Turbine blade film hole and cavity surface coherent detection method based on Mler-Trumb algorithm

Abstract

The invention discloses a turbine blade film hole and cavity surface coherent detection method based on a Mller-Trumb algorithm, and the method comprises the steps: firstly dispersing an internal cavity surface of a blade into triangular patches, reconstructing a three-dimensional model, and constructing a local coordinate system of a film hole cylinder; a space bounding box technology is used to carry out coarse detection and screen a potential interference area, and then a Mler-Trumb algorithm is used to carry out fine detection on an intersection state of a cylindrical discrete line segment and a cavity surface triangular patch. According to the invention, automatic interference detection in a film hole design stage is realized, the problems of low efficiency and large error of traditional manual checking are solved, the detection precision can reach a millimeter level, and the time consumed by single-hole detection is less than 0.1 second. Compared with a traditional method, the method has the advantages that the detection efficiency is greatly improved, the problem of cooling failure caused by interference between the air film hole and the cavity surface can be effectively avoided, and a reliable digital verification means is provided for optimization design of an aero-engine turbine blade cooling system.

Description

Technical Field

[0001] The present invention belongs to the field of engineering thermophysics and specifically relates to a Coherent detection method for film holes on the surface of turbine blades and internal cavity surfaces based on an algorithm. Background Art

[0002] The algorithm is an efficient algorithm for ray-triangle intersection detection in computer graphics, proposed by Tomas and Ben Trumbore in 1997. This algorithm determines the intersection by directly calculating the barycentric coordinate parameters. Only one matrix determinant operation is required to complete the detection, which has the characteristics of low computational complexity and high efficiency. Its core steps include: calculating the triangle edge vector and the plane normal vector, determining whether they are parallel or coplanar by the determinant, and then solving the barycentric coordinate parameters u, v and the ray parameter t to finally determine the intersection position. The algorithm uses vector cross product and dot product operations, has good numerical stability, and can effectively handle special cases such as thin triangles or coplanarity. Compared with traditional methods, this algorithm avoids redundant calculations and is widely used in ray tracing, collision detection, 3D modeling interactive picking and other fields. Although the computational complexity is O(1), it may still be affected by floating-point precision in practical applications. In the future, the performance can be further improved by GPU parallel computing and other methods. Due to its simplicity and efficiency, this algorithm has become one of the standard solutions for ray-triangle intersection detection in the field of graphics.

[0003] When designing film holes on turbine blades, adjusting the hole positions or other parameters based solely on the blade surface can result in holes that do not fully intersect the internal cavity surface, rendering the designed model invalid. To avoid invalid film holes in the designed film hole layout, each hole must be checked for coherence with the internal cavity surface. Traditional film hole design processes, typically performed in modeling software such as UG, do not fully design and validate each individual hole. Instead, they perform a 2D design of the hole array and then batch-generate hole clusters using commands such as hole generation. This process adds 3D features to the hole array, but does not ensure that all holes intersect correctly with the internal cavity surface to ensure proper cooling airflow. Therefore, after the hole cluster layout is complete, the internal hole-cavity surface intersection must be checked. This process relies on software implementation and manual inspection and judgment. While not complex, it adds complexity and uncertainty to the design process. Summary of the Invention

[0004] In order to overcome the problems existing in the prior art, the purpose of the present invention is to provide a The method for coherent detection of turbine blade surface film holes and internal cavity surfaces of an algorithm greatly improves detection efficiency, can effectively avoid cooling failure problems caused by film hole and cavity surface interference, and provides a reliable digital verification method for optimization design of an aero-engine turbine blade cooling system.

[0005] The purpose of the application is achieved by the following technical solutions:

[0006] A method for coherent detection of turbine blade film holes and cavity surfaces based on An algorithm for coherent detection of turbine blade film holes and cavity surfaces, characterized by the following steps:

[0007] Step 1: Export the internal cavity surface.stl file in the geometric processing software, and then discretize the cavity surface into triangular facets in MATLAB to reconstruct the entire cavity surface.

[0008] Step 2: Construct a cylindrical local coordinate system with the film hole direction vector as the normal vector, and calculate two unit vectors perpendicular to it.

[0009] Step 3: Convert all discrete triangular facet vertex coordinates to the cylindrical local coordinate system.

[0010] Step 4: Discretize the cylindrical surface, discretize the cylindrical surface into n rectangular facets parallel to the axis and connected to each other, and then simplify the facets into a line segment.

[0011] Step 5: Coarse detection based on spatial bounding box for the interference between the cavity surface and the film hole cylindrical surface.

[0012] Step 6: Use Algorithm to traverse all line segments on the cylindrical surface and triangular facets on the cavity surface to obtain the intersection state of all cylinders.

[0013] Step 7: Store the intersection state of each hole and cavity, and generate a visualization image.

[0014] Further, the specific steps of obtaining the cavity surface in MATLAB in step 1 include:

[0015] Step 1-1: Select the cavity surface involved in the film hole interference detection in the geometric processing software such as UG or spaceclaim, and export it in.stl format.

[0016] Step 1-2: Import the selected cavity surface file in MATLAB using the stlread command, and the.stl file is imported and reconstructed as a large number of triangular facet vertices and their connection relationships.

[0017] Step 1-3: After the.stl file is imported, the vertices of a large number of triangular facets are reconstructed and their connection relationships.

[0018] Step 1-4: Use the trisurf command to visualize the imported surface and check the completeness and correctness of its shape.

[0019] Further, the specific steps of constructing the cylindrical local coordinate system in step 2 include:

[0020] Step 2-1: The gas film hole outlet point and its direction vector are known.

[0021] Step 2-2: First, consider the gas film hole outlet point as the origin of the local coordinate system, and the sum of its direction vector and this origin is the length direction vector of the cylindrical local coordinate system.

[0022] Step 2-3: Then calculate two perpendicular vectors of the length direction vector of the cylinder, and they are perpendicular to each other.

[0023] Further, the specific steps of discretizing the cylindrical surface into line segments in step 3 include:

[0024] Step 3-1: Generate the angle θ of the discretized line segment, n line segments, with an interval of 2π / n.

[0025] Step 3-2: Calculate the X' coordinate and Y' coordinate of the start point of the line segment.

[0026] Step 3-3: Calculate the X' coordinate and Y' coordinate of the end point of the line segment.

[0027] Step 3-4: Store the start and end point coordinates of each discrete line segment.

[0028] Further, the specific steps of rough detection of the gas film hole cylinder in step 5 include:

[0029] Step 5-1: Calculate the spatial bounding box of the cavity surface using the AABB bounding box calculation method.

[0030] Step 5-2: Calculate the spatial bounding box of each detected cylinder using the OBB bounding box calculation method.

[0031] Step 5-3: Calculate whether there is an intersection between the gas film hole bounding box and the spatial bounding box of the cavity surface, and then traverse all the gas film hole cylinders.

[0032] Step 5-4: Put the gas film hole with rough detection intersection into step 7 for fine detection.

[0033] Further, the specific steps of using the algorithm to detect the intersection state of the line segment and the cavity surface in step 6 include:

[0034] Step 6-1: Calculate the plane equation of the triangular facet.

[0035] Step 6-2: Determine whether the line segment is parallel to the plane, otherwise the path is intersected.

[0036] Step 6-3: Confirm the path intersection, but still need to determine whether the intersection point is in the triangle or on the boundary.

[0037] Step 6-4: Loop to calculate the intersection of each line segment and the triangular patch.

[0038] Advantages of the present application:

[0039] 1. The present application can be used as a pre-check tool in the design process of the air film hole. By detecting the interference between the designed air film hole and the inner cavity surface, repeated adjustment and modification in geometric modeling are avoided, thereby quickly completing the scrap detection and rapid iteration in the design stage.

[0040] 2. The present application avoids manual judgment and inspection of the correctness of the air film hole, and the error is much lower than manual inspection, with high reliability and detection efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 Schematic diagram of the inner cavity surface extracted from the model in the geometric software.

[0042] Figure 2 Schematic diagram of the STL format inner cavity surface after importing MATLAB.

[0043] Figure 3 Schematic diagram of the inner cavity surface and the air film hole to be detected.

[0044] Figure 4 Schematic diagram of the OBB bounding box of the air film hole cylinder.

[0045] Figure 5 Schematic diagram of the AABB bounding box of the inner cavity surface.

[0046] Figure 6 Schematic diagram of the rough detection of the overlapping of the air film hole cylinder and the inner cavity surface bounding box.

[0047] Figure 7 Schematic diagram of N line segments obtained after the air film hole surface is discretized.

[0048] Figure 8 Schematic diagram of the air film hole (marked in black) which is completely not intersected after detection with the inner cavity surface.

[0049] Figure 9 Schematic diagram of the air film hole (marked in black) which is only partially intersected after detection with the inner cavity surface.

[0050] Figure 10 Schematic diagram of the flow of the present application. DETAILED DESCRIPTION

[0051] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, but should not be construed as limiting the present invention.

[0052] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. Figure 10 It is a schematic flow diagram of the present invention.

[0053] A kind of The coherent detection method of the air film holes on the surface of the turbine blade and the internal cavity surface based on the algorithm includes the following steps:

[0054] Step 1: Take the GE-E3 model as an example and export it in the geometry processing software SpaceClaim. Figure 1 The .stl file of the internal cavity surface shown in the figure is then imported into MATLAB using the stlread command. The file will be imported with the vertex coordinate set and connection relationship of the triangular facets. The entire cavity surface can be reconstructed using the triangular facets in MATLAB, as shown in the following example: Figure 2 shown.

[0055] Step 2: Generate some air film hole cylinders distributed around the inner cavity surface in the space where the inner cavity surface is located. These cylinders will participate in the subsequent cavity surface-air film hole detection. The positional relationship between the two is as follows: Figure 3 As shown. Constructing a local cylindrical coordinate system, in order to calculate the intersection state of each triangular facet and each cylindrical surface, it is necessary to convert the vertex coordinates of each facet into the coordinates of the cylindrical local coordinate system through a certain conversion method. This can simplify the subsequent calculation and improve the detection efficiency. First, the Z axis in the cylindrical coordinate system is the cylindrical axial vector, which only needs to be normalized. The XY axis needs to be calculated by a pair of unit vertical vectors, and the three must be perpendicular to each other.

[0056] Step 3: Convert the .stl patch vertices to the cylindrical local coordinate system. The conversion method can be known from mathematical calculations. You only need to calculate the vector from the vertex to the origin of the cylinder and multiply it by the cylindrical coordinate system unit vector group to complete the conversion.

[0057] Step 4: Discretize the cylindrical surface. The intersection detection between the complete cylindrical surface and the triangular patch can theoretically be determined by calculating whether the cylindrical surface equation and the triangular patch equation have the same solution. However, this method requires a very large amount of calculation, which is unacceptable for the detection of a large number of triangular patches and cylindrical surfaces. Therefore, the present invention proposes an idea for discretization detection of cylindrical surfaces: decompose the cylindrical surface evenly into n line segments, and calculate the starting and ending point coordinates of each line segment in the cylindrical coordinate system. When the line segments are dense enough, they can be considered to participate in intersection detection instead of the surface. In this way, the intersection detection problem is reduced in dimensionality, the amount of calculation is greatly reduced, and the efficiency is also improved. For example, a discretized air film hole Figure 7 shown.

[0058] Step 5: Rough detection is performed on the gas film hole cylinder, and the cylinder surface obviously not intersecting with the cavity surface is screened, and the space bounding box of the gas film hole cylinder and the cavity surface needs to be calculated in advance, for the space bounding box of the cavity surface, due to the irregular shape, the AABB bounding box method is the most simple and efficient, as shown in Figure 5 ; and for the gas film hole cylinder with a clear axis, the OBB bounding box with a main direction is used, as shown in Figure 4 ; if the two volume bounding boxes do not completely coincide, the gas film hole and the cavity surface are excluded, and the precise detection stage is entered, and the bounding box intersection is as shown in Figure 6 .

[0059] Step 6: the algorithm is called to detect the intersection of all line segments and triangular surfaces, when a line segment returns a true detection value, there is a triangular surface intersecting with it, otherwise, the line segment does not intersect with the triangular surface, when all line segments return a true detection value, the cylinder and the triangular surface completely intersect, and the operation is performed on all cylinders, and the intersection state of all cylinders is obtained, and the gas film hole cylinder needs to be excluded, as shown in Figure 8 and 9 , that is, the completely non-intersecting and partially intersecting cases should be excluded.

[0060] Step 7: the detection result is visualized, the gas film hole detected by the detection is colored with red and drawn together with the cavity surface, and the gas film hole not detected by the detection is drawn with black color, as shown in Figure 8 and 9 .

[0061] The present application first disperses the cavity surface inside the blade into triangular surfaces and reconstructs a three-dimensional model, and constructs a local coordinate system of the gas film hole cylinder; the space bounding box technology is used for rough detection to screen the potential interference area, and the algorithm is used for precise detection of the intersection state of the cylinder dispersed line segment and the cavity triangular surface. The present application realizes the automatic interference detection in the gas film hole design stage, solves the problems of low efficiency and large error of traditional manual checking, the detection precision can reach millimeter level, and the single hole detection time is less than 0.1 second. Compared with the traditional method, the detection efficiency is greatly improved, and the cooling failure problem caused by the interference between the gas film hole and the cavity surface can be effectively avoided, which provides a reliable digital verification means for the optimization design of the turbine blade cooling system of the aero-engine.

Claims

1. A method based on The coherent detection method of the air film hole and cavity surface of the turbine blade based on the algorithm is characterized by: The following steps are involved: 1) Export the .stl file of the internal cavity surface in the geometry processing software, and then discretize the cavity surface into triangular facets in MATLAB to reconstruct the entire cavity surface; 2) Construct a local cylindrical coordinate system, use the air film hole direction vector as the normal, and calculate two unit vectors perpendicular to it; 3) Convert all discrete triangle vertex coordinates to the cylindrical local coordinate system; 4) Discretize the cylindrical surface into n rectangular patches parallel to the axis and connected to each other on the sides, and then simplify the patch into a line segment; 5) Perform a rough detection of the interference between the cavity surface and the air film hole cylinder based on the spatial bounding box; 6) Use The algorithm traverses all line segments on the cylindrical surface and triangular facets on the cavity surface to be detected, that is, accurately detects the intersection status of all cylinders; 7) Store the intersection state of each circular hole and cavity surface and generate a visualization image.

2. According to claim 1 The coherent detection method of the air film hole and cavity surface of the turbine blade based on the algorithm is characterized by: In step 1), the specific steps of discretizing the cavity surface into triangular facets in MATLAB to reconstruct the entire cavity surface include: 1-1) In UG or SpaceClaim geometry processing software, select the cavity surface that needs to participate in the air film hole interference detection and export it in .stl format; 1-2) Use the stlread command in MATLAB to import the selected cavity surface file. The .stl file is imported and reconstructed into a large number of triangular facets and their connection relationships; 1-3) Use the trisurf command to visualize the imported surface and check its shape integrity and correctness.

3. The method according to claim 1 The coherent detection method of the air film hole and cavity surface of the turbine blade based on the algorithm is characterized by: The specific steps of constructing the cylindrical local coordinate system in step 2) include: 2-1) The film hole exit point and its direction vector are known; 2-2) First, consider the film hole exit point as the origin of the local coordinate system. The sum of its direction vector and this origin is the cylinder length direction vector in the local coordinate system. 2-3) Then calculate two perpendicular vectors to the length direction vector of the cylinder, and they are perpendicular to each other.

4. The method according to claim 1 The coherent detection method of the air film hole and cavity surface of the turbine blade based on the algorithm is characterized by: The specific steps of discretizing the cylindrical surface into line segments in step 3) include: 3-1) Generate the angle θ of the discretized line segments, n line segments, with an interval of 2π / n; 3-2) Calculate the X' and Y' coordinates of the starting point of the line segment; 3-3) Calculate the X' and Y' coordinates of the end point of the line segment; 3-4) Store the start and end coordinates of each discrete line segment.

5. The method according to claim 1 The coherent detection method of the air film hole and cavity surface of the turbine blade based on the algorithm is characterized by: The specific steps of performing a rough inspection on the air film hole cylinder in step 5) include: 5-1) Use the AABB bounding box calculation method to calculate the spatial bounding box of the cavity surface; 5-2) Use the OBB bounding box calculation method to calculate the spatial bounding box of each detected cylinder; 5-3) Calculate whether the air film hole bounding box and the cavity surface's spatial bounding box intersect, and then traverse all air film hole cylinders; 5-4) The air film holes with intersections in the rough detection are put into the fine detection in step 6).

6. The method according to claim 1 The coherent detection method of the air film hole and cavity surface of the turbine blade based on the algorithm is characterized by: Use in step 6) The algorithm accurately detects the intersection of line segments and cavity surfaces. The specific steps include: 6-1) Calculate the plane equation of the triangular patch; 6-2) Determine whether the line segment is parallel to the plane, otherwise the path intersects; 6-3) Confirm that the paths intersect, but still need to determine whether the intersection point is inside the triangle or on the boundary; 6-4) Loop and calculate the intersection of each line segment and the triangle.

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