A high-speed, low-temperature spray gun with a fuel premixing structure and its system

Abstract

The present invention discloses a high-speed, low-temperature spray gun and its system with a fuel premixing structure, belonging to the technical field of material surface modification and coating. The spray gun includes a powder feed needle, the outer shell of which is provided with a premixing air distribution unit I and a premixing air distribution unit II. The end of the powder feed needle is penetrated by a premixing common porous catalytic ceramic plate, which is connected to the combustion chamber. A premixing interlayer is provided between the premixing air distribution unit II and the premixing common porous catalytic ceramic plate. A gas channel and a powder feed needle-compressed air channel are provided within the premixing air distribution unit I, and the powder feed needle-compressed air channel is provided on the periphery of the powder feed needle. Air and gas inlets and a compressed air channel are provided outside the premixing air distribution unit I. The compressed air channel is connected to the air inlet, the powder feed needle-compressed air channel, the premixing interlayer, and the outer wall of the combustion chamber. The gas channel is connected to the gas inlet and the premixing interlayer. The spray gun can maintain a stable flame flow, reduce particle temperature, and inhibit particle oxidation and decomposition.

Description

Technical Field

[0001] The invention belongs to the technical field of material surface modification and coating, and particularly relates to a high-speed, low-temperature spray gun with a fuel premixing structure and a system thereof. Background Art

[0002] High-velocity oxygen-fuel (HVOF) spraying is an advanced coating technology. As a traditional thermal spray process, HVOF offers advantages such as high particle velocity, dense coating structure, and high deposition efficiency. However, when the spray powder is heated by the high-temperature flame, particles such as titanium alloys are subject to severe high-temperature oxidation, and oxide inclusions are easily generated on the particle surface. This reduces the service life of coatings such as titanium alloys, and their mechanical properties need to be improved. Furthermore, due to the high heat input during HVOF spraying, substrate deformation is easily caused during spraying of thin-walled substrates, limiting the application of HVOF technology on related materials.

[0003] Existing supersonic flame spray guns typically incorporate a mixing chamber outside the combustion chamber and inject cooling gas into the mixing chamber to reduce the flame temperature; alternatively, cooling gas is fed axially at the combustion chamber inlet to cool the flame. While both methods can reduce the spray temperature to a certain extent, the former method, with axial powder delivery, causes particles to overheat in the high-temperature combustion chamber, failing to effectively suppress oxidative decomposition. The latter method, on the other hand, offers a narrow adjustment range without affecting combustion, limiting the temperature control range and inhibiting oxidation of easily oxidized sprayed particles.

[0004] Chinese patent application CN116103601A discloses a high-speed, low-temperature spray gun and system for cooling the flame flow in a combustion chamber. The gun uses a non-premixing method, introducing compressed air and propane separately into the combustion chamber to achieve a state where the gases are not fully mixed and burned at the inlet section but fully burned at the combustion section. This ensures that the velocity and flame flow temperature of the sprayed powder are low upon entering the combustion chamber, preventing excessive temperature rise and suppressing particle oxidation and decomposition. This solves the problem of existing spray guns being unable to effectively suppress particle oxidation. However, the gun suffers from unstable combustion during use, requiring continuous ignition to maintain combustion. Summary of the Invention

[0005] In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a high-speed low-temperature spray gun and a system thereof with a fuel premixing structure to solve the problem that the existing spray guns cannot maintain stable combustion.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The first aspect of the present invention discloses a high-speed, low-temperature spray gun with a fuel premixing structure, characterized in that it includes a powder feed needle, the outer surface of which is provided with a premixing air distribution unit I and a premixing air distribution unit II, a premixing common porous catalytic ceramic plate is provided in a combustion chamber, the end of the powder feed needle penetrates the premixing common porous catalytic ceramic plate and is in communication with the combustion chamber, and a premixing interlayer is provided between the premixing air distribution unit II and the premixing common porous catalytic ceramic plate;

[0008] A gas channel and a powder feeding needle-compressed air channel are provided inside the pre-premixing air distribution unit I, and the powder feeding needle-compressed air channel is arranged outside the powder feeding needle; an air inlet and a gas inlet are provided at the end of the spray gun shell, and a compressed air channel is provided inside, one end of the compressed air channel is connected to the air inlet, and the other end is respectively connected to the powder feeding needle-compressed air channel, the premixing interlayer, the outer wall of the combustion chamber and the outer wall of the nozzle; one end of the gas channel is connected to the gas inlet, and the other end is connected to the premixing interlayer.

[0009] Preferably, the premixed common porous catalytic ceramic plate is provided with a plurality of through holes II for the premixed gas to pass through.

[0010] Further preferably, the thickness of the premixed common porous catalytic ceramic plate is 70% to 95% of the distance from the inlet of the premixed interlayer to the outlet of the premixed common porous catalytic ceramic plate.

[0011] Preferably, the premixed common porous catalytic ceramic plate is a silicon carbide ceramic plate.

[0012] Preferably, a matching nozzle sleeve is connected to the outside of the nozzle.

[0013] Further preferably, the nozzle is a straight-through nozzle or a Laval nozzle, and the corresponding nozzle sleeve is a straight-through nozzle sleeve or a Laval nozzle sleeve.

[0014] Preferably, the end of the powder feeding needle is connected to a powder feeding needle fixing device, and the powder feeding needle and the powder feeding needle fixing device are both fixed to the middle of the rear section of the spray gun housing, and both have a powder-cooling gas channel for the powder to be sprayed and the cooling gas to pass through.

[0015] Preferably, the combustion chamber consists of a contraction section, a combustion section and an inlet section. The contraction section is connected to the nozzle, and the inlet section is connected to the premixed common porous catalytic ceramic plate. A cooling gas distribution ring is provided on the side of the combustion section body close to the contraction section, and a cooling gas injection port and an ignition port are provided on the combustion section body on the opposite side of the cooling gas distribution ring.

[0016] Further preferably, the length l1 of the center line of the cooling gas injection port from the contraction section is 1 / 10 to 1 / 5 of the length l2 of the combustion section.

[0017] Preferably, cooling gas flow grooves are provided on the combustion chamber body and inside the cooling gas distribution ring, and a plurality of cooling gas inlets are provided on the cooling gas flow grooves. The cooling gas inlets, the interior of the combustion chamber and the cooling gas injection port are connected.

[0018] Further preferably, the number of cooling air flow inlets is 2n, n≥4, and the 2n cooling air flow inlets are arranged around the cooling air flow groove with the axial direction of the cooling gas injection port as the symmetry axis; the number of cooling air flow inlets on one side of the cooling gas injection port is n.

[0019] Preferably, the cross-sectional area S1 of the cooling air flow groove is more than 8 times the sum of the cooling air inlet opening areas S2.

[0020] Preferably, the aperture of the i-th hole on the axial side of the cooling gas injection port is the aperture of the first hole next to the axial side of the cooling gas injection port.

[0021] The second aspect of the present invention discloses a system containing the above-mentioned high-speed, low-temperature spray gun, comprising a control module, a gas module, a heating module, a powder feeding module and the above-mentioned high-speed, low-temperature spray gun, wherein the control module and the high-speed, low-temperature spray gun are respectively connected to the gas module, the heating module and the powder feeding module, and the gas module is respectively connected to the heating module and the powder feeding module.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention provides a high-speed, low-temperature spray gun with a fuel premixing structure. 1) Compared to existing non-premixing spray guns that use propane for cooling, this high-speed, low-temperature spray gun directs a portion of its compressed air into the powder feed needle-compressed air channel surrounding the powder feed needle, cooling the powder feed needle and preventing flashback and needle burnout. The compressed air then mixes with the powder feed gas to reduce particle oxidation, prevent overheating, and significantly enhance protection for the powder feed needle. 2) Compared to existing non-premixing spray guns, this high-speed, low-temperature spray gun directs another portion of its compressed air through a curved compressed air channel, with a portion entering the premixing interlayer between the premixing air distribution unit II and the premixing common porous catalytic ceramic plate, where it is fully premixed with the fuel gas. This premixing allows the premixing common porous catalytic ceramic plate to more fully exert its heating effect, thereby making the premixing structure spray gun easier to ignite, significantly increasing the gas pressure process window, and providing a more sustained and stable flame output. Furthermore, a stable Mach cone within the blue flame is present at the spray gun outlet. The remaining compressed air flows out of the spray gun along the combustion chamber and the outer wall of the nozzle, acting as a cooling circuit to prevent overheating. Tests have shown that when using this high-speed, low-temperature spray gun, the temperature is stable at 700-900K during the first ignition and around 850K during the second ignition. The flame flow is stable and can reduce the particle temperature, effectively preventing oxidation and decomposition of particles during the spraying process.

[0024] Furthermore, the premixed common porous catalytic ceramic plate is a silicon carbide ceramic plate, and the thickness h2 of the premixed common porous catalytic ceramic plate is 70%-95% of the distance h1 from the inlet of the premixed interlayer to the outlet of the premixed common porous catalytic ceramic plate, which can ensure that the fuel gas and compressed air are fully premixed in the premixed interlayer and maintain flame stability.

[0025] Furthermore, the high-speed low-temperature spray gun can use two sets of nozzles and nozzle sleeves, namely a straight-through nozzle and a straight-through nozzle sleeve, and a Laval nozzle and a Laval nozzle sleeve, to provide different process conditions and meet different spraying requirements.

[0026] Furthermore, a powder feeding needle fixing device added to the end of the powder feeding needle can ensure stable powder feeding.

[0027] Furthermore, a cooling gas distribution ring is provided on the side of the combustion section body close to the contraction section, and a cooling gas injection port is provided on the combustion section body on the opposite side of the cooling gas distribution ring, which can radially deliver the cooling gas into the combustion chamber, so that the particles can be cooled in time at the point where the temperature rises significantly, and on the basis of maintaining stable combustion, further suppress the oxidative decomposition of the powder to be sprayed.

[0028] Furthermore, the length l1 between the center line of the cooling gas injection port and the contraction section is 1 / 10 to 1 / 5 of the length l2 of the combustion section. The limited distance allows the powder to cool the flame flow in time at the position where the temperature rises most significantly.

[0029] Furthermore, the number of the cooling air inflow holes is at least 8, so that the flame flow can be cooled evenly.

[0030] Furthermore, the cross-sectional area of ​​the cooling air flow groove is more than 8 times the area of ​​the cooling air inlet hole, so that the cooling air flow rate and pressure flowing into each cooling air inlet hole are approximately the same, thereby improving the stability of the flame flow and preventing the powder beam to be sprayed from being blown off and causing adhesion to the combustion chamber.

[0031] Furthermore, by limiting the diameter of the i-th hole in the cooling gas inflow hole close to the cooling gas injection port, it is possible to ensure that the flow rate of each hole is equal.

[0032] The present invention also discloses a system of a high-speed, low-temperature spray gun containing a fuel premixing structure, which utilizes a heating module to heat a gas module to accelerate the flow rate of the gas and ensure the stability of ignition and combustion; utilizes a heating module to heat the high-speed, low-temperature spray gun to ensure that the gas ignition environment is maintained above 80°C, and ensures that the high-speed, low-temperature spray gun has stable ignition performance in the premixed state; during the operation of the high-speed, low-temperature spray gun, the fuel gas is heated to above 60°C to ensure stable combustion and enable the spray temperature to be adjusted over a wider range, thereby effectively inhibiting oxidation and decomposition of the powder to be sprayed during the spraying process. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A schematic diagram of the structure of a high-speed, low-temperature spray gun with a fuel premixing structure provided by the present invention;

[0034] Figure 2 A schematic diagram of the fuel premixing structure provided by the present invention;

[0035] Figure 3 A schematic diagram of the structure of the premixed common porous catalytic ceramic plate provided by the present invention;

[0036] Figure 4 This is a schematic structural diagram of the powder feeding needle provided by the present invention;

[0037] Figure 5 A schematic structural diagram of the powder feeding needle fixing device provided by the present invention;

[0038] Figure 6 A schematic structural diagram of the combustion chamber provided by the present invention;

[0039] Figure 7 for Figure 6 Sectional view of the AA plane;

[0040] Figure 8 It is a partial enlarged view of the cooling air flow groove;

[0041] Figure 9 Schematic diagram of the structure of the straight-through nozzle and straight-through nozzle sleeve, Laval nozzle and Laval nozzle sleeve provided by the present invention;

[0042] Figure 10 This is a structural schematic diagram of the spraying system of the high-speed low-temperature spray gun containing a fuel premixing structure provided by the present invention.

[0043] Among them: 1-nozzle sleeve; 2-nozzle; 3-fixing ring; 4-cooling gas distribution ring; 5-combustion chamber; 51-contraction section; 52-combustion section; 53-inlet section; 6-premixed common porous catalytic ceramic plate; 7-1-premixed front air distribution unit I; 7-2-premixed front air distribution unit II; 8-1-spray gun front shell; 8-2-premixed structure spray gun rear shell; 9-1-powder feeding needle; 9-2-powder feeding needle fixing device; 10-cooling gas flow groove; 11-cooling air flow inlet; 12-cooling gas injection port; 13-ignition port; 14-premixed interlayer. DETAILED DESCRIPTION

[0044] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0045] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0046] The present invention provides a high-speed low-temperature spray gun with a fuel premixing structure, such as Figure 1 As shown, it includes a powder feeding needle 9-1, a fuel premixing structure, a combustion chamber 5 and a nozzle 2. The powder feeding needle 9-1 is arranged in the fuel premixing structure, and the fuel premixing structure, the combustion chamber 5 and the nozzle 2 are connected in sequence from the powder feeding to the spraying direction.

[0047] The fuel premixing structure is used to provide an air passage and premix the incoming compressed air and fuel gas. Figure 2 As shown, from the powder feeding to the spraying direction, the fuel premixing structure includes pre-premixing air distribution unit I 7-1, pre-premixing air distribution unit II 7-2, and a common premixing porous catalytic ceramic plate 6. Pre-premixing air distribution unit I 7-1 and pre-premixing air distribution unit II 7-2 are mounted on the outside of the powder feeding needle 9-1. The powder feeding needle 9-1 coaxially passes through pre-premixing air distribution unit I 7-1, pre-premixing air distribution unit II 7-2, and the common premixing porous catalytic ceramic plate 6, and is connected to the combustion chamber 5. A premixing interlayer 14 is provided between pre-premixing air distribution unit II 7-2 and the common premixing porous catalytic ceramic plate 6. This interlayer 14 is used to premix compressed air and fuel gas. Pre-premixing air distribution unit I 7-1 contains a fuel gas channel and a powder feeding needle-compressed air channel. The powder feeding needle-compressed air channel is located outside the powder feeding needle 9-1 and is used to cool the powder feeding needle 9-1. The pre-premix air distribution unit Ⅰ7-1 is externally connected to the pre-mix structure spray gun rear shell 8-2. The rear end of the pre-mix structure spray gun rear shell 8-2 is provided with an air inlet and a gas inlet, and a curved compressed air channel is provided inside. One end of the curved compressed air channel is connected to the air inlet, and the other end is respectively connected to the powder feeding needle-compressed air channel, the pre-mixing interlayer 14, the outer wall of the combustion chamber 5 and the outer wall of the nozzle 2, wherein the outer wall of the combustion chamber 5 is connected to the compressed air channel of the outer wall of the nozzle 2. One end of the gas channel is connected to the gas inlet, and the other end is connected to the pre-mixing interlayer 14. Figure 3 As shown, a premixed common porous catalytic ceramic plate 6 is connected to the combustion chamber 5. A through hole I is provided at the center of the premixed common porous catalytic ceramic plate 6 for the passage of the sprayed powder. Surrounding through hole I are several through holes II for the passage of the premixed gas. The thickness h2 of the premixed common porous catalytic ceramic plate 6 is 70% to 95% of the distance h1 from the entrance of the premixed interlayer 14 to the exit of the premixed common porous catalytic ceramic plate 6. This distance ensures that the gas and compressed air are fully premixed within the premixed interlayer 14, maintaining flame stability. The premixed common porous catalytic ceramic plate 6 is preferably a silicon carbide ceramic plate.

[0048] The powder feeding needle 9-1 is used to feed the powder to be sprayed into the combustion chamber 5. Figure 4 and Figure 5 As shown, the end of the powder feed needle 9-1 is connected to a powder feed needle fixture 9-2, which can fix the powder feed needle 9-1 to the middle of the rear housing 8-2 of the premix spray gun. Both the powder feed needle 9-1 and the powder feed needle fixture 9-2 are provided with a powder-cooling gas channel for the powder to be sprayed and the cooling gas to pass through. The diameter of the powder-cooling gas channel is 0.2 to 0.6 times the diameter d2 of the gas channel (i.e., the fuel gas channel and the powder feed needle-compressed air channel), which can increase the speed at which the powder to be sprayed and the cooling gas enter the combustion chamber 5.

[0049] The combustion chamber 5 is used for the complete combustion of the powder to be sprayed. Figure 6 As shown, the combustion chamber 5 consists of a contraction section 51, a combustion section 52 and an inlet section 53. The contraction section 51 is connected to the nozzle 2, and the inlet section 53 is connected to the premixing common porous catalytic ceramic plate 6. The combustion chamber 5 is externally connected to the spray gun front housing 8-1, which is connected to the premixing structure spray gun rear housing 8-2. Figure 7 and Figure 8 As shown, a cooling gas distribution ring 4 is provided on the combustion section 52 body near the contraction section 51. A cooling gas injection port 12 and an ignition port 13 are provided on the combustion section 52 body opposite the cooling gas distribution ring 4. The distance l1 between the centerline of the cooling gas injection port 12 and the contraction section 51 is 1 / 10 to 1 / 5 of the length l2 of the combustion section 52. This distance ensures timely cooling of the flame flow at the point where the sprayed powder temperature rises most significantly. The ignition port 13 is connected to the spark plug. Cooling gas flow grooves 10 are provided on the combustion chamber 5 body and within the cooling gas distribution ring 4. Several cooling gas inlets 11 are provided in the cooling gas flow grooves 10. The cooling gas inlets 11 and the interior of the combustion chamber 5 are interconnected with the cooling gas injection ports 12. Preferably, the total number of cooling gas inlets 11 is 2n, where n ≥ 4. These 2n cooling gas inlets 11 are arranged around the cooling gas flow groove 10, symmetrically about the axis of the cooling gas injection port 12. The cross-sectional area S1 of the cooling gas flow groove 10 is more than 8 times the sum of the areas S2 of the cooling gas inlet openings 11. This arrangement can ensure that the cooling gas flow rate and pressure flowing into each cooling gas inlet 11 are approximately the same, thereby improving the stability of the flame flow and preventing the powder beam from being blown off and causing adhesion to the combustion chamber 5. The number of cooling gas inlets 11 on one side of the cooling gas injection port 12 is n, where n ≥ 4. The aperture of the i-th hole on the axial side of the cooling gas injection port 12 is the aperture of the first hole next to the axial side of the cooling gas injection port 12. It can ensure that the flow rate of each hole is equal.

[0050] Nozzle 2 is used to control the flow rate and speed of the powder to be sprayed. The nozzle 2 is externally connected to a matching nozzle sleeve 1. Preferably, the nozzle 2 is a straight nozzle or a Laval nozzle, and the corresponding nozzle sleeve 1 is a straight nozzle sleeve or a Laval nozzle sleeve. The design of the two sets of nozzles 2 and nozzle sleeve 1 can provide different process conditions and meet different spraying requirements. Figure 9 As shown, when conventional spraying process is adopted, straight-through nozzle and straight-through nozzle sleeve can be used in conjunction with each other ( Figure 9 A and B); When spraying materials that require higher powder flight speed, a Laval nozzle and a Laval nozzle sleeve with a contraction and expansion section can be used ( Figure 9 (C and D) The nozzle sleeve 1 is fixed to the front shell 8-1 of the spray gun via a fixing ring 3.

[0051] The working principle of the high-speed low-temperature spray gun with fuel premixing structure is as follows:

[0052] Compressed air is introduced into the air inlet of the rear housing 2 of the premix spray gun, while fuel gas is introduced into the fuel gas inlet. A portion of the compressed air enters the powder feed needle-compressed air channel through the compressed air channel, flows along the outer wall of the powder feed needle 9-1, and then passes through the premixed common porous catalytic ceramic plate 6 into the combustion chamber 5. During this process, the compressed air flows along the outer wall of the powder feed needle 9-1, preventing flashback and damage to the powder feed needle 9-1 during the spraying process. It also mixes with the powder feed cooling air upon entering the combustion chamber 5, reducing oxidation of the sprayed powder and preventing overheating. Another portion of the compressed air enters the premixed air distribution unit II 7-2 through the compressed air channel for secondary diversion. Part of the compressed air in the premixed air distribution unit II 7-2 flows out of the spray gun along the outer walls of the combustion chamber 5 and the nozzle 2, acting as a cooling circuit to prevent overheating. The remaining portion enters the premixed interlayer 14 to mix with the fuel gas. Simultaneously, the fuel gas from the fuel gas inlet enters the fuel gas channel within the premixed air distribution unit I 7-1, flows into the premixed interlayer 14, and mixes with the compressed air. At the same time, the powder to be sprayed and cooling air are introduced into the powder feeding inlet, and the cooling air feeds the powder to be sprayed into the combustion chamber 5 through the powder feeding needle 9-1 and the powder feeding fixing device 9-2.

[0053] Before the spraying powder, cooling gas, mixed fuel gas and compressed air enter the combustion chamber 5, a spark plug is connected through the ignition port 13 for ignition to heat the premixed common porous catalytic ceramic plate 6, and the premixed common porous catalytic ceramic plate 6 is heated to the gas ignition temperature.

[0054] After being thoroughly premixed in the premixing interlayer 14, the fuel gas and compressed air are preheated by the premixing common porous catalytic ceramic plate 6 before entering the combustion chamber 5, where they are ignited and continuously heat the powder to be sprayed, bringing it to a semi-molten state. Simultaneously, cooling gas is injected into the cooling gas injection port 12 and enters the combustion chamber 5 through the cooling air inlet 11 for cooling. This continuous flow of fuel gas, compressed air, and cooling gas heats the semi-molten powder particles, which are then ejected from the nozzle 2, achieving spraying.

[0055] The present invention provides a system comprising the high-speed low-temperature spray gun, such as Figure 10 As shown, it includes a control module, a gas module, a heating module, a powder feeding module and the aforementioned high-speed low-temperature spray gun.

[0056] The control cabinet module is used to control the gas pressure, the flow rate of the spray powder, and the position of the high-speed, low-temperature spray gun. The control cabinet module includes a control cabinet and a robotic arm connected by pipes. The control cabinet controls the position of the high-speed, low-temperature spray gun through the robotic arm.

[0057] The gas module supplies compressed air, cooling air, and fuel gas to the high-speed, low-temperature spray gun. The gas module contains fuel gas, cooling air, and compressed air. These gases are connected to the control cabinet module and the high-speed, low-temperature spray gun via pipelines. Under the control of the control cabinet module, compressed air, cooling air, or fuel gas are supplied to the high-speed, low-temperature spray gun. Cooling air is also connected to the powder delivery module via pipelines, which supply cooling air to the powder delivery module under the control of the control cabinet module.

[0058] The heating module is used to preheat the high-speed, low-temperature spray gun before ignition. The heating module includes a gas heater, which is connected to the control cabinet module, gas module, and high-speed, low-temperature spray gun through pipelines.

[0059] The powder feeding module is used to deliver powder to the high-speed, low-temperature spray gun. It includes a powder feeder, which is connected to the control cabinet module, gas module, and high-speed, low-temperature spray gun via pipelines.

[0060] The working principle of the above system including the high-speed low-temperature spray gun is as follows:

[0061] Under the parameter control of the control cabinet, compressed air, cooling gas and fuel gas are respectively input into the air inlet, cooling gas injection port 12 and fuel gas inlet of the high-speed low-temperature spray gun, and the cooling gas and the powder to be sprayed in the powder feeder are fed into the powder feeding inlet of the high-speed low-temperature spray gun. The fuel gas is heated by the gas heater, and the position of the high-speed low-temperature spray gun is adjusted by the movement of the robotic arm to impact the surface of the substrate to form a coating.

[0062] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0063] Example 1

[0064] A high-speed, low-temperature spray gun with a fuel premixing structure comprises a powder feeding needle 9-1, a fuel premixing structure, a combustion chamber 5 and a Laval nozzle, wherein the Laval nozzle is externally connected to a Laval nozzle sleeve.

[0065] The fuel premixing structure, from powder delivery to spraying, consists of premixing air distribution unit I 7-1, premixing air distribution unit II 7-2, and a silicon carbide ceramic plate. These units are mounted on the exterior of a powder feed needle 9-1, made of 304 stainless steel. The powder feed needle 9-1 coaxially passes through these units, each of which is connected to the combustion chamber 5. Both premixing air distribution units I 7-1 and II 7-2 are made of 6061 aluminum alloy. A premixing interlayer 14 is provided between premixing air distribution unit II 7-2 and the silicon carbide ceramic plate. Premixing air distribution unit I 7-1 houses a propane channel and a powder feed needle-compressed air channel. It is externally connected to the premixing spray gun rear housing 8-2, made of 6061 aluminum alloy. The rear housing 8-2 of the premix spray gun features an air inlet and a propane inlet at its distal end. A curved compressed air channel is located within the housing. One end of the compressed air channel connects to the air inlet, while the other connects to the powder needle-compressed air channel, the premix interlayer 14, the outer wall of the combustion chamber 5, and the outer wall of the nozzle 2. One end of the propane channel connects to the propane inlet, while the other connects to the premix interlayer 14. A silicon carbide ceramic plate connects to the combustion chamber 5. A through-hole I is defined at the center of the plate for the spray powder to pass through. Several through-holes II are located around through-hole I. The plate has a thickness h2 of 8.5 mm, and the outlet is 10 mm from h1.

[0066] The end of the powder feeding needle 9-1 is connected to the powder feeding needle fixing device 9-2. Powder-nitrogen channels are opened inside the powder feeding needle 9-1 and the powder feeding needle fixing device 9-2. The diameter of the powder-nitrogen channel is 4mm, and the diameters of the propane channel and the powder feeding needle-compressed air channel are both 7mm.

[0067] The combustion chamber 5, made of 304 stainless steel, consists of a contraction section 51, a combustion section 52, and an inlet section 53. The contraction section 51 is connected to the nozzle 2, and the inlet section 53 is connected to the silicon carbide ceramic plate. The combustion chamber 5 is externally connected to a spray gun front housing 8-1 made of aluminum alloy 6061. The spray gun front housing 8-1 is connected to the premixed structure spray gun rear housing 8-2. The spray gun front housing 8-1 is fixed to the Laval nozzle sleeve via a fixing ring 3. A cooling nitrogen distribution ring is provided on the side of the combustion section 52 body near the contraction section 51. A cooling nitrogen injection port and an ignition port 13 are provided on the combustion section 52 body opposite the cooling nitrogen distribution ring. The length l1 of the cooling nitrogen injection port from the centerline of the contraction section 51 is 4 mm, and the length of the combustion section 52 is 36 mm. The ignition port 13 is connected to a spark plug. The combustion chamber 5 body and the cooling nitrogen distribution ring are both provided with cooling nitrogen flow grooves. The cooling nitrogen flow grooves are symmetrical with the axis of the cooling nitrogen injection port. There are 8 cooling nitrogen flow inlets around the circle. The cooling nitrogen flow inlets, the interior of the combustion chamber 5 and the cooling nitrogen injection port are connected. The cross-sectional area of ​​the cooling nitrogen flow groove is 36mm 2 The number of cooling nitrogen gas inlets on one side of the cooling nitrogen gas injection port is 6, and the apertures of the cooling nitrogen gas inlets are 1 mm, 1.03 mm, 1.07 mm, 1.12 mm, 1.19 mm and 1.24 mm respectively.

[0068] The high-speed low-temperature spray gun comprises two sets of nozzles 2 and nozzle sleeves 1, namely a straight nozzle and a straight nozzle sleeve, and a Laval nozzle and a Laval nozzle sleeve. The nozzle sleeve 1 is fixed to the front shell 8-1 of the spray gun via a fixing ring 3.

[0069] A system incorporating the aforementioned high-speed, low-temperature spray gun comprises a control cabinet, a robotic arm, compressed air, cooling nitrogen, liquefied propane, a propane heater, a powder feeder, and the high-speed, low-temperature spray gun. The robotic arm, compressed air, cooling nitrogen, liquefied propane, propane heater, and powder feeder are respectively connected to the control cabinet and the high-speed, low-temperature spray gun. The cooling nitrogen is connected to the powder feeder. Each gas channel in the control cabinet is connected to a solenoid valve and a proportional valve to adjust gas pressure parameters. This circuit connects a high-voltage transformer to a spark plug for ignition. Furthermore, a gas detection system is installed within the control cabinet. The control cabinet controls parameters to input compressed air into the air inlet and cooling nitrogen into the nitrogen inlet of the high-speed, low-temperature spray gun. The propane heater heats the liquefied propane, vaporizing it to approximately 40°C. Propane is then input into the propane inlet. The cooling nitrogen and the powder to be sprayed in the powder feeder are then fed into the powder feed inlet of the high-speed, low-temperature spray gun. The position of the high-speed, low-temperature spray gun is adjusted by the movement of the robotic arm, and the powder impinges on the substrate surface, forming a coating.

[0070] The test was conducted using the system including the high-speed low-temperature spray gun:

[0071] 1. Without injecting cooling nitrogen, when only igniting the test gun without feeding powder, the temperature at 50mm from the Laval nozzle outlet was measured to be 1381.2℃, and the temperature at 93.5mm from the high-speed low-temperature spray gun outlet was 1100℃, and the high-speed low-temperature flame could burn continuously and stably.

[0072] 2. Without nitrogen cooling, a system including the aforementioned high-speed, low-temperature spray gun was used to deposit TC4 powder with a particle size of 15 to 53 μm onto a TC4 substrate. The deposition parameters were: propane pressure of 0.448 MPa, compressed air of 0.489 MPa, powder feed air flow of 25 L / min, spray distance of 200 mm, spray gun travel speed of 800 mm / s, coating thickness of 200 μm, and propane heater preheat temperature of 38°C. The coatings achieved an average porosity of 1.218%, an average hardness of 247.13 HV, and a bond strength of 50.65 MPa.

[0073] Example 2

[0074] A high-speed, low-temperature spray gun with a fuel premixing structure comprises a powder feeding needle 9-1, a fuel premixing structure, a combustion chamber 5 and a straight-through nozzle, wherein the straight-through nozzle is externally connected to a straight-through nozzle sleeve.

[0075] The fuel premixing structure, from powder delivery to spraying, consists of premixing air distribution unit I 7-1, premixing air distribution unit II 7-2, and a silicon carbide ceramic plate. These units are mounted on the exterior of a powder feed needle 9-1, made of 304 stainless steel. The powder feed needle 9-1 coaxially passes through these units, each of which is connected to the combustion chamber 5. Both premixing air distribution units I 7-1 and II 7-2 are made of 6061 aluminum alloy. A premixing interlayer 14 is provided between premixing air distribution unit II 7-2 and the silicon carbide ceramic plate. Premixing air distribution unit I 7-1 houses a propane channel and a powder feed needle-compressed air channel. It is externally connected to the premixing spray gun rear housing 8-2, made of 6061 aluminum alloy. The rear housing 8-2 of the premix spray gun features an air inlet and a propane inlet at its distal end. A curved compressed air channel is located within the housing. One end of the compressed air channel connects to the air inlet, while the other connects to the powder feed needle-compressed air channel, the premix interlayer 14, the outer wall of the combustion chamber 5, and the outer wall of the nozzle 2. One end of the propane channel connects to the propane inlet, while the other connects to the premix interlayer 14. A silicon carbide ceramic plate connects to the combustion chamber 5. A through-hole I is defined at the center of the plate for the spray powder to pass through. Several through-holes II are located around through-hole I. The plate has a thickness h2 of 9 mm, and the outlet is 10 mm from h1.

[0076] The end of the powder feeding needle 9-1 is connected to the powder feeding needle fixing device 9-2. Powder-nitrogen channels are opened inside the powder feeding needle 9-1 and the powder feeding needle fixing device 9-2. The diameter of the powder-nitrogen channel is 4mm, and the diameters of the propane channel and the powder feeding needle-compressed air channel are both 10mm.

[0077] The combustion chamber 5, made of 304 stainless steel, consists of a contraction section 51, a combustion section 52, and an inlet section 53. The contraction section 51 is connected to the nozzle 2, and the inlet section 53 is connected to the silicon carbide ceramic plate. The combustion chamber 5 is externally connected to a spray gun front housing 8-1 made of aluminum alloy 6061. The spray gun front housing 8-1 is connected to the premixing structure spray gun rear housing 8-2. The spray gun front housing 8-1 is fixed to the straight-through nozzle sleeve via a retaining ring 3. A cooling nitrogen distribution ring is provided on the side of the combustion section 52 body near the contraction section 51. A cooling nitrogen injection port and an ignition port 13 are provided on the combustion section 52 body opposite the cooling nitrogen distribution ring. The centerline of the cooling nitrogen injection port is 6 mm from the contraction section 51, and the length of the combustion section 52 is 36 mm. The ignition port 13 is connected to a spark plug. The combustion chamber 5 body and the cooling nitrogen distribution ring are both provided with cooling nitrogen flow grooves. The cooling nitrogen flow grooves are symmetrical with the cooling nitrogen injection port as the axis. There are 10 cooling nitrogen flow inlets around the circle. The cooling nitrogen flow inlets, the combustion chamber 5 interior and the cooling nitrogen injection port are connected. The cross-sectional area of ​​the cooling nitrogen flow groove is 36mm 2 The number of cooling nitrogen gas inlets on one side of the cooling nitrogen gas injection port is 5, and the apertures of the cooling nitrogen gas inlets are 1 mm, 1.03 mm, 1.07 mm, 1.12 mm, and 1.19 mm, respectively.

[0078] The high-speed low-temperature spray gun comprises two sets of nozzles 2 and nozzle sleeves 1, namely a straight nozzle and a straight nozzle sleeve, and a Laval nozzle and a Laval nozzle sleeve. The nozzle sleeve 1 is fixed to the front shell 8-1 of the spray gun via a fixing ring 3.

[0079] A system incorporating the aforementioned high-speed, low-temperature spray gun comprises a control cabinet, a robotic arm, compressed air, cooling nitrogen, liquefied propane, a propane heater, a powder feeder, and the high-speed, low-temperature spray gun. The robotic arm, compressed air, cooling nitrogen, liquefied propane, propane heater, and powder feeder are respectively connected to the control cabinet and the high-speed, low-temperature spray gun. The cooling nitrogen is connected to the powder feeder. Each gas channel in the control cabinet is connected to a solenoid valve and a proportional valve to adjust gas pressure parameters. This circuit connects a high-voltage transformer to a spark plug for ignition. Furthermore, a gas detection system is installed within the control cabinet. The control cabinet controls parameters to input compressed air into the air inlet and cooling nitrogen into the nitrogen inlet of the high-speed, low-temperature spray gun. The propane heater heats the liquefied propane, vaporizing it to approximately 40°C. Propane is then input into the propane inlet. The cooling nitrogen and the powder to be sprayed in the powder feeder are then fed into the powder feed inlet of the high-speed, low-temperature spray gun. The position of the high-speed, low-temperature spray gun is adjusted by the movement of the robotic arm, and the powder impinges on the substrate surface, forming a coating.

[0080] The test was conducted using the system including the high-speed low-temperature spray gun:

[0081] 1. When the gun is ignited without injecting cooling nitrogen and without feeding powder, the temperature at 80mm from the outlet of the straight-through nozzle is measured to be 1350.5℃, and the high-speed and low-temperature flame can burn continuously and stably.

[0082] 2. Without the injection of cooling nitrogen, a system including the aforementioned high-speed, low-temperature spray gun was used to deposit nickel-based 718 powder with a particle size of 15-45 μm onto a TC4 substrate. The deposition parameters were: propane pressure of 0.462 MPa, compressed air of 0.496 MPa, cooling nitrogen of 0.300 MPa, powder feed gas flow of 25 L / min, spray distance of 170 mm, spray gun travel speed of 800 mm / s, coating thickness of 200 μm, and propane heater preheat temperature of 37.5°C. The average porosity of the coating was measured to be 1.349%, and the average hardness of the coating was 453.8 HV.

[0083] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A high-speed, low-temperature spray gun with a fuel premixing structure, characterized in that: The invention comprises a powder feeding needle (9-1), wherein the outer portion of the powder feeding needle (9-1) is provided with a pre-mixing air distribution unit I (7-1) and a pre-mixing air distribution unit II (7-2), a pre-mixing common porous catalytic ceramic plate (6) is provided in the combustion chamber (5), the end portion of the powder feeding needle (9-1) penetrates the pre-mixing common porous catalytic ceramic plate (6) and is in communication with the combustion chamber (5), and a pre-mixing interlayer (14) is provided between the pre-mixing air distribution unit II (7-2) and the pre-mixing common porous catalytic ceramic plate (6); A gas channel and a powder feeding needle-compressed air channel are provided inside the pre-premixing air distribution unit I (7-1), and the powder feeding needle-compressed air channel is arranged outside the powder feeding needle (9-1); an air inlet and a gas inlet are provided at the end of the spray gun shell, and a compressed air channel is provided inside, one end of the compressed air channel is connected to the air inlet, and the other end is respectively connected to the powder feeding needle-compressed air channel, the premixing interlayer (14), the outer wall of the combustion chamber (5) and the outer wall of the nozzle (2); one end of the gas channel is connected to the gas inlet, and the other end is connected to the premixing interlayer (14).

2. A high-speed, low-temperature spray gun with a fuel premixing structure according to claim 1, characterized in that: The premixed common porous catalytic ceramic plate (6) is provided with a plurality of through holes II for the premixed gas to pass through.

3. A high-speed, low-temperature spray gun with a fuel premixing structure according to claim 2, characterized in that: The thickness of the premixed common porous catalytic ceramic plate (6) is 70% to 95% of the distance from the inlet of the premixed interlayer (14) to the outlet of the premixed common porous catalytic ceramic plate (6).

4. The high-speed, low-temperature spray gun with a fuel premixing structure according to claim 1, characterized in that: The nozzle (2) is externally connected to a matching nozzle sleeve (1).

5. A high-speed, low-temperature spray gun with a fuel premixing structure according to claim 4, characterized in that: The nozzle (2) is a straight nozzle or a Laval nozzle, and the corresponding nozzle sleeve (1) is a straight nozzle sleeve or a Laval nozzle sleeve.

6. The high-speed, low-temperature spray gun with a fuel premixing structure according to claim 1, characterized in that: The end of the powder feeding needle (9-1) is connected to a powder feeding needle fixing device (9-2). The powder feeding needle (9-1) and the powder feeding needle fixing device (9-2) are both fixed to the middle of the rear section of the spray gun housing, and both have a powder-cooling gas channel for the powder to be sprayed and the cooling gas to pass through.

7. A high-speed, low-temperature spray gun with a fuel premixing structure according to any one of claims 1 to 6, characterized in that: The combustion chamber (5) is composed of a contraction section (51), a combustion section (52) and an inlet section (53). The contraction section (51) is connected to the nozzle (2), and the inlet section (53) is connected to the premixed common porous catalytic ceramic plate (6). A cooling gas distribution ring (4) is provided on the combustion section (52) body on the side close to the contraction section (51). A cooling gas injection port (12) and an ignition port (13) are provided on the combustion section (52) body on the opposite side of the cooling gas distribution ring (4).

8. The high-speed, low-temperature spray gun with a fuel premixing structure according to claim 7, characterized in that: The length l1 of the center line of the cooling gas injection port (12) from the contraction section (51) is 1 / 10 to 1 / 5 of the length l2 of the combustion section (52).

9. The high-speed, low-temperature spray gun with a fuel premixing structure according to claim 7, characterized in that: A cooling gas flow groove (10) is provided on the combustion chamber (5) body and inside the cooling gas distribution ring (4). A plurality of cooling gas flow inlets (11) are provided on the cooling gas flow groove (10). The cooling gas flow inlets (11), the interior of the combustion chamber (5) and the cooling gas injection port (12) are connected.

10. A system comprising the high-speed low-temperature spray gun according to any one of claims 1 to 9, characterized in that: It includes a control module, a gas module, a heating module, a powder feeding module and the high-speed low-temperature spray gun according to any one of claims 1 to 9, the control module and the high-speed low-temperature spray gun are respectively connected to the gas module, the heating module and the powder feeding module, and the gas module is respectively connected to the heating module and the powder feeding module.

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