A method for automatically generating a non-structural grid of a moving blade gas seal body

Abstract

The application discloses a method for automatically generating a non-structural grid of a moving blade gas seal body, and particularly relates to the technical field of computational fluid dynamics preprocessing and turbine mechanical digitization design. The method is realized through the following steps: a 21-dimension gas seal modeling parameter array supporting switching between a simplified mode and a full parameter mode, a type line point set, a grid growth rate and boundary surface naming parameters; a gas seal fluid three-dimensional geometric model containing steps, long and short teeth and type line cutting features is automatically constructed by using an Open CASCADE geometric kernel; surface grid and body grid are generated in sequence by calling a grid generator; and grid surface grouping and naming are automatically completed based on the ID distribution law of the grid surface. The method integrates a tedious and time-consuming manual operation process into a parameter-driven minute-level automatic process without manual intervention, and the generated grid can be directly used for simulation calculation, so that the technical problem that the gas seal grid is difficult to be integrated into a blade automatic optimization iteration process is effectively solved.

Description

Technical Field

[0001] This invention relates to the field of computational fluid dynamics preprocessing and digital design technology of turbine machinery, and more specifically, to a method for automatically generating unstructured meshes for moving blade air seals. Background Technology

[0002] In the aerodynamic design of turbomachinery (such as steam turbines, compressors, and gas turbines), the moving blade gas seal is a key component for controlling leakage flow at the blade tip, and its performance directly affects the overall efficiency and operational safety of the machine. To obtain accurate flow field characteristics within the gas seal, a three-dimensional geometric model of the gas seal fluid needs to be established and computational fluid dynamics (CFD) simulation analysis performed. Modern turbomachinery design processes widely employ blade linear adaptive optimization technology. This technology requires the rapid generation of corresponding gas seal meshes for each set of design parameters during the optimization iteration process to support large-scale, unattended automated simulation calculations. Therefore, the efficiency, stability, and automation level of gas seal mesh generation have become bottlenecks restricting the entire blade optimization process.

[0003] However, existing air seal mesh generation processes suffer from the following insurmountable drawbacks. First, the process is fragmented and inefficient. In the traditional workflow, engineers must first manually complete the 3D model of the air seal flow channel in CAD software, then import the geometric model into pre-processing software such as Hypermesh and ICEM for geometry cleanup, mesh size setting, surface and volume mesh generation, and finally pick and group the boundary surfaces one by one. The mesh generation process for a single air seal body typically takes several hours, and once the design parameters change, the above process must be repeated from scratch, which is completely unsuitable for the optimization algorithm's requirements for large sample sizes and high-speed iteration. Second, existing processes are difficult to automate. Current mainstream commercial pre-processing software heavily relies on graphical user interface (GUI) operations. Although some software provides script recording functions, their stability is poor, portability is low, and they cannot be encapsulated as standard application programming interfaces (APIs) for upper-level optimization platforms to call, let alone achieve deep integration in low-level development environments such as C++. Third, the boundary surface grouping stage has a high error rate. The geometry of the gas seal includes multiple sets of boundary surfaces such as the inlet surface, outlet surface, rotor surface, stator surface, and periodic side surfaces. Among them, the rotor surface and stator surface are associated with the features of steps and gas seal teeth. Manually picking and naming these surfaces one by one in the graphical interface is very easy to result in omissions, incorrect selections, or duplicate selections. Once the boundary conditions are set incorrectly, it will directly lead to the failure of the subsequent CFD solver to read or the calculation diverges, which will seriously affect the reliability of the simulation.

[0004] In summary, existing gas seal mesh generation technologies suffer from significant drawbacks, including excessive manual intervention, long processing times, inability to integrate into automated optimization processes, and high boundary surface grouping error rates. Therefore, there is an urgent need for an end-to-end solution capable of receiving parametric input and automatically completing the entire process from geometric modeling and mesh generation to intelligent boundary surface grouping. This solution would achieve zero-human interaction and minute-level response in gas seal mesh generation, thereby meeting the automation requirements of CFD preprocessing for turbine blade aerodynamic optimization. Summary of the Invention

[0005] To overcome the above-mentioned defects of the prior art, embodiments of the present invention provide an automatic method for generating unstructured meshes for moving blade air seals.

[0006] To achieve the above objectives, the present invention provides the following technical solution: An automatic method for generating unstructured meshes for moving blade air seals includes the following steps: Receive input parameters, including an array of air seal modeling parameters, a set of discrete points for two profiles, a grid growth rate parameter, and boundary surface naming parameters; Using the Open CASCADE geometric kernel, a three-dimensional geometric model of the gas seal fluid is automatically constructed based on the array of gas seal modeling parameters and the discrete point set of the two profiles. The mesh generator is invoked to first generate an unstructured surface mesh from the three-dimensional geometric model, and then an unstructured volume mesh is generated based on the surface mesh. The analytical volume mesh file automatically identifies mesh surface elements based on the distribution pattern of mesh surface IDs, divides them into six surface groups: inlet surface, outlet surface, stator surface, rotor surface, and two periodic side surfaces, and writes the grouped mesh surface data into the CGNS file and outputs it.

[0007] Specifically, the air seal design parameter array contains 21 dimensions and supports switching between simplified mode and full parameter mode; In simplified mode, only six core parameters need to be input: axial position of air inlet, radial position of air inlet, axial position of air outlet, radial position of air outlet, air seal gap, and tooth pitch. The remaining styling parameters are automatically assigned default values ​​by the system, which are automatically calculated based on the core parameters. In full-parameter mode, the individual styling parameters of steps, long teeth, and short teeth can be edited independently.

[0008] Specifically, the construction of the three-dimensional geometric model of the gas-sealing fluid includes: Construct a basic rotating body along the rotation axis based on the axial and radial positions of the air inlet and outlet. Based on the number of steps, long teeth, and short teeth calculated from the air seal modeling parameter array, the corresponding air seal tooth shape and step entity are linearly arrayed along the axial direction on the basic rotating body, and the basic air seal body is generated through Boolean subtraction operation; Based on the discrete point set of two profile lines, two contour curves are fitted to form an air seal profile. The air seal profile is then stretched radially to create an air seal shape cutout. The intersection of the gas seal model cutout and the basic gas seal body is calculated by Boolean intersection operation to obtain the final three-dimensional geometric model of the gas seal fluid.

[0009] Specifically, the number of steps Number of long teeth and short tooth count relative to the axial position of the air outlet Axial position of air intake Tooth spacing Satisfying the relation: , , .

[0010] Specifically, the generation of unstructured surface meshes and unstructured volume meshes includes: Output the 3D geometric model as a STEP format file; The mesh generator is invoked to read STEP geometry data, generate unstructured surface meshes according to the set surface mesh growth rate, and output surface mesh files; Call the mesh generator to read the surface mesh data, generate an unstructured volume mesh according to the set volume mesh growth rate, and output the volume mesh file.

[0011] Specifically, the mesh generator is invoked via command line or script interface, passing the file path, face mesh growth rate, and volume mesh growth rate as execution parameters.

[0012] Specifically, the automatic identification of grid surface units based on the distribution pattern of grid surface IDs includes: The air intake surface occupies a fixed ID of 5; The air outlet surface ID is determined based on the number of steps; The rotor face corresponds to the root annular surface of all steps and air seal teeth, and its ID interval is determined according to the number of steps; The stator face corresponds to all tooth tip annular surfaces, and its ID range is determined by the IDs of other faces. The two periodic sides occupy fixed IDs of 2 and 4 respectively.

[0013] Specifically, the air outlet surface and the number of steps The following correspondence is satisfied: The ID of the air outlet surface is .

[0014] Specifically, the ID range and the number of steps of the rotor surface The following correspondence is satisfied: The rotor surface starts with ID 6 and ends with ID 6. .

[0015] Specifically, the method is implemented in the form of a C++ class, providing a parameterized static function interface that can be compiled into a dynamic link library and embedded into the blade aerodynamic optimization platform.

[0016] The technical effects and advantages of this invention are as follows: This invention receives a 21-dimensional array of air seal modeling parameters and supports switching between simplified and full-parameter modes. It automatically constructs a 3D model of the air seal body, incorporating features such as steps, short and long teeth, and profile trimming, using the Open CASCADE geometric kernel. Then, it calls a mesh generator to sequentially generate surface and volume meshes. Finally, based on the distribution of mesh surface IDs, all mesh surfaces are automatically divided into six face groups: inlet face, outlet face, stator face, rotor face, and two periodic side faces, and written into a CGNS file. This achieves end-to-end automation from parameter input to simulateable mesh output. This method reduces the traditional hours-long manual modeling, mesh generation, and boundary naming operations to minutes, requiring no manual interaction and completely eliminating boundary naming errors caused by manually picking similar geometric surfaces. Furthermore, the overall solution is implemented in C++ classes, providing a parameterized static function interface that can be compiled into a dynamic link library and directly embedded into the blade aerodynamic optimization platform, significantly improving the efficiency and integration of CFD preprocessing in the digital design process of turbine machinery. Attached Figure Description

[0017] Figure 1 This is an overall flowchart of the present invention; Figure 2 This is a schematic diagram of the structure of the blade moving blade air seal body in this invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] like Figure 1 As shown, the steps of an automatic generation method for unstructured mesh of a moving blade air seal are as follows: Step 1: Receive input parameters. The air seal design parameter array contains 21 dimensions and supports switching between simplified and full-parameter modes. In simplified mode, only six core parameters need to be input: axial position of the air inlet, radial position of the air inlet, axial position of the air outlet, radial position of the air outlet, air seal clearance, and tooth pitch. The remaining design parameters are automatically assigned default values ​​by the system. In full-parameter mode, the design parameters for the steps, long teeth, and short teeth can be edited independently.

[0020] Step two: Using the Open CASCADE geometry kernel, construct the basic solid of revolution along the rotation axis based on the axial and radial positions of the air inlet and outlet; wherein, the number of steps... Short tooth count Number of long teeth The distance between the inlet and outlet axial directions and the tooth pitch are jointly determined, satisfying the following relationship: , , In the formula This refers to the axial position of the air outlet. This refers to the axial position of the air intake. The tooth spacing is defined as follows: Based on the calculated number of steps, long teeth, and short teeth, as well as the shaping parameters, the corresponding tooth shapes and step entities are linearly arrayed along the axial direction on the basic rotating body. Boolean subtraction operations are used to excavate the step and air seal tooth shapes, generating the basic air seal body. On this basis, based on the discrete point sets of the two profile lines, B-spline curve fitting is used to generate two contour curves. The ends of the curves are connected to form the air seal surface. The air seal surface is then stretched radially to create the air seal shape cut-out body. Finally, Boolean intersection operations are used to calculate the intersection of the air seal shape cut-out body and the basic air seal body to obtain the final three-dimensional geometric model of the air seal fluid.

[0021] Step 3: Output the 3D geometric model generated in Step 2 as a STEP format file. Call the mesh generator to read the STEP geometric data, generate an unstructured surface mesh according to the set surface mesh growth rate, and output the surface mesh file. Subsequently, call the mesh generator to read the surface mesh data, generate an unstructured volume mesh according to the set volume mesh growth rate, and output the volume mesh file.

[0022] Step 4: Parse and save the mesh nodes, elements, and index data in the volume mesh. Based on the ID distribution pattern of the mesh faces in the volume mesh file, the general derivation rule is: the inlet face occupies a fixed ID of 5, and the two periodic side faces occupy fixed IDs of 2 and 4; the outlet face ID is related to the number of steps, satisfying the following relationship: The rotor face corresponds to the root annular surface of all steps and air seal teeth. Its initial ID is fixed at 6, and its ending ID is related to the number of steps, satisfying the following relationship: The stator face corresponds to all tooth tip annular surfaces, and its ID is determined by the IDs of other faces. After traversing all mesh faces, the system automatically assigns the mesh face IDs to the above 6 groups according to this rule.

[0023] Merge the mesh surfaces in the corresponding ID range, write them into the corresponding boundary condition nodes in the CGNS file, and write the entire volume mesh according to the input name. Finally, output the gas seal mesh CGNS file with grouped names.

[0024] Through the above steps, the entire process of generating the air seal mesh is integrated into a parameter-driven, end-to-end automated workflow. The overall solution is implemented in the form of C++ classes, providing parameterized static function interfaces that can be compiled into dynamic link libraries and directly embedded into integrated environments such as blade aerodynamic optimization platforms.

[0025] The method of the present invention will be further illustrated by the following embodiment: Taking the generation of an unstructured mesh for the moving blade gas seal of a heavy-duty gas turbine blade as an example, the simplified input parameter mode is used in this embodiment. The rotation axis is set as the Z-axis, the axial direction is the positive Z-axis, and the radial direction is the positive X-axis. The received parameters include: the axial position of the inlet is 75.0 mm, the radial position of the inlet is 483.9 mm, the axial position of the outlet is 175.0 mm, the radial position of the outlet is 487.6 mm, the gas seal gap is 0.8 mm, the tooth pitch is 15.0 mm, and the discrete point set of the two profiles. At the same time, the boundary names are set: the inlet surface is named In, the outlet surface is named Out, the stator surface is named Static, the rotor surface is named Rotor, the two periodic side surfaces are named Per1 and Per2 respectively, the overall mesh is named Seal_R1, and the surface mesh growth rate is set to 1.5 and the volume mesh growth rate is set to 1.1.

[0026] In the geometric construction step, a basic solid of revolution is created along the Z-axis based on the inlet and outlet parameters. Steps, long teeth, and short teeth are generated using default parameters. The number of steps (5), short teeth (5), and long teeth (6) are calculated based on the tooth spacing and inlet / outlet parameters. The corresponding number of solids are then linearly arrayed along the Z-axis, and the basic air seal body is formed through Boolean subtraction. B-spline fitting is performed on the discrete point sets of the two profile lines to generate the contour curve and create the air seal profile. This profile is then radially extruded to form the air seal shape cut-out body, and finally, the final air seal geometric model is obtained through Boolean intersection.

[0027] In the mesh generation step, the geometric model is first output as a STEP file. The mesh generator is then called to generate a surface mesh at a face mesh growth rate of 1.5 and output the file. Then, the surface mesh data is read to generate a volume mesh at a volume mesh growth rate of 1.1 and output the volume mesh file. At the same time, the volume mesh data is parsed and saved.

[0028] In the automatic grouping and output step, based on the distribution pattern of the number of steps, long teeth, and short teeth and the mesh surface IDs, the mesh surfaces belonging to the rotor surface ID interval [6,28] are merged and written into the CGNS node named "Rotor". The other five surface groups are written into their corresponding nodes according to the same rules. Finally, the overall mesh is named "Seal_R1", and a complete CGNS mesh file is output. The generated file contains approximately 18,000 tetrahedral elements, and the mesh quality meets the requirements of commercial CFD solvers. It can be directly used for blade aerodynamic optimization iterative calculations without manual interaction.

[0029] The above formulas are all dimensionless calculations. Dimensionless calculations can be performed using various methods such as standardization, which will not be elaborated here. The formulas are derived from software simulations based on a large amount of collected data, and the preset parameters in the formulas can be set by those skilled in the art according to the actual situation.

[0030] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, as a computer program product. The computer program product includes one or more computer instructions or computer programs. When the computer instructions or computer programs are loaded or executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired or wireless (e.g., infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more sets of available media. The available medium can be a magnetic medium (e.g., floppy disk, ATA hard disk, magnetic tape, mechanical hard disk, solid-state hard disk (SSD)), an optical medium (e.g., DVD), or a semiconductor medium. The semiconductor medium can be a solid-state ATA hard disk.

[0031] It should be understood that in the various embodiments of this application, the order of the above-mentioned processes does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0032] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0033] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0034] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0035] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0036] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable ATA hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0037] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for automatically generating unstructured meshes for moving blade air seals, characterized in that, Includes the following steps: Receive input parameters, including an array of air seal modeling parameters, a set of discrete points for two profiles, a grid growth rate parameter, and boundary surface naming parameters; Using the Open CASCADE geometric kernel, a three-dimensional geometric model of the gas seal fluid is automatically constructed based on the array of gas seal modeling parameters and the discrete point set of the two profiles. The mesh generator is invoked to first generate an unstructured surface mesh from the three-dimensional geometric model, and then an unstructured volume mesh is generated based on the surface mesh. The analytical volume mesh file automatically identifies mesh surface elements based on the distribution pattern of mesh surface IDs, divides them into six surface groups: inlet surface, outlet surface, stator surface, rotor surface, and two periodic side surfaces, and writes the grouped mesh surface data into the CGNS file and outputs it.

2. The method for automatically generating unstructured meshes for moving blade air seals according to claim 1, characterized in that, The air seal design parameter array contains 21 dimensions and supports switching between simplified mode and full parameter mode. In simplified mode, only six core parameters need to be input: axial position of air inlet, radial position of air inlet, axial position of air outlet, radial position of air outlet, air seal gap, and tooth pitch. The remaining styling parameters are automatically assigned default values ​​by the system, which are automatically calculated based on the core parameters. In full-parameter mode, the individual styling parameters of steps, long teeth, and short teeth can be edited independently.

3. The method for automatically generating unstructured meshes for moving blade air seals according to claim 1, characterized in that, The construction of the three-dimensional geometric model of the gas-sealed fluid includes: Construct a basic rotating body along the rotation axis based on the axial and radial positions of the air inlet and outlet. Based on the number of steps, long teeth, and short teeth calculated from the air seal modeling parameter array, the corresponding air seal tooth shape and step entity are linearly arrayed along the axial direction on the basic rotating body, and the basic air seal body is generated through Boolean subtraction operation; Based on the discrete point set of two profile lines, two contour curves are fitted to form an air seal profile. The air seal profile is then stretched radially to create an air seal shape cutout. The intersection of the gas seal model cutout and the basic gas seal is calculated by Boolean intersection operation to obtain the final three-dimensional geometric model of the gas seal.

4. The method for automatically generating unstructured meshes for moving blade air seals according to claim 3, characterized in that, The number of steps Number of long teeth and short tooth count relative to the axial position of the air outlet Axial position of air intake Tooth spacing Satisfying the relation: ， ， 。 5. The method for automatically generating unstructured meshes for moving blade air seals according to claim 1, characterized in that, The generation of unstructured surface meshes and unstructured volume meshes includes: Output the 3D geometric model as a STEP format file; The mesh generator is invoked to read STEP geometry data, generate unstructured surface meshes according to the set surface mesh growth rate, and output surface mesh files; Call the mesh generator to read the surface mesh data, generate an unstructured volume mesh according to the set volume mesh growth rate, and output the volume mesh file.

6. The method for automatically generating unstructured meshes for moving blade air seals according to claim 5, characterized in that, The mesh generator can be invoked via command line or script interface, passing the file path, face mesh growth rate, and volume mesh growth rate as execution parameters.

7. The method for automatically generating unstructured meshes for moving blade air seals according to claim 1, characterized in that, The automatic identification of grid surface units based on the distribution pattern of grid surface IDs includes: The air intake surface occupies a fixed ID of 5; The air outlet surface ID is determined based on the number of steps; The rotor face corresponds to the root annular surface of all steps and air seal teeth, and its ID interval is determined according to the number of steps; The stator face corresponds to all tooth tip annular surfaces, and its ID range is determined by the IDs of other faces. The two periodic sides occupy fixed IDs of 2 and 4 respectively.

8. The method for automatically generating unstructured meshes for a moving blade air seal according to claim 7, characterized in that, The air outlet surface ID and the number of steps The following correspondence is satisfied: The ID of the air outlet surface is .

9. The method for automatically generating unstructured meshes for moving blade air seals according to claim 7, characterized in that, The ID range and step number of the rotor surface The following correspondence is satisfied: The rotor surface starts with ID 6 and ends with ID 6. .

10. The method for automatically generating unstructured meshes for moving blade air seals according to claim 1, characterized in that, The method is implemented in the form of a C++ class, providing a parameterized static function interface that can be compiled into a dynamic link library and embedded into a blade aerodynamic optimization platform.

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