Rotating machine grid generation method based on feature region topological structure

Abstract

The invention discloses a rotating machine grid generation method based on a feature region topological structure. The rotating machine grid generation method comprises the following steps of dynamically constructing a rotating machine M-THTA plane topology; calculating and distributing global grid key node information; generating a characteristic region grid; and the 3D mesh is generated by stretching and stacking the M-THTA surface in the spanwise direction. According to the method, the technical problems of complex geometric pretreatment and automatic generation of a high-quality rotating mechanical structure grid in the field of rotating machinery at present are solved in a targeted manner, so that the application of a domestic numerical simulation technology in the whole machine simulation of an aero-engine is accelerated.

Description

Technical Field

[0001] The invention belongs to the field of simulation technology, and in particular relates to a rotating machinery grid generation method based on characteristic region topology structure in the field of industrial simulation. Background Art

[0002] With the development of modern aviation industry and the increasingly complex needs of national defense industry, CFD simulation has played an increasingly important role in the industrial design of aircraft engines, and is also a key technical support for technological advancement and digital research and development in the field of national defense aviation. Facing the industrial simulation of complex rotating parts such as compressors, fans, and turbines of aircraft engines, high-efficiency and high-quality grid generation technology is the technical core of simulation computing.

[0003] Rotating machinery simulation usually needs to face complex and shape-changing geometric models. At the same time, the traditional hand-drawn meshes and structural meshes generated by recording manual scripts are of low quality and cannot meet the increasingly complex geometric model feature expression. More importantly, its mesh drawing and generation efficiency is low, and it cannot cope with today's new industrial design model that pursues high efficiency. Therefore, in order to shorten the mesh generation cycle and reduce the cost of manually drawing meshes, this application establishes a method for dynamically constructing the M-THETA parameter plane topology of rotating machinery and stacking to generate meshes. A set of initial templates plus feature areas are used for automatic mesh generation. When facing other complex geometric models, the template can be dynamically transformed to quickly match the geometric model to build the topology, while ensuring the mesh quality of the topological parameter plane and its three-dimensional mesh, providing a low-cost and high-efficiency mesh automatic generation technology path for the field of automatic mesh generation for rotating machinery simulation, and further expanding the application prospects of rotating machinery mesh automatic generation topology technology. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for generating a rotating machinery mesh based on a characteristic region topological structure, which solves the problems existing in the prior art and expands the prospect of automatic topological generation of rotating machinery meshes.

[0005] In order to solve the above technical problems, the present invention is implemented in the following ways:

[0006] A method for generating a rotating machinery mesh based on a characteristic region topological structure comprises the following steps:

[0007] S1. Import geomTurbo geometry file;

[0008] S2, topological construction based on the O4H template of the characteristic region;

[0009] S3, generate 3D mesh by stretching and stacking the B2B surface in the span direction;

[0010] S4. Complete the generation of rotating machinery surface mesh.

[0011] Furthermore, the specific steps of step S2 are as follows:

[0012] The topological construction based on the feature area O4H template refers to the generation of the O-grid general template of the main part of the blade topology and the feature template of the flow channel area adaptively generated according to the topological type. The M-THETA feature topology of the current activation layer position is adaptively formed by combining the main blade O-grid area and the flow channel feature area. The topological construction based on the feature area O4H template includes the calculation of the key node information and the number of distribution points of the O4H main part grid and the grid generated by the feature area grid based on the extension of the main part of the blade O-grid area;

[0013] S21, O4H The calculation of key node information and distribution points of the main part of the grid is carried out by using the O grid topology characteristics of the main part of the blade topology based on the adaptive blade topology. When the main part of the grid topology is generated, the relative position of the key nodes is calculated in advance. According to the position information of the key nodes of the topological grid surface, the grid entity line is calculated to complete the construction of the blade area O grid topology.

[0014] S22, feature area mesh is generated by extending the O mesh of the main part of the blade topology. Its structure is mainly composed of two parts: the constant part and the OHGap gap layer, which together constitute the characteristic area of ​​the flow channel of the B2B surface (M-THETA parameter plane), accurately expressing the M-THETA surface topology type and the flow channel change law in the span direction.

[0015] Furthermore, the specific steps of step S21 are as follows:

[0016] S211, grid front and rear edge point position calculation

[0017] In order to ensure that the overall inlet and outlet grids and the outer O grid layout of the M-THETA plane are more standardized in physical space, it is necessary to construct appropriate leading and trailing edge point positions and calculate the blade width at the leading and trailing edge points of the blade; the blade width at the leading and trailing edge points can be regarded as the inscribed circle diameter of the blade at the leading and trailing edge points, and multiple groups of sampling points near the leading and trailing edge points are taken to calculate the center of the circle, and the minimum circle is used as the final inscribed circle. At the same time, the maximum blade width is calculated as the maximum limit of the inscribed circle diameter, and then the leading and trailing edge point positions of the grid are obtained according to the ratio of the relative control distance to the length of the pressure surface and suction surface of the blade;

[0018] S212, calculation of blade position in flow channel

[0019] There are four positions of the blade in the flow channel, which specifically include the blade to the upper cycle area AREA2, the blade to the lower cycle area AREA3, the blade leading edge to the inlet area AREA1, and the blade trailing edge to the outlet area AREA4:

[0020] The distance from the blade to the upper / lower cycle is obtained by obtaining the two closest discrete points between the upper / lower cycle boundary geometric discrete points and the blade suction surface / pressure surface discrete points, and then calculating the distance by using the coordinate discrete points to obtain the blade upper / lower cycle distance. At the same time, the point closest to the endpoint of the upper / lower cycle boundary from the blade inlet position is determined;

[0021] The distance from the blade to the inlet is obtained by obtaining the midpoint of the inlet, calculating the distance from the midpoint to the end point of the leading edge of the blade, and obtaining the horizontal distance from the inlet to the leading edge of the blade based on the length of the midpoint and the end point of the leading edge, and obtaining the node position and node distribution size on the blade;

[0022] S213, periodic boundary node position calculation

[0023] When generating the grid, the periodic boundary node positions are calculated in advance, and the periodic boundary grid line entities are subsequently calculated using the positions. In the main part of the O4H grid, there are 4 periodic boundary point positions in each periodic boundary that need to be calculated. When matching the periodicity, the positions may be related to each other. The 4 periodic boundary point positions include position 0 as the inlet end face, position 1 as the boundary surface corresponding to the leading edge position of the blade to the upper and lower periodic boundaries, position 2 as the boundary surface corresponding to the trailing edge position of the blade to the upper and lower periodic boundaries, and position 3 as the outlet end face;

[0024] 1) For positions 0 and 3, consider whether there is a constant part:

[0025] If there is no constant at the entrance, position 0 is 0.0. If there is a constant at the entrance, position 0 is the intersection of the constant line at the rear of the entrance and the periodic boundary line.

[0026] If there is no constant at the exit, position 3 is 1.0. If there is a constant at the exit, position 1 is the intersection of the constant line at the front of the exit and the periodic boundary line.

[0027] 2) For position 1 and position 2, directly use the method of calculating the closest point from the midline endpoint to the period boundary, and take the closest point as the position of position 1 and position 2. If the obtained position 1 and position 2 intersect with position 0 and position 3 or are too close, then position 1 and position 2 need to be optimized as follows:

[0028] 1. Cross judgment: judge whether position 2 is greater than position 3;

[0029] 2. Distance judgment: Calculate the horizontal distance from the trailing edge to position 3, and determine whether the ratio of the distance from position 2 to position 3 to the horizontal distance is less than a given threshold;

[0030] 3. When any of the above two conditions are met, for position 2, the position of the corresponding upper cycle boundary line is obtained based on the trailing edge point and the midpoint of the M coordinate of position 3 as the optimized new position;

[0031] S214, calculation of intermediate node positions at the entrance and exit boundaries

[0032] When generating the grid, the positions of the middle nodes of the inlet and outlet boundaries are calculated in advance, and the inlet and outlet boundary grid line entities are calculated using the positions. The two positions of the middle nodes of the inlet and outlet boundaries are determined as follows:

[0033] 1) The overall entrance and exit are evenly distributed: the position is calculated based on the ratio of the number of points on the three lines of the entrance and exit boundaries;

[0034] 2) The overall inlet and outlet are dense in the middle and gradually sparse from the middle to the two ends. The distance between the two nodes at the front and rear edges after advancement is used as the thickness of the top layer of the boundary layer grid. This thickness is used as the width of the position of the division point where the inlet and outlet are divided into three sections. The width of the remaining two ends is allocated according to the number of points.

[0035] S215, O4H main part point calculation

[0036] The edges of the O4H initial type topology template are divided into 7 groups. The number of points and distribution of the edges in each group are the same. The number of points is determined by two methods: a given number of points and a given minimum number of points and then calculated according to the actual model. The given number of points method is mainly used for HorizonMiddle, VerticalMiddle, and OutO, which have relatively fixed geometric shapes in the edges of the O4H initial type topology template. The given minimum number of points and then calculated according to the actual model method is mainly used for HorizonFront and HorizonBack, which have drastic changes in the edges of the O4H initial type topology template and need to calculate the number of points based on the length of the flow channel in the flow direction, or VerticalUp and VerticalDown, whose corresponding geometric scales will be affected by the periodic number of blades.

[0037] A reference length is set according to the geometric model. If the calculated geometric length of a part is too long relative to the reference length, the number of points is increased; if it is too short, the number of points is reduced. At the same time, a logarithmic function is used to calculate the number of topological points.

[0038] S216, Topological construction method

[0039] Topological construction refers to calculating line entities. Line entities need to express the shape of ideal grid lines. Lines mapped to geometric edges are mapped by sampling a small number of point coordinates on the geometric edges as grid line entities. When generating a grid, the projection function is used to project them to the geometric edges. The shapes of the grid lines inside the grid are calculated through the boundary lines to generate the initial grid. The specific steps are as follows:

[0040] 1) Initial topology template generation, mainly consists of four steps:

[0041] 1. Create all points in the initial topological state;

[0042] 2. Create all lines in the initial topological state;

[0043] 3. Modify to the corresponding grid line according to the specific topology type;

[0044] 4. According to the specific topology type, create all faces and do not generate internal points on the faces;

[0045] 2) Boundary layer mesh generation requires calculation of the distribution of the four lines on the wall and the outward height advancement of the points on the blade. Boundary layer mesh generation usually adopts the advancement method guided by the normal vector, and the issues that need to be considered in the advancement method include the intersection processing of the mesh and the orthogonality of the mesh. Boundary layer mesh generation selects a relatively simple method of advancing the frame line, and the process is as follows:

[0046] 1. Calculate the total propulsion height H;

[0047] 2. Push all the nodes on the four lines of the wall to a height of H along their normals to obtain a series of lines consisting of new points;

[0048] 3. There may be intersections in the new lines, so cross processing is performed;

[0049] 4. Assign the distribution of the four solid lines of the wall to the advanced lines respectively;

[0050] 5. Calculate and set the support line distribution;

[0051] 6. Generate internal points of each grid;

[0052] The core of this method is intersection processing. There are two possible intersections: one is the self-intersection within a line; the other is the intersection between lines. The situation of self-intersection within a line is as follows: when there is a concave point on the line to be advanced (under the state of turbine blades), the advancement result may produce self-intersection; the method of removing self-intersection of the present invention is: starting from the starting point of the line after advancement, calculate the angle at each point. When the angle at a certain point is greater than 90°, remove this point, and repeat until no point is removed.

[0053] 3) Flow channel mesh generation

[0054] 1. Inlet and outlet grid line entities

[0055] According to the positions of the intermediate nodes of the inlet and outlet, the corresponding discrete points are calculated and taken out at the inlet and outlet as the inlet and outlet grid line entities;

[0056] 2. Periodic Boundary Grid Line Entity

[0057] According to the position of the upper and lower periodic boundary lines, the four intersection points intersecting with the inlet and outlet are calculated and determined. The four intersection points are the left and right maximum range areas of the upper and lower periodic boundary discrete points. The discrete points within this range are the discrete point areas of the periodic boundary grid line entity.

[0058] 3. Entrance and exit horizontal middle grid line entity

[0059] By calculating the upper and lower periodic entity lines and two endpoints, given the number of sampling points, a series of vectors within the periodic boundary of the two-point coordinates are calculated, and the vectors are translated to the corresponding periodic boundary node positions. The end point of the vector is the sampling point required by the grid line entity;

[0060] 4. Internal vertical grid line entities

[0061] For the rotating machinery geometric model with too large blade inclination angle, the vertical grid lines leading to the periodic boundary of the generated M-THETA topology will point to the boundary layer area, and then from the boundary layer area to the periodic boundary. The physical distribution of the vertical grid lines is consistent with the horizontal middle grid line distribution at the inlet and outlet.

[0062] Furthermore, the specific steps of step S22 are as follows:

[0063] S221, constant part mesh generation

[0064] One edge of a mesh face in the constant part directly uses the edge of the original O4H main part, and the other three edges are generated according to the O4H exit and the actual exit position; the mesh distribution of the constant part is: the distribution of the rightmost exit edge is the same as the distribution at the exit of the O4H main part, and the distribution of the upper and lower grid lines is calculated with a uniform transition to the horizontal grid size at the exit of the O4H main part;

[0065] S222, OHGap mesh generation

[0066] The OHGap grid is divided into an O grid close to the blade wall and an innermost H grid. The O grid is directly generated using the boundary layer grid generation method in the topological construction method. The middle H grid needs to distinguish whether the number of nodes on the pressure surface and suction surface of the blade is the same. If they are the same, a grid surface is generated based on the top line of the O grid after advancement. If they are not the same, a Connector needs to be generated at the grid line entity above the O grid. The number of points of this Connector is consistent with the number of points of the grid line below the O grid, so that a grid surface can be formed.

[0067] When generating the O grid close to the blade wall and the innermost H grid, if the number of nodes on the pressure surface and the suction surface is the same, the node matching is completed, and the OHGap grid is directly promoted to generate the feature area. The corresponding 3D grid is periodic, and the pre-grid boundary connection is better after full-cycle replication, and the grid quality is higher; otherwise, the periodic nodes of the 3D grid do not match, and the periodic replication of the entire flow channel will affect the grid quality and grid solution.

[0068] Furthermore, the specific method of step S3 is as follows:

[0069] When constructing a 3D mesh by stretching and stacking the M-THETA surfaces in the span direction, a three-dimensional template needs to be stretched through the two-dimensional M-THETA surface at the hub. The stretching height of the M-THETA surface along the x direction is consistent with the meridian width, and the 3D mesh height is controlled by the meridian width. Then, according to the specific position of the M-THETA corresponding to the activation layer in the meridian plane (the meridian range ratio is [0.0,1.0]) (for example, the middle position of the M-THETA in the meridian plane is the 0.5 position of the activation layer), the above-constructed B2B (M-THETA) surfaces are placed layer by layer in this 3D template, and then the M-THETA surface mesh data stacked in the template is mapped to the stretched 3D mesh template through the surface to form the final 3D stacked mesh.

[0070] Compared with the prior art, the present invention has the following beneficial effects:

[0071] 1) Based on the M-THETA mesh topology dynamic construction technology implemented by topology templates, the M-THETA surface topology is dynamically generated by initializing the template for complex geometric models of rotating machinery (such as fans, turbines, splitters, cooling holes, etc.) without the need for additional manual operations. That is, only one initial template is needed and then dynamic template transformation is performed to obtain other complex types of topologies such as fans, turbines, splitters, cooling holes, etc. This method greatly improves the versatility of the original mesh template and the efficiency of automatic mesh generation, reducing R&D costs and user usage costs;

[0072] 2) The 3D mesh automatic generation technology based on spanwise stretching and stacking technology can well restore the global 3D mesh from the local parameter plane. The stacked 3D mesh well expresses the local details of the M-THETA surface topological structure, and technically improves the difficulty of the parameter plane mesh to accurately express the global mesh of the rotating machinery. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 It is a schematic diagram of the process steps of the present invention;

[0074] Figure 2 It is a schematic diagram of the position information of the blade in the flow channel of the present invention;

[0075] Figure 3 This is a schematic diagram of the position information of the periodic boundary points of the M-THETA plane of the present invention;

[0076] Figure 4 A schematic diagram of calculating the location information of entry and exit nodes in the present invention;

[0077] Figure 5 This is a schematic diagram of the relationship between the O4H and LH topological edges of the present invention;

[0078] Figure 6 A schematic diagram is generated for the internal feature grid OHGap portion of the present invention. DETAILED DESCRIPTION

[0079] The specific implementation of the present invention is further described in detail below with reference to the accompanying drawings and specific examples.

[0080] like Figure 1 As shown, a method for generating a rotating machinery mesh based on a characteristic region topological structure comprises the following steps:

[0081] S1. Import geomTurbo geometry file;

[0082] S2, based on the characteristic region O4H template topology construction, the specific steps are as follows:

[0083] The topological construction based on the feature area O4H template refers to the generation of the O-grid general template of the main part of the blade topology and the feature template of the flow channel area adaptively generated according to the topological type. The M-THETA feature topology of the current activation layer position is adaptively formed by combining the main blade O-grid area and the flow channel feature area. The topological construction based on the feature area O4H template includes the calculation of the key node information and the number of distribution points of the O4H main part grid and the grid generated by the feature area grid based on the extension of the main part of the blade O-grid area;

[0084] The meridian flow channel of rotating machinery is a group of M-THETA topologies distributed in the meridian area. The 3D grid range area needs to be stacked longitudinally along the x direction to form a 3D grid. The activation layer represents the specific position of the M-THETA topology along the x direction (its coordinates are in the z, y plane (or m_theta parameter plane) in the meridian plane when stacking (the meridian range ratio is [0.0,1.0]), and its range is the upper and lower width of the meridian plane (the corresponding position ratio in the meridian plane is [0.0,1.0]). For example, the M-THETA topology stacked to form the top layer of the 3D grid is in the meridian range. The top layer is the top layer of the 3D grid in the x direction, so the M-THETA topology activation layer is at 1.0 in the meridian position zone. Similarly, the bottom M-THETA topology activation layer is at 0.0 in the meridian position zone, also called the activation layer 0.0; the activation layers of the middle stacked M-THETA topologies correspond to the range of (0.0, 1.0), such as the middle section of the meridian plane (0.5 scale position zone) is the 0.5 position activation layer of the M-THETA topology, and all M-THETA topologies are distributed in the meridian range and stacked layer by layer along the x direction to form a 3D grid.

[0085] S21, O4H The calculation of key node information and distribution points of the main part of the grid is carried out based on the adaptive blade O grid topology feature. In order to ensure that the 3D grid does not have a large mutation in the meridian plane, the relative position of the key nodes is pre-calculated when the main part of the grid topology is generated. According to the position of the key nodes of the topological grid surface (such as the position of the nodes at the leading and trailing edges of the grid, the position of the periodic boundary, and the position of the middle nodes at the inlet and outlet of the flow channel), the grid entity line is calculated to complete the construction of the blade area O grid topology.

[0086] S22, feature area mesh is generated based on the extension of the main part of the blade O mesh area. Its structure is mainly composed of two parts: the constant part and the OHGap gap layer, which together constitute the characteristic area of ​​the flow channel of the B2B surface (M-THETA parameter plane), accurately expressing the M-THETA surface topology type and the flow channel change law in the span direction.

[0087] Furthermore, the specific steps of step S21 are as follows:

[0088] S211, grid front and rear edge point position calculation

[0089] In order to ensure that the overall inlet and outlet grids and the outer O grid layout of the M-THETA plane are more standardized in physical space, it is necessary to construct appropriate leading and trailing edge point positions and calculate the blade width near the leading and trailing edge point positions of the blade. What controls this position is not the leading and trailing edge point positions, but the relative control distance. The relative control distance is the normalized value of the relative blade width, that is, a certain proportion of the blade thickness of the geometric model; the blade width of the leading and trailing edge points can be approximated as the inscribed circle diameter of the blade at the leading and trailing edge points. Multiple groups of sampling points near the leading and trailing edge points are taken to calculate the center of the circle, and the minimum circle is used as the final inscribed circle. At the same time, the maximum blade width is calculated as the maximum limit of the inscribed circle diameter, and then the leading and trailing edge point positions of the grid are obtained according to the ratio of the relative control distance to the length of the pressure surface and suction surface of the blade;

[0090] S212, calculation of blade position in flow channel

[0091] like Figure 2 As shown, the blade has four positions in the flow channel, which specifically include the blade to the upper cycle area AREA2, the blade to the lower cycle area AREA3, the blade leading edge to the inlet area AREA1, and the blade trailing edge to the outlet area AREA4:

[0092] Distance from blade to upper / lower cycle ( Figure 2 In S1, S2), according to the geometric discrete points of the upper periodic boundary and the discrete points of the blade suction surface, the two discrete points with the closest distance between them are obtained, and then the distance is calculated by the coordinate discrete points to obtain the upper / lower periodic distance S1 of the blade, and the point closest to the leading edge point A of the upper / lower periodic boundary is also determined; similarly, the lower periodic distance S2 of the blade is obtained using the geometric discrete points and the discrete points of the blade pressure surface;

[0093] The distance from the blade to the inlet / outlet is obtained by obtaining the midpoint Q at the inlet, calculating the distance from the midpoint Q to the endpoint A of the leading edge of the blade, and obtaining the horizontal distance from the inlet to the leading edge of the blade based on the length QA*cosθ between the midpoint and the endpoint of the leading edge. For most models, the distances from the leading (trailing) edge of the blade to the blade inlet and the leading (trailing) edge to the blade outlet are similar. Based on this distance, the distance from the leading (trailing) edge to the flow channel outlet is obtained to confirm the approximate position of the nodes on the blade and the size of the node distribution.

[0094] S213, periodic boundary node position calculation

[0095] like Figure 3As shown, when generating the grid, the periodic boundary node position is calculated in advance, and the periodic boundary grid line entity is calculated using the position later. In the main part of the grid of O4H, there are 4 periodic boundary point positions in each periodic boundary that need to be calculated. When matching the periodicity, the positions may be related to each other. The 4 periodic boundary point positions include position 0 as the inlet end face, position 1 as the boundary surface corresponding to the leading edge position of the blade to the upper and lower periodic boundaries, position 2 as the boundary surface corresponding to the trailing edge position of the blade to the upper and lower periodic boundaries, and position 3 as the outlet end face;

[0096] 1) For positions 0 and 3, consider whether there is a constant part:

[0097] If there is no constant at the entrance, position 0 is 0.0. If there is a constant at the entrance, position 0 is the intersection of the constant line at the rear of the entrance and the periodic boundary line.

[0098] If there is no constant at the exit, position 3 is 1.0. If there is a constant at the exit, position 1 is the intersection of the constant line at the front of the exit and the periodic boundary line.

[0099] 2) For position 1 and position 2, directly use the method of calculating the closest point from the midline endpoint to the period boundary, and take the closest point as the position of position 1 and position 2 (principle of the shortest vertical segment). If the obtained position 1 and position 2 intersect with position 0 and position 3 or are too close, then position 1 and position 2 need to be optimized as follows:

[0100] 1. Cross judgment: judge whether position 2 is greater than position 3;

[0101] 2. Distance judgment: Calculate the horizontal distance from the trailing edge to position 3, and judge whether the ratio of the distance from position 2 to position 3 to the horizontal distance is less than a given threshold. A good topological block should have the same length of opposite sides. If the difference between the two ends is too large, Laplace optimization is required.

[0102] 3. When any of the above two conditions are met, for position 2, the position of the corresponding upper cycle boundary line is obtained based on the trailing edge point and the midpoint of the M coordinate of position 3 as the optimized new position;

[0103] S214, calculation of intermediate node positions at the entrance and exit boundaries

[0104] like Figure 4 As shown, when generating the grid, the positions of the intermediate nodes of the inlet and outlet boundaries are calculated in advance, and the positions are used to calculate the inlet and outlet boundary grid line entities later; the method for determining the two positions of the intermediate nodes of the inlet and outlet boundaries is as follows:

[0105] 1. The overall entrance and exit are evenly distributed: the position is calculated based on the ratio of the number of points on the three lines of the entrance and exit boundaries;

[0106] 2. The overall inlet and outlet are dense in the middle and gradually sparse from the middle to the two ends. The distance between the two nodes at the front and rear edges after advancement is used as the thickness of the top layer of the boundary layer grid. This thickness is used as the width of the position of the division point where the inlet and outlet are divided into three sections. The width of the remaining two ends is allocated according to the number of points.

[0107] The construction of key node information of M-THETA plane can ensure the complete topological function of the model blade, which is the technical basis for generating 3D mesh parameter plane;

[0108] S215, O4H main part point calculation method

[0109] The edges of the initial type O4H topology template are divided into 7 groups. The number and distribution of the edges in each group are the same. The corresponding relationship after topology optimization is required. Take the transformed topology (double L topology, Low-High angle) of O4H as an example:

[0110] like Figure 5 As shown, at this time, VerticalUp has only one edge above the entrance, and the two edges LINE1 and LINE2 in the figure become corresponding to the HorizonFront edge (the number of nodes matches), and in order to match the periodicity, the number of points of HorizonFront and HorizonBack must be the same, that is, the number of points of the grid edges 1 to 10 in the figure are the same; at the same time, in the upper surface of the leaf at this time, [11, 12<-->13] is a group of opposite edges, and [2<-->3] is another group of opposite edges.

[0111] The determination of the number of points is divided into two methods: given number of points and given minimum number of points and then calculated according to the actual model. The given number of points method is mainly used for HorizonMiddle, VerticalMiddle, OutO, which have relatively fixed geometric shapes in the edge of the O4H initial type topology template, and the given minimum number of points and then calculated according to the actual model method is mainly used for HorizonFront and HorizonBack, which have drastic changes in the edge of the O4H initial type topology template and need to calculate the number of points according to the length of the flow channel in the flow direction, or VerticalUp and VerticalDown, whose corresponding geometric scales will be affected by the periodic number of blades.

[0112] A reference length is set according to the geometric model. If the calculated geometric length of a part is too long relative to the reference length, the number of points is increased. If it is too short, the number of points is reduced (the minimum number of points needs to be limited). At the same time, the number of topological points is calculated using a logarithmic function.

[0113] Take the point calculation of the HorizonFront part as an example (the principles of the rest are the same):

[0114] Assume the blade length is bL, the length from the leading edge of the blade to the inlet is iL,

[0115] The ratio of the lengths of these two parts is ratio = iL / bL

[0116] The calculation formula for the HorizonFront points is as follows:

[0117] V=ratio*e*control+e

[0118] PointNumber=log(V)*minPtsNum

[0119] In the formula, control is used to adjust the speed of increasing or decreasing the number of points (different positions may require different increase or decrease speeds, i.e., growth rates); +e is used to make the function graph pass through the logical point (0, 1), so that when the ratio is close to 0 (very small relative to the reference length), the limited minimum number of points minPtsNum will be obtained; ratio*e is used to speed up the basic rate of increasing or decreasing the number of points. In the test of generating M-THETA surfaces, the point distribution of the resulting mesh topology when the ratio is 0-10 is more suitable for pre-grid generation.

[0120] 1. The calculation of the horizontal ratio is: the reference length is the blade length, the length used for comparison is the length from the blade to the leading edge and from the blade to the trailing edge, and the control value depends on whether there is topology optimization;

[0121] 2. The vertical ratio is calculated as the ratio of the periodic length to the defined standard periodic length. The control also needs to distinguish whether there is topological optimization. The number of points is concentrated when the leading edge of the blade transitions to the middle, and the number of points on the blade will also increase significantly.

[0122] For the distribution calculation method, first determine the grid line distribution of the blade part, that is, the front and rear edge grid lines are evenly distributed, and the pressure surface suction surface grid lines transition from the front and rear edges to the middle; then the distribution of the periodic boundary grid lines parallel to the pressure surface suction surface grid lines is the same as the distribution of the top layer of the boundary layer grid; finally, after advancing the boundary layer grid, there is the thickness of the top layer of the boundary layer grid, and the remaining grid lines are distributed according to the principle of evenly distributed transition with the boundary layer grid.

[0123] According to the node distribution principle of the structural grid block, the node distribution of the outlet section must be consistent with that of the inlet section, and in order to ensure its orthogonality, the node distribution of the middle section of the inlet and outlet must also be consistent with the outer O grid distribution close to the blade wall in the horizontal direction. In this way, the distribution of each grid edge in the horizontal and vertical directions of the blade is consistent and the topology of the entire blade is periodic, providing technical support for subsequent periodic boundary optimization.

[0124] S216, Topological construction method

[0125] Topological construction refers to calculating line entities. Line entities need to express the shape of ideal grid lines. Lines mapped to geometric edges are mapped by sampling a small number of point coordinates on the geometric edges as grid line entities. When generating a grid, the projection function is used to project them to the geometric edges. The shapes of the grid lines inside the grid are calculated through the boundary lines to generate the initial grid. The specific steps are as follows:

[0126] 1) Initial topology template generation, mainly consists of four steps:

[0127] 1. Create all points in the initial topological state;

[0128] 2. Create all lines in the initial topological state;

[0129] 3. Modify to the corresponding grid line according to the specific topology type;

[0130] 4. According to the specific topology type, create all faces and do not generate internal points on the faces;

[0131] 2) Boundary layer mesh generation requires calculation of the distribution of the four lines on the wall and the outward height advancement of the points on the blade. Boundary layer mesh generation usually adopts the advancement method guided by the normal vector, and the issues that need to be considered in the advancement method include the intersection processing of the mesh and the orthogonality of the mesh. Boundary layer mesh generation selects a relatively simple method of advancing the frame line. The general process is as follows:

[0132] 1. Calculate the total propulsion height H;

[0133] 2. Push all the nodes on the four lines of the wall to a height of H along their normals to obtain a series of lines consisting of new points;

[0134] 3. There may be intersections in the new lines, so cross processing is performed;

[0135] 4. Assign the distribution of the four solid lines of the wall to the advanced lines respectively;

[0136] 5. Calculate and set the support line distribution;

[0137] 6. Generate internal points of each grid;

[0138] The core of the method is intersection processing. There are two possible intersections: one is the self-intersection within a line; the other is the intersection between lines. The situation of self-intersection within a line is as follows: when there is a concave point on the line to be advanced (under the state of turbine blades), the advancement result may produce self-intersection; the method of removing self-intersection of the present invention is: starting from the starting point of the line after advancement, calculate the angle at each point. When the angle at a certain point is greater than 90°, remove this point, and repeat until no point is removed.

[0139] 3) Flow channel mesh generation

[0140] The flow channel mesh generation is mainly the generation of mesh line entities. The mesh line entities can approximately express the geometric shape to a certain extent, but the precise geometric shape also requires the projection of mesh nodes when the mesh lines are discretized.

[0141] 1. Inlet and outlet grid line entities

[0142] According to the position of the middle node of the entrance and exit, the corresponding discrete points are calculated on the entrance and exit as the entrance and exit grid line entities; if the position of the middle node of the entrance is determined to be 0.3 and 0.7 (that is, 30% and 70% of the entire entrance), then several points on the entrance geometry line (between 0.0-0.3, 0%-30%) can be directly obtained as the grid line entities.

[0143] 2. Periodic Boundary Grid Line Entity

[0144] According to the position of the upper and lower periodic boundary lines, the four intersection points intersecting with the entrance and exit are calculated and determined. The four intersection points are the left and right maximum range areas of the upper and lower periodic boundary discrete points. The discrete points within this range are the discrete point area of ​​the periodic boundary grid line entity; the discrete points within this range are within the control (accessible) range of the periodic boundary grid line entity (array).

[0145] 3. Entrance and exit horizontal middle grid line entity

[0146] By calculating the upper and lower periodic entity lines and two endpoints, given the number of sampling points, a series of vectors within the periodic boundary of the two-point coordinates are calculated, and the vectors are translated to the corresponding periodic boundary node positions. The end point of the vector is the sampling point required by the grid line entity;

[0147] 4. Internal vertical grid line entities

[0148] For the rotating machinery geometric model with too large blade inclination angle, the vertical grid lines leading to the periodic boundary of the generated M-THETA topology will point to the boundary layer area, and then from the boundary layer area to the periodic boundary. The physical distribution of the vertical grid lines is consistent with the horizontal middle grid line distribution at the inlet and outlet.

[0149] Furthermore, the specific steps of step S22 are as follows:

[0150] S221, constant part mesh generation

[0151] One edge of a mesh face in the constant part directly uses the edge of the original O4H main part, and the other three edges are generated according to the O4H exit and the actual exit position; the mesh distribution of the constant part is: the distribution of the rightmost exit edge is the same as the distribution at the exit of the O4H main part, and the distribution of the upper and lower grid lines is calculated with a uniform transition to the horizontal grid size at the exit of the O4H main part;

[0152] S222, OHGap mesh generation

[0153] The OHGap grid is the O grid that is close to the blade wall and the innermost H grid. The O grid is directly generated using the boundary layer grid generation method in the topological construction method. What needs to be specified is the first layer height, number of layers, and growth rate. The H grid in the middle needs to distinguish whether the number of nodes on the pressure side and suction side of the blade is the same. If they are the same, a grid surface is generated based on the top line of the O grid after advancement. If they are not the same, a Connector needs to be generated at the grid line entity above the O grid. The number of points of this Connector is consistent with the number of points of the grid line below the O grid, so that a grid surface can be formed;

[0154] like Figure 6 As shown in the figure, when generating the O grid close to the blade wall and the innermost H grid, when the number of nodes on the pressure surface and the suction surface is the same, the node matching is completed, and the grid of OHGap is directly promoted to generate the feature area. The corresponding 3D grid is periodic, and the pre-grid boundary connection is better after the full periodic replication, and the grid quality is higher; otherwise, the periodic nodes of the 3D grid do not match, and the periodic replication of the entire flow channel will affect the grid quality and grid solution.

[0155] S3. Generate 3D mesh by stretching and stacking the B2B surfaces in the span direction. The specific method is as follows:

[0156] Since all M-THETA surfaces are parameter planes of the 3D grid, the M-THETA surface data for 3D template stacking are actually regular two-dimensional planes. At the same time, the sliced ​​grid data of the 3D grid template in the span direction will be consistent with the 2D grid data, which can well express the global information of the 3D grid.

[0157] When constructing a 3D mesh by stretching and stacking the M-THETA surfaces in the span direction, a three-dimensional template needs to be stretched through the two-dimensional M-THETA surface at the hub. The stretching height of the M-THETA surface along the x direction is consistent with the meridian width, and the 3D mesh height is controlled by the meridian width. Then, according to the specific position of the M-THETA corresponding to the activation layer in the meridian plane (the meridian range ratio is [0.0,1.0]) (for example, the middle position of the M-THETA in the meridian plane is the 0.5 position of the activation layer), the above-constructed B2B (M-THETA) surfaces are placed layer by layer in this 3D template, and then the M-THETA surface mesh data stacked in the template is mapped to the stretched 3D mesh template through the surface to form the final 3D stacked mesh.

[0158] In actual simulation applications, the flow surface data is divided into flow channel internal flow surface data and upper and lower gap flow surface data. The M-THETA plane with the gap part is stacked as a separate top casing (bottom hub) in the stacking template, and is stretched and merged with the M-THETA stacking surface of the remaining internal flow channel (flow channel internal flow surface data) to achieve accurate and effective engineering simulation results.

[0159] S4. Complete the generation of rotating machinery surface mesh.

[0160] The above description is only an implementation mode of the present invention. It is stated again that for ordinary technicians in this technical field, several improvements can be made to the present invention without departing from the principle of the present invention. These improvements are also included in the protection scope of the claims of the present invention.

Claims

1. A method for generating a rotating machinery mesh based on a characteristic region topological structure, characterized in that: The following steps are involved: S1. Import geomTurbo geometry file; S2, topological construction based on the O4H template of the characteristic region; S3, generate 3D mesh by stretching and stacking the B2B surface in the span direction; S4. Complete the generation of rotating machinery surface mesh.

2. A method for generating a rotating machinery grid based on characteristic region topological structure according to claim 1, characterized in that: The specific steps of step S2 are as follows: The topological construction based on the feature area O4H template refers to the generation of the O-grid general template of the main part of the blade topology and the feature template of the flow channel area adaptively generated according to the topological type. The M-THETA feature topology of the current activation layer position is adaptively formed by combining the main blade O-grid area and the flow channel feature area. The topological construction based on the feature area O4H template includes the calculation of the key node information and the number of distribution points of the O4H main part grid and the grid generated by the feature area grid based on the extension of the main part of the blade O-grid area; S21, O4H The calculation of key node information and distribution points of the main part of the grid is carried out by using the O grid topology characteristics of the main part of the blade topology based on the adaptive blade topology. When the main part of the grid topology is generated, the relative position of the key nodes is calculated in advance. According to the position information of the key nodes of the topological grid surface, the grid entity line is calculated to complete the construction of the blade area O grid topology. S22, the feature area mesh is generated by extending the O mesh of the main part of the blade topology. Its structure is mainly composed of two parts: the constant part and the OHGap gap layer, which together constitute the characteristic area of ​​the B2B surface flow channel.

3. The method for generating a rotating machinery grid based on a characteristic region topological structure according to claim 1, characterized in that: The specific steps of step S21 are as follows: S211, grid front and rear edge point position calculation The blade width at the leading and trailing edge points can be approximated as the diameter of the inscribed circle of the blade at the leading and trailing edge points. Multiple groups of sampling points near the leading and trailing edge points are taken to calculate the center of the circle, and the minimum circle is used as the final inscribed circle. At the same time, the maximum blade width is calculated as the maximum limit of the inscribed circle diameter. The position of the leading and trailing edge points of the grid is obtained according to the ratio of the relative control distance to the length of the pressure surface and suction surface of the blade. S212, calculation of blade position in flow channel There are four positions of the blade in the flow channel, which specifically include the blade to the upper cycle area AREA2, the blade to the lower cycle area AREA3, the blade leading edge to the inlet area AREA1, and the blade trailing edge to the outlet area AREA4: The distance from the blade to the upper / lower cycle is obtained by obtaining the two closest discrete points between the upper / lower cycle boundary geometric discrete points and the blade suction surface / pressure surface discrete points, and then calculating the distance between the upper / lower cycle and the blade by using the coordinate discrete points. At the same time, the point closest to the endpoint of the upper / lower cycle boundary from the blade inlet position is determined; The distance from the blade to the inlet is obtained by obtaining the midpoint of the inlet, calculating the distance from the midpoint to the end point of the leading edge of the blade, and obtaining the horizontal distance from the inlet to the leading edge of the blade based on the length of the midpoint and the end point of the leading edge, and obtaining the node position and node distribution size on the blade; S213, periodic boundary node position calculation When generating the grid, the periodic boundary node positions are calculated in advance, and the periodic boundary grid line entities are subsequently calculated using the positions. In the main part of the O4H grid, there are 4 periodic boundary point positions in each periodic boundary that need to be calculated. When matching the periodicity, the positions may be related to each other. The 4 periodic boundary point positions include position 0 as the inlet end face, position 1 as the boundary surface corresponding to the leading edge position of the blade to the upper and lower periodic boundaries, position 2 as the boundary surface corresponding to the trailing edge position of the blade to the upper and lower periodic boundaries, and position 3 as the outlet end face; 1) For positions 0 and 3, consider whether there is a constant part: If there is no constant at the entrance, position 0 is 0.

0. If there is a constant at the entrance, position 0 is the intersection of the constant line at the rear of the entrance and the periodic boundary line. If there is no constant at the exit, position 3 is 1.

0. If there is a constant at the exit, position 1 is the intersection of the constant line at the front of the exit and the periodic boundary line. 2) For position 1 and position 2, directly use the method of calculating the closest point from the midline endpoint to the period boundary, and take the closest point as the position of position 1 and position 2. If the obtained position 1 and position 2 intersect with position 0 and position 3 or are too close, then position 1 and position 2 need to be optimized as follows:

1. Cross judgment: judge whether position 2 is greater than position 3; 2. Distance judgment: Calculate the horizontal distance from the trailing edge to position 3, and determine whether the ratio of the distance from position 2 to position 3 to the horizontal distance is less than a given threshold.

3. When any of the above two conditions are met, for position 2, the position of the corresponding upper cycle boundary line is obtained based on the trailing edge point and the midpoint of the M coordinate of position 3 as the optimized new position; S214, calculation of intermediate node positions at the entrance and exit boundaries When generating the grid, the positions of the middle nodes of the inlet and outlet boundaries are calculated in advance, and the inlet and outlet boundary grid line entities are calculated using the positions. The two positions of the middle nodes of the inlet and outlet boundaries are determined as follows: 1) The overall entrance and exit are evenly distributed: the position is calculated based on the ratio of the number of points on the three lines of the entrance and exit boundaries; 2) The overall inlet and outlet are dense in the middle and gradually sparse from the middle to the two ends. The distance between the two nodes at the front and rear edges after advancement is used as the thickness of the top layer of the boundary layer grid. This thickness is used as the width of the position of the division point where the inlet and outlet are divided into three sections. The width of the remaining two ends is allocated according to the number of points. S215, O4H main part point calculation The edge lines of the O4H initial type topology template are divided into 7 groups. The number of points and distribution of the edge lines in each group are the same. The number of points is determined by two methods: a given number of points and a given minimum number of points and then calculated according to the actual model. The given number of points method is mainly used for HorizonMiddle, VerticalMiddle, and OutO, which have relatively fixed geometric shapes in the edge lines of the O4H initial type topology template. The given minimum number of points and then calculated according to the actual model method is mainly used for HorizonFront and HorizonBack, which have drastic changes in the edge lines of the O4H initial type topology template and need to calculate the number of points based on the length of the flow channel in the flow direction, or VerticalUp and VerticalDown, whose corresponding geometric scales will be affected by the periodic number of blades. A reference length is set according to the geometric model. If the calculated geometric length of a part is too long relative to the reference length, the number of points is increased; if it is too short, the number of points is reduced. At the same time, a logarithmic function is used to calculate the number of topological points. S216, Topological construction method Topological construction refers to calculating line entities. Line entities need to express the shape of ideal grid lines. Lines mapped to geometric edges are mapped by sampling a small number of point coordinates on the geometric edges as grid line entities. When generating a grid, the projection function is used to project them to the geometric edges. The shapes of the grid lines inside the grid are calculated through the boundary lines to generate the initial grid. The specific steps are as follows: 1) Initial topology template generation, mainly consists of four steps:

1. Create all points in the initial topological state; 2. Create all lines in the initial topological state; 3. Modify to the corresponding grid line according to the specific topology type; 4. According to the specific topology type, create all faces and do not generate internal points on the faces; 2) Boundary layer mesh generation requires calculating the distribution of the four lines on the wall and pushing the points on the blade outward. Boundary layer mesh generation usually uses a normal vector-guided pushing method. Boundary layer mesh generation uses a relatively simple method of pushing the frame line. The process is as follows:

1. Calculate the total propulsion height H; 2. Push all the nodes on the four lines of the wall to a height of H along their normals to obtain a series of lines consisting of new points; 3. There may be intersections in the new lines, so cross processing is performed; 4. Assign the distribution of the four solid lines of the wall to the advanced lines respectively; 5. Calculate and set the support line distribution; 6. Generate internal points of each grid; 3) Flow channel mesh generation 1. Inlet and outlet grid line entities According to the positions of the intermediate nodes of the inlet and outlet, the corresponding discrete points are calculated and taken out at the inlet and outlet as the inlet and outlet grid line entities; 2. Periodic Boundary Grid Line Entity According to the position of the upper and lower periodic boundary lines, the four intersection points intersecting with the inlet and outlet are calculated and determined. The four intersection points are the left and right maximum range areas of the upper and lower periodic boundary discrete points. The discrete points within this range are the discrete point areas of the periodic boundary grid line entity.

3. Entrance and exit horizontal middle grid line entity Calculate through the upper and lower periodic boundary lines and two endpoints, given the number of sampling points, calculate a series of vectors within the periodic boundary of the two-point coordinates, translate the vectors to the corresponding periodic boundary node positions, and the end point of the vector is the sampling point required by the grid line entity; 4. Internal vertical grid line entities For the rotating machinery geometric model with too large blade inclination angle, the vertical grid lines leading to the periodic boundary of the generated M-THETA topology will point to the boundary layer area, and then from the boundary layer area to the periodic boundary. The physical distribution of the vertical grid lines is consistent with the horizontal middle grid line distribution at the inlet and outlet.

4. The method for generating a rotating machinery grid based on a characteristic region topological structure according to claim 1, characterized in that: The specific steps of step S22 are as follows: S221, constant part mesh generation One edge of a mesh face in the constant part directly uses the edge of the original O4H main part, and the other three edges are generated according to the O4H exit and the actual exit position; the mesh distribution of the constant part is: the distribution of the rightmost exit edge is the same as the distribution at the exit of the O4H main part, and the distribution of the upper and lower grid lines is calculated with a uniform transition to the horizontal grid size at the exit of the O4H main part; S222, OHGap mesh generation The OHGap grid is the O grid that is close to the blade wall and the innermost H grid. The O grid is directly generated using the boundary layer grid generation method in the topological construction method. The middle H grid needs to distinguish whether the number of nodes on the pressure surface and suction surface of the blade is the same. If they are the same, a grid surface is generated based on the top line of the O grid after advancement. If they are not the same, a Connector needs to be generated at the grid line entity above the O grid. The number of points of this Connector is consistent with the number of points of the grid line below the O grid to form a grid surface. When generating the O grid close to the blade wall and the innermost H grid, if the number of nodes on the pressure surface and the suction surface is the same, the node matching is completed, and the OHGap grid is directly promoted to generate the feature area, and its corresponding 3D grid is periodic; otherwise, the periodic nodes of its 3D grid do not match.

5. The method for generating a rotating machinery mesh based on a characteristic region topological structure according to claim 1, characterized in that: The specific method of step S3 is as follows: When constructing a 3D grid by stretching and stacking the M-THETA surfaces in the span direction, a three-dimensional template needs to be stretched through the two-dimensional M-THETA surface at the hub. The stretching height of the M-THETA surface along the x direction is consistent with the meridian plane width, and the 3D grid height is controlled by the meridian plane width. Then, according to the specific position of the M-THETA corresponding to the activation layer in the meridian plane, the above-constructed B2B surfaces are placed layer by layer into this 3D template, and then the M-THETA surface mesh data stacked in the template is mapped to the stretched 3D grid template through the surface to form the final 3D stacked grid.

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