A method for fabricating film gas vents in turbine blades based on digital twin technology

Abstract

This invention belongs to the field of precision manufacturing technology and relates to a method for drilling film holes in turbine blades based on digital twin technology. The method first introduces modern measurement and digital twin technologies into the turbine blade drilling process. Then, by pre-setting easily image-recognizable structures such as pits and ribs on the inner and outer surfaces of the turbine blade casting blank, and comparing the theoretical values ​​of the microstructure shape and position at the hole edge with the actual values ​​represented by the digital twin model, high-precision correction of parameters such as the inner / outer position, spatial angle, and machining depth of the film holes is achieved, meeting the precision requirements of modern high-performance turbine blades for film hole machining. According to calculations, compared with previous methods, the drilling position tolerance can be reduced by 80%, thereby increasing blade service life by more than 20%. From a manufacturability perspective, this method increases the hole-making pass rate by more than 50%, thus improving overall economic efficiency.

Description

Technical Field

[0001] This invention belongs to the field of precision manufacturing technology and relates to a method for fabricating film pores in turbine blades based on digital twin technology. Background Technology

[0002] For turbine-type aero-engines and gas turbines, the temperature of the combustion gases far exceeds the temperature resistance limit of the metal materials used in the turbine blades, necessitating thermal protection or cooling measures. Typical measures include film cooling (FSV), which involves creating small holes on the blade surface and drawing cooling gas from inside the blade through these holes. The airflow adheres to the surface, isolating the blade from the combustion gases and achieving a strong cooling effect. Currently, cooled turbine blades typically require hundreds of film cooling holes with diameters ranging from φ0.2 to 0.8 mm on their surface. The design of these numerous film cooling holes must be individually optimized based on the blade shape, combustion gas flow pattern, and internal cavity structure, resulting in differences in parameters such as hole diameter, hole shape, and spatial angle. Because film cooling holes require high spatial and geometric precision, have small diameters, and are densely packed, they cannot be directly formed through casting. Typically, after the blade blank is cast, positioning surfaces are machined on the blade, and it is then positioned using a fixture. Subsequent secondary processing is performed using processes such as electrical discharge machining (EDM), electro-hydraulic beam drilling, and laser drilling. A typical existing drilling process is as follows: Figure 1 As shown.

[0003] The complex casting process of turbine blades and the difficulty in controlling their shape result in low precision and poor consistency in the blanks. This means that the theoretical three-dimensional coordinates and geometric parameters required for film cooling hole preparation may not be applicable to the actual blank. The meaning is as follows: Figure 2 As shown: The dashed line in the figure represents the theoretical surface of the turbine blade. After establishing a three-dimensional coordinate system based on the positioning surface on the fixture, the theoretically correct drilling point is located at point P outside the theoretical film gas hole, and its theoretical coordinates are (x... 外 ,y 外 ,z 外 When drilling, the drilling tool should be positioned at this point, and its axis angles should be set as the theoretical angle α between the air film hole axis and the Y-axis, and the theoretical angle β between the air film hole axis and the Z-axis. However, in actual operation, there are many factors that affect accuracy, such as:

[0004] 1. During the casting process, it is difficult for the blade core and wax model used to be completely consistent with the theoretical internal / external shape of the designed blade;

[0005] 2. During the cooling and solidification process, the blades will experience varying degrees of material shrinkage and thermal stress strain, which will ultimately lead to a certain degree of bending, torsion, and shrinkage deformation in the actual blades relative to the design values.

[0006] 3. After the blade is clamped on the drilling machine, there is a mismatch between the tenon positioning surface and the fixture, which causes an error when the machine is positioned at the air film hole.

[0007] 4. Errors still exist in the positioning and feeding processes of the machine tool itself.

[0008] The cumulative effect of the aforementioned errors leads to the theoretical deformation of the turbine blade surface. Figure 2 The solid line represents the actual profile of the turbine blade. At this point, the actual drilling point should be transformed into the actual external point P′ of the film cooling hole, and its actual coordinates should be changed to (x... 外 ′,y 外 ′,z 外 When drilling, the drilling tool should be positioned at this point, and its axis angle should be set as the actual angle α′ between the air film hole axis and the Y-axis, and the actual angle β′ between the air film hole axis and the Z-axis. If the above-mentioned error accumulation is ignored and processing is still carried out according to theoretical point positions and theoretical angles, the spatial position, spatial angle, drilling depth, and other parameters of the actually processed air film hole will be inconsistent with the expected target parameters, which is the main source of air film hole processing error.

[0009] The aforementioned machining errors not only reduce the cooling and strength performance of the film cooling holes, but can also lead to phenomena such as misaligned film cooling holes, overlapping film cooling holes, and backwall damage, as shown in Figure 3. Figure 3(a) shows a standard film cooling hole without machining errors. As shown in Figure 3(b), when the actual drilling position deviates from the theoretical position, misalignment of the film cooling hole will occur, and in severe cases, it will not be able to properly connect the inner and outer cavities of the blade. As shown in Figure 3(c), if the drilling position is accurate, but the actual drilling angle deviates from the theoretical value, the deviated film cooling hole will interfere with the surrounding film cooling holes, resulting in overlapping film cooling holes and significant stress concentration. As shown in Figure 3(d), during the drilling process, inaccurate depth calculations can cause excessive feed of the drilling tool, leading to further mismachining of the backwall after the film cooling hole is drilled, resulting in irreversible damage such as pits or penetrations on the backwall, i.e., backwall damage. All of the above machining errors will significantly reduce the performance and service life of turbine blades, and in severe cases, they must be scrapped, thus increasing manufacturing costs. Therefore, ensuring the positioning and forming geometry accuracy of the film cooling holes is crucial for improving turbine blade strength and engine performance. Summary of the Invention

[0010] To address the shortcomings of existing manufacturing processes in achieving high precision in the machining of film-forming holes in turbine blades, this invention provides a turbine blade drilling method based on digital twin technology. This method corrects the theoretical machining parameters of the film-forming holes by comparing the theoretical values ​​of the microstructure shape and position at the hole edge with the actual values ​​represented by the digital twin model. This improves machining accuracy, avoids misalignment, overlap, and backwall damage, enhances the structural strength of the turbine blade, and ultimately improves the overall performance of the turbine blade.

[0011] To achieve the above-mentioned effects, the present invention employs the following technical solution:

[0012] A method for drilling holes in turbine blades based on digital twin technology, the process of which is as follows: Figure 4 As shown, relative to Figure 1 The existing process shown differs mainly in that some microstructures for auxiliary positioning are pre-placed on the blade blank, and these structures are identified and located using digital twin technology before drilling. These structures are then used as a reference to correct the shape and position parameters of the film gas vents.

[0013] The specific meaning of the above process is as follows:

[0014] S1: The design and casting of turbine blades begins with the production of a ceramic core and wax film based on a turbine blade model with a hemispherical recess and smooth rib structure on the edge of the film gas hole. The blank is then manufactured, and a typical scheme is shown in Figure 5.

[0015] S1.1: On the outer surface of these blades, at the outlet of the air film vent, a hemispherical recess is arranged. The recess is formed by subtracting the blade from the bottom of a sphere, and the theoretical axis of the air film vent passing through the recess does not need to pass through the center of the sphere. On the inner surface of the blade, at the air film vent inlet, three types of structures are provided: annular ribs, serpentine ribs, and straight ribs. The rib structure protrudes from the inner surface of the blade cavity, and the cross-section of the protruding part is approximately semi-circular. The theoretical axis of the air film vent passing through the rib does not need to pass through the center of the circle.

[0016] For the inlet of the film cooling perforator, different types of rib structures can be selected based on the blade shape and the structure of the film cooling perforator. Among them, the annular rib, as shown in Figure 5, is typically located in a relatively narrow area on the inner surface of the blade's leading edge. Each rib encircles the blade cavity chordally, and multiple ribs are arranged radially at the inlet of each leading edge film cooling perforator. Depending on the blade structure design requirements, this type of rib can also be arranged in other areas of the blade. The main characteristic of this type of rib is that its axis is an approximately circular curve, hence the name "annular." In terms of application, this type of rib is mainly suitable for film cooling perforators as shown in Figure 6. The angle ∠η between the axis of this type of film cooling perforator and the combustion gas can be 60–90°, meaning the perforation tilt direction is approximately along the radial direction of the blade and perpendicular to the direction of combustion gas flow. Additionally, the angle ∠θ between the axis of the film cooling perforator and the wall surface can be 20–45°. Due to cooling requirements, these types of film cooling holes are typically densely arranged radially and chordally, allowing a single annular rib to intersect with multiple film cooling holes. For straight ribs, as shown in Figure 5, they are usually located on the back side of the blade, extending radially into the cooling air passage within the blade cavity. Depending on the blade structure design, these ribs can also be arranged in other areas of the blade. The main characteristic of this type of rib is that its axis is approximately a straight line along the radial direction of the blade, hence the name "straight rib." In application, this type of rib is mainly suitable for film cooling holes as shown in Figure 6. The angle ∠η between the axis of this type of film cooling hole and the combustion gas can be 0–25°, meaning the hole axis is approximately horizontal and approximately parallel to the direction of combustion gas flow. Multiple radially arranged film cooling holes in each row can share the same straight rib. For serpentine ribs, as shown in Figure 5, they are typically located on the blade basin side, with a meandering serpentine axis located on the surface of the cooling air passage within the blade cavity. Depending on the blade structure design, this type of rib can also be arranged in other areas of the blade. In terms of application, this type of rib is mainly suitable for film gas holes as shown in Figure 6. The angle ∠η between the axis of the film gas hole and the gas combustion gas can be 25° to 60°, that is, the axis of the hole is inclined, and the degree of inclination is between the two mentioned above. Multiple such film gas holes arranged radially can share the same serpentine rib. The intersection of the serpentine ribs should be selected at the part that is as perpendicular as possible to the axis of the film gas hole, and the rest of the rib can be omitted, so that a single serpentine rib becomes multiple inclined short ribs.

[0017] Figure 5, a cross-sectional view, further illustrates the typical structure of the recess and rib of the present invention. The main characteristic parameters of this microstructure are: the diameter of the film cooling hole φD; the smooth rib structure at the air inlet end of the film cooling hole, whose cross-sectional diameter is the theoretical diameter φd1 of the smooth rib cross-section, which can be 1.5 to 2.5D; the height of the rib structure protruding from the wall surface is the height h of the smooth rib protrusion, which can be 0.2 to 0.8D; the tangential distance between the theoretical point M of the rib center and the edge of the film cooling hole is the tangential distance L1 between the smooth rib protrusion and the edge of the film cooling hole, which can be 0.8D to 1.8D, and preferably 1.2D. Viewed from the wall surface, as shown in the K-direction view of Figure 5, the rib has a theoretical width u of the smooth rib, which can be 2 to 5D. For film cooling holes at other locations on the blade and using ribs of different shapes at the inlet, the design of the ribs can be the same as described above, but the specific values ​​can be different.

[0018] The hemispherical recess structure located at the outlet of the film air vent has a diameter equal to the theoretical diameter φd2, which can be 1.5–2.5D. The depth of the recess into the wall is the depth s, which can be 0.2–0.8D. The tangential distance between the theoretical center point W of the recess and the edge of the film air vent is the tangential distance L2 between the hemispherical recess and the edge of the film air vent, which can be 0.7D–1.3D, preferably D. Viewed from the wall's normal direction, as shown in the L-direction view in Figure 5, the diameter of the sectional circle formed by its intersection with the wall is the theoretical diameter φd3, which can be 1.1–2.5D. The blade wall thickness H is generally 0.8–3 mm. For film air vents at other locations on the blade with different inclination angles, the design of the vent recess can follow the same principle, but the specific values ​​may differ. By casting these pits and ribs onto the blades and using them in combination, a reference can be provided for correcting the actual position, angle, and depth of the drilled holes.

[0019] S1.2: After completing the casting structure design, the theoretical parameters for film cooling (FS) machining are designed and determined. The method is as follows: First, based on the combination and assembly of the theoretical models of the turbine blade's theoretical surface and the fixture, a coordinate system as shown in Figure 5 is established. As shown in Figure 5, the theoretical internal point Q of the film cooling hole is located in the model, and its three-dimensional coordinate theoretical value is calculated; the theoretical external point P of the film cooling hole is located in the model, and its three-dimensional coordinate theoretical value is calculated; the angle between the theoretical axis of the film cooling hole and the X-axis is the theoretical angle γ between the film cooling hole axis and the X-axis, or the angle between this axis and other coordinate axes is obtained using the same method; the distance between the two points is the theoretical depth t of the film cooling hole. These theoretical parameters are used for subsequent numerical correction and machining of the film cooling hole to cast the turbine blade blank.

[0020] S2: Machining of positioning surfaces. The cast blank is processed by grinding and other methods to remove some of the excess material and to machine positioning surfaces such as tenons for blade clamping.

[0021] S3: Clamping and positioning. Align the positioning surfaces of the blade tenon and other parts with the positioning surfaces of the fixture, and apply appropriate clamping force to fix the two together. The fixture should be the same as the one designed in S1 and have the same coordinate system, as shown in Figure 7.

[0022] S4: Acquisition and Position Correction of the Digital Twin Model. To correct the drilling position and angle, this invention first establishes a digital twin model of the actual blade's internal and external structure. Then, using this model as a comparison, the deviation between the actual model and the theoretical model is calculated as the basis for correction. To improve the accuracy of this process, for example, to reduce the impact of assembly errors between the tenon positioning surface and the fixture on the positioning of the film cooling hole, the clamped blank and the fixture are treated as a whole, and their digital twin models are acquired simultaneously. The feature surfaces in the fixture are set as reference planes, and a coordinate system is established for determining the subsequent scanning coordinates and calculation references.

[0023] S4.1: To obtain the digital twin model of the actual blade structure, firstly, optical scanning of the blade and fixture is performed to obtain a series of three-dimensional coordinate points, including the external concave surface of the blade. The external contour of the blade is then fitted, and its absolute position in the fixture coordinate system is obtained, as shown in the optical scanning route in Figure 7. Then, CT scanning is performed on the blade and fixture to obtain the three-dimensional coordinate points of the blade's internal shape, especially the convex rib surfaces in the internal cavity. The internal contour of the blade is then fitted, and its absolute position in the fixture coordinate system is obtained, as shown in the CT scanning route in Figure 7. For the two sets of three-dimensional coordinate points obtained by the two methods, firstly, their coordinates in the same coordinate system are used for mutual verification, and then computer programming language is used to remove abnormal noise points and capture and locate feature points based on the least squares method. Finally, a digital twin model of the blade containing internal and external surfaces and structures such as external concave surfaces and internal convex ribs is generated.

[0024] S4.2: As shown on the right side of Figure 7, the actual drilling parameters to be used can be calculated based on the previously obtained digital twin model of the actual blade, and then delivered to the next process. Depending on the data format and control method used by the drilling machine, the data provided can be in the following two ways:

[0025] 1. Actual absolute value: When the machine tool does not store the theoretical parameters for blade drilling, the complete set of drilling data generated based on the digital twin model of the actual blade can be directly delivered to the machine tool, including: the three-dimensional coordinates of the actual external point P′ of the film film hole, the three-dimensional coordinates of the actual internal point Q′ of the film film hole, the actual axis of the film film hole obtained by connecting the two points, the actual depth t′ of the film film hole and the actual angle with the coordinate system, such as the actual angle α′ between the film film hole axis and the Y-axis, the actual angle β′ between the film film hole axis and the Z-axis, and the actual angle γ′ between the film film hole axis and the X-axis, etc., for drilling.

[0026] 2. Theoretical value + correction value: If the machine tool has already stored the theoretical three-dimensional coordinates of the original theoretical internal point Q of the air film hole and the theoretical three-dimensional coordinates of the theoretical external point P of the air film hole, it is only necessary to provide the correction values ​​of the internal and external point coordinates of the air film hole shown on the right side of Figure 7 as coordinate adjustment values ​​to the machine tool, so that it can automatically correct to obtain the coordinates of the actual internal point Q′ and the actual external point P′ of the air film hole, and further calculate the position of the actual axis of the air film hole, the actual depth t′ of the air film hole, and the actual angles with the coordinate system, such as the actual angle α′ between the air film hole axis and the Y-axis, the actual angle β′ between the air film hole axis and the Z-axis, and the actual angle γ′ between the air film hole axis and the X-axis.

[0027] S5: Drilling. Fix the blade and fixture on the machine tool, and according to one of the two data processing methods mentioned above, first position the drilling tool to the actual external point P′ of the film vent, such as... Figure 8 As shown, based on the actual angle α′ between the air film hole axis and the Y-axis, the actual angle β′ between the air film hole axis and the Z-axis, and the actual depth t′ of the air film hole, the air film hole is made using processes such as electrical discharge drilling, electro-hydraulic beam drilling, and laser drilling. In this way, the accuracy of the air film hole can be significantly improved, especially ensuring its relative positional relationship with the pits, ribs, and other structures on the inner and outer surfaces of the blade, thereby ensuring the cooling and strength performance of the blade.

[0028] The present invention has the following beneficial effects and advantages:

[0029] 1. Effectively ensures the positioning accuracy of air film hole drilling.

[0030] This patented method first introduces modern measurement and digital twin technologies into the turbine blade drilling process. Then, by pre-setting easily image-recognizable structures such as pits and ribs on the inner and outer surfaces of the turbine blade casting blank, and comparing the theoretical values ​​of the microstructure shape and position at the hole edge with the actual values ​​represented by the digital twin model, high-precision correction of parameters such as the inner / outer position, spatial angle, and machining depth of the film cooling holes is achieved, meeting the precision requirements of modern high-performance turbine blades for film cooling hole machining. According to calculations, compared to previous methods, the drilling position tolerance can be reduced by 80%, thereby increasing blade lifespan by more than 20%. From a manufacturability perspective, this method also avoids scrap caused by drilling positioning deviations, increasing the drilling pass rate by more than 50%, thus improving overall economic efficiency.

[0031] 2. The use of a common fixture reduced blade mounting errors.

[0032] The method used in this patent requires blade mounting in multiple processes, including CT scanning, optical scanning, and hole drilling. To avoid coordinate system transformation errors, this patent proposes using the same common fixture for all processes. This fixture not only adapts to the needs of each process but also features positioning surfaces that can be recognized and used by all three processes to establish a common coordinate system. This improves the consistency and universality of the obtained blade internal / external surface coordinates across all processes. It avoids the accumulation of positional deviations between the positioning surfaces and different fixtures during frequent fixture changes and blade mounting, as well as errors caused by the transformation of three-dimensional coordinates between different coordinate systems, effectively guaranteeing improved positioning accuracy.

[0033] 3. The use of a hole-edge assisted positioning structure reduces the difficulty of obtaining the digital twin model.

[0034] This invention uses the pits / ribs on the outer / inner surface of the blade as reference objects for locating the film cooling air vents. These structures are tightly integrated with the air vents and can more directly reflect the changes in the actual inner / outer surface of the blade relative to the theoretical surface at the location of the air vent, providing an accurate reference object for the correction of the air vents. These structures are relatively large in size compared to the air vents and have obvious geometric features compared to the blade's curved surface, making it easy to accurately capture their size and positional characteristics during CT / optical scanning. For the correction of the air vent location, only these features are needed, and other parts of the blade's digital twin model that are difficult to obtain accurately (such as the shape of the internal channels, holes, and wall thickness) can be ignored. This significantly reduces the difficulty of measurement and modeling, improves work efficiency, and ensures the accuracy of the air vent location. Attached Figure Description

[0035] Figure 1 For the existing drilling process flowchart;

[0036] Figure 2 This diagram illustrates the generation of machining errors in film venting.

[0037] Figure 3(a) shows the standard air film pore diagram;

[0038] Figure 3(b) shows the misaligned air film pores;

[0039] Figure 3(c) shows the overlapping air film pores;

[0040] Figure 3(d) shows the damage to the dorsal wall;

[0041] Figure 4 This is a flowchart of the machining process for film cooling holes in turbine blades based on digital twin technology.

[0042] Figure 5(a) is a front view of a turbine blade with a perforated edge microstructure;

[0043] Figure 5(b) is a rear view of a turbine blade with a perforated edge microstructure;

[0044] Figure 5(c) is a right view of a turbine blade with a perforated edge microstructure;

[0045] Figure 5(d) is a cross-sectional view of the turbine blade with perforated edge microstructure;

[0046] Figure 5(e) is a cross-sectional view of the turbine blade with perforated edge microstructure;

[0047] Figure 5(f) is a K-axis view of a turbine blade with a perforated edge microstructure;

[0048] Figure 5(g) is an L-direction view of a turbine blade with a perforated edge microstructure;

[0049] Figure 5(h) is a three-dimensional coordinate system diagram of a turbine blade with a perforated edge microstructure;

[0050] Figure 6(a) shows the air film pore diagram applicable to annular ribs;

[0051] Figure 6(b) shows the air film pore diagram applicable to straight convex ribs;

[0052] Figure 6(c) shows the air film pore diagram applicable to serpentine ribs;

[0053] Figure 7(a) shows the three-dimensional coordinate system diagram of an actual turbine blade with a perforated edge microstructure;

[0054] Figure 7(b) shows the acquisition and use of the digital twin model of the turbine blade;

[0055] Figure 8 This is a diagram of the punching process, corrected based on a digital twin model.

[0056] Figure 9(a) is a cross-sectional view of a turbine blade with a perforated edge microstructure;

[0057] Figure 9(b) is a CC cross-sectional view of the air film pore structure with pits on the outer surface and ribs on the inner surface;

[0058] Figure 9(c) is a K-direction view of the air film pore structure with pits on the outer surface and ribs on the inner surface;

[0059] Figure 9(d) is an L-view of the air film pore structure with pits on the outer surface and ribs on the inner surface;

[0060] Figure 10(a) is a cross-sectional view of a turbine blade with a perforated edge microstructure.

[0061] Figure 10(b) is a CC cross-sectional view of the air film pore structure with pits on the outer surface;

[0062] Figure 10(c) is an L-view of the air film pore structure with pits on the outer surface;

[0063] Figure 11(a) is a cross-sectional view of a turbine blade with a perforated edge microstructure.

[0064] Figure 11(b) is a CC cross-sectional view of the air film pore structure with protruding ribs on the inner surface;

[0065] Figure 11(c) is a K-direction view of the air film pore structure with protruding ribs on the inner surface.

[0066] In the figure: 1. Theoretical surface of turbine blade; 2. Theoretical external point P of film cooling hole; 3. Theoretical angle α between film cooling hole axis and Y-axis; 4. Theoretical angle β between film cooling hole axis and Z-axis; 5. Actual surface of turbine blade; 6. Actual external point P′ of film cooling hole; 7. Actual angle α′ between film cooling hole axis and Y-axis; 8. Actual angle β′ between film cooling hole axis and Z-axis; 9. Fixture; 10. Hole-making tool; 11. Hemispherical recess; 12. Theoretical axis of film cooling hole; 13. Annular rib; 14. Serpentine rib; 15. Straight rib; 16. Angle ∠η between film cooling hole axis and combustion gas; 17. Angle ∠θ between film cooling hole axis and wall surface; 18. Diameter of film cooling hole φD; 19. Theoretical diameter of smooth rib section φd1; 20. Height h of smooth rib. 21. Theoretical point M at the center of the rib; 22. Tangential distance L1 between the rib protrusion and the edge of the film film aperture; 23. Theoretical width u of the rib; 24. Theoretical diameter φd2 of the hemispherical pit; 25. Depth s of the hemispherical pit; 26. Theoretical point W at the center of the pit; 27. Tangential distance L2 between the hemispherical pit and the edge of the film film aperture; 28. Theoretical diameter φd3 of the truncated circle of the hemispherical pit; 29. ​​Blade wall thickness H; 30. Theoretical internal point Q of the film film aperture; 31. Theoretical angle γ between the axis of the film film aperture and the X-axis; 32. Theoretical depth t of the film film aperture; 33. Actual internal point Q′ of the film film aperture; 34. Actual axis of the film film aperture; 35. Actual angle γ′ between the axis of the film film aperture and the X-axis; 36. Coordinate correction value (Δx) of the internal point of the film film aperture. 内 ,Δy 内 ,Δz 内 ), Correction value of external point coordinates of 37 air film vents (Δx) 外 ,Δy 外 ,Δz 外 ), 38 Actual depth of air film hole t′, 39 Actual diameter of hemispherical pit φd2′, 40 Actual diameter of hemispherical pit sectional circle φd3′, 41 Actual position of pit center W′, 42 Actual diameter of smooth rib section φd1′, 43 Actual width of smooth rib u′, 44 Actual position of rib center M′. Detailed Implementation

[0067] Case 1

[0068] To address the shortcomings of existing manufacturing processes in achieving high precision in the machining of film cooling holes for turbine blades, this invention provides a turbine blade drilling method based on digital twin technology. This method compares the theoretical values ​​of the microstructure shape and position at the hole edge with the actual values ​​represented by the digital twin model, thereby correcting the theoretical machining parameters of the film cooling holes. This improves the machining accuracy of the film cooling holes, avoids misalignment, overlap, and backwall damage that occur during film cooling hole machining, enhances the structural strength of the turbine blade, and ultimately improves its overall performance. The specific correction steps are as follows:

[0069] 1. For the theoretical external point P2 of the film cooling hole on the theoretical surface 1 of the turbine blade, based on Figure 8 The theoretical values ​​of the three-dimensional coordinates of the three-dimensional coordinate system shown are (2.030, 10.438, 3.239); the theoretical values ​​of the three-dimensional coordinates of the corresponding point Q30 inside the film vent are (3.035, 10.357, 2.197); the straight line connecting these two points is the theoretical axis 12 of the film vent. The calculated theoretical angle γ31 between the film vent axis and the X-axis is 46.122°, the theoretical angle α3 between the film vent axis and the Y-axis is 86.798°, and the theoretical angle β4 between the film vent axis and the Z-axis is 44.057°; the theoretical depth t32 of the film vent between the two points is calculated to be 1.450 mm.

[0070] 2. Perform optical scanning on the external pits of the blade, such as... Figure 9d As shown, the obtained 3356 three-dimensional coordinate points are stored in the coordinate matrix G, that is:

[0071]

[0072] The internal ribs of the blade will then be subjected to a CT scan, such as... Figure 9c As shown, the 1825 obtained 3D coordinate points are stored in coordinate matrix C, that is:

[0073]

[0074] Each row of the G and C matrices contains the X, Y, and Z coordinates of a point, in mm.

[0075] 3. Based on the coordinate matrix G, a numerical algorithm was used to fit the contour of the pit, and the feature parameters φd2′39 (actual diameter of the hemispherical pit) and φd3′40 (actual diameter of the tangent circle of the hemispherical pit) were extracted, as well as the three-dimensional coordinates (1.675, 9.366, 2.127) of the actual point W′41 at the center of the pit. Figure 9bAs shown in d. The three-dimensional coordinates of the actual external point P′6 of the air-supported membrane vent (1.925, 10.352, 3.290) were then calculated. After obtaining the coordinates of P′, the correction value (Δx) for the external point coordinates of the air-supported membrane vent can be calculated. 外 ,Δy 外 ,Δz 外 )37 is (-0.105, -0.086, 0.051).

[0076] 4. Based on the coordinate matrix C, a numerical algorithm is used to fit the profile of the rib, and the feature parameters φd1′42 (actual diameter of the smooth rib section) and u′43 (actual width of the smooth rib) and the three-dimensional coordinates (2.951, 11.266, 1.930) of the actual center point M′44 of the rib are extracted. Figure 9b As shown in c. The three-dimensional coordinates of the actual point Q′33 inside the air-film vent (2.883, 10.3147, 2.334) were then calculated. After obtaining the coordinates of Q′, the correction value (Δx) for the coordinates of the point inside the air-film vent can be calculated. 内 ,Δy 内 ,Δz 内 )36 is (-0.152, -0.042, 0.137).

[0077] 5. Connect the actual external point P′6 of the air film vent with the actual internal point Q′33 of the air film vent. This is the actual axis 34 of the air film vent. The actual angle γ′35 between the air film vent axis and the X-axis is 44.962°, the actual angle α′7 between the air film vent axis and the Y-axis is 88.421°, and the actual angle β′8 between the air film vent axis and the Z-axis is 45.082°. The actual depth t′38 of the air film vent between the two points is 1.354 mm.

[0078] 6. Deliver the above calculation results to the machine tool for drilling.

[0079] Case 2

[0080] As shown in Figure 10, when constrained by structural or manufacturing cost limitations, a hemispherical recess can be used only on the outer surface of the blade at the air film aperture outlet, while the inner surface of the blade, i.e., the inlet of the air film aperture, remains a smooth surface. The difference between the theoretical and actual parameters of the recess is used to correct the shape and position of the air film aperture. This approach can sacrifice some hole-making accuracy in exchange for reduced manufacturing costs. The specific steps of the correction are as follows:

[0081] 1. For the theoretical external point P2 of the film cooling hole on the theoretical profile of the 1-turbine blade, based on Figure 8The theoretical values ​​of the three-dimensional coordinates of the three-dimensional coordinate system shown are (3.130, 12.424, 5.996); the theoretical values ​​of the three-dimensional coordinates of the corresponding point Q30 inside the film vent are (3.653, 11.562, 4.794); the straight line connecting these two points is the theoretical axis 12 of the film vent. The calculated theoretical angle γ31 between the film vent axis and the X-axis is 70.516°, the theoretical angle α3 between the film vent axis and the Y-axis is 56.705°, and the theoretical angle β4 between the film vent axis and the Z-axis is 39.966°; and the theoretical depth t32 of the film vent between the two points is 1.569 mm.

[0082] 2. Perform optical scanning on the external pits of the blade, such as... Figure 10c As shown, the 1378 obtained 3D coordinate points are stored in the coordinate matrix G, that is:

[0083]

[0084] Each row of matrix G contains the X, Y, and Z coordinates of a point, in mm.

[0085] 3. Based on the coordinate matrix G, a numerical algorithm was used to fit the contour of the pit, and the feature parameters φd2′39 (actual diameter of the hemispherical pit) and φd3′40 (actual diameter of the tangent circle of the hemispherical pit) were extracted, as well as the three-dimensional coordinates (3.144, 11.109, 5.977) of the actual point W′41 at the center of the pit. Figure 10b As shown in c. The three-dimensional coordinates of the actual external point P′6 of the air-supported membrane vent (3.387, 12.278, 5.832) were then calculated. After obtaining the coordinates of P′, the correction value (Δx) for the external point coordinates of the air-supported membrane vent can be calculated. 外 ,Δy 外 ,Δz 外 )37 is (0.257, -0.146, -0.164).

[0086] 4. Because the blade cavity lacks an auxiliary positioning structure, the internal point Q30 of the film pore theory is used as the positioning point, with coordinates (3.653, 11.562, 4.794).

[0087] 5. Connect the actual external point P′6 of the air film vent with the theoretical internal point Q30 of the air film vent, which is the actual axis 34 of the air film vent. The actual angle γ′35 between the air film vent axis and the X-axis is 70.085°, the actual angle α′7 between the air film vent axis and the Y-axis is 56.283°, the actual angle β′8 between the air film vent axis and the Z-axis is 36.316°, and the actual depth t′38 of the air film vent between the two points is 1.289 mm.

[0088] 6. Deliver the above calculation results to the machine tool for drilling.

[0089] Case 3

[0090] As shown in Figure 11, when constrained by structural or manufacturing cost limitations, smooth ribs can be used only on the inner surface of the blade at the inlet of the film cooling hole, while the outer surface of the blade, i.e., the outlet of the film cooling hole, remains smooth. The difference between the theoretical and actual parameters of the ribs is used to correct the shape and position of the film cooling hole. This approach can sacrifice some hole-making accuracy in exchange for reduced manufacturing costs. The specific steps of the correction are as follows:

[0091] 1. For the theoretical external point P2 of the film cooling hole on the theoretical surface 1 of the turbine blade, based on Figure 8 The theoretical values ​​of the three-dimensional coordinates of the three-dimensional system shown are (5.560, 11.364, 3.442); the theoretical values ​​of the three-dimensional coordinates of the corresponding theoretical internal point Q30 of the film pore are (5.470, 10.146, 2.158); the straight line connecting these two points is the theoretical axis 12 of the film pore. The calculated theoretical angle γ31 between the film pore axis and the X-axis is 87.098°, the theoretical angle α3 between the film pore axis and the Y-axis is 46.593°, and the theoretical angle β4 between the film pore axis and the Z-axis is 43.554°; the theoretical depth t32 of the film pore between the two points is calculated to be 1.773 mm.

[0092] 2. Perform a CT scan on the internal ribs of the blade, such as... Figure 11c As shown, the 1642 obtained 3D coordinate points are stored in coordinate matrix C, that is:

[0093]

[0094] Each row of matrix C contains the X, Y, and Z coordinates of a point, in mm.

[0095] 3. Because the outer surface of the blade lacks an auxiliary positioning structure, the external point P2 of the air film pore theory is used as the positioning point, with coordinates (5.560, 11.364, 3.442).

[0096] 4. Based on the coordinate matrix C, a numerical algorithm is used to fit the profile of the rib, and the feature parameters φd1′42 (actual diameter of the smooth rib section) and u′43 (actual width of the smooth rib) and the three-dimensional coordinates (6.328, 11.366, 1.957) of the actual center point M′44 of the rib are extracted. Figure 11b As shown in Figure c. The three-dimensional coordinates of the actual point Q′33 inside the air-film vent (5.139, 10.615, 2.183) were then calculated. After obtaining the coordinates of Q′, the correction value (Δx) for the coordinates of the point inside the air-film vent can be calculated. 内,Δy 内 ,Δz 内 )36 is (-0.331, 0.469, 0.025).

[0097] 5. Connect the theoretical external point P2 of the air film vent with the actual internal point Q′33 of the air film vent, which is the actual axis 34 of the air film vent. The actual angle γ′35 between the air film vent axis and the X-axis is 73.971°, the actual angle α′7 between the air film vent axis and the Y-axis is 60.580°, and the actual angle β′8 between the air film vent axis and the Z-axis is 34.297°; and the actual depth t′38 of the air film vent between the two points is 1.524 mm.

[0098] 6. Deliver the above calculation results to the machine tool for drilling.

Claims

1. A method for drilling holes in turbine blades based on digital twin technology, characterized in that, The steps are as follows: S1: The design and casting of turbine blades begins with the production of a ceramic core and wax film based on a turbine blade model with a hemispherical recess and smooth rib structure on the edge of the film gas hole, and the production of the blank is completed. S1.1: At the outlet of the air film hole on the outer surface of the blade, a hemispherical recess (11) is arranged, and the hemispherical recess (11) passes through the theoretical axis (12) of the air film hole of the recess; on the inner surface of the blade, at the inlet of the air film hole, there are three types of structures: annular rib (13), serpentine rib (14), and straight rib (15); the three types of rib structures protrude from the inner surface of the blade cavity, the cross-section of the protruding part is approximately semi-circular, and passes through the theoretical axis (12) of the air film hole of the rib; S1.2: After completing the casting structure design, design and determine the theoretical parameters for film cooling. The method is as follows: First, based on the combination and assembly of the theoretical models of the turbine blade theoretical surface (1) and the fixture (9), establish a coordinate system; locate the theoretical internal point Q (30) of the film cooling hole in the model, and statistically calculate its three-dimensional coordinate theoretical value (x 内 ,y 内 ,z 内 In the model, the theoretical external point P(2) of the air film pore is located, and its theoretical three-dimensional coordinates are (x... 外 ,y 外 ,z 外 ); The angle between the theoretical axis (12) of the film vent and the X-axis is the theoretical angle γ (31) between the film vent axis and the X-axis, or the angle between the axis and other coordinate axes can be obtained by the same method; The distance between the two points is the theoretical depth t (32) of the film vent; These theoretical parameters are used for subsequent numerical correction and machining of the film vent, and the turbine blade blank is cast. S2: Machining of the positioning surface: The cast blank is ground to remove some of the excess material and machine the tenon positioning surface for blade clamping. S3: Clamping and positioning. Match the blade tenon positioning surface with the fixture positioning surface and apply appropriate clamping force to fix the two together. The fixture should be the same as the one designed in S1 and have the same coordinate system. S4: Acquisition and Point Correction of Digital Twin Model. First, a digital twin model is established for the actual internal and external structure of the blade. Then, using this model as a comparison, the deviation between the model and the theoretical model is calculated as the basis for correction. The specific operation is as follows: S4.1 For obtaining the digital twin model of the actual blade structure, firstly, optical scanning of the outer surface of the blade and fixture is performed to obtain a series of three-dimensional coordinate points, including the outer concave surface of the blade, and the outer contour of the blade is fitted, as well as its absolute position in the fixture coordinate system; then, CT scanning is performed on the blade and fixture to obtain the three-dimensional coordinate points of each rib surface in the inner cavity of the blade, and the inner contour of the blade is fitted, as well as its absolute position in the fixture coordinate system; for the two sets of three-dimensional coordinate points obtained by the two methods, firstly, their coordinates in the same coordinate system are used as mutual verification based on the common outer surface of the two, and then computer programming language is used to remove abnormal noise points and capture and locate feature points based on the least squares method, finally generating a digital twin model of the blade containing the inner and outer surfaces and the outer concave and inner rib structures. S4.

2. Based on the obtained digital twin model of the actual blade, calculate the actual drilling parameters that should be used and deliver them to the next process. S5: Drilling; Fix the blade and fixture on the machine tool. First, position the drilling tool (10) at the actual external point P′ (6) of the air film hole. Then, based on the actual angle α′ (7) between the air film hole axis and the Y axis, the actual angle β′ (8) between the air film hole axis and the Z axis, and the actual depth t′ (38) of the air film hole, use electrical discharge drilling, electro-hydraulic beam drilling, and laser drilling processes to make holes in the air film hole.

2. The turbine blade drilling method based on digital twin technology as described in claim 1, characterized in that, S4.2, depending on the data format and control method used by the drilling machine, provides data in the following two ways:

1. Actual absolute value: When the machine tool does not store the theoretical parameters for blade drilling, the complete set of drilling data generated based on the digital twin model of the actual blade will be directly delivered to the machine tool, including: the three-dimensional coordinates (x, y, x) of the actual external point P′(6) of the film cooling hole. 外 The three-dimensional coordinates (x_inner, y_inner, z_inner) of the actual internal point Q′(33) of the air film hole, the actual axis (34) of the air film hole obtained by connecting the two points, the actual depth t′(38) of the air film hole and the actual angle with the coordinate system are used for hole making; 2. Theoretical value + correction value: When the machine tool has already stored the theoretical values ​​of the three-dimensional coordinates (x inside, y inside, z inside) of the original theoretical internal point Q(30) of the air film hole, and the theoretical values ​​of the three-dimensional coordinates (x outside, y outside, z outside) of the theoretical external point P(2) of the air film hole, it is only necessary to add the correction value (Δx) of the coordinates of the internal point of the air film hole. 内 ,Δy 内 ,Δz 内 (36) Correction value for the coordinates of the external points of the air film vent (Δx) 外 ,Δy 外 ,Δz 外 (37) is delivered to the machine tool as a coordinate adjustment amount, allowing it to correct itself to obtain the coordinates (x) of the actual internal position Q′(33) of the air film hole. 内 ′,y 内 ′,z 内 The coordinates (x) of the actual external location P′(6) of the air film vent are as follows: 外 ′,y 外 ′,z 外 ′), and further calculate the position of the actual axis (34) of the air film hole, the actual depth t′ (38) of the air film hole and the actual angle with the coordinate system.

3. A turbine blade drilling method based on digital twin technology as described in claim 1 or 2, characterized in that, In S1.1, the annular rib (13) is applicable under the following conditions: the angle ∠η (16) between the axis of the gas film hole and the gas is 60 to 90°, that is, the inclination direction of the hole is approximately along the radial direction of the blade and perpendicular to the gas flow direction. In addition, the angle ∠θ (17) between the axis of the gas film hole and the wall is 20 to 45°. Due to the need for cooling, this type of gas film hole is usually arranged very densely in the radial and chordal directions, so a single annular rib intersects with multiple gas film holes.

4. A turbine blade drilling method based on digital twin technology as described in claim 1 or 2, characterized in that, In S1.1, the straight rib (15) is applicable under the following conditions: the angle ∠η (16) between the axis of the gas film hole and the gas is 0 to 25°, that is, the direction of the hole axis is approximately horizontal and approximately parallel to the direction of gas flow; multiple such gas film holes arranged radially in each column share the same straight rib (15).

5. A method for drilling holes in turbine blades based on digital twin technology as described in claim 1 or 2, characterized in that, In S1.1, the serpentine rib (14) is applicable under the following conditions: the angle ∠η (16) between the axis of the gas film hole and the gas is 25 to 60°, that is, the direction of the hole axis is inclined, and the degree of inclination is between the two mentioned above; multiple such gas film holes arranged radially share the same serpentine rib (14).

6. A method for drilling holes in turbine blades based on digital twin technology as described in claim 1 or 2, characterized in that, The diameter of the cross-section of any one of the rib structures, namely the annular rib (13), the serpentine rib (14), and the straight rib (15), is 1.5 to 2.5D, which is the theoretical diameter of the smooth rib cross-section φd1 (19); the height of the rib structure protruding from the wall is 0.2 to 0.8D, which is the height of the smooth rib protrusion h (20); the tangential distance between the theoretical point M (21) at the center of the rib and the edge of the air film hole is 0.8D to 1.8D, which is the tangential distance L1 (22) between the protrusion of the smooth rib and the edge of the air film hole.

7. A turbine blade drilling method based on digital twin technology as described in claim 1 or 2, characterized in that, The hemispherical recess structure located at the outlet of the air film hole has a diameter of 1.5 to 2.5D, which is the theoretical diameter of the hemispherical recess φd2 (24); the depth of the recess into the wall of the hemispherical recess is 0.2 to 0.8D, which is the recess depth s (25); the tangential distance between the theoretical point W (26) at the center of the recess and the edge of the air film hole is 0.7D to 1.3D, which is the tangential distance L2 (27) between the hemispherical recess and the edge of the air film hole; and the diameter of the sectional circle formed by its intersection with the wall surface when viewed from the normal direction is 1.1 to 2.5D, which is the theoretical diameter of the sectional circle of the hemispherical recess φd3 (28).

8. The turbine blade drilling method based on digital twin technology as described in claim 6, characterized in that, The tangential distance between the theoretical point M(21) at the center of the convex rib and the edge of the air film hole is 1.2D, which is the tangential distance L1(22) between the convex rib and the edge of the air film hole.

9. The turbine blade drilling method based on digital twin technology as described in claim 7, characterized in that, The tangential distance between the theoretical point W(26) at the center of the pit and the edge of the air film hole is D, and the tangential distance L2(27) between the hemispherical pit and the edge of the air film hole is D; the blade wall thickness H(29) is 0.8~3mm.

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