Patent Application
20140284325
Solid state flow control devices are in high demand for moderate to high flow speeds. Such devices can have several important applications. Current solid state flow control devices operate using arc filament and/or arc heating flow control methods. These methods require a high amount of energy and lead to high manufacturing costs.
Embodiments of the subject invention relate to solid state flow control devices, methods of manufacturing the same, and methods of using the same. A solid state flow control device can include a set of electrodes separated by a dielectric material.
Embodiments of the subject invention also to solid state heating sources, methods of manufacturing the same, and methods of using the same. A solid state heating source can include a set of electrodes separated by a dielectric material.
Embodiments of the subject invention also relate to plasma actuators, methods of manufacturing the same, and methods of using the same. A plasma actuator can include a set of electrodes separated by a dielectric material.
In an embodiment, a plasma actuator can include: a dielectric material; at least one powered electrode in contact with the dielectric material; and at least one grounded electrode in contact with the dielectric material. The at least one powered electrode and the at least one grounded electrode can be electrically separated from each other by the dielectric material, and the dielectric material can be a ferroelectric material. A solid state flow control device or a solid state heating source can include such a plasma actuator.
In another embodiment, a method of fabricating a plasma actuator can include: forming at least one ground electrode; forming a dielectric material; and forming at least one power electrode. The at least one ground electrode and the at least one power electrode can be electrically separated from each other by the dielectric material, and the dielectric material can be a ferroelectric material.
In another embodiment, a method of generating heat can include: providing a plasma actuator including at least one powered electrode in contact with a dielectric material and at least one grounded electrode in contact with the dielectric material; and applying a voltage potential, with respect to the at least one grounded electrode, to the at least one powered electrode. The at least one powered electrode and the at least one grounded electrode can be electrically separated from each other by the dielectric material, and the dielectric material can be a ferroelectric material.
In another embodiment, a plasma actuator can include: a dielectric material; at least one powered electrode in contact with the dielectric material; and at least one grounded electrode in contact with the dielectric material. The at least one powered electrode and the at least one grounded electrode can be electrically separated from each other by the dielectric material, and the dielectric material can be a silica aerogel. A solid state flow control device or a solid state heating source can include such a plasma actuator.
In another embodiment, a method of fabricating a plasma actuator can include: forming at least one ground electrode; forming a dielectric material; and forming at least one power electrode. The at least one ground electrode and the at least one power electrode can be electrically separated from each other by the dielectric material, and the dielectric material can be a silica aerogel.
In another embodiment, a method of generating heat can include: providing a plasma actuator including at least one powered electrode in contact with a dielectric material and at least one grounded electrode in contact with the dielectric material; and applying a voltage potential, with respect to the at least one grounded electrode, to the at least one powered electrode. The at least one powered electrode and the at least one grounded electrode can be electrically separated from each other by the dielectric material, and the dielectric material can be a silica aerogel.
This patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.
When the terms “on” or “over” are used herein, when referring to layers, regions, patterns, or structures, it is understood that the layer, region, pattern or structure can be directly on another layer or structure, or intervening layers, regions, patterns, or structures may also be present. When the terms “under” or “below” are used herein, when referring to layers, regions, patterns, or structures, it is understood that the layer, region, pattern or structure can be directly under the other layer or structure, or intervening layers, regions, patterns, or structures may also be present. When the term “directly on” is used herein, when referring to layers, regions, patterns, or structures, it is understood that the layer, region, pattern or structure is directly on another layer or structure, such that no intervening layers, regions, patterns, or structures are present.
When the term “about” is used herein, in conjunction with a numerical value, it is understood that the value can be in a range of 95% of the value to 105% of the value, i.e. the value can be +/−5% of the stated value. For example, “about 1 kg” means from 0.95 kg to 1.05 kg.
Embodiments of the subject invention relate to solid state flow control devices, methods of manufacturing the same, and methods of using the same. A solid state flow control device can include a set of electrodes separated by a dielectric material.
Embodiments of the subject invention also to solid state heating sources, methods of manufacturing the same, and methods of using the same. A solid state heating source can include a set of electrodes separated by a dielectric material.
Embodiments of the subject invention also relate to plasma actuators, methods of manufacturing the same, and methods of using the same. A plasma actuator can include a set of electrodes separated by a dielectric material.
Solid state flow control devices and heating sources according to embodiments of the subject invention can use an electrically-driven plasma source (e.g., a plasma actuator) such that the heat generation can be strongly dependent upon the frequency of an applied electric potential. This can provide a low-cost alternative to are filament and are heating flow control methods due to decreased energy budget and decreased manufacturing costs.
In embodiments of the present invention, a solid state flow control device or solid state heating source can include at least one plasma actuator. Each plasma actuator can include a set of electrodes separated by a dielectric material. In an embodiment, at least one of the electrodes can be grounded. The remaining one or more electrodes can be configured to have a voltage applied, and the voltage can be either direct current (DC) or alternating current (AC). The plasma actuator can incorporate, or be configured to connect to, a power source. At least one electrode of the plasma actuator can be connected to, or configured to connect to, the power source. In an embodiment, the voltage applied, with respect to the grounded electrode(s), across each of the non-grounded electrodes can be the same. In an alternative embodiment, the voltage applied, with respect to the grounded electrode(s), across the non-grounded electrodes can vary.
In many embodiments, one or more non-grounded electrodes can be separated from one or more grounded electrodes by a dielectric material. The dielectric material can be a material with high permittivity, though embodiments are not limited thereto. The vacuum (air) permittivity (ε0) is 8.85×10−12 Farad/meter. The relative permittivity (also referred to as the dielectric constant) of a material is the permittivity of the material divided by the vacuum permittivity. Materials with high relative permittivity (e.g., >10) become highly polarizable and hence exhibit a phenomenon referred to as spontaneous electron emission. The particles spin under alternating electric field and rapidly generate heat as a function of the applied frequency. Such a material is good for polarization heating of a surface (not Joule heating) even at low voltages (e.g., 100 s of V). Materials with low relative permittivity (e.g., <2) transfer energy very efficiently with minimal dielectric heating loss. A very high voltage (for example, based on thickness, 60 kV across a 6 mm thick silica aerogel) with minimal to no damage to the material. This can advantageously induce high thrust per weight of the actuator material.
In an embodiment, a plasma actuator can include a dielectric material that has a dielectric constant of at least 10 or greater than 10. For example, the dielectric material can have a dielectric constant of at least 100, at least 1,000, or at least 10,000. In a specific embodiment, the dielectric material is in the range of slightly above 1 (free space) to 15,000, 1.001 to 15,000, 1.01 to 15,000, 1.1 to 15,000, 10 to 15,000, 100 to 15,000, 1000 to 15,000, 10,000 to 15,000, 10 to 100, 10 to 1000, 10 to 10,000, 100 to 1000, 100 to 10,000, 1000 to 10,000, 10 to 15,000, 100 to 15,000, 1000 to 15,000, or greater than 15,000. In an alternative embodiment, a plasma actuator can include a dielectric material that has a dielectric constant of no more than 2 or less than 2.
The dielectric material can be, for example, a ferroelectric material, hafnium oxide, an aerogel, a silica aerogel, an organic aerogel (e.g., Resorcinol-Formaldehyde), a metal oxide based aerogel, or a carbon aerogel. In an embodiment, the dielectric material can be a ferroelectric material. Examples of ferroelectric materials that can be as the dielectric material with respect to embodiments of the invention include, but are not limited to, Lead Zirconate Titanate (PZT), Barium Titanate (BT), Lead Titanate (PT), Lead Lanthanum Zirconate Titanate (PLZT), Lead Magnesium Niobate (PMN). In a further embodiment, the dielectric material can be a very high permittivity ferroelectric material. In a further embodiment, the dielectric material can be a silica aerogel. Numerous open sources online may be found that describe the material properties of silica aerogel, as well as how to make these materials. Silica aerogels in general consist or a complex microstructure of silicon dioxide in which air occupies a majority of the volume. In a further embodiment, the dielectric material can be an acrylic material. In a further embodiment, the dielectric material can be Kapton.
The dielectric material can have any reasonable thickness separating the electrodes. In an embodiment the thickness of the dielectric material (and the distance by which at least one grounded electrode is separated from at least one powered electrode) can be any internal range within the endpoints of 0.01 mm and 15 mm. In an embodiment, the thickness of the dielectric material can be in a range of from 0.1 mm to 10 mm. In a further embodiment, the thickness of the dielectric material can be in a range of from 0.15 mm to 8 mm. In a further embodiment, the thickness of the dielectric material can be in a range of from 0.17 mm to 6 mm. For example, the thickness of the dielectric material can be 0.17 mm, 1.5 mm, 3.0 mm, 4.6 mm, or 6.0 mm.
In an embodiment, a powered electrode can be aligned with a grounded electrode in at least one direction. In a further embodiment, a powered electrode can be non-aligned with a grounded electrode in at least one direction. In a further embodiment, a powered electrode can be aligned with a grounded electrode in at least one direction and can be non-aligned with a grounded electrode in at least one direction.
Referring to
In an embodiment, the voltage potential applied to one or more powered electrodes, with respect to one or more grounded electrodes, can be an AC signal. The frequency of an applied signal can be any reasonable frequency. In an embodiment, the frequency of an applied signal can be any internal range within the endpoints of 0.1 kHz and 15 GHz. For example, the frequency of an applied signal can be in a range of from 0.1 kHz to 1 GHz. In an embodiment, the frequency of an applied signal can be in a range of from 0.1 kHz to 10 MHz. In a further embodiment, the frequency of an applied signal can be in a range of from 0.1 MHz to 10 MHz. In a further embodiment, the frequency of an applied signal can be in a range of from 0.1 kHz to 20 kHz. For example, the frequency of an applied signal can be 0.1 kHz, 0.5, kHz, 1 kHz, 5 kHz, 14 kHz, or 15 kHz.
The amplitude of an applied signal can be any reasonable amplitude. In an embodiment, the amplitude of an applied signal can be any internal range within the endpoints of 0 V peak-to-peak (pp) and 200 kVpp. For example, the amplitude can be in a range of from 1.5 kVpp to 150 kVpp. In an embodiment, the amplitude can be in a range of from 1.5 kVpp to 36 kVpp. In a further embodiment, the amplitude can be in a range of from 1.5 kVpp to 30 kVpp. For example, the amplitude of an applied signal can be 1.5 kVpp, 2.5 kVpp, 3.0 kVpp, 3.5 kVpp, or 4.0 kVpp. The amplitude of an applied signal can also be expressed as a ratio of the thickness of the dielectric material. In an embodiment, the amplitude of an applied signal can be any internal range within the endpoints of 0 Vpp/cm of thickness of the dielectric material and 300 kVpp/cm. In an embodiment, the amplitude can be in a range of from 20 kVpp/cm to 60 kVpp/cm.
In an embodiment, the voltage potential applied to one or more powered electrodes, with respect to one or more grounded electrodes, can be applied in a duty cycle. A duty cycle can advantageously minimize the power requirement. In each cycle of the duty cycle, the voltage potential can be applied for one or more portions of the cycle and not applied for the other portions of the cycle. For example, the voltage potential can be applied as a repeating cycle of one or more pulses. The duration of the one or more portions of the cycle in which the voltage potential is applied can be any internal range within the endpoints of 10% of the duration of the cycle to 90% of the duration of the cycle. For example, the duration of the one or more portions of the cycle in which the voltage potential is applied can be from 20% of the duration of the cycle to 50% of the duration of the cycle. In an embodiment, the duration of the one or more portions of the cycle in which the voltage potential is applied can be about 25% of the duration of the cycle. In a particular embodiment, a 5 kHz, 10 kV (peak-to-peak) voltage potential can be applied in a pulsing duty cycle in which the duration of the one or more portions of the cycle the voltage potential is applied is about 25% of the duration of the cycle.
In an embodiment, at least one electrode of a plasma actuator can be encapsulated by a material, for example, by the dielectric material, a separate dielectric material, an epoxy material, and/or electrical tape. At least one electrode can be exposed to the environment. In certain embodiments, the encapsulated electrode(s) can be grounded, and the exposed electrode(s) can be powered.
Each electrode can be made from any suitable material known in the art. For example, each electrode can include one or more of the following materials: copper, aluminum, gold, silver, platinum, indium tin oxide, indium zinc oxide, aluminum tin oxide, aluminum zinc oxide, calcium, magnesium, carbon nanotubes, silver nanowire, LiF/Al/ITO, Ag/ITO, and CsCO3/ITO.
The electrode set for a plasma actuator can have any reasonable configuration. In various embodiments, a plasma actuator can include an electrode set having a linear, triangular, square, rectangular, serpentine, circular, oval, or other curved or polygonal shape.
In an embodiment, a method of fabricating a plasma actuator can include: forming at least one ground electrode; forming a dielectric material; and forming at least one power electrode. The at least one ground electrode and the at least one power electrode can be electrically separated from each other by the dielectric material, and the dielectric material can be a ferroelectric material. Each power electrode can be configured to connect to a power source and/or can be connected to a power source.
In an embodiment, a method of generating heat can include: providing a plasma actuator including at least one powered electrode in contact with a dielectric material and at least one grounded electrode in contact with the dielectric material; and applying a voltage potential, with respect to the at least one grounded electrode, to the at least one powered electrode. The at least one powered electrode and the at least one grounded electrode can be electrically separated from each other by the dielectric material, and the dielectric material can be a ferroelectric material.
In an embodiment, a method of fabricating a plasma actuator can include: forming at least one ground electrode; forming a dielectric material; and forming at least one power electrode. The at least one ground electrode and the at least one power electrode can be electrically separated from each other by the dielectric material, and the dielectric material can be a silica aerogel. Each power electrode can be configured to connect to a power source and/or can be connected to a power source.
In an embodiment, a method of generating heat can include: providing a plasma actuator including at least one powered electrode in contact with a dielectric material and at least one grounded electrode in contact with the dielectric material; and applying a voltage potential, with respect to the at least one grounded electrode, to the at least one powered electrode. The at least one powered electrode and the at least one grounded electrode can be electrically separated from each other by the dielectric material, and the dielectric material can be a silica aerogel.
Following are examples that illustrate procedures for practicing the invention. These examples should not be construed as limiting.
Referring to
Two thin (70 μm) copper electrodes were placed asymmetrically on either side of a dielectric material with no horizontal displacement between the two electrodes. The dielectric was a 3 mm thick (t) sheet of ferroelectric material which had a nominal relative dielectric constant of 1750. The dimensions of ferroelectric sample were 40×12 (x, y) mm. The exposed and encapsulated electrodes were each 5 mm wide and the thickness of the material was 3 mm. Both electrodes had a length, l, of 12 cm. Standard electrical tape in combination with epoxy covered the encapsulated electrode to avert an unwanted discharge on the lower surface. Similarly, an 84 μm-thick piece of Kapton was placed on the backside of the exposed electrode. A high voltage amplifier (Trek 30/20C) was used.
The ferroelectric material advantageously allowed for the ignition of discharge at a much lower input voltage compared to materials of the same thickness with lower dielectric constants.
Attempts were made to apply higher voltages to the actuator, however dielectric heating became an issue with temperatures reaching ˜300° C. after only 10's of seconds of operation. Since the thrust produced is directly tied to voltage, over the range of tested inputs (1.5 to 4.0 kVpp at 5 kHz), no significant force was measured.
With no force being achieved, the dielectric heating of the device was investigated. A Flir A320 infrared camera was used. The camera has a spectral range of 7.5-13 μm and pixel resolution of 320×240 pixels. The ambient humidity (55% RH), distance from actuator (0.33 m), and material emissivity were all considered in determining the surface temperature. The ferroelectric's emissivity was found to be 0.96±0.02 and was determined by heating the dielectric to a uniform temperature and comparing the cameras readout with a surface mounted thermocouple. Temperature measurements were made over a range of voltages (1.5 to 4.0 kVpp) at 5.0 kHz as well as over a range of frequencies (DC to 14 kHz) at 3.5 kVpp.
Noting the seemingly strong dependence on frequency, a plot of the temperature rise after 300 seconds (x=12.5 mm, y=1.5 mm) as a function of power shows a linear relationship proportional to 0.87° C. (
Silica aerogel, having an extremely low dielectric constant, was used as a dielectric material. Silica aerogels in general consist of a complex microstructure of silicon dioxide in which air occupies a majority of it volume. For the samples tested, ˜95% of the dielectric's volume was air resulting a density ranging from 0.04 to 0.12 g cm−3 with results being reported for samples closer to the lower bounds. Although not measured experimentally, silica aerogels for this range of densities have a dielectric constant of ˜1.1.
An added benefit of the aerogel is its low density, a parameter that would be critical when applying these actuators to, for example, medium to small/micro air vehicles.
A caveat however of increasing the dielectrics thickness is that the weight of the actuator also increases. Although this would be of little consequence for large scale applications, it could prove detrimental for medium to small/micro air vehicles wanting to benefit from the increased body force associated thicker dielectrics.
For the typical dielectrics tested (Kapton and acrylic), a thinner dielectric is clearly beneficial based on a force-to-weight basis. However, when the silica aerogel is considered (ρ=0.06 g cm−3), the benefits of this extremely low density material are clearly shown in
All patents, patent applications, provisional applications, and publications referred to or cited herein, and/or listed in the References section, are incorporated by reference in their entirety, including all figures and tables, to the extent they are not inconsistent with the explicit teachings of this specification.
It should be understood that the examples and embodiments described herein arc for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application.
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This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/500,967, filed Jun. 24, 2011, the disclosure of which is hereby incorporated by reference in its entirety, including any figures, tables, or drawings.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US2012/043947 | 6/25/2012 | WO | 00 | 3/31/2014 |
| Number | Date | Country | |
|---|---|---|---|
| 61500967 | Jun 2011 | US |
