A multi-frequency bending-torsion coupled vortex-induced vibration energy harvesting device based on the piezoelectric effect

Abstract

The present invention is applicable to the field of fluid power generation technology, and provides a multi-frequency bending-torsion coupling vortex-induced vibration energy harvesting device based on the piezoelectric effect, which includes a cantilever beam, a piezoelectric sheet, a bluff body and a beam end connection block; one end of the cantilever beam is a fixed end for fixing on a support body, and 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 connection block. The upper end of the bluff body is connected to the lower end of the beam end connection block, and the extending direction of the bluff body is perpendicular to the extending direction of the cantilever beam. By making the extending direction of the bluff body perpendicular to the extending direction of the cantilever beam, the overall shape of the device is in an "L" shape, so that the device can obtain two frequency locking intervals within the adjacent flow velocity range, broadening the width and number of the energy harvesting frequency bands, and solving the problems commonly existing in the vortex-induced vibration energy harvesting devices based on the linear resonance mode, such as single and narrow working frequency bands.

Description

Technical Field

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

[0002] Traditional blade-type hydraulic generators drive the blades to rotate through the impact of water flow. The rotating blades are connected to a traditional electromagnetic generator through a gear shaft, and mechanical energy is converted into electrical energy through electromagnetic induction. For fluids with relatively high flow rates, energy can be continuously output. However, its volume is large, the structure is relatively complex, and a certain starting flow rate is required, and the energy contained in low-flow-rate fluids cannot be collected. Although the existing linear vibration mode vortex-induced vibration energy harvesting devices are small in volume and can resonate with the vortices shed in the fluid at very low flow rates to collect energy, they only have a high energy output in the frequency-locking interval and only have a single frequency-locking interval, with a single and narrow energy capture frequency band. Summary of the Invention

[0003] The purpose of the embodiments of the present invention is to provide a multi-frequency bending-torsion coupling vortex-induced vibration energy harvesting device based on the piezoelectric effect, aiming to solve the problem that the existing linear vibration mode vortex-induced vibration energy harvesting devices only have a single frequency-locking interval, with a single and narrow energy capture frequency band.

[0004] To solve the above technical problems, the present invention adopts the following technical solutions:

[0005] A multi-frequency bending-torsion coupling vortex-induced vibration energy harvesting device based on the piezoelectric effect, comprising a cantilever beam, a piezoelectric sheet, a bluff body, and a beam end connection 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 connection block, the upper end of the bluff body is connected to the lower end of the beam end connection block, and the extending direction of the bluff body is perpendicular to the extending direction of the cantilever beam.

[0006] Further, the beam end connection blocks are connected to both opposite sides of the free end.

[0007] Further, the cross-section of the bluff body is circular, rectangular, or triangular.

[0008] Further, the bluff body is provided with a concentrated mass block.

[0009] Further, the bluff body has a receiving cavity, and the concentrated mass block is installed at the bottom of the receiving cavity.

[0010] Further, the material of the bluff body is acrylic.

[0011] Furthermore, a beam end mass block is connected to one side of each of the beam end connection blocks facing away from the free end.

[0012] Furthermore, the beam end mass blocks are symmetrically arranged with respect to the cantilever beam, and the beam end connection blocks are also symmetrically arranged with respect to the cantilever beam.

[0013] Furthermore, the cantilever beam is a long strip-shaped steel sheet.

[0014] Furthermore, the piezoelectric sheet is bonded to the surface of the cantilever beam, and the piezoelectric sheet is a piezoelectric ceramic.

[0015] Compared with the prior art, the beneficial effects of the embodiment of the present invention are as follows: The multi-frequency bending-torsion coupling vortex-induced vibration energy harvesting device based on the 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 bluff body through the beam end connection block, and makes the extending direction of the bluff body perpendicular to the extending direction of the cantilever beam, so that the overall shape is in an "L" shape, enabling the device to obtain two frequency-locked intervals within a neighboring flow velocity range, broadening the width and number of the energy harvesting frequency bands, and solving the problems such as the single and narrow working frequency band commonly existing in the vortex-induced vibration energy harvesting devices based on the linear resonance mode. Description of the Drawings

[0016] Figure 1 is a three-dimensional structural schematic diagram of the multi-frequency bending-torsion coupling vortex-induced vibration energy harvesting device provided by the embodiment of the present invention;

[0017] Figure 2 is Figure 1 the side view structural schematic diagram of the multi-frequency bending-torsion coupling vortex-induced vibration energy harvesting device shown in

[0018] Figure 3 is Figure 2 the top view structural schematic diagram of the multi-frequency bending-torsion coupling vortex-induced vibration energy harvesting device shown in

[0019] Figure 4 is Figure 1 the front view structural schematic diagram of the multi-frequency bending-torsion coupling vortex-induced vibration energy harvesting device shown in

[0020] Figure 5 is Figure 1 the vibration principle diagram of the multi-frequency bending-torsion coupling vortex-induced vibration energy harvesting device shown in

[0021] Figure 6 is the amplitude-frequency response diagram of the nonlinear vibration system based on the bending-torsion coupling of a multi-frequency bending-torsion coupling vortex-induced vibration energy harvesting device of the present invention.

[0022] The reference numerals in the drawings are as follows:

[0023] 1. Blunt body; 11. Accommodation cavity; 2. Concentrated mass block; 3. Beam-end mass block; 4. Beam-end connection block; 5. Cantilever beam; 51. Fixed end; 52. Free end; 6. Piezoelectric sheet. Detailed implementation manners

[0024] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to 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 used to limit the present invention.

[0025] In the description of the present invention, it should be noted that if terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are used to indicate the orientation or positional relationship, it is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the present invention is usually placed during use. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0026] As Figures 1 to 5 shown, an embodiment of the present invention provides a multi-frequency bending-torsion coupling vortex-induced vibration energy harvesting device based on the piezoelectric effect. The multi-frequency bending-torsion coupling vortex-induced vibration energy harvesting device includes 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, 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. A beam-end connection block 4 is connected to the free end 52 of the cantilever beam 5. The beam-end connection block 4 can balance the forces on both sides of the cantilever beam 5. The upper end of the blunt body 1 is connected to the middle position of the lower end of the beam-end connection block 4. The lower end of the blunt body 1 is used to be immersed in a fluid (such as water flow). The extending direction of the blunt body 1 is perpendicular to the extending direction of the cantilever beam 5. After the cantilever beam 5 is connected to the blunt body 1 through the beam-end connection block 4, the cantilever beam 5 and the blunt body 1 form an "L" shaped structure. The materials, lengths, and cross-sections of the cantilever beam 5 and the blunt body 1 are different, so that the multi-frequency bending-torsion coupling vortex-induced vibration energy harvesting device has two adjacent natural frequencies in the low-frequency range, so that it can obtain two adjacent resonance frequencies, so as to obtain adjacent energy harvesting frequency bands in the fluid, as Figure 6 shown.

[0027] As an implementation manner, refer to Figure 3 and Figure 4As shown, beam end connection blocks 4 are connected to both opposite sides of the free end 52 of the cantilever beam 5. The two beam end connection 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 connection blocks 4, such that the free end 52 of the cantilever beam 5 is located at the middle position directly above the bluff body 1.

[0028] In this embodiment, the cross-section of the bluff body 1 is circular. In order to make the device applicable to fluids with different flow rates, a bluff body 1 with a cross-section such as a rectangle or a triangle can 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.

[0029] As an implementation manner, the material of the bluff body 1 is acrylic, which has characteristics such as light weight, easy processing, impact resistance, and strong chemical stability.

[0030] As an implementation manner, refer to Figure 2 As shown, the bluff body 1 has a concentrated mass block 2 for weighting the bluff body 1. The concentrated mass block 2 is arranged at the lower end inside the bluff body 1. Specifically, the bluff body 1 has 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 provided 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 into the receiving cavity 11 and the lower cover is threadedly locked to the lower end of the bluff body 1 to seal the receiving cavity 11, and then the concentrated mass block 2 with different masses can be replaced according to the actual situation.

[0031] As an implementation manner, a beam end mass block 3 is connected to the side of each beam end connection block 4 facing away from the free end 52 of the cantilever beam 5. The beam end mass blocks 3 are also symmetrically arranged with respect to the cantilever beam 5, such that the forces on the left and right sides of the cantilever beam 5 are balanced in the bending vibration direction.

[0032] As an implementation manner, refer to Figure 3 As shown, the cantilever beam 5 is a strip-shaped steel sheet, and the steel sheet has characteristics such as good elasticity and low cost. The piezoelectric sheet 6 can be bonded to the surface of the cantilever beam 5 with glue, and the piezoelectric sheet 6 is preferably a piezoelectric ceramic.

[0033] The working principle of the multi-frequency bending-torsion coupling vortex-induced vibration energy harvesting device based on the piezoelectric effect provided by the present invention is as follows:

[0034] Fix the fixed end 51 of the cantilever beam 5 to a support, place the cantilever beam 5 horizontally, and thus make the bluff body 1 in the vertical direction perpendicular to the horizontal direction (as Figure 2 shown), immerse the lower end of the bluff body 1 with the concentrated mass block 2 in the water flow, and the incoming flow direction of the water flow is the extending direction of the cantilever beam 5 (as Figure 1As shown in the figure, when the vortex shedding frequency is close to the natural frequency of the first-order torsional vibration of the cantilever beam 5, the bluff body 1 swings around the cantilever beam 5, and the cantilever beam 5 resonates with the shedding vortices at the natural frequency of the first-order torsional vibration, driving the piezoelectric sheet 6 to generate geometric deformation. The piezoelectric sheet 6 generates charges, and the electric quantity output is realized through an external circuit, converting the mechanical energy of the device into electrical energy.

[0035] When the vortex shedding frequency is close to the natural frequency of the first-order bending vibration of the cantilever beam 5, the bluff body 1 and the beam-end mass block 3 undergo reciprocating vibrations (as Figure 5 shown in the figure), and the cantilever beam 5 resonates with the shedding vortices at the natural frequency of the first-order bending vibration, driving the piezoelectric sheet 6 to generate geometric deformation. The piezoelectric sheet 6 generates charges, and the electric quantity output is realized through an external circuit, converting the mechanical energy of the device into electrical energy.

[0036] Figure 6 It is a relationship diagram of the corresponding vortex shedding frequency and the system vibration amplitude under different water flow velocities. Since the device has two adjacent natural frequencies in the low-frequency range, the device can obtain two adjacent high-amplitude frequency-locked intervals in the water flow. Through the piezoelectric effect, the high-amplitude mechanical energy is converted into electrical energy, that is, two adjacent energy harvesting intervals, broadening and increasing the width, number, and voltage amplitude of the energy harvesting frequency band, greatly improving the energy capture efficiency of the energy harvesting system. The device can be arranged in positions where there is fluid flow, such as rivers, oceans, and ditches, with complex conditions and no existing stable energy supply, to provide energy for microelectromechanical systems and sensors, and can also be used to detect the flow field state.

[0037] In summary, the multi-frequency bending-torsion coupling vortex-induced vibration energy harvesting device based on the piezoelectric effect provided by the present invention has the following advantages:

[0038] (1) It solves the problems of the traditional blade-type hydraulic generator, such as large volume, complex structure, and difficulty in miniaturization. The device has a simple structure, a compact volume, is easy to be miniaturized, and can supply power to microelectromechanical systems and sensors. It can collect electrical energy from low-flow-rate fluids and will not generate any form of noise or pollution during operation, being environmentally friendly and safe.

[0039] (2) 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, and thus the device forms an "L"-shaped structure. Due to this "L"-shaped structure, the intervals between the two natural frequencies of the bending and torsion of the cantilever beam 5 can be very small, enabling the device to obtain two frequency-locked intervals within adjacent flow velocity ranges, broadening the width and number of the energy harvesting frequency band, and solving the problems such as the single and narrow working frequency band commonly existing in the vortex-induced vibration energy harvesting devices based on the linear resonance mode;

[0040] (3) Since the cantilever beam 5 has two modes of bending and torsional vibration simultaneously, its vibration is non-linear, and its amplitude-frequency response curve will deviate to one side, which broadens the width of the energy harvesting frequency band to a greater extent, broadens the resonance interval of the structure, and improves the energy harvesting efficiency.

[0041] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A multi-frequency bending-torsion coupling vortex-induced vibration energy harvesting device based on the piezoelectric effect, characterized in that It includes a cantilever beam, a piezoelectric sheet, a blunt body and a beam end connection 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 connection block, the upper end of the blunt body is connected to the lower end of the beam end connection block, and the extending direction of the blunt body is perpendicular to the extending direction of the cantilever beam; The blunt body has a concentrated mass block, the blunt body has a receiving cavity, the concentrated mass block is installed at the bottom of the receiving cavity, and a lower cover is threadedly connected to the lower end of the blunt body; The beam end connection blocks are connected to both opposite sides of the free end, and a beam end mass block is connected to the side of each beam end connection block facing away from the free end.

2. The multi-frequency bending-torsion coupling vortex-induced vibration energy harvesting device based on the piezoelectric effect according to claim 1, wherein The cross section of the blunt body is circular, rectangular or triangular.

3. The multi-frequency bending-torsion coupling vortex-induced vibration energy harvesting device based on the piezoelectric effect according to claim 1, wherein The material of the blunt body is acrylic.

4. The multi-frequency bending-torsion coupled vortex-induced vibration energy harvesting device based on the piezoelectric effect according to claim 1, wherein The beam end mass blocks are symmetrically arranged with respect to the cantilever beam, and the beam end connection blocks are also symmetrically arranged with respect to the cantilever beam.

5. The multi-frequency bending-torsion coupled vortex-induced vibration energy harvesting device based on the piezoelectric effect according to claim 1, characterized in that The cantilever beam is a strip-shaped steel sheet.

6. The multi-frequency bending-torsion coupling vortex-induced vibration energy harvesting device based on the piezoelectric effect according to claim 1 or 5, characterized in that, The piezoelectric sheet is bonded to the surface of the cantilever beam, and the piezoelectric sheet is a piezoelectric ceramic.

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