Multidirectional wind energy collector

Abstract

The invention discloses a multidirectional wind energy collector, and relates to the field of wind energy collectors, and the multidirectional wind energy collector comprises a first cantilever beam and a second cantilever beam; the end parts of the first cantilever beam and the second cantilever beam abut against each other, and the surfaces of the first cantilever beam and the second cantilever beam are coated with piezoelectric patches; the vibration direction of the first cantilever beam in the thickness direction is perpendicular to the vibration direction of the second cantilever beam in the thickness direction. According to the multidirectional wind energy collector, the defect that a single-beam collector is single in response wind direction is overcome through the orthogonal double-beam structure, and the maximum output power and the effective working wind speed range of the wind energy collector are remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of wind energy collectors, in particular to a multi-directional wind energy collector. Background Art

[0002] A single piezoelectric beam wind energy collector is a device that uses piezoelectric materials to convert wind energy into electrical energy. It is usually composed of one or more piezoelectric beams, which deform under the action of wind to generate electrical energy. The structure of a single piezoelectric beam sensor is relatively simple, easy to manufacture and maintain, and is usually made of lightweight materials to reduce its own weight and increase its response to wind force. However, the single piezoelectric beam responds better to crosswind (perpendicular to the direction of the beam), but responds weakly to tailwind (along the length of the beam), which limits its efficiency under variable wind direction conditions. Therefore, the collector based on a single piezoelectric beam mainly vibrates in response to crosswind, and the output of the tailwind response is small, but the wind in the natural environment may come from all directions, and the single beam collector in the prior art cannot fully utilize wind energy. Summary of the invention

[0003] In view of the above problems existing in the prior art, the present invention is proposed.

[0004] Therefore, the problem to be solved by the present invention is how to improve the multi-directional wind energy collection capability of the wind energy collector.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: a multi-directional wind energy collector, comprising a first cantilever beam and a second cantilever beam; the ends of the first cantilever beam and the second cantilever beam are abutted and the surfaces of both are covered with piezoelectric sheets; the vibration direction of the first cantilever beam along its thickness is perpendicular to the vibration direction of the second cantilever beam along its thickness.

[0006] As a preferred solution of the multi-directional wind energy collector of the present invention, the first cantilever beam is rectangular in shape, the second cantilever beam is trapezoidal in shape, and the narrow sides of the first cantilever beam and the second cantilever beam are in contact with each other.

[0007] As a preferred solution of the multi-directional wind energy collector of the present invention, the first cantilever beam and the second cantilever beam are both trapezoidal in shape, and the wide side of the first cantilever beam abuts against the narrow side of the second cantilever beam.

[0008] As a preferred solution of the multi-directional wind energy collector of the present invention, the first cantilever beam and the second cantilever beam are both trapezoidal in shape, and the narrow side of the first cantilever beam abuts against the narrow side of the second cantilever beam.

[0009] As a preferred solution of the multi-directional wind energy collector of the present invention, the length of the first cantilever beam is 60 mm and the width is 20 mm.

[0010] As a preferred solution of the multi-directional wind energy collector of the present invention, a bluff body is fixedly arranged at one end of the first cantilever beam away from the second cantilever beam.

[0011] As a preferred solution of the multi-directional wind energy collector of the present invention, the bluff body is in the shape of a hollow cylinder and is made of nylon.

[0012] As a preferred solution of the multi-directional wind energy collector of the present invention, the first cantilever beam and the second cantilever beam are made of phosphor bronze, and the piezoelectric sheet is made of lead zirconate titanate.

[0013] As a preferred solution of the multi-directional wind energy collector of the present invention, a first clamp and a second clamp are provided at one end of the second cantilever beam away from the first cantilever beam, the second cantilever beam is fixed on the first clamp, and the first clamp can rotate on the second clamp.

[0014] As a preferred solution of the multi-directional wind energy collector of the present invention, a protractor is fixedly arranged on the top of the second clamp, the protractor is in a circular ring shape, and the first clamp is arranged in the circular ring of the protractor.

[0015] The beneficial effects of the present invention are as follows: the multi-directional wind energy collector proposed by the present invention overcomes the shortcoming of a single-beam collector that responds to a single wind direction through an orthogonal double-beam structure, and significantly improves the maximum output power and effective working wind speed range of the wind energy collector. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0017] Figure 1 This is a schematic diagram of the structure of the multi-directional wind energy collector described in Example 1.

[0018] Figure 2 This is a schematic diagram of the structure of the multi-directional wind energy collector described in Example 2.

[0019] Figure 3 This is a schematic diagram of the structure of the multi-directional wind energy collector described in Example 3.

[0020] Figure 4 It is a top view of the first cantilever beam and the second cantilever beam of the wind energy collector and a schematic diagram of the wind direction angle.

[0021] Figure 5 This is a graph showing the relationship between the output voltage of the first cantilever beam and the second cantilever beam of each type of collector and the wind speed at 90 degrees.

[0022] Figure 6 This is a graph showing the relationship between the total output power of each type of collector and wind speed at 90 degrees.

[0023] Figure 7 This is a first-order vibration mode simulation diagram of the wind energy collector described in Example 1.

[0024] Figure 8 This is a simulation diagram of the second-order vibration mode of the wind energy collector described in Example 1.

[0025] Fig. 9 This is a simulation diagram of the third-order vibration mode of the wind energy collector described in Example 1.

[0026] Fig.10 This is a simulation diagram of the fourth-order vibration mode of the wind energy collector described in Example 1.

[0027] Fig.11 This is a response curve diagram of the output voltage and output power of the wind energy collector described in Example 1 as a function of frequency.

[0028] Fig.12 This is a curve diagram showing the relationship between the output voltage and power of the wind energy collector described in Example 1 and the change in load resistance.

[0029] Fig.13 The relationship curve of the output voltage and power of the wind energy collector described in Example 1 with the acceleration

[0030] Fig.14 This is a graph showing the relationship between the RMS voltage and power output by the first cantilever beam of the collector described in Example 1 and the load resistance when the wind speed is 7 m / s.

[0031] Fig.15 This is a graph showing the relationship between the RMS voltage and power output by the second cantilever beam of the collector described in Example 1 and the load resistance when the wind speed is 7 m / s.

[0032] Fig.16 This is a waveform diagram of the output voltage of the first cantilever beam described in Example 1 at different wind speeds when the wind direction is 90 degrees.

[0033] Fig.17 The waveform diagram of the output voltage of the second cantilever beam described in Example 1 at different wind speeds when the wind direction is 90 degrees.

[0034] Fig.18 This is a vibration frequency characteristic diagram of the first cantilever beam described in Example 1 when the wind direction is 0 degrees.

[0035] Fig.19 This is a vibration frequency characteristic diagram of the first cantilever beam described in Example 1 when the wind direction is 90 degrees.

[0036] Fig. 20 This is a vibration frequency characteristic diagram of the second cantilever beam described in Example 1 when the wind direction is 0 degrees.

[0037] Fig.21 This is a vibration frequency characteristic diagram of the second cantilever beam described in Example 1 when the wind direction is 90 degrees.

[0038] Fig. 22 This is a graph showing the relationship between the output voltage of the first cantilever beam of the collector described in Example 1 and the wind speed under different wind directions.

[0039] Fig.23 This is a graph showing the relationship between the output voltage of the second cantilever beam of the collector described in Example 1 and the wind speed under different wind directions.

[0040] Fig.24 This is a graph showing the relationship between the output power of the first cantilever beam of the collector described in Example 1 and wind speed under different wind directions.

[0041] Fig.25 This is a graph showing the relationship between the output power of the second cantilever beam of the collector described in Example 1 and wind speed under different wind directions.

[0042] Fig.26 This is a graph showing the relationship between the total power of the collector described in Example 1 and wind speed under different wind directions.

[0043] Fig. 27 The graph is a graph showing the relationship between the total output power of the collector described in Example 1 and wind direction when the wind speed is 8 m / s. DETAILED DESCRIPTION

[0044] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0045] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0046] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it an embodiment that is mutually exclusive with other embodiments, either individually or selectively.

[0047] Example 1

[0048] Reference Figure 1 , which is the first embodiment of the present invention, provides a multi-directional wind energy collector, which includes a first cantilever beam 100 and a second cantilever beam 200.

[0049] Preferably, the first cantilever beam 100 is a rectangular sheet made of phosphor bronze with a length of 60 mm, a width of 20 mm and a thickness of 0.2 mm.

[0050] The second cantilever beam 200 is a thin sheet in a trapezoidal shape, and its material is also phosphor bronze. In this embodiment, the second cantilever beam 200 is in an isosceles trapezoidal shape, and the narrow side of its top is orthogonally connected to the bottom of the first cantilever beam 100, that is, the vibration direction of the first cantilever beam 100 along its thickness is perpendicular to the vibration direction of the second cantilever beam 200 along its thickness.

[0051] The surfaces of the first cantilever beam 100 and the second cantilever beam 200 are both covered with a piezoelectric sheet 300, which is a piezoelectric ceramic made of lead zirconate titanate (specifically PZT52 in this embodiment). The piezoelectric sheet 300 is rectangular in shape and polarized along its thickness direction. The piezoelectric sheet 300 is a flip electrode, that is, the positive electrode and the negative electrode are both located on the same side of the piezoelectric sheet 300, the long side is the positive electrode, and the short side is the negative electrode, which is convenient for welding wires.

[0052] Furthermore, a bluff body 400 is fixed on the top of the first cantilever beam 100. In this embodiment, the bluff body 400 is a cylinder with a diameter of 400 mm and a height of 100 mm and is hollow inside. It is made of lightweight black nylon material, which can effectively reduce the starting wind speed of the wind energy collector.

[0053] Furthermore, a first clamp 500 is also provided at the bottom of the second cantilever beam 200, and the first clamp 500 can fix the second cantilever beam 200 and the first cantilever beam 100 and the bluff body 400 on the first clamp 500 by bolts or screws. On the other hand, the first clamp 500 is fixed on the second clamp 600, and the second clamp 500 is two metal blocks. When the two metal blocks are loosened, the first clamp 500 can be rotated thereon, and when the two metal blocks are rotated to a specified angle, the two metal blocks are clamped again. Correspondingly, a protractor 700 is also provided on the top surface of the second clamp 600, and the protractor 700 is a 360° full-circle protractor, which can help the wind energy collector adjust the accurate windward angle.

[0054] Example 2

[0055] Reference Figure 2, which is the second embodiment of the present invention, and this embodiment is based on the previous embodiment. Different from the embodiment 1, in this embodiment, the first cantilever beam 100 and the second cantilever beam 200 are both trapezoidal in shape, and the first cantilever beam 100 is narrow at the top and wide at the bottom, and the second cantilever beam 200 is also narrow at the top and wide at the bottom.

[0056] At the same time, the wide side at the bottom of the first cantilever beam 100 is orthogonally connected to the narrow side at the top of the second cantilever beam 200 .

[0057] The rest of the structure is the same as that of Example 1.

[0058] Example 3

[0059] Reference Figure 3 , which is the third embodiment of the present invention, and this embodiment is based on embodiment 1. Different from embodiment 1, in this embodiment, the first cantilever beam 100 and the second cantilever beam 200 are both trapezoidal in shape, and the first cantilever beam 100 is wide at the top and narrow at the bottom, while the second cantilever beam 200 is narrow at the top and wide at the bottom.

[0060] At the same time, the narrow side at the bottom of the first cantilever beam 100 is orthogonally connected to the narrow side at the top of the second cantilever beam 200 .

[0061] The rest of the structure is the same as that of Example 1.

[0062] Example 4

[0063] Reference Figure 4 , which is the fourth embodiment of the present invention. This embodiment provides a preferred technical solution for the wind energy collector described in the present invention and proves its beneficial effects through simulation tests and experiments.

[0064] Firstly, based on Example 1, Example 2 and Example 3, wind tunnel experiments are conducted on the wind energy collector structures proposed in these three implementation modes to select the optimal technical solution.

[0065] Before the test, the wind direction angle θ needs to be determined. Figure 4 As shown, the x direction and the y direction are the downwind direction and the crosswind direction respectively, and the wind direction angle θ is defined as the angle between the x direction and the v direction. The collector can be regarded as a two-degree-of-freedom system, one degree of freedom is the lateral vibration of the first cantilever beam 100 along the u direction, and the other degree of freedom is the lateral vibration of the second cantilever beam 200 along the v direction.

[0066] Then, when the wind direction angle θ is 90 degrees and the wind speed range is 2 to 8 m / s, wind tunnel experiments are carried out on the three wind energy collectors. The output power and the relationship between power and wind speed are shown as follows: Figure 5 and Figure 6 shown.

[0067] Specifically, from Figure 5It can be seen that the output voltages of the first cantilever beam 100 and the second cantilever beam 200 of the wind energy collector in Example 1 are both the highest, and the peak voltages of the first cantilever beam 100 and the second cantilever beam 200 both reach 3.5V at a wind speed of 8m / s.

[0068] Compared with the wind energy collector in Example 1, the output voltage of the first cantilever beam 100 of the wind energy collector in Example 2 is significantly reduced. When the wind speed is 8 m / s, the peak voltage is only 0.76 V, which is 78.3% lower than that in Example 1.

[0069] Compared with the wind energy collector in Example 1, the output voltage of the second cantilever beam 200 of the wind energy collector in Example 3 is significantly reduced. When the wind speed is 8 m / s, the peak voltage is only 1.43 V, which is 59.1% lower than that in Example 1.

[0070] from Figure 6 It can be seen that the total output power of the collector of Example 1 has significant advantages over that of Example 2 and Example 3, and the peak power reaches 82 μW when the wind speed is 8 m / s.

[0071] The peak power of the solution of Example 2 at a wind speed of 8 m / s is only 31.52 μW, which is 61.6% less than that of the solution of Example 1.

[0072] The peak power of the solution of Example 3 at a wind speed of 8 m / s is only 31.66 μW, which is 61.4% less than that of the solution of Example 1.

[0073] It can be seen from the experimental results that when the technical solution of Example 1 is adopted, the collector output performance is optimal, so the preferred solution of the wind energy collector of the present invention is the technical solution of Example 1.

[0074] After selecting the technical solution of Example 1, a simulation analysis is performed on it. Specifically, the vibration characteristics of the wind energy collector based on Example 1 and the output performance of the piezoelectric sheet 300 are studied using COMSOL Multiphysics finite element analysis software. Add multi-physics field-piezoelectric effect and circuit interface, and establish a three-dimensional model of the collector in the geometric interface. The model size is consistent with the size recorded in the example. The radius of the blunt body 400 is 20mm and the length is 100mm; the size of the first cantilever beam 100 is 20×60×0.2mm 3 The second cantilever beam 200 has an upper bottom width of 20 mm, a lower bottom width of 40 mm, and a thickness of 0.2 mm; the size of the piezoelectric sheet 300 is 20×40×0.2 mm 3 The material parameter settings of each part of the collector are shown in Table 1:

[0075] Table 1 Material parameters of each component of the collector

[0076] part <![CDATA[Density (kg / m 3 )]]> Young's modulus(GPa) Poisson's ratio Piezoelectric Ceramics 7750 80 0.32 Phosphor Bronze 8920 106 0.35 Cylindrical Blunt Body 300 105 0.4

[0077] The coupled multiphysics settings are as follows:

[0078] Solid mechanics physics field: the bluff body 400, the first cantilever beam 100 and the second cantilever beam 200 are all made of linear elastic materials, the piezoelectric sheet 300 is a piezoelectric material, and the isotropic loss factor is selected as the damping type, which is defined as 0.001; a fixed constraint is applied to the bottom surface of the second cantilever beam 200, and a boundary load of 0.001N is applied to the 1 / 4 side surface of the bluff body 400, which is equivalent to wind force, and the direction is along the diagonal direction of the x-axis and the z-axis.

[0079] Electrostatic physical field: The piezoelectric sheet 300 is polarized along the thickness direction, the outer surface is a positive electrode, which is set as a terminal, and the inner surface is a negative electrode, which is set as a ground, satisfying the charge conservation condition.

[0080] Circuit Physics: Add a load resistor directly at the piezoelectric 300 ground node and terminal voltage.

[0081] Based on the above, after obtaining the simulation results, the first aspect is to analyze the frequency domain characteristics of the collector. Specifically, the characteristic frequency of the collector is studied to obtain the first four vibration modes of the collector. Figure 7 to Figure 10 When the first cantilever beam 100 is bending and vibrating along the z direction, the corresponding collector has the first-order natural frequency of 2.651 Hz; when the second cantilever beam 200 is bending and vibrating along the x direction, the corresponding collector has the second-order natural frequency of 2.910 Hz; when the first cantilever beam 100 and the second cantilever beam 200 are torsionally vibrating in the xz plane, the corresponding collector has the third-order natural frequency of 17.116 Hz; when the first cantilever beam 100 and the second cantilever beam 200 are torsionally vibrating in the yz plane, the corresponding collector has the fourth-order natural frequency of 29.087 Hz. It can be seen from the surface displacement distribution diagram that when the collector is in the first-order motion state ( Figure 7 ), the top displacement of the blunt body is the largest, and the corresponding collector output performance is the best; followed by the fourth-order motion state ( Fig.10 ), but the structure is easily damaged at this time; when the collector is in the second-order motion state ( Figure 8 ), the displacement of the blunt body tip is minimal.

[0082] The collector described in Example 1 was studied in the frequency domain, with a scanning frequency range of 0 to 25 Hz and a load resistance of 1 MΩ. The response curves of the collector output voltage and output power with frequency were obtained as shown in FIG. Fig.11As shown in the figure, the voltage and power curves both reach the first peak at a frequency of 3 Hz and the second peak at a frequency of 17 Hz, which correspond to the first three natural frequencies of the collector, indicating that the maximum output can be obtained when the vibration frequency of the collector is close to the natural frequency.

[0083] Secondly, the relationship between the output and resistance of the collector is studied. Specifically, the resonant frequency is set to 2.651Hz, and the parameter scanning range of the load resistance is set to 1kΩ to 100MΩ. Based on the relationship curve of the output voltage and power of the wind energy collector as a function of the load resistance described in Example 1, Fig.12 As shown in the figure, it can be seen that the output voltage of the piezoelectric sheet 300 increases with the increase of the load resistance at first. When the load resistance increases to a certain extent, the output voltage no longer changes. The output power increases first and then decreases with the increase of the load resistance. When the load resistance is around 0.8MΩ, the output power reaches a peak value. This provides ideas for the measurement of the optimal matching impedance in the subsequent wind tunnel experiment.

[0084] Thirdly, the relationship between the collector output and wind force is analyzed. Specifically, in the frequency domain study, the load resistance is set to 0.8MΩ, the operating frequency is 2.651Hz, a body load of solid.rho*g_const*acc is applied to the blunt body 400, the direction is along the positive direction of the x-axis, and the parameter scanning range of the acceleration acc is set to range(0,0.25,5), and the relationship curve between the collector output voltage and power and the acceleration is obtained as follows: Fig.13 As shown in the figure, it can be seen that the output voltage increases linearly with the increase of acceleration, and the output power increases in a quadratic parabola with the increase of acceleration. This shows that the greater the acceleration, that is, the greater the wind excitation, the better the output performance of the collector.

[0085] Based on the above simulation analysis results, the wind energy collector described in Example 1 is experimented and compared with the simulation test results to verify the authenticity of the effect of the technical solution provided by the present invention.

[0086] First, in the first aspect, the relationship between the output voltage and power of the wind energy collector and the load is studied through experiments. Specifically, in order to improve the wind energy collection capability of the collector, the wind speed of the wind tunnel is adjusted to 7m / s, and the first cantilever beam 100 and the second cantilever beam 200 of the wind energy collector are adjusted to their maximum power output state, that is, the wind direction angles are 90° and 15° to carry out impedance matching experiments. The load resistor is connected to the positive and negative electrodes of the piezoelectric sheet 300 through a wire, and the load resistance value is continuously adjusted until the output power of the load resistor reaches a peak value. The output RMS voltage and power of the first cantilever beam 100 and the second cantilever beam 200 of the wind energy collector vary with the load resistance as shown in the following table. Fig.14 and Fig.15As shown in the figure, when the load resistance increases to a certain extent, the output RMS voltage of the first cantilever beam 100 and the second cantilever beam 200 no longer continues to increase with the increase of the load resistance, and the output power of the first cantilever beam 100 and the second cantilever beam 200 both reach the peak power of 29.21μW and 25.76μW when the load resistance is 0.3MΩ, that is, the optimal matching impedance of the first cantilever beam 100 and the second cantilever beam 200 are both 0.3MΩ.

[0087] Secondly, the voltage waveform of the collector is studied through experiments. Specifically, in order to study the output voltage characteristics of the collector under different wind speeds and wind directions, the waveform fragment of the collector output voltage signal after stabilization for 30 seconds is intercepted. Fig.16 and Fig.17 The output voltage waveforms of the first cantilever beam 100 and the second cantilever beam 200 at wind speeds of 5m / s, 6m / s, 7m / s and 8m / s are shown in the figure. As can be seen from the figure, the output voltage waveform shows a certain periodicity. This is because the piezoelectric sheet 300 vibrates periodically. When the vibration amplitude of the piezoelectric sheet 300 deviates the farthest from the equilibrium position, the peak voltage is output. When the piezoelectric sheet 300 slowly returns to the equilibrium position, the output voltage signal gradually decays. As the wind speed increases from 5m / s to 8m / s, the Vp-p of the first cantilever beam 100 at 90° wind direction increases from 14.9V to 23.8V, and the Vp-p of the second cantilever beam 200 at 90° wind direction increases from 14V to 25V.

[0088] After filtering out the 50 Hz power frequency noise with a notch filter, the output voltage waveform is processed by fast Fourier transform (FFT). When the wind speed is 8 m / s, the amplitude-frequency characteristic curves of the first cantilever beam 100 and the second cantilever beam 200 are as follows: Figure 18 to Figure 21 As shown. Due to the symmetry of the cross-coupled double beam structure, the vibrations in the u direction and the v direction are independent of each other. When the wind direction is 90°, the vibration frequency of the first cantilever beam 100 is 2.88 Hz, which corresponds to the lateral vibration of the first cantilever beam 100 along the u direction, which is close to the first-order natural frequency of the collector obtained by simulation, 2.651 Hz ( Figure 7 ); When the wind direction is 0°, the vibration frequency of the second cantilever beam 200 is 2.46 Hz, which corresponds to the lateral vibration of the second cantilever beam 200 along the v direction, which is close to the second-order natural frequency of the collector obtained by simulation, 2.910 Hz ( Figure 8 ). It may be because the collector does not vibrate completely regularly in the chaotic wind, so there is a certain deviation between the simulation results and the experimental results, but the error is within the allowable range.

[0089] Thirdly, the output performance of the collector is studied through experiments. The output voltage and output power of the collector are greatly affected by the wind speed. Under low wind speed excitation, the collector is affected by the pressure difference caused by the fluid movement on both sides of the bluff body 400, deviating from the equilibrium position and swinging periodically to both sides; the higher the wind speed, the more violent the wind-induced vibration effect, the faster the vortex shedding speed, the greater the vibration amplitude of the first cantilever beam 100 and the second cantilever beam 200, the greater the stress on the piezoelectric sheet 300, the more significant the piezoelectric effect, and the higher the output voltage and power.

[0090] Fourthly, the relationship between the output voltage of the collector and the wind speed is studied experimentally. Specifically, the first cantilever beam 100 and the second cantilever beam 200 of the wind energy collector can generate electricity at the same time. In order to study the response ability of the two to winds of different speeds and directions, a wind tunnel test is conducted in the wind speed range of 2 to 8 m / s with a step length of 0.5 m / s. The experimental data are organized as follows Fig. 22 and Fig.23 shown.

[0091] from Fig. 22 It can be seen that when the wind direction is 90°, that is, when the first cantilever beam 100 is parallel to the incident wind direction, its output voltage is the highest overall; when the wind direction is 0°, that is, when the first cantilever beam 100 is perpendicular to the incident wind direction, its output voltage is the lowest overall. This is because when the wind flows through the cylindrical bluff body 400, periodic alternating vortices will appear on both sides of the leeward side of the bluff body 400, and the vortices will generate periodic pressure perpendicular to the wind direction on both sides of the bluff body 400, forcing the bluff body 400 supported by the elastic beam to vibrate in a direction perpendicular to the wind direction, that is, when the wind direction is 0°, the collector mainly bends and vibrates along the y direction. At this time, the first cantilever beam 100 can be regarded as an extension of the bluff body 400, vibrating in the y direction like a rigid body, and moving synchronously with the bluff body 400. Therefore, when the wind direction is 0°, the piezoelectric sheet 300 attached to the first cantilever beam 100 is subjected to very small mechanical stress and strain, and the output voltage is small.

[0092] In the low wind speed range (2-3.5m / s), the output voltage is the highest when the wind direction is 45°, and the output voltage is 0.61V at a wind speed of 2m / s. When the wind directions are 45°, 60°, 75° and 90°, the output voltage of the first cantilever beam 100 increases first and then decreases in the wind speed range of 3-5.5m / s. This is because the vortex shedding frequency increases with the increase of wind speed. When the vortex shedding frequency is close to a certain order of natural frequency of the collector, the collector works in a resonant state, and the bluff body 400 will experience severe vortex-induced vibration and begin to vibrate greatly. As the wind speed increases further, the vortex shedding frequency gradually deviates from the natural frequency of the collector, and the vibration amplitude of the bluff body 400 decreases. This aerodynamic phenomenon is called the frequency locking effect, and the wind speed range where this phenomenon occurs is called the locking vibration region. The locking vibration area of ​​the first cantilever beam 100 at a wind direction of 45° is 3-4 m / s, the locking vibration area of ​​the first cantilever beam 100 at a wind direction of 60° and 75° is 3-5 m / s, and the locking vibration area of ​​the first cantilever beam 100 at a wind direction of 90° is 4.5-5.5 m / s, wherein the Vrms peak value can reach 2.31 V when the wind speed is 4.5 m / s and the wind direction is 60°. Therefore, the vortex-induced vibration phenomenon can reduce the critical wind speed and expand the effective working wind speed range.

[0093] In the higher wind speed range (5.5-8m / s), the output voltage of the first cantilever beam 100 is positively correlated with the wind speed. This is because when the wind speed is high enough to exceed the vibration locking area, the collector deviates from the equilibrium position and bends to one side. The higher the wind speed, the greater the vibration amplitude. When the wind speed is 8m / s, the output voltage of the 90° wind direction is the highest, reaching 3.5V, followed by 3.38V at 75° wind direction, and the lowest output voltage at 0° wind direction is only 2.44V.

[0094] from Fig.23 It can be seen that within the wind speed range of 5 to 8 m / s, when the wind direction is 0°, that is, when the second cantilever beam 200 is parallel to the incident wind direction, its output voltage is the highest overall. This is because when the wind direction is 0°, the second cantilever beam 200 mainly vibrates in the crosswind direction. At this time, the second cantilever beam 200 can be regarded as an extension of the fixed end, with large bending stiffness, large mechanical stress and strain, and high output voltage. When the wind speed is 8 m / s and the wind direction is 0°, the Vrms peak value of the second cantilever beam 200 is 3.75V, which is greater than the Vrms peak value of the first cantilever beam 100 of 3.5V. As the wind direction changes from 0°, 15°, 30°, 45°, 60° to 75°, the output voltage peak value decreases successively, and when the wind direction is 75°, the Vrms is only 2.92V. This is because as the wind direction shifts, the vibration amplitude of the second cantilever beam 200 in the crosswind direction becomes smaller and smaller.

[0095] In the low to medium wind speed range (2-5m / s), the output voltage is the highest when the wind direction is 90°, and the output voltage increases first and then decreases, from 0.75V when the wind speed is 2m / s to 1.89V when the wind speed is 4.5m / s, and then decreases to 1.48V when the wind speed is 4.5m / s, and the output voltage is the lowest when the wind direction is 75°. This is because the cylindrical bluff body 400 has a violent vortex-induced vibration phenomenon in the wind speed range of 2 to 5m / s, and the first cantilever beam 100 has a large bending vibration in the crosswind direction, which causes the second cantilever beam 200 to vibrate together.

[0096] In the fifth aspect, the relationship between the collector output power and wind speed is studied through experiments. Specifically, in order to study the multi-directional wind energy collection performance of the collector, the output power of the first cantilever beam 100 and the second cantilever beam 200 at different wind speeds and wind directions is as follows: Fig.24 and 25 As shown, the total power is Fig.26 shown.

[0097] from Fig.24 It can be seen that when the wind directions are 45°, 60°, 75° and 90°, there is a small peak in the output power curve of the first cantilever beam 100. This is because the cylindrical blunt body 400 undergoes vortex-induced vibration. After that, the collector mainly works in a turbulent state, and the output power increases with the increase of wind speed. When the wind speed is 8m / s and the wind direction is 90°, the first cantilever beam 100 obtains a maximum power of 40.83μW. When the wind direction is 0°, the first cantilever beam 100 obtains a minimum power of 19.85μW, which is less than 50% of the maximum power. It can be seen that there is a huge difference in the output performance of crosswind vibration and downwind vibration.

[0098] from Fig.25It can be seen that when the wind direction is 90°, there is a small peak in the output power curve of the second cantilever beam 200, and the peak power reaches 11.95μW at a wind speed of 4.5m / s. The output power of the second cantilever beam 200 is relatively uniform under all wind directions. Since the bending deformation of the second cantilever beam 200 is greater, the overall output voltage of the second cantilever beam 200 is higher than that of the upper piezoelectric beam. When the wind direction is 90°, the output performance of the second cantilever beam 200 is excellent in the low wind speed range (2 to 4.5m / s), and the output power reaches 11.95μW when the wind speed is 4.5m / s. In the wind speed range of 5.5 to 8m / s, the higher the wind speed, the higher the output power of the second cantilever beam 200 in each wind direction. When the wind speed is 8m / s, the output power of the second cantilever beam 200 in each wind direction reaches a peak value, and decreases in the order of 0°, 15°, 90°, 30°, 45°, 60°, and 75°, and the corresponding output powers are 46.88μW, 44.90μW, 41.16μW, 38.76μW, 33.92μW, 31.01μW, and 28.42μW, respectively. When the wind direction is 0°, that is, when the second cantilever beam 200 is parallel to the wind direction, the maximum output power of 46.88μW is obtained, which is higher than the maximum output power of 40.83μW of the first cantilever beam 100.

[0099] Depend on Fig.26 It can be seen that the wind energy collection performance is significantly improved from the unidirectional wind energy collector to the multidirectional wind energy collector. When the wind direction is 60°, the collector resonates at a wind speed of 4.5m / s, and a small peak (23.65μW) appears on the power output curve. After that, the power output curve continues to rise with the wind speed, reaching a peak of 56.55μW at a wind speed of 8m / s. In the wind speed range of 5-8m / s, the output power is very close when the wind direction is 0°, 15° and 75°, and the output power curves almost overlap, and the peak power is around 66. When the wind direction is 45°, the peak power is only 70% of the wind direction of 90°, which is 55.87μW. This may be because when θ=45°, the wind direction is inclined relative to the cross beam, and the lateral response of the first cantilever beam 100 and the second cantilever beam 200 is relatively weak. When the wind direction is 90°, the total output power of the collector is the highest. When the wind speed is 8m / s, the collector reaches a maximum output power of 81.99μW, which is twice the output power of a single piezoelectric beam (the maximum output power of the first cantilever beam is 40.83μW, and the maximum output power of the second cantilever beam 200 is 46.88μW). The locking vibration area is also widened to 3.5-5.5m / s (the locking vibration area of ​​the first cantilever beam 100 is 4.5-5.5m / s, and the locking vibration area of ​​the second cantilever beam 200 is 3.5-5m / s). This shows that the cross-coupled dual-beam structure collector proposed in this paper significantly improves the maximum output power and effective working wind speed range compared to the traditional single-beam energy harvester, and has better performance in natural wind environment.

[0100] In the sixth aspect, the multi-directional analysis of the bluff body 400 is carried out through experiments. Specifically, in order to verify the multi-directional wind energy collection characteristics of the collector based on the cross-coupled double-beam structure, a curve showing the relationship between the output power of the collector and the wind direction when the wind speed is 8m / s is drawn according to the symmetry. Fig. 27 As shown. It can be seen from the figure that the total output power of the collector is relatively uniform under different wind directions. The output power reaches a higher level when the wind direction is 90°±15°, and reaches a lower level when the wind direction is 45°±15°. The maximum power is 1.5 times the minimum power. Therefore, it is of great significance to study the influence of wind direction angle on the power output of the collector. When the wind direction is 75°, the total output power of the collector can reach 80% of the maximum output power. When the wind direction is 0°, the output power of the second cantilever beam 200 is the highest but the output power of the first cantilever beam 100 is the lowest, so the total output power is not high. When the wind direction is 90°, the output powers of the first cantilever beam 100 and the second cantilever beam 200 are both at a higher level, so the total output power is the highest.

[0101] The above experiments prove that the output power of the multi-wind direction wind energy collector proposed by the present invention is always higher than the output power of the collector based on the trapezoidal single beam, indicating that the cross-coupled double-beam structure greatly improves the output performance of the collector and the output is more uniform in all wind directions. It also shows that the cross-coupled double-beam structure has better reliability and robustness, which greatly improves the efficiency and application range of piezoelectric wind energy collectors in natural wind environments.

[0102] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A multi-directional wind energy collector, Features: include, A first cantilever beam (100) and a second cantilever beam (200); The ends of the first cantilever beam (100) and the second cantilever beam (200) are in contact with each other, and the surfaces of both cantilever beams are covered with a piezoelectric sheet (300); The vibration direction of the first cantilever beam (100) along its thickness is perpendicular to the vibration direction of the second cantilever beam (200) along its thickness.

2. The multi-directional wind energy collector according to claim 1, Features: The first cantilever beam (100) is in a rectangular shape, the second cantilever beam (200) is in a trapezoidal shape, and the narrow sides of the first cantilever beam (100) and the second cantilever beam (200) are in contact with each other.

3. The multi-directional wind energy collector according to claim 1, Features: The first cantilever beam (100) and the second cantilever beam (200) are both trapezoidal in shape, and the wide side of the first cantilever beam (100) abuts against the narrow side of the second cantilever beam (200).

4. The multi-directional wind energy collector according to claim 1, Features: The first cantilever beam (100) and the second cantilever beam (200) are both trapezoidal in shape, and the narrow side of the first cantilever beam (100) abuts against the narrow side of the second cantilever beam (200).

5. The multi-directional wind energy collector according to claim 1, Features: The first cantilever beam (100) has a length of 60 mm and a width of 20 mm.

6. The multi-directional wind energy collector according to claim 1, Features: A bluff body (400) is fixedly arranged at one end of the first cantilever beam (100) away from the second cantilever beam (200).

7. The multi-directional wind energy collector according to claim 6, Features: The bluff body (400) is in the shape of a hollow cylinder and is made of nylon.

8. The multi-directional wind energy collector according to claim 1, Features: The material of the first cantilever beam (100) and the second cantilever beam (200) is phosphor bronze, and the material of the piezoelectric sheet (300) is lead zirconate titanate.

9. The multi-directional wind energy collector according to claim 1, Features: A first clamp (500) and a second clamp (600) are provided at one end of the second cantilever beam (200) away from the first cantilever beam (100); the second cantilever beam (200) is fixed on the first clamp (500); and the first clamp (500) can rotate on the second clamp (600).

10. The multi-directional wind energy collector according to claim 9, Features: A protractor (700) is also fixedly arranged on the top of the second clamp (600); the protractor (700) is in the shape of a circular ring, and the first clamp (500) is arranged inside the circular ring of the protractor (700).

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