Numerical Evaluation Method for the Safety of Aeroengine Rotor Systems

Abstract

The present invention relates to a numerical evaluation method for the safety of an aero-engine rotor system, which comprises the following steps: according to the three-dimensional structural characteristics of the rotor system, distinguishing the axisymmetric part and the non-axisymmetric part, establishing a Fourier element finite element model for the axisymmetric part and a three-dimensional cyclic symmetric element finite element model for the non-axisymmetric part; forming a coupling between the Fourier element finite element model and the three-dimensional cyclic symmetric element finite element model by using a multi-point constraint algorithm; applying contact pairs according to the actual contact positions between components in the rotor system, setting contact parameters, setting large deformation geometric nonlinear parameters, applying engine loads and setting boundary constraints, setting load steps and parallel solution parameters, conducting parallel solution to obtain the numerical analysis results of the rotor system; and analyzing the single-point stress, life and fracture margin of the rotor system through the analysis results to complete the numerical evaluation of the safety of the rotor system. The present invention is used to improve the accuracy of the evaluation.

Description

Technical Field

[0001] The present invention relates to the field of aeroengines, and particularly to a numerical evaluation method for the safety of an aeroengine rotor system. Background Art

[0002] An aeroengine is a culmination of modern industrial technologies, and the rotor system is one of the most core components of an aeroengine. With the increasingly high requirements for the performance, reliability, and service life of aeroengines, the rotational speed of the engine is continuously increasing while the weight needs to be minimized as much as possible. The operating load environment of the engine rotor is becoming increasingly harsh. It not only has to bear the centrifugal force at tens of thousands of revolutions per minute but also the thermal stress and pressure load brought by high temperature and high pressure. During operation, it may also bear complex loads such as vibration and shock. The safety of the rotor system is crucial for the safety of the entire engine and the entire aircraft, and it is particularly important to conduct effective prediction and evaluation on it. Summary of the Invention

[0003] Some embodiments of the present invention propose a numerical evaluation method for the safety of an aeroengine rotor system to improve the accuracy of evaluation.

[0004] Some embodiments of the present invention provide a numerical evaluation method for the safety of an aeroengine rotor system, which includes the following steps:

[0005] According to the three-dimensional structural characteristics of the aeroengine rotor system, distinguish the axisymmetric part and the non-axisymmetric part, establish a Fourier element finite element model for the axisymmetric part, and establish a three-dimensional cyclic symmetric element finite element model for the non-axisymmetric part;

[0006] Form a coupling between the Fourier element finite element model and the three-dimensional cyclic symmetric element finite element model by using the multi-point constraint algorithm;

[0007] Apply contact pairs according to the actual contact positions between components in the rotor system, set contact parameters, set large deformation geometric nonlinear parameters, apply engine loads and set boundary constraints, set load steps and set parallel solution parameters, and perform parallel solution on a computer platform to obtain the numerical analysis results of the aeroengine rotor system; and

[0008] Analyze the single-point stress of the aeroengine rotor system, analyze the life of the aeroengine rotor system, and analyze the burst margin of the aeroengine rotor system through the numerical analysis results of the aeroengine rotor system to complete the numerical evaluation of the safety of the aeroengine rotor system.

[0009] In some embodiments, before the parallel solution parameters of the Fourier element finite element model, integrate the equations of the Fourier element finite element model and set the number of circumferential Fourier nodes ;

[0010] If the number of circumferential Fourier nodes is odd, the shape functions of the finite element model of the Fourier element are:

[0011]

[0012] If the number of circumferential Fourier nodes N is even, the shape functions of the finite element model of the Fourier element are:

[0013]

[0014] Among them, represents the shape function corresponding to three displacement components respectively. Among them, is the radial node displacement in the cylindrical coordinate system, is the circumferential node displacement in the cylindrical coordinate system axial node displacement, is the shape function of a plane quadrilateral or triangular element, , , are the Fourier series coefficients.

[0015] In some embodiments, establishing a three-dimensional cyclic symmetric unit finite element model for the non-axisymmetric part includes: establishing a 20-node full hexahedron element using the cyclic symmetric model, keeping the element size consistent at the positions where components in the rotor system come into contact, and keeping the mesh of the cyclic symmetric plane consistent.

[0016] In some embodiments, forming a coupling between the finite element model of the Fourier element and the three-dimensional cyclic symmetric unit finite element model includes:

[0017] Selecting the connection surface of the three-dimensional cyclic symmetric unit finite element model as the main surface, and selecting the contact surface of the finite element model of the Fourier element as the slave surface;

[0018] Establishing the constraint relationship between each slave surface node and the main surface node, and the constraint relationship satisfies the following formula:

[0019]

[0020] Among them, is the degree of freedom of the slave node, is the degree of freedom of the main node, is the weighting coefficient, is the number of nodes participating in the coupling, is the constant term.

[0021] In some embodiments, applying contact pairs according to the actual contact positions between components in the rotor system includes: using standard contact to simulate the interaction between the working surfaces of the split blade tenons and the disk, using bonded contact to simulate the threaded action between the bolt and the nut, using standard contact to simulate the interaction among the bolt, the nut, and the disk mounting edge, and simulating the tightening torque of the bolt by applying an initial interference amount.

[0022] In some embodiments, setting the large deformation geometric nonlinear parameters includes: turning on the large deformation calculation switch during the solution and performing nonlinear iterative solution based on the finite deformation theory.

[0023] In some embodiments, setting the boundary constraints includes: setting a single-point axial constraint at the bearing position.

[0024] In some embodiments, setting the load steps includes: performing the solution using two load steps according to the actual installation sequence of the engine, namely: the first step, without applying the engine load, only considering the bolt tightening torque to obtain the mechanical state in the assembled state; the second step, applying centrifugal force, temperature field, pneumatic flow path pressure, cavity pressure, turbine axial force, and torque load to simulate the mechanical state in the actual working state of the engine.

[0025] In some embodiments, setting the parallel solution parameters includes: selecting the parallel computing mode and the number of parallel computing cores.

[0026] In some embodiments, analyzing the fracture margin of the aeroengine rotor system includes: calculating the fracture margin using the mean stress method , and its calculation formula is as follows:

[0027]

[0028] where is the correction coefficient, is the ultimate strength at the corresponding temperature, is the mean circumferential stress or the mean radial stress.

[0029] Based on the above technical solutions, the present invention has at least the following beneficial effects:

[0030] In some embodiments, the numerical evaluation method for the safety of the aeroengine rotor system utilizes the Fourier element and three-dimensional cyclic symmetry element technologies. While considering the fine details of the model, it significantly reduces the computational amount, improves the computational efficiency, shortens the iterative design cycle of the rotor system while obtaining more reliable analysis results, and improves the accuracy of the evaluation. Description of the Drawings

[0031] The accompanying drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0032] Figure 1 It is a schematic flow chart of a method for numerically evaluating the safety of an aero-engine rotor system provided according to some embodiments of the present invention;

[0033] Figure 2 It is a schematic diagram of a rotor system provided according to some embodiments of the present invention;

[0034] Figure 3 It is a schematic diagram of multi-point constraints provided according to some embodiments of the present invention. Detailed implementation manners

[0035] Next, the technical solutions in the embodiments will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0036] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the scope of protection of the present invention.

[0037] When performing safety assessment on an aero-engine rotor system, the numerical simulation method based on the finite element method has the characteristics of being fast, accurate, efficient and low-cost, and has become the most widely used method in addition to the test verification methods for components, test benches and whole machines, etc., and is also one of the main methods adopted in the strength design of aero-engines.

[0038] However, due to the extremely large computational amount and extremely long design cycle brought by the full three-dimensional numerical analysis, a large number of current studies are based on a simplified two-dimensional plane axisymmetric model. However, the simplified model does not consider the asymmetric holes, mounting grooves, counterweight blocks and other structures on the rotor, nor can it consider the stiffness anisotropy of the asymmetric holes and other structures, and at the same time, it cannot apply loads such as turbine shaft torque. The simplified model will bring differences between the simulation results such as stress and deformation and the actual results, which will further make the calculations of life, dimension chain, etc. inaccurate, thereby increasing the probability of stress failure, life problems and rubbing of the rotor.

[0039] Based on this, some embodiments of the present disclosure provide a numerical evaluation method for the safety of an aero-engine rotor system, which is used to alleviate the differences between simulation results and actual results and improve the accuracy of the safety evaluation of the rotor system.

[0040] In some embodiments, as Figure 1 shown, the numerical evaluation method for the safety of an aero-engine rotor system includes the following steps:

[0041] According to the three-dimensional structural characteristics of the aero-engine rotor system, the axisymmetric part and the non-axisymmetric part are distinguished. A Fourier element finite element model is established for the axisymmetric part, and a three-dimensional cyclic symmetric element finite element model is established for the non-axisymmetric part;

[0042] Coupling is formed between the Fourier element finite element model and the three-dimensional cyclic symmetric element finite element model by using the multi-point constraint algorithm to ensure the transfer of loads and the coordination of displacements and stresses between different element types;

[0043] Contact pairs are applied according to the actual contact positions between components in the rotor system, contact parameters are set, large deformation geometric nonlinear parameters are set, engine loads are applied and boundary constraints are set, load steps are set and parallel solution parameters are set, and parallel solution is carried out on a computer platform to obtain the numerical analysis results of the aero-engine rotor system; and

[0044] Based on the numerical analysis results of the aero-engine rotor system, the single-point stress of the aero-engine rotor system is analyzed, the life of the aero-engine rotor system is analyzed, and the rupture margin of the aero-engine rotor system is analyzed to complete the numerical safety evaluation of the aero-engine rotor system.

[0045] In some embodiments, the engine loads include centrifugal force, temperature field, pneumatic flow path, cavity pressure, turbine axial force, torque, etc.

[0046] The numerical evaluation method for the safety of the aero-engine rotor system provided by the embodiments of the present disclosure overcomes the risks brought by model simplification. By using Fourier element and three-dimensional cyclic symmetric element technologies, while considering the fine details of the model, the calculation amount is greatly reduced, the calculation efficiency is improved, and while obtaining more reliable analysis results, the iterative design cycle of the rotor system is shortened, providing a more scientific and reasonable basis and guidance for the numerical safety evaluation of the aero-engine rotor system.

[0047] In some embodiments, the numerical evaluation method for the safety of an aeroengine rotor system takes into account the anisotropic stiffness of holes and other non-axisymmetric features, avoiding the safety risks brought about by two-dimensional axisymmetric numerical analysis that ignores non-axisymmetric structures and cannot apply turbine shaft torque loads, and alleviating the problems of ultra-large computational volume and extremely long design cycle brought about by the full three-dimensional numerical analysis of the rotor system.

[0048] As Figure 1 shown, in some embodiments, the numerical evaluation method for the safety of an aeroengine rotor system adopts a parallel analysis process that takes into account strong nonlinear contact and large deformation geometric nonlinearity, which includes: designing the initial structural scheme of the aeroengine rotor; judging whether to conduct a safety evaluation, and if a safety evaluation is required, conducting a structural analysis and zoning of the rotor system; discretizing the model with different element types for different parts of the model according to the model characteristics; coupling at the discontinuous element interfaces by means of multi-point constraints to achieve the transfer of loads and the continuity of displacements and stresses, obtaining a continuous finite element analysis model; setting the nonlinear contact and large deformation parameters, loads, and boundary conditions; then performing solution and parallel mode settings; performing nonlinear parallel solution to obtain the numerical analysis results of the aeroengine rotor system, and further analyzing whether the single-point stress, life, and fracture margin of the aeroengine rotor system meet the design requirements according to the analysis results. If the requirements are met, the process ends; if the requirements are not met, the initial structural scheme of the aeroengine rotor system is optimized, and the safety of the aeroengine rotor system is numerically evaluated again.

[0049] Among them, before parallel solution, issues such as mesh convergence, material parameters varying with temperature, contact and large deformation parameters, loads, constraint boundaries, and parallel solution settings need to be considered.

[0050] In some embodiments, the numerical evaluation method for the safety of an aeroengine rotor system includes the following steps:

[0051] S10: As Figure 2 shown, according to the three-dimensional structural characteristics of the aeroengine rotor system, the axisymmetric part and the non-axisymmetric part are distinguished, and a Fourier element finite element model is established for the axisymmetric part, and a three-dimensional cyclic symmetric element finite element model is established for the non-axisymmetric part.

[0052] Optionally, the axisymmetric part adopts eight-node quadrilateral Fourier elements, and the number of circumferential Fourier nodes is set to twelve to reduce the computational volume while improving the calculation accuracy.

[0053] As Figure 2 shown, the non-axisymmetric part includes the rotor body, blades, test modification holes, mounting grooves, locking screw holes, drain holes, counterweight blocks, bolts, and nuts, etc.

[0054] For non-axisymmetric parts, a cyclic symmetric model is used to establish 20-node hexahedral elements. To ensure convergence, the element size and position are basically the same at the positions where contact may occur between components of the rotor system. To avoid excessive local stress, the meshes of the cyclic symmetric planes should be exactly the same. In some embodiments, the number of finite elements of the rotor model is about 1.2 million.

[0055] S20: Use the multi-point constraint algorithm to form a coupling between different types of elements established in step S10, namely Fourier elements and three-dimensional cyclic symmetric elements, to ensure the transfer of loads and the coordination of displacements and stresses between different element types.

[0056] The specific steps of the multi-point constraint algorithm include:

[0057] Select the connection surface of the cyclic symmetric element as the master surface, and select the contact surface of the Fourier element as the slave surface.

[0058] Establish the constraint relationship between each slave surface node and the master surface node, and the constraint relationship satisfies formula (1):

[0059]

[0060] Where, is the degree of freedom of the slave node, is the degree of freedom of the master node, is the weighting coefficient, is the number of nodes participating in the coupling, is the constant term.

[0061] As Figure 3 shown, it is a schematic diagram of the multi-point constraint algorithm. The coupling of different types of elements is realized through multi-point constraints between element type 1 and element type 2.

[0062] S30: Apply contact pairs according to the actual contact positions between components in the rotor system, set contact parameters, set large deformation geometric nonlinear parameters, apply engine loads such as centrifugal force, temperature field, pneumatic flow path pressure, cavity pressure, turbine axial force and torque, and set boundary constraints. Set load steps and parallel solution parameters, and perform parallel solution on the supercomputer platform to obtain the numerical analysis results of the engine rotor.

[0063] Among them, applying contact pairs according to the actual contact positions between components in the rotor system includes: using standard contact to simulate the interaction between the working surfaces of split blade tenons and the disk, using bonded contact to simulate the threaded action between bolts and nuts, using standard contact to simulate the interaction between bolts, nuts and the mounting edge of the disk, and simulating the tightening torque of the bolts by applying an initial interference. Optionally, the contact stiffness coefficient can be appropriately adjusted to improve the convergence efficiency, but it should not be less than 0.5.

[0064] The setting of large deformation geometric nonlinear parameters includes: turning on a large deformation calculation switch during solution, and performing nonlinear iterative solution based on finite deformation theory.

[0065] The setting of boundary constraints includes: setting a single-point axial constraint at the bearing position.

[0066] Setting the load step involves solving the problem using two load steps, based on the actual engine installation sequence. The first step involves applying no engine loads and only considering bolt tightening torque to determine the mechanical state of the assembly. The second step involves applying centrifugal force, temperature field, aerodynamic flow path pressure, cavity pressure, turbine axial force, and torque loads to simulate the actual engine operating state. Optionally, to avoid impact during the loading process and non-convergence of the calculation, all loads are slowly increased from zero to their final values at a specific slope.

[0067] The setting of the parallel solution parameters includes: selecting a parallel computing mode and a number of parallel computing cores. Optionally, the parallel computing mode is a distributed memory parallel mode, and the number of parallel computing cores is 64 cores.

[0068] Before solving the parameters of the Fourier unit finite element model in parallel, integrate the Fourier unit finite element model equation and set the number of circumferential Fourier nodes. , if the number of circumferential Fourier nodes is is an odd number, its shape function For formula (2), if the number of circumferential Fourier nodes is is an even number, its shape function Formula (3):

[0069]

[0070] (3)

[0071] in, u r is the radial node displacement in the cylindrical coordinate system is the circumferential node displacement in the cylindrical coordinate system, is the axial nodal displacement in the cylindrical coordinate system;

[0072] is the shape function of a general planar quadrilateral or triangular element, and is a variable;

[0073] 、 、 are the Fourier series coefficients.

[0074] S40: Analyze the single-point stress, life, and fracture margin of the aero-engine rotor system by using the numerical analysis results of the aero-engine rotor system obtained in step S30, and complete the numerical safety assessment of the aero-engine rotor system.

[0075] Among them, the single-point stress includes: the von mises yield criterion equivalent stress at all assessment positions.

[0076] The life includes: the low-cycle fatigue life considering the number of aircraft flight cycles.

[0077] Analyzing the fracture margin of the aero-engine rotor system includes: calculating the fracture margin by using the mean stress method , and its calculation formula is formula (4):

[0078] (4)

[0079] Among them, is the correction coefficient, is the ultimate strength at the corresponding temperature, is the mean circumferential stress or mean radial stress.

[0080] The numerical safety assessment method for the aero-engine rotor system provided by the embodiments of the present disclosure overcomes the risks brought by model simplification in the related art. By using the Fourier element and three-dimensional cyclic symmetry element technologies, while considering the fine details of the model, the calculation amount is greatly reduced, the calculation efficiency is improved, while obtaining more reliable analysis results, the iterative design cycle of the rotor system is shortened, and a more scientific and reasonable basis and guidance are provided for the numerical safety assessment of the aero-engine rotor and similar structures.

[0081] Those skilled in the art know that in addition to implementing the systems, devices, and their respective modules provided by the present invention in the form of pure computer-readable program codes, the method steps can be logically programmed to enable the systems, devices, and their respective modules provided by the present invention to be implemented in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers to implement the same program. Therefore, the systems, devices, and their respective modules provided by the present invention can be regarded as a kind of hardware component, and the modules included therein for implementing various programs can also be regarded as the structures within the hardware component; the modules for implementing various functions can also be regarded as either software programs for implementing the method or the structures within the hardware component.

[0082] Based on the above embodiments of the present invention, without explicit negation, the technical features of one embodiment can be beneficially combined with one or more other embodiments.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that it is still possible to modify the specific implementation manners of the present invention or perform equivalent replacements on some technical features; without departing from the spirit of the technical solutions of the present invention, they should all be covered within the scope of the technical solutions claimed by the present invention.

Claims

1. A numerical evaluation method for the safety of an aeroengine rotor system, characterized in that It includes the following steps: According to the three-dimensional structural characteristics of the aero-engine rotor system, distinguish the axisymmetric part and the non-axisymmetric part, establish a Fourier element finite element model for the axisymmetric part, and establish a three-dimensional cyclic symmetric element finite element model for the non-axisymmetric part; Use the multi-point constraint algorithm to form a coupling between the Fourier element finite element model and the three-dimensional cyclic symmetric element finite element model; Apply contact pairs according to the actual contact positions between components in the rotor system, set contact parameters, set large deformation geometric nonlinear parameters, apply engine loads and set boundary constraints, set load steps and set parallel solution parameters, and carry out parallel solution on the computer platform to obtain the numerical analysis results of the aero-engine rotor system; And Based on the numerical analysis results of the aero-engine rotor system, analyze the single-point stress of the aero-engine rotor system, analyze the life of the aero-engine rotor system, and analyze the rupture margin of the aero-engine rotor system to complete the numerical safety assessment of the aero-engine rotor system; Before parallel solving parameters of the finite element model of the Fourier element, integrate the equations of the finite element model of the Fourier element and set the number of circumferential Fourier nodes ; If the number of circumferential Fourier nodes is odd, the shape function of the finite element model of the Fourier element is as follows: If the number of circumferential Fourier nodes N is even, the shape function of the Fourier element finite element model is as follows: Among them, represents the shape function corresponds to three displacement components respectively. Among them, is the radial nodal displacement in the cylindrical coordinate system, is the circumferential nodal displacement, is the axial nodal displacement in the cylindrical coordinate system, is the shape function of a plane quadrilateral or triangular element, , , are the Fourier series coefficients; Establishing the three-dimensional cyclic symmetric element finite element model for the non-axisymmetric part includes: using the cyclic symmetric model to establish 20-node hexahedral elements, keeping the element size consistent at the positions where components in the rotor system come into contact, and keeping the meshes of the cyclic symmetric planes consistent.

2. The numerical evaluation method for the safety of an aeroengine rotor system according to claim 1, characterized in that, The forming of the coupling between the Fourier element finite element model and the three-dimensional cyclic symmetric element finite element model by using the multi-point constraint algorithm includes: Select the connection surface of the three-dimensional cyclic symmetric element finite element model as the master surface, and select the contact surface of the Fourier element finite element model as the slave surface; Establish the constraint relationship between each slave surface node and the master surface node, and the constraint relationship satisfies the following formula: Among them, is the degree of freedom of the slave node, is the degree of freedom of the master node, is the weighting coefficient, is the number of nodes participating in the coupling, is the constant term.

3. The numerical evaluation method for the safety of an aero-engine rotor system according to claim 1, characterized in that, Applying the contact pairs according to the actual contact positions between components in the rotor system includes: using standard contact to simulate the interaction between the working surface of the split blade tenon and the disk, using bonded contact to simulate the threaded action between the bolt and the nut, using standard contact to simulate the interaction between the bolt, the nut and the disk mounting edge, and simulating the tightening torque of the bolt by applying an initial interference amount.

4. The numerical evaluation method for the safety of an aero-engine rotor system according to claim 1, wherein Setting the large deformation geometric nonlinear parameters includes: turning on the large deformation calculation switch during the solution and performing nonlinear iterative solution based on the finite deformation theory.

5. The numerical evaluation method for the safety of an aero-engine rotor system according to claim 1, characterized in that, Setting the boundary constraints includes: setting single-point axial constraints at the bearing positions.

6. The numerical evaluation method for the safety of an aero-engine rotor system according to claim 1, characterized in that Setting the load steps includes: according to the actual installation sequence of the engine, using two load steps for the solution, which are respectively: the first step, without applying engine loads, only considering the bolt tightening torque to obtain the mechanical state in the assembled state; the second step, applying centrifugal force, temperature field, pneumatic flow path pressure, cavity pressure, turbine axial force and torque loads to simulate the mechanical state in the actual working state of the engine.

7. The numerical evaluation method for the safety of an aeroengine rotor system according to claim 1, wherein Setting the parallel solution parameters includes: selecting the parallel computing mode and the number of parallel computing cores.

8. The numerical evaluation method for the safety of an aero-engine rotor system according to claim 1, characterized in that, The calculation of the fracture margin of the analyzed aero-engine rotor system includes: calculating the fracture margin using the mean stress method , and its calculation formula is as follows: wherein, is the correction coefficient, is the ultimate strength at the corresponding temperature, is the average circumferential stress or the average radial stress.

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