Machining method for special-shaped cooling hole of turbine blade of gas turbine

Abstract

The invention relates to the technical field of special-shaped hole machining methods, and provides a gas turbine turbine blade special-shaped cooling hole machining method which comprises the following steps that S1, a bottom hole is machined in the position, where a special-shaped cooling hole needs to be formed, of a turbine blade; s2, a characteristic part with a required special-shaped cooling hole is machined in an additive manufacturing or casting mode, and the outer contour of the characteristic part is consistent with the contour of the bottom hole; and S3, the feature part is arranged in the bottom hole, and the feature part and the bottom hole are welded. According to the method, the feature part with the required special-shaped cooling hole is machined in an additive manufacturing or casting mode, then the feature part is welded in the bottom hole in the turbine blade, the situation that the special-shaped cooling hole is formed through a conventional process (namely electric spark machining or laser machining) is avoided, the limitation of the conventional process on the design of the cooling hole in the manufacturability aspect is broken through, and the machining efficiency is improved. And the hole pattern of the special-shaped cooling hole is widened, so that further improvement of the cooling effect becomes possible.

Description

Technical Field

[0001] The invention relates to the technical field of special-shaped hole processing methods, and in particular to a processing method for special-shaped cooling holes of turbine blades of a gas turbine. Background Art

[0002] Special-shaped cooling holes are widely used in the cooling design of gas turbine blades. Common special-shaped cooling holes include dustpan holes, C-shaped holes and cat-ear holes. Compared with circular cooling holes, special-shaped cooling holes have an expansion profile at the outlet, which enhances the coverage of the cooling air film on the wall surface, helps to form a more uniform and stable air film protective layer on the blade surface, and improves the cooling effect. At present, there are two main types of special-shaped hole processing for turbine blades: electrospark machining and laser machining. Among them, electrospark machining uses the principle of electrical corrosion and uses pulse discharge between the forming electrode and the blade to perform drilling processing; laser machining uses the interaction between the laser beam and the material to apply a beam with extremely high energy density to a small area to remove material for drilling processing.

[0003] However, neither EDM nor laser processing can process special-shaped holes whose profiles are non-monotonically expanded along the cold air direction, nor can they process special-shaped holes with curved surface transition between cylindrical holes and expansion sections. Of course, they cannot process special-shaped holes whose profile sections are non-monotonically expanded along the cold air direction and whose profile sections and cylindrical holes have curved surface transition (such as Figure 1 As shown in Figure 2 ). Therefore, due to the limitations of EDM and laser processing characteristics, the design of cooling holes for turbine blades is limited in terms of manufacturability, and it is difficult to further improve the cooling effect of turbine blades. Summary of the invention

[0004] The purpose of the present invention is to provide a method for processing special-shaped cooling holes of gas turbine turbine blades to overcome the limitations of electrospark machining and laser machining, broaden the hole type of the special-shaped cooling holes, and make it possible to further improve the cooling effect.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for processing special-shaped cooling holes of a gas turbine blade comprises the following steps:

[0007] S1. Process the bottom hole where the turbine blade needs to be provided with a special-shaped cooling hole;

[0008] S2. Using additive manufacturing or casting to process a feature part with the required special-shaped cooling hole, the outer contour of the feature part is consistent with the bottom hole contour;

[0009] S3. Install the feature part into the bottom hole and weld the two together.

[0010] Optionally, the bottom hole is a cylindrical hole.

[0011] Optionally, the bottom hole is a tapered hole.

[0012] Optionally, in step S3, the welding method is brazing.

[0013] Optionally, in step S1, the bottom hole is processed by drilling, electric spark machining or laser machining.

[0014] The technical solution of the present invention has at least the following advantages and beneficial effects:

[0015] 1. In the present invention, a feature part with the required special-shaped cooling hole is processed by additive manufacturing or casting, and then the feature part is welded to the bottom hole on the turbine blade, avoiding the use of conventional processes (i.e., electrospark machining or laser machining) to form special-shaped cooling holes, breaking through the limitations of conventional processes on cooling hole design in terms of manufacturability, broadening the hole type of special-shaped cooling holes, and making it possible to further improve the cooling effect.

[0016] 2. Since cracks are likely to occur near the irregular cooling holes during long-term operation of the gas turbine, the processing method provided by the present invention can be used to repair the blades by replacing the characteristic parts with irregular cooling holes alone, thus providing better maintainability. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 A process flow chart of a method for machining special-shaped cooling holes of turbine blades of a gas turbine provided by the present invention;

[0019] Figure 2 It is a special-shaped hole model in which the profile hole section expands non-monotonically along the cold air direction and the profile hole section and the cylindrical hole have a curved surface transition;

[0020] Figure 3 is a structural schematic diagram of the bottom hole;

[0021] Figure 4 It is a schematic diagram of the enlarged structure of the characteristic parts;

[0022] Figure 5 It is a structural schematic diagram of the combined welding of the characteristic part and the bottom hole;

[0023] Icons: 1-turbine blade, 2-feature part, 3-special-shaped cooling hole, 4-bottom hole. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0025] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0027] refer to Figure 1 A method for processing a special-shaped cooling hole of a gas turbine blade comprises the following steps:

[0028] S1. A bottom hole 4 is machined at a turbine blade 1 where a special-shaped cooling hole 3 is required. In practical applications, the specific machining method of the bottom hole 4 is not limited, and it may be drill machining, electric spark machining or laser machining. Of course, other methods may also be used to machine the bottom hole 4.

[0029] S2. Using additive manufacturing or casting to process a feature part 2 with the required special-shaped cooling hole 3, the outer contour of the feature part 2 is consistent with the contour of the bottom hole 4; it is worth noting that additive manufacturing is commonly known as 3D printing. Different from the traditional processing mode of removing, cutting and assembling raw materials, additive manufacturing is a "bottom-up" manufacturing method through material accumulation. This manufacturing method makes it possible to manufacture complex structural parts that were previously constrained by traditional manufacturing methods; casting adopts precision manufacturing, also called lost wax casting, which uses precise modeling methods (such as investment casting, ceramic mold casting, etc.) to obtain castings close to the final shape of the parts through fine process control;

[0030] In addition, the outer contour of the feature part 2 is consistent with the contour of the bottom hole 4, that is, the shape of the feature part 2 is set according to the shape of the bottom hole 4. The shape of the bottom hole 4 can be a cylindrical hole or a tapered hole. Preferably, the bottom hole 4 in this embodiment is a tapered hole. On this basis, the outer contour of the feature part 2 is a frustum. The frustum-shaped feature part 2 matches the tapered hole well, which is convenient for better positioning of the feature part 2.

[0031] S3. Install the feature part 2 into the bottom hole 4 and weld the two together. In practical applications, brazing is selected as the welding method. Brazing is a welding method that uses a brazing material with a lower melting point than the metal to be welded. After heating, it melts and relies on capillary action to fill the joint gap and diffuse with the parent material to achieve connection. During the brazing process, only the brazing material melts, and the metal to be welded (parent material) does not melt. The liquid brazing material enters the gap between the two welds with the help of wetting and capillary action, diffuses with the solid metal to achieve atomic bonding, and forms a strong connection.

[0032] As can be seen from the above, the present invention processes the characteristic part 2 with the required special-shaped cooling hole 3 by additive manufacturing or casting, and then welds the characteristic part 2 to the bottom hole 4 on the turbine blade 1, avoiding the use of conventional processes (i.e., electrospark machining or laser machining) to form the special-shaped cooling hole 3, breaking through the limitations of conventional processes on the design of cooling holes in terms of manufacturability, broadening the hole type of the special-shaped cooling hole 3, and making it possible to further improve the cooling effect.

[0033] In addition, it is worth mentioning that during the long-term operation stage of the gas turbine, cracks are likely to initiate in the area near the special-shaped cooling hole 3. By adopting the processing method provided by the present invention, the blade can be repaired by replacing the characteristic parts with special-shaped cooling holes alone, so the maintainability is better.

[0034] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for processing special-shaped cooling holes of gas turbine blades, characterized in that: The following steps are involved: S1. Process the bottom hole where the turbine blade needs to be provided with a special-shaped cooling hole; S2. Using additive manufacturing or casting to process a feature part with the required special-shaped cooling hole, the outer contour of the feature part is consistent with the bottom hole contour; S3. Install the feature part into the bottom hole and weld the two together.

2. The method for processing the special-shaped cooling holes of gas turbine blades according to claim 1, characterized in that: The bottom hole is a cylindrical hole.

3. The method for processing the special-shaped cooling holes of gas turbine blades according to claim 1, characterized in that: The bottom hole is a tapered hole.

4. The method for processing the special-shaped cooling holes of gas turbine blades according to claim 1, characterized in that: In the step S3, the welding method is brazing.

5. The method for processing the special-shaped cooling holes of gas turbine blades according to claim 1, characterized in that: In the step S1, the bottom hole is processed by drilling, electric spark machining or laser machining.

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