Synthetic jet actuator

Abstract

A non-clamping synthetic jet actuator includes a chamber layer having an internal chamber for receiving a fluid volume and an orifice providing fluid communication between the chamber and the external atmosphere; and an oscillating membrane having a piezoelectric material adapted to deflect in response to an electrical signal. The chamber has an opening on at least one planar surface of the chamber layer, and the chamber layer and the oscillating membrane are connected by a high-strength, low-shear-modulus adhesive material. The oscillating membrane is positioned adjacent to the planar surface having the chamber opening and is adapted to serve as a closing surface for the chamber opening. The oscillating membrane is adapted to compress and expand the volume within the chamber based on deflection generated by the piezoelectric material to generate fluid flow between the chamber and the external atmosphere through the orifice.

Description

Technical Field

[0001] This invention relates to synthetic jet actuators and methods for manufacturing and using synthetic jet actuators. In particular, the invention addresses improved synthetic jet actuators suitable for use in zero net mass flow applications. Background Technology

[0002] Piezoelectric driven films have been used to generate synthetic jets in various active flow control applications, such as reducing fatigue in wind turbine blades, electronic cooling, and drag reduction for air and ground vehicles. Studies have shown that these actuators can significantly alter airflow conditions around the obstructing fluid in active flow control (AFC) systems, thereby improving aerodynamic performance.

[0003] As an example, when applied to ground vehicles such as tractor-trailers, synthetic jet-based AFC can create virtual surface modifications, effectively altering the airflow around the vehicle and thus changing its aerodynamic drag without changing its shape. Although AFC systems are known in academic research, previous attempts to apply this technology to ground vehicles have been limited by high sound levels, low jet velocities and low jet flows, as well as high actuator power consumption.

[0004] Traditional AFC systems include the use of clamp-on actuators in zero net mass flow (ZNMF) designs. ZNMF designs aim to generate jet flow by manipulating the surrounding fluid without requiring an additional fluid supply, thus generating jet flow without any change in the net mass of the surrounding fluid. However, it has been found that traditional clamp-on actuators have several undesirable limitations, including performance limitations, scaling factor limitations, and integration factor limitations.

[0005] Nuventix has developed edge-clamping actuators with optimized acoustic performance for cooling LED lights; however, these actuators achieve very low jet velocities, insufficient for applications requiring high jet velocities such as drag reduction in vehicles. While laboratory tests at Rensselaer Polytechnic Institute have shown that edge-clamping actuators can achieve jet velocities exceeding 200 m / s, such actuators are considered commercially unfeasible because they require excessive size and mass, complex assembly methods, poor repeatability and sealing, and the assembled actuators cannot be finely tuned to resonant frequencies (e.g., to avoid high decibels), and require high power consumption.

[0006] Other attempts to design actuators to reduce noise levels include modifications such as prohibiting their use in many commercial applications requiring high jet velocities, integrating actuators into confined spaces (such as vehicle surfaces), or using multiple actuators (actuator arrays) operating simultaneously to achieve the desired results. U.S. Patent No. 8,564,217 provides an embodiment of an actuator design aimed at reducing noise, in which noise reduction of a single actuator is achieved at very low jet velocities (<30 m / s) by using a fixed phase angle, which is applicable in the case of a single actuator but ineffective in an actuator array. Another embodiment is provided in U.S. Patent No. 8,308,078, in which a synthetic jet actuator is provided with two orifices facing different directions to reduce the overall noise level generated by the jet produced from the orifices, but at the cost of limited directional jet velocity and making these actuators unsuitable for any application requiring directional control of the jet to include jets ejected in a common direction. European Patent No. 2,873,609 provides another embodiment in which the actuator is provided with a surround muffler that significantly increases the volume of the actuator and effectively prohibits the use of the actuator in applications that require integration into a confined space (such as surface integration applications).

[0007] Despite current technological advancements, there remains a need to improve synthetic jet actuators in order to further advance existing technologies and improve ZNMF design overall. Summary of the Invention

[0008] A synthetic jet actuator includes: a first chamber layer comprising an internal chamber for receiving a volume of fluid and an orifice providing fluid communication between the chamber and the external atmosphere; and a first oscillating membrane comprising a piezoelectric material adapted to deflect in response to an electrical signal. The chamber has an opening on at least one planar surface of the first chamber layer. The first chamber layer and the first oscillating membrane are connected by a high-strength, low-shear-modulus adhesive material. The first oscillating membrane is positioned adjacent to the planar surface having the chamber opening and is adapted to serve as a closing surface for the chamber opening. The first oscillating membrane is adapted to compress and expand the volume within the chamber based on deflection generated by the piezoelectric material to generate fluid flow between the chamber and the external atmosphere through the orifice.

[0009] The first oscillating membrane includes a substrate having a high storage modulus and a low loss modulus, and an angle tangent of less than 0.5. A piezoelectric material is connected to the substrate via a bonding material having high strength and high shear modulus through covalent and polymeric bonding. The substrate and bonding material are conductive and adapted to act as electrical connections for supplying electrical power to the piezoelectric material, these connections being configured to provide a non-uniform spatial coverage on the piezoelectric material, causing anisotropic deflection of the oscillating membrane.

[0010] The adhesive material connecting the oscillating membrane and the chamber layer includes at least one of the following: an adhesive film positioned between the first chamber layer and the first oscillating membrane, and an adhesive liquid applied to the surface of at least one of the first chamber layer and the first oscillating membrane. The first oscillating membrane is positioned such that the central axis of the oscillating membrane is aligned with the central axis of the chamber in the first chamber layer, and the central axis of the piezoelectric material is also aligned with the central axis of the chamber in the first chamber layer.

[0011] The first oscillating membrane is adapted to be in a prestressed state such that, in the unenergized state, the oscillating membrane rests on a neutral axis that provides a slightly expanded state for the chambers of the first chamber layer, and is forced to buckle when deflected into a compressed state under the energized state of the piezoelectric material. Preferably, the first oscillating membrane is adapted to have a prestress of at least 0.01 inches (in).

[0012] In some embodiments, the first chamber layer includes an expansion chamber embedded within an orifice, the expansion chamber including a series of baffles for buffering fluid flow through the orifice. In some embodiments, the boundary surfaces of the chambers of the first chamber layer include one or more inclined surfaces having a predetermined curvature corresponding to the curvature of the first oscillating membrane in a deflected compression state, for minimizing the volume within the chamber, the volume of which is predetermined to correspond to stagnant fluid flow. The actuator is configured to generate a jet velocity greater than 50 m / s at a resonant frequency below 500 Hz; preferably, it generates a jet velocity in the range of greater than 50 m / s to 100 m / s in a resonant frequency range of about 150 Hz to 475 Hz.

[0013] In one embodiment, the actuator further includes: a second oscillating diaphragm comprising a piezoelectric material adapted to deflect in response to an electrical signal; the chambers of the first chamber layer are formed as through-holes throughout the entire chamber layer and have two openings on opposing planar surfaces of the first chamber layer. The first oscillating diaphragm is positioned adjacent to a first planar surface of the first chamber layer having the first chamber opening and is adapted to serve as a closing surface for the first chamber opening; the second oscillating diaphragm is positioned adjacent to a second planar surface of the first chamber layer having the second chamber opening and is adapted to serve as a closing surface for the second chamber opening. Both the first and second oscillating diaphragms are adapted to compress and expand the volume within the chamber based on the deflection generated in each oscillating diaphragm by the respective piezoelectric material, thereby generating fluid flow between the chamber and the external atmosphere through the orifice. Both the first and second oscillating diaphragms are positioned such that the central axis of the respective oscillating diaphragm is aligned with the central axis of the chamber in the first chamber layer, and the central axis of the piezoelectric material of the respective oscillating diaphragm is also aligned with the central axis of the chamber in the first chamber layer.

[0014] In another embodiment, the actuator further includes: a second chamber layer including an internal chamber for receiving a volume of fluid and an orifice providing fluid communication between the chamber and the external atmosphere; a second oscillating membrane including a piezoelectric material adapted to deflect the second oscillating membrane in response to an electrical signal; and a third oscillating membrane including a piezoelectric material adapted to deflect the second oscillating membrane in response to an electrical signal. The chambers in both the first and second chamber layers are formed as through-holes extending through the entire respective chamber layer, and both chambers have two openings on opposite planar surfaces of the respective chamber layers. A first oscillating membrane is positioned adjacent to a first planar surface of a first chamber layer having a first chamber opening in the first chamber layer, and is adapted to serve as a closing surface for the first chamber opening of the chamber in the first chamber layer. A second oscillating membrane is positioned adjacent to a second planar surface of a first chamber layer having a second chamber opening in the first chamber layer, and is also adjacent to a first planar surface of a second chamber layer having a first chamber opening in the second chamber layer, and is adapted to serve as a closing surface for the second chamber opening of the chamber in the first chamber layer and the first chamber opening of the chamber in the second chamber layer. A third oscillating membrane is positioned adjacent to a second planar surface of a second chamber layer having a second chamber opening in the second chamber layer, and is adapted to serve as a closing surface for the second chamber opening of the chamber in the second chamber layer.

[0015] In this embodiment, the first and second oscillating films are adapted to compress and expand the volume within the cavity of the first chamber layer based on the deflection generated by the respective piezoelectric materials in each oscillating film, thereby generating fluid flow between the cavity and the external atmosphere through an orifice. The second and third oscillating films are adapted to compress and expand the volume within the cavity of the second chamber layer based on the deflection generated by the respective piezoelectric materials in each oscillating film, thereby generating fluid flow between the cavity and the external atmosphere through an orifice. The second oscillating film is adapted to expand the volume within the cavity of the second chamber layer while compressing the volume within the cavity of the first chamber layer, or is adapted to compress the volume within the cavity of the second chamber layer while expanding the volume within the cavity of the first chamber layer.

[0016] In another embodiment, the actuator further includes a second chamber layer comprising an internal chamber for receiving a volume of fluid and an orifice providing fluid communication between the chamber and the external atmosphere. The chambers in both the first and second chamber layers are formed as blind orifices, each having a single opening only on a planar surface of its respective chamber layer. A first oscillating diaphragm is located between the first and second chamber layers, adjacent to the planar surface of the first chamber layer containing the chamber opening in the first chamber layer, and adjacent to the planar surface of the second chamber layer containing the chamber opening in the second chamber layer. The diaphragm is adapted to compress and expand the volume within the chambers of the first chamber layer, and to compress and expand the volume within the chambers of the second chamber layer. The first oscillating diaphragm is adapted to expand the volume within the chambers of the second chamber layer while compressing the volume within the chambers of the first chamber layer, or to compress the volume within the chambers of the second chamber layer while expanding the volume within the chambers of the first chamber layer.

[0017] The actuator according to the invention may further include an acoustic housing disposed outside the first chamber layer and the first oscillating diaphragm for suppressing noise generated by the first oscillating diaphragm. The acoustic housing includes an outer shell with an absorbing material and an acoustic barrier positioned within the outer shell, the absorbing material being positioned outside the oscillating diaphragm and the acoustic barrier being disposed outside the absorbing material.

[0018] The actuator according to the invention may further include an acoustic nozzle positioned outside an orifice of a first chamber layer and adapted to extend a flow path for fluid inflow and outflow from the orifice. The acoustic nozzle includes an outer ring made of an acoustic barrier material, within which are disposed an acoustic substrate and an acoustic absorbing layer. The acoustic substrate is positioned outside the extended flow path provided to the orifice of the chamber layer, while the acoustic absorbing layer is positioned outside the acoustic substrate. The acoustic nozzle may be an integrally integrated component of the chamber layer, and the flow path provided within the acoustic nozzle includes a flow expansion chamber.

[0019] The present invention also includes a method of manufacturing an actuator, comprising the steps of: forming an oscillating membrane by attaching a piezoelectric material to a substrate; thermoforming the oscillating membrane by voltage compression and / or prestressing it by electrically actuating the piezoelectric material during assembly; positioning a first oscillating membrane adjacent to a planar surface of a first chamber layer having a chamber opening, and connecting the first oscillating membrane and the chamber layer by an adhesive material; positioning a separate mass structure within the oscillating membrane, adjacent to the piezoelectric material, and securing the separate mass structure in place with a high-strength, low-shear-modulus adhesive; generating vacuum pressure to apply uniform atmospheric pressure, thereby pressing the chamber layer and the oscillating membrane together; and thermosetting the chamber layer and the oscillating membrane while applying uniform atmospheric pressure.

[0020] The general description above and the detailed description below are exemplary and explanatory only, intended to provide further explanation of the claimed invention. The included drawings provide a further understanding of the invention; they are incorporated in and constitute a part of this specification; the illustrative embodiments of the invention, together with the description, serve to explain the principles of the invention. Attached Figure Description

[0021] The features and advantages of the present invention will become apparent from the following detailed description, which is provided in connection with the accompanying drawings described below:

[0022] Figures 1a and 1b show schematic diagrams of conventional synthetic jet actuators, including: (a) an assembly diagram of the clamping actuator, and (b) an exploded view of the clamping actuator;

[0023] Figures 2a to 2c show schematic diagrams of embodiments of the actuator according to the present invention, including: (a) an assembly view of the actuator; (b) an exploded view of the actuator with the oscillating diaphragm layer separated from the chamber layer; and (c) a further exploded view of the actuator with the individual layers of the composite oscillating diaphragm separated.

[0024] Figure 3 A schematic diagram of the exploded view of the oscillating membrane in Figure 2c is shown, connected to a power source;

[0025] Figures 4a and 4b show schematic diagrams of a single-form assembly of the oscillating membrane in the actuators of Figures 2a and 2c, including: (a) an assembly view of the single-form membrane; and (b) an exploded view of the single-form membrane.

[0026] Figures 5a and 5b show schematic diagrams of the single-morphology membrane assembly with the chamber layer in Figures 4a and 4b, including: (a) an assembly diagram of the chamber and the single-morphology membrane layer; and (b) an exploded view of the chamber and the single-morphology membrane layer;

[0027] Figures 6a and 6b show schematic diagrams of the chamber and single-morphology membrane assembly in Figures 5a and 5b, wherein additional mass is provided to the single-morphology membrane, including: (a) an assembly view of the chamber and the single-morphology membrane with additional mass; and (b) an exploded view of the chamber and the single-morphology membrane with additional mass.

[0028] Figure 7 A schematic diagram of an actuator with a pre-tensioned composite oscillating diaphragm is shown.

[0029] Figure 8 A schematic diagram of a fully covalent and polymerically bonded actuator assembly is shown in Figures 2a to 2c.

[0030] Figures 9a to 9c show schematic diagrams of embodiments of the actuator according to the present invention, having two chambers for noise reduction, including: (a) an exploded view of the actuator layer, (b) a cross-sectional view of the assembled actuator, and (c) a schematic diagram showing the operation of the oscillating diaphragm in the actuator;

[0031] Figures 10a to 10c show schematic diagrams of another embodiment of the actuator according to the invention, having two chambers for noise reduction, including: (a) an exploded view of the actuator layer, (b) a cross-sectional view of the assembled actuator, and (c) a schematic diagram showing the operation of the oscillating diaphragm in the actuator;

[0032] Figures 11a to 11c show schematic diagrams of embodiments of the actuator according to the present invention, having a center-aligned chamber and an oscillating diaphragm, including: (a) an exploded view of the actuator layer, (b) a cross-sectional view of the assembled actuator, and (c) a comparative schematic diagram of an off-center actuator arrangement and a centered actuator arrangement.

[0033] Figures 12a and 12b show schematic diagrams of embodiments of the actuator according to the present invention, having a composite acoustic housing for side-based noise reduction, including: (a) an exploded view of the actuator layer, and (b) a cross-sectional view of the assembled actuator;

[0034] Figures 13a and 13b show schematic diagrams of embodiments of the actuator according to the present invention, having a noise-reducing acoustic nozzle, including: (a) an exploded view of the actuator layer, and (b) a cross-sectional view of the assembled actuator;

[0035] Figures 14a and 14b show schematic diagrams of an embodiment of an actuator with an integrated acoustic nozzle according to the present invention, including: (a) an exploded view of the actuator layer, and (b) a cross-sectional view of the assembled actuator and a cross-sectional view of the airflow path with the embedded acoustic nozzle;

[0036] Figures 15a and 15b show schematic diagrams of embodiments of an actuator with an embedded acoustic nozzle according to the present invention, including: (a) an exploded view of the actuator layer, and (b) a cross-sectional view of the airflow path of the embedded acoustic nozzle;

[0037] Figures 16a and 16b show schematic diagrams of embodiments of an actuator with an inclined chamber according to the present invention, including: (a) an exploded view of the actuator layer, and (b) a cross-sectional view of the assembled actuator; and

[0038] Figure 17 A schematic diagram of a synthetic jet actuator array suitable for reducing noise through phase synchronization is shown. Detailed Implementation

[0039] The following disclosure discusses the invention with reference to the embodiments shown in the accompanying drawings, but does not limit the invention to these embodiments.

[0040] The use of any and all embodiments or exemplary language (e.g., “such as”) provided herein is merely for the purpose of better illustrating the invention and, unless otherwise stated, does not constitute a limitation on the scope of the invention. Unless explicitly stated in the context, no language in this specification should be construed as indicating that any unclaimed element is necessary or critical to the implementation of the invention.

[0041] Unless the context otherwise requires, the singular forms of “a,” “an,” and “the” used herein include plural references. Unless the context otherwise requires, the term “or” should be understood as inclusive “or.” Terms such as “first,” “second,” and “third,” when used to describe multiple devices or elements, are used only to indicate the relative action, position, and / or function of the individual devices, and do not necessarily refer to a specific order of these devices or elements, or any specific number or ranking of these devices or elements.

[0042] The use of the term "substantially" in this document for any attribute or condition means a sufficiently small deviation such that there is no significant reduction relative to the identified attribute or condition. It will be understood by those skilled in the art that the exact degree of deviation permissible in a given situation will depend on the specific circumstances.

[0043] As will be understood by one of ordinary skill in the art in the appropriate context, the use of the terms “about” or “approximately” is intended to describe values ​​above and / or below the stated value or range. In some cases, this may include values ​​in the range of approximately + / - 10%; in others, it may include values ​​in the range of approximately + / - 5%; in still others, it may include values ​​in the range of approximately + / - 2%; and in yet another still, it may include values ​​in the range of approximately + / - 1%.

[0044] It will be understood that the terms “comprising” and / or “including”, when used in this specification, specify the presence of the said feature, integral, step, operation, element, and / or component, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or groups thereof, unless indicated herein or expressly contradicted by the context.

[0045] Unless otherwise stated, references to numerical ranges herein are used as abbreviations to refer individually to each individual value falling within the range, including: the endpoints of the range, each individual value within the range, and all intermediate ranges contained within the entire range, each of which is included in this specification as separately stated herein.

[0046] Unless otherwise stated, or clearly contradicted by the context, the methods described herein may perform individual steps in any suitable order, including: the exact order disclosed, without any intermediate steps or one or more other steps inserted between the disclosed steps; performing the disclosed steps in an order different from the exact order disclosed; performing one or more steps simultaneously; and omitting one or more disclosed steps.

[0047] Figures 1a and 1b illustrate embodiments of a conventional synthetic jet actuator 100 in the form of a clamping actuator in an assembled state (Figure 1a) and an exploded state (Figure 1b). In this conventional embodiment, the actuator 100 is shown as comprising several layers, including: a central chamber layer 110; two oscillating diaphragm layers 120a / 120b; and two outer layers 130a / 130b. The layers in the conventional actuator 100 are held together by a plurality of clamping elements 140, which in this embodiment are exemplified by a plurality of bolts and mating nuts (not shown). Each bolt has a head with a threaded shaft extending from the head, the threaded shaft of each bolt being formed to extend through a corresponding series of through holes in the layers and to mate with a corresponding nut, such that the layers of the actuator 100 are compressed between the nut and the bolt head.

[0048] Conventional actuators (such as actuator 100) have been found to have numerous undesirable limitations, including performance limitations, scaling factor limitations, and integration factor limitations. Performance issues stem from: compromised robustness of several layers in the assembled state, impaired repeatability due to uneven pressure distribution within chamber layer 110, and low efficiency due to air leakage in the assembled actuator 100. The scaling factor is limited because each actuator requires manual assembly, and numerous components are needed to mechanically secure several layers of each actuator. These conventional actuators are also limited by integration factors, such as excessive mass in the assembled actuator due to the additional weight required for clamping elements and associated hardware, making it impractical for smaller applications requiring actuator positioning in confined spaces (e.g., aircraft wings, wind turbine blades, or automotive body components).

[0049] This invention relates to a synthetic jet actuator and a method for producing such an actuator, which employs one or more piezoelectrically driven oscillating films to generate a compressed jet flow rate and incorporates actuators particularly suitable for integration into aerodynamic surfaces, as required in many commercial applications. The stacked layers in the actuator according to the invention are bonded together to fix each other, such that the resulting actuator is made lightweight, small in overall size, and easy to manufacture in cost- and energy-efficient processes.

[0050] Typically, in piezoelectric actuators, a voltage is supplied to deflect the piezoelectric element along with a corresponding oscillating diaphragm, increasing the pressure within the corresponding chamber and forcibly expelling fluid from the chamber through a shaped orifice. This invention provides novel material combinations, design features, and fabrication techniques to achieve unprecedented performance beyond what conventional actuators can offer, and allows for the optimization of previously considered mutually exclusive performance parameters, such as aerodynamic performance, acoustic performance, integration into confined spaces, and the use of multiple simultaneously acoustically synchronized actuators.

[0051] The synthetic jet actuator according to the present invention can generate a synthetic jet with a reduced sound level without compromising the aerodynamic performance of the generated jet. The reduction in sound level can be achieved in several ways, including but not limited to changing the shape of the actuator and the assembly used to operate the actuator, exhibiting unprecedented performance in reducing noise levels and overcoming previous methods while allowing for further optimization of performance parameters.

[0052] The system and method according to the invention are proposed for the production of synthetic jet actuators based on piezoelectric actuation films, overcoming the limitations of previous conventional systems and methods, maximizing jet velocity and momentum while reducing resonant frequency (e.g., below 500 Hz), minimizing the amount of piezoelectric material, minimizing power and energy consumption, and minimizing the overall weight and size of the actuator.

[0053] The proposed system and method according to the invention are also used to achieve high jet velocities and momentum while remaining suitable for integration into confined spaces (e.g., integration into surfaces in commercial applications) and to achieve compliance with regulatory standards, such as those set by the U.S. Federal Motor Transportation Safety Administration (FMCSA) and the European Union.

[0054] Figures 2a to 2c illustrate embodiments of the non-clamping actuator 200 according to the invention, the actuator 200 being shown in an assembled state (Figure 2a) and an exploded state (Figure 2b); and Figure 2c shows a further exploded view.

[0055] As shown in Figures 2a and 2b, the actuator 200 includes a chamber layer 210 sandwiched between two composite oscillating membrane layers 220a / 220b. The chamber layer 210 includes a body having a first planar surface and a second planar surface, an outer perimeter, and an inner perimeter, the inner perimeter defining a chamber 211 within the chamber layer 210. The chamber 211 is open to at least one of the two planar surfaces and may be open to both planar surfaces. When placed adjacent to the chamber, the oscillating membrane layer 220 acts as a closed surface above the opening of the chamber 211, thereby defining a closed space within the chamber 211 for retaining fluid volume. The chamber layer 211 also includes an orifice 212 that provides an airflow path between the chamber 211 and the atmosphere outside the actuator 200 for drawing airflow into or out of the chamber 211.

[0056] As shown in Figure 2c, both oscillating membranes 220a / 220b include a substrate 221, which is integrally coupled to a piezoelectric disk 223 via a high-strength, high-shear-modulus covalent and polymeric bond 222. The polymeric bond 222 can be formed from a single-component or two-component thermosetting material, such as, but not limited to, a two-component epoxy resin, a single-component methacrylate, or a low-melting-point metal (such as silver solder). In some embodiments, the polymeric bond 222 can be formed by a thermosetting film adhesive or a "prepreg." In some embodiments, as will be discussed further in detail below, the polymeric bond 222 can be conductive. Both oscillating membranes 220a / 220b further include an outer layer 224 that encapsulates and secures several layers of the respective membrane 220 in place.

[0057] In use, the piezoelectric disc 223 operates by electrical power supplied from the power source 226 via electrical connection 225 (see...). Figure 3Supplying electrical power to the piezoelectric disk 223 causes the disk to deform. Due to the overall coupling between the disk 223 and the substrate 221, the deformation of the disk 223 causes a corresponding offset of the substrate 221 in the same direction. Preferably, the substrate 221 is formed of a material that is substantially thin, has a high storage modulus, and has a minimized loss modulus, which results in a minimized tangent (tandelta). Table I provides the ranges of these parameters and their preferred values.

[0058] In some embodiments, the substrate 221 may be a metal, such as, but not limited to, steel, aluminum, titanium, brass, copper, etc., including alloys thereof. In some embodiments, the metal may be selected from corrosion-resistant grades, such as, but not limited to, stainless steel. The metal may also be modified by using surface treatments (such as, but not limited to, solvent cleaning, polishing, acid etching, alkaline treatment, electroplating, and combinations thereof) to provide further corrosion resistance or enhanced bonding strength. The surface may also be treated with high-energy processing (such as flame, corona, plasma, or arc). In a preferred embodiment, the substrate is 0.005'' of 6061 aluminum, cleaned with acetone, polished with 120-grit alumina, and etched with chromic acid prior to bonding with the piezoelectric material.

[0059] In some embodiments, substrate 221 may include a high-modulus polymer, a filled polymer, or a fiber-reinforced polymer. These polymers may comprise thermoplastics or thermosetting plastics and may include solids such as, but not limited to, particles of polymers, metals, or minerals (including but not limited to, glass, talc, carbon, and graphite), hollow microspheres, nanocomposite materials, clay, fibers, or sheets. The fibers may be chopped short fibers, discontinuous fibers, short or long fibers, or continuous, woven, non-woven, or randomly oriented mats. Examples of suitable fibers include, but are not limited to, glass fibers, e-glass, s-glass, cr-glass, carbon fibers, low-modulus carbon, medium-modulus carbon, high-modulus carbon, polyethylene, polypropylene, nylon, polyester, aramid, Kevlar, PPS, and combinations thereof. The fiber-reinforced matrix may also be produced from a "prepreg material".

[0060] Substrate 221 may comprise multiple layers, each independently selected from the materials disclosed herein, with different layers having independent fiber orientations. The fiber laminate may be balanced or unbalanced, symmetrical or asymmetrical. The polymer matrix may comprise thermosetting or thermoplastic materials, including but not limited to: epoxy resins, polyurethanes, polyesters, vinyl esters, PPS, polypropylene, PTFE, Teflon, polyethylene, or phenols. The matrix may contain toughening agents, softening agents, wetting agents, defoamers, Tg reinforcing agents, and materials with a density greater than 2.6 g / cm³. 3The material may be further modified using other materials, or composite materials known to those skilled in the art. In a preferred embodiment, the substrate is a pre-formed 0.005-inch 0 / 90 glass braided laminate in an amine-cured epoxy resin matrix, solvent-cleaned with isopropanol, polished with 220-grit sandpaper, and dried and wiped before bonding the piezoelectric pad.

[0061] In some embodiments, the piezoelectric pad 223 may be covalently bonded to the substrate 221 during the fabrication of the substrate 221. This can be performed through processes including, but not limited to, injection molding, overmolding, thermoforming, heat sealing, RTM, VARTM, SCRIMP, vacuum bagging, autoclave processes, or wet bonding. In a preferred embodiment, the piezoelectric pad 223 is placed on a square-woven 7-ounce e-glass pad impregnated with amine-cured epoxy resin. Vacuum bagging technology can be used for applications that apply uniform pressure during temperature curing, during which the pad 223 is integrally bonded to the substrate 221 as the substrate is formed.

[0062] As shown in Figures 2a to 2c, the layered composite oscillating film 220 may include one or more outer layers 224 located outside the piezoelectric disk 223. Previously, conventional actuators used low-modulus outer layers or no outer layers at all, because conventional wisdom held that high-modulus layers coupled to the piezoelectric disk and offset relative to the neutral bending axis would prevent or inhibit film deflection and therefore could not be used. However, it has been surprisingly found that, in this invention, the use of a high-modulus outer layer 224 formed from a material substantially similar to the substrate 221 (such as a thermoplastic, thermosetting, or metal) can result in an unexpected increase in jet velocity. While not bound by theory, it is believed that the coupling between the piezoelectric disk 223 and the substrate 221 at the edge of the disk 223 increases the coupling to the substrate 221, which in turn increases the deflection of the substrate 221. In a preferred embodiment, one or more outer layers 224 are provided in 7 oz, square-woven, glass fiber form in a cycloaliphatic amine-cured epoxy resin laminate.

[0063] Figure 3 An exploded view of a single composite oscillating membrane 220 is shown. As illustrated in this embodiment, the piezoelectric disk 223 is deformed by supplying electrical power via an electrical connection 225, illustrated in this embodiment as an electrode, which provides electrical communication between the power source 226 and the surface of the piezoelectric disk 223. Suitable electrical connection embodiments include, but are not limited to, wires, strips, conductive metal strips, fibers, and stencil printing, screen printing, or printed circuits. In some embodiments, the substrate 221 may include a conductive material such as metal or carbon fiber, serving a dual role as both an electrode and a mechanical component of the layered composite membrane.

[0064] Electrical connection 225 can be attached to any location on the surface of piezoelectric disk 223 and cover any percentage of that surface. In some embodiments, electrical connection 225 may be attached only to the edge or center of piezoelectric disk 223; in other embodiments, electrical connection 225 may be formed in a ring shape or may be helical to reduce flexural strain thereon. Electrical connection 225 may also include: conductive voltage-sensitive adhesive, methacrylate, filled thermosetting material, solder, or conductive yarn (such as metal-coated nonwoven fabric or metal mesh), or anisotropic conductive adhesive film (ACF). In a preferred embodiment, electrical connection 225 comprises a 1 / 8'' wide copper strip with conductive pressure-sensitive adhesive (PSA). In another preferred embodiment, electrical connection 225 comprises Ni or Cu-coated carbon yarn, such as those supplied by Technical Fibre Products, having an air weight of 20 g / m². The surface of piezoelectric disk 223 may also include a conductive layer, which may be thin and have low flexural stiffness, such as, but not limited to, a nickel plating or copper cladding. In some embodiments, the piezoelectric disk 223 may have a nickel surface with a deposition thickness of 20 micrometers.

[0065] In a preferred embodiment, the electrical connection 225 can be designed to intentionally provide non-uniform spatial coverage on the piezoelectric disk 223. This non-uniform coverage, combined with the resistance from the surface of the piezoelectric disk 223, produces anisotropic deflection of the oscillating film 220 that is non-uniform in both time and location. By carefully selecting the orientation of the electrical connection 225 and the surface resistance of the piezoelectric disk 223, an unexpected improvement in jet velocity can be observed. In a preferred embodiment, the orientation extends 1 / 8 of the length perpendicular to the orifice 212. The copper strip is connected to the Ni-sprayed surface of the piezoelectric disk 223 using a conductive PSA, where the resistance across the connection is less than 2 ohms, but the electrode surface has a resistance of 10 to 40 ohms per inch away from the copper strip. Supplying electricity to the copper strip causes a deflection to be generated along the central axis of the piezoelectric disk 223, with the highest amplitude, although this amplitude decreases near the edge of the piezoelectric disk due to resistance loss across the surface of the disk 223. This induces the formation of a partial wave pattern in the piezoelectric disk 223 and throughout the oscillating diaphragm 220, thereby directing the fluid in the chamber 211 to the orifice 212 and producing an increase in jet velocity of up to 5%. Furthermore, the reduction in actuation force near the periphery of the piezoelectric disk 223 reduces strain during material transition, which has been found to lead to a significant improvement in the disk 223's lifetime.

[0066] Piezoelectric materials are well known to those skilled in the art, and can be selected from the group including, but not limited to, PZT, quartz, zinc oxide, PVDF, barium titanate, or the like. Because these materials are relatively expensive, the amount of material used in the oscillating membrane 220 is limited. In some embodiments, the reduction of piezoelectric material can be achieved by using relatively thin piezoelectric disks 223 with a thickness between 0.01" and 0.1", with each oscillating membrane 220 containing only one piezoelectric disk 223. An oscillating membrane using only a single piezoelectric disk 223 can be referred to as a monomorphic membrane. Figures 4a and 4b illustrate one embodiment of the monomorphic membrane 220', where, for ease of illustration, descriptions of the polymer bond 222 and the outer layer 224 are omitted.

[0067] By using only a single piezoelectric disk 223, the monomorphic membrane 220' has the advantages of reduced power and energy consumption, as well as a lower resonant frequency. As shown in Figures 4a and 4b, in the monomorphic membrane 220', the piezoelectric disk 223 can be placed on the neutral bending axis of the oscillating membrane, either inside or outside the chamber 211 of the chamber layer 210. In a preferred embodiment, the monomorphic membrane 220' is designed such that the single piezoelectric disk 223 is on the side of the substrate 221 opposite to the chamber 211. Figures 5a and 5b show one such embodiment of the monomorphic membrane 220' assembled in an actuator 200, which employs only a single oscillating membrane 220, wherein the piezoelectric disk 223 of the single monomorphic membrane 220' is located on the outer surface of the substrate 221, opposite to the chamber 211. Similarly, for ease of illustration, the description of the polymer bond 222 and the outer layer 224 is omitted in the illustrated embodiments.

[0068] In some embodiments, the deflection and resonant frequencies of the oscillating membrane 220 can be further altered by using high-density materials. Empirical studies have shown that increasing the mass of the oscillating membrane 220 without significantly altering other mechanical properties can dramatically change the response of the membrane 220. This increase in mass can be achieved by inserting a high-density material, such as tungsten, into the substrate 221, or by making the substrate 221 substantially formed of tungsten. In some embodiments, additional mass can be achieved by filling the thermoplastic and thermosetting plastics of the composite oscillating membrane 220 with a high-density material, such as barium sulfate. In some embodiments, an additional, independent mass structure can be incorporated into the composite oscillating membrane 220. Figures 6a and 6b illustrate one embodiment of the actuator 200, in which a 5-ounce lead disk 227 is attached to the center of the outer surface of a piezoelectric disk 223 via a high-strength, low-shear-modulus adhesive (not shown). Due to the attachment location and the low shear modulus of the adhesive, the piezoelectric disk 223 is still allowed to bend freely, while the added mass 227 reduces the resonant frequency by 40% without significantly affecting the jet velocity.

[0069] While not bound by theory, it is believable that the added mass increases the momentum of the oscillating diaphragm 220, resulting in greater displacement during cyclic power supply. Furthermore, the increased weight leads to a decrease and broadening of the resonant frequency. This is particularly advantageous for the use of net-zero mass flow non-clamping actuators in aerodynamic applications (including tractor tractor heads), where the market demands resonant frequencies below 500 Hz. By increasing the mass of the oscillating diaphragm 220, the resonant frequency can be reduced and broadened from 800 Hz to a range of approximately 150 to approximately 475 Hz.

[0070] Buckling actuators are well known to those skilled in the art. In the design according to the invention, the unenergized oscillating diaphragm 220 remains on the neutral bending axis, resulting in... Figure 7 The description describes a slight expansion state. When energized, the oscillating diaphragm 220 is forced to buckle and abruptly move to the side opposite the neutral bending axis. This is expected to lower the resonant frequency while increasing the force exerted by the diaphragm on the air inside the chamber, resulting in a higher jet velocity value (compared to a non-buckling actuator of similar size) at a lower sound level (the reduction in actuation frequency is equivalent to a lower sound level).

[0071] As an alternative to conventional mechanical displacement used for prestressing, the present invention includes voltage compression, which can be used to thermoform the oscillating membrane 220 by raising its temperature above its softening or melting point, thereby deforming it, and then cooling it in the deformed state. Thermoforming can be performed before or after actuator assembly. In some embodiments, the actuator can be assembled using a mechanically fastened plate, giving it variable displacement, such that the fasteners allow the membrane to be repeatedly displaced or repositioned and subsequently clamped for fine-tuning of performance parameters.

[0072] By electrically actuating the piezoelectric disk 223 during actuator assembly, the buckling geometry of the actuator 200 can be optimized. The actuated piezoelectric disk 232 will deform to its desired geometry; therefore, by actuating the piezoelectric disk 223 during actuator assembly, the assembled actuator 200 will be pre-optimized for a specific combination of piezoelectric disk 223 and substrate 221. Control of the static voltage can further finely tune this buckling geometry and performance parameters.

[0073] The present invention includes an oscillating membrane 220 and a method for manufacturing an actuator 200 incorporating such a membrane to produce a synthetic jet actuator having a fully polymerized and covalently bonded structure with uniform adhesive strength and minimized internal stress.

[0074] Existing methods for assembling zero-net-mass-flow edge-clamped piezoelectric-driven synthetic jet actuators rely on mechanical clamping. These conventional methods suffer from drawbacks such as an increased number of parts and assembly steps, the potential for leakage through interfaces, increased mass and volume, and further potential mechanical failures due to fastener loosening over time during actuator operation. Non-mechanical methods that have been developed include injection molding, overmolding, or thermoforming. While these techniques are known for their high throughput, the use of high thermal stress and non-uniform pressure has been found to lead to in-situ strain and poor repeatability in the actuator. Other methods include the use of liquid adhesives, although these methods have been found to lack the ability to tightly control the bonding lines and pose a risk of contaminating small design features such as orifices 212 in chamber layer 210.

[0075] This invention avoids the shortcomings of existing methods by using a new application of Class B thermosetting adhesive film and vacuum bag processing to produce actuators. It has strict control over the bonding line and spatially uniform interlayer bonding strength, improves jet performance, reduces complexity, lowers overall weight, and improves consistency between parts.

[0076] Assembling one or more oscillating membranes 220 to the chamber layer 210 may include the surface treatments described above. In one embodiment, a Class B thermosetting adhesive film is cut or punched from a sheet stock and placed between the membrane 220 and the chamber layer 210. The film adhesive may also be applied as a liquid to one or both layers and subjected to a Class B treatment prior to assembly. The film adhesive may also be provided in the same form as the polymerization / adhesive bonding 222. Figure 8 As shown, several layers are then sealed in a bag 30 connected to a vacuum source 40 from which air is removed, thereby applying atmospheric pressure uniformly to the surfaces of the layered components. Unlike existing methods using hot pressing, which introduces point loads and misalignments on small features, using vacuum-based atmospheric pressure ensures perfectly uniform layer stacking and significantly reduces capital costs due to the elimination of expensive molds. Several vacuum bags 30 can be assembled and loaded into a processing oven where the temperature is increased, causing the film adhesive to briefly reflow and form a polymeric covalent bond between the layered components before curing.

[0077] The layered components can be cured for approximately 1 to 4 hours within a temperature range of approximately 140 ºF to approximately 350 ºF, allowing the thermosetting properties to reach their full potential. In a multi-step assembly, the maximum curing temperature can be reserved for the final step to "co-cure" all layers of the composite actuator. Inspection of the bond line after such curing revealed that adhesive flow can be controlled to an accuracy of 0.030". It was also found that actuators manufactured under these conditions exhibit increased jet velocities, up to 25% higher than those produced by mechanically fixed actuators.

[0078] While not bound by theory, the method according to the invention is believed to provide a larger and more spatially uniform interface between the oscillating diaphragm and the chamber compared to that achieved with mechanical fasteners, in the case of a high modulus combination greater than about 8000 PSI, while also eliminating leakage paths. Since no external clamping is required, the method of the invention also provides significant weight, cost, and parts savings, allowing these zero net mass flow non-clamping actuators to be used in specific applications, including improving the aerodynamics of tractor-trailer heads.

[0079] Certain materials, particularly those that are corrosion-resistant and inherently non-reactive, may be difficult to covalently bond with thermosetting materials. These materials may include stainless steel, aluminum, or polypropylene. If desired, a “bonding layer” can be used instead of a thermosetting material to achieve a similar effect. A “bonding layer” is typically a material, or a combination of two or more compatible materials, that forms a bonding layer between two incompatible materials. The bonding layer may include, for example, a thermoplastic material that can, typically through melt processing or chemical reaction, provide adhesive force to two adjacent materials; the thermoplastic material may be modified acrylic, or anhydride-grafted polymers, or polymers similar to, but not limited to, DuPont Bynel, Nucrel, and Fusabond grades, as further examples, or materials described and referenced in U.S. Patent Nos. 8,076,000; 7,807,013; and 7,285,333. The melting point or melt index of the link layer can be selected so that the link layer can be post-processed without the other non-metallic materials in other parts of the actuator melting or flowing substantially.

[0080] The method according to the present invention, including the use of one or more electrodes, a high-modulus outer layer, covalent-polymer bonding, a vacuum bag, and careful control over the thickness, storage, loss modulus, and mass distribution of the substrate, can effectively produce synthetic jet actuators that overcome the limitations of existing designs, including generating jet velocities greater than 100 m / s at frequencies below 500 Hz. The synthetic jet actuators have dimensions and weights feasible for practical applications, as detailed in Table I below.

[0081]

[0082] The present invention includes additional designs for synthetic jet actuators, including designs that combine multiple chamber layers with one or more oscillating membrane arrangements (which may include monomorphic membranes), arrangements that share a common oscillating membrane between two chamber layers, and arrangements that include additional noise reduction elements.

[0083] Figures 9a and 9c illustrate one embodiment of a synthetic actuator 300, which comprises laminated stacked layers including three oscillating membranes 320a / 320b / 320c and two chamber layers 310a / 310b, each chamber layer 310 having a separate chamber 311 and an orifice 312. As shown in Figure 9c, the layers are stacked such that the two chamber layers 310a / 310b cyclically share a common oscillating membrane 320b, which switches between a first mode and a second mode. In the first mode, the common oscillating membrane 320b compresses the volume in the top chamber 311a and expands the volume in the bottom chamber 311b; and in the second mode, the common oscillating membrane 320b expands the volume in the top chamber 311a and compresses the volume in the bottom chamber 311b. In this way, the actuator 300 is adapted to ensure that the airflow through the two orifices 312a / 312 is always in opposite directions to each other.

[0084] As those skilled in the art will understand, the noise level generated by the synthetic actuator is a function of the sound waves generated by the airflow exiting from the actuator orifice and the airflow entering the actuator orifice. In the arrangement shown in Figure 9c, because the airflows travel in opposite directions, the sound waves generated by individual airflows are opposite to each other, causing interference between them and resulting in partial cancellation of the sound waves, thereby reducing the overall noise level. As shown in Figures 9a to 9c, acoustic testing of an actuator with a three-diaphragm design revealed a 14.7 dB reduction in sound power level compared to that generated by a single synthetic jet actuator. Advantageously, since the two orifices 312a / 312b face a common direction, the reduction in noise level is achieved without substantial loss of aerodynamic performance. Additional parameters for a preferred embodiment of the actuator 300 are provided in Table II below.

[0085] Figures 10a and 10c illustrate another embodiment of the synthetic actuator 400, which comprises laminated stacked layers including two capped chamber layers 410a / 410b, each capped chamber layer having a chamber 411a / 411b and an orifice 412a / 412b, and an intermediate piezoelectric oscillating membrane 420. As shown in Figure 10c, the actuator 400 is adapted to periodically share a common oscillating membrane 420 between the two chamber layers 411a / 411b, such that the airflows through the two orifices 412a / 412b are always in opposite directions, thereby causing the sound waves generated by the two airflows to interfere with each other, resulting in reduced noise. In this embodiment, using a single oscillating membrane 420 reduces cost and power consumption. Additional parameters for the preferred embodiment of the actuator 400 are provided in Table II below.

[0086] Figures 11a and 11c illustrate another embodiment of a synthetic actuator 500, which consists of laminated stacked layers including two oscillating membranes 520a / 520b and a single chamber layer 510 having a cavity 511 and an orifice 512. In contrast to mechanically fixed actuators, where fastening elements (e.g., screws, bolts, etc.) are positioned around the cavity 511 and restrict the volume of the cavity, the use of laminates in the actuator 500 can significantly increase the cavity volume and align the central axis of the oscillating membrane with the central axis of the cavity 511.

[0087] As can be seen from the comparison shown in Figure 11c, the conventional clamping actuator 100 has a chamber 111 with a central axis offset from the central axis of the oscillating membranes 120a / 120b, while the actuator 500 according to the invention provides additional space for centering the chamber 511, such that the central axis of the chamber is aligned with the central axis of the oscillating membranes 520a / 520b. Since the piezoelectric disk is positioned at the center of the oscillating membranes 520a / 520b, the alignment of the chamber's central axis and the membrane's central axis also results in simultaneous alignment with the piezoelectric disk. This large-volume chamber 511, aligned with the central axis of the oscillating membranes 520a / 520b and the centrally located piezoelectric disk, allows for greater displacement of the membranes 520a / 520b, resulting in a larger jet volume and a lower resonant frequency. Additional parameters for the preferred embodiment of the actuator 500 are provided in Table II below.

[0088] Figures 12a and 12b illustrate another embodiment of actuator 600, which comprises laminated stacked layers including two oscillating diaphragms 610a / 610b and a chamber layer 610 having a cavity 611 and an orifice 612. On each side of actuator 600, an acoustic housing 630 is provided to suppress noise generated by each oscillating diaphragm 620. The housing 630 has a minimum volume to avoid suppressing the performance of actuator 600. Typically, the outer housing volume doubles when the frequency decreases by one-third of an octave. The volume of the housing 630 on each side of the sealed portion of actuator 600 is approximately 40 times the volume of air moved by each piezoelectric disc during actuation. This volume is filled with an acoustic absorbing material 631, such as melamine foam, fiberglass insulation, or mineral wool, thereby increasing the apparent volume and lowering the resonant frequency. Surrounding the absorbing material 631 is an acoustic barrier 632, such as mass-loaded vinyl. Both materials are encapsulated within an outer housing 633. The transmission loss (TL) values ​​of these materials are approximately 24 at 360 Hz and approximately 29 at 675 Hz. Additional parameters for a preferred embodiment of the actuator 600 are provided in Table II below.

[0089] Figures 13a and 13b illustrate another embodiment of actuator 700, which comprises laminated stacked layers including two oscillating diaphragms 720a / 720b and a chamber layer 710 having a cavity 711 and an orifice 712. An acoustic nozzle 740 attached to the outer plane of the orifice 712 provides an extended airflow path into and out of the cavity 711. The acoustic nozzle 740 is adapted to reduce the acoustic level by providing an airflow path 741 as an extension of the cavity 712, the interior of which is formed an acoustic absorbing layer 742 and an acoustic substrate 743 made of a material having high absorption properties at one or more relevant acoustic frequencies. Suitable embodiments of highly absorbent acoustic materials include, but are not limited to, melamine and acoustic foam. The acoustic nozzle 740 also includes an outer ring 744 made of an acoustic barrier material for further attenuating the acoustic level. Additional parameters for a preferred embodiment of actuator 700 are provided in Table II below.

[0090] Figures 14a and 14b illustrate another embodiment of the actuator 800, which comprises a laminated stack of layers including two oscillating diaphragms 820a / 820b and a chamber layer 810 having a cavity 811 and an orifice 812. An acoustic nozzle 840 extends from the outer plane of the orifice 812 and provides an extended airflow path 841 for inflow into and outflow from the cavity 811. In this embodiment, the airflow path 841 of the acoustic nozzle 840 forms an expanded cavity 842 for attenuating the acoustic level. Additional parameters for preferred embodiments of the actuator 800 are provided in Table II below.

[0091] Figures 15a and 15b illustrate another embodiment of the actuator 900, which comprises a laminated stack of layers including two oscillating films 920a / 920b and a chamber layer 910 having a cavity 911 and an aperture 912. Figure 15a shows an exploded view of the actuator 900, with the chamber layer 910 divided into two halves 910-1 / 910-2, and the aperture 912 also divided into two halves 912-1 / 912-2. In this embodiment, the chamber layer 910 is provided with an integrated expansion chamber 940, which includes a baffle arrangement 941 embedded in the aperture 912 by forming an etched pattern in the two aperture halves 912-1 / 912-2 of Figure 15a. Figure 15b shows a close-up view of the aperture half 912-2, showing the baffle arrangement etched therein. The baffle arrangement 941 provides a buffering effect for the airflow through the orifice 912, which effectively reduces the acoustic level generated by the airflow. Additional parameters for the preferred embodiment of the actuator 900 are provided in Table II below.

[0092] Figures 16a and 16b illustrate another embodiment of the actuator 1000, which comprises laminated stacked layers including two oscillating membranes 1020a / 1020b and a chamber layer 1010 having a tilted chamber 1011 and an orifice 1012. Figure 16a omits a description of the top oscillating membrane 1020a to provide a more comprehensive view of the chamber 1011. In this embodiment, a tilted surface 1013 is formed on the boundary surface of the open volume of the chamber 1011 on the side opposite to the orifice 1012. The tilted surface 1013 eliminates dead zones and enhances the internal pressure distribution within the chamber 1011. The tilted surface 1013 optimizes the shape of the chamber 1011 to further correspond to the characteristics and actuation frequency of the oscillating membranes 1020a / 1020b. Specifically, the inclined surface 1013 is formed with opposing surfaces having a curvature corresponding to the maximum curvature generated in the membrane 1020a / 1020b when the membrane 1020a / 1020b is in maximum inward displacement toward the chamber 1011, although a slight offset has been provided to the inclined surface so that the membrane does not contact these surfaces, thereby avoiding friction that could lead to mechanical and thermal wear of the membrane. This configuration of the inclined surface 1013 reduces the volume of the internal chamber 1011 by removing stale air chamber portions that would normally be retained (not compressed into a jet), thereby enhancing the efficiency of the actuator and reducing noise levels and power consumption. Additional parameters for a preferred embodiment of the actuator 1000 are provided in Table II below.

[0093] Figure 17An embodiment of System 1 is shown, comprising an array of multiple actuators 200, each mounted on a common transport platform (e.g., a surface mounted for commercial applications). The actuators 200 are operated by a common arrangement of multi-channel drivers 10, a controller 20, and one or more sensors 30. Alternating current (AC) voltage is provided to each actuator 200 for individual phase adjustment to control the sound level generated at a distance greater than two wavelengths, where the waves are, in fact, plane waves. Phase control can be applied to the sound waves generated for each linear column of actuators 200, and the degree of acoustic benefit can be adjusted according to the phase coherence of System 1. If each driver has a different phase response, the acoustic benefit will not be as large as that of System 1 with drivers of similar phase. Through basic calculations, at a distance equivalent to two wavelengths, under perfect phase, System 1 can be controlled to produce zero acoustic levels. Achieving such an ideal result in reality is difficult due to challenges in aligning the drivers and also due to phase differences caused by inconsistencies in the manufacturing of the drivers. In an embodiment according to the invention, the phase difference between adjacent actuators 200 is adjusted according to a noise level measured as the driver scans different phase angles of each actuator 200 on two separate channels. While the system 1 discussed in this embodiment includes multiple actuators 200, it will be understood that system 1 may include multiple actuators of any type discussed herein, including combinations of multiple actuators of different types. Additional parameters for a preferred embodiment of system 1 are provided in Table II below.

[0094] The systems and methods according to the present invention, including systems employing one or more of the above embodiments, and systems combining two or more elements of the above embodiments, are capable of efficiently producing synthetic jet actuators that overcome the limitations of existing designs, including reducing the noise level generated by the jet velocity to a level previously considered impossible, as further detailed in Table 2 below.

[0095]

[0096] Although the present invention has been described with reference to specific embodiments, those skilled in the art will understand that the above disclosure is only about exemplary embodiments; the scope of the invention is not limited to the disclosed embodiments; the scope of the invention may include other embodiments with various changes and modifications to the embodiments disclosed herein without departing from the scope of the invention as defined by the appended claims and their equivalents.

[0097] While the foregoing embodiments omit description and / or discussion of certain elements discussed in other embodiments, it will be understood that each embodiment may include or be made to include elements from one or more other embodiments. For example, while some examples omit description of the polymer bonding layer and / or outer layer (as shown in Figure 2c and...) Figure 3 While the description and / or specific discussion of the polymeric bonding 222 and outer layer 224 are provided herein, it is understood that each embodiment discussed herein may include these elements. Similarly, although some embodiments are discussed with configurations having only a single chamber layer (having a single chamber and an orifice), it is understood that it is also conceivable that each embodiment discussed herein may include multiple chamber layers, each with a corresponding chamber and orifice (e.g., each embodiment of Figures 10 to 16 is illustrated as having a single chamber layer, and each embodiment of Figures 10 to 16 may include multiple chamber layers as illustrated in the embodiment of Figure 9). Furthermore, although the above embodiments are discussed with respect to airflow, it will be understood that the jet actuator according to the invention is not limited to the generation of air and airflow and can be used with any suitable fluid to generate a corresponding fluid flow.

[0098] All publications, patents, and patent applications mentioned herein are expressly incorporated herein by reference to the extent necessary for understanding or fulfilling the disclosure of this invention, to the same extent as each individually incorporated. No express or implied license is granted to any patent incorporated herein.

[0099] This invention is not limited to the exemplary embodiments described herein, but is characterized by the appended claims, which do not limit the scope of this disclosure.

Claims

1. A synthetic jet actuator, comprising: A first chamber layer, the first chamber layer comprising: A body having a first planar surface and a second planar surface, an outer perimeter and an inner perimeter, the inner perimeter defining a first chamber for receiving a fluid volume; as well as An orifice is provided for fluid communication between the first chamber and the external atmosphere; as well as A first oscillating membrane, comprising a piezoelectric material adapted to deflect in response to an electrical signal, wherein... The first chamber has an opening on at least one planar surface of the first chamber layer, and the first oscillating membrane is positioned adjacent to the planar surface having the chamber opening and is adapted to serve as a closing surface for the chamber opening. The first oscillating diaphragm is adapted to compress and expand the volume within the first chamber based on deflection generated by the piezoelectric material, so as to generate fluid flow between the first chamber and the external atmosphere through the orifice. The first chamber layer and the first oscillating diaphragm are connected by an adhesive material. An acoustic nozzle is positioned outside the orifice of the first chamber layer and is adapted to extend the flow path for fluid inflow and outflow from the orifice. The acoustic nozzle includes an outer ring made of an acoustic barrier material, within which are disposed an acoustic substrate and an acoustic absorption layer. The acoustic substrate is positioned outside an extended flow path provided to the orifice of the first chamber layer, while the acoustic absorption layer is positioned outside the acoustic substrate.

2. The synthetic jet actuator according to claim 1, wherein... The adhesive material includes at least one of the following: an adhesive film positioned between the first chamber layer and the first oscillating membrane, and an adhesive liquid applied to the surface of at least one of the first chamber layer and the first oscillating membrane.

3. The synthetic jet actuator according to claim 1, wherein: The first oscillating membrane includes a substrate with a piezoelectric material attached to the substrate by a bonding material.

4. The synthetic jet actuator according to claim 3, wherein: The substrate and bonding material are conductive, and the substrate and bonding material are adapted to act as electrical connections for supplying electrical power to the piezoelectric material.

5. The synthetic jet actuator according to claim 4, wherein: The electrical connection is configured to provide a non-uniform spatial coverage on the piezoelectric material, causing the first oscillating membrane to undergo anisotropic deflection.

6. The synthetic jet actuator according to claim 3, wherein: The substrate has a high storage modulus and a low loss modulus, as well as an angle tangent of less than 0.

5.

7. The synthetic jet actuator according to claim 1, wherein... The first oscillating membrane is positioned such that the central axis of the first oscillating membrane is aligned with the central axis of the first chamber in the first chamber layer.

8. The synthetic jet actuator according to claim 7, wherein... The central axis of the piezoelectric material is aligned with the central axis of the first chamber in the first chamber layer.

9. The synthetic jet actuator according to claim 1, wherein: The first chamber layer includes an expansion chamber embedded within the orifice, the expansion chamber including a series of baffles for buffering fluid flow through the orifice.

10. The synthetic jet actuator according to claim 1, wherein: The boundary surface of the first chamber of the first chamber layer includes one or more inclined surfaces having a predetermined curvature corresponding to the curvature of the first oscillating membrane in a deflected compression state, for minimizing the volume within the first chamber, the volume of the first chamber being predetermined to correspond to stagnant fluid flow.

11. The synthetic jet actuator according to claim 1, wherein: The first oscillating membrane is adapted to be in a prestressed state such that, in the unenergized state, the first oscillating membrane remains on a neutral axis that provides a slightly expanded state for the first chamber of the first chamber layer, and such that the first oscillating membrane is forced to buckle when deflected into a compressed state in the piezoelectric material under energized conditions.

12. The synthetic jet actuator according to claim 11, wherein: The first oscillating diaphragm is adapted to have a prestress of at least 0.01 inches.

13. The synthetic jet actuator according to claim 1, wherein: The actuator is configured to generate a jet velocity greater than 50 m / s at a resonant frequency below 500 Hz.

14. The synthetic jet actuator according to claim 13, wherein: The actuator is configured to generate a jet velocity greater than 50 m / s up to 100 m / s in the resonant frequency range of 150 Hz to 475 Hz.

15. The synthetic jet actuator according to claim 1, further comprising: The second oscillating membrane includes a piezoelectric material adapted to deflect in response to an electrical signal, wherein... The first chamber of the first chamber layer is formed as a through-hole extending through the entire first chamber layer, and the first chamber has two openings on opposite planar surfaces of the first chamber layer. The first oscillating diaphragm is positioned adjacent to a first planar surface of the first chamber layer having a first chamber opening, and is adapted to serve as a closing surface for the first chamber opening. The second oscillating diaphragm is positioned adjacent to a second planar surface of the first chamber layer having a second chamber opening, and is adapted to serve as a closing surface for the second chamber opening. Both the first and second oscillating membranes are adapted to compress and expand the volume within the first chamber based on the deflection generated in each oscillating membrane by the respective piezoelectric material, in order to generate fluid flow between the first chamber and the external atmosphere through the orifice.

16. The synthetic jet actuator according to claim 15, wherein... The first and second oscillating membranes are both positioned such that the central axis of the respective oscillating membrane is aligned with the central axis of the first chamber in the first chamber layer.

17. The synthetic jet actuator according to claim 16, wherein... The central axis of the piezoelectric material of the corresponding oscillating membrane is aligned with the central axis of the first chamber in the first chamber layer.

18. The synthetic jet actuator according to claim 1, further comprising: The second chamber layer includes a second chamber for receiving a volume of fluid, and an orifice providing fluid communication between the second chamber and the external atmosphere; The second oscillating membrane includes a piezoelectric material adapted to deflect the second oscillating membrane in response to an electrical signal; as well as A third oscillating membrane, comprising a piezoelectric material adapted to deflect in response to an electrical signal, wherein... The chambers in both the first and second chamber layers are formed as through-holes that pass through the entire corresponding chamber layer, and each chamber has two openings on the opposite plane surface of the corresponding chamber layer. The first oscillating diaphragm is positioned adjacent to a first planar surface of the first chamber layer having a first chamber opening in the first chamber layer, and is adapted to serve as a closing surface for the first chamber opening of the chamber in the first chamber layer. The second oscillating diaphragm is positioned adjacent to a second planar surface of the first chamber layer having a second chamber opening in the first chamber layer and adjacent to a first planar surface of the second chamber layer having a first chamber opening in the second chamber layer, and is adapted to serve as a closing surface for the second chamber opening of the first chamber in the first chamber layer and the first chamber opening of the second chamber in the second chamber layer. The third oscillating membrane is positioned adjacent to a second planar surface of the second chamber layer having a second chamber opening in the second chamber layer, and is adapted to serve as a closing surface for the second chamber opening of the chamber in the second chamber layer. Both the first and second oscillating films are adapted to compress and expand the volume within the first chamber of the first chamber layer based on the deflection generated in each oscillating film by the corresponding piezoelectric material, thereby generating fluid flow between the first chamber and the external atmosphere through the orifice. Both the second and third oscillating membranes are adapted to compress and expand the volume within the second chamber of the second chamber layer based on the deflection generated in each oscillating membrane by the respective piezoelectric material, thereby generating fluid flow between the second chamber and the external atmosphere through the orifice.

19. The synthetic jet actuator according to claim 18, wherein... The second oscillating membrane is adapted to expand the volume inside the second chamber of the second chamber layer while compressing the volume inside the first chamber layer, or to compress the volume inside the second chamber layer while expanding the volume inside the first chamber layer.

20. The synthetic jet actuator according to claim 1, further comprising: The second chamber layer includes a second chamber for receiving a volume of fluid, and an orifice providing fluid communication between the second chamber and the external atmosphere. The chambers in both the first and second chamber layers are formed as blind holes, with a single opening only on one planar surface of the respective chamber layer. The first oscillating diaphragm is located between the first chamber layer and the second chamber layer, adjacent to the planar surface of the first chamber layer having the chamber opening of the first chamber in the first chamber layer, and adjacent to the planar surface of the second chamber layer having the chamber opening of the second chamber in the second chamber layer. The first oscillating diaphragm is adapted to compress and expand the volume within the first chamber of the first chamber layer, and to compress and expand the volume within the second chamber of the second chamber layer.

21. The synthetic jet actuator according to claim 20, wherein... The first oscillating membrane is adapted to expand the volume inside the second chamber of the second chamber layer while compressing the volume inside the first chamber layer, and is also adapted to compress the volume inside the second chamber layer while expanding the volume inside the first chamber layer.

22. The synthetic jet actuator according to claim 1, further comprising: An acoustic enclosure is disposed outside the first chamber layer and the first oscillating diaphragm to suppress noise generated by the first oscillating diaphragm.

23. The synthetic jet actuator according to claim 22, wherein: The acoustic enclosure includes an outer shell with an absorbing material and an acoustic barrier positioned within the outer shell. The absorbing material is positioned outside the first oscillating diaphragm, and the acoustic barrier is positioned outside the absorbing material.

24. The synthetic jet actuator according to claim 1, wherein: The acoustic nozzle is an integrally integrated component of the first chamber layer, and the flow path provided within the acoustic nozzle includes a flow expansion chamber.

25. A method of manufacturing an actuator according to claim 1, the method comprising: The first oscillating diaphragm is positioned adjacent to the planar surface of the first chamber layer having a chamber opening, and the first oscillating diaphragm and the first chamber layer are connected by an adhesive material.

26. The method of claim 25, further comprising: The first oscillating film is formed by attaching the piezoelectric material to the substrate.

27. The method of claim 25, further comprising: During the assembly process, the first oscillating diaphragm is subjected to prestress through thermoforming.

28. The method of claim 27, wherein: The thermoforming of the first oscillating diaphragm is performed by voltage compression.

29. The method of claim 25, further comprising: During the assembly process, the piezoelectric material is electrically actuated to apply prestress to the first oscillating diaphragm.

30. The method of claim 25, further comprising: An independent mass structure is positioned within the first oscillating membrane, adjacent to the piezoelectric material.

31. The method of claim 30, further comprising: The individual mass structures are attached to the piezoelectric material using an adhesive.

32. The method of claim 25, further comprising: A vacuum pressure is generated to apply uniform atmospheric pressure, thereby pressing the first chamber layer and the first oscillating membrane together.

33. The method of claim 32, further comprising: The first chamber layer and the first oscillating membrane are thermo-cured while uniform atmospheric pressure is applied.

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