Patent Application
20240042467
Embodiments of the present application generally relate to electrostatic atomization of fluids. More specifically, embodiments of the present application relate to systems and methods for electrostatic atomization of moderately conductive fluids.
Considerable effort has been devoted to development of methods and apparatus for dispersing fluids. For example, mechanical atomizers, which operate by forcing a fluid to be atomized under high pressure through a fine orifice. Such mechanical atomizers are used in oil burners and as fuel injectors in combustion engines. Other mechanical dispersion devices mix the fluid to be atomized with a gas flowing at high velocity, so that the fluid is dispersed by the kinetic effect of the high velocity gas.
Another dispersion process is atomization of a fluid into droplets. Atomization is employed in industrial processes such as combustion, chemical treatment of fluids, spray coating and spray painting. It is ordinarily desirable in dispersion processes such as atomization to produce a fine, uniform dispersion of the fluid. Thus, in atomization it is desirable to convert the fluid into fine droplets, most desirably droplets of substantially uniform size. In one type of atomization, an electric charge, generally negative, is applied to the fluid by one or more charged electrode pairs.
Currently, such charge injected, electrostatic atomizer systems are only effective for fluids having relatively low electrical conductivity, typically below 1 microSiemens per meter (1 S/m). When the electrical conductivity of the fluid is greater than 1 S/m, it is difficult to maintain a substantial potential difference between the opposed electrodes. Although numerous organic liquids can be successfully atomized by current charge injected atomizers, many other industrially significant materials are too conductive and hence cannot be atomized or dispersed by the current atomizers. For example, typical aqueous solutions of inorganic materials are highly conductive and hence not readily susceptible to electrostatic atomization. These conductive solutions include industrially important materials, such as water-based paints and coatings, comestible materials such as beverage extracts, and agricultural materials such as aqueous fertilizer solutions, herbicide solutions and the like.
Thus, there is a need to extend the operating envelope of current charge injection atomizers to include fluids, such as water, having conductivity levels greater than 1 S/m. Additional and/or alternative advantages may be present in one or more embodiments described herein.
In at least one aspect, an apparatus for electrostatically atomizing a fluid into a plurality of charged droplets includes a chamber forming an inlet and an exit aperture, wherein the chamber is configured for the fluid to flow into the chamber from the inlet and to flow out of the chamber from the aperture. The apparatus includes an emitter electrode in liquid contact with the fluid in the chamber, wherein the emitter electrode injects an electrical charge into the fluid in the chamber. The apparatus also includes an impedance circuit coupled to the chamber and configured to obtain a voltage difference (Va− Vb) between an emitter voltage Va of the emitter electrode and an aperture voltage Vb of the exit aperture, wherein the voltage difference is at least a minimum voltage threshold.
In at least another aspect, a method by an electrostatic atomizer for electrostatically atomizing a fluid includes monitoring one or more of: an emitter voltage Va of an emitter electrode in liquid contact with the fluid in a chamber of the electrostatic atomizer; or an aperture voltage Vb of the chamber; or an emitter to aperture voltage (Va− Vb). The method also includes determining one or more of: the emitter to aperture voltage (Va− Vb); the emitter voltage Va; or the aperture voltage Vb are not within respective predetermined thresholds; and adjusting the emitter voltage Va and/or the aperture voltage Vb.
In one or more of the above aspects, the fluid has a conductivity greater than 1 microSieman/meter (μS/m).
In one or more of the above aspects, the minimum voltage threshold is determined in response to a predetermined droplet diameter of the plurality of charged droplets.
In one or more of the above aspects, the minimum voltage threshold is approximately 400 V for a predetermined droplet diameter of 10 μm.
In one or more of the above aspects, the minimum voltage threshold is approximately 3300 V for a predetermined droplet diameter of 100 μm.
In one or more of the above aspects, the impedance circuit comprises a variable impedance circuit.
In one or more of the above aspects, a controller is configured to adjust an impedance of the impedance circuit to increase or decrease the aperture voltage Vb to maintain the voltage difference (Va− Vb) at least at the minimum voltage threshold.
In one or more of the above aspects, a power supply is configured to supply the emitter voltage Va to the emitter electrode and a controller is configured to adjust the power supply to increase or decrease the emitter voltage Va to maintain the voltage difference (Va− Vb) at least at the minimum voltage threshold.
In one or more of the above aspects, a controller is configured to monitor one or more of: the emitter voltage Va; or the aperture voltage Vb; or the voltage difference (Va− Vb) between the emitter voltage Va and the aperture voltage Vb.
In one or more of the above aspects, a controller is configured to adjust the emitter voltage Va; or the aperture voltage Vb; or a combination of the emitter voltage Va and the aperture voltage Vb.
In one or more of the above aspects, the step of determining that one or more of: the emitter to aperture voltage (Va− Vb); the emitter voltage Va; or the aperture voltage Vb; are not within the respective predetermined thresholds includes determining the emitter to aperture voltage (Va− Vb) falls below a minimum voltage threshold VT.
In one or more of the above aspects, the step of adjusting the emitter voltage Va and/or the aperture voltage Vb includes one or more of: adjusting a power supply to the emitter electrode to increase or decrease the emitter voltage Va; or adjusting a variable impedance circuit to increase or decrease the aperture voltage Vb.
In one or more of the above aspects, the method includes injecting the fluid into the chamber, wherein the chamber forms an aperture and injecting an electrical charge through the fluid, using an emitter electrode, as the fluid flows through chamber, past the emitter electrode and exits the aperture.
In one or more of the above aspects, the method includes electrostatically atomizing the fluid into a charged spray, wherein the charged spray includes a plurality of charged droplets; and directing the charged spray at a surface for a predetermined duration to decontaminate the surface. The fluid may include water, and the predetermined duration is 60 seconds or less.
In one or more of the above aspects, the droplets in a charged spray of a plurality of charged droplets of the atomized fluid are characterized by a K factor, wherein the K factor is a ratio of the electrostatic energy of the surface charges (We) and the surface energy (Ws), and wherein the K factor is less than one (K<1).
In one or more of the above aspects, the method includes electrostatically atomizing saline water into a charged spray, wherein the charged spray includes a plurality of charged droplets; directing the charged spray at an evaporative surface to separate water from salt particulates; and collecting the separated water. The method may further include applying heat and/or pressure to the evaporative surface to evaporate the separated water.
In one or more of the above aspects, the method includes electrostatically atomizing saline water into a charged spray, wherein the charged spray includes a plurality of charged droplets; directing the charged spray at a surface of a material, wherein the material traps and/or attracts salt particulates in the plurality of charged droplets; and collecting water residue not trapped by the material.
The foregoing summary, as well as the following detailed description of preferred embodiments of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments that are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings:
As required, a detailed illustrative embodiment of the present invention is disclosed herein. However, techniques, systems, and operating structures in accordance with the present invention may be embodied in a wide variety of forms and modes, some of which may be quite different from those in the disclosed embodiment. Consequently, the specific structural and functional details disclosed herein are merely representative, yet in that regard, they are deemed to afford the best embodiment for purposes of disclosure and to provide a basis for the claims herein, which define the scope of the present invention. The following presents a detailed description of the preferred embodiment (as well as some alternative embodiments) of the present invention.
In the following description, numerous specific details are set forth to provide a more thorough understanding of the present invention. However, it will be apparent to one of skill in the art that the present invention may be practiced without one or more of these specific details. In other instances, well-known features have not been described to avoid obscuring the present invention. For clarity, embodiments of the present invention are described in terms of conductive fluent material. However, it is contemplated that virtually any fluent material including materials such as non-conductive fluids, and the like, may be used to advantage within the scope of the present invention. In addition, both fluent and non-fluent materials may be produced using the methods and apparatus of the present invention.
A first non-conductive elongated cylindrically shaped tube 242 having an externally threaded surface 218 and a continuous bore therethrough is threadedly disposed through threaded aperture 220, wherein one end 246 of tube 242 extends outwardly from housing 212 and the other end 248 of tube 242 extends inwardly into an upper portion of chamber 226. A first electrode 238 or a series of first electrodes 238 in parallel or in a parallel series combination is joined into the end 248 of tube 242 by suitable means such as an adhesive cement or the end 248 of tube 242 can be embedded into electrode 238, wherein electrode 238 preferably is a setaceous surface 250 formed from a plurality of pins 251 which are in a substantially parallel alignment within the chamber 226. A setaceous surface is defined as one having a plurality of essentially parallel similar continuous pins having lateral dimensions of order 10 μm, more preferably 1 μm, most preferably 0.1 mm or less in a matrix of non-conductor or semi-conductor material. Each pin is arrayed in a regular or almost regular pattern with mean separation distances of an order of about 35 μm or less. An example of a suitable electrode 238, but not limiting in scope, is a eutectic mixture of uranium oxide and tungsten fibers, e.g., as described in the article, “Unidirectional Solidification Behavior in Refractory Oxide Metal Systems,” A. T. Chapman, R. J. Geides, Journal of Crystal Growth Vol. 13/14, p. 765, 771 (1972).
The first electrode 238 is connected in series to a high voltage source 240 which is disposed externally to the housing 212, by means of a first electrical lead wire 252 extending through the bore 244 of tube 242. The high voltage source 240 is wired by means of a ground wire 276 to a ground 278 disposed externally to device 210. A second non-conductive, elongated cylindrically shaped tube 256 (e.g., made of a plastic, such as a Lucite® material) having a continuous bore 258 therethrough is disposed through aperture 221, wherein one end 260 of tube 256 extends outwardly from housing 212 and the other end 262 of tube 256 extends inwardly into a lower portion of chamber 226. A liquid tight seal is formed between tube 256 and sidewall 216 by adhesive or by another sealant means 254.
A second electrode 264 or a series of second electrodes 264 in parallel or in series parallel combination are joined onto end 264 of tube 256 by suitable means such as an adhesive cement or the end 262 of tube 256 can be embedded in electrode 264. The second electrode 264 is a planar shaped disc 266 having at least one center longitudinally aligned aperture 268 therethrough and optionally a plurality more of longitudinally aligned apertures 270 therethrough at prescribed distances from the center aperture 268; alternately a plurality of longitudinally aligned apertures 268 could be used arrayed symmetrically with respect to the center line with no aperture hole on the center line.
The aperture holes could also be skewed to the center line. The second electrode 264 is disposed transversely within chamber 226 below and spaced apart from the first electrode 238. The first electrode 238 can be moved longitudinally upwardly or downwardly thereby reducing or increasing the gap between the electrodes 238, 264 as well as modifying the flow of charge within the liquid. The second electrode 264 is preferably formed, e.g., from platinum, nickel or stainless steel and is wired in series to a high voltage resistor element 272 disposed externally to housing 212 by an electrical lead wire 274 extending through tube 256. The resistor element 272 is connected at its opposite end to ground juncture 280 of the high voltage source 240.
An external annularly shaped electrode 282 (e.g., stainless steel) can be affixed on the external bottom surface 284 of base 214 by adhesive means or by a plurality of anchoring elements 286 extending upwardly through electrode 282 and being embedded into base 214. The center opening 288 of electrode 282 and discharge opening 228 are aligned, wherein opening 228 is preferably less than about 2 cm in diameter, more preferably less than about 1 cm in diameter most preferably less than about 6 mm in diameter, and the diameter of the center opening 88 is less than about 1 mm, more preferably less than about 600 μm, and most preferably less than about 200 μm. In this position, electrode 282 assists the spraying due to the development of the electrostatic field; however, the positioning of electrode 282 at this position is not critical to operation as long as this electrode 282 is disposed external to housing 212.
The electrode 282 is also connected to a second grounded junction 290 disposed between ground 278 and the first electrical juncture 280. The first electrode 238 is negatively charged wherein the second electrode 264 has a relative positive potential with respect to the first electrode 238 and the external electrode 282 is at ground potential (the positive potential of source 240). In one mode of operation the first electrode 238 is negatively charged and the second electrode264 and the external electrode282 are relatively positively charged.
The high voltage source 240 which can be a direct voltage, an alternating voltage, or a pulsed voltage source of either polarity, wherein the source is about 100 volts to about 100 kilovolts, more preferably about 100 volts to about 50 kilovolts DC, and most preferably about 100 volts to about 30 kilovolts DC. The charge induced into the liquid 236 within the chamber 226 results in a flow from the first electrode 238 to the second electrode 264. The liquid within the chamber 226 flows towards the discharge opening 228 of the base 214, wherein the electrical charge which is induced into the liquid within the chamber 226 must be sufficient to generate excess free charge in the liquid within the chamber 226, wherein the charge can be positive or negative. The fluid is emitted outwardly therefrom in a spray configuration, (as a plurality of droplets, wherein the external electrode 282 enhances acceleration of the charged droplets. In an embodiment, the fluid has a conductivity of less than about 10−4 mho/meter, more preferably less than about 10−4 mho/meter, and most preferably less than about 10−10 mho/meter. Another example of an electrostatic dispenser is described in U.S. Pat. No. 8,622,324, entitled, “VOC-less Electrostatic Dispenser,” issued on Jan. 7, 2012 with inventor Arnold J. Kelly.
Electrostatic atomization enables the electronic control of fuel droplet size and dispersion. The mean droplet size will be determined solely by the free charge density ρ=Q/V, Coulombs per volume (C/m3) of a droplet of the fluid. Droplet diameter is independent of other properties, e.g., such as the fluid properties of conductivity, density, viscosity, temperature, background conditions (such as pressure, temperature, humidity), and fluid dynamic effects (such as fluid velocity and flow rate). In general, electrostatic sprays, independent of source, will self-organize such that each droplet surface charge is exceptionally energetic (˜55 electron-volt (eV))−an energy level approximately twenty times larger than that associated with chemical or fluid dynamic processes (2 to 3 eV).
The inference that electrostatic spraying is a meso-scale quantum-mechanical process is bolstered by the fact that the energy level of 55 eV is within about 1% of 4 Rydberg unit of energy (Ry), wherein 4 Ry=54.6 eV. Additionally, and more convincingly, using available data, such as in the article by A. J. Kelly, entitled, “Low Charge Density Electrostatic Atomization,” IEEE Industry Applications, 1-A, 20, pp. 267-273, 1984, spanning greater than three orders of magnitude in charging level (ultimately expanded to ˜7 orders of magnitude for disparate liquids), droplet diameter (d) is, with <5% uncertainty, simply related to the number of surface charges (Ne), wherein:
d=N
e
a
0, whereina0 is the first Bohr radius5.29 10−11m.
These close correspondences are unlikely to be coincidental. Subsequent work has validated the quantum-mechanical nature of electrostatic sprays.
These discoveries led to the development of the electrostatic atomizers or direct charge injection atomizers, hereinafter referred to as direct charge injection (DCI) atomizers. Numerically, droplet diameter (d) is simply related to the charge density ρ (C/m3) by the following relation:
d(μm)=75/√p.
Production of unlimited quantities of charged droplets having precisely determined diameters can thus be achieved by simply submerging an electron source in the fluid to be atomized.
Another embodiment of a charge injection, electrostatic atomizer 100, such as that described in
Oils, fuels, and electrically insulating fluids are particularly well suited for use with the anatomization process of a charge injection, electrostatic atomizer, e.g., such as the Spray Triode Atomizer®. Electrically insulating fluids are characterized by low charge mobility velocity v=μE, wherein μ is the charge mobility (typically μ has an order 10−7) and E is the emitter/aperture electric field strength required for charge injection (typically E is approximately 107 V/m). Charge velocity v in these fluids is therefore on the order of 1 m/sec. In known embodiments, the aperture flow velocity of the injected fluids (e.g., approximately 10 m/s) is generally higher than the charge velocity. As such, most of the injected charge is expelled in the fluid flowing from the electrostatic atomizer. In some instances, greater than 95% of the input charge has been observed as spray current.
This type of charge injection, electrostatic atomizer is extremely efficient in converting bulk fluid into droplet sprays. For instance, only 6 milliwatt (mW) of input injected electrical power is required to generate a 30 μm diameter droplet spray at 1 milliliter per second (mL/s) throughput. By comparison, the hydraulic power required to simply move the fluid through the exit aperture is usually an order of magnitude greater. Thus, in comparison, very little extra power is needed for the emitter electrode of the atomizer.
Currently, these charge injection, electrostatic atomizers described in
In contrast, the current charge injection, electrostatic atomizers, e.g., as shown in
However, due to the efficiency and simplicity of charge injection, electrostatic type atomizers, it would be advantageous to extend the operating envelope of such atomizers to include fluids such as saline water having conductivity levels greater than 1 μS/m. Conceptually, if the aperture flow velocity is sufficiently high, these electrostatic type atomizers are capable of charge injecting any fluid; the charge mobility velocity must be comparable to, or lower than, the aperture flow velocity of the fluid. This may be marginally feasible for de-ionized (DI), distilled water and some low conductivity tap waters. However, more conductive fluids (greater than approximately μS/m or greater than approximately 1 mS/in) would require exorbitantly high pumping power which leads to correspondingly low operating efficiency, and so are not economically feasible. Thus, an electrostatic atomizer capable of atomizing fluids having conductivity levels greater than 1 μS/m without unacceptably high flow velocities and exorbitant pumping power has been a long felt but unmet need in the industry.
It was found in unexpected results that when the second electrode formed by the chamber 404 and/or aperture 406 is maintained at an elevated voltage, e.g. rather than at or near ground as with current charge injection, electrostatic atomizers, it is possible to meet the required thresholds for the emitter to aperture voltage, and effectively atomize moderately conductive fluids cost effectively without unacceptably high flow velocities.
In one embodiment, an impedance circuit 410 is implemented in series with the chamber/electrode 404 to generate a voltage Vb at chamber 404 (and so also at the exit aperture 406), wherein the voltage Vb equals the current Ib times the impedance Rb. The emitter electrode 402 is charged to a first voltage Va while the second voltage Vb at the chamber 404/aperture 406 is at an elevated voltage, such that the emitter to aperture voltage Va−Vb equals at least a minimum voltage threshold. Successful spray generation to atomize moderately conductive fluids requires that the emitter to aperture voltage Va−Vb exceeds a minimum voltage, wherein the minimum voltage may be set to obtain a preferred droplet diameter. For example, the minimum voltage tray be set to approximately 400 V to produce droplets with 10 μm diameters or may be set to approximately 3300 V for droplets with 100 μm diameters. In one embodiment, the operating voltage Vb of the chamber 404 and/or aperture 406 is in a range of 1 to 100 KiloVolts (KV). In another embodiment, the operating voltage Vb of the chamber 404 and/or aperture 406 is 100 to 500 Volts below the input voltage Va.
In one embodiment, the impedance circuit 410 includes at least one resistor Rb, wherein Rb is approximately 400 MegaOhms (MΩ). Alternative or additional impedance circuits may be implemented to obtain a minimum aperture voltage Vb needed for the desired droplet diameter for the fluid. For example, pulsed or dynamically variable operation and/or use of an AC current can involve an inductive and/or capacitive and/or variable impedance circuit 410 to generate the appropriate voltage differential. Assuming that the current carried away from the atomizer 400 by the fluid flow is termed the spray current, Is, and the current that passes through the liquid to the chamber 404/aperture 406 is the leakage current, IL, then the second voltage Vb at the chamber 404/aperture 406 may be determined as follows:
V
b
=I
L
*R
b
So rather than the chamber/aperture voltage Vb being at or near ground as in known charge injection, electrostatic atomizers, the modified electrostatic atomizer 400 exhibits a chamber/aperture voltage Vb equal to the leakage current IL times the impedance Rb. In one embodiment, the operating voltage Vb of the chamber 404 and/or aperture 406 is in a range of 1 to 100 KiloVolts (KV). In another embodiment, the operating voltage Vb of the chamber 404 and/or aperture 406 is 100 to 500 Volts below the input voltage Ma.
The fluid 504 is introduced into the modified electrostatic atomizer 400 using a valve 508, such as an inline slide valve or other type of valve, and an inlet 518. The power supply 514 energizes the emitter electrode 402 in the fluid chamber 404 of the modified electrostatic atomizer 400. When energized, the emitter electrode 402 electrostatically charges the pressurized fluid 504 in the chamber 404 as it flows through the fluid chamber 404 and exits through the aperture 406. That is, the fluid 504, under pressure, exits reservoir 502 and enters the chamber 404 of the modified electrostatic atomizer 400 through valve 508 and fluid inlet 518. The fluid 504 flows past the emitter electrode 402 and then flows out of the chamber 404 through aperture 406. As the fluid 504 passes through the chamber 404, it becomes electrically charged and subsequently atomizes and self-disperses into a plume or spray 522 of charged droplets after exiting the modified electrostatic atomizer 400. An external electrode pair 512 may accelerate the electrically charged and atomized droplets exiting from the aperture 406.
In this embodiment, a voltage controller 524 monitors the emitter voltage Va and the aperture voltage Vb. When the emitter to aperture difference Va−Vb falls below a minimum voltage threshold VT or above a maximum voltage threshold VM, the voltage controller 524 adjusts the emitter voltage Va or the aperture voltage Vb or a combination thereof. For example, the voltage controller 524 may adjust the variable impedance circuit 526 to increase or decrease the impedance Rb and thus, increase or decrease the aperture voltage Vb. Additionally and/or alternatively, the voltage controller 524 may increase or decrease the emitter voltage Va (e.g., increase or decrease the input current Ia from the power supply).
Using this system 500, the modified electrostatic atomizer 400 may atomize moderately to highly conductive fluids with conductivity greater than 1 μS/m without undue aperture flow velocities. However, operation of the modified electrostatic atomizer 400 is not constrained thereto. The modified electrostatic atomizer 400 may also atomize fluids with low conductivity, such as fluids having conductivity of 1 μS/m or less than 1 μS/m.
At step 608, the emitter to aperture voltage (Va−Vb) range is determined such that the modified electrostatic atomizer 400 generates the selected droplet diameter for the indicated type of fluid. To achieve the emitter to aperture voltage (Va−Vb), both the voltage of the emitter Va and the voltage of the aperture Vb are determined at 610. For example, the emitter voltage Vat may be set to operate within a first predetermined voltage range while the aperture voltage Vb may be set to operate in a second predetermined voltage range, such that the emitter to aperture voltage Va−Vb is maintained at a minimum voltage threshold or within a predetermined voltage range.
In one embodiment, the minimum emitter to aperture voltage (Va−Vb) threshold may be set to approximately 400 V for generation of 10 μm diameter droplets of water to approximately 3300 V for generation of 100 μm diameter droplets of water. The article, “Low Charge Density Electrostatic Atomization,” by A. J. Kelly, IEEE Transactions on Industry Applications, Vol 1A-20, No. 2, March/April 1984, Equation 21 reveals the existence of a characteristic voltage related to droplet size, but not how it is related to atomizer characteristics and configurations. Recently concluded experiments, in unexpected results, found that for de-ionized water, distilled water, and tap water, the emitter to aperture voltage (Va−Vb) of 400 V and 3300 V resulted in these approximate diameters of 10 μm and 100 μm, respectively. Note that these crucial voltage differentials is trivially satisfied during atomizer operation with low conductivity fluids, such as fuels and oils, but as discussed, must be carefully provided for with more conductive fluids, such as water.
The parameters of operation of the atomizer system 500 are then configured at 612. The configuration may be done automatically by the atomizer system 500 based on the user input. In another embodiment, the parameters of operation of the atomizer system 500 may be configured manually, e.g., without user input of the type of fluid, conductivity, and/or droplet diameter.
The monitoring of the voltages continues at 704 during operation of the modified electrostatic atomizer 400, and the emitter voltage Va or the aperture voltage Vb may be adjusted further to maintain the predetermined emitter to aperture voltage (Va−Vb) threshold or range. The monitoring may be continuous or at periodic intervals.
The atomizer system 500 thus adjusts a voltage of the emitter Va and/or the aperture Vb to maintain the emitter to aperture voltage (Va−Vb) at or above a minimum threshold VT or within a predetermined voltage range. By maintaining the emitter to aperture voltage (Va−Vb), successful and efficient spray generation is possible of moderately to highly conductive fluids with a conductivity of 1 μS/m or more.
The controller 800 includes a processing circuit 802 and memory device 804. The processing circuit 802 includes at least one processor, such as a central processor unit (CPU), microprocessor, microcontroller, embedded processor, digital signal processor, media processor, field programmable gate array, programmable logic device, state machine, logic circuitry, analog circuitry, digital circuitry, and/or any device that manipulates signals (analog and/or digital) based on hard coding of the circuitry and/or operational instructions.
The memory device 804 is a non-transitory memory and may be an internal memory or an external memory, and may be a single memory or a plurality of memories. The memory device 804 may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, cache memory, and/or any non-transitory memory device that stores digital information. The memory device 804 stores computer-executable instructions which when executed by the processing circuit 802 causes the atomizer system 500 to perform one or more functions described herein. Computer-executable instructions may include, e.g., program modules such as routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Such programs may be implemented in a high-level procedural or object-oriented programming language to communicate with a computer system. However, the program(s) can be implemented in assembly or machine language, if desired. In any case, the language may be a compiled or interpreted language, and combined with hardware implementations.
The controller 800 may further include a display or touch screen that displays the system parameters, settings, operational status, etc. Additional user interfaces 808 may include buttons, dials, keyboard, mouse, touchpad, or other user input devices. A transmitter 810 may include a wireless and/or wireline transmitter to control and is configured to communicate with the atomizer system 500.
Independent of the process for generation of charged sprays, be it with a charge injected atomizer, electron beam DCI injection atomizer, or by simple diode/capillary sprayers, certain fundamental principles apply to the charged sprays. Plume behavior is either dominated by surface tension (the Rayleigh regime) or by the droplet surface electric field (the emission limited regime). Sprays generated in the immediate vicinity of the boundary between the two regimes are not surprisingly more complex.
The Rayleigh regime, dominated by surface tension, is characterized by the K factor, wherein K<We/Ws, the ratio of the total electrostatic energy of the surface charges (We) and the surface tension energy (Ws). The electrostatic energy of the surface charges We of the droplet are generated by the atomization process. The surface energy Ws is the surface tension responsible for maintaining the minimum energy spherical shape of the droplet. In the Rayleigh regime, the K factor is less than 1 (K<1), and the outwardly directed, surface charge forces We are in direct competition and less than the inwardly directed surface tension Ws.
When the K factor is unity (K=1), for instance as will occur during evaporation (surface charge does not evaporate), the electrostatic We and surface tension Ws energies are equal, and the droplet disrupts. Another way of visualizing this is to consider the balance of surface forces. When the inward surface tension force is just balanced by the outward electrostatic force, the droplet is unconstrained and subject to instability. Observations of evaporating charge droplets and detailed analysis reveal that the droplet literally explodes. This so-called Rayleigh or Coulomb bursting gives birth to upwards of ten very much smaller “daughter” droplets that carry away about a quarter of the parent droplet's charge, and about five percent of its mass. What's left of the original droplet has been observed to undergo this process numerous (upwards of seven) times.
When the K factor is less than one (K<1), the droplet is sufficiently small so that surface tension forces dominate. The droplet cannot be disrupted by the electrostatic forces. Droplet charging is now completely controlled by the droplet surface electric field Es. This field limits the droplet from acquiring additional charge. The surface electric field Es uniquely defines the Rayleigh/emission spray regime boundary. That is, when the K factor equals one (K=1), the droplet surface electric field Es is the dominant, controlling factor limiting charging of smaller droplets and defining the 4 Ry energy of the surface electrons in the large droplet Rayleigh spraying regime.
As noted, in the surface tension dominated, Rayleigh regime (K<1), each surface electron is exceptionally energetic (4 Ry). Whereas, in the electrostatically dominated (K>1) regime the droplet charge energy is at best a half, and most probably a quarter of this level.
The question is: Where does the K=1 demarcation occur, and by extension what parameters define the droplet surface electric field Es? Note that the Rayleigh/emission regime boundary is defined by two distinct processes. Heretofore, the boundary has been defined solely as a particle centric process—the equality of two forces acting on a surface charge: the inwardly directed surface tension force and the outwardly directed electrostatic repulsive force. But it is equally valid to also define the boundary in terms of the equality of the overall, global system energy, the K=1 condition. In the Rayleigh regime (K<1), when surface tension dominates, the droplets are uniquely characterized by 4 Ry surface electrons, wherein Ry is the Rydberg unit and 1 Ry=13.6 eV. Melding the particle centric and the global-centric description of the K=1 transition permits derivation of a definitive expression for the droplet surface electric field Es:
E
s=(4πa0/q)γ, wherein
Numerically, the droplet surface electric field Es (GV/m)=4.12 γ (N/m), and the corresponding droplet diameter (dx) is defined as follows.
dx (μm)=0.0524/γ, wherein
For typical hydrocarbon liquids, the surface tension γ is approximately 0.03, the droplet surface electric field Es is approximately 0.13 GV/m and the droplet diameter dx is approximately 1.7 μm. For water, the surface tension γ is approximately 0.08, the droplet surface electric field Es is approximately 0.33 GV/m, and the droplet diameter dx is approximately 0.85 μm. The corresponding values for molten Woods metal: the surface tension γ is approximately 0.45, the droplet surface electric field Es is approximately 1.85 GV/m, and the droplet diameter dx is approximately 0.012 μm.
These predictions are consistent with the previously referenced available data. Most importantly, these results are strongly supportive of a very nontraditional interpretation of the electrostatic spray process.
The two electrostatic spray regimes, e.g. the surface tension dominated, Rayleigh regime (K<1) and the electrostatically dominated, emission limited regime (K>1, d>dx), can be visualized as representing two distinct aspects of the collective behavior of the droplet surface charges. A clue to the nature of these states is the prediction that droplet charging undergoes a first order charging phase transition at the K=1 boundary. See, e.g., the article by A. J. Kelly, “Low Charge Density Electrostatic Atomization,” IEEE Industry Applications, 1-A, 20, pp. 267-273, 1984.
A new theory of the charge energetics between the two regimes is proposed herein. In this theory, the droplet surface charges in the Rayleigh regime (K<1) form a crystalline structure. That is, the surface charges are dominated by collective quantum-dynamic effects to form a rigid structure, a spherical crystalline cage structure. This inference is supported by the spray data. It explains why droplet diameter is solely determined by injected charge density. If droplet size is determined by the crystalline cage structure, then the anchoring liquid is irrelevant to the droplet formation process. It also explains why the only model of Rayleigh/Coulomb bursting comporting with available data requires surface charge immobility. See, e.g., the article by D. G. Roth, A. J. Kelly, “Analysis of the Disruption of Evaporating Charged Droplets,” IEEE Industry Applications, 1-A, 19, pp. 771-775, 1983.
The K=1 boundary condition is also compatible with the theory of a crystalline cage structure. At the K=1 boundary, the crystalline cage structure melts due to zero-point energy overcoming the strength of the crystalline structure. Droplet surface charges in the emission limited regime (K>1) become a liquid or gas and are free to skitter around the surface. This theory thus postulates that the surface charges of droplets formed in the surface tension dominated Rayleigh regime (K<1) are a new state of matter, a spherical Fermionic crystal. The crystalline structure formed by the surface charges melt at the K=1 boundary and become a liquid or gas in the emission limited regime (K>1).
During experimentation, depending on the spray fluid surface tension, the droplet surface charges in the Rayleigh regime (K<1) form the crystalline structure for spray droplet sizes larger than about 0.1 micron. Specifically, the crystalline structure exists for a mean droplet size dx>0.0525/g, where g is the surface tension.
The theory of a crystalline structure of droplet surface charges (K<1) thus provides an explanation for droplet diameter being solely determined by injected charge density in the Rayleigh/Coulomb regime (K<1).
Sprays generated by the unmodified charge injection atomizers (
In recent testing, charge injected atomizers operating with (K<1) distilled water sprays, were capable of destroying E. Coli bacteria with the same lethality rate (4−log) as reported in the Pyrgiotakis article in much shorter time scales (<60 seconds). In the testing, approximately one minute exposure tests produced the same lethality rate as the 45 minute tests described in the Pyrgiotakis article. In some tests of the charge injected atomizers, E. Coli bacteria was reduced approximately 10,000-fold by brief exposure (approximately 30 seconds) to the charged water droplet sprays.
Lethality of the charge injected atomizers is attributed to generating droplets in the Rayleigh regime (K<1) having energetic 4 Ry droplet surface charges. Each droplet surface charge in the Rayleigh regime has approximately 54 eV of energy or 4 Ry. The transfer of these 4 Ry electrons to the bacterium are probably instantaneously lethal. The inherent energy of each electron is well over an order of magnitude larger than the metabolic process (2 to 3 eV) of E. Coli. The 4 Ry charge, equivalent to 54.4 eV, unleashed on the bacterium is most assuredly lethal. The approximately million charges (Ne=d/a0) delivered by each 50 μm droplet can effectively disrupt biological processes of the E. Coli bacterium.
The charge injection atomizers generating droplets in the Rayleigh regime (K<1) are thus lethal to the E. Coli bacterium, even over short exposure times of 60 seconds or less. However, since the transference of charge produces the lethality rate, the process does not offer persistence over time.
The charge injected atomizer may also provide protection against significantly more complex biologically entities, such as tick larva and less complex organisms, such as spores and viruses. In testing, a charged injection atomizer employed distilled water at an approximately 1 mL/sec flow rate with an approximately 1 μA amperage. The generated water droplets proved lethal to tick larvae. Operation with higher throughput and/or higher amperage may further reduce the exposure time required for disinfecting and sanitizing of surfaces.
Desalination has typically involved reverse osmosis technology and/or distillation to separate water molecules from seawater. In a reverse osmosis process, salt water, e.g., from the ocean, is forced through thousands of tightly wrapped, semipermeable membranes under extremely high pressure. The membranes allow the smaller water molecules to pass through, leaving salt and other impurities behind. However, the semipermeable membranes in this process require large surface areas that are exposed to pressure, heat, or a combination of the two. In distillation, selective boiling and condensation creates a separation of the water and the salt or other components). However, this distillation process consumes a large amount of energy to operate because the saltwater must be boiled at very high temperatures before it is potable. Thus, there is a need for an improved system and process for desalination.
At step 1002, the electrostatic atomizer 400 is initiated or powered using saline water, such as ocean water. The electrostatic atomizer 400 converts the saline water into plumes of charged droplets at step 1004. The charged plumes are directed onto an evaporative surface in step 1006. Due to the self-dispersity of the charged plumes, the process separates the water and salt particulates at least to some extent on the evaporative surface. The separated water may then be collected as it evaporates from the surface in step 1008. The separated water and salt particulates may undergo further processing. For example, heat or pressure may be applied to the evaporative surface to further separate the water from the salt particulates and shorten the time to evaporate the water. Additional processing such as filtering or reverse osmosis processes may also be performed.
The charged plumes enhance evaporation such that the need for heating and pressure is reduced relative to traditional desalination methods. Electrostatic sprays, by virtue of their inherently high efficiency converting bulk fluids into high surface area droplets, provides a more direct means for desalinization. Charged plumes, in addition to having high dispersion that tends to vigorously separate into individual particles, also involve Rayleigh or Coulomb Busting. As charged droplets evaporate the charge is conserved until such time as the K=1 (surface tension and counteracting electrostatic force are equal) is reached. The droplet then explodes ejecting several (upwards of ten) smaller highly charged droplets and leaving a still charged “mother” droplet. This process of intense in situ atomization is repetitive until the complete disappearance of the droplet. Due to the self-dispersion of the charged plumes, the process assists in separating the water and salt particles more efficiently. The atomization may thus shorten the desalination process and/or increase efficiency of the desalination process.
In this embodiment, a material (such as an inexpensive recyclable material) is employed that is capable of sequestering salt as micron sized particulates. These particulates are removed from the saline water by having the charged spray impact the surface of the material. The salt particulates are welded or otherwise attached to the surface of the material. The salt particulates are thus separated from the water and may be collected and removed leaving salt-free water as a residue.
Referring to
A variety of processes have been developed to remove particulate matter from bulk hydrocarbon liquids using charged sprays generated by an atomizer. A large variety of micron and sub-micron particulate materials (metals, soot, alumina, Arizona road dust, etc.) have been effectively removed from charged spray droplets. The same fundamental separation processes hold for water. For example, viruses and bacteria may be removed from contaminated water. High quality deionized water has a conductivity of about 5.5 μS/m at 25° C., typical drinking water has a conductivity in a range of 5-50 mS/m, while sea water has a conductivity of about 5 S/m (or 5,000,000 μS/m). A modified electrostatic atomizer 400 may generate a charged spray from these types of water to remove particulate matter from water.
In one or more embodiments described herein, a modified charge injection, electrostatic atomizer is described that efficiently atomizes fluids, such as water, having conductivity levels greater than 1 S/m. Rather than having a chamber/aperture that is at ground or below a small voltage (e.g., less than 10 V) as in prior charge injection atomizers, the modified atomizer has a chamber/aperture at an elevated voltage Vb. For example, the aperture voltage Vb may be equal to the leakage voltage IL times an impedance Rb of an impedance circuit (Vb=IL*Rb). The impedance circuit includes capacitance, inductance and/or resistance and may be implemented in series with the chamber/aperture of the atomizer. The emitter electrode of the atomizer is charged to a first voltage Va, such that the emitter to aperture voltage Va−Vb equals at least a minimum voltage threshold. For example, the minimum voltage may be set to approximately 400 V to produce droplets with 10 μm diameters or may be set to approximately 3300 V for droplets with 100 μm diameters.
It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.
As may be used herein, the term “operable to” or “configurable to” indicates that an element includes one or more of circuits, instructions, modules, data, input(s), output(s), etc., to perform one or more of the described or necessary corresponding functions and may further include inferred coupling to one or more other items to perform the described or necessary corresponding functions. As may also be used herein, the term(s) “coupled,” “coupled to,” “connected to” and/or “connecting” or “interconnecting” includes direct connection or link between nodes/devices and/or indirect connection between nodes/devices via an intervening item. As may further be used herein, inferred connections (i.e., where one element is connected to another element by inference) includes direct and indirect connection between two items in the same manner as “connected to.” As may be used herein, the terms “substantially” and “approximately” provides an industry-accepted tolerance for its corresponding term and/or relativity between items.
Note that the aspects of the present disclosure may be described herein as a process that is depicted as a schematic, a flow chart, a flow diagram, a structure diagram, or a block diagram. Although a flowchart may describe the operations as a sequential process, many of the operations can be performed in parallel or concurrently. In addition, the order of the operations may be re-arranged. A process is terminated when its operations are completed. A process may correspond to a method, a function, a procedure, a subroutine, a subprogram, etc. When a process corresponds to a function, its termination corresponds to a return of the function to the calling function or the main function.
The various features of the disclosure described herein can be implemented in different systems and devices without departing from the disclosure. It should be noted that the foregoing aspects of the disclosure are merely examples and are not to be construed as limiting the disclosure. The description of the aspects of the present disclosure is intended to be illustrative, and not to limit the scope of the claims. As such, the present teachings can be readily applied to other types of apparatuses and many alternatives, modifications, and variations will be apparent to those skilled in the art.
In the foregoing specification, certain representative aspects have been described with reference to specific examples. Various modifications and changes may be made, however, without departing from the scope of the present invention as set forth in the claims. The specification and figures are illustrative, rather than restrictive, and modifications are intended to be included within the scope of the present invention. Accordingly, the scope of the invention should be determined by the claims and their legal equivalents rather than by merely the examples described. For example, the components and/or elements recited in any apparatus claims may be assembled or otherwise operationally configured in a variety of permutations and are accordingly not limited to the specific configuration recited in the claims.
Furthermore, certain benefits, other advantages and solutions to problems have been described above with regard to particular embodiments; however, any benefit, advantage, solution to a problem, or any element that may cause any particular benefit, advantage, or solution to occur or to become more pronounced are not to be construed as critical, required, or essential features or components of any or all the claims.
As used herein, the terms “comprise,” “comprises,” “comprising,” “having,” “including,” “includes” or any variation thereof, are intended to reference a nonexclusive inclusion, such that a process, method, article, composition, or apparatus that comprises a list of elements does not include only those elements recited, but may also include other elements not expressly listed or inherent to such process, method, article, composition, or apparatus. Other combinations and/or modifications of the above-described structures, arrangements, applications, proportions, elements, materials, or components used in the practice of the present invention, in addition to those not specifically recited, may be varied, or otherwise particularly adapted to specific environments, manufacturing specifications, design parameters, or other operating requirements without departing from the general principles of the same.
Moreover, reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” Unless specifically stated otherwise, the term “some” refers to one or more. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is intended to be construed under the provisions of 35 U.S.C. § 112(f) as a “means-plus-function” type element, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for.”
This application claims priority under 35 U.S.C. § 119 to U.S. Provisional Application No. 63/395,480 entitled, “Systems and Methods for an Electrostatic Atomizer of Moderately Conductive Fluids,” filed Aug. 5, 2022, and hereby expressly incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| 63395480 | Aug 2022 | US |
