Blade hot state profile calculation method

Abstract

A blade hot state airfoil profile calculation method is provided, comprising the following steps: S1. establishing a cold state airfoil profile surface model, a hot state airfoil profile surface model and a blade strength finite element model, the cold state airfoil profile surface model has a cold state airfoil profile surface grid, the hot state airfoil profile surface model has a hot state airfoil profile surface grid, and the nodes of the hot state airfoil profile surface grid are provided with aerodynamic pressure load; S2. transforming the node coordinates of the hot state airfoil profile surface grid to the cold state airfoil profile surface grid; S3. mapping the aerodynamic pressure load on the cold state airfoil profile surface grid obtained in step S2 to the surface elements of the blade strength finite element model; S4. applying a rotating speed body load and a temperature body load to the blade strength finite element model; S5. iteratively calculating the blade strength finite element model in step S4, calculating the displacement amount of each node on the blade strength finite element model, and extracting the blade strength finite element model after the iteration calculation as a blade hot state airfoil profile. The above method can obtain a more accurate blade hot state airfoil profile.

Description

Technical Field

[0001] This invention relates to the field of aero-engines, and more specifically to the field of cold and hot state model conversion of blades. Background Technology

[0002] An aero-engine is a highly complex and precise thermodynamic machine used to power aircraft, including various types such as turbojet / turbofan engines and turboshaft / turboprop engines. The cold state of a blade refers to its condition when it is in a non-operating state, such as during manufacturing. The hot state refers to the blade when it is in operation, subjected to centrifugal force, aerodynamic pressure loads, and temperature loads, which differs from the cold state.

[0003] In its aerodynamic design state, a fan blade is a hot airfoil subjected to centrifugal force and aerodynamic loads (i.e., temperature loads). However, blade manufacturing requires a cold airfoil configuration. Therefore, fan blades need to undergo a hot-cold state conversion to obtain a cold airfoil for blade manufacturing. In many cases, hot loads need to be applied to the cold airfoil to recalculate it back to a hot state, thereby evaluating the corresponding aerodynamic performance. Examples include analyzing the impact of blade manufacturing deviations on aerodynamic performance; and assessing the aerodynamic and thrust losses after reheating damaged blades following external object damage such as bird strikes or ice strikes. Because the aerodynamic loads are obtained under a hot airfoil configuration, while the blade to be evaluated is a cold airfoil, it is necessary to first convert the cold airfoil to a hot airfoil configuration before performing aerodynamic calculations.

[0004] However, there are significant differences between hot and cold states, especially for fan blades, where the differences are quite large. The above method makes it impossible to accurately interpolate the aerodynamic loads of the hot state onto the cold state airfoil, which in turn makes it impossible to accurately back-calculate the cold state airfoil back to the hot state airfoil. This leads to errors in the aerodynamic performance calculation based on the hot state airfoil, ultimately resulting in inaccurate design results and affecting the performance and airworthiness certification of the final product. Summary of the Invention

[0005] One objective of this invention is to provide a method for calculating the hot airfoil profile of a blade, which can obtain a more accurate hot airfoil profile of the blade and ensure the accuracy of aerodynamic performance evaluation based on the hot airfoil profile.

[0006] The blade hot airfoil calculation method to achieve the above objectives includes the following steps: S1. Establishing a cold airfoil surface model, a hot airfoil surface model, and a blade strength finite element model. The cold airfoil surface model has a cold airfoil surface mesh, and the hot airfoil surface model has a hot airfoil surface mesh. The nodes of the hot airfoil surface mesh have aerodynamic pressure loads. S2. Transforming the node coordinates of the hot airfoil surface mesh onto the cold airfoil surface mesh. S3. Mapping the aerodynamic pressure loads on the cold airfoil surface mesh obtained in step S2 onto the surface elements of the blade strength finite element model. S4. Applying rotational volume loads and temperature volume loads to the blade strength finite element model. S5. Iteratively calculating the blade strength finite element model in step S4, calculating the displacement of each node on the blade strength finite element model, and extracting the iteratively calculated blade strength finite element model as the blade hot airfoil.

[0007] In one or more embodiments, the number of model nodes and the node connection relationships of the cold airfoil model and the hot airfoil model are the same.

[0008] In one or more embodiments, in step S3, the mapping includes the following steps: generating multiple pressure surface elements from the blade strength finite element model; searching for nodes on the cold-state airfoil surface mesh that are spatially closest to any node within the pressure surface element, and mapping the aerodynamic pressure load on the searched node to the node on the pressure surface element; and using the weighted average of the aerodynamic pressure loads of each node on the pressure surface element as the pressure value of the pressure surface element.

[0009] In one or more embodiments, in step S5, a distributed memory-based parallel algorithm is used to solve the problem.

[0010] In one or more embodiments, in step S5, the finite element model of the blade strength and the wheel it is paired with are calculated together.

[0011] In one or more embodiments, in step S5, during a calculation process, the coordinate values ​​and displacement values ​​of each node in three directions in the global Cartesian coordinate system are obtained; the coordinate values ​​and displacement values ​​of each node in the same direction are added together and used as the new coordinates of that node in that direction; the displacement value of the next calculation process is calculated based on the new coordinates.

[0012] In one or more embodiments, in step S1, the cold airfoil model, the hot airfoil model, and the blade strength finite element model each include their respective pressure surface node sets and suction surface node sets.

[0013] The above method utilizes the aerodynamic load information on the blade surface from the hot CFD model and uses the strength finite element model for iterative calculation to obtain a more accurate hot model of surface load distribution and deformation. This can improve the accuracy of the hot blade generated from the cold blade and ensure the accuracy of aerodynamic performance evaluation based on the hot blade. At the same time, it can improve the calculation accuracy of strength calculation based on the cold model and ensure the service safety of engine blades. Attached Figure Description

[0014] The above and other features, properties and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings and embodiments, wherein:

[0015] Figure 1 This is a flowchart of the method for calculating the hot airfoil shape of a blade;

[0016] Figure 2 This is a schematic diagram of the blade structure;

[0017] Figure 3 This is a schematic diagram of the leaf-shaped surface mesh;

[0018] Figure 4 This is a schematic diagram of the information content within the aerodynamic load file;

[0019] Figure 5 This is a comparison diagram between the obtained hot blade profile and the original hot blade profile surface model;

[0020] Figure 6A This is a comparison diagram of the overall hot airfoil shape calculated by traditional methods and the original hot airfoil surface model;

[0021] Figure 6B yes Figure 6A A magnified view of the tip of the middle leaf. Detailed Implementation

[0022] The present invention will be further described below with reference to specific embodiments and accompanying drawings. More details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention can obviously be implemented in many other ways different from those described herein. Those skilled in the art can make similar extensions and derivations based on actual application situations without departing from the spirit of the present invention. Therefore, the scope of protection of the present invention should not be limited by the content of this specific embodiment.

[0023] It should be noted that these and other accompanying drawings are merely examples and are not drawn to scale, and should not be construed as limiting the scope of protection of the present invention.

[0024] Hot-state blade data is readily available and can guide blade design, while blade manufacturing must be carried out in a cold state. However, the airfoil profiles of hot-state and cold-state blades are not the same. Therefore, it is necessary to accurately derive the hot-state airfoil profile from the cold-state airfoil profile so that the derived hot-state airfoil profile conforms to the hot-state blade load.

[0025] The blade hot airfoil calculation method described in this disclosure enables the cold airfoil to be accurately reversed back to the hot airfoil, ensuring the accuracy of aerodynamic performance evaluation based on the hot airfoil.

[0026] Reference Figure 1 As shown, the method includes the following steps: S1. Establish a cold-state airfoil model, a hot-state airfoil model, and a blade strength finite element model. The cold-state airfoil model has a cold-state airfoil surface mesh, and the hot-state airfoil model has a hot-state airfoil surface mesh. The nodes of the hot-state airfoil surface mesh have aerodynamic pressure loads; S2. Transform the coordinates of the nodes of the hot-state airfoil surface mesh to the cold-state airfoil surface mesh accordingly; S3. Map the aerodynamic pressure loads on the cold-state airfoil surface mesh obtained in step S2 to the surface elements of the blade strength finite element model; S4. Apply rotational loads and temperature loads to the blade strength finite element model; S5. Iteratively calculate the blade strength finite element model in step S4, calculate the displacement of each node on the blade strength finite element model, and extract the iteratively calculated blade strength finite element model as the hot-state airfoil.

[0027] Specifically, in step S1, both the cold airfoil model and the hot airfoil model are... Figure 3 The surface mesh shown is used to simulate the pressure surface 101 and suction surface 102 of the airfoil. Since hot blade data is readily available, each node H0(i,j) on the hot airfoil surface mesh of the hot airfoil model can be assigned an aerodynamic pressure load to the blade surface, forming H(i,j,k), where i and j represent the mesh coordinates and k represents the aerodynamic pressure load.

[0028] In some embodiments, aerodynamic load files in text format under the thermal model can be generated for the pressure surface and suction surface respectively. The file format includes x-coordinate, y-coordinate, z-coordinate, and aerodynamic pressure scalar values, such as... Figure 4 As shown.

[0029] To ensure the corresponding transformation in step S2, the structured mesh topology of the cold and hot airfoil models is completely identical, making the number of model nodes and node connections the same for both the cold and hot airfoil models. Therefore, the cold and hot airfoil models have a high degree of similarity. Each cold and hot airfoil model includes its own pressure surface node set and suction surface node set. Since these node sets correspond, the node coordinates in the hot CFD load file can be replaced one by one with the corresponding node coordinates C(i,j,k) of the cold model, completing the coordinate transformation of the aerodynamic model in step S2.

[0030] Unlike the CFD hot and cold surface model, the blade strength finite element model is a volume model, including pressure and suction surfaces, and the internal structure of the blade is also constructed by mesh. The nodes on the pressure and suction surfaces also form pressure surface node sets and suction surface node sets, respectively.

[0031] In step S3, since the node distribution of the blade strength finite element model is different from that of the cold airfoil surface model, the mapping of aerodynamic pressure loads specifically includes the following mapping steps: taking any node in the pressure surface element as the center, searching for the node C(i,j,k) on the cold airfoil surface mesh that is spatially closest to that node, and mapping the aerodynamic pressure load k on the searched node C(i,j,k) to the node on the pressure surface element; taking the weighted average of the aerodynamic pressure loads of each node on the pressure surface element as the pressure value of the pressure surface element.

[0032] In one specific embodiment, pressure surface elements are first generated based on the pressure surface node set and the strength finite element model. Then, the nodes of each pressure surface element are traversed. For each node in the pressure surface element, the node on the cold-state airfoil surface mesh with the closest spatial distance is searched, and the pressure value corresponding to that node is used as the pressure value of the currently traversed point in the strength finite element model. For each pressure surface element, the weighted average of the pressure values ​​of its nodes is used as the pressure value of that surface element, and this pressure value is used as the load in the finite element model for subsequent solution calculations. Finally, the application of suction and pressure surface loads is completed sequentially.

[0033] In addition to aerodynamic pressure loads, the blade is also affected by temperature and rotational speed. Therefore, in step S4, the state requiring back-calculation of the thermal state is selected, and corresponding rotational speed and temperature field loads are applied to the blade strength finite element model as loads for subsequent finite element strength calculations. Both rotational speed and temperature are volume loads, assigned to each coordinate point on the surface and inside the blade strength finite element model.

[0034] After the finite element model of the blade strength is completed and the load conditions are applied, the solution parameters are set and the calculation is performed. The blade calculation needs to consider rotational stiffening and geometric nonlinearity, as well as the influence of the rotor disk; therefore, the blade strength finite element model and its mating rotor disk are calculated together. The contact between the blade and the rotor disk is set as a standard contact.

[0035] To accelerate computational efficiency, a distributed memory-based parallel algorithm is used for solving the problem.

[0036] After multiple iterations, each node in the finite element model of blade strength has displacement, and finally the hot blade profile is extracted.

[0037] In a global Cartesian coordinate system, during a single calculation, the coordinates and displacements of each node in three directions are obtained. The coordinates and displacements of each node in the same direction are added together and used as the new coordinates for that node in that direction. The displacement values ​​for the next calculation are then calculated based on these new coordinates. In other words, the displacements of each node in three directions obtained from a single calculation are superimposed onto the global coordinates of the corresponding node in three directions, and the updated model nodes and coordinates are output. After multiple iterations, the final calculated model nodes and coordinates are output, which is the final obtained hot blade profile.

[0038] The above method calculates and evolves the hot airfoil of the blade by applying load conditions and environmental conditions based on the blade strength, and can obtain a more accurate hot airfoil model than the traditional interpolation method. Figure 5 The diagram shows a comparison between the hot blade profile obtained in step S5 and the original hot blade profile surface model. Red represents the original hot model, and pink represents the inversely calculated hot model; the two completely overlap. Figure 6A and 6B The diagram shows a comparison between the hot airfoil calculated using traditional methods and the original hot airfoil surface model. A magnified view at the blade tip reveals an 11mm gap U at the leading edge of the two models. Therefore, it can be seen that the deformation amount calculated in this application is more accurate.

[0039] This application uses specific terms to describe embodiments of the application. Terms such as "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic associated with at least one embodiment of the application. Therefore, it should be emphasized and noted that references to "an embodiment," "one embodiment," or "an alternative embodiment" in different locations throughout this specification do not necessarily refer to the same embodiment. Furthermore, certain features, structures, or characteristics in one or more embodiments of the application can be appropriately combined.

[0040] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any variations and modifications can be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the invention, fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for calculating the hot blade profile, characterized in that, Includes the following steps: S1. Establish a cold-state airfoil model, a hot-state airfoil model, and a blade strength finite element model. The cold-state airfoil model has a cold-state airfoil surface mesh, and the hot-state airfoil model has a hot-state airfoil surface mesh. The nodes of the hot-state airfoil surface mesh have aerodynamic pressure loads. S2. Transform the node coordinates of the hot airfoil surface mesh to the cold airfoil surface mesh; S3. Map the aerodynamic pressure load on the cold airfoil surface mesh obtained in step S2 onto the surface elements of the blade strength finite element model; S4. Apply rotational load and temperature load to the blade strength finite element model; S5. Iteratively calculate the blade strength finite element model in step S4, calculate the displacement of each node on the blade strength finite element model, and extract the blade strength finite element model after iterative calculation as the blade hot airfoil.

2. The method as described in claim 1, characterized in that, In step S1, the number of model nodes and the node connection relationship of the cold airfoil model and the hot airfoil model are made the same.

3. The method as described in claim 1, characterized in that, In step S3, the mapping includes the following steps: The blade strength finite element model generates multiple pressure surface elements; Centered on any node within the pressure surface unit, search for the node on the cold airfoil surface grid that is spatially closest to that node, and map the aerodynamic pressure load on that node to the node on the pressure surface unit. The weighted average value of the aerodynamic pressure loads at each node on the pressure surface unit is taken as the pressure value of the pressure surface unit.

4. The method as described in claim 1, characterized in that, In step S5, a distributed memory-based parallel algorithm is used to solve the problem.

5. The method as described in claim 1, characterized in that, In step S5, the finite element model of the blade strength and the wheel it is paired with are calculated together.

6. The method as described in claim 1, characterized in that, In step S5, In one calculation process, the coordinates and displacements of each node in three directions in the global Cartesian coordinate system are obtained; the coordinates and displacements of each node in the same direction are added together and used as the new coordinates of that node in that direction; the displacement values ​​of the next calculation process are then calculated based on the new coordinates.

7. The method as described in claim 1, characterized in that, In step S1, the cold airfoil model, the hot airfoil model, and the blade strength finite element model each include their respective pressure surface node sets and suction surface node sets.

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