A high-speed low-temperature spray gun for cooling the flame flow in the combustion chamber and its system

Abstract

The invention belongs to the field of material surface modification and coating technology, and discloses a high-speed low-temperature spray gun and a system thereof for cooling a flame flow in a combustion chamber, including a combustion chamber, the combustion chamber is composed of a contraction section, a combustion section and an inlet section, the contraction section is connected to a nozzle, a porous catalytic ceramic plate, a gas distribution unit, and a spray gun tail seat are arranged in sequence at the inlet section, a spray gun housing is arranged outside the combustion chamber, a nozzle housing is arranged outside the nozzle, a powder delivery needle is arranged in the middle of the spray gun tail seat, the spray gun tail seat is provided with a curved compressed air channel and is connected to the gas distribution unit, a cooling gas distribution ring is arranged on one side of the combustion section close to the contraction section, an ignition port is arranged on the other side, and a gas channel is arranged in sequence through a porous catalytic ceramic plate, a gas distribution unit, and the middle of the spray gun tail seat and connected to a gas interface. The spray gun of the present invention reduces the spraying temperature, thereby effectively inhibiting oxidation and decomposition of particles during the spraying process.

Description

Technical Field

[0001] The invention belongs to the technical field of material surface modification and coating, and in particular relates to a high-speed low-temperature spraying gun for cooling a flame flow in a combustion chamber and a system thereof. Background Art

[0002] Supersonic flame spraying is a new type of thermal spraying technology developed in the early 1980s on the basis of ordinary flame spraying. It uses hydrogen, acetylene, propylene, kerosene and other fuels, oxygen or compressed air as combustion aids, and burns in a combustion chamber or a special nozzle to produce a supersonic flame flow with a temperature of more than 2000°C and a speed higher than the speed of sound, thereby sending the powder into the flame to heat it into molten or semi-molten particles, and then colliding at high speed on the surface of the substrate to form a high-strength and high-density coating. The coating produced by supersonic flame spraying technology has the characteristics of high bonding strength and dense structure, which provides more options for coating preparation and component maintenance, etc. However, due to the high temperature of the flame flow, such as WC-CO, Ti and other particles, it is easy to cause a large degree of oxidation and decomposition, which limits the use of supersonic flame spraying technology on these powder coatings.

[0003] At present, the art usually installs a mixing chamber outside the combustion chamber of the supersonic flame spray gun and injects cooling gas into the mixing chamber to reduce the temperature of the flame flow; or axially feeds cooling gas to cool the flame flow at the inlet of the combustion chamber. These two methods can reduce the spraying temperature to a certain extent, but for axial powder feeding, the former particles will overheat in the high temperature combustion chamber and cannot effectively inhibit the oxidation and decomposition of the particles; while the latter has a narrow adjustment range without affecting combustion, and the temperature control range is limited, and the degree of oxidation inhibition for easily oxidized particles is limited. Summary of the invention

[0004] 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 for cooling the flame flow in the combustion chamber, thereby solving the problem that the axial powder feeding in the prior art cannot effectively inhibit the oxidation of particles.

[0005] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme to achieve it: a high-speed low-temperature spray gun for cooling the flame flow in the combustion chamber, including a combustion chamber, the combustion chamber is composed of a contraction section, a combustion section and an inlet section, the contraction section is connected to the nozzle, and a porous catalytic ceramic plate, a gas distribution unit, and a spray gun tail seat are arranged in sequence at the inlet section, a spray gun housing is arranged outside the combustion chamber, a nozzle housing is arranged outside the nozzle, a powder feeding needle is arranged in the middle of the spray gun tail seat, a curved compressed air channel is provided on the spray gun tail seat and is connected to the gas distribution unit, a cooling gas distribution ring is provided on one side of the combustion section close to the contraction section, and an ignition port is provided on the other side, and a gas channel is sequentially penetrated through the porous catalytic ceramic plate, the gas distribution unit, the spray gun tail seat and connected to the gas interface.

[0006] Preferably, cooling gas flow grooves are provided in the cooling gas distribution ring and the combustion chamber, the cooling gas flow grooves are connected to the cooling gas injection port, and the cooling gas injection port and the ignition port are located on the same horizontal line.

[0007] Preferably, the cooling gas distribution ring is provided with a plurality of cooling gas inlet holes, and the cooling gas inlet holes are penetrated through the cooling gas flow groove and communicated with the combustion chamber.

[0008] Preferably, the plurality of cooling gas inlet holes are arranged around the cooling gas distribution ring, and the plurality of cooling gas inlet holes take the axial direction where the cooling gas injection port is located as the symmetry axis.

[0009] Preferably, the number of the cooling air inlet holes is 2n, the number of the cooling air inlet holes on one side of the cooling air injection port is n, and n≥4.

[0010] 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. .

[0011] Preferably, the cross-sectional area of ​​the cooling air flow groove is S 1 is the cooling air inlet opening area S More than 8 times the sum of 2.

[0012] Preferably, the distance between the center line of the cooling gas injection port and the contraction section is l 1 is the length of the combustion section l 1 / 10~1 / 5 of 2.

[0013] Preferably, the gas channel has a cross-section contraction at the inlet section, and the gas channel has an aperture of d 1 is the diameter of the gas channel in the tailstock of the spray gun d 0.2-0.6 times of 2.

[0014] The present invention also discloses a spraying system of a high-speed low-temperature spraying gun for cooling the flame flow in a combustion chamber, comprising:

[0015] The gas module is used to deliver compressed air, cooling gas and fuel gas to the spray gun, including an air compressor connected to a gas storage tank and a dryer in sequence, the dryer connected to a control cabinet module and a gas heater in sequence through pipelines, a cooling gas bottle connected to a control cabinet module and a spray gun in sequence through pipelines, a fuel gas bottle and a vaporizer connected to a control cabinet module and a gas heater in sequence through pipelines, and the gas heater connected to the spray gun;

[0016] The powder feeding module is used to feed powder to the spray gun, including a powder feeding gas bottle connected to the control cabinet module through a pipeline, and the control cabinet module is connected to the powder feeder and the spray gun in sequence through pipelines;

[0017] The control cabinet module is used to control the flow of gas and powder;

[0018] The spray gun heating module is used for preheating a high-speed low-temperature spray gun which cools the flame flow in the combustion chamber before ignition.

[0019] Compared with the prior art, the present invention has the following beneficial effects: the present invention discloses a high-speed low-temperature spray gun for cooling the flame flow in the combustion chamber. The spray powder is heated most seriously in the combustion section near the contraction section. A cooling gas distribution ring needs to be set here for cooling. The cooling gas distribution ring radially delivers the cooling gas into the combustion chamber so that the particles can be cooled in time at the place where the temperature rises significantly. The curved compressed air channel can destroy the laminar flow state, and the flow rate of the compressed air in the curved compressed air channel is more uniform. The spray gun adopts a non-premixing method, forming a form in which the fuel gas is not fully mixed and burned in the inlet section and fully burned in the combustion section; thereby ensuring that the speed and flame flow temperature of the particles are low when they just enter the combustion chamber, so as not to cause excessive temperature rise; the flame flow temperature in the combustion section is high, but the particle speed has also been improved. At the same time, due to the addition of cooling gas, the temperature of a large area near the particle surface is avoided to rise significantly, thereby inhibiting the oxidation and decomposition of the particles. The spray gun of the present invention reduces the spraying temperature by 1000°C, realizes the regulation of the spraying temperature in a relatively large range, and reduces the temperature of the particles to below 750°C, thereby effectively inhibiting the oxidation and decomposition of the particles during the spraying process.

[0020] Furthermore, the number of the cooling air inflow holes is at least 8, so that the flame flow can be cooled evenly.

[0021] 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 ensured that the flow rate of each hole is equal.

[0022] Furthermore, the cross-sectional area of ​​the cooling gas flow groove is more than 8 times the area of ​​the cooling gas inlet hole, so that the cooling gas flow rate and pressure flowing into each cooling gas inlet hole 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.

[0023] Furthermore, the distance between the center line of the cooling gas injection port and the contraction section is l 1 is the length of the combustion section l The distance is 1 / 10 to 1 / 5 of 2, and the powder is able to cool the flame flow in time at the position where the temperature rises most significantly.

[0024] Furthermore, the gas channel has an aperture of d 1 is the diameter of the gas channel in the gas distribution unit d 2 is 0.2-0.6 times of 2, which can increase the speed of the gas entering the combustion chamber.

[0025] The present invention also discloses a high-speed, low-temperature spraying system for cooling the flame flow in a combustion chamber. A gas heater is used to heat the fuel gas and compressed air, so that the flow rate of the gas is accelerated, thereby ensuring the stability of ignition and combustion. A heating sleeve is used to heat the spray gun to ensure that the gas ignition environment is maintained above 80°C, thereby ensuring that the spray gun still has good ignition performance in the non-premixed state. During the operation of the spray gun, the compressed air is heated to above 60°C, thereby ensuring stable combustion and achieving a wide range of spray temperature adjustment. The temperature of the particles is reduced to below 750°C, thereby effectively inhibiting oxidation and decomposition of the particles during the spraying process. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A structural diagram of a high-speed low-temperature spray gun for cooling the flame flow in a combustion chamber provided by the present invention;

[0027] Figure 2 A schematic diagram of the structure of the combustion chamber provided by the present invention;

[0028] Figure 3 It is a partial enlarged view of the cooling air flow groove;

[0029] Figure 4 for Figure 2 AA surface section view;

[0030] Figure 5 A schematic diagram of the structure of a high-speed low-temperature spraying system for cooling the flame flow in a combustion chamber provided by the present invention;

[0031] Among them: 1-nozzle housing; 2-nozzle; 3-spray gun housing; 4-cooling gas distribution ring; 5-combustion chamber; 51-contraction section; 52-combustion section; 53-inlet section; 6-porous catalytic ceramic plate; 7-gas distribution unit; 8-spray gun tail seat; 9-powder delivery needle; 10-cooling gas flow groove; 11-cooling gas inflow hole; 12-cooling gas injection port; 13-ignition port; 14-air compressor; 15-gas storage tank; 16-dryer; 17-cooling gas bottle; 18-gas bottle; 19-vaporizer; 20-control cabinet; 21-powder feeder; 22-gas heater; 23-powder carrier gas bottle; 24-heating sleeve; 25-spray gun. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme 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 described embodiments 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 creative work should fall within the scope of protection of the present invention.

[0033] It should be noted that the terms "first", "second", etc. in the specification 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 data 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 that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0034] Example 1

[0035] A high-speed, low-temperature spray gun that cools the flame flow in the combustion chamber, see Figure 1 and Figure 2 , including a combustion chamber 5, 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 a porous catalytic ceramic plate 6, a gas distribution unit 7 and a spray gun tail seat 8 are arranged in sequence at the inlet section 53, a spray gun housing 3 is arranged outside the combustion chamber 5, a nozzle housing 1 is arranged outside the nozzle 2, a powder feeding needle 9 is arranged in the middle of the spray gun tail seat 8, the spray gun tail seat 8 is provided with a curved compressed air channel and is connected to the gas distribution unit 7, a cooling gas distribution ring 4 is arranged on one side of the combustion section 52 close to the contraction section 51, and an ignition port 13 is arranged on the other side, and the gas channel is sequentially penetrated through the porous catalytic ceramic plate 6, the gas distribution unit 7, and the middle of the spray gun tail seat 8 and is connected to the gas interface.

[0036] See also Figure 4 , multiple cooling air inflow holes 11 are symmetrically arranged with the radial direction of the cooling air injection port 12, and 10 cooling air inflow holes 11 are evenly opened on both sides of the cooling air injection port 12, and cooling air flows into the combustion chamber 5. The apertures of the five small holes on both sides of the cooling air injection port 12 are 1 mm, 1.02 mm, 1.17 mm, 1.31 mm, and 1.58 mm respectively; the length of the combustion section 52 is 36 mm, and the length of the center line of the cooling air injection port 12 from one side of the contraction section 51 is 6 mm, see Figure 3 The cross-sectional area of ​​the cooling air flow channel 10 is 32 mm 2 .

[0037] The gas channel and the curved compressed air channel are used to independently deliver the gas and the compressed air into the combustion chamber 5 without premixing. The gas channel has a cross-sectional contraction at the inlet section 53 to increase the gas flow rate. The cross-sectional aperture of the gas channel at the inlet section 53 is d 1 is 4 mm, the gas channel is in the tailstock of the spray gun 8 inner diameterd 2 is 7 mm.

[0038] Without injecting cooling gas, a deposition test was carried out using Ti powder with a particle size of 15-45 μm. The temperature at the spray gun outlet was measured to be 2000 °C, the average temperature of the particles measured using the DPV-2000 thermal spray online monitor was 1550 °C, and the oxygen content of the coating was measured to be 9.8 at.%.

[0039] A high-speed low-temperature spray system for cooling the flame flow in the combustion chamber is ignited after preheating the gas and the spray gun in the manner used in Example 1, such as Figure 5 As shown in FIG. 1 , after the combustion is stabilized, the cooling gas is injected into the combustion chamber 5 in the form of linearly increasing flow rate to cool the flame flow; during the spraying process, the cooling gas flow rate is set to 0.5 mm 3 / min.

[0040] The gas module is used to deliver compressed air, cooling gas and fuel gas to the spray gun, including an air compressor 14 connected to a gas storage tank 15 and a dryer 16 in sequence, the dryer 16 is connected to a control cabinet module and a gas heater 22 in sequence through pipelines, a cooling gas bottle 17 is connected to a control cabinet module and a spray gun in sequence through pipelines, a fuel gas bottle 18 and a vaporizer 19 are connected to a control cabinet module and a gas heater 22 in sequence through pipelines, and the gas heater 22 is connected to a spray gun 25;

[0041] The powder feeding module is used to feed powder to the spray gun, including a powder feeding gas bottle 23 connected to the control cabinet module through a pipeline, and the control cabinet module is connected to the powder feeder 21 and the spray gun in sequence through pipelines;

[0042] The control cabinet module is used to control the flow of gas and powder, and includes a control cabinet 20;

[0043] The spray gun heating module is used for preheating a high-speed low-temperature spray gun for cooling the flame flow in the combustion chamber before ignition, and comprises a spray gun 25, and a heating jacket 24 is arranged outside the spray gun 25.

[0044] The deposition test was carried out using Ti powder with a particle size of 15-45 μm. The temperature at the spray gun outlet was measured to be 1600°C. The average temperature of the particles measured using the DPV-2000 thermal spray online monitor was 1325°C. The oxygen content of the coating was measured to be 6.4 at.%.

[0045] Example 2

[0046] A high-speed, low-temperature spray gun that cools the flame flow in the combustion chamber, see Figure 1 and Figure 2, including a combustion chamber 5, 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 a porous catalytic ceramic plate 6, a gas distribution unit 7 and a spray gun tail seat 8 are arranged in sequence at the inlet section 53, a spray gun housing 3 is arranged outside the combustion chamber 5, a nozzle housing 1 is arranged outside the nozzle 2, a powder feeding needle 9 is arranged in the middle of the spray gun tail seat 8, the spray gun tail seat 8 is provided with a curved compressed air channel and is connected to the gas distribution unit 7, a cooling gas distribution ring 4 is arranged on one side of the combustion section 52 close to the contraction section 51, and an ignition port 13 is arranged on the other side, and the gas channel is sequentially penetrated through the porous catalytic ceramic plate 6, the gas distribution unit 7, and the middle of the spray gun tail seat 8 and is connected to the gas interface.

[0047] See also Figure 4 , multiple cooling air inflow holes 11 are symmetrically arranged with the radial direction of the cooling air injection port 12, 16 cooling air inflow holes 11 are evenly opened on both sides of the cooling air injection port 12, and cooling air enters the combustion chamber 5. The apertures of the 8 small holes on both sides of the cooling air injection port 12 are 1 mm, 1.03 mm, 1.07 mm, 1.12 mm, 1.19 mm, 1.24 mm, 1.35 mm, and 1.58 mm respectively; the length of the combustion section 52 is 36 mm, the length of the center line of the cooling air injection port 12 from one side of the contraction section 51 is 4 mm, and the cross-sectional area of ​​the cooling air flow groove 10 is 36 mm 2 , see Figure 3 .

[0048] The gas channel and the curved compressed air channel are used to independently deliver the gas and the compressed air into the combustion chamber 5 without premixing. The gas channel has a cross-sectional contraction at the inlet section 53 to increase the gas flow rate. The cross-sectional aperture of the gas channel at the inlet section 53 is d 1 is 4 mm, the gas channel is in the tailstock of the spray gun 8 inner diameter d 2 is 10 mm.

[0049] A high-speed low-temperature spray system for cooling the flame flow in the combustion chamber ignites after preheating the gas and the spray gun, such as Figure 5 As shown in FIG. 1 , after the combustion is stabilized, the cooling gas is injected into the combustion chamber 5 in the form of a linear increase in flow rate to cool the flame flow; during the spraying process, the cooling gas flow rate is set to 1 mm 3 / min.

[0050] The deposition test was carried out using Ti powder with a particle size of 15-45 μm. The temperature at the spray gun outlet was measured to be 1320 ℃. The average temperature of the particles measured using the DPV-2000 thermal spray online monitor was 1045 ℃. The oxygen content of the coating was measured to be 1.2 at.%.

[0051] Example 3

[0052] A high-speed, low-temperature spray gun that cools the flame flow in the combustion chamber, see Figure 1 and Figure 2 , including a combustion chamber 5, 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 a porous catalytic ceramic plate 6, a gas distribution unit 7 and a spray gun tail seat 8 are arranged in sequence at the inlet section 53, a spray gun housing 3 is arranged outside the combustion chamber 5, a nozzle housing 1 is arranged outside the nozzle 2, a powder feeding needle 9 is arranged in the middle of the spray gun tail seat 8, the spray gun tail seat 8 is provided with a curved compressed air channel and is connected to the gas distribution unit 7, a cooling gas distribution ring 4 is arranged on one side of the combustion section 52 close to the contraction section 51, and an ignition port 13 is arranged on the other side, and the gas channel is sequentially penetrated through the porous catalytic ceramic plate 6, the gas distribution unit 7, and the middle of the spray gun tail seat 8 and is connected to the gas interface.

[0053] See also Figure 4 , multiple cooling air inflow holes 11 are symmetrically arranged with the radial direction of the cooling air injection port 12, 20 cooling air inflow holes 11 are evenly opened on both sides of the cooling air injection port 12, and cooling air enters the combustion chamber 5. The apertures of the 10 small holes on both sides of the cooling air injection port 12 are 1 mm, 1.02 mm, 1.05 mm, 1.09 mm, 1.13 mm, 1.19 mm, 1.25 mm, 1.33 mm, 1.44 mm, and 1.58 mm respectively; the length of the combustion section 52 is 36 mm, the length of the center line of the cooling air injection port 12 from one side of the contraction section 51 is 8 mm, and the cross-sectional area of ​​the cooling air flow groove 10 is 48 mm 2 , see Figure 3 .

[0054] The gas channel and the curved compressed air channel are used to independently deliver the gas and the compressed air into the combustion chamber 5 without premixing. The gas channel has a cross-sectional contraction at the inlet section 53 to increase the gas flow rate. The cross-sectional aperture of the gas channel at the inlet section 53 is d 1 is 4 mm, and the diameter of the gas channel in the tailstock 8 of the spray gun is 5 mm.

[0055] A high-speed low-temperature spray system for cooling the flame flow in the combustion chamber ignites after preheating the gas and the spray gun, such as Figure 5 As shown in the figure, after the combustion stabilizes, the cooling gas is injected into the combustion chamber in the form of linearly increasing flow rate to cool the flame flow; during the spraying process, the cooling gas flow rate is set to 2 mm 3 / min.

[0056] The deposition test was carried out using Ti powder with a particle size of 15-45 μm. The temperature at the spray gun outlet was measured to be 1000°C. The temperature of the particles measured using the DPV-2000 thermal spray online monitor was 750°C. The oxygen content of the coating was measured to be 0.3 at.%.

[0057] The above contents are 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 for cooling the flame flow in the combustion chamber, characterized in that: The invention comprises a combustion chamber (5), wherein the combustion chamber (5) is composed of a contraction section (51), a combustion section (52) and an inlet section (53), wherein the contraction section (51) is connected to the nozzle (2), and a porous catalytic ceramic plate (6), a gas distribution unit (7) and a spray gun tail seat (8) are arranged in sequence at the inlet section (53), a spray gun housing (3) is arranged outside the combustion chamber (5), and a spray gun housing (1) is arranged outside the nozzle (2), a powder delivery needle (9) is arranged in the middle of the spray gun tail seat (8), and the spray gun tail seat (8) is provided with a curved compressed air channel and is connected to the gas distribution unit (7), a cooling gas distribution ring (4) is arranged on one side of the combustion section (52) close to the contraction section (51), and an ignition port (13) is arranged on the other side, and a gas channel is arranged through the porous catalytic ceramic plate (6), the gas distribution unit (7), the spray gun tail seat (8) and is connected to a gas interface in sequence; The cooling gas distribution ring (4) is provided with a plurality of cooling gas inflow holes (11), the cooling gas inflow holes (11) are arranged through the cooling gas flow groove (10) and communicate with the combustion chamber (5), the plurality of cooling gas inflow holes (11) are arranged around the cooling gas distribution ring (4), and the plurality of cooling gas inflow holes (11) are symmetrically arranged with the axial direction where the cooling gas injection port (12) is located; The number of the cooling air inflow holes (11) is 2n, and the number of the cooling air inflow holes (11) on one side of the cooling air injection port (12) is n, where n≥4; The i-th hole diameter on the axial side of the cooling gas injection port (12) is the diameter of the first hole on the axial side of the cooling gas injection port (12). times.

2. A high-speed low-temperature spray gun for cooling the flame flow in the combustion chamber according to claim 1, characterized in that: The cooling gas distribution ring (4) and the combustion chamber (5) are provided with cooling gas flow grooves (10), the cooling gas flow grooves (10) are connected to the cooling gas injection port (12), and the cooling gas injection port (12) and the ignition port (13) are located on the same horizontal line.

3. A high-speed low-temperature spray gun for cooling the flame flow in the combustion chamber according to claim 2, characterized in that: The cross-sectional area of ​​the cooling air flow groove (10) S 1 is the area of ​​the cooling air inlet hole (11) S More than 8 times the sum of 2.

4. A high-speed low-temperature spray gun for cooling the flame flow in the combustion chamber according to claim 2, characterized in that: The distance between the center line of the cooling gas injection port (12) and the contraction section (51) is l 1 is the length of the combustion section (52) l 1 / 10~1 / 5 of 2.

5. A high-speed low-temperature spray gun for cooling the flame flow in the combustion chamber according to claim 1, characterized in that: The gas channel has a cross-sectional contraction at the inlet section (53), and the gas channel has an aperture of d 1 is the diameter of the gas channel in the tailstock (8) of the spray gun d 0.2-0.6 times of 2.

6. A spraying system using a high-speed low-temperature spray gun for cooling the flame flow in the combustion chamber as described in any one of claims 1 to 5, characterized in that: include: The gas module is used to deliver compressed air, cooling gas and fuel gas to the spray gun, including an air compressor connected to a gas storage tank and a dryer in sequence, the dryer connected to a control cabinet module and a gas heater in sequence through pipelines, a cooling gas bottle connected to a control cabinet module and a spray gun in sequence through pipelines, a fuel gas bottle and a vaporizer connected to a control cabinet module and a gas heater in sequence through pipelines, and the gas heater connected to the spray gun; The powder feeding module is used to feed powder to the spray gun, including a powder feeding gas bottle connected to the control cabinet module through a pipeline, and the control cabinet module is connected to the powder feeder and the spray gun in sequence through pipelines; The control cabinet module is used to control the flow of gas and powder; The spray gun heating module is used for preheating a high-speed low-temperature spray gun which cools the flame flow in the combustion chamber before ignition.

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