A method and system for simulating the laying of an external duct of an aeroengine

Abstract

The application discloses an aero-engine external pipeline simulation laying method and system, and the method comprises the following steps: generating an engine casing model and a model of obstacles on the engine casing; determining the start and end positions of the external pipeline of the engine casing; generating a pipeline laying map; calculating a pipeline path by using a pipeline path planning algorithm, and performing post-processing on the generated pipeline path, wherein the post-processing comprises: removing redundant points, removing redundant turns, stretching the pipeline to be processable, and installing an edge adsorption; generating spline curve nodes according to the path nodes obtained after the post-processing; and generating a center line and a pipeline according to the spline curve nodes. The application can help designers to quickly generate a pipeline meeting constraints, and if the generated result is not satisfactory, the path can be quickly generated to fit the surface of the casing by modifying the path nodes. The operation is simple, and designers do not need to perform a large number of repetitive operations on the modeling of the casing, obstacles and pipelines, thereby improving the design efficiency.

Description

Technical Field

[0001] This invention relates to the field of external pipeline laying for engines, and specifically to a method and system for simulating the laying of external pipelines for aero-engines. Background Technology

[0002] The external piping structure of aero-engines is complex, with numerous components and high integration. Limited space makes piping installation difficult. Traditionally, aero-engine piping was laid manually on full-size metal prototypes, which struggled to guarantee design quality and efficiency. While advancements in CAD technology allow designers to lay out piping in 3D modeling software, a series of constraints still need to be considered, such as obstacle avoidance in 3D space, minimum spacing, pipe turning radii, pipe fit against the casing surface, pipe adhesion to the mounting edge, and maximum installation height. Furthermore, the aero-engine casing is a variable-diameter rotating body, making it challenging to manually design aesthetically pleasing and constraint-compliant piping paths. Modifying these paths is also inconvenient.

[0003] To ensure neat layout and improve space utilization, most aero-engine piping is laid in orthogonal directions. However, most automated layout systems for aero-engine piping currently prioritize obstacle avoidance and the shortest path, resulting in piping that is not orthogonal.

[0004] To solve the above problems, the A* algorithm and path post-processing are used to obtain pipelines with shorter total lengths that are mainly laid along orthogonal directions, while ensuring that the bends in the pipelines can be processed.

[0005] The mechanical pipeline layout module in UG can create pipelines by setting point sets and handle corners and paths of the generated pipelines. However, a series of constraints during pipeline laying still need to be considered by the designer, such as obstacle avoidance in 3D space, minimum laying spacing, pipeline turning radius, pipeline fit to the casing surface, pipeline adsorption to the installation edge, and maximum pipeline laying height. Furthermore, the engine casing is a variable-diameter rotating body, and designing aesthetically pleasing and constraint-compliant pipeline paths on such a complex rotating body using UG is quite challenging. Therefore, it is hoped that through secondary development of UG, a path can be automatically generated that meets constraints, is short, and has smooth turns, based on user-provided information such as pipeline start and end points, pipeline radius, and turning radius. Users can also modify the path by adding, deleting, and moving nodes. Summary of the Invention

[0006] The purpose of this invention is to provide a method and system for simulating the laying of external pipes for aero-engines, to solve the problem mentioned in the background art that although pipes can be generated using UG's mechanical pipeline layout module, the pipe paths still need to be set by designers. Setting the paths requires consideration of multiple constraints, and the aero-engine casing is a complex rotating body, further increasing the design difficulty and leading to a decrease in design efficiency.

[0007] A method for simulating the laying of external ducts for an aircraft engine includes the following steps:

[0008] Generate models of the engine casing and obstacles on the engine casing;

[0009] Determine the start and end points of the external pipes of the engine casing;

[0010] Generate a pipeline layout map;

[0011] The pipeline path is calculated using a pipeline path planning algorithm, and the generated pipeline path is then post-processed. The post-processing includes: removing redundant points, removing redundant turns, stretching the pipeline to make it workable, and attaching the installation edge.

[0012] Spline curve nodes are generated based on the path nodes obtained after post-processing.

[0013] Generate centerlines and pipes based on spline curve nodes.

[0014] Preferably, the engine casing model is a rotating body with a variable diameter, and the surface of the rotating body has several annular mounting edges. Its model parameters include: the piecewise function of the casing generatrix, the maximum height of the space laid on the outer surface of the casing, the minimum distance between pipes and pipes, and between pipes and obstacles, the axial position of the mounting edge on the casing, the height of the mounting edge, and the thickness of the mounting edge.

[0015] Preferably, the parameters of the obstacle model include the base point coordinates, the vector perpendicular to and pointing outward from the casing surface, the circumferential length, the length of the tangent parallel to the generatrix, and the length perpendicular to the casing surface.

[0016] Preferably, the steps for generating a pipeline laying map include: expanding obstacles outward by a certain length, which is equal to the sum of the minimum spacing and the pipeline radius; dividing the space by extending the edges of the expanded obstacles; decomposing the laying space into small-sized grids and assigning energy values ​​or state values ​​to the grids according to the constraints of pipeline laying; and generating a pipeline laying map based on the energy values ​​or state values.

[0017] Preferably, all pipes and obstacles on the surface of the casing are rotated so that the midpoint of the arc between the starting and ending points of the pipe to be laid is achieved. Greater than π / 2, meaning both the starting and ending points are controlled within... Within the radius of the arc; the actual path is obtained by rotating the path obtained by the algorithm in the reverse direction.

[0018] Preferably, the pipeline path planning algorithm is a five-direction A* algorithm, which searches in five directions: up, forward, backward, left, and right. The pipeline explores one grid at a time in the h direction. When the next exploration direction of the pipeline is the same as the current forward direction, the pipeline moves one grid along the exploration direction. When the two directions are different, the coordinates of the exploration point are calculated based on the coordinates of the current node and the pipeline's specified value. Then, a binary search method is used to find which grid in the three-dimensional grid map this new coordinate is located in, thereby obtaining the number of grids that need to be moved.

[0019] Preferably, the evaluation function of the five-direction A* algorithm is:

[0020]

[0021] n-1 represents the current point, n represents the exploration point, (h,t,z) are the coordinates of the exploration point, r represents the distance of the exploration point from the axis of the casing, and d represents the distance between the current point and the exploration point. end ,t end ,z end ) represents the endpoint coordinates; α is used to suppress the movement of the pipeline in the h direction. When the current point of the pipeline and the exploration point are at the same height, α is 1. When the pipeline moves in the h direction, d is multiplied by an α that is larger than 1 to increase the cost of moving in the h direction.

[0022] Preferably, if the user is not satisfied with the generated path, they can select the path to generate a list of path nodes. By moving, adding, or deleting path nodes, a preview path is generated based on the modified list of path nodes. The user can then decide whether to keep the modified result based on the preview.

[0023] The present invention also provides a simulated laying system for external ducts of an aircraft engine, comprising:

[0024] The model generation module is used to generate models of the engine casing and obstacles on the engine casing;

[0025] The map generation module is used to determine the start and end points of the external pipes of the engine casing and generate a pipe laying map.

[0026] The path planning module uses a pipeline path planning algorithm to calculate the pipeline path and performs post-processing on the generated pipeline path.

[0027] The pipeline generation module is used to generate spline curve nodes based on the path nodes obtained after post-processing; and to generate centerlines and pipelines based on the spline curve nodes.

[0028] Preferably, it also includes a pipeline path modification module, which is used to move, add, and delete path nodes.

[0029] Beneficial effects: Although piping can be generated in UG using the mechanical piping layout module, the pipe paths still need to be set by the designer. Setting the paths requires considering multiple constraints, and the complex rotating body of an aero-engine casing further increases the design difficulty. This invention helps designers quickly generate piping that meets the constraints. If the generated results are unsatisfactory, paths that fit the casing surface can be quickly generated by modifying the path nodes. The operation is simple, eliminating the need for designers to perform numerous repetitive operations on modeling the casing, obstacles, and piping, thus improving design efficiency. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the pipeline's path.

[0031] Figure 2 This is a diagram illustrating the elimination of redundant turns.

[0032] Figure 3 This is a diagram illustrating the elimination of consecutive redundant turns.

[0033] Figure 4 This is a schematic diagram of moving nodes to stretch the pipe.

[0034] Figure 5 This is a schematic diagram of spline curve nodes generated based on path nodes.

[0035] Figure 6 This is a schematic diagram of the pipeline laying steps.

[0036] Figure 7 This is a diagram illustrating the steps for modifying the pipeline path.

[0037] Figure 8 This is a diagram showing the effect of the installation.

[0038] Figure 9 It refers to modifying the effect image. Detailed Implementation

[0039] The present invention will be further described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0040] To improve the design efficiency of aero-engine piping laying, this invention provides the following technical solution: an aero-engine external piping laying plugin based on UG secondary development, which implements functions interactively using a *.dll executable file, and stores the data required for piping laying in a *.csv file. The dll calls the exe executable file to perform path calculations, and the data required for the calculations is read from the csv file. This plugin is one of the specific implementation methods and systems for simulating the laying of external aero-engine pipes.

[0041] like Figure 6 As shown, the pipeline laying steps are as follows:

[0042] Step 1: Model the casing as a rotating body with a variable diameter and several annular mounting edges on its surface. Input the piecewise function of the casing's generatrix, the maximum height of the space on the outer surface of the casing, the minimum spacing between pipes and between pipes and obstacles, the axial position of the mounting edges on the casing, the height of the mounting edges, and the thickness of the mounting edges.

[0043] Step Two: Obstacle Modeling. During installation, the actual obstacle is replaced with a sector that completely encloses it. Obstacle generation is determined by the base point (the center point of the obstacle's bottom), the vector perpendicular to and pointing outwards from the casing surface, the circumferential length, the length of the tangent to the parallel generatrix, and the length perpendicular to the casing surface. The base point is determined by clicking on the casing surface or inputting xyz coordinates. The program ultimately generates the obstacle placed perpendicular to the casing surface.

[0044] Step 3: Pipeline Initialization. Determine the start and end point locations by clicking on the surfaces (casing surface, obstacle surface) to which the start and end points are attached, or by entering xyz coordinates. Since the pipeline needs to extend a certain distance perpendicular to the attachment surface, click on the start and end point attachment surfaces to generate vectors perpendicular to the attachment surface and extending outwards from it. Enter the pipeline's inner diameter, outer diameter, and turning radius. The program will ultimately generate a sphere with a diameter equal to the pipeline's outer diameter on the attachment surface to mark the start and end points.

[0045] Step 4: Laying Pipes. Click the start or end point to select the pipe for path planning, enter the search range, and the inhibition rate for radial path movement. The DLL first iterates through the objects (obstacles, pipe start point, pipe end point, pipeline) generated in the UG interface and updates the object status (existence, non-existence) in the CSV file. Then, it calls the EXE to calculate the pipeline path. Finally, the path is generated in the UG interface as a spline curve, and the pipeline is generated based on the spline curve.

[0046] This plugin uses A* as the path planning algorithm, which is widely used for path planning on two-dimensional plane maps. Here, it is used for path planning on a three-dimensional surface of rotation with a variable diameter. Therefore, the map needs to be processed. Considering that the pipes need to be able to be manufactured and that the pipes have as few turns as possible, the generated paths need to be post-processed.

[0047] Because the pipeline path is described by a series of spatial point coordinates, a suitable coordinate system is needed to describe the available space outside the aircraft engine casing before searching for the pipeline path. Since the aircraft engine casing is a rotating body with a variable diameter, a coordinate system (h, t, z) is used to determine a point in space, where h represents the radial distance from the point to the casing surface, so h = 0 for a point on the casing surface, t is the circumferential radius of the point, and z is the axial distance of the point.

[0048] Before searching for the pipeline path, the laying space needs to be represented using a data structure, i.e., a laying map needs to be generated. The meshing method decomposes the laying space into small-sized grids and assigns energy or state values ​​to the grids based on the constraints of the pipeline laying. Considering the large surface area of ​​the casing, to reduce the algorithm's map exploration time, the space is divided by extending and expanding the edges of obstacles. The grid's state value includes 0 and 1, where 0 represents no obstacle and 1 represents an obstacle. Because the algorithm calculates the path along the pipeline centerline, obstacles need to be expanded outward by a certain length before meshing; this length is equal to the sum of the minimum spacing and the pipeline radius. Because the casing surface is a body of revolution, to meet the requirement of finding a shorter path, the path range of a pipeline in the t direction generally does not exceed π, such as... Figure 1 As shown, path 2 should be chosen instead of path 1 from the starting point to the ending point. However, path 2 crosses the line with an arc of 0, meaning that a sudden change from 0 to 2π occurs during the path movement, affecting the normal operation of the algorithm. To solve this problem, all pipes and obstacles on the casing surface are rotated to make the midpoint of the arc between the starting and ending points of the pipe to be laid. Slightly greater than π / 2, meaning both the starting and ending points are controlled within... Within the radius of the arc. To obtain the actual path, simply rotate the path obtained by the algorithm in the reverse direction.

[0049] After representing the laying space using a laying map, the start and end points of the laying map also need to be determined. Because the laid pipes need to extend a section perpendicular to the attachment surface from the start and end points, the extension start and end points need to be calculated; these two points also serve as the start and end points of the laying map. The extension start and end points can be calculated using the attachment point coordinates stored in the CSV file and the vector perpendicular to the attachment surface. The extension length is determined by the pipe radius.

[0050] After generating the laying map and its starting and ending points, the A* algorithm can be used to search for pipeline paths. Here, we will first introduce the principle of the A* algorithm. The A* algorithm takes the starting point as the initial node and uses the evaluation function to evaluate the points around the node. The algorithm will select the point with the smaller evaluation function value as the next node. The key point is that this selection is not limited to the points around the current node, but includes all points that have been evaluated but have not yet become nodes. This allows the algorithm to choose a previously evaluated point to continue exploring when it gets stuck in a dead end. This continues until the end point is finally found. By influencing the selection of nodes through the heuristic function in the evaluation function, the algorithm is more inclined to search towards the end point, which significantly improves the search efficiency while finding a path with the minimum cost. The evaluation function of the A* algorithm is expressed as Equation (1):

[0051]

[0052] In the formula, n represents the exploration point, G(n) represents the distance cost incurred by the path from the starting point to exploration point n, and the heuristic function H(n) represents the estimate of the distance cost from exploration point n to the destination. In the formula, (x, y, z) are the coordinates of the exploration point, (x...y...z ... end ,y end ,z end Let F(n) be the coordinates of the destination. The sum of F(n) and F(n) is a comprehensive evaluation of the past and future of this path.

[0053] Since the search involves traversing pipe paths, and these pipes require 90° bends, a minimum length for each pipe segment is necessary to ensure the bend can be fabricated. This minimum length is called the specified value, and it is related to the pipe's turning radius. To guarantee that the length from the exploration point to the current node meets this specified value, the step size of the A* algorithm is adjusted. When the next exploration direction of the pipe is the same as the current direction, the pipe moves one grid along that direction. When the two directions are different, the coordinates of the exploration point are calculated based on the coordinates of the current node and the specified pipe value. Then, a binary search is used to determine which grid in the 3D mesh map this new coordinate falls into, thus determining the number of grids that need to be moved.

[0054] To save radial space in the casing, the pipeline maintains single-cell exploration in the h-direction, i.e., variable step size is not used. Furthermore, the path should be kept at the same height as much as possible to reduce the occupation of radial space. Because the casing is a rotating body, and to achieve the above objectives, the evaluation function is modified to equation (2).

[0055]

[0056] n-1 represents the current point, n represents the exploration point, (h,t,z) are the coordinates of the exploration point, r represents the distance of the exploration point from the axis of the casing, and d represents the distance between the current point and the exploration point.end ,t end ,z end ) represents the endpoint coordinates. α is used to suppress the movement of the pipeline in the h direction. When the current point of the pipeline and the exploration point are at the same height, α is 1. When the pipeline moves in the h direction, d is multiplied by an α that is larger than 1 to increase the cost of moving in the h direction.

[0057] The steps for post-processing the generated pipeline path include:

[0058] (1) Remove redundant points. After A* calculation is completed, a series of path nodes will be obtained. Each pair of adjacent nodes is a pipe segment. Since the cross product of the direction vectors of adjacent pipe segments is 0, the turning points can be filtered out.

[0059] (2) Remove redundant turns. Because the A* evaluation function can only find the shortest path and does not consider the cost of turns, it may generate multiple turns, some of which may be redundant, such as... Figure 2 As shown, P0-P1-P2-P3 represents the original path. It can be seen that this path has two turns, and moving P1 to P1' or P2 to P2' can eliminate one turn. Whether a turn can be eliminated depends solely on whether a collision occurs along the path indicated by the dotted line. Sometimes, structures identical to P0-P1-P2-P3 will appear consecutively, such as... Figure 3 The path P0-P1-P2-P3-P4-P5 contains consecutive redundant turns, requiring multiple rounds of processing to completely eliminate them. Figure 3 As shown in the example, the first round is: P0-P1-P2-P3-P4-P5->P0-P1'-P2-P3-P4'-P5 (removing redundant turns)->P0-P1'-P4'-P5 (removing redundant points). The second round is: P0-P1'-P4'-P5->P0-P1'-P4'-P5 (removing redundant turns)->P0-P1'-P5 (removing redundant points).

[0060] (3) Stretch the pipe to make it machinable. In the variable step size section of the A* search process, it was mentioned that the shortest pipe length can be disregarded for the pipe's movement in the h-direction and the path to the final destination. To make this pipe segment machinable, nodes need to be moved to stretch the pipe. For example... Figure 4 Let the pipe radius be r and the pipe turning radius be R, with R = 3r by default. If a pipe has a right-angle turn at both ends, the minimum shortest pipe length is 2R. In the figure, h < 2R, so a bend cannot be generated. Therefore, it is necessary to move point P1 to P1'. To ensure that for any h < 2R, point P1' can be found so that the pipe can bend with the turning radius, the following inequality (3) must be satisfied:

[0061]

[0062] Therefore, to ensure that h has a solution in 2θ∈[0,π / 2], K≥1.18 is required. Furthermore, K=1.18 guarantees that h can take any value within [0,2R]. This means that setting the shortest pipe segment length to 2.18R guarantees that the pipe can always bend by moving node P1 with the pipe's turning radius. The moving distance P1P1' of point P1 is = h / tan2θ. To make the pipe bendable, P1P1' needs to be moved ∈ [4Rsinθ]. 2 θ / tan2θ,R / (K-tanθ)].

[0063] (4) Installation edge adsorption. After the pipeline path is calculated, traverse each installation edge segment, find the pipeline segment that moves circumferentially closest to the installation edge, and determine whether the distance between the pipeline segment and the installation edge is less than a certain value. If so, move the pipeline segment closer to the installation edge without collision.

[0064] Step 5: Generate spline curve nodes based on the path nodes. For example... Figure 5 Two adjacent pipe sections are divided into two straight pipe sections (the centerline of these straight pipes is not a straight line, but a line segment that fits the surface of the casing. If the pipe moves circumferentially, the centerline of the straight pipe is actually an arc rather than a straight line) and a middle bend. The middle node of the straight pipe can be obtained by uniformly interpolating the (h,t,z) coordinates of the starting and ending points. The center of the bend needs to be found first; the method for calculating the center is shown below.

[0065]

[0066]

[0067] It is a vector whose direction is from the center of the circle to the endpoint P0'P2', O xyz Using the coordinates of the center of the circle and two points P0' and P2' on the circle, we can obtain the other nodes on the center line of the bend.

[0068] If a user is not satisfied with the generated path, they can select the path to generate a list of path nodes. By moving, adding, or deleting path nodes, a preview path is generated based on the modified list of path nodes. The user can then decide whether to keep the changes based on the preview. Figure 7 As shown, the steps for modifying the pipeline path are as follows:

[0069] Step 1: In the UG interface, click the "Modify Pipeline Path" button, select the pipeline to be modified, and click "Apply." The program will hide the selected pipeline and display the centerline, read the pipeline nodes from the CSV file, display the nodes in UG, and generate a temporary feature group. All node objects are stored in the temporary feature group according to the path movement order.

[0070] Step 2: Modify nodes. Users can move and delete existing nodes, and add nodes to temporary feature groups. Before generating a new path, ensure that all node objects are stored in the temporary feature group in the order they were moved along the path.

[0071] Step 3: In the UG interface, click the "Modify Pipeline Path" button, then click the centerline. The program will generate spline curve nodes based on the path nodes in the temporary feature group, as described earlier. The program generates temporary centerlines and temporary pipes based on the spline curve nodes for previewing the pipe laying effect. If you click "cancel" at this point, the modification result will be discarded, and Step 2 will be executed again. If you click "apply," the original centerline and pipes will be replaced by the temporary centerline and pipes, meaning the path modification is complete.

[0072] The above description is only a preferred embodiment of the present invention. This scheme can also be used to design the stator slots for other bearingless motors. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for simulating the laying of external ducts in an aero-engine, characterized in that, Includes the following steps: Generate models of the engine casing and obstacles on the engine casing; Determine the start and end points of the external pipes of the engine casing; Generating a pipeline laying map involves the following steps: expanding obstacles outward by a certain length, equal to the sum of the minimum spacing and the pipeline radius; dividing the space by extending the edges of the expanded obstacles; decomposing the laying space into small-sized grids and assigning energy or state values ​​to the grids based on the pipeline laying constraints; generating a pipeline laying map based on the energy or state values; and rotating all pipelines and obstacles on the casing surface to ensure that the midpoint of the arc between the starting and ending points of the pipeline to be laid is within the specified range. Greater than The starting point and the finish line are both under control. Within the radius of the arc; the actual path is obtained by rotating the path obtained by the algorithm in the opposite direction. A pipeline path is calculated using a pipeline path planning algorithm. The generated pipeline path undergoes post-processing, including: removing redundant points, removing redundant turns, stretching the pipeline to make it workable, and attaching the installation edges. The pipeline path planning algorithm is a five-directional A* algorithm, meaning the algorithm searches in five directions: up, forward, backward, left, and right. The pipeline... The exploration proceeds in a single grid direction. When the next exploration direction of the pipe is the same as the current forward direction, the pipe moves one grid along the exploration direction. When the two directions are different, the coordinates of the exploration point are calculated based on the coordinates of the current node and the pipe's specified value. Then, a binary search is used to find which grid in the 3D grid map this new coordinate is located in, thus obtaining the number of grids that need to be moved. Spline curve nodes are generated based on the path nodes obtained after post-processing. Generate centerlines and pipes based on spline curve nodes.

2. The method for simulating the laying of external pipes for an aero-engine according to claim 1, characterized in that, The engine casing model is a rotating body with a variable diameter. The rotating body has several annular mounting edges on its surface. Its model parameters include: the piecewise function of the casing generatrix, the maximum height of the space laid on the outer surface of the casing, the minimum distance between pipes and between pipes and obstacles, the axial position of the mounting edge on the casing, the height of the mounting edge, and the thickness of the mounting edge.

3. The method for simulating the laying of external ducts of an aero-engine according to claim 1, characterized in that, The parameters of the obstacle model include the base point coordinates, the vector perpendicular to and pointing outward from the casing surface, the circumferential length, the length of the tangent parallel to the generatrix, and the length perpendicular to the casing surface.

4. The method for simulating the laying of external ducts for an aero-engine according to claim 3, characterized in that, The evaluation function of the five-direction A* algorithm is: ； Indicates the current point, Indicates the point of exploration. The coordinates of the exploration point, This indicates the distance of the exploration point from the axis of the casing. This represents the distance between the current point and the exploration point. The coordinates of the endpoint; Used to suppress pipelines Movement in direction, when the current point of the pipe and the exploration point are at the same height, The value is 1, when the pipe is facing... When moving in direction, Multiply by a factor greater than 1 To increase The cost of directional movement.

5. The method for simulating the laying of external pipes for an aero-engine according to claim 1, characterized in that, If a user is not satisfied with the generated path, they can select the path to generate a list of path nodes. By moving, adding, or deleting path nodes, a preview path is generated based on the modified list of path nodes. The user can then decide whether to keep the changes based on the preview results.

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