixed end 51 of the cantilever beam 5 is fixed on the support, so that the cantilever beam 5 is placed horizontally, and the bluff body 1 is in a vertical direction perpendicular to the horizontal direction (such as Figure 2 As shown in FIG. 1 ), the lower end of the bluff body 1 with the concentrated mass block 2 is immersed in the water flow, and the incoming direction of the water flow is the extension direction of the cantilever beam 5 (as shown in FIG. Figure 1 As shown in the figure, when the vortex shedding frequency is close to the first-order torsional vibration natural frequency of the cantilever beam 5, the bluff body 1 swings around the cantilever beam 5, and the cantilever beam 5 resonates with the shedding vortex at the first-order torsional vibration natural frequency, driving the piezoelectric sheet 6 to produce geometric deformation, and the piezoelectric sheet 6 generates electric charge, which is output through an external circuit, converting the mechanical energy of the device into electrical energy.

[0027] When the vortex shedding frequency is close to the first-order bending vibration natural frequency of the cantilever beam 5, the bluff body 1 and the beam end mass block 3 will vibrate back and forth (such as Figure 5 As shown in the figure, the cantilever beam 5 resonates with the shedding vortex at the natural frequency of the first-order bending vibration, driving the piezoelectric sheet 6 to produce geometric deformation. The piezoelectric sheet 6 generates electric charge, which is output through an external circuit, converting the mechanical energy of the device into electrical energy.

[0028] Figure 6 This is a graph showing the relationship between the vortex shedding frequency and the system vibration amplitude at different water flow rates. Since the device has two adjacent natural frequencies in the low-frequency range, it can obtain two adjacent high-amplitude frequency-locked intervals in the water flow, and convert high-amplitude mechanical energy into electrical energy through the piezoelectric effect, namely two adjacent energy-capturing intervals, which broadens and increases the width, number and voltage amplitude of the energy-capturing frequency band, greatly improving the energy-capturing efficiency of the energy-capturing system. The device can be placed in rivers, oceans, ditches and other locations with fluid flow, complex conditions and no existing stable energy supply, to provide energy for micro-electromechanical systems and sensors, and can also be used to detect flow field states.

[0029] In summary, the multi-frequency bending-torsion coupled vortex-induced vibration energy harvesting device based on piezoelectric effect provided by the present invention has the following advantages: (1) The problem of traditional blade-type hydraulic generators being large in size, complex in structure and difficult to miniaturize has been solved. The device has a simple structure, compact size, and is easy to miniaturize. It can also power micro-electromechanical systems and sensors, collect electrical energy from low-flow fluids, and does not generate any form of noise or pollution during operation, making it environmentally friendly and safe.

[0030] (2) After the cantilever beam 5 is connected to the bluff body 1 through the beam end connecting block 4, the cantilever beam 5 and the bluff body 1 form an "L"-shaped structure, and thus the device forms an "L"-shaped structure. Due to the "L"-shaped structure, the interval between the two natural frequencies of bending and torsion of the cantilever beam 5 can be very small, so that the device can obtain two frequency locking intervals within the adjacent flow velocity range, broadening the width and number of energy capture frequency bands, and solving the problems of single and narrow working frequency bands commonly existing in vortex-induced vibration energy harvesting devices based on linear resonance modes; (3) Since the cantilever beam 5 has both bending and torsional vibration modes, its vibration is nonlinear and its amplitude-frequency response curve deviates to one side, thereby broadening the width of the energy capture frequency band to a greater extent, broadening the resonance range of the structure, and improving the energy capture efficiency.

[0031] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A multi-frequency bending-torsion coupled vortex-induced vibration energy harvesting device based on piezoelectric effect, characterized in that: It includes a cantilever beam, a piezoelectric sheet, a bluff body and a beam end connecting block; one end of the cantilever beam is a fixed end for fixing on a support body, the other end of the cantilever beam is a free end, the piezoelectric sheet is connected to the cantilever beam and is located between the fixed end and the free end, the free end is connected to the beam end connecting block, the upper end of the bluff body is connected to the lower end of the beam end connecting block, and the extension direction of the bluff body is perpendicular to the extension direction of the cantilever beam.

2. The multi-frequency bending-torsion coupled vortex-induced vibration energy harvesting device based on piezoelectric effect according to claim 1 is characterized in that: The beam end connecting blocks are connected to opposite sides of the free end.

3. The multi-frequency bending-torsion coupled vortex-induced vibration energy harvesting device based on piezoelectric effect according to claim 1 is characterized in that: The cross section of the bluff body is circular, rectangular or triangular.

4. The multi-frequency bending-torsion coupled vortex-induced vibration energy harvesting device based on piezoelectric effect according to claim 1 or 3, characterized in that: The bluff body is provided with a concentrated mass block.

5. The multi-frequency bending-torsion coupled vortex-induced vibration energy harvesting device based on piezoelectric effect according to claim 4 is characterized in that: The bluff body has a receiving cavity therein, and the concentrated mass block is installed at the bottom of the receiving cavity.

6. The multi-frequency bending-torsion coupled vortex-induced vibration energy harvesting device based on piezoelectric effect according to claim 4 is characterized in that: The material of the bluff body is acrylic.

7. The multi-frequency bending-torsion coupled vortex-induced vibration energy harvesting device based on piezoelectric effect according to claim 2 is characterized in that: A beam end mass block is connected to a side of each beam end connecting block facing away from the free end.

8. The multi-frequency bending-torsion coupled vortex-induced vibration energy harvesting device based on piezoelectric effect according to claim 7 is characterized in that: The beam end mass blocks are symmetrically arranged with respect to the cantilever beam, and the beam end connecting blocks are also symmetrically arranged with respect to the cantilever beam.

9. The multi-frequency bending-torsion coupled vortex-induced vibration energy harvesting device based on piezoelectric effect according to claim 1 is characterized in that: The cantilever beam is a long steel sheet.

10. The multi-frequency bending-torsion coupled vortex-induced vibration energy harvesting device based on piezoelectric effect according to claim 1 or 9, characterized in that: The piezoelectric sheet is bonded to the surface of the cantilever beam, and the piezoelectric sheet is piezoelectric ceramic.

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