Hollow blade inner cavity polishing method

Abstract

The invention discloses a method for polishing an inner cavity of a hollow blade. The method comprises the following steps: removing oxides on the surface of the inner cavity of the hollow blade by using acid liquor; the outlet end of a polishing solution pipeline is arranged at the airflow outlet end of the hollow blade, and polishing solution is conveyed to the surface of an inner cavity of the hollow blade through the outlet end of the polishing solution pipeline through a pump; the outlet end of the polishing solution pipeline is arranged at the air flow inlet end of the hollow blade, the polishing solution is conveyed to the surface of an inner cavity of the hollow blade through the outlet end of the polishing solution pipeline through a pump, and the polishing solution is conveyed to the surface of the inner cavity of the hollow blade through a specific polishing strategy and arrangement of the polishing pipeline. The polishing efficiency and consistency of the inner cavity of the large-size hollow turbine blade are improved, meanwhile, damage possibly caused in the inner cavity cleaning process and operation complexity are reduced, and the production efficiency of the hollow blade is improved.

Description

Technical Field

[0001] The present invention relates to the field of turbine blade manufacturing, and particularly to a method for polishing the inner cavity of a hollow blade. Background Art

[0002] Heavy-duty gas turbines are core power equipment using high-temperature gas as the working medium. Turbine blades are key hot-end components that determine the output power of gas turbines and are crucial for the performance realization of the entire gas turbine. The sizes of turbine blades of high-power heavy-duty gas turbines are several times larger than those of aero-engine blades. Taking a 300MW-class heavy-duty gas turbine as an example, the length of the largest hollow turbine blade exceeds 650mm, and the weight exceeds 25kg.

[0003] With the improvement of gas turbine efficiency, the service temperature of turbine blades has been continuously increasing, and they are subjected to the impact of high-temperature and high-pressure gas exceeding 1400°C during the operation of the gas turbine. This temperature far exceeds the temperature-bearing limit of the superalloy material used for the substrate. Therefore, it is necessary to cool the turbine blades, that is, to adopt a hollow cooling structure, and at the same time, a thermal barrier coating is applied to the gas erosion surface to ensure the safe and reliable operation of the transition section at high temperatures.

[0004] To manufacture hollow turbine blades, ceramic-based cores must be used. The hollow turbine blades are cast by the lost wax process. The innermost part of the entire casting system is the core, followed by the casting wax that coats the core, and the outside of the wax is coated with a ceramic shell. The casting system thus formed causes the casting wax to vaporize and disappear during the casting process, and the molten metal liquid fills the space between the core and the shell to form a complex structure with a cavity and internal cooling ribs and partitions. After solidification, the outer shell and the core in the inner cavity need to be removed to obtain the turbine casting. The shell is usually removed by physical methods, and the core is usually removed by a high-pressure core removal kettle filled with KOH or NaOH solution through a chemical reaction.

[0005] During the casting process of the blade, the molten high-temperature alloy liquid has a very high temperature. During the solidification process, the core mainly composed of silicon oxide will react with the high-temperature alloy liquid, generating a rough reaction layer, which causes an increase in the inner cavity roughness after core removal. The inner cavity with a more intense reaction has a roughness higher than Ra3.2μm.

[0006] In practice, for the inner cavity with a relatively high roughness, sandblasting is used for cleaning. Sandblasting has certain risks. Even when using relatively fine sand grains and a relatively low sandblasting pressure, the rib structure on the inner cavity will be damaged. At present, when polishing the complex hollow structure of turbine blades with a chemical polishing solution, it is easy to cause differences in the inner cavity roughness of the blades due to reasons such as uneven polishing solution pressure.

[0007] In patent document CN114113337B, a chemical treatment of an additive manufacturing workpiece is disclosed. By flowing a chemical polishing solution in the internal cavity of an AM metal workpiece, surface finishing of the internal cavity is achieved. The method includes providing a connector fluidly connected to the internal cavity and flowing the chemical polishing solution through the connector to process the internal cavity to a desired degree of completion. This method can significantly improve the surface quality of the internal cavity of an additive manufacturing metal workpiece, remove internal debris and temporary support structures, and solve the problem of uneven roughness during chemical polishing of the complex cavity of a hollow blade.

[0008] In patent document CN112496341B, a method for selective laser melting forming and post-treatment of a thin-walled sandwich cooling structure is disclosed, including design optimization based on additive manufacturing technology and establishing a three-dimensional model; placing the established model as required; intercepting local parts for forming and post-treatment tests, and iteratively optimizing the model according to the liquid flow results; adding supports; selective laser melting forming; cleaning the powder and performing wax filling protection; using wire electrical discharge machining, machining, and manual grinding to remove external supports, and performing dewaxing treatment after completion; heat treatment and using chemical polishing to finish the inner surface of the thin-walled sandwich to meet the requirements of the inner cavity finish, and solving the problem of uneven roughness during chemical polishing of the complex cavity of a hollow blade. Summary of the Invention

[0009] Based on the above technical problems, the present invention proposes a method for polishing the inner cavity of a hollow blade, which solves the problem of uneven roughness during chemical polishing of the complex cavity of a hollow blade.

[0010] To achieve the above object, the present invention proposes a method for polishing the inner cavity of a hollow blade.

[0011] A method for polishing the inner cavity of a hollow blade includes:

[0012] S1: Using an acid solution to remove oxides on the inner cavity surface of the hollow blade;

[0013] S2: Placing the outlet end of the polishing solution pipeline at the air outlet end of the hollow blade, and pumping the polishing solution through the outlet end of the polishing solution pipeline to the inner cavity surface of the hollow blade;

[0014] S3: Placing the outlet end of the polishing solution pipeline at the air inlet end of the hollow blade, and pumping the polishing solution through the outlet end of the polishing solution pipeline to the inner cavity surface of the hollow blade.

[0015] Further, in step S1, it includes:

[0016] The acid solution includes sulfuric acid with a concentration of 5%-8% and / or nitric acid with a concentration of 8%-10%.

[0017] Further, in the step S1, it includes:

[0018] By immersing the hollow blade in the acid solution, the oxides on the inner cavity surface of the hollow blade are removed.

[0019] Further, in the step S1, it includes:

[0020] The air flow outlet end and the air flow inlet end of the hollow blade are pre-shielded with a peelable electroplating protective glue.

[0021] Further, in the step S1, it also includes:

[0022] After removing the oxides on the inner cavity surface of the hollow blade, the surface of the hollow blade is cleaned with alcohol.

[0023] Further, it also includes:

[0024] The tenon part of the hollow blade is the air flow inlet end;

[0025] The tip part of the hollow blade is the air flow outlet end.

[0026] Further, in the step S2, it also includes:

[0027] The outlet end of the polishing liquid pipeline includes a main pipeline outlet and a plurality of sub-pipeline outlets.

[0028] Further, in the step S2, it also includes:

[0029] If the length of the hollow blade is less than 400 mm, only the main pipeline outlet of the polishing liquid pipeline is arranged at the air flow outlet end to convey the polishing liquid;

[0030] If the length of the hollow blade is greater than 400 mm, the main pipeline outlet of the polishing liquid pipeline is arranged at the air flow outlet end, and at least one sub-pipeline outlet is set. The distance between the sub-pipeline outlet and the main pipeline outlet is greater than 400 mm, and the number N of the sub-pipeline outlets is:

[0031]

[0032] wherein, L is the length of the hollow blade, and N is rounded down to an integer.

[0033] Further, in the step S2, it also includes:

[0034] The diameter of the main pipeline outlet is 8 mm - 10 mm, and the diameter of the sub-pipeline outlet is 3 mm - 5 mm.

[0035] Further, in the step S2, it includes:

[0036] The composition of the polishing liquid includes sulfuric acid, nitric acid, sulfuric acid and / or nitric acid with a content of 48 g / L - 52 g / L, phosphoric acid with a content of 48 g / L - 52 g / L, sodium methylene bisnaphthalenesulfonate with a content of 4 g / L - 6 g / L, sodium dodecyl sulfate with a content of 1 g / L - 10 g / L, hexamethylenetetramine with a content of 0.5 g / L - 1 g / L, and the balance is water.

[0037] Further, in the step S2, it includes:

[0038] The flow rate of the polishing liquid is 600 ml / min - 800 ml / min, and the conveying time of the polishing liquid is 10 min - 15 min.

[0039] Further, in the step S3, it further includes:

[0040] If the length of the hollow blade is less than 400 mm, only the main pipe outlet of the polishing liquid pipe is arranged at the air inlet end to convey the polishing liquid;

[0041] If the length of the hollow blade is greater than 400 mm, the main pipe outlet of the polishing liquid pipe is arranged at the air inlet end, and at least one sub-pipe outlet is set. The distance between the sub-pipe outlet and the main pipe outlet is greater than 400 mm, and the number N of the sub-pipe outlets is:

[0042]

[0043] where L is the length of the hollow blade, and N is rounded down to an integer.

[0044] Further, in the step S3, it includes:

[0045] The flow rate of the polishing liquid is 400 ml / min - 500 ml / min, and the conveying time of the polishing liquid is 8 min - 12 min.

[0046] Further, in the step S3, it further includes:

[0047] Rinse the hollow blade with water for 8 min - 10 min.

[0048] Further, in the step S3, it further includes:

[0049] Use compressed air to remove the remaining water in the inner cavity and outer surface of the hollow blade.

[0050] Further, in the step S3, it includes:

[0051] The inner cavity surface roughness of the hollow blade after being polished by the polishing liquid is 0.5μm - 1μm.

[0052] Based on the above technical solution, the present invention has at least the following beneficial effects:

[0053] 1. The present invention provides a method for polishing the inner cavity of a hollow blade. By setting specific polishing strategies and polishing pipelines, the polishing efficiency and consistency of the inner cavity of large-sized hollow turbine blades are improved, and at the same time, the damage that may be caused during the inner cavity cleaning process is significantly reduced. By using a specific chemical polishing liquid, the roughness of the inner cavity of the blade is effectively reduced, avoiding the metal thinning and damage to the cooling structure that may be caused by the traditional physical sandblasting method. This not only improves the polishing quality but also maintains the integrity of the inner cavity of the blade, thereby extending the service life of the turbine blade and improving the reliability of the gas turbine.

[0054] 2. The present invention provides a method for polishing the inner cavity of a hollow blade. By finely proportioning the polishing liquid, the controllability and accuracy of the polishing process are improved. It is not only applicable to large-sized turbine blades with complex inner cavity structures but also can adapt to blades of different shapes and sizes, including blades with multiple cooling channels and cooling rib structures. This wide applicability enables the technical solution of the present invention to be widely applied to the manufacturing and repair processes of various gas turbine blades.

[0055] 3. The present invention provides a method for polishing the inner cavity of a hollow blade. By designing a good polishing process and polishing liquid, the traditional complex mechanical polishing, sandblasting or manual grinding steps are simplified. This method avoids the use of heavy machinery and complex operating equipment, thereby reducing the requirements for professional technology and equipment, making the polishing process more convenient and fast. The simplified process not only reduces the complexity of the operation but also shortens the production cycle and improves the production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The specification drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0057] Figure 1 shows a schematic flow diagram of a method for polishing the inner cavity of a hollow blade in an embodiment;

[0058] Figure 2 shows a three-dimensional structure schematic diagram of a hollow blade in an embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0059] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0060] The present invention will be further described in detail below in conjunction with specific embodiments, and these embodiments should not be construed as limiting the scope claimed by the present invention. The term "comprising" indicates the presence of features when used, but does not exclude the presence or addition of one or more other features; the orientation or positional relationship indicated by terms such as "lateral", "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for convenience of description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation on the present invention; in addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0061] In the description, it should be noted that unless otherwise clearly specified and defined, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In addition, in the description of the present invention, unless otherwise stated, the meaning of "a plurality" is two or more.

[0062] Embodiment

[0063] To solve the problem of uneven roughness during chemical polishing of the complex cavities of hollow blades, the present invention proposes a method for polishing the inner cavity of hollow blades, and the process flow is as Figure 1 shown below.

[0064] Embodiment 1

[0065] One such as Figure 2The length of the hollow blade shown is 380 mm. Sulfuric acid with a concentration of 5% is configured as the acid solution to fill the soaking tank. First, the tip and tenon of the hollow blade to be polished are respectively shielded with peelable electroplating protective glue. Subsequently, the hollow blade to be polished is placed in the soaking tank for 10 minutes, and the soaking tank is stirred. After 10 minutes, the inner cavity of the hollow blade to be polished is observed. If the oxides are not removed sufficiently, the above steps can be repeated and soaked for another 10 minutes until the oxides in the inner cavity are removed. Then, the hollow blade to be polished is taken out of the soaking tank, and the inner cavity surface of the hollow blade to be polished is cleaned with alcohol; a polishing solution is configured, which includes 48 g / L of sulfuric acid, 48 g / L of phosphoric acid, 4 g / L of sodium methylene bisnaphthalenesulfonate, 1 g / L of sodium dodecyl sulfate, and 0.5 g / L of hexamethylenetetramine, with the remaining being water. An acid-resistant industrial pump is selected, and the polishing solution pipeline is connected to the industrial pump. Since the length of the hollow blade to be polished is 380 mm, which is less than 400 mm, only the main pipeline outlet of the polishing solution pipeline is placed at the tip air outlet end of the hollow blade to be polished. The industrial pump is started, and the flow rate of the polishing solution is controlled at 600 ml / min. The polishing solution is continuously transported to scour the inner cavity of the hollow blade for 10 minutes to make the polishing solution fully contact the complex structure surface of the inner cavity of the hollow blade. After completion, the industrial pump is turned off. The main pipeline outlet of the polishing solution pipeline is placed at the tip air inlet end of the hollow blade to be polished, the industrial pump is started, and the flow rate of the polishing solution is controlled at 400 ml / min. The polishing solution is continuously transported to scour the inner cavity of the hollow blade for 8 minutes. After completion, the industrial pump is turned off; the hollow blade is rinsed with water for 8 minutes, and finally the water stains on the surface of the hollow blade are removed by compressed air. At this time, the surface roughness of the inner cavity of the polished hollow blade is 0.8 μm.

[0066] Example 2

[0067] When as Figure 2The length of the hollow blade to be polished is 450 mm. A mixed acid solution with a concentration of 5% sulfuric acid and a concentration of 8% nitric acid is configured as the acid solution to fill the soaking pool. First, the tip and tenon of the hollow blade to be polished are respectively shielded with a peelable electroplated protective glue. Subsequently, the hollow blade to be polished is placed in the soaking pool for 10 minutes, and the soaking pool is stirred. After 10 minutes, the inner cavity of the hollow blade to be polished is observed. If the oxides are not removed sufficiently, the above steps can be repeated and soaked for another 10 minutes until the oxides in the inner cavity are removed. Then, the hollow blade to be polished is taken out of the soaking pool, and the inner cavity surface of the hollow blade to be polished is cleaned with alcohol; Preferably, a polishing solution is configured, including 50 g / L of sulfuric acid, 50 g / L of phosphoric acid, 5 g / L of methylene bisnaphthalenesulfonic acid sodium, 5 g / L of sodium dodecyl sulfate, and 1 g / L of hexamethylenetetramine, with the remaining balance being water. An acid-resistant industrial pump is selected, and the polishing solution pipeline is connected to the industrial pump. Since the length of the hollow blade to be polished is 450 mm, which is greater than 400 mm, the main pipeline outlet of the polishing solution pipeline is placed at the tip air outlet end of the hollow blade to be polished. By calculation, it is obtained that 1 sub-pipeline outlet should be set. Therefore, at a position 400 mm from the tip as the starting point on the hollow blade, another sub-pipeline outlet is set. The industrial pump is started, and the flow rate of the polishing solution is controlled at 700 ml / min. The polishing solution is continuously transported to scour the inner cavity of the hollow blade for 12 minutes, so that the polishing solution is in full contact with the complex structure surface of the inner cavity of the hollow blade. After completion, the industrial pump is turned off. The main pipeline outlet of the polishing solution pipeline is placed at the tip air inlet end of the hollow blade to be polished, and the sub-pipeline outlet is set at a position 400 mm from the tenon as the starting point in the inner cavity of the hollow blade. The industrial pump is started, and the flow rate of the polishing solution is controlled at 450 ml / min. The polishing solution is continuously transported to scour the inner cavity of the hollow blade for 9 minutes. After completion, the industrial pump is turned off; The hollow blade is rinsed with water for 8 minutes, and finally the water stains on the surface of the hollow blade are removed by compressed air. At this time, the surface roughness of the inner cavity of the polished hollow blade is 0.5 μm.

[0068] Example 3

[0069] When as Figure 2The length of the hollow blade to be polished is 650 mm. A mixed acid solution with a concentration of 8% sulfuric acid and a concentration of 10% nitric acid is configured as the acid solution to fill the soaking pool. First, the tip and tenon of the hollow blade to be polished are respectively shielded with peelable electroplating protective glue. Subsequently, the hollow blade to be polished is placed in the soaking pool for 10 minutes, and the soaking pool is stirred. After 10 minutes, the inner cavity of the hollow blade to be polished is observed. If the oxides are not removed sufficiently, the above steps can be repeated and soaked for another 10 minutes until the oxides in the inner cavity are removed. Then, the hollow blade to be polished is taken out of the soaking pool, and the inner cavity surface of the hollow blade to be polished is cleaned with alcohol. Preferably, a polishing solution is configured, which includes 52 g / L of sulfuric acid, 52 g / L of phosphoric acid, 6 g / L of methylene bisnaphthalenesulfonic acid sodium, 10 g / L of sodium dodecyl sulfate, and 1 g / L of hexamine, with the remaining being water. An acid-resistant industrial pump is selected, and the polishing solution pipeline is connected to the industrial pump. Since the length of the hollow blade to be polished is 650 mm, which is greater than 400 mm, the main pipeline outlet of the polishing solution pipeline is placed at the air outlet end of the tip of the hollow blade to be polished. Through formula calculation, it is obtained that 5 sub-pipeline outlets should be set, and 1 sub-pipeline outlet can be set at the positions of 400 mm, 450 mm, 500 mm, 550 mm, and 600 mm from the tip as the starting point on the hollow blade respectively. The industrial pump is started, and the flow rate of the polishing solution is controlled at 800 ml / min, and the polishing solution is continuously transported to scour the inner cavity of the hollow blade for 10 minutes to make the polishing solution fully contact with the complex structure surface of the inner cavity of the hollow blade. After completion, the industrial pump is turned off, and the main pipeline outlet of the polishing solution pipeline is placed at the air inlet end of the tip of the hollow blade to be polished, and the other sub-pipeline outlets are set at the positions of 400 mm, 450 mm, 500 mm, 550 mm, and 600 mm from the tenon as the starting point in the inner cavity of the hollow blade. The industrial pump is started to control the flow rate of the polishing solution at 500 ml / min, and the polishing solution is continuously transported to scour the inner cavity of the hollow blade for 10 minutes. After completion, the industrial pump is turned off; the hollow blade is rinsed with water for 8 minutes, and finally the water stains on the surface of the hollow blade are removed by compressed air. At this time, the surface roughness of the inner cavity of the polished hollow blade is 0.6 μm.

[0070] In summary, from the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0071] 1. The present invention provides a method for polishing the inner cavity of a hollow blade. By means of a specific polishing strategy and the setting of a polishing pipeline, the polishing efficiency and consistency of the inner cavity of large-sized hollow turbine blades are improved, and at the same time, the damage that may be caused during the inner cavity cleaning process is significantly reduced. By using a specific chemical polishing solution, the roughness of the inner cavity of the blade is effectively reduced, avoiding the metal thinning and damage to the cooling structure that may be caused by the traditional physical sandblasting method. This not only improves the polishing quality but also maintains the integrity of the inner cavity of the blade, thereby extending the service life of the turbine blade and improving the reliability of the gas turbine.

[0072] 2. The present invention provides a method for polishing the inner cavity of a hollow blade. By finely proportioning the polishing solution, the controllability and accuracy of the polishing process are improved. It is applicable not only to large-sized turbine blades with complex inner cavity structures but also to blades of different shapes and sizes, including those with multiple cooling channels and cooling rib structures. This wide applicability enables the technical solution of the present invention to be widely applied to the manufacturing and repair processes of various gas turbine blades.

[0073] 3. The present invention provides a method for polishing the inner cavity of a hollow blade. By means of a designed polishing process and polishing solution, the traditional complex mechanical polishing, sandblasting or manual grinding steps are simplified. This method avoids the use of heavy machinery and complex operating equipment, thereby reducing the requirements for professional technology and equipment and making the polishing process more convenient and fast. The simplified process not only reduces the complexity of the operation but also shortens the production cycle and improves the production efficiency.

[0074] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0075] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover a non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising one..." does not exclude the existence of another identical element in the process, method, article or device comprising the element.

[0076] It should be noted that in the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

Claims

1. A method for polishing the inner cavity of a hollow blade, characterized in that: include: S1: using acid to remove oxides on the inner cavity surface of the hollow blade; S2: placing the outlet end of the polishing liquid pipeline at the airflow outlet end of the hollow blade, and delivering the polishing liquid to the inner cavity surface of the hollow blade through the outlet end of the polishing liquid pipeline by a pump; S3: placing the outlet end of the polishing liquid pipeline at the air flow inlet end of the hollow blade, and delivering the polishing liquid to the inner cavity surface of the hollow blade through the outlet end of the polishing liquid pipeline by a pump.

2. The method according to claim 1, characterized in that: The step S1 includes: The acid solution includes sulfuric acid with a concentration of 5%-8% and / or nitric acid with a concentration of 8%-10%.

3. The method according to claim 1, characterized in that: The step S1 comprises: The oxide on the inner cavity surface of the hollow blade is removed by immersing the hollow blade in the acid solution.

4. The method according to claim 3, characterized in that: Before step S1, the method further includes: The airflow outlet end and the airflow inlet end of the hollow blade are pre-shielded by using a peelable electroplating protective glue.

5. The method according to claim 1, characterized in that: The step S1 further includes: After removing the oxide on the inner cavity surface of the hollow blade, the surface of the hollow blade is cleaned with alcohol.

6. The method according to claim 1, characterized in that: include: The tenon portion of the hollow blade is the airflow inlet end; The tip of the hollow blade is the airflow outlet end.

7. The method according to claim 1, characterized in that: The step S2 further includes: The outlet end of the polishing liquid pipeline includes a main pipeline outlet and a plurality of auxiliary pipeline outlets.

8. The method according to claim 7, characterized in that: The step S2 further includes: If the length of the hollow blade is less than 400 mm, only the main pipeline outlet of the polishing liquid pipeline is arranged at the air flow outlet end to transport the polishing liquid; If the length of the hollow blade is greater than 400 mm, the main pipeline outlet of the polishing liquid pipeline is set at the air flow outlet end, and at least one auxiliary pipeline outlet is set, and the distance between the auxiliary pipeline outlet and the main pipeline outlet is greater than 400 mm. The number N of the auxiliary pipeline outlets is: Wherein, L is the length of the hollow blade, and N is rounded down to an integer.

9. The method according to claim 7, characterized in that: The step S2 further includes: The diameter of the main pipe outlet is 8mm-10mm, and the diameter of the secondary pipe outlet is 3mm-5mm.

10. The method according to claim 1, characterized in that: The step S2 includes: The material composition of the polishing liquid includes 48g / L-52g / L sulfuric acid, nitric acid, sulfuric acid and / or nitric acid, 48g / L-52g / L phosphoric acid, 4g / L-6g / L sodium methylenebisnaphthalene sulfonate, 1g / L-10g / L sodium dodecyl sulfate, 0.5g / L-1g / L hexamethylenetetramine, and the balance is water.

11. The method according to claim 1, characterized in that: The step S2 includes: The flow rate of the polishing liquid is 600ml / min-800ml / min, and the delivery time of the polishing liquid is 10min-15min.

12. The method according to claim 7, characterized in that: The step S3 further includes: If the length of the hollow blade is less than 400 mm, only the main pipeline outlet of the polishing liquid pipeline is arranged at the air flow inlet end to transport the polishing liquid; If the length of the hollow blade is greater than 400 mm, the main pipeline outlet of the polishing liquid pipeline is arranged at the air flow inlet end, and at least one auxiliary pipeline outlet is provided, and the distance between the auxiliary pipeline outlet and the main pipeline outlet is greater than 400 mm. The number N of the auxiliary pipeline outlets is: Wherein, L is the length of the hollow blade, and N is rounded down to an integer.

13. The method according to claim 1, characterized in that: The step S3 includes: The flow rate of the polishing liquid is 400ml / min-500ml / min, and the delivery time of the polishing liquid is 8min-12min.

14. The method according to claim 1, characterized in that: After step S3, the method further includes: The hollow leaves are rinsed with water for 8 min-10 min.

15. The method according to claim 1, characterized in that: After step S3, the method further includes: Compressed air is used to remove the residual water from the inner cavity and outer surface of the hollow blade.

16. The method according to claim 1, characterized in that: The step S3 includes: The inner cavity surface roughness of the hollow blade after polishing with the polishing liquid is 0.5 μm-1 μm.

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