CN114829068A - Method and design for high productivity quiet abrasive jet nozzle - Google Patents
Method and design for high productivity quiet abrasive jet nozzle Download PDFInfo
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- CN114829068A CN114829068A CN202080086029.XA CN202080086029A CN114829068A CN 114829068 A CN114829068 A CN 114829068A CN 202080086029 A CN202080086029 A CN 202080086029A CN 114829068 A CN114829068 A CN 114829068A
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24C—ABRASIVE OR RELATED BLASTING WITH PARTICULATE MATERIAL
- B24C5/00—Devices or accessories for generating abrasive blasts
- B24C5/02—Blast guns, e.g. for generating high velocity abrasive fluid jets for cutting materials
- B24C5/04—Nozzles therefor
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
- B05B1/00—Nozzles, spray heads or other outlets, with or without auxiliary devices such as valves, heating means
- B05B1/002—Nozzles, spray heads or other outlets, with or without auxiliary devices such as valves, heating means designed to reduce the generation or the transmission of noise or to produce a particular sound; associated with noise monitoring means
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
- B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
- B05B7/14—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas designed for spraying particulate materials
- B05B7/1404—Arrangements for supplying particulate material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
- B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
- B05B7/14—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas designed for spraying particulate materials
- B05B7/1481—Spray pistols or apparatus for discharging particulate material
- B05B7/1486—Spray pistols or apparatus for discharging particulate material for spraying particulate material in dry state
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Nozzles (AREA)
- Cleaning In General (AREA)
Abstract
Noise reducing abrasive jet assemblies and systems are described. The new assembly and system includes standard spray tubes, accelerator tubes, couplings and nozzles. The improved abrasive blasting system maintains the velocity of the abrasive particles while reducing the exit gas velocity and thus reducing the generation of sound. This is achieved by the accelerating portion having a reduced inner diameter and a sufficient length to provide the necessary abrasive particle velocity. The new system maintains the productivity and efficiency of conventional abrasive blasting systems, but greatly reduces noise generation and reduces operator fatigue due to the smaller weight of the load-bearing portion of the system.
Description
Statement regarding federally sponsored research or development
The invention is supported, in part, by the united states government ("government") under contract FA8222-14-M-0006 with the air force. The invention is also supported in part by the government under contract N68335-17-C-0581 with the naval research office. The government therefore has certain rights in this invention.
Technical Field
The present invention relates to an apparatus and a method for abrasive blasting. More specifically, noise reducing abrasive jet assemblies and systems and methods of constructing the same are described.
Background
Spray operations for removing paint and surface coatings are essential for ships, aircraft and land vehicles of the U.S. armed forces, and for industrial vehicles and machinery. These operations, however, expose maintenance personnel to Sound Pressure Levels (SPL) of 119dB and greater, which presents serious health, productivity, and compliance issues to the jetting operator. Many jetting operators suffer from hearing loss directly due to prolonged exposure to jetting noise. Personal Protective Equipment (PPE) such as earplugs and earmuffs may reduce direct risk, but may result in a loss of situational awareness and still not meet OSHA level requirements for noise exposure limits. The OSHA noise standard (29 CFR 1910.95) limits the worker's allowable noise exposure limit (PEL) to a time weighted average of 8 hours of 90dBA, and better hearing protection is not considered to reduce the worker's noise exposure. Only by reducing the sound at the source of the sound can the worker experience harmless noise.
Shown in fig. 1 is a conventional, prior art supersonic abrasive blasting system 10, the system 10 comprising a compressor 12, a compressor tube 14, and an abrasive tank 16, the abrasive tank 16 containing an abrasive medium 18. The abrasive metering valve 20 controls the rate at which abrasive media 18 is released into the standard jet pipe 22. Released medium 18 travels through ejector tube 22 to claw coupling 24, and then medium 18 passes through supersonic converging-diverging nozzle 26, where medium 18 is released into the environment at supersonic speeds and substantial noise at supersonic converging-diverging nozzle 26.
Details of a prior art converging-diverging nozzle 26 are shown in cross-section in fig. 2. The nozzle 26 includes a barrel 28, the barrel 28 having an orifice 30, the orifice 30 having a converging orifice portion 32, a throat 34, and a diverging orifice portion 36. The gas mixed with the abrasive media 18 is compressed as it travels through the converging portion 32 and then dispersed through the diverging portion 36, causing the particles of the media 18 to accelerate within the diverging portion 36 of the nozzle 26 and to flow out of the diverging portion 36.
Conventional abrasive blasting systems have been provided using a single 1 inch inner diameter blast tube 22 and a converging-diverging supersonic nozzle attachment 26. The abrasive blasting media in these arrangements undergoes a substantial portion of the acceleration of the abrasive blasting media over a short distance into the nozzle 26 and then away from the nozzle 26.
As demonstrated in Settles' paper (Settles G., A scientific view of the production of the rasive blasting nozzle, 1996), particles accelerate from a relatively small velocity in front of the nozzle to a higher velocity as they flow through the diverging portion and the outlet of the nozzle. This minimizes wear in the tube, especially for high abrasive media. This behavior is illustrated in the graph reproduced from the Settles paper in FIG. 3, which shows the predicted and measured velocities through the Laval nozzle. As shown, throughout the entire nozzle, the particle velocity is always well below 50% of the gas velocity.
Currently available abrasive blasting systems, such as the abrasive blasting systems shown in fig. 1 and 2, generate excessive noise that exceeds the levels set by occupational safety organizations for work environment noise, and therefore, require the use of personal protective equipment to protect hearing and limit the time an operator is exposed to such noise. Therefore, the following abrasive blasting systems are needed: the abrasive blasting system produces less noise, thereby reducing noise-induced hearing loss and/or tinnitus and improving situational awareness in noisy operating environments, while also exhibiting comparable productivity and efficiency.
Currently available abrasive blasting systems, such as the abrasive blasting systems shown in fig. 1 and 2, are large and heavy, causing stress and fatigue to the user. Accordingly, there is a need for smaller and lighter abrasive blasting systems for ease of use and for extended periods of use.
Disclosure of Invention
These and other objects are achieved in the noise reducing abrasive jet assemblies and systems of the present invention. The new assembly and system provide effective abrasive blasting with significantly less noise than the prior art while providing ergonomic stress reduction from the size and weight of the system load-bearing portion.
The new assembly and system provides a greater length in the tube, nozzle, or both the tube and nozzle over which the particles are accelerated before the outlet, thereby bringing the velocity of the particles closer to the velocity of the gas at the outlet, and enables the use of lower gas outlet velocities to reduce the noise of the system while maintaining or even increasing the particle velocity and thus the production rate. While the amount of jetting time allowed for the jetting operator is related to noise exposure (due to regulatory compliance issues, for example), nozzle productivity related to the velocity of abrasive exiting the nozzle is also a concern in abrasive jetting. Higher speeds mean that the jetting operator can spend less time jetting per square meter. Less time translates into higher worker productivity and lower operating costs.
In some embodiments, the new assembly and system includes a standard injection tube, a new accelerator tube portion, a coupling including a transition coupling, and a nozzle. The improved jetting system maintains the desired abrasive particle velocity while reducing the exit gas velocity and thus reducing sound generation. This is achieved by incorporating a straight accelerating portion, not present in prior art jetting systems, of sufficient length to provide the necessary abrasive particle velocity. The new system maintains the productivity and efficiency of conventional abrasive blasting systems, but greatly reduces noise generation and reduces operator fatigue due to the lower weight of the load-bearing portion of the system.
One aspect of the present invention is an abrasive blasting apparatus that generates significantly less noise than conventional supersonic abrasive blasting systems while exhibiting equal or greater efficiency and blasting results when compared to prior art supersonic abrasive blasting apparatuses.
An additional aspect of the present invention is an abrasive blasting apparatus having a smaller and lighter load-bearing portion than conventional supersonic abrasive blasting systems while exhibiting equal or greater efficiency and results.
Another aspect of the invention is an abrasive blasting system that employs a length of accelerator tube having a smaller inner diameter than conventional standard blasting tubes, with the accelerator tube employing additional length to accelerate media particles to a desired velocity before the particles enter the blasting nozzle.
A further aspect of the invention is the use of a transition piece to progressively reduce the inside diameter of the media path from the standard ejector tube to the accelerator tube.
Another aspect of the invention is an abrasive blasting system that employs a nozzle having a straight section after a diverging section to accelerate media particles to a desired velocity before the particles exit the blasting nozzle.
It is a further aspect of the invention that as energy is transferred to the particles, the air velocity leaving the straight section after the diffuser section decreases, thereby causing the nozzle to produce a lower sound.
In some embodiments, the new assemblies and systems include a tube and nozzle assembly having: a first portion having a first inner diameter; a constricted portion having an inner diameter smaller than the first inner diameter; a converging portion connecting the first portion to the converging portion and having a converging inner diameter; and a straight portion downstream of the converging portion, the straight portion having a constant inner diameter that is less than the inner diameter of the first portion. The straight portion has the following length: the length of the straight portion is such that when the blast nozzle assembly is operated at a predetermined gas/particle mixture and a predetermined pressure, the velocity of the gas exiting the blast nozzle assembly is reduced by at least 30% relative to a blast nozzle assembly without the straight portion. Any noise reduction that does not affect the productivity of the system or make the nozzle cumbersome or difficult to control is desirable. A reduction of only 7% in the exit gas velocity results in a 3dB reduction in noise, which is a significant improvement. In various embodiments, the length of the straight portion is effective to reduce the outlet gas velocity by 7% to 43%, in some embodiments 30% to 40%, and in some embodiments 35% when operating at a predetermined gas/particle mixture and a predetermined pressure. In operation, fluid flows through the first portion, the converging portion, and the straight portion in sequence.
In some embodiments, the converging portion, and the straight portion are all portions of a nozzle, which may also have a diverging portion connecting the converging portion with the straight portion. The converging portion, diverging portion and straight portion may together comprise a nozzle, and the converging portion may be the throat of the nozzle. The length of the straight portion may be at least 2/10 and less than 10 times the inner diameter of the straight portion. The straight portion has a constant inner diameter in some embodiments, and a slightly diverging profile or a slightly converging profile in other embodiments (the inner diameter varies by 5% or less over the length of the straight portion). In calculating the appropriate length for the straight section, a slightly diverging or converging profile may be considered to achieve the desired flow within the straight section (i.e., a Mach (Mach) number of 1 at or near the exit of the straight section). In some embodiments, the straight section has at least sections of alternating diameter, for example 1/8 inches, creating a bump that increases the surface friction on the inside of the section and affects the desired length (which may be incorporated into the friction calculation when determining the length of the straight section), but may slow the particle velocity somewhat. For a straight section with a variable inner diameter, reference herein to the diameter of the straight section may be seen as a reference to the average inner diameter of the straight section or to the inner diameter of the straight section at its outlet. The nozzle may be a number 6 nozzle. In other embodiments, the nozzle may be any diameter nozzle including, but not limited to, nozzle No. 4, nozzle No. 5, nozzle No. 7, nozzle No. 9, and nozzle No. 10.
In some embodiments, the inner diameter of the straight section is selected to produce a predetermined "hot spot" diameter of abrasive action.
In other embodiments, the inner diameter of the straight portion is selected to match the outlet of the diverging portion.
In some embodiments, the noise reducing abrasive jet nozzle assembly further comprises a media canister, abrasive media, and a compressed gas carrying the abrasive media, and the tube and nozzle assembly comprises one or more tube portions.
The present invention achieves sufficient abrasive particle velocity in an air stream having a lower exit velocity through a greater acceleration distance, thereby resulting in reduced nozzle generated noise experienced from a supersonic jet nozzle. The jetting productivity can be adjusted by adjusting the abrasive mass flow rate.
At least one embodiment of the present invention is a high productivity, quiet abrasive nozzle comprising: a converging portion having a converging inner diameter; a throat connected to the converging portion; a diffusion portion connected to the throat; and a straight portion connected to and immediately behind the diffusing portion. The straight portion has the following length: the length of the straight portion is such that, assuming that both injection nozzles are operated with the same predetermined mixture of gas and particles and a predetermined pressure, the velocity of the gas leaving the injection nozzles is reduced by at least 30% relative to the same injection nozzles with the straight portion removed. Further, in operation of a high productivity, quiet abrasive nozzle, fluid flows sequentially through a converging section, a throat section, a diverging section, and a straight section. In a preferred embodiment, the fluid flows directly from the converging portion to the throat to the diverging portion to the straight portion to the exterior of the nozzle (atmosphere/ambient) without any other intermediate portion.
In some embodiments, the inner diameter of the straight portion is less than the maximum inner diameter of the converging portion. In some embodiments, the straight portion has a constant inner diameter, and in other embodiments, the inner diameter of the straight portion may vary by up to 5% over the length of the straight portion.
In certain embodiments, the length of the straight portion is at least two tenths of the inner diameter of the straight portion. In other embodiments, the length of the straight portion is less than ten times the inner diameter of the straight portion. In further embodiments, the straight portion is between 1 inch and 10 inches in length. In yet another embodiment, the length of the straight portion is 2.5 inches.
In some embodiments, the nozzle is configured such that: for a predetermined mixture of gas and particles and a predetermined pressure, the supersonic flow of gas is isolated to the interior of the nozzle and the supersonic gas flow accelerates the abrasive particles in a straight section.
In some embodiments, the nozzle is further configured such that: the Mach number of the gas at the exit of the straight section is lower than the Mach number of the gas at the exit of the diffuser section for a predetermined mixture of gas and particles and a predetermined pressure, resulting in reduced operating noise.
In some embodiments, the nozzle is further configured such that: the gas mach number decreases from a gas mach number greater than 1 at the outlet of the diffuser section to a gas mach number of 1 at the outlet of the straight section for a predetermined gas and particle mixture and a predetermined pressure.
In at least one embodiment of the invention, the straight portion is configured to be attached to and detached from the diffuser portion. Some embodiments further comprise one or more additional straight portions configured to be attached to and detached from the diffuser portion. The straight portion and the one or more additional straight portions may each have a different length and/or a different inner diameter. In some embodiments, each of the one or more additional straight portions has a length of: the length of the one or more additional straight portions is such that when the spray nozzle is operated at a different predetermined mixture of gas and particles and a predetermined pressure, the velocity of the gas exiting the spray nozzle is reduced by at least 30% relative to the spray nozzle with the straight portions removed. In some embodiments, one or more of the straight portions may be configured to attach to each other such that the overall length of the straight portions may be quickly modified by attaching or removing such straight portions.
In some embodiments, the straight portion is cylindrical in shape.
In some embodiments, the nozzle is nozzle No. 4, nozzle No. 5, nozzle No. 6, nozzle No. 7, or nozzle No. 8. In some embodiments, the nozzle is made of a material selected from the group consisting of: tungsten carbide, silicon carbide, boron carbide, acrylic, ceramic, stainless steel, hardened steel, aluminum, or combinations thereof. In yet another embodiment, the nozzle further comprises at least one protective grip.
Some embodiments of the invention further comprise a fluid flowing through the diffuser section and having a mach number greater than 1 at an exit from the diffuser section to the straight section.
Some embodiments of the invention further comprise a fluid flowing through the straight section and having a mach number of 1 at an outlet of the straight section.
Some embodiments of the invention include a plurality of abrasive particles in a supersonic fluid flow inside a nozzle, the supersonic fluid flow being subjected to a positive shockwave in a straight portion.
In some embodiments, the length of the straight portion is such that: the spray nozzle has a noise level of 90dbA or less when operated at a predetermined mixture of gas and particles and a predetermined pressure. In further embodiments, the length of the straight portion is such that: when the spray nozzle is operated at a predetermined mixture of gas and particles and a predetermined pressure, the spray nozzle has a noise level reduced by 3dBA or more compared to a spray nozzle without a straight portion. In further embodiments, the length of the straight portion is such that: when the blast nozzle is operated at a predetermined mixture of gas and particles and a predetermined pressure, the blast nozzle has a noise level reduced by 6dBA or more compared to a blast nozzle without a straight portion.
In some embodiments, the length L of the straight portion is at least L * L of the compound * As given by the following equation:
wherein D is the diameter of the straight section, M is the Mach number of the fluid at the inlet of the straight section for a predetermined mixture of gas and abrasive particles,
is the average coefficient of friction of the straight part, f abrasives Is the coefficient of friction of the particles in the fluid stream, and gamma is the specific heat ratio of the fluid stream.
In some embodiments, the length L of the straight portion is at least L adjusted according to the ratio of the back pressure to the outlet pressure * Wherein L is * Given by the following equation:
wherein D is the diameter of the straight section, M is the Mach number of the fluid at the inlet of the straight section for a predetermined mixture of gas and abrasive particles,
is the average coefficient of friction of the straight part, f abrasives Is the coefficient of friction of the particles in the fluid stream, and gamma is the specific heat ratio of the fluid stream. In other words, L * Can be calculated according to the above equation, then L can be calculated according to L * The adjustment is made to take into account the fact that the ratio of the back pressure to the outlet pressure is not 1.
The present invention, in its various embodiments, also includes a method for making a high productivity quiet abrasive blasting nozzle, such as, for example, the high productivity quiet blasting nozzle described herein above, comprising: a converging portion having a converging inner diameter; a throat connected to the converging portion; a diffusion portion connected to the throat; and a straight portion connected to the diffusion portion, wherein the straight portion has a length of: the length of the straight portion is such that, assuming that both injection nozzles are operated with the same predetermined mixture of gas and particles and a predetermined pressure, the velocity of the gas leaving the injection nozzles is reduced by at least 30% relative to the same injection nozzles in the case where the straight portion is removed; and wherein, in operation of the nozzle, fluid flows sequentially through the converging portion, the throat portion, the diverging portion and the straight portion. Such a method comprises: determining a minimum length required for the straight section for a predetermined mixture of gas and abrasive particles and a predetermined pressure, the minimum length being a length that produces a mach number of 1 for the gas at or within a straight section inner diameter before exiting from the straight section; and, fabricating a nozzle having a straight portion with a length equal to or greater than the minimum length.
In some embodiments, the method further comprises: determining an optimum length of the straight section such that the gas mach number decreases from a peak at a first point, i.e. at the end of the diverging section, to a mach number of 1 at a length equal to or within the length equal to the inner diameter of the straight section before the exit of the straight section without entering subsonic velocity between the first and second points; and manufacturing a nozzle having a straight portion of an optimal length.
In some embodiments, the step of determining the optimal length comprises: analyzing the effect of friction from the walls of the straight section; and/or analyzing the effect of the plurality of abrasive particles on the reduction of the velocity of the airflow in the straight section.
In some embodiments, the method further comprises: adjusting the length of the straight portion in accordance with a particular operating condition to produce a desired combined sound reduction and productivity length determination; and manufacturing a nozzle having the length.
In some embodiments, the method further comprises: iterative computer simulations of the high productivity quiet abrasive jet nozzle described herein above over a series of straight segment lengths to find a length with the desired combination of sound reduction and productivity; and manufacturing a nozzle having the length.
The present invention additionally comprises, in its various embodiments, a nozzle attachment for high-productivity quiet abrasive blasting, the nozzle attachment comprising a straight tubular portion adapted to be connected to an outlet of a blasting nozzle. The straight tubular portion has the following length: the straight tubular portion has a length such that, when the abrasive jet nozzle is operated at a predetermined mixture of gas and particles and a predetermined pressure, the velocity of the gas leaving the abrasive jet nozzle with the straight tubular portion attached is reduced by at least 30% relative to an abrasive jet nozzle without a connecting straight tubular portion. In a preferred embodiment, the straight tubular portion has a constant inner diameter along its entire length. In some embodiments, the inner diameter of the straight tubular portion may vary over its length by up to 5%. In a preferred embodiment, the inner diameter of the straight tubular portion (particularly at the inlet) is arranged to match the inner diameter at the outlet of a given abrasive jet nozzle or set of abrasive jet nozzles with which the straight tubular portion is to be used. In a preferred embodiment, the straight tubular portion is free of diverging or converging portions or appendages, and when the nozzle attachment is mounted on an abrasive blasting nozzle, the fluid flow passes directly from the diverging portion of the nozzle into the straight tubular portion nozzle attachment and from the straight tubular portion directly into the atmosphere/environment (e.g., toward a target surface for abrasive blasting). Similarly, for embodiments embedding a straight section into the end of the abrasive jet nozzle, such as the embodiments described above, the fluid may flow directly from the diverging section into the straight section and from the straight section into the atmosphere/environment without any intermediate sections.
In at least one aspect of the nozzle attachment, the abrasive jet nozzle is a No. 4 nozzle, a No. 5 nozzle, a No. 6 nozzle, a No. 7 nozzle, or a No. 8 nozzle. The numerical grading of the nozzles (No. 6, No. 8, etc.) is a well-known graded measurement based on orifice size (inner diameter at the outlet).
In some embodiments, the nozzle attachment further comprises a fixture for connecting the straight tubular portion to the abrasive jet nozzle.
In some embodiments, the nozzle attachment further comprises a fixture embedded in the straight tubular portion to assist in connecting the straight tubular portion to the abrasive jet nozzle.
In a further aspect of the nozzle attachment, the inner diameter of the straight tubular portion is less than the maximum inner diameter of the converging portion of the abrasive jet nozzle.
In other aspects of the nozzle attachment, the straight tubular portion is configured such that: for a predetermined mixture of gas and particles and a predetermined pressure, when the straight tubular portion is connected to the abrasive blasting nozzle, the supersonic flow of gas does not continue beyond the outlet of the straight tubular portion, and the supersonic flow of gas accelerates the abrasive particles in the straight tubular portion.
In other aspects of the nozzle attachment, the straight tubular portion is configured such that: when the straight tubular portion is connected to the abrasive blasting nozzle, the gas mach number is lower at the outlet of the straight tubular portion than at the outlet of the diffuser portion of the blasting nozzle for a predetermined mixture of gas and particles and pressure, so that the operating noise is reduced.
In a further aspect of the nozzle attachment, the straight tubular portion is configured such that: when the straight tubular portion is connected to the blasting nozzle, the gas mach number decreases from a gas mach number greater than 1 at the outlet of the diffusing portion of the blasting nozzle to a gas mach number of 1 at the outlet of the straight portion, for a predetermined mixture of gas and particles and a predetermined pressure.
In other aspects of the nozzle attachment, the length of the straight tubular portion is at least two tenths of the diameter of the straight tubular portion. In some embodiments, the length of the straight tubular portion is less than 10 times the diameter of the straight tubular portion. In further embodiments, the straight tubular portion is between 1 inch and 10 inches in length. In other embodiments, the length of the straight tubular portion is 2.5 inches.
In other aspects of the nozzle attachment, the straight tubular portion is cylindrical in shape. In some embodiments, the straight tubular portion is made of a material selected from the group consisting of: tungsten carbide, silicon carbide, boron carbide, acrylic, ceramic, stainless steel, hardened steel, aluminum, or combinations thereof.
In a further aspect of the nozzle attachment, the length of the straight tubular portion is such that: when the straight tubular portion is connected to the abrasive blasting nozzle, the blasting nozzle has a noise level of 90dBA or less when operated with a predetermined mixture of gas and particles and a predetermined pressure. In a further aspect of the nozzle embodiment, the length of the straight tubular portion is such that: when a straight tubular portion is connected to the abrasive blasting nozzle, the noise level of the blasting nozzle is reduced by 3dBA or more when the blasting nozzle is operated at a predetermined mixture of gas and particles and a predetermined pressure, compared to a blasting nozzle without a straight tubular portion. In a further aspect of the nozzle embodiment, the length of the straight tubular portion is such that: when a straight tubular portion is connected to the abrasive blasting nozzle, the noise level of the blasting nozzle is reduced by 6dBA or more when the blasting nozzle is operated at a predetermined mixture of gas and particles and a predetermined pressure, compared to a blasting nozzle without a straight tubular portion
Other aspects of the nozzle attachment have a length L of the straight tubular portion, where L is at least L * ，L * As given by the following equation:
wherein, in the case where the straight tubular portion is connected to the blasting nozzle, D is a diameter of the straight tubular portion, M is a Mach number of the fluid at an inlet of the straight portion, for a predetermined mixture of the gas and the abrasive particles,
is the average coefficient of friction of the straight part, f abrasives Is the coefficient of friction of the particles in the fluid stream, and gamma is the specific heat ratio of the fluid stream.
Some aspects of the nozzle attachment have a length L of the straight tubular portion, where L is at least L adjusted according to a ratio of back pressure to outlet pressure * Wherein, L * Given by the following equation:
wherein D is the diameter of the straight tubular portion, M is the Mach number of the fluid at the inlet of the straight portion, for a predetermined mixture of gas and abrasive particles when the straight tubular portion is connected to the blasting nozzle,
is the average coefficient of friction of the straight part, f abrasives Is the coefficient of friction of the particles in the fluid stream, and gamma is the specific heat ratio of the fluid stream.
The present invention, in its various embodiments, also includes a method for manufacturing the nozzle attachment described herein above to reduce the noise of a connected abrasive blasting nozzle without reducing the nozzle productivity. The method comprises the following steps: determining a minimum length required for the nozzle attachment described herein above for a predetermined mixture of gas and abrasive particles and a predetermined pressure, the minimum length resulting in a mach number of 1 at or within a straight tubular portion inner diameter of the gas prior to the exit of the straight portion; and manufacturing a straight tubular portion having a length equal to or greater than the minimum length.
In some embodiments, the method for manufacturing a nozzle attachment as described herein above further comprises: determining an optimum length of the straight tubular portion of the nozzle attachment described herein above such that the gas mach number decreases from a peak at a first point, i.e. at the end of the diffuser portion of the connected blasting nozzle, to a mach number of 1 at a length equal to or within the inner diameter of the straight tubular portion without entering subsonic velocity between the first and second points before the exit of the straight tubular portion; and manufacturing a straight tubular part having an optimal length.
In some embodiments, the step of determining the optimal length comprises: analyzing the effect of friction from the wall of the straight tubular section; and/or analyzing the effect of the plurality of abrasive particles on the reduction of the air flow velocity in the straight tubular section.
In some embodiments, the method for manufacturing a nozzle attachment as described herein above further comprises: adjusting the length of the straight tubular portion in accordance with a particular operating condition to determine the length of the combination of sound reduction and productivity required to produce the desired sound; and manufacturing a straight tubular portion having the length.
In some embodiments, the method for manufacturing a nozzle attachment as described herein above further comprises: performing repeated computer simulations of the straight tubular portion of the nozzle attachment described herein above over a range of straight tubular portion lengths to find a length having a desired combination of sound reduction and productivity; and manufacturing a straight tubular portion having the length.
In general, any known abrasive blasting nozzle may be adapted as a nozzle according to embodiments of the invention. For example, the existing nozzle No. 2, nozzle No. 3, nozzle No. 4, nozzle No. 5, nozzle No. 6, nozzle No. 7, nozzle No. 8, nozzle No. 9, nozzle No. 10, nozzle No. 11, or nozzle No. 12 may be adjusted to have a straight portion at the end of the diffuser portion of the nozzle, as described herein, to achieve an embodiment of the present invention. Similarly, a nozzle attachment according to embodiments of the present invention may be adapted to attach to any known abrasive blasting nozzle. The assembly as a whole (i.e., the existing nozzle in combination with the attached nozzle attachment) can be considered a high productivity, quiet abrasive blasting nozzle when the nozzle attachment is mounted on an existing nozzle. Furthermore, abrasive blasting nozzles and nozzle attachments according to embodiments of the invention may be suitable for use in a variety of applications and in a variety of operating conditions including pressure, particulate loading, types of abrasive particles and fluids, nozzle materials, and the like. In particular, any given nozzle or nozzle attachment according to embodiments of the present invention may be adapted to: a certain result or range of results is achieved for a predetermined mixture of gas and particles and a predetermined pressure or for a predetermined range of mixtures of gas and particles and a predetermined pressure. The nozzle or nozzle attachment according to embodiments of the invention may for example be adapted to: for a predetermined mixture of gas and particles and a predetermined pressure, including a nozzle pressure between 20psi and 200psi and a particle load of abrasive wear rate of 50 to 10,000 pounds per hour or any range of pressures and particle loads within these ranges, at least a 3dB reduction in noise is achieved relative to prior art abrasive jet nozzles. For example, such conditions are suitable for nozzle No. 2, nozzle No. 3, nozzle No. 4, nozzle No. 5, nozzle No. 6, nozzle No. 7, nozzle No. 8, nozzle No. 9, nozzle No. 10, nozzle No. 11, and nozzle No. 12. The particle loading may be determined in part by what type of roughness profile the shooter wants to have and the jetting pressure used. The predetermined mixture of gas and particles may be, for example, compressed air and sand and/or any other abrasive particles. The phrase "predetermined mixture of gas and particles and predetermined pressure" may include gas type, particle type, nozzle pressure, back pressure, and particle loading. The back pressure is usually atmospheric pressure, and may be assumed to be atmospheric pressure if not specifically mentioned. For example, compressed air with sand particles, a nozzle pressure of 100psi, and a particle load of 1,000 pounds per hour are an exemplary predetermined mixture of gas and particles and a predetermined pressure.
Additional embodiments of the present invention include a high productivity quiet abrasive jet nozzle assembly including a productivity quiet abrasive jet nozzle as described herein above.
The principles described herein may be applied to applications other than abrasive blasting where the sound level of fluid flow is problematic, even in applications where nozzles are not used. In particular, in applications where supersonic fluid flow results in high noise levels, flowing the fluid through a straight tubular portion prior to entering the atmosphere/environment may reduce the fluid velocity. The noise level is particularly reduced where the straight tubular portion is sized to induce a shockwave upon or immediately prior to discharge of the fluid into the environment. The straight tubular portion reduces velocity and noise level even in non-supersonic flows. The use of a straight tubular section is particularly useful in applications where the fluid is used to accelerate particles or other objects within the fluid stream that are at a lower velocity than the fluid, because the straight section can reduce the fluid velocity while increasing the entrained object velocity, thereby reducing the noise level without sacrificing productivity.
Thus, based on the foregoing and the continued description, the invention may, in its various embodiments, comprise one or more of the following features, in any non-mutually exclusive combination:
a high productivity, quiet abrasive blasting nozzle having a converging portion with a converging inner diameter;
a high productivity, quiet abrasive blasting nozzle having a throat connected to a converging portion;
a high productivity, quiet blasting nozzle having a diverging portion connected to a throat;
a high productivity, quiet abrasive blasting nozzle having a straight section connected to and immediately behind a diverging section;
a high productivity, quiet abrasive blasting nozzle having a straight section with the following length: the length of the straight portion is such that when the spray nozzle is operated at a predetermined mixture of gas and particles and a predetermined pressure, the velocity of the gas exiting the spray nozzle is reduced by at least 30% relative to the blast nozzle in the case where the straight portion is removed;
a high productivity, quiet abrasive jet nozzle in which, in operation, fluid flows sequentially through a converging section, a throat section, a diverging section and a straight section;
a high productivity, quiet abrasive jet nozzle in which the diameter of the straight section is less than the maximum internal diameter of the diverging section;
a high productivity, quiet abrasive blasting nozzle, wherein the nozzle is configured such that: for a predetermined mixture of gas and particles and a predetermined pressure, the supersonic flow of gas is isolated to the interior of the nozzle and the supersonic gas flow accelerates the abrasive particles in the straight portion;
a high productivity, quiet abrasive blasting nozzle, wherein the nozzle is configured such that: the Mach number of the gas at the outlet of the straight section is lower than that at the outlet of the diffuser section for a predetermined mixture of gas and particles and a predetermined pressure, thereby reducing the operating noise;
a high productivity, quiet abrasive blasting nozzle, wherein the nozzle is configured such that: for a predetermined mixture of gas and particles and a predetermined pressure, the gas mach number decreases from a gas mach number greater than 1 at the diffuser section exit to a gas mach number of 1 at the straight section exit;
a high productivity, quiet abrasive jet nozzle in which the length of the straight section is at least two tenths of the internal diameter of the straight section;
a high productivity, quiet abrasive blasting nozzle in which the length of the straight section is less than ten times the internal diameter of the straight section;
a high productivity, quiet abrasive jet nozzle, wherein the length of the straight section is between 1 and 10 inches;
a high productivity, quiet abrasive jet nozzle in which the length of the straight section is 2.5 inches;
a high productivity, quiet abrasive blasting nozzle, wherein the straight section is configured to be attached to and detached from the diverging section;
a high productivity, quiet abrasive blasting nozzle, further comprising one or more additional straight sections configured to be attached to and detached from the diverging section, wherein the straight section and the one or more additional straight sections have different lengths and/or different inner diameters;
a high productivity quiet abrasive jet nozzle, wherein each of the one or more additional straight sections has a length of: the length of the one or more additional straight portions is such that when the spray nozzle is operated at a predetermined mixture of gas and particles and pressure, the velocity of the gas exiting the spray nozzle is reduced by at least 30% relative to the spray nozzle if the straight portions were removed;
a high productivity, quiet abrasive blasting nozzle in which the straight portion is cylindrical in shape;
a high productivity, quiet abrasive blasting nozzle, wherein the nozzle is nozzle No. 4, nozzle No. 5, nozzle No. 6, nozzle No. 7, or nozzle No. 8;
a high productivity, quiet abrasive blasting nozzle, wherein the nozzle is made of a material selected from: tungsten carbide, silicon carbide, boron carbide, acrylic, ceramic, stainless steel, hardened steel, aluminum, or combinations thereof;
a high productivity, quiet abrasive blasting nozzle, wherein the nozzle further comprises at least one protective grip;
a high productivity, quiet abrasive jet nozzle, further comprising a fluid flowing through the diffuser section and having a mach number greater than 1 at the exit from the diffuser section to the straight section;
a high productivity, quiet abrasive jet nozzle, further comprising a fluid flowing through the diffuser section and having a mach number of 1 at the exit of the straight section;
a high productivity, quiet abrasive blasting nozzle, further comprising a plurality of abrasive particles in a supersonic fluid stream inside the nozzle, the supersonic fluid stream being subjected to a positive shockwave in a straight section;
a high productivity, quiet abrasive blasting nozzle, wherein the length of the straight section is such that: the spray nozzle has a noise level of 90dBA or less when operated at a predetermined mixture of gas and particles and a predetermined pressure;
a high productivity, quiet abrasive blasting nozzle, wherein the length of the straight section is such that: when the spray nozzle is operated at a predetermined mixture of gas and particles and a predetermined pressure, the spray nozzle has a noise level that is reduced by 3dBA or more compared to a spray nozzle without a straight portion;
a high productivity, quiet abrasive blasting nozzle, wherein the length of the straight section is such that: when the blast nozzle is operated at a predetermined mixture of gas and particles and pressure, the blast nozzle has a noise level reduced by 6dBA or more compared to a blast nozzle without a straight portion;
a high productivity quiet abrasive blasting nozzle, wherein the length L of the straight section is at least L * ，L * As given by the following equation:
wherein D is the diameter of the straight section, M is the Mach number of the fluid at the inlet of the straight section for a predetermined mixture of gas and abrasive particles,
is the average coefficient of friction of the straight part, f abrasives Is the coefficient of friction of the particles in the fluid stream, and γ is the specific heat ratio of the fluid stream;
a high productivity quiet abrasive blasting nozzle, wherein the length L of the straight portion is at least L adjusted according to the ratio of the back pressure to the outlet pressure * Wherein L is * Given by the following equation:
wherein for a predetermined mixing of gas and abrasive particlesD is the diameter of the straight section, M is the mach number of the fluid at the entrance of the straight section,
is the average coefficient of friction of the straight part, f abrasives Is the coefficient of friction of the particles in the fluid stream, and γ is the specific heat ratio of the fluid stream;
a method for manufacturing the high productivity quiet abrasive jet nozzle described herein above to reduce nozzle noise without reducing nozzle efficiency. The method comprises the following steps: determining a minimum length of the straight section of the high productivity quiet abrasive jet nozzle described herein above for a predetermined mixture of gas and abrasive particles and a predetermined pressure, the minimum length being that length required for the gas to produce a mach number of 1 at or within a straight section inner diameter prior to the exit of the straight section; and, fabricating a nozzle having a straight portion with a length equal to or greater than a minimum length;
a method for making the high productivity quiet abrasive jet nozzle described herein above, the method further comprising: determining an optimum length of the straight section of the high productivity quiet abrasive jet nozzle described herein above such that the gas mach number decreases from a peak at a first point, i.e. at the end of the diverging section, to a mach number of 1 at a second point at or within a length equal to the inner diameter of the straight section before the exit of the straight section without entering subsonic velocity between the first and second points; and manufacturing a nozzle having a straight portion of an optimal length;
a method for making the high productivity quiet abrasive jet nozzle described herein above, wherein the step of determining the optimal length comprises: analyzing the effect of friction from the walls of the straight section; and/or analyzing the effect of the plurality of abrasive particles on the reduction of the air flow velocity in the straight section;
a method for making the high productivity quiet abrasive jet nozzle described herein above, the method further comprising: adjusting the length of the straight portion in accordance with the particular operating condition to determine the length of the straight portion that produces the desired combination of sound reduction and productivity; and fabricating a nozzle having the length;
a method for making the high productivity quiet abrasive jet nozzle described herein above, the method further comprising: iterative computer simulations of the high productivity quiet abrasive jet nozzle described herein above over a series of straight segment lengths to find a length with the desired combination of sound reduction and productivity; and fabricating a nozzle having the length;
a nozzle attachment for high-productivity quiet abrasive blasting, the nozzle comprising a straight tubular portion for connection to an outlet of a blasting nozzle, wherein the length of the straight tubular portion is such that: when the spray nozzle is operated at a predetermined mixture of gas and particles and a predetermined pressure, the velocity of the gas exiting the spray nozzle is reduced by at least 30%;
a nozzle attachment for high productivity quiet abrasive blasting, wherein the abrasive blasting nozzle is nozzle No. 4, nozzle No. 5, nozzle No. 6, nozzle No. 7 or nozzle No. 8;
a nozzle attachment for high-productivity quiet abrasive blasting, the nozzle further comprising fixing means for connecting the straight tubular portion to the abrasive blasting nozzle;
a nozzle attachment for high-productivity quiet abrasive blasting, the nozzle further comprising a fixing means embedded in the straight tubular portion to assist in connecting the straight tubular portion to the abrasive blasting nozzle;
a nozzle attachment for high-productivity quiet abrasive blasting, wherein the inner diameter of the straight tubular portion is smaller than the maximum inner diameter of the convergent portion of the abrasive blasting nozzle;
a nozzle attachment for high-productivity quiet abrasive blasting, wherein the straight tubular portion is configured such that: for a predetermined mixture of gas and particles and a predetermined pressure, when the straight tubular portion is connected to the abrasive blasting nozzle, the supersonic flow of gas does not exceed the outlet of the straight tubular portion and the supersonic flow of gas accelerates the abrasive particles in the straight tubular portion;
a nozzle attachment for high-productivity quiet abrasive blasting, wherein the straight tubular portion is configured such that: when the straight tubular portion is connected to the blasting nozzle, the mach number of the gas at the outlet of the straight tubular portion is lower than that at the outlet of the diffusing portion of the blasting nozzle for a predetermined mixture of gas and particles and a predetermined pressure, so that the operating noise is reduced;
a nozzle attachment for high-productivity quiet abrasive blasting, wherein the straight tubular portion is configured such that: when the straight tubular portion is connected to the blasting nozzle, the gas mach number decreases from a gas mach number greater than 1 at the outlet of the diffusing portion of the blasting nozzle to a gas mach number of 1 at the outlet of the straight portion, for a predetermined mixture of gas and particles and a predetermined pressure;
a nozzle attachment for high productivity quiet abrasive blasting, wherein the length of the straight tubular portion is at least two tenths of the diameter of the straight tubular portion;
a nozzle attachment for high productivity quiet abrasive blasting, wherein the length of the straight tubular portion is less than ten times the diameter of the straight tubular portion;
a nozzle attachment for high productivity quiet abrasive blasting, wherein the length of the straight tubular section is between 1 and 10 inches;
a nozzle attachment for high productivity quiet abrasive blasting, wherein the length of the straight tubular section is 2.5 inches;
a nozzle attachment for high-productivity quiet abrasive blasting, wherein the straight tubular portion is cylindrical in shape;
a nozzle attachment for high-productivity quiet abrasive blasting, wherein the straight tubular portion is made of a material selected from: tungsten carbide, silicon carbide, boron carbide, acrylic, ceramic, stainless steel, hardened steel, aluminum, or combinations thereof;
a nozzle attachment for high-productivity quiet abrasive blasting, wherein the length of the straight tubular portion is such that: when the straight tubular portion is connected to the abrasive blasting nozzle, the blasting nozzle has a noise level of 90dBA or less operating at a predetermined mixture of gas and particles and a predetermined pressure;
a nozzle attachment for a high productivity quiet abrasive blasting, wherein the length of the straight tubular section is such that: when the straight tubular portion is connected to the abrasive blasting nozzle, the blasting nozzle has a noise level reduced by 3dBA or more when the blasting nozzle is operated with a predetermined mixture of gas and particles and a predetermined pressure, compared to the blasting nozzle without the straight tubular portion;
a nozzle attachment for high-productivity quiet abrasive blasting, wherein the length of the straight tubular portion is such that: when the straight tubular portion is connected to the blasting nozzle, the blasting nozzle has a noise level reduced by 6dBA or more when operated with a predetermined mixture of gas and particles and pressure compared to the blasting nozzle without the straight tubular portion;
a nozzle attachment that achieves a predetermined noise level reduction for nozzle pressures between 20psi and 200psi and particle loads of abrasive wear rates of 50 to 10,000 pounds per hour or any value or range of values within these ranges.
A nozzle attachment for high productivity quiet abrasive blasting, wherein the length L of the straight tubular section is at least L * ，L * As given by the following equation:
wherein D is a straight tube for a predetermined mixture of gas and abrasive particles with the straight tube part connected to the abrasive-blasting nozzleThe diameter of the shape, M being the Mach number of the flow at the inlet of the straight section,
is the average coefficient of friction of the straight part, f abrasives Is the coefficient of friction of the particles in the fluid stream, and γ is the specific heat ratio of the fluid stream;
a nozzle attachment for high productivity quiet abrasive blasting, wherein L is at least L adjusted according to the ratio of back pressure to outlet pressure * Wherein L is * Given by the following equation:
wherein, in the case where the straight tubular portion is connected to the abrasive-blasting nozzle, D is a diameter of the straight tubular portion, M is a Mach number of the fluid at an inlet of the straight portion, for a predetermined mixture of the gas and the abrasive particles,
is the average coefficient of friction of the straight part, f abrasives Is the coefficient of friction of the particles in the fluid stream, and γ is the specific heat ratio of the fluid stream;
a plurality of nozzle attachments configured to be connected to each other to combine the lengths of the plurality of nozzle attachments;
a method for manufacturing a nozzle attachment as described herein above to reduce noise of a connected abrasive blasting nozzle without reducing nozzle productivity, the method comprising: determining a minimum length of the straight tubular portion of the nozzle attachment described herein above for a predetermined mixture of gas and abrasive particles and a predetermined pressure, the minimum length being that length required to produce a mach number of 1 at or within a straight tubular portion inner diameter of the gas prior to the exit of the straight portion; and, manufacturing a straight tubular portion having a length equal to or greater than a minimum length;
a method for manufacturing a nozzle attachment as described herein above to reduce noise of a connected abrasive blasting nozzle without reducing nozzle productivity, the method further comprising: determining an optimum length of the straight tubular portion of the nozzle attachment described herein above such that the gas mach number decreases from a peak at a first point, i.e. at the end of the diverging portion of the connected blasting nozzle, to a mach number of 1 at a length equal to or within the inner diameter of the straight tubular portion without entering subsonic velocity between the first and second points before the exit of the straight tubular portion; and manufacturing a straight tubular part having an optimal length;
a method for manufacturing a nozzle attachment as described herein above to reduce noise of a connected abrasive blasting nozzle without reducing nozzle productivity, wherein the step of determining the optimum length comprises: analyzing the effect of friction from the wall of the straight tubular section; and/or analyzing the effect of the plurality of abrasive particles on the reduction of the air flow velocity in the straight tubular section;
a method for manufacturing a nozzle attachment as described herein above to reduce noise of a connected abrasive blasting nozzle without reducing nozzle productivity, the method further comprising: adjusting the length of the straight tubular portion according to specific operating conditions to determine the length of the straight portion of the desired combination of sound reduction and productivity; and manufacturing a straight tubular portion having the length;
a method for manufacturing a nozzle attachment as described herein above to reduce noise of a connected abrasive blasting nozzle without reducing nozzle productivity, the method further comprising: performing iterative computer simulations of the straight tubular portion of the nozzle attachment described herein above over a series of straight tubular portion lengths to find a length having a desired combination of sound reduction and productivity; and manufacturing a straight tubular portion having the length; and
a high productivity quiet abrasive jet nozzle assembly comprising the high productivity quiet abrasive jet nozzle described herein above;
a nozzle or nozzle attachment having a terminal straight portion with an internal diameter that varies by 5% or less over the length of the straight portion.
Drawings
FIG. 1 illustrates a conventional prior art supersonic abrasive blasting system.
FIG. 2 illustrates, in cross-section, a conventional prior art supersonic converging-diverging nozzle used in the abrasive blasting system shown in FIG. 1.
FIG. 3 is a graph reproduced from Settles' paper (Settles G., A scientific view of the production of abrasive blasting nozzles, 1996) showing predicted and measured velocities through a conventional Laval nozzle and the large difference between abrasive velocity and outlet air velocity.
FIG. 4 is a graph showing the drag coefficient of a sphere as a function of Mach number at two Reynolds numbers.
FIG. 5 is a graph illustrating the required jet exit velocity reduction to achieve a desired Sound Pressure Level (SPL) reduction based on the jet exit velocity versus generated jet noise;
FIG. 6 is a graph showing simulated particle velocity versus distance for 20/30 mesh V-type acrylic media in the 345m/s accelerator section.
Fig. 7 is a Moody Diagram (Moody Diagram) for estimating a friction coefficient from a reynolds number and a pipe roughness.
FIG. 8 illustrates an improved noise reducing abrasive blasting system according to an embodiment of the present invention.
FIG. 9 shows, in cross-section, details of a transition coupling for progressively reducing the inner diameter of the abrasive media path employed in the noise reducing abrasive blasting system shown in FIG. 8.
FIG. 10 is a photograph of a prototype noise reducing abrasive jet accelerator tube and nozzle according to an embodiment of the invention.
Fig. 11 is a photograph showing in comparative form the productivity of a noise reducing abrasive spray nozzle according to an embodiment of the present invention (left side) and a conventional spray using nozzle No. 8 (right side) both using a 4-turn abrasive metering valve knob by spraying V-type media on a half-exposed coated bakeware for 30 seconds.
FIG. 12 is a photograph comparing the results of using a noise reducing abrasive blasting system according to an embodiment of the invention operating with additional abrasive to the results of a conventional system operating with a standard No. 8 nozzle.
FIG. 13 is a self-spectrum of a prior art supersonic abrasive jet apparatus with a standard No. 8 nozzle using V-media and 40psi operating pressure with a prototype of the invention and background noise level from the jet compressor unit.
Fig. 14A to 14B are a side view and a perspective view, respectively, of a standard No. 6 nozzle.
FIG. 15 is a cross-sectional view of nozzle XL 6.
Fig. 16A to 16B are a side perspective view (fig. 16A) and a sectional view (fig. 16B) of a modified spray nozzle according to an embodiment of the present invention.
Fig. 17A to 17B are a side perspective view (fig. 17A) and a sectional view (fig. 17B) of a modified spray nozzle extended in length according to an embodiment of the present invention.
FIG. 18 is a schematic diagram illustrating convergent-divergent nozzle expansion.
Fig. 19A-19B are CFD results showing mach number distributions at 67psig nozzle pressure using ANSYS Fluent for a standard No. 6 nozzle (fig. 19A) and a modified nozzle according to an embodiment of the present invention (fig. 19B).
Fig. 20A-20B are CFD results showing mach number distributions at 100psig nozzle pressure using ANSYS Fluent for a standard No. 6 nozzle (fig. 20A) and a modified nozzle according to an embodiment of the present invention (fig. 20B).
Fig. 21A-21B are CFD results showing mach number distributions at 67psig nozzle pressure using ANSYS Fluent with increased wall drag for a standard 6 nozzle (fig. 21A) and a modified nozzle according to an embodiment of the invention (fig. 21B).
FIG. 22 is a graph showing the average 1/3 octave acoustic spectrum for various nozzles.
FIG. 23 is a cross-sectional view of a standard converging-diverging abrasive jet nozzle.
Fig. 24 shows a cross-section of an abrasive jet nozzle according to an embodiment of the invention.
Fig. 25 shows a cross-section of an abrasive jet nozzle according to an embodiment of the invention, wherein abrasive particles are in a flow.
FIG. 26 shows a cross-section of an abrasive jet nozzle according to an embodiment of the invention, wherein the length is equal to L * Or length ratio L * Is slightly longer.
Fig. 27 shows the effect of increasing or decreasing the nozzle pressure on the outlet condition of the straight part of the nozzle.
Detailed Description
As set forth below, a solution to the problem of excessive noise from prior art superabrasive blasting systems was discovered.
The acceleration of the particles in the flow can be simulated using the resistance coefficient determined empirically based on data from Bailey and Hialt as proposed previously (Settles & Geppert, 1997). The acceleration of the particles of mass m can be determined from the resistance D as
Wherein A is the cross-sectional area of the sphere, and U rel Is the relative velocity between the gas and the particles. Shown in fig. 4 is the drag coefficient of a sphere as a function of mach Number for two Reynolds numbers.
Previous studies have demonstrated that the noise power P of a jet is proportional to the eighth power of the velocity and the square of the jet diameter (Powell, 1959):
P∝U 8 D 2
furthermore, the sound pressure level SPL is proportional to the sound power level SWL, wherein
Thus, it can be concluded that SPL, velocity and diameter are proportional:
this relationship is illustrated in the form of a graph in fig. 5. Thus, if the exit velocity of the nozzle is reduced by, for example, 30%, the SPL is expected to drop by 12.5dB, while a 43% reduction in exit velocity would result in an expected 20dB drop in SPL.
In order to have the same throughput as the prior art nozzle abrasive blasting systems, the velocity of the particles must be maintained. Conventional nozzles as shown in fig. 2 have gas velocities that are much higher than the particle velocities, and these high gas velocities are responsible for the higher sound levels. The present invention maintains particle velocity while reducing nozzle outlet gas velocity and thus reducing sound generation. This requires a longer acceleration length relative to prior art nozzle abrasive blasting systems.
The mass of the sphere is the density of the particle ρ particle Multiplied by volume
The acceleration becomes:
the solution can be found in a stepwise manner and is shown in fig. 6 for 20/30 mesh V-type acrylic media in a gas stream with a velocity of 345 m/s. This indicates that an accelerator section of 4 meters is required in the tube to achieve a particle velocity of 275 m/s.
Based on the predicted outlet velocity 483m/s from the previous model of a standard No. 8 nozzle operating at 40psi pressure, the outlet velocity decreased by 30% to 345m/s (roughly sonic), with an outlet velocity of 345m/s decreasing the SPL by 12.5 dB. Therefore, the length of the tube needs to be long enough to match the particle velocity at 40psi for the size 8 nozzle.
The current invention achieves sufficient abrasive particle velocity in an air stream having a lower exit velocity through a greater acceleration distance, thereby using ultrasonic spray nozzles to reduce the noise perception produced by the nozzles. The jetting productivity can be adjusted by adjusting the abrasive mass flow rate.
Pressure loss or head loss is unavoidable and must be taken into account. As the length of the tube increases, the pressure will drop and eventually the flow rate will decrease. But such losses can be calculated. The head loss or pressure loss due to friction along the pipe is given by the Darcy-Weisbach equation:
where L is the length of the pipe section, D is the pipe diameter, ρ is the density of the fluid, V is the average fluid velocity, and f D Is based on the reynolds number Re and Darcy (Darcy) coefficient of friction relative to the pipe roughness e/d and is equal to about 0.02 for plastic/rubber. Fig. 7 shows a Moody Diagram (Moody Diagram) for estimating the friction coefficient from the reynolds number and the pipe roughness.
An injection tube having an inner diameter of 3/4 inches operating near "choke" conditions has a velocity of 230 to 340m/s and a Reynolds number of 300,000 to 436,000. The resistance over the length of the tube causes a pressure loss, which reduces the average velocity in the pipe.
If a choke flow condition exists where the downstream pressure drops below a critical value, the velocity in the tube will be sonic,
wherein the heat capacity ratio K is 1.4 for air, i.e.
p * ＝0.528p 0
For a gauge pressure of 40psi or an absolute pressure of 54.7, p is 28.9psia or 14.2 psig.
Based on the results of the analytical model discussed above, a preferred embodiment of the present invention is designed to: the airborne particulates are withdrawn from the exemplary 1 inch tube and accelerated through the smaller diameter tube a sufficient distance so that a high production rate of particulate velocity is achieved. Transition couplings that step down the inner diameter of the pipe provide a smooth transition between different pipe section diameters and minimize pressure losses.
According to a preferred embodiment of the noise reducing abrasive injection system of the present invention shown in FIG. 8, the compressor 112 pressurizes the gas to approximately 120 psi. The compressed gas is pumped through a starting pipe section 114 into an abrasive media tank 116 that contains abrasive media 118. The abrasive metering valve 120 controls the rate of release of the abrasive media 118. A standard 1 inch inner diameter jet tube 124 is attached at one end to metering valve 120 and at the other end to transition link 122. A length of reduced inner diameter accelerator tube 130, such as 3/4 inches, connects the transition piece 122 to the nozzle 134 via a claw-like coupling 132. The transition joint 122 is used to gradually reduce the inner diameter of the path taken by the abrasive media 118 from the 1 inch diameter blast tube 124 to the smaller diameter acceleration tube 130.
Details of the transition piece 122 and nozzle 134 are shown in cross-section in fig. 9. The coupling 122 includes a housing 128 that encloses an aperture (not shown). The injection pipe side 125 of the transition piece 122 has a 1 inch inner diameter bore, while the accelerator side 130 of the transition piece 122 has an 3/4 inch diameter bore. Each side of the transition piece 122 is connected to a respective tube using conventional claw coupling 132 techniques.
The outlet diameter 136 of nozzle 134 is sized to control the desired abrasive "hot spot" diameter so that the effective spray area of the noise reducing abrasive spray system can be matched to that of a conventional supersonic nozzle.
Other preferred embodiments of the noise reducing abrasive blasting system of the present invention are the following systems: the system includes more than one acceleration tube portion and employs more than one transition coupling, each of the acceleration tubes having a reduced inner diameter. Other types of couplings, nozzles, metering valves, and abrasive media may be employed in the system of the present invention without departing from the scope of the invention.
More details are given below regarding how the nozzle according to the invention is designed in various embodiments of the invention in the following configurations: this configuration uses a converging portion, a throat portion, a diverging portion, and a straight portion in that order. One-dimensional supersonic flow in a conduit with friction can be represented by the following equation, where x 1 And x 2 Is a location of interest, and M 1 And M 2 Corresponding to the local mach numbers at these locations. D is the diameter of the pipe, f is the coefficient of friction, and γ is the specific heat ratio:
wherein the wall shear stress τ is related to the coefficient of friction by:
if L is * Defined as the length position at which the mach number in the pipe is reduced to 1 by friction, the following well-known relationship is obtained:
wherein the average coefficient of friction is defined as:
the local temperature, static pressure, density and total pressure associated with the local temperature, static pressure, density and total pressure at the throat of sonic velocity are given by the following equations, respectively:
to produce a noise-reduced version of a conventional nozzle, a conventional exit area to throat area ratio, which is the square A of the exit diameter to throat diameter ratio, may be examined e /A*＝(D e /D*) 2 . The area ratio then determines the mach number at the end of the diffuser section according to the well-known area mach number relationship:
then the exit Mach number M of the convergent part e Used with the coefficient of friction of the pipe wall and the equation for determining the length of pipe required to reduce the mach number inside the pipe to 1. Then the length L * The length of the straight section required for the nozzle to produce mach 1 number at the outlet without any abrasive media. Any length beyond this length will produce a positive shock wave at the outlet. Since a positive shock wave has subsonic flow downstream of the shock wave, the flow velocity and hence the sound produced by the flow is significantly reduced.
Equation of the previousRearranging the equations to solve for L * The following results were produced:
abrasive jet nozzles use some type of abrasive that is accelerated in the nozzle as it moves toward the outlet. As the abrasive particles are accelerated, energy is transferred from the stream to the particles. The effect of adding abrasive to the flow is similar to increasing the coefficient of friction of the straight section and thus reducing the length required to achieve a positive shock wave at or immediately before the outlet. Generally, the more abrasive added to the flow, the shorter the length of the straight pipe section required to achieve a positive shock wave at or immediately before the outlet. A more detailed estimate of the effect of the abrasive can be calculated starting from the resistance from one abrasive particle,
wherein, U rel Is the relative velocity of the air/gas stream to the particle velocity, and, d particle Is the diameter of the abrasive particles. Number of particles n in a specific volume p Can be used to calculate the total force on the flow within the volume according to the following equation:
F volume ＝n p F particle drag
the average may be used for the approximate calculation, although a more accurate calculation would include the change in the entire volume. N in a straight section of length L p The values can be approximated according to the following equation:
wherein Q is abs Is the mass rate of consumption of abrasive material, Q air Is the volume rate of the gas flow, D is the diameter of the straight section, L is the length of the straight section, and m p Is the abrasive particle mass. The particle mass can be calculated according to the following equation:
then
From this resistance value to volume, e.g. the volume of the straight part of the quiet nozzle, the equivalent additional force from the abrasive on the fluid as a function of the wall area can be calculated by the following equation:
although this is not a shear force, because the force on the fluid volume is divided by the wall area rather than the cross-sectional flow area, the same sign as the shear force is used so that the force can eventually merge into L * In the equation (2).
Then, the approximate length at which mach number becomes 1 may be calculated based on the following equation, where M denotes the mach number at the beginning of the straight section:
thus, the length is considered to be the minimum length of the straight portion after the diverging portion, which is after the throat, which is after the converging portion. This length assumes that the outlet pressure is equal to the back pressure or pressure after the outlet. Deviations from this assumption will result in: the shock wave moves outwardly in the case where the outlet pressure of the straight portion is greater than the back pressure or moves inwardly in the case where the outlet pressure of the straight portion is less than the back pressure. These deviations can be quantified using known methods based on the pressure at the nozzle inlet, the ratio of the nozzle throat area to the nozzle exit area, and the back pressure (typically the local atmospheric pressure). Typically, where the flow is sonic, i.e. mach number 1, the exit pressure is a function of the pressure upstream of the throat and the ratio of the exit area of the diffuser section to the throat area. Thus, control of the upstream pressure at the inlet of the converging portion controls the outlet pressure.
The noise reducing abrasive jet nozzle may also take the form of a standard nozzle with an attachment that is attached to the end via threads or clamps or other known securing methods or devices. Thus, any of the characteristics of the straight portion of the noise reducing abrasive jet nozzle described herein may be applied to the straight portion of such an attachment, and vice versa. For standard nozzles lacking threads at the outlet of the diverging section, threads may be machined into the diverging section to mate with threads on an accessory (or fixture), or a clamp or other fixture may be used. Many different types of clamps for connecting adjacent tubular objects are known. Such attachments in embodiments are the same as the "straight portions" of the nozzles described herein, except that they may be separate from the other components of the nozzles. In this manner, the standard nozzle may be reconfigured as a quiet noise reducing abrasive jet nozzle. These accessories and the method of dimensioning these accessories follow the same design principles and steps as already outlined herein. The attachment may be provided separately and/or with the fixing means to facilitate use in retrofitting existing standard nozzles, or the attachment may be provided with the remainder of the nozzle and optional fixing means. The remainder of the nozzle may be a standard nozzle or may be a custom or standard nozzle that has been specifically adapted to removably secure the attachment to the diffuser portion of the nozzle, for example by providing threads on the end of the diffuser portion. The attachment and the diffuser portion of the nozzle may have various known securing structures built into them to help removably secure the attachment to the diffuser portion. In embodiments, various accessories (with or without the remainder of the nozzle) may be provided for use with various corresponding gas/abrasive particle mixtures and/or pressures.
Examples of the invention
Manufacture and testing of initial prototypes
A prototype including the component parts shown in fig. 8 and 9 was manufactured as shown in fig. 10, having the following characteristics for testing:
four meters accelerator section with 3/4 inches inner diameter to achieve sonic conditions (345m/s)
Straight orifice nozzle with 0.79 orifice diameter to match the output diameter of nozzle No. 8, to obtain the same "hot spot" as the current standard No. 8 setup "
A coupling, etc.
The sound pressure level is measured using both a handheld integrated sound pressure meter and a separate microphone data acquisition system. The nozzle pressure measured near the end of the 1 inch pipe before the coupling was 40 psi. The V-media is introduced by opening the media valve 4 full turns. The sound pressure level test results in dB are as follows:
| nozzle for spraying liquid | Integral sound pressure level (dB) |
| Standard No. 8 | 108 |
| QB-1 prototype | 94.5 |
Productivity was qualitatively assessed by using both a number 8 nozzle and a prototype of the present subject matter on a half exposed coated bakeware for 30 seconds, as shown in fig. 11. The effect of adjusting the knob of the abrasive metering valve was examined by adjusting the knob used for the prototype to six revolutions and comparing the throughput of this setting to a standard No. 8 nozzle using a four revolution setting.
Figure 12 shows that the prototype operating in the six-turn setting is significantly more efficient than standard No. 8 operating in the four-turn setting. These results show that the present invention can operate with equal or better productivity than a standard No. 8 nozzle, while producing 16dB of low noise as measured at the operator.
Tests were also performed to examine the total sound pressure level and sound spectrum of the prototype compared to a standard nozzle number 8, both of which were run at 40 psi. The test results demonstrate that the noise reduction is broad-spectrum, as shown in fig. 13.
Other preferred embodiments of the noise reducing abrasive blasting system of the present invention are systems employing a new nozzle having a straight section after the diverging section to accelerate the media particles to a desired velocity before the particles exit the blasting nozzle. Such a low-noise abrasive blasting nozzle is suitable for replacing a nozzle such as a standard No. 6 nozzle, and improves blasting productivity and reduces noise generation. The outlet shockwave condition of the new nozzle is designed to provide a significant reduction in jet noise from the stream exiting the nozzle. Comparative testing between the new nozzle and the existing commercial nozzle achieved a noise reduction of 17db (a), while the productivity was shown to be improved in the tests using garnet. CFD modeling shows improved particle acceleration zones. Furthermore, using the new nozzle with steel shot compared to using the standard No. 6 nozzle, the evaluation showed: the productivity is improved; the noise is reduced; and the productivity is improved; acoustic noise is reduced; and reduces operational fatigue.
Fig. 14A to 14B are a side view and a perspective view of a standard No. 6 nozzle 1400, respectively. The overall length of the nozzle shown is 6.53 inches, with the converging portion 1410 being 2.80 inches in length, the throat 1420 being 0.5 inches in length, and the diverging portion 1430 being 3.13 inches in length, the opening having an inner diameter of 1.25 inches, a throat diameter of 0.38 inches, and an outlet diameter of 0.55 inches. The outlet portion 1440 is 0.10 inches in length and is also divergent. Nozzles are standard for abrasive blasting operations. A conventional nozzle is a convergent/divergent nozzle such as standard No. 6. The particular version shown has a wider inlet, which means that the uniformity of particle distribution is enhanced. This particular version has a converging portion at the inlet, a straight throat portion 6/16 inches in diameter (hence the name No. 6), and a diverging portion that then continues to the outlet. The peak velocity of this design occurs at (and after) the exit. Fig. 15 is a cross-sectional view of nozzle No. XL6, 1500, which, as shown, has an overall length of 11.71 inches and a longer diverging portion 1530(8.31 inches instead of 3.13 inches) compared to the standard nozzle No. 6 shown in fig. 14A-14B. The converging portion 1510, throat 1520, and exit 1540 are identical.
Fig. 16A to 16B are a side perspective view and a sectional view, respectively, of a modified spray nozzle 1600 according to an embodiment of the present invention. The overall length of the nozzle is shown as 9.07 inches, with the throat 1620 having a length of 0.50 inches, the diverging section 1630 having a length of 3.13 inches, and the straight section 1650 having a length of 2.56 inches, with the converging section 1610 making up the remaining length. The opening has an inner diameter of 1.25 inches, a throat diameter of 0.375 inches, and a straight portion diameter of 0.55 inches. The angle of convergence is 8.88 degrees and the angle of the diverging outlet portion 1640 is 50 degrees. Fig. 17A-17B are a side perspective view and a cross-sectional view, respectively, of an improved spray nozzle 1700 extending in length, the nozzle 1700 having a converging portion 1710, a throat 1720, a diverging portion 1730, a straight portion 1750, and an outlet portion 1740, according to an embodiment of the present invention. This nozzle 1700 has a longer straight portion 1750 compared to the nozzle 1600 shown in fig. 16A-16B, and the overall length of this nozzle 1700 is similar to the overall length of XL6 nozzle shown in fig. 15, with the overall length of this nozzle 1700 being 11.71 inches. The dimensions are the same as those of the nozzle 1600 shown in fig. 16A-16B, except that the straight portion 1750 is 5.20 inches in length.
Since the sound generated from the air exiting the nozzle is largely dependent on the air velocity, a design with a lower air exit velocity without reducing the abrasive particle velocity allows for equal or higher production rates while greatly reducing the sound volume. The new nozzle employing this method adds a straight portion (neither converging nor diverging) to the end of the diverging portion of the conventional nozzle design. This extends the particle acceleration section while reducing the exit mach number as energy is transferred from the air to the particles. The extension of the accelerating portion is based on the maximum mach number reached at the end of the diffusing portion. In various embodiments, the length of the straight portion is in the range from 1/5 a of the nozzle throat diameter to ten times the nozzle throat diameter, but may also extend to 10 times the diameter of the straight portion. The increased interaction distance between the slower abrasive in the flow and the air slows the air in a manner similar to wall friction, thereby accelerating the abrasive particles more efficiently while reducing the nozzle exit velocity.
FIG. 18 is a schematic diagram illustrating the convergent-divergent nozzle expansion under over-expansion 1810, under full expansion 1820 and under expansion 1830 conditions. Conventional spray nozzles typically operate in what is considered an over-expanded state, meaning that the flow passes through an inclined shock wave 1870 as the flow exits and constricts 1840 behind the nozzle exit. The flow is supersonic at the divergent portion throughout the nozzle and at the outlet, and the jet pressure is adjusted to atmospheric pressure by means of an oblique shockwave 1840 outside the plane of the outlet. In contrast, the fully expanded flow 1850 does not expand or contract after the outlet, while the under-expanded flow 1860 expands in an expansion fan 1880 after the outlet.
Considering nozzle number 6, a full expansion nozzle with an outlet to throat area ratio a/a ═ 2.15 would be driven by the 183psi pressure reservoir and achieve an outlet mach number of 2.3. Under appropriate circumstances, reducing the reservoir pressure may induce a positive shock wave at the exit plane of the nozzle, thereby significantly reducing the velocity of the gas as it exits the nozzle. However, lowering the reservoir pressure of conventional abrasive jet nozzles reduces particle velocity and makes such an arrangement impractical. However, when the supersonic portion is uniformly extended, the effect of the injected media on the supersonic flow structure results in the formation of a positive shock wave at a pressure higher than the intended reservoir. The longer high mach number nozzle portion followed by a positive shock wave at the nozzle exit reduces the exit velocity of the air and thus the generation of noise. This has the same effect as operating an abrasive-free nozzle at a sufficiently low pressure to produce a positive shock wave at the outlet. Having a positive shock wave at the outlet significantly reduces the air outlet velocity with little effect on the net abrasive velocity.
The straight cylindrical section also causes some frictional losses due to wall surface roughness only, which results in a slightly lower mach number towards the nozzle end. For example, for a nominal coefficient of friction of 0.005 over the length of a straight section of 2.56 inches, this would result in a mach number drop from M2.3 to M1.8. This condition is even more over-inflated and more likely to result in a positive shock wave where the output is subsonic and quiet.
Fig. 19A-19B are CFD results 1900, 1901 showing mach number distributions at 67psig nozzle pressure for a media-free single-phase compressible gas stream using ANSYS Fluent for a standard No. 6 nozzle (fig. 19A) and a modified nozzle according to an embodiment of the present invention (fig. 19B). Fig. 20A-20B are CFD results 2000, 2001 showing mach number distributions at 100psig nozzle pressure using ANSYS Fluent for a standard No. 6 nozzle (fig. 20A) and a modified nozzle according to an embodiment of the present invention (fig. 20B). The results clearly show that the improved nozzle has an extended acceleration portion under various conditions compared to the standard No. 6 nozzle. In this model, at 67psig, the modified nozzle had a slightly lower maximum mach number (2.21 versus 2.26) than the standard No. 6 nozzle, but had a longer cross-section where supersonic flow existed to accelerate the particles. Similar results were found at a nozzle pressure of 100 psig.
Fig. 21A-21B are CFD results 2100, 2101 showing mach number distributions at 67psig nozzle pressure using ANSYS Fluent with increased wall drag for a standard No. 6 nozzle (fig. 21A) and a modified nozzle according to an embodiment of the present invention (fig. 21B). Increased wall resistance uses an increased wall coefficient of friction to simulate the resistance of particles to flow. The main implication from this result is that the longer straight nozzle portion of the improved nozzle has a greater impact on the flow structure.
FIG. 22 is a graph showing the averaged 1/3 octave spectra for various nozzles, and is discussed in more detail below.
FIG. 23 is a cross-sectional view of a standard converging-diverging abrasive jet nozzle 2300 of the prior art, showing Mach number 1 at the throat 2304 and Mach number greater than 1 at the outlet 2310. The converging portion 2303 extends from the inlet of the nozzle to the beginning of the throat 2303, and the diverging portion 2306 extends from the end of the throat 2305 to the end of the nozzle 2307.
Fig. 24 shows a cross-section of a nozzle 2400 in accordance with an embodiment of the present invention, where a converging portion 2402 extends from an inlet 2401 of the nozzle to a beginning 2403 of a throat 2404, the throat 2404 ending at 2405, and after the throat 2404 is a diverging portion 2406 that transitions at a point 2407 to a straight barrel portion 2408, the straight barrel portion 2408 extending to an end 2409 of the nozzle. The mach number at the exit 2407 of the diffuser section is M1 greater than 1. L is * Indicating the length of the straight cylindrical portion 2408 over which the flow will become sonic (M1) due to wall friction. At the outlet 2410, the flow has a Mach number M of less than 1 e 。
Fig. 25 shows a cross-section of a nozzle 2500 according to an embodiment of the invention where a converging portion 2502 extends from an inlet 2501 to a beginning 2503 of a throat 2504 followed by a diverging portion 2506, the diverging portion 2506 extending from an end 2505 of the throat to a beginning 2507 of a straight cylindrical portion 2508, the straight cylindrical portion 2508 continuing to an end 2509 of the nozzle. In the flow of abrasive particles 2512 through the nozzle 2500, Δ L represents L * The introduction of abrasive particles 2512 serves to reduce energy in the flow due to the reduced length of abrasive particles 2512 relative to the nozzle shown in fig. 24.
FIG. 26 shows a view according to the present inventionThe nozzle 2600 of an embodiment of the invention has a cross-section in which the converging portion 2602 is followed by a throat 2604, the throat 2604 extends from a throat inlet 2603 to a throat outlet 2605, the throat 2604 is followed by a diverging portion 2606, the diverging portion 2606 extends from the throat outlet 2605 to an inlet 2607 of a straight cylindrical portion 2608, the straight cylindrical portion 2608 terminating at an end 2609 of the nozzle, wherein the abrasive particles 2612 are in flow, and the mach number plot 2620 represents mach number (M) along the axial dimension (x) of the nozzle. For an optimized nozzle designed according to the present invention, mach number remains above 1 up to the exit, which is marked by the label "L ═ L * "outline 2622 indicates. For a less optimized nozzle designed according to the present invention, where the length of the straight portion 2608 is equal to L * By contrast, mach number will drop below 1 in the straight portion 2608 and then rise to 1 at the exit 2610, as shown by profile 2624.
Fig. 27 shows a cross-section of a nozzle 2700 according to an embodiment of the invention, where the converging portion 2702 is followed by a throat 2704, the throat 2704 extends from a throat inlet 2703 to a throat outlet 2705, the throat 2704 is followed by a diverging portion 2706, the diverging portion 2706 extends from the throat outlet 2705 to an inlet 2707 of a straight cylindrical portion 2708, the straight cylindrical portion 2708 terminates at an end 2709 of the nozzle, where abrasive particles 2712 are in flow, and a mach number plot 2720 represents mach number (M) along the axial dimension (x) of the nozzle. The contours 2722, 2724, 2726 illustrate the effect of increasing or decreasing nozzle pressure on the outlet conditions of the straight portion of the nozzle. When the outlet pressure p e Is equal to the back pressure p b And the length L of the straight portion 2708 is equal to L * A shockwave is formed in the flow at the outlet, as shown in profile 2722, producing subsonic flow after the outlet. Increasing the nozzle pressure p 0 Resulting in a higher outlet pressure p e And when p is e Exceeding the back pressure p b When, as shown in profile 2726, a supersonic outlet flow with higher noise is produced. To avoid supersonic outlet flow at such nozzle pressures, the length L of straight portion 2708 may be increased to exceed L * And/or may be sprayedThe friction of the inner wall of the nozzle and/or the abrasive particles increases so that the air flow velocity in the straight section decreases faster. Lowering the nozzle pressure results in a lower outlet pressure p e And the shockwave moves upstream from the outlet, with particle acceleration falling slightly due to the lower mach number profile, as shown in profile 2724.
The productivity and noise performance of the new nozzle described above was compared to standard commercially available nozzle number 6, including standard nozzle number 6 and extra long (XL) nozzles. Prior to testing, 20 panels of 18 inch x18 inch steel 14 were uniformly powder coated (coating thickness from 10 mils to 12 mils) to be used to evaluate nozzle productivity (time required to clean the panels to a set level). All tests were performed with a new 30/40 garnet medium at 67psi nozzle pressure.
For each nozzle tested, the sound level was measured with a sound level meter at the left shoulder of the operator when the nozzle was operated in the open air (to avoid the sound produced by sand hitting the metal during actual spraying). The sound level of the 1/3 octave band was measured for a time of 10 seconds, and the MIN sound level, MAX sound level, and AVG sound level were automatically calculated and stored. The background sound level was also recorded to confirm that the background noise did not have an effect on the measured nozzle noise level.
Next, a video of each nozzle was recorded while the nozzle was used to spray one side of the powder coated test panel. Video recordings were used to quantify the throughput rate (the time required to clean the test panel to the desired finish) for each nozzle. Feedback from the shooter after using each nozzle, including impressions of sound level and productivity, were also recorded.
Table 1 summarizes the main results of the tests and some operator reviews. According to the first test run, the quietest and highest productivity nozzle was the modified nozzle known as the Oceanit BN6V1 or Oceanit Short SS, which was the nozzle schematically shown in fig. 17A to 17B. The nozzle was quiet by 16dB and cleaned the test panel in 51 seconds, while the standard long nozzle was 69 seconds. The XL nozzle (No. XL 6) shows some improvement in sound performance, but productivity is not improved, and is considered too large and heavy for daily use.
TABLE 1 summary of test results (30/40 garnet, at 70psi nozzle pressure)
Based on the results of the first round, a second trial was performed on a standard nozzle number 6 and two Oceanit nozzles with straight portions (also shown in table 1). Likewise, the Oceanit Short SS is the operator's favorite nozzle and is 15.2dB quieter than the standard nozzle No. 6 and cleans the test panel within 39 seconds (while the standard nozzle No. 6 is 41 seconds). Oceanit BN6-V1 was significantly quieter than the standard No. 6 nozzle, such that the operator felt it unnecessary to protect the ears, Oceanit BN6-V1 was more productive, less recoil, and less thermally warped the test panel.
The average sound level 2200 measured for the 1/3 octave band is shown in fig. 22. These confirm that the sound levels of the two new nozzles 2230(BNG-V1), 2240(BNG-V2) with straight sections are lower over the entire frequency spectrum compared to the standard nozzle 2210 and also significantly lower over most of the frequency spectrum than the XL nozzle 2220. It is also worth noting that the spike 2250 of the standard nozzle (standard No. 6) is centered at 4000 hertz, which may be associated with greater turbulence generated by the high velocity jet and/or jet squeal, which is avoided by the subsonic exit velocity after the positive shock wave at the nozzle exit.
Additional tests were performed on a new nozzle (Oceanit BN6V1) with a shorter straight section with a standard No. 6 nozzle using shot media at a nozzle pressure of about 90 psi. The same coated panel described for the above test was used to measure the productivity of the nozzles (time to jet clean the panel). Two trials were performed for each nozzle. The results are shown in table 2 below. In the first test, the new nozzles performed the same as the standard nozzles (the time for each nozzle to clean the panel was about 53 seconds). In the second trial, the new nozzle outperformed the standard nozzle (30 seconds versus 47 seconds). In general, the second trial is more reliable because the user has time to adapt to a particular nozzle.
Table 2: shot, 90 psi.
Accordingly, the new noise reducing abrasive jet nozzle has proven to be superior in commercial abrasive jet environments. High particle velocities produce high productivity nozzles. The low outlet air velocity produces a low noise nozzle. The new nozzle maintains or increases the velocity of the abrasive particles exiting the nozzle while reducing the exit air velocity. The new nozzle (based on nozzle number 6) uses an extended exit section that lengthens the high mach number acceleration region of the nozzle while producing, in part (in some embodiments), a much lower exit velocity by creating a positive shockwave at the nozzle end. In tests using garnet and steel shot, the productivity of the new nozzle was shown to be superior to the standard No. 6 nozzle, while achieving a 17dB reduction in noise over commercial nozzles, reduced backlash and resulting user fatigue, and improved operating characteristics. CFD modeling shows improved particle acceleration zones.
Reducing the exposure of the employee to dangerous noise below the OSHA 8 hour time weighted average alleviates the need for employers to modify employee current practices, reduces the need for Personal Protective Equipment (PPE), reduces the likelihood of injury in the event of PPE failure, and ensures that personnel in the adjacent "safe area" are guaranteed protection from exposure. Most importantly, reducing the noise in the jetting facility to 90dBA or less allows workers to operate up to an 8 hour standard working day with OSHA compliance. It should also be appreciated that minimizing noise by 3dBA would be beneficial to workers using such quieter nozzles. In practice, reducing the noise by, for example, 6dBA would be very important to reduce the risk of worker injury.
Although the above describes testing of an embodiment of nozzle number 6, other embodiments may be any size including nozzle number 8, 7, and 5, or 90 degree nozzle number 6 or other 90 degree nozzles. The same design may be applied to any converging-diverging nozzle using any type of abrasive media/material including coal slag, garnet, acrylic, and the like. Typically, compressed air is used. Water vapor may be used in some embodiments. The new nozzle may be made of, for example, tungsten carbide, silicon carbide, boron carbide, acrylic, ceramic, stainless steel, hardened steel, aluminum, any other known nozzle material, or combinations thereof (with or without a wear resistant ceramic liner). The nozzle may have a protective handle to improve operation and eliminate static concerns with stainless steel versions. The nozzle may be designed for and used with various line pressures and injection modes.
As will be understood from the above description and the description, drawings, and examples referenced herein, the noise reducing abrasive blasting system of the present disclosure allows abrasive blasting with significantly reduced resulting noise while providing equivalent or improved productivity and efficiency as compared to conventional abrasive blasting systems. Such an improved noise reducing abrasive blasting system promotes worker health and safety and provides a quieter environment for nearby personnel.
Embodiments of the improved abrasive blasting system utilize elongated accelerator sections in the tubes and/or nozzles to maintain particle velocity while reducing gas exit velocity. Straight orifice nozzles may be used to create the desired effective abrasive area. The maintained particle velocity provides equivalent abrasive production rate, while the reduced gas velocity provides reduced resulting noise.
While particular preferred embodiments and examples of the manufacture and testing of the invention have been shown and described, it will be obvious that the invention is not limited thereto. Numerous modifications or changes, variations, alterations, substitutions and equivalents will occur to those skilled in the art without departing from the spirit and scope of the present invention and are considered to be part of the invention disclosed herein.
By way of example and not limitation, the size and coupling type of nozzles and tubes, as well as the specific configuration and size of the tubes, couplings, nozzles and accelerator portions, may be varied in accordance with the general principles of the invention as described herein to accommodate different operating conditions, target materials, project specifications, budget considerations and user preferences. The nozzle may have any throat diameter, such as 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc., included in embodiments featuring a new nozzle with a straight portion. Further, more than one transition coupling and accelerator tube portion and inner diameter may be employed in the system of the present invention. The invention described herein includes all such modifications and variations.
Furthermore, the present invention should be considered to include all possible combinations of each of the features set forth in the present specification, appended claims, and/or drawings, which may be considered new, inventive, and industrially applicable.
Many variations and modifications are possible in the embodiments of the invention described herein. Although certain illustrative embodiments of the invention have been shown and described herein, a wide range of modifications, changes, and substitutions is contemplated in the foregoing disclosure. While the above description contains many specifics, these should not be construed as limitations on the scope of the invention, but rather as exemplifications of one or another preferred embodiment thereof. In some instances, some features of the present invention may be employed without a corresponding use of the other features.
Accordingly, the foregoing description should be construed broadly and understood as being given by way of illustration and example only, the spirit and scope of the invention being limited only by the ultimately issued claims.
Claims (54)
1. A high productivity, quiet abrasive jet nozzle comprising:
a converging portion having a converging inner diameter;
a throat connected to the converging portion;
a diffuser portion connected to the throat; and
a straight portion connected to and immediately behind the diffusion portion;
wherein the straight portion has the following length: the length of the straight portion is such that when the spray nozzle is operated at a predetermined mixture of gas and particles and a predetermined pressure, the velocity of gas exiting the spray nozzle is reduced by at least 30% relative to the spray nozzle with the straight portion removed; and
wherein, in operation, fluid flows sequentially through the converging portion, the throat portion, the diverging portion, and the straight portion.
2. A high productivity quiet abrasive jet nozzle as claimed in claim 1, wherein the inner diameter of said straight section is less than the maximum inner diameter of said diverging section.
3. A high productivity, quiet abrasive jet nozzle assembly comprising the noise reducing abrasive jet nozzle of claim 1.
4. A high productivity quiet abrasive blasting nozzle according to claim 1, wherein the nozzle is configured such that: for the predetermined mixture of gas and particles and the predetermined pressure, the supersonic flow of gas is isolated to the interior of the nozzle and accelerates the abrasive particles in the straight section.
5. A high productivity quiet abrasive blasting nozzle according to claim 1, wherein the nozzle is configured such that: the gas mach number at the outlet of the straight section is less than the gas mach number at the outlet of the diffuser section for the predetermined mixture of gas and particles and the predetermined pressure, resulting in reduced operating noise.
6. A high productivity quiet abrasive blasting nozzle according to claim 5, wherein the nozzle is configured such that: for the predetermined mixture of gas and particles and the predetermined pressure, the gas mach number decreases from a gas mach number greater than 1 at the outlet of the diffusing section to a gas mach number of 1 at the outlet of the straight section.
7. A high productivity quiet abrasive jet nozzle as claimed in claim 1, wherein said length of said straight section is at least two tenths of the inner diameter of said straight section.
8. A high productivity quiet abrasive jet nozzle as claimed in claim 1, wherein said length of said straight section is less than ten times the inner diameter of said straight section.
9. A high productivity quiet abrasive jet nozzle as claimed in claim 1, wherein said length of said straight section is between 1 and 10 inches.
10. A high productivity quiet abrasive jet nozzle as claimed in claim 1, wherein said length of said straight section is 2.5 inches.
11. A high productivity quiet abrasive jet nozzle as claimed in claim 1, wherein said straight section is configured to be attached to and detached from said diverging section.
12. A high productivity quiet abrasive jet nozzle as claimed in claim 11, further comprising one or more additional straight sections configured to be attached to and detached from said diverging section, wherein said straight section and said one or more additional straight sections each have a different length and/or a different inner diameter.
13. A high productivity quiet abrasive jet nozzle as claimed in claim 12, wherein each of said one or more additional straight sections has a length of: the length of the one or more additional straight portions is such that when the spray nozzle is operated with a different predetermined mixture of gas and particles and a predetermined pressure, the velocity of gas exiting the spray nozzle is reduced by at least 30% relative to the spray nozzle with the straight portions removed.
14. A high productivity quiet abrasive jet nozzle as claimed in claim 1, wherein said straight portion is cylindrical in shape.
15. A high productivity quiet abrasive blasting nozzle as claimed in claim 1, wherein said nozzle is a No. 4 nozzle, a No. 5 nozzle, a No. 6 nozzle, a No. 7 nozzle or a No. 8 nozzle.
16. A high productivity quiet abrasive jet nozzle as claimed in claim 1, further comprising a fluid flowing through said diffuser section and having a mach number greater than 1 at an outlet from said diffuser section to said straight section.
17. A high productivity quiet abrasive jet nozzle as claimed in claim 1, further comprising a fluid flowing through said straight section and having a Mach number of 1 at the exit of said straight section.
18. A high productivity quiet abrasive jet nozzle as claimed in claim 1, further comprising a plurality of abrasive particles in a supersonic fluid stream inside said nozzle, said supersonic fluid stream being subjected to shock waves in said straight section.
19. A high productivity quiet abrasive blasting nozzle as claimed in claim 1, wherein said nozzle is made from a material selected from: tungsten carbide, silicon carbide, boron carbide, acrylic, ceramic, stainless steel, hardened steel, aluminum, or combinations thereof.
20. A high productivity quiet abrasive blasting nozzle as claimed in claim 1, wherein said nozzle further comprises at least one protective grip.
21. A high productivity quiet abrasive jet nozzle as claimed in claim 1, wherein said length of said straight section is such that: the injection nozzle has a noise level of 90dBA or less when operating at the predetermined mixture of gas and particles and a predetermined pressure.
22. A high productivity quiet abrasive jet nozzle as claimed in claim 1, wherein said length L of said straight portion is at least L * Said L is * Given by the following equation:
wherein for a predetermined mixture of gas and abrasive particles, D is the diameter of the straight section, M is the Mach number of the fluid at the inlet of the straight section,
is the average coefficient of friction of said straight portion, f abrasives Is the coefficient of friction of the particles in the fluid stream, and γ is the specific heat ratio of the fluid stream.
23. A high productivity quiet abrasive jet nozzle as claimed in claim 1, wherein said length L of said straight portion is at least L * Said L is * Is regulated according to the ratio of back pressure to outlet pressure, where L * Given by the following equation:
wherein for a predetermined mixture of gas and abrasive particles, D is the diameter of the straight section, M is the Mach number of the fluid at the inlet of the straight section,
is the average coefficient of friction of said straight portion, f abrasives Is the coefficient of friction of the particles in the fluid stream, and γ is the specific heat ratio of the fluid stream.
24. A method for manufacturing the nozzle of claim 1 to reduce noise of the nozzle without reducing the nozzle productivity, the method comprising:
determining a minimum length of the straight section of claim 1 for the predetermined mixture of gas and abrasive particles and predetermined pressure, the minimum length of the straight section being the length required for the gas to produce a mach number of 1 at or within a straight section inner diameter before exiting the straight section; and
fabricating the nozzle having a straight portion having a length equal to or greater than the minimum length.
25. The method of claim 24, further comprising:
determining an optimum length of the straight section according to claim 1 such that the Mach number of the gas decreases from a peak at a first point that is an end of the diffuser section to a Mach number of 1 at a second point at or within a length equal to the inner diameter of the straight section before the exit of the straight section without entering subsonic velocity between the first and second points; and
manufacturing the nozzle with the straight portion of the optimal length.
26. The method of claim 25, wherein the step of determining the optimal length comprises:
analysing the effect of friction from the wall of the straight portion, and/or
The effect of the plurality of abrasive particles on the reduction of the air flow velocity in the straight section is analyzed.
27. The method of claim 24, further comprising: adjusting the length of the straight portion according to a particular operating condition to determine the length of the straight portion that produces the desired combination of sound reduction and productivity; and fabricating the nozzle having the length.
28. The method of claim 24, further comprising: repeated computer simulations of the nozzle of claim 1 over the length of a series of straight sections to find a length with a desired combination of sound reduction and productivity; and fabricating the nozzle having the length.
29. A nozzle attachment for high productivity quiet abrasive blasting comprising:
a straight tubular portion for connection to an outlet of an abrasive jet nozzle;
wherein the straight tubular portion has a length of: the length of the straight tubular section is such that when the abrasive blasting nozzle is operated with a predetermined mixture of gas and particles and a predetermined pressure, the velocity of the gas leaving the abrasive blasting nozzle connected to the straight tubular section is reduced by at least 30%.
30. A nozzle attachment as claimed in claim 29, further comprising a fixing means for connecting the straight tubular portion to the abrasive blasting nozzle.
31. The nozzle attachment of claim 29, further comprising a fixture embedded in said straight tubular portion to assist in connecting said straight tubular portion to said abrasive jet nozzle.
32. The nozzle attachment of claim 29, wherein the straight tubular portion has an inner diameter that is less than a maximum inner diameter of a converging portion of the abrasive jet nozzle.
33. The nozzle attachment of claim 29, wherein the straight tubular portion is configured such that: for the predetermined mixture of gas and particles and the predetermined pressure, when the straight tubular portion is connected to the abrasive jet nozzle, the supersonic flow of gas does not continue beyond the outlet of the straight tubular portion and the supersonic flow of gas accelerates the abrasive particles in the straight tubular portion.
34. The nozzle attachment of claim 29, wherein the straight tubular portion is configured such that: when the straight tubular portion is connected to the abrasive blasting nozzle, the gas mach number at the outlet of the straight tubular portion is smaller than the gas mach number at the outlet of the diffuser portion of the abrasive blasting nozzle for the predetermined mixture of gas and particles and the predetermined pressure, thereby reducing the operating noise.
35. The nozzle attachment of claim 29, wherein the straight tubular portion is configured such that: when the straight tubular portion is connected to the abrasive blasting nozzle, the gas mach number decreases from a gas mach number greater than 1 at the outlet of the diverging portion of the abrasive blasting nozzle to a gas mach number of 1 at the outlet of the straight portion, for the predetermined mixture of gas and particles and the predetermined pressure.
36. The nozzle attachment of claim 29, wherein the length of the straight tubular portion is at least two tenths of the diameter of the straight tubular portion.
37. The nozzle attachment of claim 29, wherein the length of the straight tubular portion is less than ten times the diameter of the straight tubular portion.
38. The nozzle attachment of claim 29, wherein the straight tubular portion is between 1 and 10 inches in length.
39. The nozzle attachment of claim 29, wherein the straight tubular portion is 2.5 inches in length.
40. The nozzle attachment of claim 29, wherein the straight tubular portion is cylindrical in shape.
41. The nozzle attachment of claim 29, wherein the abrasive jet nozzle is a No. 4 nozzle, a No. 5 nozzle, a No. 6 nozzle, a No. 7 nozzle, or a No. 8 nozzle.
42. The nozzle attachment of claim 29, wherein the straight tubular portion is made of a material selected from the group consisting of: tungsten carbide, silicon carbide, boron carbide, acrylic, ceramic, stainless steel, hardened steel, aluminum, or combinations thereof.
43. The nozzle attachment of claim 29, wherein the length of the straight tubular portion is such that: when the straight tubular portion is connected to the abrasive blasting nozzle, the abrasive blasting nozzle has a noise level of 90dBA or less when operating at the predetermined mixture of gas and particles and a predetermined pressure.
44. The nozzle attachment of claim 29, wherein the straight tubular portion is longThe degree L is at least L * Said L is * Given by the following equation:
wherein, in a case where the straight tubular portion is connected to the abrasive-blasting nozzle, D is a diameter of the straight tubular portion, M is a Mach number of a fluid at an inlet of the straight portion, for the predetermined mixture of the gas and the abrasive grains,
is the average coefficient of friction of said straight portion, f abrasives Is the coefficient of friction of the particles in the fluid stream, and γ is the specific heat ratio of the fluid stream.
45. The nozzle attachment of claim 29, wherein the length L of the straight tubular portion is at least L * Said L is * Is regulated according to the ratio of back pressure to outlet pressure, where L * Given by the following equation:
wherein, in a case where the straight tubular portion is connected to the abrasive-blasting nozzle, D is a diameter of the straight tubular portion, M is a Mach number of a fluid at an inlet of the straight portion, for the predetermined mixture of the gas and the abrasive grains,
is the average coefficient of friction of said straight portion, f abrasives Is the coefficient of friction of the particles in the fluid stream, and γ is the specific heat ratio of the fluid stream.
46. A method for manufacturing the nozzle attachment of claim 29 to reduce noise of a connected abrasive blasting nozzle without reducing productivity of the nozzle, the method comprising:
determining a minimum length of the straight tubular section of claim 29 for the predetermined mixture of gas and abrasive particles and predetermined pressure, the minimum length of the straight tubular section being the length required for the gas to produce a mach number of 1 at or within a straight tubular section inner diameter prior to exiting from the straight section; and
manufacturing the straight tubular portion having a length equal to or greater than the minimum length.
47. The method of claim 46, further comprising:
determining an optimum length of the straight tubular portion according to claim 29 such that the mach number of the gas decreases from a peak at a first point which is an end of the diffuser section to a mach number of 1 at a second point at or within a length equal to the inner diameter of the straight tubular portion before the exit of the straight tubular portion without entering subsonic velocity between the first point and the second point; and
-manufacturing said straight tubular portion having said optimal length.
48. The method of claim 47, wherein the step of determining the optimal length comprises:
analysing the effect of friction from the wall of the straight tubular section, and/or
The effect of the plurality of abrasive particles on the reduction of the air flow velocity in the straight tubular section was analyzed.
49. The method of claim 46, further comprising: adjusting the length of the straight tubular portion according to a particular operating condition to determine the length of the straight tubular portion that produces the desired combination of sound reduction and productivity; and manufacturing the straight tubular portion having the length.
50. The method of claim 46, further comprising: repeated computer simulations of a straight tubular section according to claim 29 over a series of straight tubular section lengths to find a length having a desired combination of sound reduction and productivity; and manufacturing the straight tubular portion having the length.
51. A high productivity quiet abrasive jet nozzle as claimed in claim 1, wherein said length of said straight section is such that: when the injection nozzle is operated at the predetermined mixture of gas and particles and a predetermined pressure, the injection nozzle has a noise level that is reduced by 3dBA or more compared to an injection nozzle without the straight portion.
52. A high productivity quiet abrasive jet nozzle as claimed in claim 1, wherein said length of said straight section is such that: when the injection nozzle is operated at the predetermined mixture of gas and particles and a predetermined pressure, the injection nozzle has a noise level that is reduced by 6dBA or more compared to an injection nozzle without the straight portion.
53. The nozzle attachment of claim 29, wherein the length of the straight tubular portion is such that: when the straight tubular portion is connected to the abrasive blasting nozzle, the blasting nozzle has a noise level reduced by 3dBA or more when the blasting nozzle is operated with the predetermined mixture of gas and particles and a predetermined pressure compared to the abrasive blasting nozzle without the straight tubular portion.
54. The nozzle attachment of claim 29, wherein the length of the straight tubular portion is such that: when the straight tubular portion is connected to the abrasive blasting nozzle, the blasting nozzle, when operating at the predetermined mixture of gas and particles and at the predetermined pressure, has a noise level reduced by 6dBA or more compared to the abrasive blasting nozzle without the straight tubular portion.
Applications Claiming Priority (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| USPCT/US2019/065783 | 2019-12-11 | ||
| PCT/US2019/065783 WO2020123697A1 (en) | 2018-12-11 | 2019-12-11 | Reduced noise abrasive blasting systems |
| US16/819,035 US20200282517A1 (en) | 2018-12-11 | 2020-03-13 | Method and design for productive quiet abrasive blasting nozzles |
| US16/819,035 | 2020-03-13 | ||
| PCT/US2020/025586 WO2021118625A1 (en) | 2019-12-11 | 2020-03-28 | Method and design for productive quiet abrasive blasting nozzles |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN114829068A true CN114829068A (en) | 2022-07-29 |
Family
ID=76330311
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202080086029.XA Pending CN114829068A (en) | 2019-12-11 | 2020-03-28 | Method and design for high productivity quiet abrasive jet nozzle |
Country Status (7)
| Country | Link |
|---|---|
| EP (1) | EP4072778A4 (en) |
| JP (1) | JP2023505838A (en) |
| KR (1) | KR20220110268A (en) |
| CN (1) | CN114829068A (en) |
| AU (1) | AU2020399540A1 (en) |
| CA (1) | CA3159321A1 (en) |
| WO (1) | WO2021118625A1 (en) |
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- 2020-03-28 AU AU2020399540A patent/AU2020399540A1/en active Pending
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Also Published As
| Publication number | Publication date |
|---|---|
| EP4072778A4 (en) | 2024-01-17 |
| AU2020399540A1 (en) | 2022-06-09 |
| CA3159321A1 (en) | 2021-06-17 |
| EP4072778A1 (en) | 2022-10-19 |
| KR20220110268A (en) | 2022-08-05 |
| JP2023505838A (en) | 2023-02-13 |
| WO2021118625A1 (en) | 2021-06-17 |
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Effective date of registration: 20230303 Address after: Pennsylvania, America Applicant after: KENNAMETAL Inc. Address before: Hawaii, USA Applicant before: HOANA MEDICAL, Inc. |