Blade thermal state blade profile calculation method

Abstract

The blade thermal state blade profile calculation method comprises the following steps that S1, a cold state blade profile surface model, a thermal state blade profile surface model and a blade strength finite element model are established, the cold state blade profile surface model is provided with a cold state blade profile surface grid, the thermal state blade profile surface model is provided with a thermal state blade profile surface grid, and the blade strength finite element model is provided with a thermal state blade profile surface grid; pneumatic pressure loads are arranged on nodes of the grids on the surface of the thermal-state blade profile; s2, converting the node coordinates of the surface grid of the hot-state blade profile to the surface grid of the cold-state blade profile; s3, mapping the pneumatic pressure load on the surface grid of the cold-state blade profile obtained in the step S2 to a surface unit 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; and S5, iteratively calculating the blade strength finite element model in the 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 thermal-state blade profile of the blade. According to the method, the more accurate thermal-state blade profile of the blade can be obtained.

Description

Technical Field

[0001] The invention relates to the field of aeroengines, and in particular to the field of cold-hot state model conversion of blades. Background Art

[0002] Aircraft engines are highly complex and sophisticated thermal machines used to power aircraft, including turbojet / turbofan engines, turboshaft / turboprop engines, etc. The cold state of blades refers to the state of blades in non-working states such as manufacturing state, while the hot state of blades refers to the state of blades in operation. During operation, blades are subject to centrifugal force, aerodynamic pressure load, temperature load, etc., which are different from blades in the cold state.

[0003] The blade in the aerodynamic design state is a hot blade profile under the action of centrifugal force, aerodynamic load, and temperature load, while the blade processing and manufacturing needs to be carried out on the cold blade profile. Therefore, the fan blade needs to be converted from hot to cold to obtain the cold blade profile and then manufacture the blade. In many cases, it is necessary to apply a hot load to the cold blade profile, calculate the cold blade profile back to the hot state, and then evaluate the corresponding aerodynamic performance. For example, the analysis of the impact of blade processing out of tolerance on aerodynamic performance; after external damage such as bird strikes and ice strikes, the damaged blades are heated and then the aerodynamic and thrust losses are evaluated. Because the aerodynamic load is obtained under the hot blade profile, and the blade to be evaluated is a cold blade profile, it is necessary to first convert the cold blade profile to a hot blade profile, and then perform aerodynamic calculations.

[0004] However, there are significant differences between the hot and cold states, especially for fan blades. The above method results in the inability to accurately interpolate the hot aerodynamic loads onto the cold blade shape, which in turn results in errors in the calculation of aerodynamic performance based on the hot blade shape, ultimately leading to inaccurate design results, affecting the performance and airworthiness certification of the final product. Summary of the invention

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

[0006] The method for calculating the hot blade profile of a blade to achieve the above-mentioned purpose comprises the following steps: S1. establishing a cold blade profile surface model, a hot blade profile surface model and a blade strength finite element model, wherein the cold blade profile surface model has a cold blade profile surface mesh, the hot blade profile surface model has a hot blade profile surface mesh, and the nodes of the hot blade profile surface mesh carry aerodynamic pressure loads; S2. transforming the node coordinates of the hot blade profile surface mesh to the cold blade profile surface mesh; S3. mapping the aerodynamic pressure load on the cold blade profile surface mesh obtained in step S2 to the surface unit of the blade strength finite element model; S4. applying a 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 of each node on the blade strength finite element model, and extracting the iteratively calculated blade strength finite element model as the hot blade profile.

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

[0008] In one or more embodiments, in step S3, mapping includes the following steps: generating a plurality of pressure surface units from the blade strength finite element model; searching for a node on the cold blade surface mesh that is closest to the node in space with any node in the pressure surface unit as the center, and mapping the aerodynamic pressure load on the searched node to the node on the pressure surface unit; and taking the weighted average of the aerodynamic pressure loads of each node on the pressure surface unit as the pressure value of the pressure surface unit.

[0009] In one or more embodiments, in step S5, a distributed memory-based parallel algorithm is used for solving.

[0010] In one or more embodiments, in step S5, the blade strength finite element model and its corresponding wheel are calculated together.

[0011] In one or more embodiments, in step S5, in 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 the node in that direction; and the displacement values ​​of the next calculation process are continued to be calculated based on the new coordinates.

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

[0013] The above method utilizes the aerodynamic load information of the blade surface on the hot CFD model and uses the strength finite element model for iterative calculation, so as to inversely calculate and obtain a hot model with more accurate surface load distribution and deformation. This can improve the accuracy of the hot blade profile generated by inverse calculation of the cold blade profile, and ensure the accuracy of the aerodynamic performance evaluation based on the hot blade profile; at the same time, it can improve the calculation accuracy of the strength calculation based on the cold model, and ensure the service safety of the engine blades. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0015] Figure 1 It is a flow chart of the method for calculating the hot blade profile of a blade;

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

[0017] Figure 3 is a schematic diagram of the blade surface mesh;

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

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

[0020] Fig. 6A It is an overall comparison diagram of the hot blade profile calculated by the traditional method and the original hot blade profile surface model;

[0021] Figure 6B yes Fig. 6A A magnified view of the middle lobe tip. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with specific embodiments and drawings. More details are elaborated in the following description to facilitate a full understanding of the present invention. However, the present invention can obviously be implemented in a variety of other ways different from the description herein. Those skilled in the art can make similar generalizations and deductions based on actual application situations without violating the connotation of the present invention. Therefore, the protection scope of the present invention should not be limited by the content of this specific embodiment.

[0023] It should be noted that these and other subsequent drawings are only examples and are not drawn to scale, and should not be used to limit the actual scope of protection required by the present invention.

[0024] The hot blade data under working condition is easy to obtain and can be used to guide the design of blades, while the processing and manufacturing of blades need to be carried out in cold state, and the blade profiles of hot blades and cold blades are not consistent. Therefore, it is necessary to accurately derive the cold blade profile to the hot blade profile so that the derived hot blade profile meets the hot blade load.

[0025] The hot blade profile calculation method disclosed in the present invention enables the cold blade profile to be accurately calculated back to the hot blade profile, thereby ensuring the accuracy of the aerodynamic performance evaluation based on the hot blade profile.

[0026] Reference Figure 1 As shown, the method includes the following steps: S1. establishing a cold blade surface model, a hot blade surface model and a blade strength finite element model, wherein the cold blade surface model has a cold blade surface mesh, the hot blade surface model has a hot blade surface mesh, and the nodes of the hot blade surface mesh carry aerodynamic pressure loads; S2. transforming the coordinates of the nodes of the hot blade surface mesh to the cold blade surface mesh correspondingly; S3. mapping the aerodynamic pressure load on the cold blade surface mesh obtained in step S2 to the surface unit of the blade strength finite element model; S4. applying a 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 of each node on the blade strength finite element model, and extracting the iteratively calculated blade strength finite element model as the hot blade profile of the blade.

[0027] Specifically, in step S1, the cold blade profile model and the hot blade profile model are Figure 3 The surface mesh shown is used to simulate the pressure surface 101 and the suction surface 102 of the blade. Since the hot blade data is relatively easy to obtain, each node H on the hot blade surface mesh of the hot blade surface model 0 (i, j) can be assigned to the blade surface aerodynamic pressure load to form H(i, j, k), where i and j represent grid coordinates and k represents the aerodynamic pressure load.

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

[0029] To ensure the corresponding transformation in step S2, the structured mesh topology of the cold and hot surface models is completely consistent, so that the number of model nodes and node connection relationship of the cold blade surface model and the hot blade surface model are the same, so the cold and hot models have great similarity. The cold and hot blade surface models include their own pressure surface node set and suction surface node set. Each node set corresponds to the node coordinates in the hot CFD load file. The node coordinates C (i, j, k) of the cold model can be replaced once according to the node order to complete the coordinate transformation of the aerodynamic model in step S2.

[0030] Different from the CFD cold and hot surface model, the blade strength finite element model is a solid model, including the pressure surface and the suction surface, and the internal structure of the blade is also constructed by the mesh. Each node on the pressure surface and the suction surface also forms a pressure surface node set and a suction surface node set.

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

[0032] For example, in a specific embodiment, first generate a pressure surface unit based on the pressure surface node set of the strength finite element model and the strength finite element model; traverse the nodes of the pressure surface unit, and for each node on the pressure surface unit, search for the node on the cold blade surface grid with the closest spatial distance, and the pressure value corresponding to the node is used as the pressure value of the current traversal point in the strength finite element model; traverse each pressure surface unit, and use the weighted average of the pressure values ​​of each node as the pressure value of the surface unit, and use the pressure value as the load of the finite element model to participate in the subsequent solution calculation. Finally, the application of the suction surface and pressure surface loads is completed in sequence.

[0033] In addition to the aerodynamic pressure load, the blade is also affected by temperature and rotation speed. Therefore, in step S4, the state that needs to be back-calculated for the hot state is selected, and the corresponding rotation speed and temperature field loads are applied to the blade strength finite element model as the load for the subsequent finite element strength calculation. The rotation speed and temperature are both body loads, which are assigned to each coordinate point on the surface and inside of the blade strength finite element model.

[0034] After the blade strength finite element model is built and the load conditions are attached, the solution parameters are set and the calculation is performed. The blade calculation must take into account rotational stiffening and geometric nonlinearity, and the influence of the disk must also be considered. Therefore, the blade strength finite element model and the disk it matches are calculated together. The contact between the blade and the disk is set to standard contact.

[0035] In order to speed up the calculation efficiency, a distributed memory-based parallel algorithm is used to solve the problem.

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

[0037] In the global Cartesian coordinate system, in a single calculation process, the coordinate values ​​and displacement values ​​of each node in the 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 the node in that direction; the displacement values ​​of the next calculation process are calculated based on the new coordinates. That is, the displacements of each node in the three directions obtained in a single calculation are superimposed on the global coordinates of the corresponding node in the three directions, and the model nodes and coordinates after the coordinates are updated are output. After multiple iterations, the model nodes and coordinates after the final calculation are output, which is the final hot blade shape of the blade.

[0038] The above method applies load conditions and environmental conditions to the hot blade profile through the blade strength, and performs computational evolution of the finite element model, which can be more accurate than the hot model obtained by the traditional interpolation method. Figure 5 The comparison diagram of the hot blade profile obtained in step S5 and the original hot blade profile surface model is shown. The red color represents the original hot model, and the pink color represents the inverse hot model. The two completely overlap. Fig. 6A and 6B A comparison diagram of the hot blade profile calculated by the traditional method and the original hot blade profile surface model is shown. In the enlarged diagram at the blade tip, it can be seen that the front edge of the blade tip of the two models has a spacing U of 11 mm. Therefore, in comparison, it can be seen that the deformation amount of the present application is more accurate.

[0039] The present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or multiple times in different positions in this specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0040] Although the present invention is disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, any modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall 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: The steps include: S1. Establishing a cold blade surface model, a hot blade surface model and a blade strength finite element model, wherein the cold blade surface model has a cold blade surface mesh, the hot blade surface model has a hot blade surface mesh, and the nodes of the hot blade surface mesh carry aerodynamic pressure loads; S2. transforming the node coordinates of the hot blade surface mesh to the cold blade surface mesh; S3. Mapping the aerodynamic pressure load on the cold airfoil surface grid obtained in step S2 to the surface unit of the blade strength finite element model; S4. Applying speed body load and temperature body 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 hot blade profile of the blade.

2. The method according to claim 1, characterized in that In step S1, the number of model nodes and the node connection relationship of the cold blade profile model and the hot blade profile model are made the same.

3. The method according to claim 1, characterized in that In step S3, mapping includes the following steps: The blade strength finite element model generates a plurality of pressure surface elements; Taking any node in the surface unit of the pressure surface as the center, searching for a node on the cold airfoil surface grid that is closest to the node in space, and mapping the aerodynamic pressure load on the searched node to the node on the surface unit of the pressure surface; The weighted average of the aerodynamic pressure loads of each node on the surface unit of the pressure surface is taken as the pressure value of the surface unit of the pressure surface.

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

5. The method according to claim 1, characterized in that In step S5, the blade strength finite element model and its matching wheel are calculated together.

6. The method according to claim 1, characterized in that In step S5, In 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 the node in that direction; and the displacement values ​​of the next calculation process are continued to be calculated based on the new coordinates.

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

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