Adaptive processing method for high-speed electric spark gas film cooling hole of multi-turbine blade

Abstract

A kind of multi-turbine blade high-speed electric spark gas film cooling hole adaptive processing method, by measuring turbine blade blade body outer contour to obtain actual point cloud model and calculate the nonlinear matching relationship between each point of ideal blade grid model, then through the mapping method of gas film cooling hole position and direction, the position and direction of designed gas film cooling hole are converted to actual point cloud space, and processing code in high-speed electric spark processing machine tool coordinate system is generated after coordinate system transformation, so that the gas film hole processing error caused by the contour error and clamping error of multi-turbine blade is reduced.The present application is based on the contour error and clamping error of each multi-turbine blade to adaptively adjust, and the machining precision of high-speed electric spark small hole machining can be significantly improved.

Description

Technical Field

[0001] This invention relates to a technology in the field of aerospace manufacturing, specifically an adaptive machining method for film cooling holes of multi-stage turbine blades in aero-engines that can compensate for clamping and contour errors. Background Technology

[0002] The geometric accuracy of cooling holes, including position and orientation accuracy, significantly affects film cooling efficiency. The geometric accuracy of machining film cooling holes is affected by two types of errors: casting profile errors of the turbine blades and positional errors caused by clamping. Therefore, directly machining cooling holes based solely on an ideal model will lead to significant geometric deviations. Furthermore, the casting profile errors of each blade are not consistent. Therefore, it is necessary to adjust the machining position and orientation of each hole for each blade. This adjustment of position and orientation is generally performed by a skilled operator. However, manual adjustment is not only inefficient but also prone to errors. Therefore, to achieve automated machining of cooling holes, it is necessary to compensate for clamping and casting profile errors. Summary of the Invention

[0003] To address the aforementioned shortcomings of existing technologies, this invention proposes an adaptive machining method for high-speed EDM film cooling holes in multi-stage turbine blades. This method adaptively adjusts the machining based on the contour and clamping errors of each multi-stage turbine blade, significantly improving the machining accuracy of high-speed EDM small hole machining.

[0004] This invention is achieved through the following technical solution:

[0005] This invention relates to an adaptive machining method for high-speed EDM film cooling holes in multi-stage turbine blades. The method involves measuring the outer contour of the turbine blade to obtain an actual point cloud model and calculating the nonlinear matching relationship between each point and the ideal blade mesh model. Then, using a mapping method for the position and orientation of the film cooling holes, the designed positions and orientations are transformed into the actual point cloud space. After coordinate system transformation, machining codes are generated in the coordinate system of the high-speed EDM machine tool, thereby reducing machining errors in the film cooling holes caused by contour errors and clamping errors in the multi-stage turbine blades.

[0006] The aforementioned nonlinear matching refers to: using an approximate rigid deformation algorithm to process the ideal blade mesh, transforming it into an intermediate mesh to fit the actual point cloud model; then using a mesh normal growth algorithm to transform the intermediate mesh into a target mesh so that the distance between it and the actual point cloud model is minimized, thereby completing the matching.

[0007] The aforementioned approximate rigid deformation algorithm refers to a nonlinear mesh deformation that minimizes mesh deformation energy while ensuring local rigidity during mesh deformation. Specifically: Where: E(X) ′X represents the deformation energy of the source mesh. ′ Let M be the set of spatial coordinates of all points on the source grid, and let x be the set of coordinates of all points on the source grid. ′ Let x be the spatial coordinates of a point on the source grid, x be the spatial coordinates of a point on the target point cloud, N(i) be the set of indices of all neighboring points of the i-th point, and C be the spatial coordinates of a point on the target point cloud. i It includes point x i x corresponding to N(i) N(i) The set of C i ′ contains x i x′ corresponding to N(i) N(i) The set of E(C) i C i ′)=∑ j∈N(i) ω ij |(x i ′-x j ′)-R i (x i -x j )| 2 R is the deformation energy of the i-th point and its neighborhood. i Let ω be the rotation matrix corresponding to the i-th point to be optimized. i This is the weight of the deformation energy at each point on the source mesh, typically set to 1. The weight of the line connecting the i-th point and its neighboring j-th point is the optimized X. ′ The corresponding grid is the middle grid.

[0008] The aforementioned mesh normal growth algorithm refers to an algorithm that, by simulating the growth phenomenon in nature, moves each vertex along its corresponding normal vector direction to minimize the distance between the transformed intermediate mesh and the target point cloud. Specifically: Where: f(d) is the average distance between the intermediate grid and the target point cloud, d is the distance to be optimized, m is the number of points in the grid, and y i Let x be the coordinate of the i-th point in the target point cloud. i Let n be the coordinates of the i-th point in the middle grid. i Let be the direction of the normal vector of the i-th point in the middle grid.

[0009] The method for mapping the location and orientation of air film cooling holes refers to: after searching for the triangular mesh cell closest to the location of the air film cooling hole in the ideal mesh, determining the mapping point of the air film cooling hole in the found ideal mesh triangular cell through the vertical mapping method, and locating the corresponding cell on the target mesh obtained after nonlinear matching of the triangular cell; then, using the local coordinate system mapping method, obtaining the corresponding position of the air film cooling hole in the mesh obtained by nonlinear matching, thereby achieving the conversion of the location and orientation of the air film cooling hole to the target mesh space.

[0010] The vertical mapping refers to: drawing a perpendicular line from the air film vent to the plane of the triangular mesh cell, intersecting the triangular mesh cell at a single point. This intersection point is the mapping point of the air film vent on the triangular mesh cell.

[0011] The local coordinate system mapping refers to the following steps: First, establishing local coordinate systems for the ideal mesh triangular element closest to the film cooling vent and the corresponding triangular element of the target mesh. Using these local coordinate systems, the ideal triangular element is mapped from three-dimensional space to two-dimensional parameter space, establishing a correspondence between the triangular elements in the two-dimensional parameter space and the triangular elements in the target mesh space. Then, based on the mapping points obtained in the vertical mapping step, the coordinates of the film cooling vent in the two-dimensional parameter space are determined. Finally, according to the correspondence between the triangular elements in the two-dimensional parameter space and the triangular elements in the target mesh space, the film cooling vent in the two-dimensional parameter space is transformed to the target mesh space, thereby realizing the transformation of the film cooling vent location and orientation from the ideal mesh space to the target mesh space.

[0012] This invention relates to a system for implementing the above-mentioned method, comprising: a five-axis laser measuring machine tool, a nonlinear point cloud matching calculation module, a hole position and orientation mapping module, and a film drying hole machining code generation module. The five-axis laser measuring machine tool integrates a laser measuring instrument and a five-axis linkage machine tool, used for laser scanning of the outer contours of the multi-stage turbine blade to be machined, i.e., the blade body and upper and lower edge plates, to obtain point cloud information. The nonlinear point cloud matching calculation module performs nonlinear matching based on the laser-measured point cloud information and an ideal mesh model to obtain the target mesh closest to the point cloud. The hole position and orientation mapping module utilizes the relationship between the ideal mesh model and the target mesh to transform the film drying hole positions in the ideal mesh model, obtaining the spatial coordinates of the film drying hole positions in the target mesh. The film drying hole machining code generation module converts the film drying hole positions to the machining machine space based on the spatial coordinates of the film drying hole positions in the target mesh and the conversion relationship from the target mesh space to the machining machine space, thereby obtaining the EDM (Electrical Discharge Machining) code. Technical effect

[0013] This invention uses laser measurement technology to obtain the actual point cloud model of a multi-stage turbine blade and a nonlinear matching method to establish a mapping relationship between the ideal design mesh and the actual point cloud. This allows for the determination of the optimal machining position and direction for the film cooling holes, minimizing contour and clamping errors. Finally, a film cooling hole machining code generation module generates the actual machining code. Compared with existing technologies, this invention minimizes contour and clamping errors, improves the machining accuracy of film cooling holes in blades, enhances the automation capability of film cooling holes in multi-stage turbine blades, and thus improves machining efficiency. This facilitates the establishment of an automated production line for machining film cooling holes in multi-stage turbine blades. Attached Figure Description

[0014] Figure 1This is a schematic diagram of laser measurement of the outer contour of a multi-stage turbine blade.

[0015] Figure 2 A mapping method for the position and orientation of air film cooling holes;

[0016] Figure 3 This is a flowchart of the present invention;

[0017] Figure 4 This is a comparison diagram showing the effects of using traditional film pore processing methods and the present invention. Detailed Implementation

[0018] like Figures 1-3 As shown in this embodiment, an adaptive machining method for high-speed EDM film cooling holes in multi-stage turbine blades includes:

[0019] Step 1: Measure the outer contour of the turbine blade using a five-axis laser measuring machine and a laser measurement sensor, and reconstruct the target point cloud model of the blade. The measurement process is as follows: Figure 1 As shown, the laser measurement sensor 1 emits a laser 2 and scans the outer contour of the turbine blade body 3. The scan data is then converted into an actual point cloud model in space through internal calculations by the processor.

[0020] Step 2: Using a nonlinear point cloud matching algorithm, an intermediate mesh satisfying the minimum deformation energy is generated based on the actual point cloud model and the ideal blade mesh model obtained in Step 1. Specifically: Where: E(X′) is the deformation energy of the source mesh, X ′ Let M be the set of spatial coordinates of all points on the source grid, and let x be the set of coordinates of all points on the source grid. ′ Let x be the spatial coordinates of a point on the source grid, x be the spatial coordinates of a point on the target point cloud, N(i) be the set of indices of all neighboring points of the i-th point, and C be the spatial coordinates of a point on the target point cloud. i It includes point x i x corresponding to N(i) N(i) The set of C i ′ contains x i x′ corresponding to N(i) N(i) The set of E(C) i C i ′)=∑ j∈N(i) ω ij |(x i ′-x′ j )-R i (x i -x j )| 2 R is the deformation energy of the i-th point and its neighborhood. i Let ω be the rotation matrix corresponding to the i-th point to be optimized. iThis is the weight of the deformation energy at each point on the source mesh, typically set to 1. Let X' be the weight of the line connecting the i-th point to its neighboring j-th point. The optimized X' corresponds to the intermediate grid.

[0021] Step 3: Use the mesh normal growth algorithm to reduce the distance between the intermediate mesh obtained in Step 2 and the target point cloud to obtain the final target mesh for processing. Specifically: Where: f(d) is the average distance between the intermediate grid and the target point cloud, d is the distance to be optimized, m is the number of points in the grid, and y i Let x be the coordinate of the i-th point in the target point cloud. i Let n be the coordinates of the i-th point in the middle grid. i Let be the direction of the normal vector of the i-th point in the middle grid.

[0022] Step 4, as follows Figure 2 As shown, the process involves finding the triangular mesh element of the ideal mesh closest to the film cooling vent location, obtaining the mapping point of the vent in the ideal mesh triangular element using the perpendicular mapping method, and then finding the corresponding element of the above triangular element in the target mesh obtained in step three that has the same topological position. Finally, the local coordinate system mapping method is used to obtain the corresponding position of the film cooling vent location in the mesh obtained by nonlinear matching, thereby realizing the transformation of the film cooling vent location and orientation to the target mesh space. Specifically, this includes:

[0023] 4.1 Draw a perpendicular line from the air film pore location to the triangular mesh element. The perpendicular line intersects the triangular element at a point, which is the mapping point of the air film pore location.

[0024] 4.2 Establish local coordinate systems for the ideal mesh triangular element closest to the film cooling vent and the corresponding triangular element of the target mesh, respectively; then use the local coordinate system to map the ideal triangular element from three-dimensional space to two-dimensional parameter space, and obtain the correspondence between the triangular elements in the two-dimensional parameter space and the triangular elements in the target mesh space; using the mapping points obtained in step 4.1, find the coordinates of the film cooling vent in the two-dimensional parameter space; finally, based on the correspondence between the triangular elements in the two-dimensional parameter space and the triangular elements in the target mesh space, transform the film cooling vent in the two-dimensional parameter space to the target mesh space, thereby realizing the transformation of the film cooling vent position and direction from the ideal mesh space to the target mesh space.

[0025] Step 5: By establishing the transformation matrix of the kinematic model, the position and orientation of the air film hole obtained in Step 4 are transformed into the coordinate system of the high-speed EDM small hole machining center. Specifically, the transformation matrix is ​​as follows: Where: C k =cosθ k S k =sinθk k = b, c, θ = [θ x ,θ y ,θ z ,θ b ,θ c ] T The distance between the origins of the two coordinate systems and the angular difference between the rotation axes are given. Based on the film cooling hole positions and coordinate transformation matrix obtained in step four, the machining code for the film cooling holes of any multi-stage turbine blade can be obtained.

[0026] In machining a turbine blade with a 2mm spacing between two film cooling holes, the two drilling methods described above were used. Results showed that the traditional film cooling hole machining method produced a poorer surface morphology. Furthermore, when machining film cooling holes in the same row but with different orientations, the distance error between the holes was significantly greater than that using the adaptive film cooling hole machining method. Meanwhile, the adaptive machining method ensured that the distance error between each film cooling hole did not exceed 0.3mm. Figure 4 The figure shows the experimental results comparing the traditional film pore processing method with the present invention.

[0027] Compared with existing technologies, this method improves the positional accuracy of film diaphragm hole machining by reducing contour errors and clamping errors.

[0028] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.

Claims

1. A multi-turbine blade high-speed electric spark gas film cooling hole adaptive machining method, characterized in that, By measuring the outer contour of the turbine blade to obtain the actual point cloud model and calculating the nonlinear matching relationship between each point and the ideal blade mesh model, the designed position and orientation of the air film cooling hole are transformed into the actual point cloud space through the mapping method of the air film cooling hole position and orientation. After coordinate system transformation, the machining code in the coordinate system of the high-speed EDM machine tool is generated, thereby reducing the air film hole machining error caused by the contour error and clamping error of the multi-stage turbine blade.

2. The adaptive machining method for high-speed EDM film cooling holes in multi-stage turbine blades according to claim 1, characterized in that, The aforementioned nonlinear matching refers to: using an approximate rigid deformation algorithm to process the ideal blade mesh, transforming it into an intermediate mesh to fit the actual point cloud model; then using a mesh normal growth algorithm to transform the intermediate mesh into a target mesh so that the distance between it and the actual point cloud model is minimized, thereby completing the matching.

3. The adaptive machining method for high-speed EDM film cooling holes in multi-stage turbine blades according to claim 2, characterized in that, The aforementioned approximate rigid deformation algorithm refers to a nonlinear mesh deformation that minimizes mesh deformation energy while ensuring local rigidity during mesh deformation. Specifically: Where: E(X) ′ X represents the deformation energy of the source mesh. ′ Let M be the set of spatial coordinates of all points on the source grid, and let x be the set of coordinates of all points on the source grid. ′ Let x be the spatial coordinates of a point on the source grid, x be the spatial coordinates of a point on the target point cloud, N(i) be the set of indices of all neighboring points of the i-th point, and C be the spatial coordinates of a point on the target point cloud. i It includes point x i x corresponding to N(i) N(i) The set, C′ i It includes x′ i x′ corresponding to N(i) N(i) The set of E(C) i ,C′ i )=∑ j∈N(i) ω ij |(x′ i -x′ j )-R i (x i -x j )| 2 R is the deformation energy of the i-th point and its neighborhood. i Let ω be the rotation matrix corresponding to the i-th point to be optimized. i This is the weight of the deformation energy at each point on the source mesh, typically set to 1. The weight of the line connecting the i-th point and its neighboring j-th point is the optimized X. ′ The corresponding grid is the middle grid.

4. The adaptive machining method for high-speed EDM film cooling holes in multi-stage turbine blades according to claim 2, characterized in that, The aforementioned mesh normal growth algorithm refers to an algorithm that, by simulating the growth phenomenon in nature, moves each vertex along its corresponding normal vector direction to minimize the distance between the transformed intermediate mesh and the target point cloud. Specifically: Where: f(d) is the average distance between the intermediate grid and the target point cloud, d is the distance to be optimized, m is the number of points in the grid, and y i Let x be the coordinate of the i-th point in the target point cloud. i Let n be the coordinates of the i-th point in the middle grid. i Let be the direction of the normal vector of the i-th point in the middle grid.

5. The adaptive machining method for high-speed EDM film cooling holes in multi-stage turbine blades according to claim 1, characterized in that, The method for mapping the location and orientation of air film cooling holes refers to: after searching for the triangular mesh cell closest to the location of the air film cooling hole in the ideal mesh, determining the mapping point of the air film cooling hole in the found ideal mesh triangular cell through the vertical mapping method, and locating the corresponding cell on the target mesh obtained after nonlinear matching of the triangular cell; then, using the local coordinate system mapping method, obtaining the corresponding position of the air film cooling hole in the mesh obtained by nonlinear matching, thereby achieving the conversion of the location and orientation of the air film cooling hole to the target mesh space.

6. The adaptive machining method for high-speed EDM film cooling holes in multi-stage turbine blades according to claim 5, characterized in that, The vertical mapping refers to: drawing a perpendicular line from the air film pore location to the plane of the triangular mesh cell, and intersecting the triangular mesh cell at a point, which is the mapping point of the air film pore location on the triangular mesh cell.

7. The adaptive machining method for high-speed EDM film cooling holes in multi-stage turbine blades according to claim 5, characterized in that, The local coordinate system mapping refers to the following steps: First, establishing local coordinate systems for the ideal mesh triangular element closest to the film cooling hole and the corresponding triangular element of the target mesh. Using the local coordinate system, the ideal triangular element is mapped from three-dimensional space to two-dimensional parameter space, and a correspondence is established between the triangular elements in the two-dimensional parameter space and the triangular elements in the target mesh space. Then, based on the mapping points obtained in the vertical mapping step, the coordinates of the film cooling hole in the two-dimensional parameter space are determined. Finally, according to the correspondence between the triangular elements in the two-dimensional parameter space and the triangular elements in the target mesh space, the film cooling hole in the two-dimensional parameter space is transformed into the target mesh space, thereby realizing the transformation of the film cooling hole position and direction from the ideal mesh space to the target mesh space.

8. The adaptive machining method for high-speed EDM film cooling holes of multi-stage turbine blades according to any one of claims 1-7, characterized in that, specifically... include: Step 1: Measure the outer contour of the turbine blade using a five-axis laser measuring machine and a laser measuring sensor, and reconstruct the target point cloud model of the blade: The laser measuring sensor emits a laser and scans the outer contour of the turbine blade. The processor then converts the scanned data into an actual point cloud model in space. Step 2: Using a nonlinear point cloud matching algorithm, an intermediate mesh satisfying the minimum deformation energy is generated based on the actual point cloud model and the ideal blade mesh model obtained in Step 1. Specifically: Where: E(X) ′ X represents the deformation energy of the source mesh. ′ Let M be the set of spatial coordinates of all points on the source grid, and let x be the set of coordinates of all points on the source grid. ′ Let x be the spatial coordinates of a point on the source grid, x be the spatial coordinates of a point on the target point cloud, N(i) be the set of indices of all neighboring points of the i-th point, and C be the spatial coordinates of a point on the target point cloud. i It includes point x i x corresponding to N(i) N(i) The set, C′ i It includes x′ i x′ corresponding to N(i) n(i) The set of E(C) i ,C′ i )=∑ j∈N(i) ω ij |(x′ i -x′ j )-R i (x i -x j )| 2 R is the deformation energy of the i-th point and its neighborhood. i Let ω be the rotation matrix corresponding to the i-th point to be optimized. i This is the weight of the deformation energy at each point on the source mesh, typically set to 1. The weight of the line connecting the i-th point and its neighboring j-th point is the optimized X. ′ The corresponding grid is the middle grid; Step 3: Use the mesh normal growth algorithm to reduce the distance between the intermediate mesh obtained in Step 2 and the target point cloud to obtain the final target mesh for processing. Specifically: Where: f(d) is the average distance between the intermediate grid and the target point cloud, d is the distance to be optimized, m is the number of points in the grid, and y i Let x be the coordinate of the i-th point in the target point cloud. i Let n be the coordinates of the i-th point in the middle grid. i Let be the direction of the normal vector at the i-th point of the intermediate grid. Step 4: Find the triangular mesh element of the ideal mesh closest to the film cooling hole location. Use the perpendicular mapping method to obtain the mapping point of the film cooling hole in the ideal mesh triangular element. Then find the corresponding element of the above triangular element in the target mesh obtained in Step 3 with the same topological position. Finally, use the local coordinate system mapping method to obtain the corresponding position of the film cooling hole location in the mesh obtained by nonlinear matching, thereby realizing the transformation of the film cooling hole location and direction to the target mesh space. Specifically, this includes: 4.1 Draw a perpendicular line from the air film pore location to the triangular mesh element. The perpendicular line intersects the triangular element at a point, which is the mapping point of the air film pore location. 4.2 Establish local coordinate systems for the ideal mesh triangular element closest to the film cooling hole and the corresponding triangular element of the target mesh, respectively; then use the local coordinate system to map the ideal triangular element from three-dimensional space to two-dimensional parameter space, and obtain the correspondence between the triangular elements in the two-dimensional parameter space and the triangular elements in the target mesh space; using the mapping points obtained in step 4.1, find the coordinates of the film cooling hole in the two-dimensional parameter space; finally, according to the correspondence between the triangular elements in the two-dimensional parameter space and the triangular elements in the target mesh space, transform the film cooling hole in the two-dimensional parameter space to the target mesh space, thereby realizing the transformation of the film cooling hole position and direction from the ideal mesh space to the target mesh space; Step 5: By establishing the transformation matrix of the kinematic model, the position and orientation of the air film hole obtained in Step 4 are transformed into the coordinate system of the high-speed EDM small hole machining center. Specifically, the transformation matrix is ​​as follows: Where: C k =cosθ k S k =sinθ k k = b, c, θ = [θ x ,θ y ,θ z ,θ b ,θ c ] T Given the distance between the origins of the two coordinate systems and the angle difference between the rotation axes, the machining code for the film cooling hole positions of any multi-stage turbine blade can be obtained based on the film cooling hole positions and coordinate transformation matrix obtained in step four.

9. An adaptive machining system for high-speed EDM film cooling holes of multi-stage turbine blades implementing the method of any one of claims 1-8, characterized in that, include: The system includes a five-axis laser measuring machine tool, a nonlinear point cloud matching and calculation module, a hole position and orientation mapping module, and a film cooling hole processing code generation module. The five-axis laser measuring machine tool integrates a laser measuring instrument and a five-axis linkage machine tool. It is used to perform laser scanning to obtain point cloud information of the outer contour of the multi-stage turbine blade to be processed, namely the blade body and the upper and lower edge plates. The nonlinear point cloud matching and calculation module performs nonlinear matching based on the point cloud information measured by laser and the ideal mesh model to obtain the target mesh that is closest to the point cloud. The hole position and orientation mapping module uses the relationship between the ideal mesh model and the target mesh to transform the air film hole position in the ideal mesh model to obtain the spatial coordinates of the air film hole position in the target mesh. The air film hole machining code generation module converts the air film hole position to the machining machine space according to the spatial coordinates of the air film hole position in the target mesh and the conversion relationship from the target mesh space to the machining machine space, thereby obtaining the EDM code.

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