Unstructured mesh generation method applied to numerical calculation of heat flow field of sleeve

Abstract

The invention discloses an unstructured mesh generation method applied to casing heat flow field numerical calculation, which relates to the technical field of engineering, and comprises the following steps: obtaining the structural characteristics of a casing, and constructing a casing finite element analysis model; preprocessing the finite element analysis model of the casing pipe, identifying geometric defects and carrying out geometric shape division; performing grid drawing based on the fluid area and the solid area of the casing finite element analysis model to obtain a first grid and a second grid; and based on the first grid and the second grid, casing pipe swept grid data are obtained, and a three-dimensional swept grid is formed. According to the unstructured grid drawing method for sleeve heat flow field numerical calculation based on the sweeping method, the grid subdivision efficiency is improved, the calculation complexity of sleeve heat flow field analysis is effectively reduced, and powerful technical support is provided for design, optimization and safe operation of power equipment.

Description

Technical Field

[0001] The invention relates to the field of engineering technology, in particular to an unstructured grid generation method applied to numerical calculation of thermal flow field of a casing. Background Art

[0002] In power equipment, bushings, as one of the key components, are widely used in various transformers and electrical equipment fields. With the continuous development and increasing complexity of power equipment, the thermal flow field analysis of bushings has gradually become an important link to ensure equipment safety and improve operating efficiency. The thermal flow field analysis of bushings relies on numerical simulation methods, such as the finite element method FEM and the finite difference method FDM. These methods mesh the geometric structure of the bushing and construct mathematical models to calculate the temperature distribution, heat conduction and convection characteristics. With the continuous advancement of numerical simulation technology, the calculation accuracy and efficiency have been significantly improved, especially with the support of modern computing power, it can handle more complex geometric shapes and thermal flow field distributions.

[0003] However, the existing technology still has many shortcomings in the analysis of the thermal flow field of the sleeve: since the axial length of the sleeve is usually much larger than the radial length, and the internal structure is complex, there are multiple irregular geometric shapes and flow areas, making it difficult for traditional meshing methods to effectively deal with the geometric characteristics of the sleeve, especially in the multi-physics field coupling analysis of fluid flow and heat conduction in the sleeve, the construction of the grid often faces great challenges; traditional meshing methods often use regular grids or simplified geometric shapes for analysis, but when faced with complex structures, it is easy to cause the grid to be too coarse or distorted, thereby affecting the calculation accuracy and reliability of the results; at the same time, due to the huge amount of calculation required for meshing, especially when high-precision thermal flow field simulation is required, the traditional method will face the problems of excessive consumption of computing resources and slow calculation speed; therefore, the existing meshing methods are difficult to adapt to the needs of efficient and accurate drawing of the thermal flow field of the sleeve, especially in the case of complex geometric features and internal fluid flow characteristics, and still cannot give full play to its advantages in high-precision numerical simulation. Summary of the invention

[0004] In view of the above-mentioned problems, the present invention is proposed.

[0005] Therefore, the problem to be solved by the present invention is how to provide an unstructured grid generation method based on a sweeping method for numerical calculation of the thermal flow field of a sleeve, which can provide a swept grid that meets the structural characteristics of the sleeve when performing numerical calculations on the thermal flow field of the sleeve, improve the grid generation efficiency, reduce the number of redundant grids, capture the flow characteristics of the fluid, and improve the computational efficiency while ensuring the accuracy of the numerical calculation of the thermal flow field.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] In a first aspect, an embodiment of the present invention provides an unstructured grid generation method for numerical calculation of a sleeve thermal flow field, which includes acquiring structural features of the sleeve and constructing a finite element analysis model of the sleeve; preprocessing the finite element analysis model of the sleeve, identifying geometric defects and performing geometric shape division; grid drawing based on the fluid region and solid region of the finite element analysis model of the sleeve to obtain a first grid and a second grid; obtaining sleeve swept grid data based on the first grid and the second grid to form a three-dimensional swept grid.

[0008] As a preferred solution of the unstructured grid generation method for numerical calculation of the thermal flow field of the bushing described in the present invention, wherein: the structural features of the bushing include a solid area and a fluid area; the solid area includes a conductor, a flange and a core; the fluid area includes air and oil; the bushing finite element analysis model is used to analyze the thermal flow field distribution under the natural convection phenomenon generated by the fluid medium filled in the bushing when the bushing conductor is energized and heated; the bushing finite element analysis model is a two-dimensional axisymmetric model containing detailed geometric information and material properties.

[0009] As a preferred solution of the unstructured grid generation method for the numerical calculation of the thermal flow field of the bushing described in the present invention, the construction of the bushing finite element analysis model includes the following steps: obtaining the structural characteristics of the bushing, including three solid regions of the conductor, the flange and the core, and two fluid regions of the air and the oil; constructing a two-dimensional axisymmetric structure of the conductor, the flange, the core, the air and the oil, and generating a two-dimensional axisymmetric finite element analysis model; marking the axis of symmetry in the two-dimensional axisymmetric finite element analysis model, and marking the rotation surface of the two-dimensional axisymmetric finite element analysis model that can form a complete bushing by rotating along the axis of symmetry.

[0010] As a preferred scheme of the unstructured grid generation method for numerical calculation of thermal flow field of casing described in the present invention, wherein: the geometric defects include sharp-angle geometric defects and slit geometric defects; the geometric shape division is used to simplify the grid generation process while maintaining the ability to capture key features of the thermal flow field; the identification of geometric defects and geometric shape division include the following steps: preprocessing the two-dimensional axisymmetric finite element analysis model to identify geometric defects that are difficult to directly grid, including sharp-angle geometric defects and slit geometric defects; geometrically dividing the geometric defects by segmentation or recombination to obtain a geometric shape containing two groups of opposite edges; reconstructing the fluid region in the two-dimensional axisymmetric finite element analysis model based on the geometric shape containing two groups of opposite edges to obtain a reconstructed fluid region.

[0011] As a preferred solution of the unstructured grid generation method for numerical calculation of thermal flow field of casing described in the present invention, wherein: obtaining the first grid and the second grid includes the following steps: setting the axial grid size and radial grid size of the reconstructed fluid area based on the requirements of thermal flow field analysis; setting the axial grid size and radial grid size of the solid area in the two-dimensional axisymmetric finite element analysis model based on the requirements of thermal flow field analysis; based on the lower limit of the grid size, using a mapping method to draw the first grid in the fluid area of ​​the rotating surface of the two-dimensional axisymmetric finite element analysis model; based on the lower limit of the grid size, using a free triangle grid division method to draw the second grid in the solid area of ​​the rotating surface.

[0012] As a preferred scheme of the unstructured grid generation method for numerical calculation of thermal flow field of casing described in the present invention, wherein: setting the axial grid size and radial grid size of the reconstructed fluid region and solid region refers to refining the grid size to the standard of grid-independent solution; the standard of grid-independent solution refers to comparing the calculation results under different grid densities after multiple trials, and then obtaining the lower limit of the grid size that meets the accuracy requirements.

[0013] As a preferred solution of the unstructured grid generation method for the numerical calculation of the thermal flow field of the sleeve described in the present invention, wherein: the sleeve swept grid data includes the overall size and distribution of the sleeve swept grid; the forming of the three-dimensional swept grid includes the following steps: setting the sleeve swept grid data based on the first grid and the second grid; obtaining the rotation surface that can form a complete sleeve by rotating along the symmetry axis in the two-dimensional axisymmetric finite element analysis model, and setting the rotation surface as the source surface of the swept grid; setting the second rotation surface that is spaced from the source surface by a preset angle as the target surface of the swept grid; refining the size of the swept grid based on the standard of the grid-independent solution to obtain the refined swept grid size; based on the refined swept grid size, rotating the first grid and the second grid of the source surface along the symmetry axis to the target surface to generate a three-dimensional swept grid.

[0014] In the second aspect, in order to further solve the safety problems existing in the project, the embodiment of the present invention provides an unstructured grid generation system for numerical calculation of the thermal flow field of the casing, which includes: a model building module, which is used to obtain the solid area and the fluid area of ​​the casing and construct a finite element analysis model of the casing; a defect recognition module, which is used to preprocess the finite element analysis model of the casing, identify geometric defects in the fluid area and perform geometric shape division to obtain a reconstructed fluid area; a grid drawing module, which is used to grid the reconstructed fluid area and solid area in the finite element analysis model of the casing to obtain a first grid and a second grid; a grid generation module, which is used to obtain the overall size and distribution of the casing swept grid according to the first grid and the second grid, and then generate a three-dimensional swept grid.

[0015] In a third aspect, an embodiment of the present invention provides a computer device, comprising a memory and a processor, wherein the memory stores a computer program, wherein: when the computer program is executed by the processor, any step of the unstructured grid generation method for numerical calculation of the thermal flow field of the casing as described in the first aspect of the present invention is implemented.

[0016] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein: when the computer program is executed by a processor, any step of the unstructured grid generation method for numerical calculation of thermal flow field of a casing as described in the first aspect of the present invention is implemented.

[0017] Beneficial effects of the invention: The invention proposes an unstructured grid drawing method for numerical calculation of the thermal flow field of the bushing based on the sweeping method, which not only improves the efficiency of grid generation, but also effectively reduces the computational complexity of the thermal flow field analysis of the bushing, and provides strong technical support for the design, optimization and safe operation of power equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0019] Figure 1 This is an overall flow chart of the unstructured grid generation method used in numerical calculation of the thermal flow field of the casing in Example 1.

[0020] Figure 2 This is a schematic diagram of the casing model in Example 1.

[0021] Figure 3 This is the mesh division diagram of the rotating surface in Example 1.

[0022] Figure 4 This is a cross-sectional view of the swept grid in Example 1.

[0023] Figure 5 This is a schematic diagram of the structure of the computer device in Example 3. DETAILED DESCRIPTION

[0024] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0025] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0026] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0027] Example 1

[0028] Reference Figure 1 to Figure 4 , which is the first embodiment of the present invention, provides an unstructured grid generation method for numerical calculation of thermal flow field of casing.

[0029] The existing bushing thermal flow field analysis methods mainly have the following problems: since the axial length of the bushing is usually much larger than the radial length, and the internal structure is complex, there are multiple irregular geometric shapes and flow areas, making it difficult for traditional mesh generation methods to effectively deal with the geometric characteristics of the bushing, especially in the multi-physics field coupling analysis of fluid flow and heat conduction in the bushing, the construction of the mesh often faces great challenges; traditional mesh generation methods often use regular grids or simplified geometric shapes for analysis, but when faced with complex structures, it is easy to cause the grid to be too coarse or distorted, thereby affecting the calculation accuracy and reliability of the results; at the same time, due to the huge amount of calculation required for mesh generation, especially when high-precision thermal flow field simulation is required, traditional methods will face the problems of excessive consumption of computing resources and slow calculation speed.

[0030] The present application provides an effective solution to the above-mentioned problems. Next, multiple embodiments will be combined to explain in detail how to implement the unstructured grid generation method for the numerical calculation of the thermal flow field of the casing.

[0031] Figure 1 The overall flow chart of the unstructured grid generation method applied to the numerical calculation of the thermal flow field of the casing is shown, including:

[0032] S1: Obtain the structural characteristics of the casing and build a finite element analysis model of the casing.

[0033] Preferably, the structural features of the sleeve include a solid region and a fluid region.

[0034] Specifically, the solid region includes the conductor, the flange and the core.

[0035] Specifically, the fluid region includes air and oil.

[0036] Preferably, the bushing finite element analysis model is used to analyze the heat flow field distribution under the natural convection phenomenon generated by the fluid medium filled in the bushing when the bushing conductor is energized and heated, wherein the fluid medium includes air and oil.

[0037] Specifically, the bushing finite element analysis model is a two-dimensional axisymmetric model containing detailed geometric information and material properties, which can accurately reflect the physical properties of the bushing components (such as conductors, flanges, cores) and the surrounding fluid area.

[0038] Further, such as Figure 2 The figure shows a schematic diagram of the bushing model. Constructing the bushing finite element analysis model includes the following steps: obtaining the structural characteristics of the bushing, including three solid regions of the conductor, flange and core, and two fluid regions of air and oil.

[0039] A two-dimensional axisymmetric structure of conductor, flange, core, air and oil is constructed to generate a two-dimensional axisymmetric finite element analysis model.

[0040] Mark the symmetry axis in the 2D axisymmetric finite element analysis model, and mark the rotation surface that can form a complete casing by rotating along the symmetry axis in the 2D axisymmetric finite element analysis model, where Figure 3 The figure shows the meshing diagram of the rotated surface.

[0041] Preferably, the present invention can accurately reflect the interaction between the fluid and the solid area inside the casing by modeling the geometric features of the casing in detail, especially the distribution of the thermal flow field when the current generates heat through the conductor and causes natural convection of the fluid; compared with the traditional model that usually ignores the dynamic behavior of the fluid medium, the present invention improves the authenticity and calculation accuracy of the model by comprehensively considering the interaction between the solid and the fluid, and solves the problem of accurate simulation of the complex thermal flow field in the casing, especially the influence of non-uniform heating and flow of the fluid on heat transfer.

[0042] S2: Preprocess the casing finite element analysis model, identify geometric defects and divide the geometric shape.

[0043] Preferably, the geometric defects include sharp-angle geometric defects and slit geometric defects.

[0044] Specifically, geometric shape partitioning is used to simplify the mesh generation process while maintaining the ability to capture key features of the thermal flow field, ensuring the quality of the mesh and calculation accuracy.

[0045] Specifically, identifying geometric defects and performing geometric shape division includes the following steps: preprocessing the two-dimensional axisymmetric finite element analysis model, identifying geometric defects that are difficult to directly mesh, including sharp-angle geometric defects and slit geometric defects.

[0046] The geometric defects are divided into geometric shapes by segmentation or recombination to obtain geometric shapes containing two sets of opposite edges, wherein the geometric shapes include diamond structures and trapezoidal structures, thereby dividing the originally complex fluid area into structures with more regular shapes and easier to handle.

[0047] A fluid region in a two-dimensional axisymmetric finite element analysis model is reconstructed based on a geometric shape containing two sets of opposite edges to obtain a reconstructed fluid region.

[0048] Preferably, the present invention effectively avoids the generation of irregular grids and improves the uniformity and stability of the grid by dividing complex geometric shapes, especially areas that are difficult to grid, such as sharp corners and slits. This division not only simplifies the grid generation process, but also ensures the calculation accuracy, avoids calculation errors caused by poor grid quality, and solves the gridding difficulties caused by complex geometric shapes, making the entire model more stable and efficient during numerical calculations.

[0049] S3: Mesh drawing is performed based on the fluid region and the solid region of the casing finite element analysis model to obtain a first mesh and a second mesh.

[0050] Preferably, obtaining the first grid and the second grid comprises the following steps: setting the axial grid size and the radial grid size of the reconstructed fluid region based on the requirements of the thermal flow field analysis.

[0051] Based on the requirements of thermal flow field analysis, the axial mesh size and radial mesh size of the solid area in the two-dimensional axisymmetric finite element analysis model are set to ensure that the mesh is refined enough to capture the key features of the thermal flow field.

[0052] Based on the lower limit of mesh size, a mapping method is used to draw the first mesh in the fluid region of the rotation surface of a two-dimensional axisymmetric finite element analysis model.

[0053] Based on the lower limit of mesh size, a free triangle meshing method is used to draw the second mesh on the solid region of the rotation surface to adapt to the complex geometry and maintain the flexibility and computational efficiency of the mesh.

[0054] Furthermore, setting the axial grid size and radial grid size of the reconstructed fluid region and solid region refers to refining the grid size to the standard of a grid-independent solution, that is, further refining the grid no longer significantly affects the calculation results, thereby optimizing the use of computing resources while ensuring the calculation accuracy.

[0055] Specifically, the standard for grid-independent solutions refers to comparing the calculation results under different grid densities after multiple trials, and then obtaining the lower limit of the grid size that meets the accuracy requirements.

[0056] Preferably, the present invention sets appropriate grid sizes in the fluid region and the solid region, and combines the mapping method and the free triangle grid division, so as to optimize the use of computing resources while ensuring the accuracy of the thermal flow field. In particular, when refining the grid, it ensures that the grid is refined to the standard of the grid-independent solution, so that further grid refinement will not significantly affect the calculation results, avoids excessive calculation, and significantly improves the calculation efficiency; by scientifically setting the grid size and division method, the waste of excessive computing resources is avoided, and the accuracy of the numerical simulation is guaranteed.

[0057] S4: Obtain casing swept mesh data based on the first mesh and the second mesh to form a three-dimensional swept mesh.

[0058] Preferably, Figure 4 Shown is a cross-sectional view of the swept mesh. The casing swept mesh data includes the overall size and distribution of the casing swept mesh.

[0059] Preferably, forming the three-dimensional swept grid comprises the following steps: setting casing swept grid data based on the first grid and the second grid to ensure the continuity and quality of the grid during the sweeping process.

[0060] The rotation surface that can be rotated along the symmetry axis to form a complete casing in a 2D axisymmetric finite element analysis model is obtained, and the rotation surface is set as the source surface of the swept mesh.

[0061] A second rotation surface which is spaced from the source surface by a preset angle is set as a target surface of the swept mesh, wherein the preset angle is 360 degrees.

[0062] The size of the swept grid is refined based on the grid-independent solution standard to obtain a refined swept grid size, ensuring that the numerical simulation results of the thermal flow field of the entire casing are both accurate and efficient.

[0063] Based on the refined swept mesh size, the first mesh and the second mesh of the source surface are rotated along the symmetry axis to the target surface to generate a three-dimensional swept mesh, wherein the three-dimensional swept mesh retains the accuracy of the two-dimensional mesh and adapts to the three-dimensional structure of the casing.

[0064] Preferably, the swept grid generation method proposed in the present invention ensures the high efficiency and accuracy of the numerical simulation of the thermal flow field of the entire sleeve by combining the accuracy of the two-dimensional grid and the adaptability of the three-dimensional structure; by generating a three-dimensional swept grid by rotation, the three-dimensional heat conduction characteristics of the sleeve can be fully considered to ensure the accurate calculation of the thermal flow field at each point; it solves the problem of how to handle three-dimensional complex structures while ensuring accuracy, so that the three-dimensional thermal flow field of the sleeve can be simulated efficiently and accurately.

[0065] In summary, the present invention proposes an unstructured grid drawing method for numerical calculation of the thermal flow field of the bushing based on the sweeping method, which not only improves the efficiency of grid generation, but also effectively reduces the computational complexity of the thermal flow field analysis of the bushing, providing strong technical support for the design, optimization and safe operation of power equipment.

[0066] Embodiment 2 is an embodiment of the present invention, which provides an unstructured grid generation system for numerical calculation of thermal flow field of casing, including: a model building module, used to obtain the solid area and fluid area of ​​the casing and construct a finite element analysis model of the casing; a defect recognition module, used to preprocess the finite element analysis model of the casing, identify geometric defects in the fluid area and perform geometric shape division to obtain a reconstructed fluid area; a grid drawing module, used to grid the reconstructed fluid area and solid area in the finite element analysis model of the casing to obtain a first grid and a second grid; a grid generation module, used to obtain the overall size and distribution of the casing swept grid according to the first grid and the second grid, and then generate a three-dimensional swept grid.

[0067] Embodiment 3 is an embodiment of the present invention, which is different from the previous embodiment in that:

[0068] like Figure 5 As shown, if the function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0069] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0070] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0071] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0072] Example 4 is an embodiment of the present invention, which provides an unstructured grid generation method applied to the numerical calculation of the thermal flow field of the casing. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through simulation experiments.

[0073] In this example, the bushing in a 500kV substation is taken as the research object. The rated current of the bushing is 2000A, the outer diameter is 890mm, and the total height is 3200mm. The traditional structured grid method and the unstructured grid partitioning method of the present invention are used to perform numerical calculations of the thermal flow field of the bushing. First, the structural characteristics of the bushing are obtained, including solid areas such as conductors, flanges, and epoxy resin cores, and fluid areas such as filled SF6 gas and transformer oil, and a two-dimensional axisymmetric finite element analysis model containing complete geometric information and material physical parameters is constructed.

[0074] In the preprocessing stage, professional geometric detection algorithms are used to identify geometric defects in the model, mainly including sharp-angle geometric defects at the connection between the conductor and the flange, and slit geometric defects between the core and the flange. For these defects, a segmentation and reconstruction method based on topology optimization is used to reconstruct the sharp-angle area into a regular diamond structure and optimize the slit area into an equally spaced trapezoidal structure.

[0075] In the meshing stage, the mesh size of the reconstructed fluid area is first optimized. Through repeated iterative calculations, the optimal mesh size that meets the requirements of the mesh-independent solution is determined: the axial base size is 3 mm, and the radial base size is 2 mm; for the solid area, considering the heat generation and heat conduction characteristics of the conductor, the mesh is further refined: the axial mesh size is 2 mm, and the radial mesh size is 1.5 mm; on this basis, an improved mapping method is used to mesh the fluid area to generate a regular quadrilateral mesh, and an adaptive triangular meshing method is used for the solid area to better adapt to complex geometric shapes.

[0076] Finally, in the swept mesh generation stage, the two-dimensional mesh is rotated 360° along the axial direction to form a three-dimensional mesh. At the same time, in the heat flux intensive area and the area where the geometric features suddenly change, the mesh density is improved by local encryption to ensure the calculation accuracy of these key areas. Tables 1 and 2 show the mesh quality comparison table and calculation performance comparison table of different mesh division methods.

[0077] Table 1 Comparison of mesh quality of different meshing methods

[0078] Meshing method Total number of grids (10,000) Mesh distortion rate (%) Boundary layer mesh quality indicators Traditional structured grid 156.8 8.45 0.82 Ordinary unstructured grid 142.3 6.78 0.85 Method of the present invention 122.3 3.45 0.95

[0079] Table 2 Comparison of computational performance of different meshing methods

[0080] Meshing method Calculation time (h) Memory usage (GB) Maximum error of temperature field (%) Traditional structured grid 12.6 24.8 4.26 Ordinary unstructured grid 10.4 22.3 3.85 Method of the present invention 7.5 17.8 2.12

[0081] It can be seen from Table 1 and Table 2 that the unstructured grid generation method proposed in the present invention has significant advantages over the traditional method. From the perspective of overall performance indicators, the total number of grids is reduced by about 22% by using the composite optimization method of the present invention, while the grid distortion rate is significantly reduced to 3.45%, which is much better than 8.45% of the traditional structured grid. At the same time, the boundary layer grid quality index is improved to 0.95, which meets the ideal requirements. These improvements are directly reflected in the computational efficiency. The computational time is reduced from 12.6 hours to 7.5 hours, the memory usage is reduced by 28.2%, and the maximum error of the temperature field is reduced to 2.12%. This shows that the method of the present invention first performs geometric preprocessing, then optimizes the grid size, and finally forms a high-quality three-dimensional grid through a sweeping strategy, which effectively reduces the computational complexity of the casing thermal flow field analysis and improves the efficiency of grid generation.

[0082] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. An unstructured grid generation method for numerical calculation of thermal flow field of casing, characterized by: include: Obtain the structural characteristics of the casing and build a finite element analysis model of the casing; Preprocessing the casing finite element analysis model, identifying geometric defects and performing geometric shape division; Grid drawing is performed based on the fluid region and the solid region of the casing finite element analysis model to obtain a first grid and a second grid; The casing swept mesh data is obtained based on the first mesh and the second mesh to form a three-dimensional swept mesh.

2. The unstructured grid generation method for the numerical calculation of the thermal flow field of a casing according to claim 1, characterized in that: The structural features of the casing include a solid region and a fluid region; The solid region includes a conductor, a flange and a core; The fluid region includes air and oil; The bushing finite element analysis model is used to analyze the heat flow field distribution under the natural convection phenomenon generated by the fluid medium filled in the bushing when the bushing conductor is energized and heated; The casing finite element analysis model is a two-dimensional axisymmetric model containing detailed geometric information and material properties.

3. The unstructured grid generation method for the numerical calculation of the thermal flow field of a casing according to claim 2, characterized in that: The construction of the casing finite element analysis model comprises the following steps: Obtain the structural characteristics of the bushing, including three solid regions of conductor, flange and core, and two fluid regions of air and oil; Construct a two-dimensional axisymmetric structure of conductor, flange, core, air and oil, and generate a two-dimensional axisymmetric finite element analysis model; The symmetry axis is marked in the two-dimensional axisymmetric finite element analysis model, and the rotation surface of the two-dimensional axisymmetric finite element analysis model that can form a complete casing by rotating along the symmetry axis is marked.

4. The unstructured grid generation method for the numerical calculation of the thermal flow field of a casing according to claim 3, characterized in that: The geometric defects include sharp corner geometric defects and slit geometric defects; The geometric shape division is used to simplify the mesh generation process while maintaining the ability to capture key features of the thermal flow field; The method of identifying geometric defects and performing geometric shape division comprises the following steps: Preprocessing the two-dimensional axisymmetric finite element analysis model to identify geometric defects that are difficult to directly mesh, including sharp corner geometric defects and slit geometric defects; Dividing the geometric defect into geometric shapes by segmentation or reassembly to obtain a geometric shape including two sets of opposite edges; The fluid region in the two-dimensional axisymmetric finite element analysis model is reconstructed based on the geometric shape including the two sets of opposite edges to obtain a reconstructed fluid region.

5. The unstructured grid generation method for the numerical calculation of the thermal flow field of a casing according to claim 4, characterized in that: The obtaining of the first grid and the second grid comprises the following steps: Based on the requirements of thermal flow field analysis, an axial grid size and a radial grid size of the reconstructed fluid region are set; Based on the requirements of thermal flow field analysis, an axial mesh size and a radial mesh size of a solid region in the two-dimensional axisymmetric finite element analysis model are set; Based on the lower limit of the mesh size, a first mesh is drawn in the fluid region of the rotation surface of the two-dimensional axisymmetric finite element analysis model using a mapping method; Based on the lower limit of the mesh size, a second mesh is drawn in the solid area of ​​the rotation surface using a free triangle meshing method.

6. The unstructured grid generation method for the numerical calculation of the thermal flow field of a casing according to claim 5, characterized in that: Setting the axial grid size and radial grid size of the reconstructed fluid region and solid region refers to the criterion of refining the grid size to a grid-independent solution; The standard of the grid-independent solution refers to comparing the calculation results under different grid densities after multiple trial calculations, and then obtaining the lower limit of the grid size that meets the accuracy requirements.

7. The unstructured grid generation method for the numerical calculation of the thermal flow field of a casing according to claim 6, characterized in that: The casing swept grid data includes the overall size and distribution of the casing swept grid; The forming of the three-dimensional swept grid comprises the following steps: Setting casing sweeping grid data based on the first grid and the second grid; Acquire a rotation surface that can form a complete casing by rotating along the symmetry axis in the two-dimensional axisymmetric finite element analysis model, and set the rotation surface as a source surface of the swept mesh; Setting a second rotating surface which is spaced by a preset angle from the source surface as a target surface of the swept mesh; Refining the size of the swept grid based on the standard of the grid-independent solution to obtain a refined swept grid size; Based on the refined swept mesh size, the first mesh and the second mesh of the source surface are rotated along the symmetry axis to the target surface to generate a three-dimensional swept mesh.

8. An unstructured grid generation system for numerical calculation of thermal flow field of casing, based on the unstructured grid generation method for numerical calculation of thermal flow field of casing as claimed in any one of claims 1 to 7, characterized in that: include, A model building module, used for obtaining the solid region and fluid region of the casing and building a finite element analysis model of the casing; The defect recognition module is used to pre-process the casing finite element analysis model, identify geometric defects in the fluid area and divide the geometric shape to obtain the reconstructed fluid area; A mesh drawing module is used to draw meshes on the reconstructed fluid region and solid region in the casing finite element analysis model to obtain a first mesh and a second mesh; The grid generation module is used to obtain the overall size and distribution of the casing swept grid according to the first grid and the second grid, and then generate a three-dimensional swept grid.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the unstructured grid generation method for numerical calculation of thermal flow field of a casing as described in any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the unstructured grid generation method for numerical calculation of thermal flow field of a casing as claimed in any one of claims 1 to 7 are implemented.

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