WAVE-DRIVEN BLOWER AND ELECTRIC MOTOR/GENERATOR

TECHNICAL FIELD

The present invention is related to the field of heat transfer, and more particularly to production of airflow across heat transfer surfaces, and to the field of electric motors and generators.

BACKGROUND ART

This application claims the benefit of U.S. provisional application 61/393,138, filed Oct. 14, 2010, which is incorporated herein by reference.

Previous inventions for creating airflows and for cooling electronic devices have used electric fans to increase airflows thorough cooling fins. U.S. Pat. No. 7,647,960 and U.S. Pat. No. 7,701,718 describe a means for heat dissipation using separate cooling fins and electric fans to remove heat. Piezoelectric or otherwise electroactuated fans and pumps use mechanical traveling waves or peristaltic action to generate flows. U.S. Pat. No. 5,192,197 and U.S. Pat. No. 5,961,298 describe generating flows from macroscopic motions of the surfaces of chambers that progress as traveling waves. All prior approaches require moving parts, with consequent expense, noise, power, and volume requirements that can be undesirable.

Previous inventions have used piezoelectric actuators to generate rotational motion or to produce electrical power in piezoelectric motors. U.S. Pat. No. 6,744,176 describes a means for transmitting the vibratory movement to which the stator is subjected are arranged on the rotor, this transmission means being formed by deflectable tongues, which can be deformed elastically. U.S. Pat. No. 7,576,474 describes a piezoelectric motor for generating an elliptic motion by adding a longitudinal vibration to a bending-direction vibration is provided. U.S. Pat. No. 7,696,673 describes devices in which a non-piezoelectric resonating element is configured to oscillate and dissipate mechanical energy into a piezoelectric element, which converts a portion of such mechanical energy into electricity and therefore acts as a generator. Additionally, it describes a piezoelectric element that is configured to drive one or more mechanical elements operably coupled to the one or more non-piezoelectric resonating elements, and therefore acts as a motor. Furthermore, it describes a piezoelectric element that is operably coupled to a non-piezoelectric resonating element to form an electrical transformer. These three patents describe variations of conventional piezoelectric motors that use piezoelectric actuators to generate vibrations or wave motion, which interacts with a rotor to produce rotation or extract electrical power from sending vibrations into piezoelectric actuators. In none of these are piezoelectric actuators used to regulate magnetic reluctance or to drive a magnetically powered electric motor or generator.

Switched reluctance motors and generators are in wide use. U.S. Pat. No. 3,984,711 describes variable reluctance step motors of the type in which a rotor member is rotatable stepped relative to a stator member by magnetic flux produced as a result of the simultaneous energization of adjacent windings, which extend around circumferentially spaced pole pieces on one of the members. U.S. Pat. No. 7,459,812 describes a switched reluctance motor capable of reducing the number of assembling processes by simplifying a structure and safely protecting a winding coil. U.S. Pat. No. 7,781,931 describes a switched reluctance motor capable of reducing torque ripple and vibration noise. These three use coils to carry current to generate magnetic fields. This use of current-carrying wires in these devices introduces problems of heat generation, added weight and expense.

DISCLOSURE OF INVENTION

Previous devices for generating fluid flow or airflow use mechanical motions, such as spinning blades, bellows, or surface motions to generate flows or they use electrohydrodynamic processes to move charged particles which in turn accelerate flows. The use of waves without moving parts or electrohydrodynamic processes to produce fluid flows has not been used in any earlier inventions.

Embodiments of the present invention provide a wave-driven blower, which can accelerate or decelerate airflows or other fluid flows using waves. As an example, the driving waves can be thermal waves produced by varying the temperature of regions of a surface. The thermal wave moves along the surface as some regions are made cooler and others are made hotter. This motion of the wave pattern can be produced without any physical motion of any parts of the surface. Even though there is no material motion, the velocity of the surface-thermal wave entrains the fluid near the surface and imparts a velocity to the fluid. Other types of waves, in addition to thermal waves, can generate fluid flow. As examples, waves can be produced by variations in chemical composition, ionic concentration, chemical potential, total pressure, partial pressure and surface texture.

Embodiments of the present invention can also provide as wave-driven generator. A flowing fluid such as air can be used to amplify wave motions in the device. The wave motions in turn can generate power, for example electrical power.

Embodiments of the present invention, which use piezoelectric actuators to regulate magnetic reluctance, can drive a magnetically powered electric motor or generator efficiently and with high power density. Embodiments of the present invention eliminate current carrying coils and significantly mitigate the problems with prior motor/generators. Piezoelectrically actuated, reluctance-switched (PARS) generators and motors according to the present invention provide important advantages over conventional electrical generators and motors. PARS generators and motors are unique in using piezoelectric actuators to modulate magnetic reluctance and in harnessing this effect to generate electrical power or mechanical motion. This approach leads to PARS generators and motors having attractive features not common in more conventional generators and motors: (1) The PARS generators and motors can have low mass because the piezoelectric actuators have high power densities. (2) The hysteresis losses in the piezoelectric material can be a few percent of the power generated. (3) In the PARS generator or motor architecture, such as that shown in FIG. 21, below, the piezoelectric actuators can be situated in the periphery of the generator or motor allowing the heat to be easily removed from the device, preventing overheating. (4) Since PARS devices have no current-carrying coils of wires, winding losses are eliminated. (5) The small thickness of the reluctance switch layers (see FIG. 16) and the rotor-attractor plates (see FIGS. 18-19) minimizes eddy current losses in the rotor and stator. (6) Heating of permanent magnets, and the resulting demagnetization are a concern in conventional motors and generators. In PARS motors and generators, the permanent magnetic can be located in a region far from the piezoelectric actuators where most of the heat is generated. (7) Conventional motors that use permanent magnets have safety issues because voltages are produced whenever the rotor is spinning, regardless of whether output power is desired. PARS generators do not have this safety issue, since they only produce power when the actuated is activated.

The PARS architecture enables many possibilities for electric generators and electric motors from low power devices to high power devices. Additionally, the PARS architecture can be used for very precise stepper motors and for motors with highly controlled speeds or torques. Applications include small battery-operated motors, large industrial motors, generators for aircraft, and multi-MW electric generators for power plants.

These and other aspects of the present invention will become apparent to those skilled in this art upon reading the accompanying description, drawings, and claims set forth herein.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic illustration of a surface with a plurality of regions disposed thereon.

FIG. 2(
a,b,c) provide schematic illustrations of the motion of a surface thermal wave with a rectangular profile moving across a surface.

FIG. 3(
a,b,c) provide schematic illustrations of the motion of a three-level surface thermal wave moving across a surface.

FIG. 4 illustrates the generation of fluid motion through the channels formed by several surfaces with surface thermal waves.

FIG. 5(
a,b) is a schematic illustration of the use of surfaces thermal waves in channels to remove heat from an object.

FIG. 6(
a,b) is a schematic illustration of the use of surfaces thermal waves on a surface to remove heat from an object.

FIG. 7 is a sketch of a single heat fin.

FIG. 8 is a schematic illustration of an insulating gasket.

FIG. 9 is a schematic illustration of a single heat switch electrode and an electrically conducting wire emanating from it.

FIG. 10 shows a set of electrodes each with it own connecting wire.

FIG. 11 is an exploded view of the solid components of a heat fin with a liquid-crystal based thin film heat switch.

FIG. 12 is a schematic illustration of an assembled heat fin with a liquid-crystal based thin-film heat switch.

FIG. 13 is schematic illustration of a set of heat fins with thin-film heat switches on their interior walls connected to the base of a heat sink.

FIG. 14 is a block diagram of a piezoelectrically-actuated reluctance-switched (PARS) generator.

FIG. 15 is a schematic depiction of a sliding teeth reluctance switch with one moveable layer.

FIG. 16(
a, b) is a schematic depiction of a sliding teeth reluctance switch with multiple moveable layers.

FIG. 17 is a schematic depiction of a driver unit with a permanent magnetic, reluctance switch, and rotor gaps.

FIG. 18 is a schematic depiction of a single rotor disk with symmetric tapered rotor-gap plates.

FIG. 19 is a schematic depiction of a single rotor disk with one-sided feathered rotor-gap plates.

FIG. 20 is a schematic depiction of multiple rotor disks with one driver unit.

FIG. 21 is a schematic depiction of a full PARS motor or generator with multiple rotor disks and drivers units.

MODES FOR CARRYING OUT THE INVENTION AND INDUSTRIAL APPLICABILITY

Wave-Driven Blower. FIG. 1 is a schematic illustration of a surface with a plurality of regions disposed thereon. A substrate 101 can comprise any rigid material such as aluminum, copper, iron, ceramic, and polymer. A surface of the substrate 101 can have a plurality of regions 111-122 disposed on it. In the figure, the each region extends across a first dimension of the surface, and the regions are disposed in a sequence across a second dimension of the surface. Other arrangements of regions can also be suitable. The regions 111-122 have a characteristic that is controllable. For ease of description, it will be assumed that the temperature of the regions can be controlled, although other characteristics can also be suitable; examples are described elsewhere herein. In operation, the temperatures of the regions can be controlled so that there is a nonconstant temperature profile across the second dimension of the surface. For example, each region can be controlled so that there is a roughly sinusoidal temperature profile. The regions can then be controlled so that the sinusoidal profile moves across the surface, for example from left to right. Air or another fluid near the regions will encouraged to move across the surface by the temperature profile; the moving profile keeps the fluid moving and accordingly generates continuous fluid flow across the surface.

FIG. 2(
a,b,c) provide schematic illustrations of an example embodiment of the present invention. The substrate and regions illustrated can be like those described in connection with FIG. 1. A depiction of the controllable characteristic, for example surface temperature of the regions, is depicted graphically above the substrate and regions. In FIG. 2a, regions 1-3 and 7-9 (counting from the left of the figure) are controlled such that their temperature is at a first value. Regions 4-6 and 10-12 are controlled such that their temperature is at a second value, lower than the first value. The temperature differential will encourage fluid to flow along the surface.

In FIG. 2b, regions 2-4 and 8-10 are at the first, high temperature, while regions 1, 5-7, and 11-12 are at the second, low temperature. The timing of the change from the profile in FIG. 2a to that in FIG. 2b can be chosen such that fluid flow velocity based on the temperature differentials are continued by the timing of the control changes (i.e., the fluid is “chasing” the temperature differential across the surface). The induced velocity of the fluid is comparable to but somewhat less than the “phase velocity” of the surface thermal wave, which is the velocity at which the high temperature regions move across the surface. To generate large flow velocities, the temperatures of the various regions have to change rapidly. In FIG. 2c, regions 3-5 and 9-11 are at the first, high temperature, while regions 1-2, 6-8, and 12 are at the second, low temperature.

FIG. 3(
a,b,c) provide schematic illustrations of an example embodiment of the present invention. The substrate and regions illustrated can be like those described in connection with FIG. 1. A depiction of the controllable characteristic, for example surface temperature of the regions, is depicted graphically above the substrate and regions.

In FIG. 3a, regions 3, 7 and 11 (counting from the left of the figure) are controlled such that their temperature is at a first value. Regions 2, 4, 6, 8, 10 and 12 are controlled such that their temperature is at a second value, lower than the first value. Regions 1, 5, and 9 are controlled such that their temperature is at a third value, lower than the second value. The temperature differential will encourage fluid to flow along the surface. In FIG. 3b, regions 4, 8 and 12 are at the first highest value, regions 1, 3, 5, 7, 9 and 11 are at the second intermediate value, and regions 2, 6, and 10 are at the third lowest value. The timing of the change from the profile in FIG. 2a to that in FIG. 2b can be chosen such that fluid flow velocity based on the temperature differentials are continued by the timing of the control changes (i.e., the fluid is “chasing” the temperature differential across the surface). The induced velocity of the fluid is comparable to but somewhat less than the “phase velocity” of the surface thermal wave, which is the velocity at which the high temperature regions move across the surface. To generate large flow velocities, the temperatures of the various regions have to change rapidly. In FIG. 3c, regions 1, 5 and 9 are at the first highest value, regions 2, 4, 6, 8, 10 and 12 are at the second intermediate value, and regions 3, 7, and 11 are at the third lowest value.

FIG. 4 is a schematic illustration of an example embodiment of the present invention. A plurality of elements 401 is disposed in an array such that fluid flow paths 402 are formed between the elements. Each element has regions 403 on the surfaces facing a fluid flow path that accommodates wave propagation like that described above. The facing surfaces can encourage fluid flow in the flow paths between the surfaces.

FIG. 5
a is a schematic illustration of an example embodiment of the present invention. A device or system 501 to be cooled or heated mounts with a fluid flow device 502. The device 502 is configured to form a plurality of fluid flow paths, similar to the flow paths shown in FIG. 4. In operation, heat is transferred between device 501 and device 502, and between device 502 and the fluid flowing through the paths 505. Fluid is pumped through the paths 505 by wave propagation like that described above, such that the fluid transport can be accomplished without moving parts and attendant noise, cost, size, and reliability disadvantages.

FIG. 5
b is a schematic illustration of an example embodiment of the present invention. A device or system 501 to be cooled or heated mounts with a fluid flow device 512. The device 512 is configured to form a plurality of fluid flow paths, similar to the flow paths shown in FIG. 4. The device 512 differs from the device 502 in FIG. 5a in that the flow paths are open on the top so that they form a series of “fins” so that the fluid can enter or leave the flow paths. In operation, heat is transferred between device 501 and device 512, and between device 512 and the fluid flowing through the paths 515. Fluid is pumped through the paths 515 by wave propagation like that described above, such that the fluid transport can be accomplished without moving parts and attendant noise, cost, size, and reliability disadvantages.

FIG. 6
a is a schematic illustration of an example embodiment of the present invention. A device or system 601 to be cooled or heated mounts with a fluid flow device 602. The device 602 is configured to define an internal channel 605. The facing surfaces of the channel 605, for example the top and bottom surfaces as shown in the figure, are configured to accommodate wave propagation as described above. Fluid can thereby be pushed through the channel 605 to facilitate heat transfer between device 601 and fluid without moving parts and attendant noise, cost, size, and reliability disadvantages.

FIG. 6
b is a schematic illustration of an example embodiment of the present invention. A device or system 601 to be cooled or heated mounts with a fluid flow device 612. The device 612 is configured to define a fluid layer 615 near its surface. The facing surface of the fluid layer 615 is configured to accommodate wave propagation as described above. The device 612 differs from the device 602 by not having a surface above the flowing fluid to create a channel that confines the flowing fluid. In device 612 the fluid can thereby be pushed along the layer 615 close to the surface to facilitate heat transfer between device 601 and fluid without moving parts and attendant noise, cost, size, and reliability disadvantages.

The temperature of the surfaces of each of the bands can be controlled in several ways. One way is by attaching electrical heaters to each band. In this case, driving more current through a heater increases the surface temperature of that band. For example, in FIG. 2a the currents flowing through the heaters in regions 1-3 and 7-9 would be larger than the currents flowing through the heaters on regions 4-6 and 10-12. The temperatures of the regions with the larger currents would be correspondingly greater. Similarly, in FIG. 3a the currents flowing through the heater in region 3 would be greater than that flowing through the heater in region 2, and the currents flowing through the heater in region 2 would be greater than that flowing through the heater in region 1.

Another method for creating a surface-thermal wave is by controlling the surface thermal conductivity of a surface that is hotter or colder than the ambient fluid. For example, attaching a thin-film heat switch to the surface of each region 111-122 in FIG. 1 allows one to modulate the rate at which each band exchanges heat with the surrounding fluid. For example, in FIG. 2a if the substrate 201 were hot the thermal conductivity of the thin-film heat switches in regions 1-3 and 7-9 would be larger than the thermal conductivity of the thin-film heat switches on regions 4-6 and 10-12. The temperatures of the regions with the larger thermal conductivity heat switches would be correspondingly greater. Similarly, in FIG. 3a if the substrate 301 were hot the thermal conductivity of the thin-film heat switches in region 3 would be greater than that for region 2, which in turn would be greater than that for region 1.

Another method for creating a surface-thermal wave is by attaching thin thermoelectric devices to the surface of each region 111-122 in FIG. 1. The thermoelectric devices raise or lower the surface temperatures of each region as required to produces surface-thermal waves. For example, in FIG. 2a the thermoelectric devices would heat regions 1-3 and 7-9 to a higher temperature than regions 4-6 and 10-12.

Still another method for creating surface-thermal waves is by attaching thin electrocaloric devices to the surface of each region 111-122 in FIG. 1. The electrocaloric devices raise or lower the surface temperatures as required to produces thermal waves. For example, in FIG. 2a the electrocaloric devices would heat regions 1-3 and 7-9 to a higher temperature than regions 4-6 and 10-12.

An additional method for producing surface-thermal waves is by illuminating the surface of each region 111-122 in FIG. 1 with different amounts of electromagnetic radiation. This radiation can be infrared light, visible light or ultraviolet light. The absorption of the light on the different regions raises the temperature of the regions in proportion with the intensity of the light. For example, in FIG. 2a more intense light would heat regions 1-3 and 7-9 to a higher temperature than regions 4-6 and 10-12, which would be exposed to less or no light. The reflectivity of the regions can be changed, to control the energy absorption of each region, as a single control method or in combination with varied incident light energy levels.

The wave-driven blower as illustrated in FIGS. 5(a, b) and 6(a, b) can impart heat to the fluid as the fluid moves through the device. Some of the methods discussed above for creating surface-thermal waves will raise the average temperature of the surfaces and will impart heat to the moving fluid. For example, the electric heaters that heat the various regions of the surface, as shown in FIG. 2(a, b, c) and FIG. 3(a, b, c) will produce a net heating of the whole surface and would heat the fluid passing next to it. Similarly, thermoelectric devices attached to the different regions of the surface can provide heating to the fluid passing near the surface. If the substrates are hotter than the ambient temperature, thin-film heat switches attached to the different regions of the surface can control the amount of temperature rise for the different regions, but there will be a net transfer of heat to the fluid passing through the device. By heating air the wave-driven blowers can be used as hot air blowers, hair dryers and heat guns.

The wave-driven blower can be attached to a hot object so that the heat from the hot object heats up the wall of the device, as illustrated in FIG. 5(a, b) and FIG. 6(a, b). The fluid or air that passes through the wave-driven blower can carry heat away from the vicinity of the hot object and the wave-driven blower. In this embodiment the heat wave can be generated by some of the techniques described above, but not limited to them. Possible techniques include, but are not limited to, using thin-film heat switches, thermoelectric devices or electrocaloric devices. In this way heat removal from a hot object is enhanced. The wave-driven blower can aid in heat removal from hot objects including computers, electronics, and light emitting diodes and other illumination devices.

The wave-driven blower as illustrated in FIGS. 5(a, b) and 6(a, b) can cool the fluid as the fluid moves through the device. Some of the methods discussed above for creating surface-thermal waves can lower the average temperature of the surfaces and can extract heat from the moving fluid. For example, the thermoelectric devices that cool the various regions of the surface, as shown in FIG. 2(a, b, c) and FIG. 3(a, b, c) can produce a net cooling of the whole surface and will cool the fluid passing next to it. If the substrates are cooler than the ambient temperature, thin-film heat switches attached to the different regions of the surface can control the amount of temperature fall for the different regions, but there will be a net extraction of heat from the fluid passing through the device. By cooling air or other fluids the wave-driven blowers can be used for air conditioning and for refrigeration.

In another embodiment of a wave-driven blower, the ionic concentration in the fluid near each region is controlled to produce ionic-concentration waves. The ionic concentration near each region is controllable by many means. For example, a voltage can be applied to spikes on the surfaces of each band to create electrical discharges that ionize the atoms and molecules in the nearby fluid. Another means of controlling the ion density is to apply voltages to each of the bands. If the air is partially ionized, the ions will be attracted or repelled by each region, depending on the sign of the ionic charge and whether the band has positive or negative voltage biases.

With the controllable variable taken to be the ionic concentration, FIG. 2(a, b, c) and FIG. 3(a, b, c) provide schematic illustrations of the operation of a wave-driven blower in which the controllable characteristic is the ionic concentration near the surface. The substrate and regions illustrated can be like those described in connection with FIG. 1. A depiction of the ionic concentration of the regions is depicted graphically above the substrate and regions.

In FIG. 2a, regions 1-3 and 7-9 (counting from the left of the figure) are controlled such that their ionic concentration is at a first value. Regions 4-6 and 10-12 are controlled such that their ionic concentration is at a second value, lower than the first value. The ionic concentration differential will encourage fluid to flow along the surface. In FIG. 2b, regions 2-4 and 8-10 are at the first, high ionic concentration, while regions 1, 5-7, and 11-12 are at the second, low ionic concentration. The timing of the change from the profile in FIG. 2a to that in FIG. 2b can be chosen such that fluid flow velocity based on the ionic concentration differentials are continued by the timing of the control changes (i.e., the fluid is “chasing” the ionic concentration differential across the surface). The induced velocity of the fluid is comparable to but somewhat less than the “phase velocity” of the ionic concentration wave, which is the velocity at which the high ionic concentration regions move across the surface. To generate large flow velocities, the ionic concentrations of the various regions have to change rapidly. In FIG. 2c, regions 3-5 and 9-11 are at the first, high ionic concentration, while regions 1-2, 6-8, and 12 are at the second, low ionic concentration. The motion of the ionic concentration wave entrains the fluid in the channels creating fluid flow.

In another embodiment of a wave-driven blower, the surface texture of each region is controlled to produce surface-texture waves. The texture of the surface of each region is controllable by many means. For example, a surface layer of microelectromechanical system, MEMS, devices can be attached to the surfaces of each region. A voltage applied to the MEMS devices of each region alters the surface texture creating a surface-texture wave. Fluid flowing over these textured regions will acquire irregular flow patterns that will couple with the overall flow.

With the controllable variable taken to be the surface texture, FIG. 2(a, b, c) and FIG. 3(a, b, c) provide schematic illustrations of the operation of a wave-driven blower in which the controllable characteristic is the surface texture near the surface. The substrate and regions illustrated can be like those described in connection with FIG. 1. A depiction of the surface-texture of the regions is depicted graphically above the substrate and regions.

In FIG. 2a, regions 1-3 and 7-9 (counting from the left of the figure) are controlled such that their surface texture is at a first value. Regions 4-6 and 10-12 are controlled such that their surface-texture is at a second value, lower than the first value. The surface-texture differential will encourage fluid to flow along the surface. In FIG. 2b, regions 2-4 and 8-10 are at the first, high surface texture, while regions 1, 5-7, and 11-12 are at the second, low surface texture. The timing of the change from the profile in FIG. 2a to that in FIG. 2b can be chosen such that fluid flow velocity based on the surface-texture differentials are continued by the timing of the control changes (i.e., the fluid is “chasing” the surface-texture differential across the surface). The induced velocity of the fluid is comparable to but somewhat less than the “phase velocity” of the surface surface-texture wave, which is the velocity at which the high surface texture regions move across the surface. To generate large flow velocities, the surface-textures of the various regions have to change rapidly. In FIG. 2c, regions 3-5 and 9-11 are at the first, high surface texture, while regions 1-2, 6-8, and 12 are at the second, low surface texture. The motion of the surface-texture wave entrains the fluid in the channels creating fluid flow.

In another embodiment of a wave-driven blower, the traveling waves can be variations in gas composition near each region. The magnitudes of each of quantities can be varied by several means. For example a particular species of gas, such as nitrogen or argon, can be stored in a reservoir. The wave-driven blower can control the size of pores or holes in the surfaces of each region. Opening the pores in one band increases the concentration of the particular species of gas near the surface of that band. Closing the pores in another band decreases the concentration of the particular species of gas near the surface of that band. In this embodiment, the control variable can be the concentration of injected gas species. Fluid flow would be generated as described for the other embodiments with this new control variable.

In another embodiment of a wave-driven blower, the traveling waves can be variations in gas pressure near each region. The magnitudes of each of quantities can be varied by several means. For example high-pressure gas can be stored in a reservoir. The wind-driven blower can control the size of pores or holes in the surfaces of each region. Opening the pores in one band increases the gas pressure near the surface of that band. Closing the pores in another band decreases the gas pressure near the surface of that band. In this embodiment, the control variable is the concentration of injected gas species. Fluid flow is generated as described for the other embodiments with this new control variable.

The various waves that operate in a wave-driven blower can include any of the above-mentioned waves or other types of waves acting individually or in combinations with one or more other types of waves. For example the wave-driven blower device can work simultaneously with surface-temperature waves and ionic-concentration waves.

A wave-driven blower can operate in reverse as a device that converts the kinetic energy from fluid flow into other forms of energy. In these embodiments it is appropriate to refer to the device as a wave-driven generator though all the components are the same as shown in FIG. 1-6. The flow of air or other fluid through the channels 402 in a wave-driven generator imparts energy to the surface waves.

In one embodiment the wave-driven generator uses surface-thermal waves. The motion of fluid through channels 402 interacts with surface-thermal waves. The interactions transfer energy from the fluid flow to the surface-thermal waves. The induced surface temperature changes can generate electrical power through various processes such as the electrocaloric effect.

Example Embodiment

FIG. 7 is a schematic illustration of a single heat fin in an example embodiment of the present invention. The heat fin 701 comprises a substantially rigid material with high thermal and electrical conductivities, for example copper or aluminum.

FIG. 8 is a schematic illustration of an electrically insulating gasket. The gasket 801 can comprise any electrically insulating material that also provides a good seal for containing liquid crystals. The insulating gaskets mount between the electrodes and the heat fins. The gaskets electrically insulate the electrodes from the fins. The gaskets also create cavities between the heat fin and the electrodes for holding liquid crystal material.

FIG. 9 is an illustration of a single electrode 902 with an electrical wired 901 connected to it. The electrical wire 901 connects to the control electronics, which sets the voltage of the electrode relative to the heat fin.

FIG. 10 is an illustration of a set of electrodes 902 with their electrical leads 901. Each electrode is electrically and thermally isolated from the other electrodes.

FIG. 11 is an exploded view of the solid components of a heat fin with arrays of thin film heat switches on each side. On each side of the heat fin 701 the gaskets 801 are located between the sets of electrodes 1001 and the heat fin 701.

FIG. 12 is a sketch of a heat fin with arrays of thin film heat switches connected to each side. On each side of the heat fin 701 the gaskets 801 create seals between each electrode 902 and the heat fin 701. The cavity created by electrode 902 the gasket 801 and the heat fin 701 is filled with a liquid crystal. The liquid crystal can be one of a class of liquid crystals that exhibit strong thermal conductivity anisotropy and which change the orientations of their director under the influence of an electric field. This class includes the n-pentyl-4-cyanobiphenyl (nCB) series of liquid crystals among many others. For clarity, the electrical leads from each fin are not explicitly shown in this figure.

FIG. 13 is an illustration of a set of heat fins with thin-film heat switches on their interior walls connected to the base of the heat sink 1301. The base of the heat sink 1301 is thermally connected to the hot object that is producing heat. The interior heat fins 1401 have arrays of thin film heat switches on both surfaces. The exterior heat fins 1501 have arrays of thin-film heat switches only on the inside surface of the heat fin. The electrical leads from each of the electrodes and from the heat fins are bundled in a cable 1201 and connected to the control electronics 1101. The control electronics regulates the voltage of each electrode relative to the heat fin on which it is mounted. The control electronics can control the thermal conductivity across the layers of liquid crystal in each heat switch to generate waves as described before.

Electrohydrodynamic Thin-Film Heat Switch. Electrohydrodynamically (EHD) driven thin-film heat switches can switch the effective thermal conductivity across a ˜100 micron layer by about a factor of 100 on millisecond time scales. These heat switches can perform the functions of liquid crystal based heat switches. Thin-film heat switches enable electrocaloric heat engines. These switches can also enable magnetocaloric heat engines, which use rapidly changing magnetic fields rather than electric fields. Heat switches can enable thermal-wave fans, as discussed above. With suitable heat switches, electrocaloric and magnetocaloric heat engines can perform far better than existing thermoelectric devices and even supersede vapor compression heat engines. The EHD switches can be also used to control the temperature of existing devices that are subject to changing thermal environments or changing power generation. These can include satellites, electric batteries, detector arrays or computer chips. The EHD switches also can be used in protective clothing.

Electrohydrodynamic heat switches use EHD flows, which are based on the dynamics of dielectric liquids that carry charge. In earlier EHD experiments, a high voltage is applied to a pointed object with radii of curvature of a few microns. The large local electric field forces charge to leak into the dielectric liquid. Since the liquid is not electrically conducting, there is no discharge current or breakdown. The imposed electric field drags the charged liquid creating fluid circulation. In the published experiments, kV voltages create circulations over macroscopic scales (a few cm), which significantly enhance the heat transfer (Grassi, et al. 2006).

The present invention uses EHD phenomenon on the small scales (much less than one cm). EHD heat flows create convective flows in layers of thickness less than one millimeter and use arrays of micro-discharge spikes with radii of curvature less than one micron. These devices create convective flows that enhance the heat flow by large factors and do not require large voltages. These enhanced heat flows can be turned on or off in a small fraction of a second.

The arrays of micro-discharge spikes can be formed by lithographic techniques. There are a number of strategies suitable to obtain spikes with the needed sharpness and aspect ratio. As an example, one can use an aluminum mask and adjust the etching plasma so that the posts neck off. Alternatively, one may initially form straight sided posts with a dry etch and then use a plane-selective wet etch. Plane-selective etchants can put an extremely sharp tip to the posts.

Tall non-conducting oxide posts or gaskets can act as spacers to separate the electrodes EHD heat switches. The cells of the EHD switches can be filled with dielectric fluids. Examples of such fluids are HFE-7100, a non-toxic hydrofluoroether produced by 3M. Increasing voltage across the electrodes drives EHD convection.

Electric Motors And Generators. An example embodiment of a PARS generator or motor is schematically described in the block diagram of FIG. 14. At the center of this diagram is a driver unit 2045 comprising materials of high magnetic permeability 2050 and magnetized by a permanent magnet 2060. In this application, materials of high magnetic permeability are referred to as “iron”. The term “iron” as used here and elsewhere includes but is not limited to transformer steel, ferrites, and silicon steel. The flux from the magnet flows through both the left branch (the reluctance-switch branch) and the right branch (the rotor branch). The fraction of the total flux going through one branch increases as the reluctance of the other branch increases. This effect is most pronounced when the reluctances of the two branches and the permanent magnet are all comparable.

A piezoelectric actuator 2030 moves back and forth and drives the reluctance switch 2040, increasing and decreasing the magnetic reluctance in the switch. In a PARS motor the piezoelectric actuator does net work on the system in one full cycle of back and forth motion. In this case net power supplied by the wires 2010 is delivered to the actuator by the power electronics 2020. In a PARS generator the rest of the system does net work on the piezoelectric actuator, and the power electronics extracts electrical power, which can be used elsewhere.

In a PARS device acting as a motor (a PARS motor) the magnetic flux passing through the reluctance switch 2040 is greater when the switch is opening than when it is closing. In this case the piezoelectric actuator does more work to open the switch than the work done on it while it is closing so that it expends net work over a full cycle.

In a PARS device acting as a generator (a PARS generator) the magnetic flux passing through the reluctance switch 2040 is greater when the switch is closing than when it is opening. In this case the piezoelectric actuator does less work to open the switch than the work done on it while it is closing so that it receives net work over a full cycle.

The rotor 2080 spinning on the shaft 2090 moves rotor-attractor plates 2095 into and out of the rotor gap 2070, modulating the reluctance of the rotor branch. The rotor-attractor plates 2095 are composed of iron. This in turn, modulates the magnetic flux moving through the reluctance-switch branch. By appropriately choosing the phase of the rotor motion and the opening and closing of the reluctance switch, the device can act as a generator or a motor. In the former case, the work done by the rotor motion becomes a power input to the piezoelectric actuator. When the device acts as a motor, the relative phases are chosen so that the rotor absorbs energy. The power electronics 2020 control the current and voltages in the piezoelectric actuator 2030 and either generates electrical power or uses electrical power when the device acts as a generator or motor, respectively.

PARS generators and motors can be more efficient than conventional electric motors and generators and are less apt to overheat. The power electronics and the piezoelectric actuator are the elements in a PARS generator or motor where most of the power losses occur. The power dissipated in the other components shown in FIG. 14 is mostly produced by eddy currents or hysteresis, which can be controlled by careful design of the magnetic circuit, reluctance switch and the rotor-attractor plates.

Both the power electronics and piezoelectric actuators are compact and efficient. Piezoelectric transformers, with similar requirements to that needed for PARS generators and motors, have high power densities and efficiencies. Similarly, the weight of these two components is small.

The following paragraphs discuss the operation of piezoelectrically actuated, reluctance-switched (PARS) generators and describe the separate components of PARS generators and motors and the complete, integrated generator or motor system. The main components that are examined are the reluctance switch and piezoelectric actuator, the magnetic circuit and the rotor with its rotor-attractor plates.

The reluctance switch modulates the magnetic reluctance by applying electric power. For PARS generators and motors, the switch allows the PARS device to extract electrical power or generate mechanical work in the rotor. Whether the device uses or generates mechanical or electrical power depends on the relative phase of the changes in the magnetic flux and the changing reluctance.

Piezoelectrically actuated reluctance switches harness the small displacements of piezoelectric drivers to take advantage of their high efficiencies and power densities. One embodiment of a reluctance switch is a sliding teeth reluctance switch with a single moveable layer as illustrated in FIG. 15. The open reluctance switch 2103 is shown in the upper part of the figure and the closed switch 2106 is shown in the lower part. This device has three iron elements with teeth: two fixed elements 2140 and one moveable element 2150. The three elements have teeth cut in their surfaces whose dimensions are comparable to the maximum displacement of the piezoelectric driver. When the switch is in the closed state 2106 (minimum magnetic reluctance), the teeth are aligned. To open the switch (i.e., increase the reluctance), the piezoelectric actuator 2110 moves the plunger 2120 that moves the non-magnetic support 2130 that that in turn moves the moveable iron teeth 2150 so that the teeth are misaligned. The guide 2170 maintains the alignment of the moveable iron teeth. The iron 2160 guides the magnetic flux.

A sliding teeth reluctance switch controls the macroscopic reluctance of the magnetic circuit with the microscopic motion of the piezoelectric actuator. The teeth of sliding teeth reluctance switches can be mechanically cut into the high permeability iron material. Alternatively, the teeth of sliding teeth reluctance switches can be formed by etching. Etch resist can be applied by photolithography or by direct printing.

To produce larger reluctance changes than that generated by a single layer sliding teeth reluctance switch, as shown in FIG. 15, one can use another embodiment of this invention, a multilayer sliding teeth reluctance switches. FIG. 16a show the open reluctance switch 2203 and FIG. 16b shows the closed switch 2206. In these devices there are a plurality moveable iron layers interleaved with fixed layers. With this design the total reluctance change is increased in proportion with the number of moveable layers. The piezoelectric actuator 2210 and plungers 2220 and guide 2270 control the motion and alignment of the moveable iron teeth. The iron 2260 guides the magnetic flux.

Nonmagnetic materials such as aluminum, strong polymers or ceramics can be used to bind elements in place, and maintain alignment. Bearings between the moveable and fixed iron elements can maintain the appropriate gap between the layers and to lessen drag as the moveable layers move back and forth. The reluctance switch with its precisely engineered parts can be sealed to prevent grains of dust or other foreign objects from obstructing its proper operation.

Actuated reluctance switches can be used to modulate the magnetic fields in magnetic circuits. In one embodiment this branch is replaced by a closed magnetic circuit with current carrying coils. In this way the mechanical actuation of the reluctance-switch-branch produces electric power in the current-carrying coils of the other branch.

In another embodiment, the variable magnetic flux passing through magnetocaloric materials drives temperature changes. This approach can be used for cooling and air conditioning devices. Reluctance switches may use a variety of actuators including linear motors, pneumatic actuators or thermal actuators. Reluctance switches can be scaled to small size to power MEMS devices and smaller structures that contain permanent magnets. These switches can be scaled to large sizes for high power generators or powerful industrial motors.

FIG. 17 shows a “driver unit” 2345 with input or output electrical power supply 2310, a piezoelectric actuator 2330, a reluctance switch 2340, iron to complete the magnetic circuit 2350, a permanent magnet 2360, and rotor gaps 2370. The iron plates on the rotor passing through the rotor gaps modulate the reluctance of the magnetic circuit. The motion of these plates through the gap does work on the magnetic circuit that is converted into electrical power through the reluctance switch, the piezoelectric actuator and power electronics.

The magnetic field generates a force between the surface of the rotor gap and the iron plate passing through it. In a PARS generator or motor with multiple rotor gaps, the total force between the magnetic circuit assembly and the rotor is multiplied compared to a PARS device with a single gap. This increase in force occurs even though the flux through the circuit is not increased over that with a single gap. This force multiplication increases the applied torque of the PARS generator or motor for a modest increase in the mass. The mass of the magnetic circuit can be made small by incorporating materials with high magnetic field saturation. With these high-saturation materials the PARS devices can be designed so that the various elements have small cross sections.

FIG. 18 shows a rotor consisting of a disk of nonmagnetic material 2410 connected to a shaft 2420. Symmetric tapered iron rotor-attractor plates 2430 are anchored near the edge of the rotor disk 2410. In a PARS generator, as the rotor spins on its shaft 2420, the interaction of the rotor-attractor plates with the variable magnetic field in the rotor gaps produces the energy that ultimately becomes electrical power. In a PARS motor, the variable magnetic field in the rotor gaps produces a force on the rotor that powers the motor. The shape of rotor-attractor plates and the numbers of plates per rotor disk determine the magnitude of the torque on the disk, which fluctuates as the disk rotates. In PARS generators and motors the rotors and rotor-attractor plates can be tailored for particular applications. For example the rotor attractor plates can be tapered to make the torque nearly constant as the rotor spins. Alternatively, the rotor attractor plates can be shaped so that the torque varies sharply as the rotor moves. Rapidly varying torques are desirable in some applications such as stepper motors. Increasing the number of plates and decreasing the size of each provides greater torque. Appropriately tapering or feathering the edge of the iron rotor plates 2430 can decrease or increase ripples in the torque as the rotor spins.

For PARS devices that act as both motors and generators, the tapering of the rotor iron plates can be symmetric to provide both accelerations and deceleration of the rotor in either direction of motion as in the rotor plates 2430 shown in FIG. 18. Additionally, for motors that are designed to move similarly in forward and reverse directions the tapering of the rotor iron plates should be symmetric.

FIG. 19 shows a rotor disk 2510, shaft 2520 and rotor iron plates 2530 for motors or generators that operate in only one direction of motion. In these motors or generators the rotor-attractor plates 2530 need tapering on only one side. This shape allows each rotor-attractor plate to produce a torque through a greater fraction of the rotational cycle and thereby allows greater compactness and higher power density of the PARS device. In FIG. 19 the rotor-attractor plates 2530 are “feathered”; that is the tapering produces more than one tip. The choice of rotor attractor shape is flexible to achieve the best results for torque smoothness and stability.

FIG. 20 shows a PARS device with multiple rotor plates 2670 on a shaft 2680 together with one driver unit 2645. The driver unit is connect to the power electronics by electric power cables 2610 and has a piezoelectric actuator 2620, and a reluctance switch 2630 which is sealed to prevent grit from damaging its interior parts. Non-magnetic material 2650 supports and maintains the alignment of the rotor gaps. Iron material 2640 completes the magnetic circuit of the driver unit 2645.

FIG. 21 illustrates one embodiment of a PARS generator or motor. The device has multiple rotor disks 2770 on shaft 2780 and multiple driver units 2720 which are connect to the power electronics by cables 2710.

The present invention has been described in the context of various example embodiments as set forth herein. It will be understood that the above description is merely illustrative of the applications of the principles of the present invention, the scope of which is to be determined by the claims viewed in light of the specification. Other variants and modifications of the invention will be apparent to those of skill in the art.

WAVE-DRIVEN BLOWER AND ELECTRIC MOTOR/GENERATOR

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