A strength load analysis method for aircraft engine mounted blades

Abstract

The present invention belongs to the technical field of aero-engine design, and specifically relates to a strength load analysis method for aero-engine joint blades, comprising the following steps: S1, establishing a single blade mesh model, and establishing a joint load data import model; S2, applying load to the single blade sub-grid model based on finite element analysis software, and obtaining a load finite element analysis model of the single blade; S3, setting joint parameters through the joint load data import model; S4, generating a joint blade finite element model and joint load according to the joint parameters and the load finite element analysis model of the unit blade; S5, reading the joint load, judging whether the temperature load at the connection position of the inner and outer rings is continuous, and if not, resetting the node tolerance, and repeating step S4 until the temperature load is continuous, and saving the joint blade finite element model. The present invention can effectively shorten the finite element pre-processing time and calculation accuracy, and is suitable for the pre-processing of finite element analysis of joint blades of aero-engines.

Description

Technical Field

[0001] The invention belongs to the technical field of aero-engine design, and in particular relates to a strength load analysis method for aero-engine mounted blades. Background Art

[0002] The aircraft engine, as the heart of the aircraft, is known as the jewel in the crown of modern industry. It is a high-speed rotating thermomechanical device. The engine stator blades, especially the engine turbine guide vanes, are located after the combustion chamber and before the tail nozzle. They are in a harsh environment of high temperature, high pressure and high speed. They must not only withstand the erosion of high-speed airflow, but also thermal loads and mechanical loads. The load environment is very harsh. Therefore, in the structural design of the turbine guide vanes, while ensuring performance, structural safety and reliability are important factors to be considered in the design. In order to ensure the safe and reliable operation of the guide vanes, they are generally designed as a combined structure, that is, several blades are grouped together as a group, sharing the same inner and outer rings. The combined blade structure is shown in the figure. Figure 2 .

[0003] In the process of aircraft engine design and development, in order to ensure the structural integrity and safety and reliability of the entire engine, the strength analysis of the main load-bearing components must be carried out in accordance with relevant standards and specifications. Whether it is the fan stator blades in a high-pressure environment or the turbine guide blades in a high-temperature, high-pressure environment that are prone to ablation, fracture and other failures, detailed strength analysis work must be carried out, including static strength analysis, vibration characteristics analysis, fatigue life analysis, and endurance creep life analysis. Among them, static strength analysis is the first and most important work to be carried out, and load analysis processing is the premise of static strength analysis.

[0004] The present invention takes the turbine guide blade under extremely harsh working conditions of high temperature and high pressure as an example. When the blade is subjected to strength simulation analysis, based on the structure and load characteristics of the turbine guide blade, the loads selected for strength calculation analysis are the gas pressure of the blade body and blade back, the temperature load of the blade as a whole (with inner and outer rings), and the axial force load of the inner and outer rings, etc. The given calculation loads are mainly for single blades. The guide blade is a joint structure. Due to the inconsistency of rigidity and boundary conditions between the single blade and the joint blade, the strength stress calculation results of the single blade are quite different from those of the joint blade, and the calculation results of the single blade cannot simulate the stress of the real blade well. In order to make the blade calculation results consistent with the stress results of the real blade when working, it is necessary to use the joint blade model for finite element strength analysis. Therefore, it is necessary to analyze and process the load of the single blade, and convert the single blade load into a joint load and apply it to the joint structure.

[0005] For aircraft engine turbine guide blades, generally 4 to 6 blades form a group, called a combined blade, and a multi-blade assembly forms a ring blade, which serves as the first-stage stator blade assembly of the engine turbine. For turbine combined guide blades, they are in a harsh environment of high temperature, high pressure, and high speed, and are subjected to extremely complex loads, such as aerodynamic loads, temperature loads, axial forces, etc. There are many types of loads, and there are also many load conditions (such as ground slow state, maximum aerodynamic load state, maximum thermal load state, cruising state, etc.). How to accurately and quickly apply multiple conditions and multiple types of loads to the combined blade model is a major technical problem in the pre-processing of blade strength analysis. At present, the commonly used blade combined load processing method is mainly based on manual rotation, and requires the use of special pre-processing software. This processing method is inefficient and time-consuming. Part of the load will be lost during the load rotation process, and the temperature field load at the connection position of the inner and outer rings after rotation will be discontinuous; at the same time, there are generally many strength calculation conditions, and several or more than a dozen conditions generally need to be considered during strength analysis. Manual processing is extremely inefficient and has low accuracy. Summary of the invention

[0006] Aiming at the problems of low load processing efficiency and poor accuracy in the pre-processing of finite element strength analysis of mounted blades of existing aero-engines, a strength load analysis method for mounted blades of aero-engines was proposed, which could effectively save the finite element pre-processing time and improve the efficiency and accuracy of the simulation analysis of the strength of mounted blades.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: a strength load analysis method for aero-engine mounted blades, comprising the following steps:

[0008] S1. Establish a finite element mesh model of a single blade and establish a joint load data import model;

[0009] S2. Based on the finite element analysis software, a load is applied to the single blade mesh model to obtain a load finite element analysis model of the single blade;

[0010] S3, setting the joint assembly parameters by importing the joint assembly load data into the model;

[0011] S4. Open the single blade model in the finite element analysis software, read in the combined load analysis program processed in step S3, and generate a combined blade finite element model and combined load.

[0012] S5. Read the combined load in the finite element model of the combined blade to determine whether the temperature load at the connection position of the inner and outer rings is continuous. If it is not continuous, it is necessary to reset the node tolerance in step S3 and repeat step S4 until the temperature load at the connection position of the inner and outer rings is continuous, and save the finite element model of the combined blade.

[0013] In step S1, establishing a single blade finite element model comprises the following steps:

[0014] S111, analyzing the blade structure and determining the single blade selected for modeling;

[0015] S112, performing a rotary cutting process on the blades according to the blade assembly form and quantity;

[0016] S113, performing geometric processing on the selected single blade to ensure that the corresponding surfaces of the upper and lower edge plates are consistent;

[0017] S114, meshing a single blade based on pre-processing meshing software;

[0018] S115, exporting the blade mesh model obtained by the pre-processing mesh software into a format corresponding to the finite element analysis software.

[0019] In step S3, the assembly parameters set by importing the assembly load data into the model include:

[0020] Load conditions, number of ganged blades, number of single-gang blades, maximum number of nodes and maximum number of elements in the finite element model of a single blade, and tolerances for nodes associated with the upper and lower inner rings.

[0021] In the step S2, the loads applied to the single blade include aerodynamic loads, temperature loads and axial force loads.

[0022] In step S2, the method of applying a load to a single blade is:

[0023] S201, Apply aerodynamic load:

[0024] In the dedicated meshing tool, the aerodynamic load and the single-blade finite element model are adjusted to the overlapping position, that is, the blade model and the load data points are completely matched, and then the gas pressure load is interpolated with the blade basin and blade back surface nodes in the single-blade finite element model, and the aerodynamic load is equivalent to the nodes of the blade basin and blade back. For multiple calculation conditions, the corresponding aerodynamic load processing is performed respectively.

[0025] S202, apply temperature load:

[0026] Adjust the given temperature field result model and the single blade finite element calculation model to the same position, and then interpolate the temperature load of all nodes of the finite element calculation model with the model of the given temperature field result. The interpolated temperature result also needs to be processed by heat conduction in the blade finite element calculation model to finally generate the temperature field load of the single blade.

[0027] S203. Apply axial force loads to the inner ring and the outer ring.

[0028] In the step S1, the combined load data import model is developed by Fortran programming software.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention provides a method for analyzing the strength load of aero-engine mounted blades, which overcomes the problems of low efficiency, poor precision, and long cycle in the load processing of mounted blades in the prior art. The present invention uses a single-piece blade finite element model and a data processing program to realize the generation of multiple loads such as blade pressure, temperature, and axial force, and realizes the rapid generation of the mounted model and the assembly of the connection interface, and realizes the automatic batch processing of multiple working conditions to calculate the load. Compared with manual load processing, the load processing of the present invention is high in precision and time, and can save up to 98% of time, and is particularly suitable for multi-load working conditions, such as transient multi-condition loads. The present invention can effectively shorten the finite element pre-processing time and calculation accuracy, and is very suitable for load analysis in the pre-processing of aero-engine mounted blades. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A flow chart of a method for processing and analyzing the combined loads of turbine guide blades of an aero-engine provided by the present invention;

[0032] Figure 2 It is a schematic diagram of the guide blade assembly structure;

[0033] Figure 3 Schematic diagram of the monolithic structure of the guide vane;

[0034] Figure 4 It is a finite element model of a single blade;

[0035] Figure 5 This is the finite element model of a single blade after aerodynamic loads are applied;

[0036] Figure 6 This is the finite element model of a single blade after applying the temperature field load;

[0037] Figure 7 This is the finite element model of a single blade after all loads are applied;

[0038] Figure 8 Model of the mounted blade assembly with all loads. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0040] like Figure 1 As shown, the present invention provides a method for analyzing the strength load of aero-engine mounted blades, comprising the following steps:

[0041] S1. Establish a finite element mesh model of a single blade and establish a joint load data import model.

[0042] Specifically, in step S1, establishing a single blade finite element model includes the following steps:

[0043] S111. Analyze the blade structure and determine the single blade to be used for modeling.

[0044] First, check the structure of the turbine blades, the combination configuration of the blades, the structure of the upper and lower edge plates, whether the interior is hollow, etc., and select one of the blades and the inner and outer rings of the corresponding angle area as the single blade model for subsequent modeling and analysis, such as Figure 2 The figure shows a triple-mounted blade. The blade in the middle position and the inner and outer rings of its corresponding fan-shaped segment can be selected as the analysis object.

[0045] S112, performing a rotary cutting process on the blades according to the blade assembly form and quantity.

[0046] According to the combination form of the blades and the number of blades in a ring, the angle α occupied by a blade is obtained as:

[0047] α=360 / ( c * d ); (1)

[0048] Where: c is the number of joints in a complete ring, d The number of single blades in a group is determined by rotating the selected single blade (with inner and outer rings) along the circumferential direction at an angle α. The two cutting surfaces corresponding to the inner and outer rings must be symmetrical and consistent.

[0049] S113. Perform geometric processing on the selected single blade to ensure that the corresponding surfaces of the inner and outer rings are consistent.

[0050] In this embodiment, based on the complexity of the engine blade structure, special pre-processing meshing software is used for meshing. Before meshing, the selected single blade model needs to be geometrically processed, such as removing redundant characteristic lines and feature surfaces, as well as removing features that have little impact on the results, and ensuring that the faces corresponding to the inner and outer rings are consistently associated, that is, the nodes on both sides of the corresponding positions of the inner and outer rings are circumferentially coordinated during subsequent meshing.

[0051] S114. Based on the pre-processing meshing software, mesh the single blade.

[0052] In this embodiment, the model is cut into multiple small blocks based on the pre-processing meshing software, and each block is meshed from difficult to easy. To ensure the calculation accuracy, solid units with intermediate nodes are generally used, mainly hexahedral units. After the meshing is completed, the mesh of the overall model needs to be quality checked to ensure that its Jacobi value is greater than 0.5. According to the complexity of the model, the Jacobi value can be appropriately reduced at the local position, but it is best not to be lower than 0.3.

[0053] S115, exporting the single blade mesh model obtained by the pre-processing meshing software into a file in a corresponding format of the finite element analysis software.

[0054] Specifically, in step S1, the joint assembly load data is imported into the model to set the joint assembly parameters, and the joint assembly input parameters include: the number of load conditions, the number of joint assemblies, the number of single-joint blades, the maximum number of nodes and the maximum number of units in the finite element model of a single blade, and the tolerance of the upper and lower inner ring associated nodes.

[0055] S2. Based on the finite element analysis software, a load is applied to the mesh model of the single blade to obtain the load of the finite element analysis model of the single blade.

[0056] According to the working environment of the blade, the loads borne by the blade include gas pressure load, inner and outer ring axial force load, blade body and inner and outer ring temperature load. Therefore, in step S2, the loads applied to the single blade include aerodynamic load, temperature load and axial force load.

[0057] In step S2, the method of applying a load to a single blade is:

[0058] S201, Apply aerodynamic load:

[0059] The aerodynamic loads on the blades are mainly the gas pressure loads on the blade base and the back of the blade. These gas pressure loads are generally expressed in terms of "coordinates ( x , y , z), pressure load", and the aerodynamic load and the single-blade finite element model are adjusted to coincide with each other in the dedicated meshing tool (that is, the blade model and the load data points are completely fitted), and then the gas pressure load is interpolated with the nodes of the blade basin and the back surface of the single-blade finite element model, and the aerodynamic load is equivalent to the nodes of the blade basin and the back surface. For multiple calculation conditions (multiple strength calculation points), the corresponding aerodynamic load processing needs to be performed respectively.

[0060] S202, apply temperature load:

[0061] Adjust the given temperature field result model and the single blade finite element calculation model to the same position, then interpolate the temperature load of all nodes of the finite element calculation model with the given temperature field result. The interpolated temperature result also needs to be processed by simple heat conduction in the finite element calculation model to finally generate the temperature field load of the single blade. When multiple calculation conditions are involved, the corresponding temperature field load processing needs to be performed separately.

[0062] S203, apply axial force load to inner ring and outer ring:

[0063] Due to the inconsistent pressure at the front and rear ends of the blade, an axial force will be generated at the inner ring / outer ring. In order to simplify the load handling process, the pressure difference on both sides of the inner ring / outer ring can be applied to one surface or to each surface separately. For hollow blades, gas pressure loads need to be applied in the hollow cavity.

[0064] S204, generate load steps for each calculation condition

[0065] The gas pressure load of the blade basin and blade back, the temperature field load of the blade body and the inner and outer rings, and the axial force load of the inner and outer rings are applied to the same single blade, that is, the single blade strength calculation load is successfully synthesized. For multiple calculation conditions, in order to facilitate subsequent load analysis, all loads of each condition need to be written out in the corresponding load step.

[0066] S3. Set the joint assembly parameters by importing the joint assembly load data into the model.

[0067] Open the program file of the joint load data import model, and add the information such as the number of load calculation conditions, the number of blades in a joint assembly, the number of joint assembly in a complete ring, the tolerance size of the inner and outer rings, the maximum number of single blade units and nodes, etc. Specifically, in this embodiment, the joint load data import model can be developed by Fortran programming software.

[0068] S4. Open the single blade model in the finite element analysis software, read in the combined load analysis program processed in step S3, and generate a combined blade finite element model and combined load.

[0069] S5. Read the combined load in the finite element model of the combined blade to determine whether the temperature load at the connection position of the inner and outer rings is continuous. If it is not continuous, it is necessary to reset the node tolerance in step S3 and repeat step S4 until the temperature load at the connection position of the inner and outer rings is continuous, and save the finite element model of the combined blade.

[0070] In this embodiment, the generated joint assembly load is read into the joint assembly finite element model to check the continuity and consistency of the load. If the temperature load is discontinuous, it means that the given tolerance is too small, and the tolerance interpolation value needs to be reset and step S4 needs to be re-run. If the joint assembly model and the load are continuous and consistent, the joint assembly load processing work is completed, and the joint assembly model and the load are saved in the corresponding files to facilitate the next step of strength simulation analysis.

[0071] For example, take a turbine guide blade of an engine as an example, which is a triple assembly model. Figure 2 , take one of the leaves for analysis, see Figure 3 First, the model geometry is cleaned and the finite element mesh is divided. The finite element model is shown in Figure 4 , import the processed model into the large-scale finite element pre-processing software, and apply aerodynamic loads, temperature loads, axial force loads and boundary conditions respectively, see Figure 5 and Figure 6 The finite element model of a single blade after all loads are applied is shown in Figure 7 By importing the joint assembly load data into the model to set the joint assembly parameters, it is necessary to set the axial coordinates of the overall coordinate axis, calculate the number of load conditions, the number of blades in a joint, the number of joint rings, the assembly tolerance, etc. After the settings are completed, the blade joint assembly load processing can be performed. The processed load model is shown in Figure 8 , check the load and boundary conditions. If the tolerance setting is too small and the temperature field is discontinuous, the tolerance needs to be adjusted. This model is the final finite element simulation analysis model.

[0072] In summary, the present invention provides a method for processing and analyzing the loads of aircraft engine mounted blades, which overcomes the problems of low efficiency, poor precision, and long cycle in the manual processing of mounted blade loads in the prior art. The present invention imports the assembly parameters through the assembly load data file, which not only realizes the assembly generation of multiple loads such as blade pressure, temperature, and axial force, but also realizes the rapid generation of the assembly model and the assembly of the connection interface, and realizes the automatic batch processing of the calculated loads of multiple working conditions. Compared with manual load processing, the load processing of the present invention is efficient and accurate, and can save up to 98% of time, and is particularly suitable for multi-load working conditions, such as transient multi-working conditions. The advantages of the present invention are more obvious, and can effectively shorten the finite element pre-processing time and calculation accuracy, and is very suitable for the pre-processing of aircraft engine mounted blades.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A strength load analysis method for aircraft engine mounted blades, characterized in that: The following steps are involved: S1. Establish a finite element mesh model of a single blade and establish a joint load data import model; S2. Based on the finite element analysis software, a load is applied to the single blade mesh model to obtain a load finite element analysis model of the single blade; S3, setting the joint assembly parameters by importing the joint assembly load data into the model; S4, opening the single blade model in the finite element analysis software, reading the combined load analysis program processed in step S3, and generating a combined blade finite element model and combined load; S5, reading the combined load in the combined blade finite element model, judging whether the temperature load at the connection position of the inner and outer rings is continuous, if not, resetting the node tolerance in step S3, and repeating step S4 until the temperature load at the connection position of the inner and outer rings is continuous, and saving the combined blade finite element model; In step S1, establishing a single blade finite element model comprises the following steps: S111, analyzing the blade structure and determining the single blade selected for modeling; S112, performing a rotary cutting process on the blades according to the blade assembly form and quantity; S113, performing geometric processing on the selected single blade to ensure that the corresponding surfaces of the upper and lower edge plates are consistent; S114, meshing a single blade based on pre-processing meshing software; S115, exporting the blade mesh model obtained by the pre-processing mesh software into a format corresponding to the finite element analysis software.

2. The strength load analysis method of an aircraft engine mounted blade according to claim 1, characterized in that: In step S3, the assembly parameters set by importing the assembly load data into the model include: Load conditions, number of ganged blades, number of single-gang blades, maximum number of nodes and maximum number of elements in the finite element model of a single blade, and tolerances for nodes associated with the upper and lower inner rings.

3. The strength load analysis method of an aircraft engine mounted blade according to claim 1, characterized in that: In the step S2, the loads applied to the single blade include aerodynamic loads, temperature loads and axial force loads.

4. The strength load analysis method of an aircraft engine mounted blade according to claim 3, characterized in that: In step S2, the method of applying a load to a single blade is: S201, Apply aerodynamic load: In the dedicated meshing tool, the aerodynamic load and the single blade finite element model are adjusted to coincide with each other, that is, the blade model and the load data points are completely matched, and then the gas pressure load is interpolated with the nodes of the blade basin and the back surface of the single blade finite element model, and the aerodynamic load is equivalent to the nodes of the blade basin and the back surface of the blade. For multiple calculation conditions, the corresponding aerodynamic load processing is performed respectively; S202, apply temperature load: Adjust the given temperature field result model and the single blade finite element calculation model to the same position, then interpolate the temperature load of all nodes of the finite element calculation model with the model of the given temperature field result. The interpolated temperature result also needs to be heat-conducted in the blade finite element calculation model to finally generate the temperature field load of the single blade; S203. Apply axial force loads to the inner ring and the outer ring.

5. The strength load analysis method of an aircraft engine mounted blade according to claim 1, characterized in that: In the step S1, the combined load data import model is developed by Fortran programming software.

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