Patent Application
20070248470
The present invention relates generally to cavitation processes and, more particularly, to a method and apparatus for loading a source gas into a cavitation system.
Sonoluminescence is a well-known phenomena discovered in the 1930's in which light is generated when a liquid is cavitated. Although a variety of techniques for cavitating the liquid are known (e.g., spark discharge, laser pulse, flowing the liquid through a Venturi tube), one of the most common techniques is through the application of high intensity sound waves.
In essence, the cavitation process consists of three stages; bubble formation, growth and subsequent collapse. The bubble or bubbles cavitated during this process absorb the applied energy, for example sound energy, and then release the energy in the form of light emission during an extremely brief period of time. The intensity of the generated light depends on a variety of factors including the physical properties of the liquid (e.g., density, surface tension, vapor pressure, chemical structure, temperature, hydrostatic pressure, etc.) and the applied energy (e.g., sound wave amplitude, sound wave frequency, etc.).
It is generally recognized that during the collapse of a cavitating bubble extremely high temperature plasmas are developed, leading to the observed sonoluminescence effect. This phenomena is at the heart of a considerable amount of research as scientists and engineers attempt to both completely characterize the phenomena and find applications for it. Noted applications include sonochemistry, chemical detoxification, ultrasonic cleaning and nuclear fusion.
U.S. Pat. No. 4,333,796 discloses a cavitation chamber comprised of a refractory metal such as tungsten, titanium, molybdenum, rhenium or some alloy thereof. Acoustic energy is supplied to the liquid (e.g., lithium or an alloy thereof) within the chamber by six metal acoustic horns coupled to transducers. The tips of the horns project into the chamber while the rearward portion of each horn is coupled to a heat exchanger system, the heat exchanger system withdrawing heat generated by the reactions within the chamber. The inventors note that by removing heat in this manner, the liquid remains within the chamber, thus avoiding the need to pump the chamber liquid. In one disclosed embodiment, the source (i.e., deuterium) is introduced into the cavitation medium through a conduit attached to the top of the chamber, the concentration of the source being controlled by the dissociation pressure over the surface of the host liquid. In an alternate disclosed embodiment, an external processing system with a combination pump and mixer removes deuterium and tritium gases released from the cavitation zone and trapped within the chamber or tritium gases trapped within the Li-blanket surrounding the chamber and then reintroduces the previously trapped deuterium and tritium into the cavitation zone via a conduit coupled to the cavitation chamber. Additional deuterium may also be introduced into the mixer.
U.S. Pat. No. 4,563,341, a continuation-in-part of U.S. Pat. No. 4,333,796, discloses a slightly modified, cylindrical cavitation chamber. The chamber is surrounded by an external heating coil which allows the liquid within the chamber to be maintained at the desired operating temperature. The system is degassed prior to operation by applying a vacuum through a duct running through the cover of the chamber. During operation, the inventor notes that graphite, dissolved in the host liquid metal, is converted to diamond. The diamond-rich host material is removed via an outlet duct adjacent to the bottom of the chamber and graphite-rich host material is removed via an outlet duct adjacent to the upper end of the chamber. Additional host material and graphite are added by lowering rods comprised of the host material and graphite, respectively, into the heated chamber.
U.S. Pat. No. 5,659,173 discloses a sonoluminescence system that uses a transparent spherical flask fabricated from Pyrex®, Kontes®, quartz or other suitable glass and ranging in size from 10 milliliters to 5 liters. The inventors disclose that preferably the liquid within the flask is degassed and the flask is sealed prior to operation. In one disclosed embodiment, the cavitation chamber is surrounded by a temperature control system, thus allowing the liquid within the chamber to be cooled to a temperature of 1° C. Bubbles are introduced into the cavitation fluid using a variety of techniques including dragging bubbles into the fluid, for example with a probe, and localized boiling.
U.S. Pat. No. 5,858,104 discloses a shock wave chamber partially filled with a liquid. The remaining portion of the chamber is filled with gas which can be pressurized by a connected pressure source. Acoustic transducers mounted in the sidewalls of the chamber are used to position an object within the chamber while another transducer delivers a compressional acoustic shock wave into the liquid. A flexible membrane separating the liquid from the gas reflects the compressional shock wave as a dilatation wave focused on the location of the object about which a bubble is formed.
U.S. Pat. No. 5,968,323 discloses a cavitation chamber filled with a low compressibility liquid such as a liquid metal, the chamber enclosed within a temperature controlled container. A sealed fluid reservoir is also enclosed within the temperature controlled container, the reservoir connected to the bottom of the cavitation chamber by a pipe. By pressurizing or evacuating the reservoir, fluid can be forced into or withdrawn from the cavitation chamber. Fluid flow into or out of the chamber is aided by a vacuum pump and a pressurized gas source coupled to the top of the cavitation chamber. The system includes two material delivery systems for introducing materials or mixtures of materials into the chamber. One of the delivery systems is coupled to the bottom of the chamber and is intended for use with materials of a lower density than that of the cavitation liquid, thus causing the material to float upwards. The second delivery system is coupled to the top of the chamber and is intended for use with materials of a higher density than that of the cavitation liquid, thus causing the material to sink once introduced into the chamber.
PCT Application No. US02/16761 discloses a nuclear fusion reactor in which at least a portion of the liquid within the reactor is placed into a state of tension, this state of tension being less than the cavitation threshold of the liquid. The liquid preferably includes enriched deuterium or tritium, the inventors citing deuterated acetone as an exemplary liquid. In at least one disclosed embodiment, acoustic waves are used to pretension the liquid. After the desired state of tension is obtained, a cavitation initiation source, such as a neutron source, nucleates at least one bubble within the liquid, the bubble having a radius greater than a critical bubble radius. The nucleated bubbles are then imploded, the temperature generated by the implosion being sufficient to induce a nuclear fusion reaction.
PCT Application No. CA03/00342 discloses a nuclear fusion reactor in which a bubble of fusionable material is compressed using an acoustic pulse, the compression of the bubble providing the necessary energy to induce nuclear fusion. The nuclear fusion reactor is spherically shaped and filled with a liquid such as molten lithium or molten sodium. A pressure control system is used to maintain the liquid at the desired operating pressure. To form the desired acoustic pulse, a pneumatic-mechanical system is used in which a plurality of pistons associated with a plurality of air guns strike the outer surface of the reactor with sufficient force to form a shock wave within the liquid in the reactor. In one disclosed embodiment, the spherical reactor is coupled to a fluid flow circuit in which a pump and a valve control the flow of fluid. A reservoir containing a fusionable material, preferably in gaseous form, is in communication with the fluid flow circuit. When desired, a bubble of the fusionable material, preferably encapsulated in a spherical capsule, is released from the reservoir and into the fluid flow circuit, which then injects the bubble into a port at the bottom of the chamber.
Co-pending U.S. patent application Ser. No. 11/001,720, filed Dec. 1, 2004, discloses a system for circulating cavitation fluid within a closed-loop fluid circulatory system coupled to the cavitation chamber. Cavitation fluid can be circulated throughout the system before, during or after cavitation chamber operation. As disclosed, a network of conduits couples the cavitation chamber to a cavitation fluid reservoir and at least one external fluid pump. Manipulation of various valves within the conduit network allows the cavitation fluid to either be pumped from the reservoir into the cavitation chamber or from the cavitation chamber into the reservoir. The disclosed system provides a means of draining and/or filling the cavitation chamber with minimal, if any, exposure of the cavitation fluid to the outside environment.
Although a variety of sonoluminescence systems have been designed, they do not provide an efficient system for introducing a source, e.g., a reactant, into the cavitation medium. Accordingly, what is needed is a cavitation system that can be used for source loading. The present invention provides such a system.
The present invention provides a system and method of use for a cavitation system in which a source gas, e.g., a reactant, is loaded into the cavitation medium prior to cavitation. The cavitation system of the invention includes a cavitation chamber with suitable cavitation drivers and a pressurized gas source coupled to the chamber. A valve interposed between the source gas and the cavitation chamber controls the loading process in which the cavitation medium is loaded with the desired reactant (i.e., the source gas). In another aspect of the invention, a vacuum system is coupled to the cavitation system for use during degassing procedures. The vacuum system may include a cold trap. Preferably multiple valves are used to couple/de-couple the vacuum system and the gas source to the cavitation system when required, for example as a means of protecting pressure and vacuum gauges attached to the system.
In one embodiment of the invention, the cavitation medium (e.g., metal, salt) has a melting temperature higher than the ambient temperature. In order to accommodate such a medium, the cavitation chamber and the cavitation medium fill reservoir as well as any coupling conduits in which the cavitation fluid is expected to flow are heated to a temperature greater than the melting temperature of the intended cavitation medium. Preferably in this embodiment the system components that must be heated are located within an oven. Alternately the desired temperature can be reached using localized heaters to heat the cavitation chamber, fill reservoir and those portions of the conduits through which the cavitation fluid must pass.
In another embodiment of the invention, a method of loading a cavitation medium with a source, e.g., reactant, is provided. The cavitation system is first filled with sufficient cavitation fluid to fill the cavitation chamber to the desired operating capacity (e.g., full, partially full). After filling to the desired level, the system is sealed and degassed. Cavitation may be used to aid the degassing procedure. The cavitation medium is then loaded with the desired source, e.g., reactant, by pressurizing the system with the desired gas. The cavitation process is then initiated in the cavitation chamber. Depending upon the melting temperature of the cavitation medium, this embodiment of the invention may also include the step of heating the cavitation medium as well as all components through which the cavitation medium flows.
A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings.
In illustrated system 100 as well as at least one preferred embodiment of the invention, cavitation chamber 101 is a spherical chamber. It will be appreciated, however, that the invention is not limited to spherical chambers, rather chamber 101 can utilize any chamber design which is suitable for the intended cavitation process. Examples of other configurations include cylindrical chambers, hourglass-shaped chambers, conical chambers, cubical chambers, rectangular chambers, irregularly-shaped chambers, etc. One method of fabricating chamber 101 is described in detail in co-pending U.S. patent application Ser. No. 10/925,070, filed Aug. 23, 2004, entitled Method of Fabricating a Spherical Cavitation Chamber, the entire disclosure of which is incorporated herein for any and all purposes. Examples of hourglass-shaped chambers are provided in co-pending U.S. Patent application Ser. No. 11/140,175, filed May 27, 2005, entitled Hourglass-Shaped Cavitation Chamber, and Ser. No. 11/149,791, filed Jun. 9, 2005, entitled Hourglass-Shaped Cavitation Chamber with Spherical Lobes, the entire disclosures of which are incorporated herein for any and all purposes. An example of a cylindrical cavitation chamber is provided in co-pending U.S. patent application Ser. No. 11/038,344, filed Jan. 18, 2005, entitled Fluid Rotation System for a Cavitation Chamber, the entire disclosure of which is incorporated herein for any and all purposes.
Chamber 101 can be fabricated from any of a variety of materials, depending primarily upon the desired operating pressure and temperature of the chamber and system. Preferably the selected material is machinable, thus simplifying fabrication, and corrosion resistant, thus allowing the chamber to be used repeatedly with a variety of liquids. Typically a metal, for example 17-4 precipitation hardened stainless steel, is used for chamber 101.
The selected dimensions of chamber 101 depend primarily on the intended use of the chamber, although the cost of the cavitation fluid, chamber fabrication issues, operating temperature and cavitation driver capabilities also influence the preferred dimensions of the chamber for a specific process. In general, small chambers are preferred for situations in which it is desirable to limit the amount of the cavitation medium or in which driver input energy is limited while large chambers (e.g., 10 inches or greater) are preferred as a means of simplifying experimental set-up and event observation or when high energy reactions are being driven within the chamber. Thick chamber walls are preferred in order to accommodate high pressures.
Conduit 103 allows the system to be coupled to a vacuum system for evacuation and coupled to a pressurized gas system for supplying the desired gas for loading the cavitation medium. Although not preferred, it should be understood that the gas loading system and the degassing system (i.e., vacuum pump) can be attached to system 100 (e.g., conduit 103) in separate locations. Conduit 103 can also be used to fill the system with the cavitation medium. Alternately a separate cavitation medium filling system can be used as described in further detail below.
In the preferred embodiment, conduit 103 tees or splits into two branches, conduit 105 leading to the vacuum system and conduit 107 leading to the gas loading system. A three-way valve 109 allows the system to be coupled to the ambient atmosphere via conduit 111 or to vacuum pump 113. It will be appreciated that three-way valve 109 can be replaced with a pair of two-way valves (not shown). Valve 115 provides a means for isolating the system from pump 113. Preferably a trap 117 insures that cavitation fluid is not drawn into vacuum pump 113 or vacuum gauge 119. Preferably trap 117 is cooled so that any cavitation medium entering the trap solidifies. Typically at least one vacuum gauge 119 is used to provide an accurate assessment of the system pressure. Once the cavitation system is pressurized, prior to re-coupling the system to either vacuum gauge 119 or vacuum pump 113, the cavitation system pressure is bled down to an acceptable level using three-way valve 109.
A high pressure gas source 125 is coupled to the cavitation system. Preferably a three-way valve 121 allows high pressure gas source 125 to be coupled to the system or to the ambient atmosphere via conduit 123. It will be appreciated that three-way valve 121 can be replaced with a pair of two-way valves (not shown). Conduit 123 and the associated valve allows the pressure to be bled from the high pressure system prior to changing source 125 or otherwise working on the high pressure system. A pressure regulator 127 is used to control the output pressure of source 125. Valve 129 controls the output of source 125. Typically at least one pressure gauge 131 is used to monitor the system pressure.
If the system does not exhibit any leaks while evacuated or pressurized, or after any leaks have been fixed, it is then filled with the cavitation medium (step 203). The system is filled with sufficient cavitation medium to fill cavitation chamber 101 to the desired operating level. It will be appreciated that the operating level for chamber 101 is based on obtaining the most efficient cavitation action. For example, while a spherical chamber (e.g., the chamber shown in
System 100 can be filled, for example, via conduit 111. Alternately system 100 can be coupled to a filling or a filling/degassing system. For example, in the system illustrated in
In the system illustrated in
In the system illustrated in
After system 100 is filled, the system is sealed and degassed using vacuum pump 113 (step 205). This step typically takes between 30 and 60 minutes, depending primarily upon the capacity of pump 113, the volume of chamber 101, and the vapor pressure of the cavitation fluid. In general, the system is pumped down to the limits of the vacuum pump (e.g., less than 1 mm of mercury for liquid metals) or to the vapor pressure of the liquid.
After degassing step 205, a determination is made as to whether additional degassing is required (step 207). In general, the amount of degassing that is required depends on the sensitivity of the reactants to the presence of oxygen and nitrogen (i.e., the greater the sensitivity to oxygen and nitrogen, the greater the need for degassing). If additional degassing is warranted, preferably cavitation using a cavitation driver(s) coupled to chamber 01 is used to tear vacuum cavities within the cavitation medium (step 209). As the newly formed cavities expand, gas from the fluid that remains after the initial degassing step enters into the cavities. During cavity collapse, however, not all of the gas re-enters the fluid. Accordingly a result of the cavitation process is the removal of dissolved gas from the cavitation fluid via rectified diffusion and the generation of bubbles. Preferably the cavitation degassing step is performed repeatedly (step 211) until all of the cavitation medium is sufficiently degassed.
The cavitation fluid is preferably degassed within chamber 101 as described above. It should be appreciated, however, that degassing can be performed within the reservoir (e.g., reservoir 401) prior to filling chamber 101 with the cavitation fluid. In this instance if additional degassing via cavitation is required, either chamber 101 can be filled after the initial degassing step or the degassing via cavitation step (i.e., step 209) can be performed within the reservoir (e.g., reservoir 401), assuming that at least one cavitation driver is coupled to the reservoir (not shown). This approach is not, however, preferred as it does not eliminate the need for drivers 133 which are required for the desired cavitation process.
As previously described, cavitation as a means of degassing the fluid is typically performed within cavitation chamber 101 using one or more cavitation drivers 133. Clearly the invention is not limited to a specific number, type or location of driver. Examples of suitable drivers are given in co-pending U.S. patent application Ser. No. 10/931,918, filed Sep. 1, 2004, entitled Acoustic Driver Assemblyfor a Spherical Cavitation Chamber; Ser. No. 11/123,388, filed May 5, 2005, entitled Acoustic Driver Assembly With Recessed Head Mass Contact Surface; and Ser. No. 11/068,080, filed Feb. 28, 2005, entitled Hydraulic Actuated Cavitation Chamber, the disclosures of which are incorporated herein in their entirety for any and all purposes. Preferably for high vapor pressure liquids, prior to optional step 209 the use of vacuum pump 113 is temporarily discontinued, for example by closing valve 115 and turning off the pump, thereby minimizing the loss of cavitation medium through boiling. For low vapor pressure liquids such as liquid metals, vacuum pump 113 can be operated continuously. After the fluid within chamber 101 is cavitated for a period of time, typically for at least 5 minutes and preferably for more than 30 minutes, the newly created bubbles float to the top of the chamber due to their buoyancy. The gas removed from the fluid during this step is periodically removed from the cavitation system using vacuum pump 113. Typically the vacuum pump is only used after there has been a noticeable increase in pressure within system 100, preferably an increase of at least 0.2 psi over the vapor pressure of the cavitation fluid, alternately an increase of at least 0.02 psi over the vapor pressure of the cavitation fluid, or alternately an increase of a couple of percent of the vapor pressure. Preferably the use of cavitation as a means of degassing the cavitation fluid is continued until the amount of dissolved gas within the cavitation fluid is so low that the fluid will no longer cavitate at the same cavitation driver power.
Once system 100 is sufficiently degassed via step 205 and, if desired, optional step 209, system 100 is sealed off from the vacuum system, for example using valve 109 (step 213), thereby protecting sensitive vacuum gauge 119. Then system 100 is pressurized with the desired source (i.e., reactant) gas 125 to the desired pressure in order to load the cavitation medium with the source gas (step 215). In one preferred embodiment, the desired system pressure is between 500 and 1000 psi and source gas 125 is deuterium gas. If desired, source gas 125 can be a mixture of gases.
After completion of step 215, cavitation drivers 133 are used to cavitate the cavitation medium contained within chamber 101. In a preferred embodiment, however, the concentration of non-source gas in the cavitation medium is further decreased by isolating the cavitation system from the high pressure source and repeating the degassing steps. Once again step 209 is optional. After this degassing step, system 100 is once again sealed off from the vacuum system and then pressurized with source gas 125.
At this point the cavitation system is ready to perform the desired cavitation reactions within chamber 101. Accordingly the cavitation medium within chamber 101 which has been loaded with source gas 125 is cavitated using driver(s) 133, the high intensity cavitation driven implosions within the cavitation medium driving the desired reactions (step 217).
As the cavitation driven reactions take place and bubbles are formed and cavitated within the medium, the cavitating medium slowly becomes depleted of source gas 125. After the cavitation medium has been sufficiently depleted of source gas 125, either experiments are terminated (step 219) or the cavitation fluid must be reloaded (step 215). If the reaction products are gaseous, then preferably the medium is degassed (step 205) prior to reloading the system.
During cavitation step 217, the inventor has found that slowly bleeding system 100, for example by opening valve 121 to conduit 123 and lowering the pressure at a rate of approximately 10 psi per hour, leads to improved bubble formation (optional step 221).
It should be understood that cavitation system 100 is not limited to one specific cavitation fluid. The primary limitation placed on the cavitation medium is the temperature capabilities of system 100 since the system, as shown, is only capable of operating at ambient temperature. In order to use the system for higher temperature applications, in particular those in which the cavitation medium must be heated in order to change phases from solid to liquid, at least a portion of the cavitation system must be heated. To simplify the design and fabrication of a system capable of operating at elevated temperatures, preferably the melting point of the cavitation media is relatively low (e.g., mercury or a cerro metal such as cerrobend). Higher melting point metals or salts can be used if the system is capable of operating at or above the melting point of the desired metal or salt.
As previously noted, the present apparatus and source loading method can be used with liquid metals, including those metals that have a melting point higher than the ambient temperature.
Although the inventor has found that the systems shown in
Regardless of the method of heating (i.e., oven, localized heaters, etc.), in addition to heating chamber 101 it is necessary to heat the initial cavitation fluid filling reservoir as shown in the embodiments of
The use of the heated system as illustrated in
As will be understood by those familiar with the art, the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the disclosures and descriptions herein are intended to be illustrative, but not limiting, of the scope of the invention which is set forth in the following claims.
