Multi-scale high-quality mesh generation method for magnetic liquid sealing structure of rotating shaft

Abstract

The invention belongs to the technical field of mechanical engineering magnetic liquid sealing, and particularly relates to a multi-scale high-quality mesh generation method for a rotating shaft magnetic liquid sealing structure, which comprises the following steps: constructing a two-dimensional axisymmetric magnetic liquid sealing model; importing the two-dimensional axisymmetric magnetic liquid sealing model into a grid division tool for grid division to obtain a target grid file; and detecting the precision of each grid in the target grid file, and if a preset precision index is met, outputting the target grid file. According to the method, an encryption area needing high-precision calculation and a relatively secondary non-encryption area are accurately defined based on a regional partitioning strategy, so that unnecessary calculation burden caused by global encryption is effectively avoided; meanwhile, according to the characteristics that the size of the encrypted area is small and the magnetic flux density changes extremely violently, a two-in-one grid transition strategy is innovatively introduced into the junction of the encrypted area and the non-encrypted area, and the structured multi-scale grid layout is achieved while it is ensured that the grids are smoothly transited from high density to low density.

Description

Technical Field

[0001] The invention belongs to the technical field of magnetic liquid seals in mechanical engineering, and in particular relates to a multi-scale high-quality grid division method for a rotating shaft magnetic liquid seal structure. Background Art

[0002] Magnetic liquid seals are widely used in key fields such as energy electronics, aerospace, and medical health. Their sealing performance is directly affected by the magnetic circuit characteristics of electromagnets or permanent magnets. However, when dividing the magnetic field simulation grid, the seal design faces a major challenge: the sealing gap is extremely small and the overall structure size is huge, forming a significant multi-scale feature. This leads to uneven quality of the automatically generated meshes, and the mesh density tends to be consistent, which is difficult to meet the needs of fine calculations. If you try to improve the calculation accuracy by reducing the mesh size, the total number of meshes will increase sharply, thereby significantly reducing the calculation efficiency. In view of the key role of meshing in ensuring the accuracy of the calculation results and improving the calculation efficiency, meshing in the pre-processing stage is particularly important in the finite element simulation process. Therefore, it is urgent to develop a meshing optimization strategy to ensure the calculation accuracy while effectively improving the simulation efficiency. Summary of the invention

[0003] In view of the shortcomings of the above-mentioned prior art, the present invention provides a multi-scale high-quality meshing method for a rotating shaft magnetic liquid seal structure, and develops a meshing optimization strategy to cope with the multi-scale challenges of tiny sealing gaps and huge overall structural dimensions, while ensuring calculation accuracy and effectively improving simulation efficiency.

[0004] According to the characteristics of the magnetic liquid sealing structure and the simulation requirements, the present invention accurately defines the encrypted area requiring high-precision calculation and the relatively minor non-encrypted area based on the regional blocking strategy, effectively avoiding the unnecessary calculation burden brought by the global encryption; at the same time, in view of the characteristics of the small size of the encrypted area and the extremely drastic change in magnetic flux density, an innovative "two-in-one" grid transition strategy is introduced at the junction of the encrypted area and the non-encrypted area, which ensures a smooth transition of the grid from high density to low density while realizing a structured multi-scale grid layout. This innovation not only ensures the high-precision requirements in the fine structure, but also takes into account the improvement of the overall calculation efficiency.

[0005] The present invention provides a multi-scale high-quality grid division method for a rotary shaft magnetic liquid sealing structure, and the specific steps are:

[0006] S1. Establish theoretical parameters of sealing geometry model and construct two-dimensional axisymmetric magnetic liquid sealing model;

[0007] S2. Import the two-dimensional axisymmetric magnetic liquid seal model into a meshing tool for meshing to obtain a target mesh file. The meshing tool is Hypermesh. The specific meshing steps are as follows:

[0008] S21, after importing the two-dimensional axisymmetric magnetic liquid seal model into the mesh generation tool, finding the symmetry line of the two-dimensional axisymmetric magnetic liquid seal model and dividing it into two completely identical parts, namely, part A and part B, along the symmetry line;

[0009] S22, randomly select one of parts A and B as a model to be divided into meshes, and obtain a first mesh file;

[0010] S23, symmetrically copying the first grid file to the other side along the symmetry line to obtain a second grid file;

[0011] S24, performing a common node operation on the first grid file and the second grid file to complete the grid division of the two-dimensional axisymmetric magnetic liquid seal model and obtain a target grid file;

[0012] S3. Check the accuracy of each grid in the target grid file. If the preset accuracy index is met, the division is completed and the target grid file is output; otherwise, modify the non-compliant area in the grid until the preset accuracy index is met and stop.

[0013] Preferably, the theoretical parameters of the sealing geometric model include the radius of the rotating shaft, the inner diameter, outer diameter and thickness of the pole shoe, the sealing gap s, the inner diameter, outer diameter and thickness of the permanent magnet, the number of pole teeth, the pole tooth height h, the pole tooth width d1, and the pole tooth slot width d2;

[0014] The two-dimensional axisymmetric magnetic liquid sealing model includes a rotating shaft, an upper pole shoe, a permanent magnet, a lower pole shoe, an air domain and a shell, wherein the rotating shaft is arranged in the shell, and two pole shoes arranged up and down are sleeved on the rotating shaft, namely an upper pole shoe and a lower pole shoe, and a permanent magnet is arranged between the upper pole shoe and the lower pole shoe to fit the two, and multiple magnetic circuits are arranged between the rotating shaft, the upper pole shoe, the permanent magnet and the lower pole shoe, and the gap formed by the pole shoe and the rotating shaft in the magnetic circuit has magnetic liquid.

[0015] Preferably, in step S22, different division strategies are adopted for each area based on the regional block strategy according to the importance and calculation requirements of each area, wherein the specific strategies are: for the encrypted area, a fine grid division strategy is adopted, that is, the axial size of the grid in the encrypted area and the radial size of the grid in the encrypted area are much smaller than the axial size of the grid in the non-encrypted area and the radial size of the grid in the non-encrypted area; for the non-encrypted area, a sparse grid division strategy is adopted, that is, the axial size of the grid in the non-encrypted area and the radial size of the grid in the non-encrypted area are much larger than the axial size of the grid in the encrypted area and the radial size of the grid in the encrypted area; for the transition area, a "two-in-one" grid transition method is adopted, that is, the grid size of the transition area gradually transitions between the two;

[0016] In addition, the step S22 is specifically divided into the following steps:

[0017] S221, based on the physical characteristics, geometric shape and simulation requirements of the model to be divided, dividing the model to be divided into different areas, including an encrypted area, a transition area and a non-encrypted area;

[0018] S222, setting encryption area parameters, transition area parameters and non-encryption area parameters;

[0019] S223, based on the set encryption area parameters, the encryption area is grid-divided;

[0020] S224, based on the set encrypted area parameters, transition area parameters and non-encrypted area parameters, the transition area is meshed by using a "two-in-one" mesh transition method, wherein the "two-in-one" mesh transition method is specifically: m transition layers are constructed between the encrypted area and the non-encrypted area, and the mesh size is enlarged layer by layer, that is, the axial / radial size of the mesh unit of each transition layer is twice that of the previous layer, so as to realize a gradual transition from a high-density mesh to a low-density mesh;

[0021] S225, based on the set non-encrypted area parameters, the non-encrypted area is grid-divided;

[0022] S226, performing a common node operation on the meshes of the encrypted area, the transition area, and the non-encrypted area to complete the mesh division of the model to be divided, and obtaining a first mesh file.

[0023] Preferably, the densified area is the pole teeth on the pole shoe and the corresponding sealing gap area, the transition area is the area where the densified area transitions to the non-densified area, and the non-densified area is the remaining area outside the densified area and the transition area;

[0024] In addition, the encrypted area parameters include the encrypted area axial size, the encrypted area grid axial size, the encrypted area radial size and the encrypted area grid radial size, the transition area parameters include the number of transition layers, and the non-encrypted area parameters include the non-encrypted area grid axial size and the non-encrypted area grid radial size, wherein the calculation formula for the number of transition layers is as follows:

[0025]

[0026] In the formula, m represents the number of transition layers, x 11 Indicates the axial size of the mesh in the encrypted area, x 12 Indicates the radial size of the mesh in the encrypted area, x 21 Indicates the axial size of the grid in the non-refined area, x 22 Represents the radial size of the grid in the non-refinement area.

[0027] Preferably, the number of transition layers and the number of mesh axes in the dense area are 11 Need to meet ∈even number, where a 11 It is obtained by combining the axial size of the densified area and the axial size of the densified area grid; at the same time, the number of transition layers and the radial number of densified area grids a 12 Also need to satisfy ∈even number, where a 12 It is obtained by combining the radial size of the encrypted area with the radial size adjustment of the encrypted area grid.

[0028] Preferably, the specific steps of step S224 are:

[0029] a. Double the axial size and radial size of the mesh in the densified area to serve as the axial size and radial size of the mesh in the first transition layer;

[0030] b. Based on the axial size and radial size of the first transition layer grid determined in step a, dividing the first transition layer grid outside the densification area;

[0031] c. Double the axial size and radial size of the first transition layer grid to serve as the axial size and radial size of the second transition layer grid;

[0032] d. based on the axial size and radial size of the second transition layer grid determined in step c, dividing the second transition layer grid outside the first transition layer;

[0033] e. Repeat steps c and d, each time doubling the axial and radial dimensions of the current transition layer grid and expanding a new transition layer grid outward until the mth transition layer grid is divided and stops;

[0034] f. Perform a common node operation on the grids of the m transition layers, and the grid division of the transition area is completed, forming a smooth transition area with a gradually decreasing grid density from the encrypted area to the peripheral area.

[0035] Preferably, each grid in the transition layer is composed of a plurality of quadrilateral small grids having at least one right angle, and the plurality of small grids constituting each grid may include a variety of shapes;

[0036] In addition, the ratio of the number of grids in the current transition layer to the number of grids in the transition layer immediately below it is 2:1.

[0037] Preferably, each grid in the transition layer is composed of two right-angled trapezoidal small grids and one regular quadrilateral small grid, wherein the side lengths of the regular quadrilaterals on the upper base of the right-angled trapezoids are equal to the size of the grid of the previous layer, and the lower base of the right-angled trapezoids is equal to the size of the grid of the current layer, and the three small grids include two arrangement modes in the grid: ① the left diagonal of the regular quadrilateral small grid coincides with the lower left diagonal of the grid, and two right-angled trapezoidal small grids are arranged on the lower left diagonal of the grid, and the hypotenuses of the two right-angled trapezoidal small grids coincide with the upward extension line of the left diagonal of the regular quadrilateral; ② the right diagonal of the regular quadrilateral small grid coincides with the lower right diagonal of the grid, and two right-angled trapezoidal small grids are arranged on the lower right diagonal of the grid, and the hypotenuses of the two right-angled trapezoidal small grids coincide with the upward extension line of the right diagonal of the regular quadrilateral;

[0038] In addition, in each transition layer, the grids appear alternately in two different arrangements; at the same time, in each transition layer, at both end boundaries in contact with the non-reinforced area, the lower base of the right-angled trapezoidal small grid is directly connected to the grid boundary of the non-reinforced area.

[0039] Preferably, the encrypted zone, transition zone and non-encrypted zone are all quadrilateral grids, among which the encrypted zone and the non-encrypted zone are regular quadrilateral grids; at the same time, due to the progressive influence of multiple transition layers in the transition zone, the grid shape in the non-encrypted zone that overlaps with the axial / radial extension of these transition layers is rectangular.

[0040] Preferably, the preset accuracy index is that the Jacobian value of each grid in the target grid file is ≥ 0.6.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. Based on the unique properties of the magnetic liquid sealing structure and the precise simulation requirements, the present invention uses a sophisticated regional block strategy to clearly distinguish between the encrypted area with extremely high requirements for calculation accuracy and the relatively unimportant non-encrypted area. This strategy effectively avoids the huge amount of calculations brought by global encryption, enables reasonable allocation of computing resources, and significantly reduces unnecessary computing burdens.

[0043] 2. The present invention also takes into account the significant difference in mesh density between the encrypted area and the non-encrypted area, and direct connection may cause a sudden change in mesh size. A transition zone is set at the junction of the encrypted area and the non-encrypted area, and an innovative "two-in-one" mesh transition method is introduced to ensure that the mesh density can smoothly and continuously transition from the high-density area to the low-density area, while maintaining the uniformity and good geometric shape of the mesh in the transition area. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 paying creative work.

[0045] Figure 1 It is a flow chart of a multi-scale high-quality grid division method for a rotary shaft magnetic liquid sealing structure provided by the present invention;

[0046] Figure 2 It is a geometrical schematic diagram of the magnetic liquid sealing structure provided by the present invention;

[0047] Figure 3 It is a magnetic force line circuit diagram of the magnetic liquid sealing structure provided by the present invention;

[0048] Figure 4 It is a schematic diagram of the encrypted area and the non-encrypted area of ​​the magnetic liquid sealing structure provided by the present invention;

[0049] Figure 5 It is a geometrical schematic diagram of the A portion after the magnetic liquid seal is cut along the X axis according to the present invention;

[0050] Figure 6 This is a display diagram of the four-layer uniform grid generation and density-free gradient effect provided by the present invention;

[0051] Figure 7 This is a display diagram of the four-layer grid density gradient provided by the present invention, but lack of regularity;

[0052] Figure 8 It is a schematic diagram of the first arrangement form of each grid in the transition layer provided by the present invention;

[0053] Fig. 9 This is a schematic diagram of the second arrangement form of each grid in the transition layer provided by the present invention;

[0054] Fig.10 It is a close grid layout diagram of the first arrangement form in the transition layer provided by the present invention;

[0055] Fig.11 It is a final grid schematic diagram of the two-dimensional axisymmetric magnetic liquid sealing model provided by the present invention. DETAILED DESCRIPTION

[0056] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention; the terms "first", "second", and "third" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance. In addition, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0058] In view of the fact that the existing grid division methods cannot cope with the multi-scale challenges of tiny sealing gaps and huge overall structural dimensions, and cannot effectively improve the simulation efficiency while ensuring the calculation accuracy, the present invention provides a multi-scale high-quality grid division method for a rotating shaft magnetic liquid seal structure, specifically: first, after importing the constructed two-dimensional axisymmetric magnetic liquid seal model into the grid division tool, the two-dimensional axisymmetric magnetic liquid seal model is divided into two completely identical parts along the symmetry line; secondly, a part is randomly selected from the two divided parts as the model to be divided, and based on the unique properties of the magnetic liquid seal structure and the precise simulation requirements, a fine regional blocking strategy is used to clearly distinguish the parts with extremely high requirements for calculation accuracy. The encrypted area and the relatively minor non-encrypted area are separated. Considering the significant difference in mesh density between the encrypted area and the non-encrypted area, a transition area is set at the junction of the encrypted area and the non-encrypted area, and a "two-in-one" mesh transition method is innovatively proposed based on the characteristics of the transition area; again, after setting the parameters of each area to mesh each area, each area is subjected to a common node operation to obtain a mesh file of the model to be divided; then, the mesh file of the model to be divided is copied to the other side along the symmetry line, and the common node operation is performed again to form a mesh file of a two-dimensional axisymmetric magnetic liquid sealing model; finally, the accuracy of the mesh in the mesh file of the two-dimensional axisymmetric magnetic liquid sealing model is detected until the preset accuracy index is met, and the division is completed. Based on the unique properties of the magnetic liquid sealing structure and the precise simulation requirements, the present invention clearly distinguishes each area with different computing requirements through a sophisticated regional block strategy, effectively avoids the huge amount of calculation brought by global encryption, enables reasonable allocation of computing resources, and significantly reduces unnecessary computing burden. In addition, the present invention also takes into account the significant difference in mesh density between the encrypted area and the non-encrypted area, and direct connection may cause a sudden change in mesh size. A transition zone is set at the junction of the encrypted area and the non-encrypted area, and an innovative "two-in-one" mesh transition method is introduced based on the characteristics of the transition zone, ensuring that the mesh density can smoothly and continuously transition from the high-density area to the low-density area, while maintaining the uniformity and good geometric shape of the mesh in the transition area, which not only improves the overall quality of the mesh, but also significantly enhances the accuracy of the simulation results.

[0059] like Figure 1 As shown, the present invention provides a multi-scale high-quality grid division method for a rotary shaft magnetic liquid seal structure, and the specific steps are:

[0060] S1. Establish the theoretical parameters of the sealing geometry model and construct a two-dimensional axisymmetric magnetic liquid sealing model.

[0061] In the present application, the theoretical parameters of the sealing geometry model include the radius of the rotating shaft, the inner diameter, outer diameter and thickness of the pole shoe, the sealing gap s, the inner diameter, outer diameter and thickness of the permanent magnet, the number of pole teeth, the pole tooth height h, the pole tooth width d1, and the pole tooth slot width d2.

[0062] like Figure 2 As shown, the two-dimensional axisymmetric magnetic liquid sealing model in the present application includes a rotating shaft 1, an upper pole shoe 2, a permanent magnet 3, a lower pole shoe 4, an air domain 5 and a shell 6, wherein the rotating shaft 1 is arranged in the shell 6, and two pole shoes arranged up and down are sleeved on the rotating shaft 1, namely, an upper pole shoe 2 and a lower pole shoe 4, and a permanent magnet 3 is arranged between the upper pole shoe 2 and the lower pole shoe 4 to fit the two, and there are multiple magnetic circuits between the rotating shaft 1, the upper pole shoe 2, the permanent magnet 3 and the lower pole shoe 4, and there is a magnetic liquid in the gap formed by the pole shoe and the rotating shaft in the magnetic circuit.

[0063] In order to better illustrate the principle of the magnetic liquid sealing structure, the embodiment of the present application also provides a magnetic line of force loop diagram of the magnetic liquid sealing structure, such as Figure 3 The permanent magnet shown is located between the two pole shoes, and its magnetic lines of force start from one end of the permanent magnet and pass through the entire system along a specific path. When the magnetic lines of force reach the upper pole shoe, they are effectively guided and concentrated at the pole teeth by the magnetic focusing effect of the pole teeth on the pole shoe. Subsequently, these magnetic lines of force pass through the shaft, continue to travel to the lower pole shoe, and finally return to the other end of the permanent magnet, thus forming a complete closed loop of magnetic lines of force. In this process, the gap between the pole teeth and the shaft is filled with magnetic liquid. Due to the difference in magnetic force between the pole teeth and the outside of the pole teeth, this difference acts as a driving force to firmly adsorb the magnetic liquid around the pole teeth, forming a stable liquid barrier.

[0064] S2. Import the two-dimensional axisymmetric magnetic liquid seal model into a meshing tool for meshing to obtain a target mesh file.

[0065] In this application, the meshing tool used in step S2 is Hypermesh, and the specific meshing steps are as follows:

[0066] S21. After the two-dimensional axisymmetric magnetic liquid seal model is imported into the meshing tool, the symmetry line of the two-dimensional axisymmetric magnetic liquid seal model is found and the model is divided into two completely identical parts, namely, part A and part B, along the symmetry line.

[0067] S22. Randomly select one of parts A and B as the model to be divided and perform mesh division to obtain a first mesh file.

[0068] It should be noted that the model to be divided in the present application is randomly selected, and it is sufficient to select a part of the segmented part as the model to be divided, that is, part A can be selected as the model to be divided, or part B can be selected as the model to be divided.

[0069] like Figure 5As shown, in the embodiment of the present application, the two-dimensional axisymmetric magnetic liquid sealing model is divided into two parts A and B along the X-axis with the X-axis as the symmetry line, and part A is selected as the model to be divided for meshing.

[0070] In the present application, in the step S22, different division strategies are adopted for each area based on the regional blocking strategy according to the importance and computing requirements of each area. The specific strategies are: for the encrypted area, a fine grid division strategy is adopted, that is, the axial size of the grid in the encrypted area and the radial size of the grid in the encrypted area are much smaller than the axial size of the grid in the non-encrypted area and the radial size of the grid in the non-encrypted area; for the non-encrypted area, a sparse grid division strategy is adopted, that is, the axial size of the grid in the non-encrypted area and the radial size of the grid in the non-encrypted area are much larger than the axial size of the grid in the encrypted area and the radial size of the grid in the encrypted area; for the transition zone, a "two-in-one" grid transition method is adopted, that is, the grid size of the transition zone gradually transitions between the two.

[0071] In the embodiment of the present application, by adopting a fine grid division strategy for the encrypted area, the physical phenomena in the key area are effectively ensured to be accurately simulated; by adopting a sparse grid division strategy for the non-encrypted area, the purpose of reducing computing costs and shortening computing time is achieved; by adopting a "two-in-one" grid transition method for the transition zone, while ensuring the calculation accuracy and efficiency, the numerical problems caused by the sudden change of the grid size are avoided, and a smooth transition from a high-density grid to a low-density grid is achieved.

[0072] In this application, the step S22 is specifically divided into the following steps:

[0073] S221. Based on the physical characteristics, geometric shape and simulation requirements of the model to be divided, the model to be divided is divided into different areas, including an encrypted area, a transition area and a non-encrypted area.

[0074] Preferably, the densified area is the pole teeth on the pole shoe and the corresponding sealing gap area, the transition area is the area where the densified area transitions to the non-densified area, and the non-densified area is the remaining area outside the densified area and the transition area.

[0075] It should be noted that the density and quality of the mesh directly affect the accuracy and computational efficiency of the simulation results. Since the magnetic lines of force of the magnetic liquid seal are mainly concentrated in the gap formed by the inner end faces of the upper and lower pole shoes and the outer cylindrical surface of the rotating shaft, the magnetic flux density in the area near the sealing gap fluctuates greatly, while the change near the non-sealing gap is relatively gentle. In addition, the magnetic field at the sealing gap plays a decisive role in the sealing performance. Therefore, in order to capture the violent fluctuation characteristics of the magnetic flux density near the sealing gap, it is usually necessary to encrypt the mesh there, and a relatively sparse mesh in the non-sealing gap area can meet the requirements. In addition, considering that there is a significant difference in mesh density between the encrypted area and the non-encrypted area, direct connection may cause a sudden change in mesh size, which in turn causes numerical problems during the simulation process, such as numerical oscillation or divergence, so a transition zone is also set to smoothly connect the mesh density of the encrypted area and the non-encrypted area to ensure the continuity of mesh division, thereby avoiding the occurrence of such numerical problems.

[0076] S222. Set encryption area parameters, transition area parameters, and non-encryption area parameters.

[0077] Preferably, the encrypted area parameters include the encrypted area axial size, the encrypted area grid axial size, the encrypted area radial size and the encrypted area grid radial size, the transition area parameters include the number of transition layers, the non-encrypted area parameters include the non-encrypted area grid axial size and the non-encrypted area grid radial size, wherein the calculation formula for the number of transition layers is as follows:

[0078]

[0079] In the formula, m represents the number of transition layers, x 11 Indicates the axial size of the mesh in the encrypted area, x 12 Indicates the radial size of the mesh in the encrypted area, x 21 Indicates the axial size of the grid in the non-refined area, x 22 Represents the radial size of the grid in the non-refinement area.

[0080] For example, if the axial size of the mesh in the encrypted area is 1 and the radial size is 1, and the axial size of the mesh in the non-encrypted area is 4 and the radial size is 4, then the number of transition layers is 2.

[0081] like Figure 4 As shown, the shaded part in the figure is the encrypted area. It should be noted that the encrypted area only needs to include the pole teeth on the pole shoe and the corresponding sealing gap area. In actual use, the parameter size of the encrypted area and the parameter size of the non-encrypted area can be set according to needs.

[0082] Preferably, the number of transition layers and the number of mesh axes in the dense area are 11 Need to meet where a 11It is obtained by combining the axial size of the densified area and the axial size of the densified area grid; at the same time, the number of transition layers and the radial number of densified area grids a 12 Also need to satisfy where a 12 It is obtained by combining the radial size of the encrypted area with the radial size adjustment of the encrypted area grid.

[0083] S223. Divide the encryption area into grids based on the set encryption area parameters.

[0084] S224. Based on the set encrypted area parameters, transition area parameters and non-encrypted area parameters, the transition area is meshed using a "two-in-one" mesh transition method.

[0085] like Figure 6 As shown in the figure, firstly, 4 layers of grids are set and the number of grids in each layer is set to 8, and then Hypermesh is used to directly generate the grid. It can be seen from the figure that the grid generated by the above settings is regular but the transition from dense to sparse grid cannot be achieved.

[0086] like Figure 7 As shown, 4 layers of grids are also set, and the number of lower grids is set to 8 and the number of upper grids is set to 2. Then Hypermesh is used to directly generate the grid. It can be seen from the figure that the grid generated by the above settings can achieve a transition from dense to sparse but is not regular.

[0087] Therefore, in this application, a "two-in-one" grid transition method is used to divide the transition zone into grids, wherein the "two-in-one" grid transition method is specifically as follows: m transition layers are constructed between the encrypted area and the non-encrypted area, and the grid size is enlarged layer by layer, that is, the axial / radial size of the grid unit of each transition layer is twice that of the previous layer, thereby realizing a gradual transition from a high-density grid to a low-density grid.

[0088] In the embodiment of the present application, the specific steps of step S224 are:

[0089] a. Double the axial size and radial size of the mesh in the densified area to serve as the axial size and radial size of the mesh in the first transition layer;

[0090] b. Based on the axial size and radial size of the first transition layer grid determined in step a, dividing the first transition layer grid outside the densification area;

[0091] c. Double the axial size and radial size of the first transition layer grid to serve as the axial size and radial size of the second transition layer grid;

[0092] d. based on the axial size and radial size of the second transition layer grid determined in step c, dividing the second transition layer grid outside the first transition layer;

[0093] e. Repeat steps c and d, each time doubling the axial and radial dimensions of the current transition layer grid and expanding a new transition layer grid outward until the mth transition layer grid is divided and stops;

[0094] f. Perform a common node operation on the grids of the m transition layers, and the grid division of the transition area is completed, forming a smooth transition area with a gradually decreasing grid density from the encrypted area to the peripheral area.

[0095] In the embodiment of the present application, the grid size of the transition zone gradually increases from the encrypted zone to the non-encrypted zone, and the number of grids in the transition zone gradually decreases from the encrypted zone to the non-encrypted zone.

[0096] Assuming that the axial grid size of the encrypted area is 1 and the radial grid size is 1, and the axial grid size of the non-encrypted area is 4 and the radial grid size is 4, if the axial / radial grid size of the encrypted area is to be transitioned to the axial / radial grid size of the non-encrypted area, two transition layers need to be constructed in the transition area, specifically: in the first transition layer, the axial / radial size of the grid is twice the axial / radial grid size of the encrypted area, so the axial size and radial size of the grid in the first transition layer are both 2; in the second transition layer, the axial / radial size of the grid is twice the axial / radial grid size of the grid in the first transition layer, so the axial size and radial size of the grid in the second transition layer are both 4. At this time, the transition of the transition zone is completed, satisfying the smooth transition from the axial / radial grid size of the encrypted area to the axial / radial grid size of the non-encrypted area. This method not only ensures the continuity and consistency of the grid, but also avoids the calculation accuracy problem that may be caused by directly reducing the number of grids.

[0097] Preferably, each grid in the transition layer is composed of a plurality of quadrilateral small grids having at least one right angle, and the plurality of small grids constituting each grid may include a variety of shapes.

[0098] In the present application, each grid in the transition layer is composed of two right-angled trapezoidal small grids and one regular quadrilateral small grid, wherein the side lengths of the regular quadrilateral on the upper base of the right-angled trapezoid are equal to the size of the grid of the previous layer, and the lower base of the right-angled trapezoid is equal to the size of the grid of the current layer. These three small grids include two arrangement modes in the grid: ① The left diagonal of the regular quadrilateral small grid coincides with the lower left diagonal of the grid, and two right-angled trapezoidal small grids are arranged on the lower left diagonal of the grid, and the hypotenuses of the two right-angled trapezoidal small grids coincide with the upward extension line of the left diagonal of the regular quadrilateral; ② The right diagonal of the regular quadrilateral small grid coincides with the lower right diagonal of the grid, and two right-angled trapezoidal small grids are arranged on the lower right diagonal of the grid, and the hypotenuses of the two right-angled trapezoidal small grids coincide with the upward extension line of the right diagonal of the regular quadrilateral.

[0099] like Figure 8-9 As shown, Figure 8 This is a schematic diagram of the first arrangement form of each grid in the transition layer. Fig. 9 Schematic diagram of the second arrangement form of each grid in the transition layer.

[0100] Preferably, in each transition layer, the grids appear alternately in two different arrangements; at the same time, in each transition layer, at both end boundaries in contact with the non-encrypted area, the lower base of the right-angled trapezoidal small grid is directly connected to the grid boundary of the non-encrypted area.

[0101] For example, in each transition layer of the embodiment of the present application, at the two end boundaries in contact with the non-encrypted area, the starting grid adopts the first arrangement form, and the ending grid adopts the second arrangement form.

[0102] It should be noted that two grids with the same arrangement cannot appear at the same time in each transition layer. Fig.10 As shown, when the grids with the same arrangement form are closely laid out in the first type, due to the existence of the grid point at the upper right corner of the regular quadrilateral small grid in the leftmost grid, the lower bottom line segment of the right-angled trapezoidal small grid on the left in the rightmost grid will be made - Fig.10 The bold line in the figure is identified as connecting two independent grid points, which causes the line segment to be divided into two parts. This changes the structure of the right-angled trapezoidal small grid, that is, from a quadrilateral grid to a pentagonal grid, causing the simulation results to deviate from the actual situation, thereby reducing the accuracy of the simulation.

[0103] Preferably, the ratio of the number of grids in the current transition layer to the number of grids in the transition layer immediately below it is 2:1.

[0104] S225. Based on the set non-encrypted area parameters, the non-encrypted area is gridded.

[0105] In the present application, the encrypted area, transition area and non-encrypted area are all quadrilateral grids, wherein the encrypted area and non-encrypted area are regular quadrilateral grids.

[0106] Preferably, due to the progressive influence of multiple transition layers in the transition zone, the grid shape in the non-encrypted area that coincides with the axial / radial extension of these transition layers is rectangular.

[0107] S226, performing a common node operation on the meshes of the encrypted area, the transition area, and the non-encrypted area to complete the mesh division of the model to be divided, and obtaining a first mesh file.

[0108] S23, symmetrically copying the first grid file to the other side along the symmetry line to obtain a second grid file.

[0109] In the embodiment of the present application, the symmetrical part of the model to be divided is quickly generated through the copy operation, which not only reduces the workload of repeated modeling, but also saves a lot of computing resources.

[0110] S24, performing a common node operation on the first grid file and the second grid file to complete the grid division of the two-dimensional axisymmetric magnetic liquid seal model and obtain a target grid file.

[0111] In the embodiment of the present application, the target grid file is as follows: Fig.11 shown.

[0112] S3. Check the accuracy of each grid in the target grid file. If the preset accuracy index is met, the division is completed and the target grid file is output; otherwise, modify the non-compliant area in the grid until the preset accuracy index is met and stop.

[0113] In the embodiment of the present application, the preset accuracy index is that the Jacobian value of each grid in the target grid file is ≥0.6.

[0114] The Jacobian value is an important indicator for evaluating the quality of meshes in fields such as finite element analysis and computational fluid dynamics. It reflects the degree of deformation of mesh units from theoretical shapes to actual shapes, such as squares, regular triangles, etc., which has an important impact on the accuracy and stability of simulation results. When the Jacobian value is ≥0.6, it can be considered that the mesh quality is relatively good and can better reflect the actual situation of the model, thereby obtaining more accurate simulation results. On the contrary, if the Jacobian value is <0, it means that flip units have appeared in the model, which will lead to inaccuracy and instability in the simulation results. When the Jacobian value is <0.6, although the model has no flip units, the mesh quality is still low, which may lead to large errors in the simulation results. Therefore, when performing finite element analysis, the minimum standard of the Jacobian value is usually set to 0.6 or higher to ensure that the mesh quality meets the simulation requirements. Therefore, in the embodiment of the present application, the preset accuracy index is set to "Jacobian value of each mesh in the target mesh file ≥0.6", which can guarantee the accuracy and reliability of the simulation results to a certain extent.

[0115] It should be noted that different physical environments and solvers may have different requirements for mesh quality. In specific applications, it is also necessary to select appropriate meshing methods and standards based on actual conditions.

[0116] Preferably, when the detection in step S3 is unqualified, the specific modification step is: re-gridding the local area that does not meet the accuracy requirement.

[0117] In view of the shortcomings of the existing grid division methods for magnetic liquid sealing structures, the present invention accurately defines the encrypted areas requiring high-precision calculations and the relatively minor non-encrypted areas based on the regional blocking strategy according to the characteristics of the magnetic liquid sealing structure and the simulation requirements, effectively avoiding the unnecessary calculation burden brought by global encryption; at the same time, at the junction of the encrypted area and the non-encrypted area, an innovative "two-in-one" grid transition method is proposed, which ensures the smooth transition of the grid from high density to low density while maintaining the uniformity and shape regularity of the grid in the transition area. This technology not only improves the overall quality of the grid, but also significantly enhances the accuracy of the simulation results.

[0118] Furthermore, the present invention combines the regional block strategy with the "two-in-one" grid transition method to provide dual guarantees of efficiency and accuracy for existing grid division technology, and successfully solves two major problems in traditional grid division methods: one is the excessive consumption of computing resources caused by comprehensive encryption; the other is that simple sparse grids are difficult to ensure the simulation accuracy of key areas, and the automatic grid division algorithm often has poor grid quality problems in complex structures. In addition, the grid division method provided by the present invention has a high degree of flexibility and universality, can be applied to magnetic liquid sealing structures of different sizes and complexities, and has far-reaching guiding significance and broad application prospects in the design optimization, performance prediction and fault analysis of magnetic liquid seals.

[0119] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A multi-scale high-quality meshing method for a rotating shaft magnetic liquid seal structure. It is characterized in that The specific steps are: S1. Establish theoretical parameters of sealing geometry model and construct two-dimensional axisymmetric magnetic liquid sealing model; S2. Import the two-dimensional axisymmetric magnetic liquid seal model into a meshing tool for meshing to obtain a target mesh file. The meshing tool is Hypermesh. The specific meshing steps are as follows: S21, after importing the two-dimensional axisymmetric magnetic liquid seal model into the mesh generation tool, finding the symmetry line of the two-dimensional axisymmetric magnetic liquid seal model and dividing it into two completely identical parts, namely, part A and part B, along the symmetry line; S22, randomly select one of parts A and B as a model to be divided into meshes, and obtain a first mesh file; S23, symmetrically copying the first grid file to the other side along the symmetry line to obtain a second grid file; S24, performing a common node operation on the first grid file and the second grid file to complete the grid division of the two-dimensional axisymmetric magnetic liquid seal model and obtain a target grid file; S3. Check the accuracy of each grid in the target grid file. If the preset accuracy index is met, the division is completed and the target grid file is output; otherwise, modify the non-compliant area in the grid until the preset accuracy index is met and stop.

2. A multi-scale high-quality meshing method for a rotary shaft magnetic liquid seal structure according to claim 1, It is characterized in that The theoretical parameters of the sealing geometric model include the radius of the rotating shaft, the inner diameter, outer diameter and thickness of the pole shoe, the sealing gap s, the inner diameter, outer diameter and thickness of the permanent magnet, the number of pole teeth, the pole tooth height h, and the pole tooth width d. 1 , and the pole slot width d 2 ; The two-dimensional axisymmetric magnetic liquid sealing model includes a rotating shaft, an upper pole shoe, a permanent magnet, a lower pole shoe, an air domain and a shell, wherein the rotating shaft is arranged in the shell, and two pole shoes arranged up and down are sleeved on the rotating shaft, namely an upper pole shoe and a lower pole shoe, and a permanent magnet is arranged between the upper pole shoe and the lower pole shoe to fit the two, and multiple magnetic circuits are arranged between the rotating shaft, the upper pole shoe, the permanent magnet and the lower pole shoe, and the gap formed by the pole shoe and the rotating shaft in the magnetic circuit has magnetic liquid.

3. A multi-scale high-quality meshing method for a rotary shaft magnetic liquid seal structure according to claim 2, It is characterized in that In the step S22, different division strategies are adopted for each area based on the regional block strategy according to the importance and calculation requirements of each area, wherein the specific strategies are: for the encrypted area, a fine grid division strategy is adopted, that is, the axial size of the grid in the encrypted area and the radial size of the grid in the encrypted area are much smaller than the axial size of the grid in the non-encrypted area and the radial size of the grid in the non-encrypted area; for the non-encrypted area, a sparse grid division strategy is adopted, that is, the axial size of the grid in the non-encrypted area and the radial size of the grid in the non-encrypted area are much larger than the axial size of the grid in the encrypted area and the radial size of the grid in the encrypted area; for the transition area, a "two-in-one" grid transition method is adopted, that is, the grid size of the transition area gradually transitions between the two; In addition, the step S22 is specifically divided into the following steps: S221, based on the physical characteristics, geometric shape and simulation requirements of the model to be divided, dividing the model to be divided into different areas, including an encrypted area, a transition area and a non-encrypted area; S222, setting encryption area parameters, transition area parameters and non-encryption area parameters; S223, based on the set encryption area parameters, the encryption area is grid-divided; S224. Based on the set encrypted area parameters, transition area parameters and non-encrypted area parameters, the transition area is meshed by using a "two-in-one" mesh transition method, wherein the "two-in-one" mesh transition method is specifically as follows: m transition layers are constructed between the encrypted area and the non-encrypted area, and the mesh size is enlarged layer by layer, that is, the axial / radial size of the mesh unit of each transition layer is twice that of the previous layer, so as to realize a gradual transition from a high-density mesh to a low-density mesh; S225, based on the set non-encrypted area parameters, the non-encrypted area is grid-divided; S226, performing a common node operation on the meshes of the encrypted area, the transition area, and the non-encrypted area to complete the mesh division of the model to be divided, and obtaining a first mesh file.

4. A multi-scale high-quality meshing method for a rotary shaft magnetic liquid seal structure according to claim 3, It is characterized in that The densified area is the pole teeth on the pole shoe and the corresponding sealing gap area, the transition area is the area where the densified area transitions to the non-densified area, and the non-densified area is the remaining area outside the densified area and the transition area; In addition, the encrypted area parameters include the encrypted area axial size, the encrypted area grid axial size, the encrypted area radial size and the encrypted area grid radial size, the transition area parameters include the number of transition layers, and the non-encrypted area parameters include the non-encrypted area grid axial size and the non-encrypted area grid radial size, wherein the calculation formula for the number of transition layers is as follows: In the formula, m represents the number of transition layers, x 11 Indicates the axial size of the mesh in the encrypted area, x 12 Indicates the radial size of the mesh in the encrypted area, x 21 Indicates the axial size of the grid in the non-refined area, x 22 Represents the radial size of the grid in the non-refinement area.

5. A multi-scale high-quality meshing method for a rotary shaft magnetic liquid seal structure according to claim 4, It is characterized in that The number of transition layers and mesh axes in the dense area a 11 Need to meet where a 11 It is obtained by combining the axial size of the densified area and the axial size of the densified area grid; at the same time, the number of transition layers and the radial number of densified area grids a 12 Also need to satisfy where a 12 It is obtained by combining the radial size of the encrypted area with the radial size adjustment of the encrypted area grid.

6. A multi-scale high-quality meshing method for a rotary shaft magnetic liquid seal structure according to claim 5, It is characterized in that The specific steps of step S224 are: a. Double the axial size and radial size of the mesh in the densified area to serve as the axial size and radial size of the mesh in the first transition layer; b. Based on the axial size and radial size of the first transition layer grid determined in step a, dividing the first transition layer grid outside the densification area; c. Double the axial size and radial size of the first transition layer grid to serve as the axial size and radial size of the second transition layer grid; d. based on the axial size and radial size of the second transition layer grid determined in step c, dividing the second transition layer grid outside the first transition layer; e. Repeat steps c and d, each time doubling the axial and radial dimensions of the current transition layer grid and expanding a new transition layer grid outward until the mth transition layer grid is divided and stops; f. Perform a common node operation on the grids of the m transition layers, and the grid division of the transition area is completed, forming a smooth transition area with a gradually decreasing grid density from the encrypted area to the peripheral area.

7. A multi-scale high-quality meshing method for a rotary shaft magnetic liquid seal structure according to claim 6, It is characterized in that Each grid in the transition layer is composed of a plurality of quadrilateral small grids having at least one right angle, and the plurality of small grids constituting each grid may include a variety of shapes; In addition, the ratio of the number of grids in the current transition layer to the number of grids in the transition layer immediately below it is 2:

1.

8. A multi-scale high-quality meshing method for a rotary shaft magnetic liquid seal structure according to claim 7, It is characterized in that Each grid in the transition layer is composed of two right-angled trapezoidal small grids and one regular quadrilateral small grid, wherein the side lengths of the regular quadrilaterals on the upper base of the right-angled trapezoids are equal to the size of the grid of the previous layer, and the lower base of the right-angled trapezoids is equal to the size of the grid of the current layer, and the three small grids are arranged in two ways in the grid: ① the left diagonal of the regular quadrilateral small grid coincides with the lower left diagonal of the grid, and two right-angled trapezoidal small grids are arranged on the lower left diagonal of the grid, and the hypotenuses of the two right-angled trapezoidal small grids coincide with the upward extension line of the left diagonal of the regular quadrilateral; ② the right diagonal of the regular quadrilateral small grid coincides with the lower right diagonal of the grid, and two right-angled trapezoidal small grids are arranged on the lower right diagonal of the grid, and the hypotenuses of the two right-angled trapezoidal small grids coincide with the upward extension line of the right diagonal of the regular quadrilateral; In addition, in each transition layer, the grids appear alternately in two different arrangements; at the same time, in each transition layer, at both end boundaries in contact with the non-reinforced area, the lower base of the right-angled trapezoidal small grid is directly connected to the grid boundary of the non-reinforced area.

9. A multi-scale high-quality meshing method for a rotary shaft magnetic liquid seal structure according to claim 8, It is characterized in that The encrypted zone, transition zone and non-encrypted zone are all quadrilateral grids, among which the encrypted zone and the non-encrypted zone are regular quadrilateral grids; at the same time, due to the progressive influence of multiple transition layers in the transition zone, the grid shape in the non-encrypted zone that overlaps with the axial / radial extension of these transition layers is rectangular.

10. A multi-scale high-quality meshing method for a rotary shaft magnetic liquid seal structure according to claim 9, It is characterized in that The preset accuracy index is that the Jacobian value of each grid in the target grid file is ≥ 0.6.

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