Patent Application
20140070018
Current aerosol technology has n evolved to include a plurality of aerosol dry powders or nano-particles without the use of a solvent or a propellant that suspends or combines with the powders or nano-particles to be dispersed.
It is an object of the present invention to provide a device and method for aerosol dispensing of a plurality of dry powders and nano-materials that utilizes current aerosol technology that has not evolved to include aerosol dry powders or nano-particles without the use of a solvent or a propellant that suspends or combines with the powders and nano-materials dispersed by aerosol.
It is an object of the present invention to provide a device and method for aerosol dispensing of a plurality of dry powders and nano-materials that allows for a plurality of powders and nano-particles with relatively widely differing properties to be dispersed by aerosol that include pharmaceuticals, paint powders, silicates, nano-particles, CNFs, graphenes, oxides and nano-scale metals.
It is an object of the present invention to provide a device and method for aerosol dispensing of a plurality of dry powders and nano-materials that is a relative improvement over dry powder dispensing such as siphon aerosols or bag on valve systems.
What is needed is a device and method for aerosol dispensing of a plurality of dry powders and nano-materials that utilizes current aerosol technology that has evolved to include aerosol dry powders or nano-particles without the use of a solvent or a propellant that suspends or combines with the powders and nano-materials dispersed by aerosol that allows for a plurality of powders and nano-particles with relatively widely differing properties to be dispersed by aerosol that include pharmaceuticals, paint powders, silicates, nano-particles, CNFs, graphenes, oxides and nano-scale metals that is a relative improvement over dry powder dispensing ouch as a siphon aerosols or a bag on valve systems.
The present invention will be described by way of exemplary embodiments, but not limitations, illustrated in the accompanying drawing in which like references denote similar elements, and in which:
Various aspects of the illustrative embodiments will be described using terms commonly employed by those skilled in the art to convey the substance of their work to others skilled in the art. However, it will be apparent to those skilled in the art that the present invention may be practiced with only some of the described aspects. For purposes of explanation, specific numbers, materials and configurations are set forth in order to provide a thorough understanding of the illustrative embodiments. However, it will be apparent to one skilled in the art that the present invention may be practiced without the specific details. In other instances, well-known features are omitted or simplified in order not to obscure the illustrative embodiments.
Various operations will be described as multiple discrete operations, in turn, in a manner that is most helpful in understanding the present invention. However, the order of description should not be construed as to imply that these operations are necessarily order dependent. In particular, these operations need not be performed in the order of presentation.
The phrase “in one embodiment” is used repeatedly. The phrase generally does not refer to the same embodiment, however, it may. The terms “comprising”, “having” and “including” are synonymous, unless the context dictates otherwise.
The powder aerosol device 100 includes a cylindrical vessel 110 and a nozzle 120. The cylindrical vessel 110 has a top portion 112 with a middle 114 and is described and illustrated in additional detail in subsequent
The powder aerosol device 100 includes a cylindrical vessel 110 and a nozzle 120 illustrated and described in
The powder aerosol device 100 additionally includes a propellant chamber 130, a cylinder 140, a piston 150 and a plurality of apertures 160. The propellant chamber 130 contains a propellant that can be a compressed gas, a phase change material or a refrigerant. The compressed gas can be nitrogen, argon, carbon dioxide or any other suitable compressed gas. The phase change material can be hydrofluoroalkane-134a or HFO-134a, 2,3,3,3-Tetrafluoropropene or HFO-1234yf, a refrigerant or any suitable phase change material. The refrigerant can be any suitable refrigerant. The cylinder 140 contains the plurality of dry powders and nano-materials 124 to be dispersed by aerosol 142 to ambient 144. Within the cylinder 140 is the piston 150 that moves the plurality of dry powders and nano-materials 124 or pressure drop end pushing the plurality of dry powders and nano-materials 124 toward the nozzle 120 (path to ambient) for more effective gas and powder entrainment effects. The propellant stream is passed through the plurality of apertures 160 disposed on the piston 150 which has a dual effect of fluidizing the plurality of dry powders and nano-materials 124 and providing a gas stream for aerosolization gas flow through the plurality of dry powders and nano-materials 124 and out the nozzle 120. Pressure is created by propellant passing through the plurality of apertures 160. Pressure behind the piston 150 moves it upward keeping the plurality of dry powders and nano-materials 124 moving upward toward the nozzle 120. The gas pressure is higher behind the piston 150 than within the cylinder 140 thereby forcing the piston 150 upward. The advantage to the powder aerosol device 100 is that all the plurality of dry powders and nano-materials 124 will be dispersed by aerosol 142.
The powder aerosol device 100 is set in motion by the pressure drop created when the nozzle 120 is opened to ambient 144. Conversely the powder aerosol device 100 is stopped when the nozzle 120 is closed to ambient 144. This capability allows for a continuous or start and stop operation and the nozzle valve 122 can be one of many suitable configurations with a variety of patterned spray.
The method 200 steps include converting a granular material from a static solid-like state to a dynamic fluid-like state 210, presenting a powder material to an nozzle of the powder aerosol device that releases a propellant and the powder to ambient 220 and using a single gas stream to move the powder material, fluidize the powder material and provides an entrainment gas stream propelling the powder material to the ambient 230. The converting step 210 includes passing a fluid through the granular material. The presenting step 220 includes the powder material is a plurality of dry powders and nano-materials and the propellant is a compressed gas, a phase change material or a refrigerant. The using step 230 includes the entrainment gas stream propelling the powder material through a nozzle provided on the powder aerosol device to the ambient.
The powder aerosol device is capable of efficiently fluidizing, aerosolizing and disseminating various micro-sized and nano-sized powders that fall into a category of materials referred to as Geldart Group C Powders. Geldart Group C Powders are known as particularly difficult to fluidize, aerosolize and pneumatically transport in nearly all applications. An object of the research and development of the powder aerosol device is to develop and demonstrate an obscurant grenade device that enables in-canister fluidization of dry powder obscurant (PO), a Geldart Group C Powder, using compressed gas and if necessary mechanical vibration or agitation of the PO powder to enhance fluidization. Efficient pneumatic transport of PO powder is achieved by fluidizing and suspending the powder followed by entraining the suspended PO powder in the fluidization gas and ejecting it from the canister through a Venturi tube, dissemination nozzle or canister orifice. The concept of a powder fluidization grenade (PFG) was developed for particulate obscurant dissemination. A primary goal of its R&D effort was to facilitate continuous and uniform dissemination of an approximate 200 cc charge of Titanium Dioxide (TiO2) PO powder from an approximate Coke can sized canister over an approximate 30 second period. In order to achieve the goal, engineering analysis was first conducted and ANSYS computational fluid dynamics (CFD) simulations of PO powder fluidization quality (FQ) within a 3-dimensional computer aided design (CAD) finite element (FE) model of the PFG canister were performed. These models included the characterization of powder fluidization, powder entrainment into the fluidization gas stream and dissemination of the powder and gas mixture from the PFG canister nozzle. After successfully establishing the efficacy of the PFG concept using a plurality of ANSYS models, several PFG prototype variant devices were designed and fabricated with which to conduct laboratory testing, produce photographic and video documentation of PFG performance and perform data analysis. When fully developed and deployed, the PO powder fluidization grenade (PFG) described and detailed herein will provide the following benefits over currently deployed obscurant grenade systems:
The data analysis of PFG models created and simulated using ANSYS software provided strong evidence that PO powder fluidization, entrainment and dissemination could be accomplished using an appropriately designed PFG device powered by a compressed carrier gas. To that end, began the design and fabrication of an initial PFG prototype. The initial PFG prototype, designated PFG Prototype No. 1 (PFG1), was tested and demonstrated that approximately 200 cc of TiO2 obscurant powder could be disseminated from the PFG canister using a compressed air source. The rate at which powder dissemination occurred within PFG1, however, was insufficient for practical use due in large part to the small diameter of the PFG venture nozzle orifice. A second PFG variant design, designated PFG Prototype No. 2 (PFG2), excluded the Venturi section of PFG1 and instead utilized an approximate 0.150 inch diameter cylindrical nozzle located atop the canister for powder dissemination. Removal of the Venturi from the PFG2 design was beneficial in two ways: it eliminated the need for a second air supply plenum to deliver air to the Venturi throat and it reduced the PFG bill of materials (BOM) part count. This configuration performed significantly better than the Venturi equipped PFG1 in rapidly disseminating powder from the canister. Having documented the excellent performance of PFG2, a perforated HDPE liner was installed inside the PFG2 canister to assist in powder fluidization and entrainment, thereby increasing the mass flow rate of powder disseminated through the canister nozzle. Testing results for this variant, a designated PFG Prototype No. 3 (PFG3) was characterized by a significantly greater rate of powder mass entrainment and more rapid and consistent powder dissemination from the canister than that observed in PFG2 testing. PFG 1, PFG2 and PFG3 were all tested using a constant source of pressurized air from a manufacturing plant compressor system.
Because of the exceptional performance of PFG3 while powered by the manufacturing plant compressed air, this prototype was provided with a gas pressure regulator and fittings necessary for operation with an approximate 850 psi gas cartridge containing approximately 74 grams of Carbon Dioxide (CO2) gas. Testing results of this PFG3 variant revealed that after approximately 2 or 3 seconds of CO2 gas flow into PFG3, relatively very good fluidization and dissemination of powder was established through the nozzle. It was noted however, that relatively good quality powder fluidization and dissemination lasted only approximately 10 seconds, after which the cartridge gas pressure dropped significantly due to CO2 mass depletion. During this test only approximately 50 cc of powder was entrained and disseminated from PFG3, an unsatisfactory performance yield as compared to the compressed air PFG3 variant. Confident that optimization of powder bed geometry could facilitate rapid powder entrainment and dissemination from PFG3 when powered by approximately 74 grams of compressed CO2, a PFG3 redesign focused in three areas:
The resulting PFG variant, PFG prototype No. 4 (PFG4), was derived from the notion that the HDPE liner of PFG3 could be replaced by a device that dynamically reduced the volume of the powder bed at a rate proportional to which powder mass is disseminated from the canister. To test this principle, an approximate 50 cc HDPE syringe was obtained with a rubber plunger. The syringe and plunger were modified with a series of apertures allowing the flow of pressurized gas to fluidize and entrain powder while also driving the plunger forward to reduce the bed volume at a rate proportional to powder mass dissemination. Functioning as a powder syringe, PFG4 containing an approximate 50 cc charge of TiO2 powder and powered by a single approximate 74 gram, 850 psi CO2 cartridge was tested. Results of the PFG4 testing showed complete dissemination of the approximate 50 cc TiO2 powder charge in only approximately 5 seconds. Supported by its relatively promising performance during in-house testing, the PFG4 powder syringe design will facilitate development of a wholly self-contained PFG of approximate Coke can-sized dimensions that can disseminate an approximate 200 cc charge of TiO2 obscurant powder within approximately 30 seconds without the use of energetic components.
Inserted through the center of the PFG canister body is a plenum tube that supplies pressurized gas to the Venturi section by a dedicated air supply. The fluidization gas supply is separate from the Venturi plenum supply so as to enable independent control of both fluidization and Venturi gas flow and pressure. The arrows in
The left side of
The results of the ANSYS modeling and simulation work are obtained by obtaining components necessary to fabricate a PFG1 prototype. A PFG1 laboratory scale prototype was designed to provide a versatile and reusable platform to perform actual powder fluidization while observing the fluidization and Venturi effects described in CFD simulations.
After the PFG1 prototype was completed a preliminary operational test was performed using a titanium dioxide powder CR826 obtained from Tronox, Inc. The average powder particle size was approximately 0.2 μm. Other preliminary test parameters include:
Additional testing of PFG1 was conducted using various fluidization and Venturi plenum flow rates and pressures. The initial mass of TiO2 within the PFG1 canister prior to each test was held constant at approximately 200 cc. While varying air pressure and flow, PFG1 was tested for both the quality and rate of PO powder mass dissemination in both horizontal and vertical spatial orientations. In the vertical orientation, it was discovered that regardless of the air pressure and flow rate combinations used, the time required to empty approximately 200 cc of PO powder from the PFG canister significantly exceeded the approximate 30 second threshold. The quality of the powder/air dissemination stream was considered from the Venturi nozzle to be relatively excellent, with a relatively high velocity powder/air stream reaching as much as approximately 15 vertical feet. It was recognized however, that in each test the concentration of powder in the stream was relatively very dilute, owing to the protracted time required to discharge the entire mass of powder within the canister. From these tests, it was also determined that the well suited fluidization air pressure was in the approximately range of 20-30 psi. Fluidization air pressures approximately below 20 psi failed to establish high fluidization quality (FQ) of the powder, while those approximately above 30 psi resulted in the formation of powder channeling and slugging within the canister. Overall, the performance of PFG 1 in the vertical orientation was deemed to be inadequate due to the relatively low mass flow rate of powder discharged from the canister.
In horizontal orientation, the PFG prototype performed relatively poorly as well. While the relative quality of powder/air dissemination stream was once again relatively good, with the relatively high velocity stream reaching approximately 15 feet horizontal from the Venturi nozzle, the stream was even more relatively dilute than in the vertical orientation tests. It was found that constant vibration of the PFG canister while held by hand was needed to assist powder fluidization so that it could be entrained by the Venturi. After numerous tests and observations, it was calculated that the jet orifice of the PFG1 prototype Venturi was relatively too small to entrain a sufficient concentration of powder into the throat for rapid dissemination by the Venturi nozzle. The Venturi was removed from the PFG1 prototype in anticipation of installing and testing a Venturi with relatively larger jet and nozzle dimensions. Parameters and results of the testing of PFG1 are summarized below:
The relatively dilute TiO2 concentration and protracted rate of powder discharge from the canister during PFG1 testing considers the inherent limitations in the rate at which powder is entrained and disseminated from a Venturi nozzle. While awaiting delivery of a relatively larger Venturi, several tests were run in which the canister cap penetration would serve as the PFG nozzle. With the Venturi removed and no requirement for plenum air, the plenum tube was removed from the center of the canister and the plenum tube air supply penetration at the bottom of the canister was capped. The fluidization air supply tube and air distribution plate was left in place. This PFG prototype variant, designated as PFG2 is illustrated below in FIG. 5.0.
After being loaded with approximately 200cc charge of TiO2 powder, testing was conducted of PFG2 within an industrial paint booth. The parameters utilized for PFG2 testing included:
During this test, fluidization air pressure was relatively increased from approximately 5 psi to 60 psi while photographing and digitally filming the test process and powder behavior within the canister. In vertical orientation, the best powder fluidization and dissemination performance occurred at approximately 40 psi fluidization air pressure, during which the powder stream exiting the nozzle became relatively very concentrated and created a relative thick opaque cloud. The bulk of the powder was discharged from the canister within approximately 60 seconds of the start of powder dissemination at the nozzle. After completing this test, it was determined that approximately 15% of the initial powder charge was left inside the canister, with approximately 85% or approximately 170 cc of the powder having been disseminated through the nozzle within the approximate 60 second discharge period. At the conclusion of this test, it was clear that removal of the entire Venturi from the PFG1 produced a much larger and more concentrated stream of powder, while powder fluidization quality within the canister was maintained. PFG2 was next tested in the horizontal orientation. As with the vertical orientation test, increased fluidization air pressure was relatively slowly increased and made flow adjustments until the relative best visible powder stream was established. While a relatively good quality powder stream having relatively high powder concentration was initially observed, the stream quickly became dilute over a period of approximately 15-20 seconds until the bulk of the stream was fluidization air. Engineers quickly realized that when rotated approximately 90 degrees from vertical, the bulk of powder settled along the wall of the cylindrical canister and was no longer in the direct path of fluidization air. Having no options to solve this issue given the PFG2 design, several alternative designs were considered for additional testing that could facilitate powder fluidization with the canister in the horizontal position. Testing parameters and results of the testing of PFG Prototype No. 2 are summarized below:
Because of the excellent performance of PFG2 when tested in the vertical orientation, an air flow analysis of PFG2 was conducted to develop an alternative fluidization air distribution regime. The goal was to develop uniform air flow distribution within the canister to facilitate relatively rapid fluidization and dissemination in the horizontal. After testing several air distribution methods, a make-shift canister liner was developed and fabricated from an approximate 2.375 inch diameter high density polyethylene (HDPE) laboratory bottle. Ten (10) small drill holes were placed in the bottle, located approximately 0.5 inch from the bottom and equally spaced around the bottle circumference. Four (4) equally spaced holes were drilled around the bottle neck. In laboratory tests, this configuration provided a relatively uniform flow of air through the entire cross section of the bottle liner that engineers believed would prevent stagnation of powder movement when the canister was oriented horizontal.
Testing began of PFG3 in the vertical orientation. Fluidization relatively slowly increased air flow into PFG Prototype No. 3 from approximately in the range 5 psi to 40 psi while photographing and filming the behavior of the powder. It's observed that at approximately 20 psi air pressure the powder fluidized uniformly and formed a very concentrated stream of powder from the canister nozzle. Additionally, the holes near the top of the bottle performed as expected in facilitating a relatively high velocity powder stream from the PFG. It was also observed that the HDPE bottle slightly contracted under approximately 20 psi of air pressure, reducing its cross sectional area by as much as approximately 15% thereby relatively increasing the velocity of fluidization air within the liner and improving fluidization and delivery of powder to the nozzle.
The canister liner was emptied of the bulk of the powder at approximately 27 seconds from initiation of stream formation with only approximately 20 cc of powder remaining in the canister liner at the end of the test. PFG3 was next tested in the horizontal orientation. As with the vertical orientation test, fluidization air pressure was relatively slowly increased and flow adjustments were made until the best visible powder stream was established. A relatively excellent quality powder stream with a relatively high concentration of powder solids was observed at approximately 20 psi fluidization air. The dissemination stream remained concentrated over the length of the test. Again, it was observed that the HDPE bottle slightly contracted approximately less than 20 psi of air pressure, reducing its cross sectional area by approximately 15%, thereby relatively increasing the velocity of fluidization air within the liner.
Testing parameters and results of the testing of PFG3 are summarized below:
Testing parameters and results of the testing of PFG3 are summarized below:
The relatively excellent performance of PFG Prototypes No. 2 and No. 3 in which the Venturi was removed which was believed that the use of a Venturi to facilitate powder entrainment and dissemination may not, in the end, be necessary for realization of a deployable PFG device. The rapid dissemination of powder from this prototype indicates that the complications associated with homogeneous blending of Aerosol glidant and TiO2 powder would not be necessary for the duration of the PFG R&D process. PFG3 testing results also conclude that design and implementation of a less complex PFG nozzle improved PFG performance while simplifying the PFG design, thus lower fabrication costs and improving PFG reliability. The integration of the HDPE liner into PFG3 proved to be a particular breakthrough in achieving complete and rapid powder fluidization within the PFG canister. This design modification may also eliminate the need for a relatively complex and expensive air distribution plate, further lowering costs and relatively increasing reliability.
In light of the relatively outstanding performance of PFG3 during compressed air testing, mass flow rate calculations were performed on the compressed air supplied to PFG3 and found that approximately 215 grams (0.47 lbs.) of air was consumed during the approximate 30 second event. Understanding that in practice, there will not be a constant supply of compressed gas to power the PFG, rather an onboard supply of limited size, PFG3 was reconfigured to operate using compressed carbon dioxide (CO2) gas supplied from an approximate 850 psi gas cylinder. The mass of CO2 contained within each cartridge is approximate 74 grams (0.16 lbs.), only approximately one-third of that used during the compressed air tests conducted on PFG3.
After filling PFG3 with approximately 200 cc of powder and setting the pressure regulator at approximately 25 psi, engineers opened the supply valve to the CO2 gas cartridge allowing a flow of gas into the PFG. After approximately 2 or 3 seconds of CO2 gas flow into the PFG, it was initially observed relatively very good fluidization and dissemination of powder through the nozzle. This relatively good quality powder fluidization and dissemination, however, lasted only approximately 10 seconds, after which pressure from the gas cartridge dropped significantly as a result of CO2 gas depletion. During this test only approximately 50 cc of powder was entrained and disseminated from PFG3 yielding relatively unsatisfactory performance as compared to the compressed air PFG3 variant. Testing parameters and results of testing of PFG3 affixed to the CO2 gas cartridge are summarized below:
Various mass transport calculations were performed to determine the reason for the relatively poor performance of this variant. While it was obvious that the CO2 gas cartridge provides only approximately one third of the gas mass consumed in the compressed air tests, it was thought that perhaps appropriate optimization of the PFG powder bed geometry and function could enable the PFG to entrain and disseminate powder using only approximately 74 grams of CO2. It was decided to focus on three relatively significant features of the PFG for optimization, including:
To achieve these goals, engineers conceptualized several new powder bed configurations. After considering which might provide the most relatively promising results, a new design was developed for PFG Prototype No. 4 (PFG4).
PFG4 was derived from the idea that the HDPE liner of PFG3 could be replaced by a device that dynamically contracts to relatively reduce the volume of the powder bed at a rate proportional to which powder mass is disseminated from the canister. The relative simplest manifestation of this idea is the operation of a plunger that relatively reduces the volume inside of a syringe as liquid material is discharged from it. To test this principle, an approximate 50 cc HDPE syringe was obtained with a rubber plunger. The syringe and plunger were modified with a series of holes allowing the flow of pressurized gas into the base of the syringe cylinder and through the plunger base to fluidize and entrain powder. As powder is fluidized in the syringe and disseminated from the syringe nozzle, the flow of pressurized gas also drives the plunger forward toward the syringe nozzle, relatively effectively reducing the bed volume at a rate proportional to powder mass dissemination. Eight evenly distributed approximate 0.06 in. diameter holes were drilled at the base of the syringe and below the plunger to allow the flow of pressurized air to enter the plunger base. Four evenly placed approximate 0.03 in. diameter holes were drilled in the plastic base of the plunger and three evenly placed approximate 0.03 in. diameter holes were drilled in the rubber plunger to allow gas flow into the powder bed formed by the syringe cylinder.
PFG4 was loaded with approximately 30 cc of Tronox CR826 TiO2 powder and connected to a supply of approximately 25 psi pressurized air. The testing parameters for PFG Prototype No. 4 testing included:
Testing parameters and results of PFG Prototype No. 4 are summarized below:
Approximately 30 cc charge of powder disseminated from PFG4 in only approximately 3.5 seconds. Owing to the relatively excellent results with an approximate 30 cc load of powder, it was decided to reload the PFG4 with approximately 50 cc of powder, which is the full capacity of the syringe, and retest its performance using compressed air. The parameters for this test included:
Testing parameters and results of testing of PFG Prototype No. 4 are summarized below:
This test shows the approximate 50 cc charge of powder disseminated from PFG4 in only approximately 8 seconds. After the successful test of PFG4 connected to a compressed air supply, PFG4 was reconfigured to operate powered by a single approximate 74 gram 850 psi CO2 cartridge.
Testing parameters and results of the testing of the Self-Contained Gas Cartridge PFG4 variant are summarized below:
This test shows that the PFG4 powered by a single approximately 74 gram, 850 psi CO2 cartridge completely disseminated the approximately 50 cc charge of powder in only approximately 5 seconds. This relatively successful test of the self-contained PFG4 is a technical success toward development of a wholly self-contained PFG prototype that can disseminate approximately 200 cc of obscurant powder in approximately 30 seconds.
PFG5 represent the culmination of the well suited features of PFG1 through PFG4 and incorporates a custom engineered and manufactured powder cylinder, piston and dissemination nozzle. This embodiment of PFG4 includes a powder containment cylinder and nozzle that can be manufactured of various materials, including plastics, metals or cellulose and designed in various geometries, including elliptical, rectangular or irregular shapes. Similarly, the PFG5 piston plunger can be manufactured of the same array of materials and designed to match the preferred cylinder geometric shape. PFG5 can be operated using a compressed gas source that is integrated into the unit or by a separate compressed gas source such as a compressed gas cylinder. Other embodiments of PFG5 will include a piston actuated by an explosive charge such that nearly instantaneous powder dissemination can be achieved as well as an embodiment in which the explosive charge itself produces a sufficient mass of gas products to facilitate powder fluidization, piston actuation and powder dissemination through the PFG nozzle. The PFG5 is designed and manufactured from custom components that significantly improve powder dissemination performance achieved during PFG4 testing and evaluation.
As part of the well-planned engineered design, prototype fabrication, testing and optimizing strategy with which PFG development was performed, the following has been achieved:
Through its iterative engineering design, prototype fabrication, testing and evaluation process, it has been shown that the PFG technology concept presented herein is a practical alternative to energetic actuation of obscurant grenades. Additionally, it has been established that efficient and cost effective pneumatic fluidization, processing, transport and dissemination of Geldart Group C powders is viable by the PFG device and its embodiments. While testing of PFG1, PFG2 and PFG3 proved that the concept was feasible, it was identified and reported the performance drawbacks of each prototype. These drawbacks included:
These drawbacks were successfully resolved through the successive redesign of each PFG prototype fabricated and tested. During the course of R&D efforts, it was found that certain technical assumptions made at the outset of each PFG design were inaccurate with respect to powder behavior and PFG function. As engineers documented these technical discoveries, appropriate modifications to the PFG were made to relatively progressively enhance its performance, these modifications included:
In due course of these design modifications, the powder syringe concept was developed and demonstrated by PFG4 and formalized in PFG5. This PFG variant showed that all-orientation operation of the PFG was feasible as a result of the dynamic reduction in powder bed volume that conserves gas and powder momentum as powder dissemination progresses. The powder syringe design also reduces the relatively large mass of fluidization gas that was necessary for complete powder dissemination in previous prototypes. In addition to solving these technical problems, PFG5 also maximized mass flow of powder disseminated from the canister, relatively significantly conserved the kinetic energy of the fluidizing gas, relatively significantly decreased powder dissemination time and facilitated the practical integration of a self-contained gas cartridge. Currently, PFG5 represents a powder syringe designed and fabricated to disseminate approximately 200 cc of Geldart Group C Powder with relatively high efficiency and relatively low propellant consumption.
While the present invention has been related in terms of the foregoing embodiments, those skilled in the art will recognize that the invention is not limited to the embodiments described. The present invention can be practiced with modification and alteration within the spirit and scope of the appended claims. Thus, the description is to be regarded as illustrative instead of restrictive on the present invention.
