Method for preheating hollow blade of gas turbine and preparing coating with longitudinal cracks

Abstract

The invention discloses a method for preheating a hollow blade of a gas turbine and preparing a coating with longitudinal cracks. The method comprises the steps that firstly, a blade preheating and coating preparing device is built; 2, preheating the surface of the hollow blade of the gas turbine; and 3, spraying the hollow blade of the gas turbine. According to the method, the steps are simple, the air heater is adopted for preheating the rotating gas turbine hollow blade, so that the uniformity of surface temperature distribution of the gas turbine hollow blade is improved, and the coating with the longitudinal cracks can have the long service life while the good performance is kept.

Description

Technical Field

[0001] The invention belongs to the technical field of gas turbine hollow blade coatings, and in particular relates to a method for preheating a gas turbine hollow blade and preparing a coating with longitudinal cracks. Background Art

[0002] Gas turbines are one of the core power equipment in clean and efficient thermal power energy systems. The hollow blades of gas turbines work in harsh environments. Thermal barrier coatings are mainly used for gas turbine blades. They not only have thermal barrier effects, but also can prevent damage to the blades caused by oxidation, corrosion, and erosion by foreign objects.

[0003] In order to improve the long-term service life of thermal barrier coating materials, thermal barrier coatings with longitudinal crack structures have begun to emerge. The presence of longitudinal cracks can increase the interface fracture resistance of the coating. The introduction of longitudinal cracks improves the strain tolerance of the coating and reduces the thermal stress accumulated in the coating due to the difference in thermal expansion coefficient between the ceramic layer and the bonding layer, thereby extending its service life.

[0004] At present, the preheating treatment of the substrate is usually achieved by a plasma spray gun. The heat impulse that a plasma spray gun can provide in a short period of time is limited, which may lead to uneven temperature distribution on the blade. At the same time, when using a plasma spray gun for preheating, the local temperature of the bonding layer will be too high at the moment of contact of the plasma moment of the spray gun, which will cause the bonding layer on the substrate to oxidize. This oxidation reaction will change the physical and chemical properties of the bonding layer and may cause early failure of the coating.

[0005] Therefore, a method for preheating the hollow blades of a gas turbine and preparing a coating with longitudinal cracks with a reasonable design is needed. An air heater is used to preheat the rotating hollow blades of the gas turbine to improve the uniformity of the surface temperature distribution of the hollow blades of the gas turbine, so that the coating with longitudinal cracks can have a longer service life while maintaining good performance. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for preheating hollow blades of a gas turbine and preparing a coating with longitudinal cracks in view of the deficiencies in the above-mentioned prior art. The method has simple steps and reasonable design. An air heater is used to preheat the rotating hollow blades of the gas turbine to improve the uniformity of the surface temperature distribution of the hollow blades of the gas turbine, so that the coating with longitudinal cracks can have a longer service life while maintaining good performance.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preheating a hollow blade of a gas turbine and preparing a coating with longitudinal cracks, the method comprising the following steps: Step 1: Build a blade preheating and coating preparation device: Step 101, constructing a blade preheating device; wherein the blade preheating device comprises a rotatable worktable and a preheating device arranged on the side of the rotatable worktable, the preheating device comprises an air heater and an air outlet pipeline connected to the air heater, and the outlet of the air outlet pipeline is connected to the rotatable worktable; Step 102: Building an atmospheric plasma spraying device on the side of the rotatable worktable away from the air heater; wherein the atmospheric plasma spraying device includes a base, a six-axis robotic arm disposed on the base, and a plasma spray gun disposed at the end of the six-axis robotic arm; Step 2: Preheating of the surface of the hollow gas turbine blades: The hollow blade of the gas turbine rotates with the rotatable worktable, and the air heater passes hot air into the hollow blade of the gas turbine to heat it until the surface temperature of the hollow blade of the gas turbine reaches the set preheating temperature; Step 3: Spraying of hollow gas turbine blades: Step 301, the air heater continuously introduces hot air into the hollow blades of the gas turbine; Step 302: spraying the surface of the hollow blade of the gas turbine by operating a plasma spray gun through a six-axis robot arm to form a coating with longitudinal cracks; Step 303: Obtain a cross section of the gas turbine hollow blade with the longitudinal crack coating, and use a scanning electron microscope to scan the cross section of the gas turbine hollow blade with the longitudinal crack coating to obtain the longitudinal crack density.

[0008] The above-mentioned method for preheating hollow blades of a gas turbine and preparing a coating with longitudinal cracks, the rotatable worktable includes a bottom bracket, a worktable arranged on the bottom bracket, a turntable embedded in the worktable and flush with the worktable, and a motor drive component arranged at the bottom of the worktable and driving the turntable to rotate, the motor drive component includes an L-frame arranged at the bottom of the worktable, a hollow motor arranged on the L-frame and an intermediate shaft passing through the hollow motor, the lower end of the intermediate shaft is connected to a rotary joint, the outlet of the exhaust pipe is connected to the rotary joint, and the turntable is provided with a heat-resistant steel clamp for installing the hollow blades of the gas turbine.

[0009] The above-mentioned method for preheating hollow blades of a gas turbine and preparing a coating with longitudinal cracks, the intermediate shaft comprises a coaxially arranged outer shaft and an inner shaft extending from both ends of the outer shaft, the outer shaft is installed in the hollow motor and is transmission-connected, the upper end of the inner shaft extends into the turntable and is transmission-connected, and the lower end of the inner shaft passes through the L frame and is connected to the rotary joint; Sealing plates are arranged between the two ends of the outer shaft and the outer side wall of the inner shaft, and the cavity enclosed by the inner side wall of the outer shaft, the outer side wall of the inner shaft and the sealing plates is referred to as the outer cavity, and the interior of the inner shaft is hollow; the outlet of the inner shaft is located at the bottom opening of the blade root of the hollow blade of the gas turbine; A lower inlet pipe is arranged at the lower part of the outer shaft extending out of the L frame, and an upper inlet pipe is arranged at the upper part of the outer shaft close to the rotating disk. Both the lower inlet pipe and the upper inlet pipe are communicated with the outer cavity.

[0010] The above-mentioned method for preheating a hollow gas turbine blade and preparing a coating with longitudinal cracks, step 2, the specific process is as follows: Step 201, multiple clamping frames are arranged on a workbench, each clamping frame is clamped with an infrared thermometer; Step 202, mounting the blade root of the hollow gas turbine blade on a heat-resistant steel fixture, with the bottom surface of the blade root of the hollow gas turbine blade in contact with the surface of the turntable, and the blade top of the hollow gas turbine blade facing upward; Step 203, operate the hollow motor to drive the gas turbine hollow blade to rotate, and at the same time, operate the air heater to operate, the hot air output from the air outlet pipeline connected to the air heater passes through the inner shaft of the intermediate shaft, and the hot air output from the inner shaft outlet passes through the blade root bottom of the gas turbine hollow blade and enters the gas turbine hollow blade to heat the gas turbine hollow blade; Step 204: During the rotation and heating process of the hollow blades of the gas turbine, a plurality of infrared thermometers perform non-contact detection of the surface temperature of the hollow blades of the gas turbine according to a set sampling time until the surface temperature of the hollow blades of the gas turbine reaches a set preheating temperature.

[0011] The above-mentioned method for preheating a hollow gas turbine blade and preparing a coating with longitudinal cracks, step 204, specifically comprises the following steps: Step 2041, performing average and standard deviation processing on multiple surface temperature values ​​at any sampling time to obtain the surface temperature average and the surface temperature standard deviation; Step 2042: If the standard deviation of the surface temperature at the sampling time is less than 10°C, and the deviation between the average surface temperature and the set preheating temperature satisfies (-20°C, 20°C), the preheating of the hollow blade of the gas turbine is stable, and the surface temperature of the hollow blade of the gas turbine reaches the set preheating temperature.

[0012] In the above-mentioned method for preheating a hollow gas turbine blade and preparing a coating with longitudinal cracks, after step 3, the following process is performed: Step A, repeating step 2 and step 3 multiple times, obtaining the longitudinal crack density by scanning electron microscopy at different set preheating temperatures; Step B, using different set preheating temperatures as the horizontal coordinates and the longitudinal crack densities corresponding to the different set preheating temperatures as the vertical coordinates, to obtain a relationship diagram between the longitudinal crack density and the substrate preheating temperature.

[0013] In the above-mentioned method for preheating hollow blades of a gas turbine and preparing a coating with longitudinal cracks, in step 203, during the process of hot air passing through the intermediate shaft, the lower inlet pipe is connected to the inlet cooling water pipe, and the upper inlet pipe is connected to the return cooling water pipe to cool the external cavity.

[0014] Compared with the prior art, the present invention has the following advantages: 1. The method of the present invention has simple steps and reasonable design, and solves the problem of uneven preheating temperature distribution before spraying on the surface of hollow blades of gas turbines.

[0015] 2. The hollow blades of the gas turbine of the present invention are installed on a rotatable worktable and rotate with the rotatable worktable. During the rotation of the hollow blades of the gas turbine, they are preheated by an air heater. In this way, hot air is introduced while rotating to heat the hollow blades of the gas turbine, thereby improving the uniformity of the surface temperature distribution of the hollow blades of the gas turbine.

[0016] 3. When the hot air output by the air heater of the present invention enters the hollow blade of the gas turbine through the bottom of the blade root of the hollow blade of the gas turbine for heating, the hot air overflows through the cooling holes on the hollow blade, and forms a hot air film around the outer surface of the blade, thereby reducing the heat exchange between the blade and the surrounding cold air during the blade preheating and coating preparation process, and improving the preheating effect of the blade substrate; in addition, the hot air overflows through the cooling holes on the hollow blade, which can also reduce the spray thickness at the cooling holes when the plasma spray gun sprays the surface of the hollow blade of the gas turbine, thereby reducing the subsequent coating treatment at the cooling holes.

[0017] 4. The present invention realizes preheating of the hollow blades of the gas turbine, reaches the set preheating temperature and the preheating is stable, and then continuously introduces hot air into the interior of the hollow blades of the gas turbine. The plasma spray gun sprays the surface of the hollow blades of the gas turbine to form a coating with longitudinal cracks, so that the coating with longitudinal cracks can have a long service life while maintaining good performance.

[0018] In summary, the method of the present invention has simple steps and reasonable design. An air heater is used to preheat the rotating hollow blade of a gas turbine to improve the uniformity of the surface temperature distribution of the hollow blade of the gas turbine, so that the coating with longitudinal cracks can have a longer service life while maintaining good performance.

[0019] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the structure of the blade preheating and coating preparation device of the present invention.

[0021] Figure 2 It is a structural schematic diagram of the rotatable workbench of the present invention.

[0022] Figure 3 It is a schematic structural diagram of the intermediate shaft of the present invention.

[0023] Figure 4 The figure is a flowchart of the method of the present invention.

[0024] 1—air heater; 2—air outlet pipe; 3—bottom bracket; 4—Hollow motor; 4-1—Turntable; 4-2—L frame; 5—six-axis robot arm; 6—intermediate axis; 6-1—inner shaft; 6-2—outer shaft; 6-3—lower end inlet pipe; 6-4—upper inlet pipe; 6-5—limiting connecting plate; 6-6—sealing plate; 6-7—rotating joint; 7—gas turbine hollow blade; 8—plasma spray gun; 9—heat-resistant steel fixture; 10—infrared thermometer; 10-1—clamping frame; 11—working table; 12—base. DETAILED DESCRIPTION

[0025] like Figures 1 to 4 As shown, the method for preheating a hollow gas turbine blade and preparing a coating with longitudinal cracks of the present invention comprises the following steps: The method comprises the following steps: Step 1: Build a blade preheating and coating preparation device: Step 101, constructing a blade preheating device; wherein the blade preheating device comprises a rotatable worktable and a preheating device arranged on the side of the rotatable worktable, the preheating device comprises an air heater 1 and an air outlet pipeline 2 connected to the air heater 1, and the outlet of the air outlet pipeline 2 is connected to the rotatable worktable; Step 102: Building an atmospheric plasma spraying device on the side of the rotatable workbench away from the air heater 1; wherein the atmospheric plasma spraying device includes a base 12, a six-axis robot 5 disposed on the base 12, and a plasma spray gun 8 disposed at the end of the six-axis robot 5; Step 2: Preheating of the surface of the hollow gas turbine blades: The gas turbine hollow blade 7 rotates with the rotatable worktable, and the air heater 1 passes hot air into the gas turbine hollow blade 7 to heat it until the surface temperature of the gas turbine hollow blade 7 reaches the set preheating temperature; Step 3: Spraying of hollow gas turbine blades: Step 301, the air heater 1 continuously passes hot air into the hollow blade 7 of the gas turbine; Step 302: The six-axis robot arm 5 operates the plasma spray gun 8 to spray the surface of the hollow blade 7 of the gas turbine to form a coating with longitudinal cracks; Step 303: Obtain a cross section of the gas turbine hollow blade with the longitudinal crack coating, and use a scanning electron microscope to scan the cross section of the gas turbine hollow blade with the longitudinal crack coating to obtain the longitudinal crack density.

[0026] In this embodiment, the rotatable workbench includes a bottom bracket 3, a workbench 11 arranged on the bottom bracket 3, a turntable 4-1 embedded in the workbench 11 and flush with the workbench 11, and a motor driver arranged at the bottom of the workbench 11 and driving the turntable 4-1 to rotate, the motor driver includes an L frame 4-2 arranged at the bottom of the workbench 11, a hollow motor 4 arranged on the L frame 4-2 and an intermediate shaft 6 passing through the hollow motor 4, the lower end of the intermediate shaft 6 is connected to a rotary joint 6-7, the outlet of the exhaust pipe 2 is connected to the rotary joint 6-7, and the turntable 4-1 is provided with a heat-resistant steel clamp 9 for installing the hollow blades 7 of the gas turbine.

[0027] In this embodiment, the intermediate shaft 6 includes a coaxially arranged outer shaft 6-2 and an inner shaft 6-1 extending from both ends of the outer shaft 6-2. The outer shaft 6-2 is installed in the hollow motor 4 and is transmission-connected. The upper end of the inner shaft 6-1 extends into the turntable 4-1 and is transmission-connected. The lower end of the inner shaft 6-1 passes through the L frame 4-2 and is connected to the rotary joint 6-7. A sealing plate 6-6 is provided between the two ends of the outer shaft 6-2 and the outer side wall of the inner shaft 6-1. The cavity enclosed by the inner side wall of the outer shaft 6-2, the outer side wall of the inner shaft 6-1 and the sealing plate 6-6 is referred to as the outer cavity. The interior of the inner shaft 6-1 is hollow. The outlet of the inner shaft 6-1 is located at the bottom opening of the blade root of the hollow blade 7 of the gas turbine. The lower part of the outer shaft 6-2 extending out of the L frame 4-2 is provided with a lower end inlet pipe 6-3, and the upper part of the outer shaft 6-2 close to the turntable 4-1 is provided with an upper end inlet pipe 6-4, and the lower end inlet pipe 6-3 and the upper end inlet pipe 6-4 are both connected to the outer cavity.

[0028] In this embodiment, step 2, the specific process is as follows: Step 201, a plurality of clamping frames 10-1 are arranged on the workbench 11, and each clamping frame 10-1 is clamped with an infrared thermometer 10; Step 202, install the blade root of the gas turbine hollow blade 7 on the heat-resistant steel fixture 9, with the bottom surface of the blade root of the gas turbine hollow blade 7 in contact with the surface of the turntable 4-1, and the blade top of the gas turbine hollow blade 7 facing upward; Step 203, operate the hollow motor 4 to drive the gas turbine hollow blade 7 to rotate, and at the same time, operate the air heater 1 to operate, and the hot air output from the air outlet pipeline 2 connected to the air heater 1 passes through the inner shaft 6-1 of the intermediate shaft 6, and the hot air output from the outlet of the inner shaft 6-1 passes through the blade root bottom of the gas turbine hollow blade 7 and enters the gas turbine hollow blade 7 to heat the gas turbine hollow blade 7; Step 204: During the rotation and heating process of the gas turbine hollow blade 7, a plurality of infrared thermometers 10 perform non-contact detection of the surface temperature of the gas turbine hollow blade 7 according to the set sampling time until the surface temperature of the gas turbine hollow blade 7 reaches the set preheating temperature.

[0029] In this embodiment, step 204, the specific process is as follows: Step 2041, performing average and standard deviation processing on multiple surface temperature values ​​at any sampling time to obtain the surface temperature average and the surface temperature standard deviation; Step 2042: If the standard deviation of the surface temperature at the sampling time is less than 10°C, and the deviation between the average surface temperature and the set preheating temperature satisfies (-20°C, 20°C), the preheating of the gas turbine hollow blade 7 is stable, and the surface temperature of the gas turbine hollow blade 7 reaches the set preheating temperature.

[0030] In this embodiment, after step 3, the following process is performed: Step A, repeating step 2 and step 3 multiple times, obtaining the longitudinal crack density by scanning electron microscopy at different set preheating temperatures; Step B, using different set preheating temperatures as the horizontal coordinates and the longitudinal crack densities corresponding to the different set preheating temperatures as the vertical coordinates, to obtain a relationship diagram between the longitudinal crack density and the substrate preheating temperature.

[0031] In this embodiment, in step 203, when the hot air passes through the intermediate shaft 6, the lower inlet pipe 6-3 is connected to the inlet cooling water pipe, and the upper inlet pipe 6-4 is connected to the return cooling water pipe to cool the external cavity.

[0032] In this embodiment, during actual use, in step 301, the air heater 1 continuously introduces hot air into the hollow gas turbine blade 7 so that the surface temperature is maintained at the set preheating temperature during the spraying process.

[0033] In this embodiment, in actual use, a limit connecting plate 6-5 is provided at the top of the inner shaft 6-1, a circular groove for the limit connecting plate 6-5 to be embedded in the top surface of the turntable 4-1 is provided, the limit connecting plate 6-5 is embedded in the circular groove and connected to the turntable 4-1, and the outer shaft 6-2 is located below the turntable 4-1. The limit connecting plate 6-5, the turntable 4-1 and the upper surface of the workbench 11 are flush.

[0034] In this embodiment, during actual use, the inner shaft 6-1 adopts a heat-insulating shaft to prevent heat loss of the hot air transported in the inner shaft 6-1, or the inlet cooling water pipe and the return cooling water pipe are connected to the cooling water tank. When hot air passes through the inner shaft 6-1, the outer cavity is cooled to prevent the outer cavity temperature from being too high and affecting the working performance of the hollow motor 4.

[0035] In this embodiment, during actual use, when the hot air output by the inner shaft 6-1 enters the hollow gas turbine blade 7 through the bottom of the blade root of the hollow gas turbine blade 7 and is heated, the hot air overflows through the cooling holes on the hollow blade, and forms a hot air film around the outer surface of the blade, thereby reducing the heat exchange between the blade and the surrounding cold air during the blade preheating and coating preparation process, thereby improving the preheating effect of the blade substrate; in addition, the hot air overflows through the cooling holes on the hollow blade, which can also reduce the spray thickness at the cooling hole when the plasma spray gun 8 sprays the surface of the hollow gas turbine blade 7, thereby reducing the subsequent coating treatment at the cooling hole.

[0036] In this embodiment, when actually used, the plasma spray gun 8 sprays the surface of the hollow blade 7 of the gas turbine, and the preparation process parameters in the patent CN117072253B heavy-duty gas turbine high-temperature blade thermal barrier coating and design, manufacturing and evaluation method can be referred to.

[0037] In this embodiment, it should be noted that the figure does not show a plurality of infrared thermometers 10 ; in actual use, a plurality of infrared thermometers 10 detect a plurality of locations on the surface of the hollow blade 7 of the gas turbine.

[0038] In this embodiment, in actual use, the sampling time set in step 204 is 1s to 5s.

[0039] In this embodiment, in actual use, the preheating temperature is set in the range of 550°C to 750°C to produce a crack density of 0.5 / mm to 6 / mm to avoid too low crack density which will lead to the ineffective release of thermal stress and increase the risk of coating peeling. Too high crack density will weaken the mechanical strength of the coating and reduce the thermal shock resistance.

[0040] In this embodiment, it should be noted that the coating thickness on the surface of the hollow blade of the gas turbine is 300 microns to 1000 microns.

[0041] In this embodiment, it should be noted that the longitudinal cracks extend along the thickness direction of the coating on the surface of the hollow blade of the gas turbine.

[0042] In this embodiment, it should be noted that the coating in this application relies on conventional atmospheric plasma, and the spraying process parameters are 38KW to 45KW in power and 60mm to 100mm in spraying distance. This is because the temperature of the blade substrate is increased by preheating measures, which effectively reduces the energy consumption of the YSZ molten powder in the first stage at the moment of spraying onto the blade substrate, and reserves sufficient energy for the subsequent second stage. Because the YSZ molten powder condenses rapidly in the first stage, a large number of microscopic reticular cracks are generated, and further cools in the second stage to generate longitudinal cracks. When the spraying parameters are determined, the total energy of the YSZ molten powder is certain, so increasing the preheating temperature can effectively reduce the energy consumption in the first stage and reserve more energy for the initiation of longitudinal cracks in the second stage. Therefore, when preparing a coating with longitudinal cracks, it is necessary to control the preheating temperature of the substrate.

[0043] In summary, the method of the present invention has simple steps and reasonable design. An air heater is used to preheat the rotating hollow blade of a gas turbine to improve the uniformity of the surface temperature distribution of the hollow blade of the gas turbine, so that the coating with longitudinal cracks can have a longer service life while maintaining good performance.

[0044] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural change made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preheating a hollow gas turbine blade and preparing a coating with longitudinal cracks, characterized in that: The method comprises the following steps: Step 1: Build a blade preheating and coating preparation device: Step 101, constructing a blade preheating device; wherein the blade preheating device comprises a rotatable worktable and a preheating device arranged on the side of the rotatable worktable, the preheating device comprises an air heater (1) and an air outlet pipeline (2) connected to the air heater (1), and the outlet of the air outlet pipeline (2) is connected to the rotatable worktable; Step 102: Building an atmospheric plasma spraying device on the side of the rotatable worktable away from the air heater (1); wherein the atmospheric plasma spraying device comprises a base (12), a six-axis robot arm (5) disposed on the base (12), and a plasma spray gun (8) disposed at the end of the six-axis robot arm (5); Step 2: Preheating of the surface of the hollow gas turbine blades: The gas turbine hollow blade (7) rotates with the rotatable worktable, and the air heater (1) passes hot air into the gas turbine hollow blade (7) to heat it until the surface temperature of the gas turbine hollow blade (7) reaches a set preheating temperature; Step 3: Spraying of hollow gas turbine blades: Step 301: The air heater (1) continuously introduces hot air into the hollow blade (7) of the gas turbine; Step 302: using a six-axis robot arm (5) to operate a plasma spray gun (8) to spray the surface of the hollow blade (7) of the gas turbine to form a coating with longitudinal cracks; Step 303: Obtain a cross section of the gas turbine hollow blade with the longitudinal crack coating, and use a scanning electron microscope to scan the cross section of the gas turbine hollow blade with the longitudinal crack coating to obtain the longitudinal crack density.

2. The method for preheating a hollow gas turbine blade and preparing a coating with longitudinal cracks according to claim 1, characterized in that: The rotatable workbench comprises a bottom bracket (3), a workbench (11) arranged on the bottom bracket (3), a turntable (4-1) embedded in the workbench (11) and flush with the workbench (11), and a motor drive component arranged at the bottom of the workbench (11) and driving the turntable (4-1) to rotate, the motor drive component comprising an L-frame (4-2) arranged at the bottom of the workbench (11), a hollow motor (4) arranged on the L-frame (4-2), and an intermediate shaft (6) passing through the hollow motor (4), the lower end of the intermediate shaft (6) being connected to a rotary joint (6-7), the outlet of the gas outlet pipeline (2) being connected to the rotary joint (6-7), and the turntable (4-1) being provided with a heat-resistant steel fixture (9) for mounting a hollow blade (7) of a gas turbine.

3. The method for preheating a hollow gas turbine blade and preparing a coating with longitudinal cracks according to claim 2, characterized in that: The intermediate shaft (6) comprises a coaxially arranged outer shaft (6-2) and an inner shaft (6-1) extending from both ends of the outer shaft (6-2); the outer shaft (6-2) is installed in the hollow motor (4) and is transmission-connected thereto; the upper end of the inner shaft (6-1) extends into the turntable (4-1) and is transmission-connected thereto; the lower end of the inner shaft (6-1) passes through the L-frame (4-2) and is connected to a rotary joint (6-7); A sealing plate (6-6) is provided between the two ends of the outer shaft (6-2) and the outer side wall of the inner shaft (6-1); a cavity enclosed by the inner side wall of the outer shaft (6-2), the outer side wall of the inner shaft (6-1) and the sealing plate (6-6) is referred to as an outer cavity; the interior of the inner shaft (6-1) is hollow; the outlet of the inner shaft (6-1) is located at the bottom opening of the blade root of a hollow blade (7) of a gas turbine; The lower part of the outer shaft (6-2) extending out of the L frame (4-2) is provided with a lower inlet pipe (6-3), and the upper part of the outer shaft (6-2) close to the rotating disk (4-1) is provided with an upper inlet pipe (6-4), and both the lower inlet pipe (6-3) and the upper inlet pipe (6-4) are in communication with the outer cavity.

4. The method for preheating a hollow gas turbine blade and preparing a coating with longitudinal cracks according to claim 3, characterized in that: Step 2: The specific process is as follows: Step 201, arranging a plurality of clamping frames (10-1) on a workbench (11), each clamping frame (10-1) clamping an infrared thermometer (10); Step 202, mounting the blade root of the gas turbine hollow blade (7) on the heat-resistant steel fixture (9), with the bottom surface of the blade root of the gas turbine hollow blade (7) in contact with the surface of the rotating disk (4-1), and the blade top of the gas turbine hollow blade (7) facing upwards; Step 203, operating the hollow motor (4) to drive the gas turbine hollow blade (7) to rotate, and at the same time, operating the air heater (1) to operate, and hot air output from the air outlet pipeline (2) connected to the air heater (1) passes through the inner shaft (6-1) of the intermediate shaft (6), and the hot air output from the outlet of the inner shaft (6-1) passes through the bottom of the blade root of the gas turbine hollow blade (7) and enters the gas turbine hollow blade (7), thereby heating the gas turbine hollow blade (7); Step 204: During the rotation and heating process of the gas turbine hollow blade (7), the plurality of infrared thermometers (10) perform non-contact detection of the surface temperature of the gas turbine hollow blade (7) according to a set sampling time until the surface temperature of the gas turbine hollow blade (7) reaches a set preheating temperature.

5. The method for preheating a hollow gas turbine blade and preparing a coating with longitudinal cracks according to claim 4, characterized in that: Step 204, the specific process is as follows: Step 2041, performing average and standard deviation processing on multiple surface temperature values ​​at any sampling time to obtain the surface temperature average and the surface temperature standard deviation; Step 2042: If the standard deviation of the surface temperature at the sampling time is less than 10°C, and the deviation between the average surface temperature and the set preheating temperature satisfies (-20°C, 20°C), the preheating of the gas turbine hollow blade (7) is stable, and the surface temperature of the gas turbine hollow blade (7) reaches the set preheating temperature.

6. The method for preheating a hollow gas turbine blade and preparing a coating with longitudinal cracks according to claim 1, characterized in that: After step 3, perform the following process: Step A, repeating step 2 and step 3 multiple times, obtaining the longitudinal crack density by scanning electron microscopy at different set preheating temperatures; Step B, using different set preheating temperatures as the horizontal coordinates and the longitudinal crack densities corresponding to the different set preheating temperatures as the vertical coordinates, to obtain a relationship diagram between the longitudinal crack density and the substrate preheating temperature.

7. The method for preheating a hollow gas turbine blade and preparing a coating with longitudinal cracks according to claim 4, characterized in that: In step 203, when the hot air passes through the intermediate shaft (6), the lower inlet pipe (6-3) is connected to the inlet cooling water pipe, and the upper inlet pipe (6-4) is connected to the return cooling water pipe, so as to cool the external cavity.

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