Piezoelectric synthesis jet device based on combined cavity

Abstract

In order to improve the energy conversion efficiency and the output performance, the piezoelectric synthesis jet device based on the combined cavity comprises a base body, a cavity, a nozzle and a piezoelectric vibrator, and a pump cavity is formed in a pump body; the piezoelectric vibrator is arranged in the pump cavity and divides the pump cavity into two cavities; a through hole is formed in the position, with the maximum amplitude, of the piezoelectric vibrator; the pump body is provided with a nozzle at the coaxial position of the through hole; the height, close to the nozzle, of the two cavities is larger than that of the other cavity; the hole diameter of the nozzle is larger than that of the through hole. The device has the characteristics and advantages of low power consumption, high energy density, high jet velocity of the nozzle, small size and easiness in integration.

Description

Technical Field

[0001] The present invention belongs to the field of synthetic jet injectors, and particularly relates to a piezoelectric synthetic jet injector based on a combined cavity. Background Art

[0002] As an important device in the field of active fluid control, the synthetic jet injector realizes the active control of the flow field based on the synthetic jet principle. Its main structure includes an elastic diaphragm, a cavity and a nozzle (as Figure 6 shown). The synthetic jet injector drives the volume of the cavity to change periodically through the vibration of the elastic diaphragm. Combining with the synthetic jet principle, a jet is obtained at the nozzle. According to different driving methods of the elastic diaphragm vibration, the synthetic jet injector can be divided into piezoelectric, electrostatic or electromagnetic types, etc. It is applicable to occasions such as heat dissipation of portable electronic devices and gas supply of micro-systems. The synthetic jet injector is applicable to occasions such as heat dissipation of portable electronic devices and gas supply of micro-systems. In recent years, the synthetic jet injector has been used as an active fluid control device to increase the aerodynamic efficiency of machines, such as the surface of an aircraft.

[0003] Referring to Figure 6 , Chinese Patent CN100548504C discloses a manufacturing method of a piezoelectric synthetic jet injector, which processes a cavity (2), a nozzle (5), a vibrating diaphragm (3) and a piezoelectric diaphragm (4) on the same silicon substrate, improving the reliability and consistency of the synthetic jet injector. Chinese Patent CN108298065B discloses a piezoelectric synthetic jet injector. The synthetic jet injector has a housing defining a resonant chamber therein, and an orifice fluidly connects the resonant chamber to the ambient atmosphere. A thin film or diaphragm is capable of vibrating to change the volume of the resonant chamber, thereby inducing air to be alternately ejected and inhaled through the orifice. Currently, the piezoelectric synthetic jet injector mainly realizes gas jet through a single piezoelectric vibrator paired with a single chamber, and there is room for further improvement in its jet velocity and energy conversion efficiency. Summary of the Invention

[0004] In recent years, there has been a trend of low power consumption and small volume in integrated electronic devices. Therefore, a piezoelectric synthetic jet injector with high energy conversion efficiency (which can achieve low power consumption) and high jet velocity is urgently needed in the market. In order to further improve the jet velocity and energy conversion efficiency of the piezoelectric jet driver, the present invention proposes a piezoelectric synthetic jet injector based on a combined cavity.

[0005] In order to improve the energy conversion efficiency of the piezoelectric jet actuator, the present invention has the following structure, in which a first top plate, a first intermediate plate, a vibration diaphragm, a second intermediate plate, and a second top plate are stacked and connected in sequence from top to bottom; the first top plate, the first intermediate plate, and the vibration diaphragm form a first chamber; the second top plate, the second intermediate plate, and the vibration diaphragm form a second chamber; the first top plate, the first intermediate plate, the second intermediate plate, and the second top plate together form the base body of the piezoelectric synthetic jet actuator of the present invention; the first chamber and the second chamber together form the cavity of the piezoelectric synthetic jet actuator of the present invention, that is, the "combined chamber" in the present invention.

[0006] Further, a piezoelectric element is concentrically connected to the vibration diaphragm; as a driving source, the piezoelectric element drives the vibration diaphragm to vibrate under the drive of an alternating voltage signal; the piezoelectric element and the vibration diaphragm form a piezoelectric vibrator.

[0007] Further, the piezoelectric vibrator is provided with a through hole at the center, and the through hole communicates the first chamber and the second chamber.

[0008] Further, the first top plate is provided with a nozzle at a position coaxial with the through hole, and the nozzle is coaxial with the through hole; the nozzle communicates the first chamber and the external atmospheric environment.

[0009] Further, the height of the first chamber is greater than the height of the second chamber; the height of the second chamber is not less than 2 times the maximum amplitude of the piezoelectric vibrator (i.e., the amplitude at the maximum amplitude) during the working process.

[0010] Further, the aperture of the nozzle is not less than 3 times the aperture of the through hole.

[0011] In this structure, the vibration diaphragm is arranged in the cavity and divides the cavity into a first chamber and a second chamber. The piezoelectric vibrator communicates the first chamber and the second chamber through a through hole at the center. Under the drive of an alternating voltage signal in a certain frequency band (about 20 kHz), high-pressure acoustic regions will be alternately generated on both sides of the first chamber and the second chamber. This can effectively convert the energy of the piezoelectric vibrator into fluid kinetic energy. Under the action of the alternating high-pressure acoustic regions in the first chamber and the second chamber, a continuous jet will be obtained at the nozzle. Therefore, the energy conversion efficiency of the piezoelectric synthetic jet actuator and the fluid jet velocity at the nozzle will increase.

[0012] Preferably, the vibrating diaphragm is provided with structural holes arranged in a circumferential array. Through the structural holes arranged in a circumferential array, the vibrating diaphragm is divided into a middle part, a supporting part, and supporting beams; the middle part is concentrically connected to the piezoelectric element; the diameter of the middle part is not less than the outer diameter of the piezoelectric element; the supporting part is clamped by the first middle plate and the second middle plate to play a peripheral supporting role for the piezoelectric vibrator; there are eight supporting beams, and the supporting beams are distributed in a circumferential array. The eight supporting beams elastically support the central part and the piezoelectric element on the supporting part, which can well reduce the overall stiffness of the piezoelectric vibrator, and can effectively excite vibration and achieve high-amplitude output under low-voltage / high-frequency driving; by adding the supporting beams, the stiffness of the piezoelectric vibrator is greatly reduced, which can reduce the driving voltage of the piezoelectric vibrator (this is beneficial to the service life of the piezoelectric vibrator), and further enables the piezoelectric vibrator to work at low voltage and ultrasonic frequency.

[0013] Furthermore, an isolation layer is concentrically connected to the vibrating diaphragm on the side facing the first chamber; the isolation layer realizes the sealing isolation of the upper and lower ends of the vibrating diaphragm at the structural holes through a hermetic bond, which can provide subsequent sealing isolation of the first chamber and the second chamber at the structural holes.

[0014] Furthermore, the aperture of the nozzle is not less than 3 times the aperture of the through hole. In this embodiment, the aperture of the nozzle is 3 mm, and the aperture of the through hole is 1 mm; the ratio of the aperture of the through hole to the outer diameter of the piezoelectric element (diameter ratio) is about 18; the diameters of the first cavity and the second cavity are the same, and the diameters of both the first cavity and the second cavity are 21 mm. The ratio of the nozzle aperture to the diameter of the first chamber (diameter ratio) is about 21; the thickness ratio of the vibrating diaphragm and the piezoelectric element is about 2. In this embodiment, the thickness of the vibrating diaphragm is 0.2 mm, and the thickness of the piezoelectric element is 0.4 mm; the outer diameters and thicknesses of the piezoelectric element and the matching layer are equal, with a thickness of 0.4 mm and an outer diameter of 18 mm each.

[0015] Preferably, the materials of the first intermediate plate and the second intermediate plate can also be selected as silicone materials, which can further reduce the support stiffness of the piezoelectric vibrator, thereby increasing the vibration amplitude of the piezoelectric vibrator and enhancing the jet flow intensity. It should be noted here that when the materials of the first intermediate plate and the second intermediate plate are selected as silicone materials, within a certain vibration frequency range, the amplitudes of the first intermediate plate and the second intermediate plate can be superimposed when the piezoelectric vibrator vibrates, which can increase the vibration amplitude of the piezoelectric vibrator. However, since the materials of the first intermediate plate and the second intermediate plate are selected as silicone materials, their stiffness is greatly reduced, and it is necessary to increase the heights of the first chamber and the second chamber to prevent interference from occurring. At the same time, since the elasticity (i.e., stiffness) of the silicone material will change during long-term operation, a frequency tracking (tracking the optimal operating frequency function, generally tracking based on the current of the drive circuit) function needs to be added to the drive circuit of the piezoelectric vibrator.

[0016] Driven by an AC voltage signal at an ultrasonic frequency (about 20 - 21 kHz), the piezoelectric element drives the vibration diaphragm to bend and vibrate. The piezoelectric vibrator is in a second-order vibration mode. In the second-order vibration mode, the piezoelectric vibrator generates three amplitude maximum points, namely the center of the piezoelectric vibrator and its left and right sides, among which the amplitude at the center of the piezoelectric vibrator is the largest. During one vibration period, the working process can be divided into a first working state and a second working state, which will be described in detail below.

[0017] First working state: The amplitude maximum points on both sides of the piezoelectric vibrator vibrate downward, and the amplitude maximum point in the middle vibrates upward. The piezoelectric vibrator obtains the vibration mode of the first working state. Based on the principle of acoustic standing waves (the lower surface of the first top plate acts as a reflector), high-pressure acoustic regions are gathered near both sides of the center amplitude maximum point in the first chamber (it should be emphasized here that since there is a nozzle opening in the center of the first top plate and a through hole in the center of the piezoelectric vibrator, no sound waves are emitted from the center and there is no reflector, which will cause no high-pressure acoustic region to be generated in the center of the first chamber). Under the action of sound pressure, the gas on both sides of the first chamber flows towards the center. The fluid in the central region of the first chamber sprays outwards through the nozzle and flows towards the second chamber through the through hole. The fluid in the central region of the second chamber flows towards both sides and jets upwards through the through hole. Based on the principle of synthetic jet, jet flow is achieved at the center of the nozzle. It should be noted here that during the process of the fluid spraying outwards from the center of the nozzle, due to the viscous effect of the fluid, vortices will be generated around the wall surface of the nozzle. Under the action of the vortices and pressure, the fluid around the outer periphery of the nozzle side is driven to flow into the first chamber, that is, the fluid in the atmospheric environment flows along the periphery of the nozzle towards the first chamber.

[0018] Second working state: The maximum amplitude points on both sides of the piezoelectric vibrator vibrate upward, and the maximum amplitude point in the middle vibrates downward. The piezoelectric vibrator obtains the vibration mode of the second working state. Based on the principle of acoustic standing waves, high-pressure acoustic regions gather near both sides of the maximum amplitude point at the center of the second chamber (it should be emphasized here that since there is a through hole in the center of the piezoelectric vibrator and no sound waves are emitted from the center, this will cause no high-pressure acoustic region to be generated at the center of the second chamber). Under the action of sound pressure, the fluids on both sides of the second chamber flow towards the center and jet upward through the through hole. Part of the fluid jets outward through the nozzle, and part of the fluid flows towards both sides of the first chamber; during the process of the fluid jetting outward from the center of the nozzle, due to the viscous effect of the fluid, vortices will be generated around the wall surface of the nozzle. Under the action of the vortices and pressure, the fluid on the outer periphery of the nozzle side is driven into the first chamber, that is, the fluid in the atmospheric environment flows along the periphery of the nozzle towards the first chamber. It should be noted here that since the aperture of the nozzle is larger than that of the through hole, there is a flow resistance difference effect, and the fluid in the central region of the first chamber has a tendency to jet outward.

[0019] The features and advantages of this project are as follows: 1. Low power consumption and high energy conversion efficiency. Through the combined cavity structure, bilateral energy convergence of the piezoelectric vibrator is achieved, and the mechanical energy of the piezoelectric vibrator is efficiently converted into fluid kinetic energy; 2. High jet velocity. Through the combined cavity structure, the cumulative acceleration jet of gas is realized, and the jet velocity at the nozzle is high. Brief Description of the Drawings

[0020] Figure 1 is a schematic structural sectional view of a preferred embodiment; Figure 2 (A) and (B) are Figure 1 schematic working principle sectional views when the embodiment is driven in the sixth-order vibration mode, where Figure 2 (A) is the first working state within one driving period, Figure 2 (B) is the second working state within one driving period; Figure 3 is a brief top view sectional drawing of a preferred embodiment of the vibration diaphragm 3; Figure 4 is adopted Figure 3 a bottom view of a preferred embodiment of the piezoelectric vibrator 30 after implementing the vibration diaphragm 3 in Figure 5 is Figure 4 C-C sectional view schematic diagram of Figure 6 is a schematic structural diagram of a prior art piezoelectric synthetic jet; Wherein: 1 - matrix; 11 - first top plate; 12 - second top plate; 100 - first chamber; 110 - second chamber; 2 - cavity; 21 - first intermediate; 22 - second intermediate; 3 - vibration diaphragm; 30 - piezoelectric oscillator; 301 - first operating mode vibration mode; 302 - second operating mode vibration mode; 31 - middle part; 32 - support part; 33 - support beam; 34 - matching layer; 310 - through hole; 330 - structural hole; 4 - piezoelectric element; 5 - nozzle. Detailed implementation manners

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that the orientation or positional relationships indicated by the terms "middle", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the orientation or positional relationships shown in the accompanying drawings, and are 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. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0022] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0023] The following will describe in detail the specific implementation manners of the present invention with reference to the accompanying drawings. It should be understood that the specific implementation manners described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments.

[0025] Please refer to Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 、 Figure 6 , the present invention provides a piezoelectric synthetic jet actuator based on a combined cavity, as Figure 1As shown in the figure, a first top plate 11, a first middle plate 21, a piezoelectric vibrator 30, a second middle plate 22, and a second top plate 12 are connected in sequence from top to bottom; the first top plate 11, the first middle plate 21, and the piezoelectric vibrator 30 form a first chamber 100; the second top plate 12, the second middle plate 22, and the piezoelectric vibrator 30 form a second chamber 110; the first top plate 11, the first middle plate 21, the second middle plate 22, and the second top plate 12 together constitute the base body 1 of the piezoelectric synthetic jet injector of the present invention; the first chamber 100 and the second chamber 110 together constitute the cavity 2 of the piezoelectric synthetic jet injector of the present invention, that is, the "combined chamber" in the present invention.

[0026] Further, the first top plate 11 is in the shape of a circular flat plate, for example, made of resin; the first top plate 11 is connected to the upper surface of the first middle plate 21; the first top plate 11 forms the top of the first chamber 100.

[0027] Further, the first middle plate 21 is in the shape of a circular ring, for example, made of resin; the first middle plate 21 is connected to the upper surface of the periphery of the piezoelectric vibrator 30; the first chamber 100 is in the shape of a cylinder, and the diameter of the first chamber 100 is the inner diameter of the first middle plate 21.

[0028] Further, the piezoelectric vibrator 30 is composed of a vibrating diaphragm 3 and a piezoelectric element 4 connected concentrically; the vibrating diaphragm 3 is in the shape of a circular flat plate, for example, made of metal; as a driving source, the piezoelectric element 4 drives the vibrating diaphragm 3 to vibrate under the drive of an alternating voltage signal; the lower surface of the periphery of the vibrating diaphragm 3 is connected to the upper surface of the second middle plate 22; the upper surface of the periphery of the vibrating diaphragm 3 is connected to the lower surface of the first middle plate 21.

[0029] Further, the piezoelectric element 4 is in the shape of a circular flat plate, for example, made of lead zirconate titanate (PZT) ceramic; electrode layers are provided on both the upper and lower end faces of the piezoelectric element 4, and the electrode layers are, for example, made of silver; the piezoelectric element 4 is connected to the side of the vibrating diaphragm 3 facing the second chamber 110; the polarization direction of the piezoelectric element 3 is the vertical direction (the direction perpendicular to the electrode layer); the piezoelectric element 4 and the vibrating diaphragm 3 form the piezoelectric vibrator 30; the outer diameter of the piezoelectric element 4 is smaller than the outer diameter of the vibrating diaphragm 3.

[0030] Further, the second middle plate 22 is in the shape of a circular ring, for example, made of resin; the second middle plate 22 is connected to the upper surface of the second top plate 12; the second chamber 110 is in the shape of a cylinder, and the diameter of the second chamber 110 is the inner diameter of the second middle plate 22.

[0031] Further, the second top plate 12 is in the shape of a circular flat plate, for example, made of resin; the second top plate 12 forms the bottom of the second chamber 22.

[0032] Further, a through hole 310 is provided at the position where the amplitude of the piezoelectric vibrator 30 is the largest in the sixth-order mode (i.e., at the antinode of the sixth-order vibration mode of the piezoelectric vibrator 30, where the amplitude at the antinode is the largest). In this embodiment, the opening position of the through hole 310 is at the center of the piezoelectric vibrator 30; the through hole 310 communicates with the first chamber 100 and the second chamber 110.

[0033] Further, a nozzle 5 is provided at the position coaxial with the through hole 310 on the first top plate 11, that is, the nozzle 5 is coaxial with the through hole 310; the nozzle 5 communicates with the first chamber 100 and the external atmospheric environment.

[0034] Further, the height of the first chamber 100 is greater than the height of the second chamber 110; the height of the second chamber 110 is not less than 2 times the maximum amplitude (i.e., the amplitude at the antinode) of the piezoelectric vibrator 30 during operation.

[0035] Further, a matching layer 34 is concentrically connected to the side of the vibration diaphragm 3 facing the first chamber 100; the matching layer 34 is in the shape of a circular flat plate, for example, made of aluminum alloy. The addition of the matching layer 34 can enhance the energy conversion efficiency at the gas-solid interface junction; the outer diameter of the matching layer 34 is smaller than the outer diameter of the vibration diaphragm 3; the outer diameter and thickness of the matching layer 34 are equal to those of the piezoelectric element 4, which can balance the mass and sound energy emission levels at both ends of the vibration diaphragm 3 to a certain extent, thereby improving the vibration balance and energy conversion efficiency of the piezoelectric vibrator 30.

[0036] Preferably, as Figure 3 and Figure 4 shown, the vibration diaphragm 3 is provided with structural holes 330 arranged in a circumferential array. Through the structural holes 330 arranged in a circumferential array, the vibration diaphragm 3 is partitioned into a middle part 31, a support part 32, and support beams 33; the middle part 31 is concentrically connected to the piezoelectric element 4; the diameter of the middle part 31 is not less than the outer diameter of the piezoelectric element 4; the support part 32 is clamped by the first intermediate plate 21 and the second intermediate plate 22, playing a role in peripherally supporting the piezoelectric vibrator 30; there are eight support beams 33, and the support beams are distributed in a circumferential array. The eight support beams 31 elastically support the central part 31 and the piezoelectric element 4 on the support part 32, which can effectively reduce the overall stiffness of the piezoelectric vibrator 30, and can achieve effective excitation of vibration and high-amplitude output under low-voltage / high-frequency drive; by adding the support beams 31, the stiffness of the piezoelectric vibrator 30 is greatly reduced, which can reduce the driving voltage of the piezoelectric vibrator 30.

[0037] Further, an isolation layer 35 is concentrically connected to the side of the vibration diaphragm 3 facing the first chamber 100; the isolation layer 35 realizes the sealing isolation of the upper and lower ends of the vibration diaphragm 3 at the structural hole 330 through a hermetic bond, which can provide the subsequent sealing isolation of the first chamber 100 and the second chamber 110 at the structural hole 330.

[0038] Further, the aperture of the nozzle 5 is not less than 3 times the aperture of the through hole 310. In this embodiment, the aperture of the nozzle 5 is 3 mm, and the aperture of the through hole 310 is 1 mm; the ratio of the aperture of the through hole 310 to the outer diameter of the piezoelectric element 4 (diameter ratio) is about 18; the diameters of the first cavity 100 and the second cavity 110 are the same, and the diameters of both the first cavity 100 and the second cavity 110 are 21 mm. The ratio of the aperture of the nozzle 5 to the diameter of the first chamber 21 (diameter ratio) is about 21; the thickness ratio of the vibration diaphragm 3 and the piezoelectric element 4 is about 2. In this embodiment, the thickness of the vibration diaphragm 3 is 0.2 mm, and the thickness of the piezoelectric element 4 is 0.4 mm; the outer diameters and thicknesses of the piezoelectric element 4 and the matching layer 34 are equal, with a thickness of 0.4 mm and an outer diameter of 18 mm.

[0039] Preferably, the materials of the first intermediate plate 21 and the second intermediate plate 22 can also be selected as silicone materials, which can further reduce the support stiffness of the piezoelectric vibrator 30, thereby increasing the vibration amplitude of the piezoelectric vibrator 30 and enhancing the jet flow intensity. It should be noted here that when the materials of the first intermediate plate 21 and the second intermediate plate 22 are selected as silicone materials, within a certain vibration frequency range, the amplitudes of the first intermediate plate 21 and the second intermediate plate 22 can be superimposed when the piezoelectric vibrator 30 vibrates, which can increase the vibration amplitude of the piezoelectric vibrator 30. However, since the materials of the first intermediate plate 21 and the second intermediate plate 22 are selected as silicone materials, their stiffness is greatly reduced, and it is necessary to increase the heights of the first chamber 100 and the second chamber 110 to prevent interference. At the same time, since the elasticity (i.e., stiffness) of the silicone material will change during long-term operation, a frequency tracking (function of tracking the optimal operating frequency, generally tracking according to the current of the drive circuit) function needs to be added to the drive circuit of the piezoelectric vibrator 30.

[0040] Figure 2 For the working principle of a preferred embodiment, the piezoelectric element 4 drives the vibration diaphragm 3 to bend and vibrate under the drive of an alternating voltage signal at an ultrasonic frequency (about 20 - 21 kHz). The piezoelectric vibrator 30 is in a second-order vibration mode. In the second-order vibration mode, the piezoelectric vibrator 30 generates 3 points with the maximum amplitude, namely the center of the piezoelectric vibrator 30 and its left and right sides. Among them, the amplitude at the center of the piezoelectric vibrator 30 is the largest. During one vibration period, the working process can be divided into a first working state (as shown in Figure 2 A) and a second working state (as shown inFigure 2 as shown in B), which will be described in detail below.

[0041] The first working state ( Figure 2 A): The points with the maximum amplitude on both sides of the piezoelectric vibrator 30 vibrate downward, and the point with the maximum amplitude in the middle vibrates upward. The piezoelectric vibrator 30 obtains the vibration mode 301 of the first working state. Based on the principle of acoustic standing wave (the lower surface of the first top plate 11 serves as a reflector), high-pressure acoustic regions are gathered near both sides of the center amplitude maximum point in the first chamber 100 (it should be emphasized here that since there is a nozzle 5 in the center of the first top plate 11 and a through hole 310 in the center of the piezoelectric vibrator, no sound waves are emitted from the center and there is no reflector, which will cause no high-pressure acoustic region to be generated in the center of the first chamber 100). Under the action of sound pressure, the gases on both sides of the first chamber 100 flow towards the center. The fluid in the central region of the first chamber 100 jets outwards through the nozzle 5 and flows towards the second chamber 110 through the through hole 310. The fluid in the central region of the second chamber 110 flows towards both sides and jets upwards through the through hole 310. Based on the principle of synthetic jet, jet flow is realized at the center of the nozzle 5; it should be noted that during the process of the fluid jetting outwards from the center of the nozzle 5, due to the viscous effect of the fluid, eddy currents will be generated around the wall surface of the nozzle 5. Under the action of the eddy currents and pressure, the fluid outside the periphery of the side of the nozzle 5 is driven to flow into the first chamber 100, that is, the fluid in the atmospheric environment flows along the periphery of the nozzle 5 towards the first chamber 100.

[0042] The second working state ( Figure 2 B): The points with the maximum amplitude on both sides of the piezoelectric vibrator 30 vibrate upward, and the point with the maximum amplitude in the middle vibrates downward. The piezoelectric vibrator 30 obtains the vibration mode 302 of the second working state. Based on the principle of acoustic standing wave, high-pressure acoustic regions are gathered near both sides of the center amplitude maximum point in the second chamber 110 (it should be emphasized here that since there is a through hole 310 in the center of the piezoelectric vibrator, no sound waves are emitted from the center, which will cause no high-pressure acoustic region to be generated in the center of the second chamber 110). Under the action of sound pressure, the fluids on both sides of the second chamber 110 flow towards the center and jet upwards through the through hole 310. Part of it jets outwards through the nozzle 5 and part of it flows towards both sides of the first chamber 100; during the process of the fluid jetting outwards from the center of the nozzle 5, due to the viscous effect of the fluid, eddy currents will be generated around the wall surface of the nozzle 5. Under the action of the eddy currents and pressure, the fluid outside the periphery of the side of the nozzle 5 is driven to flow into the first chamber 100, that is, the fluid in the atmospheric environment flows along the periphery of the nozzle 5 towards the first chamber 100. It should be noted here that since the aperture of the nozzle 5 is larger than the aperture of the through hole 310, there is a flow resistance difference effect, and the fluid in the central region of the first chamber 100 has a tendency to jet outwards.

[0043] Driven by an alternating voltage signal with an ultrasonic frequency, the first working state and the second working state of the piezoelectric vibrator 30 alternate. Based on the principle of synthetic jet, continuous jet flow will be realized at the center of the nozzle 5; Traditional piezoelectric synthetic jet devices (refer toFigure 6 During the driving process of the piezoelectric vibrator 3, the up-and-down vibration of the piezoelectric vibrator 3 causes the cavity 2 to change alternately, and the fluid injection at the nozzle 5 is alternating. However, through the design of the composite cavity (the first cavity 100 and the second cavity 110) of the present invention, the fluid injection at the nozzle 5 can be made continuous, which can greatly improve the energy density and output performance of the piezoelectric synthetic jet.

[0044] Features of the present invention: 1. The piezoelectric vibrator 30 divides the cavity 2 into a first chamber 100 and a second chamber 110. Combined with the through hole 310, the fluid injection at the nozzle 5 is continuous, and the piezoelectric synthetic jet has high energy conversion efficiency and good output performance; 2. By introducing a support beam, the piezoelectric vibrator 30 reduces the stiffness and improves the frequency response characteristics of the piezoelectric vibrator 30, and increases the amplitude of the piezoelectric vibrator 30; 3. A matching layer 34 is added to the piezoelectric vibrator 30. Through balancing, this can effectively improve the vibration effect of the piezoelectric vibrator 30. At the same time, the acoustic impedance of the matching layer 34 is between the vibrating diaphragm 3 and the fluid, which can effectively improve the acoustic characteristics of the piezoelectric vibrator 30, and further improve the driving effect of the piezoelectric vibrator 30.

Claims

1. A piezoelectric synthetic jet actuator based on a combined cavity, comprising a base body, a cavity, a nozzle and a vibrating diaphragm, characterized in that: A pump chamber is provided inside the pump body; the vibrating diaphragm is arranged inside the pump chamber and divides the pump chamber into a first chamber and a second chamber; a through hole is provided at the position where the amplitude of the vibrating diaphragm is the largest; the through hole communicates the first chamber and the second chamber; a nozzle is provided on the pump body coaxially with the through hole; the nozzle communicates the first chamber and the external environment.

2. The piezoelectric synthetic jet actuator based on a combined cavity according to claim 1, wherein: The vibrating diaphragm is concentrically connected with a piezoelectric element; as a driving source, the piezoelectric element drives the vibrating diaphragm to vibrate under the drive of an AC voltage signal; the piezoelectric element and the vibrating diaphragm form a piezoelectric oscillator.

3. A piezoelectric synthetic jet actuator based on a combined cavity according to claim 1, characterized in that: The vibrating diaphragm is provided with a support beam.

4. A piezoelectric synthetic jet actuator based on a combined cavity according to claim 2, characterized in that: A matching layer is concentrically connected to one side of the vibrating diaphragm facing the first chamber; the acoustic impedance of the matching layer is between the vibrating diaphragm and the working gas.

5. The piezoelectric synthetic jet actuator based on a combined cavity according to claim 1, wherein: The height of the first chamber is greater than that of the second chamber; the height of the second chamber is not less than 2 times the maximum amplitude of the piezoelectric oscillator.

6. The piezoelectric synthetic jet actuator based on a combined cavity according to claim 1, wherein The aperture of the nozzle is larger than that of the through hole; the aperture of the nozzle is not less than 3 times the aperture of the through hole.

7. A piezoelectric synthetic jet actuator based on a combined cavity according to claim 1, wherein: The periphery of the piezoelectric oscillator is supported by an elastic washer and connected to the base body.

8. The piezoelectric synthetic jet actuator based on a combined cavity according to claim 1, wherein: The driving frequency of the piezoelectric oscillator is the ultrasonic frequency.

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