Optimization design method for multi-pivot elastic ring supporting structure of aero-engine rotor system

Abstract

The application relates to a kind of aero-engine rotor system multi-support point elastic ring supporting structure optimization design method, belong to aero-engine vibration control and rotor dynamics simulation technical field.First, the coupling dynamics equation of rotor and elastic ring is established by using finite element or lumped element model, considering elastic ring inner and outer oil film and orifice flow and other fluid-structure coupling factors;Then, through critical speed and vibration harmonic response analysis, the stiffness and damping characteristics of different supporting positions are evaluated, and the target vibration reduction mode corresponding to each support point is identified;Subsequently, around the number of elastic ring boss, boss height, damping hole diameter, thin wall thickness and other key structural parameters, coupling simulation and multi-objective optimization are carried out, and the optimal design meeting the vibration reduction requirements of rotor system and the strength reliability requirements of elastic ring is obtained by iteration;Finally, the optimization results are applied to structure manufacturing and assembly.The method can effectively reduce the vibration amplitude of rotor when crossing multiple critical speeds.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aero-engine vibration control and rotor dynamics simulation, and particularly relates to a multi-pivot elastic ring supporting structure optimization design method for aero-engine rotor systems. BACKGROUND

[0002] The high-speed flexible rotor-supporting structure system of an advanced aero-engine usually has the characteristics of high rotation speed, large load, multi-pivot supporting, and spanning multiple critical rotation speeds, and complex vibration response characteristics appear in the working process. Due to the differences in the vibration mode and motion characteristics of the rotor under different orders of critical state, if only a spring damping structure is used at a single supporting position, it is often difficult to effectively suppress the vibration response of each order. To realize safe spanning of multiple critical rotation speeds, corresponding spring damping devices need to be respectively arranged at different supporting positions, and the natural frequency of the system is adjusted and the vibration energy is effectively dissipated by the motion of the supporting points by optimizing the supporting stiffness and damping parameters, so that the rotor resonance avoids the working rotation speed or smoothly passes through the critical rotation speed.

[0003] The elastic ring squeeze film damper (ERSFD) is a new type of spring damping structure developed on the basis of the traditional squeeze film damper. It is mainly composed of a thin-walled elastic ring with inner and outer bosses and damping holes, and a flowing oil film in the ring gap. In the working process, the precession motion of the rotor causes elastic-plastic deformation of the elastic ring, which in turn squeezes the oil film in the ring and forces it to flow, and the supporting force and damping effect are provided by the oil film pressure and ring stiffness. The ERSFD can adjust the rotor critical rotation speed within a certain range and significantly reduce the vibration amplitude, and its structure is compact and light in weight, and is suitable for high-speed rotor systems of various sizes.

[0004] However, the stiffness and damping characteristics of the ERSFD are influenced by the coupling of multiple factors such as the geometry of the elastic ring, material properties, assembly, and oil film flow state, and there are complex interactions between the factors. Changes in the structural parameters of the elastic ring not only affect its own static mechanical properties, but also change the oil film flow characteristics, thereby having a coupled effect on the dynamic characteristics of the system. Therefore, to fully exploit the vibration control advantages of the ERSFD in high-speed flexible rotor systems of aero-engines, it is necessary to optimize the design of the geometry, material, assembly method, and oil film parameters of the elastic ring around the actual deformation and motion characteristics of the rotor. At present, there is still a lack of a systematic design theory and method for the elastic ring, making it difficult to accurately grasp key issues such as the fatigue life, stiffness measurement, and assembly precision of the ERSFD, which poses challenges to its specific application in rotor systems of aero-engines. Therefore, it is necessary to establish a systematic design process based on fluid-structure coupling and dynamic optimization to provide feasible theoretical and technical support for the engineering application of the ERSFD in high-speed flexible rotor-support systems. SUMMARY

[0005] The present application is directed to the design and optimization of an elastic ring squeeze film damper (ERSFD) support system for a multi-pivot flexible rotor system, and proposes a multi-pivot elastic ring support structure optimization design method for aero-engine rotor systems that can comprehensively consider critical speed, vibration response, and damping characteristics. This method fully considers the dynamic response characteristics of the rotor system, combines dynamic modeling, sensitivity evaluation, and structural parameter optimization, and can effectively improve the vibration control capability of the rotor system when crossing multiple orders of critical speed, and ensure long-term reliable performance.

[0006] To achieve the above-mentioned application purposes, the aero-engine rotor system multi-pivot elastic ring support structure optimization design method proposed by the present application adopts the technical scheme of:

[0007] An aero-engine rotor system multi-pivot elastic ring support structure optimization design method, the method comprises:

[0008] Step S1: establishing a coupled dynamics model of the rotor-support system; performing dynamic modeling of the rotor, performing finite element modeling of the elastic ring, establishing the inner and outer oil film fluid domains of the elastic ring and the oil film coupling equation to represent the oil film pressure distribution and orifice flow rate; coupling the rotor and the elastic ring to form a coupled dynamics equation of the rotor-support system;

[0009] Step S2: sensitivity evaluation of critical speed to support stiffness; based on the coupled dynamics model, solving the eigenvalue problem of the rotor to obtain the critical speed; through analysis of the critical speed and the working speed safety margin under different support stiffness, determining the reasonable range of the support stiffness of the different pivot elastic rings;

[0010] Step S3: Evaluate the sensitivity of the rotor response to the damping coefficient; change the damping coefficient of the elastic ring and evaluate the vibration amplitude of the rotor in each critical speed region under different damping coefficients; determine the target vibration reduction speed range of the elastic ring at different support points based on the sensitivity of the modal response of different support points to each critical speed region;

[0011] Step S4: Analyzing the influence of elastic ring structural parameters: Based on the geometric characteristics and material properties of the elastic ring, extract the elastic ring structural parameters and analyze their influence on the elastic ring support stiffness and damping coefficient; combining the critical speed and vibration response requirements of the rotor, screen the elastic ring structural parameter range that meets the target support stiffness and damping coefficient requirements;

[0012] Step S5: Iteratively optimize the elastic ring structural parameters; use the elastic ring structural parameter range as the optimization variable, and minimize the rotor vibration amplitude and the strength and durability of the elastic ring as the optimization goals; calculate the vibration response of each structural parameter at different speeds until the target vibration reduction effect and structural reliability requirements are met, and obtain the optimal structural parameter combination.

[0013] Compared with the traditional method of solving the Reynolds equation for obtaining the mechanical characteristic parameters of the elastic ring oil film, the present invention has the following beneficial effects:

[0014] (1) The present invention takes into account the rotor motion and deformation characteristics during optimization, and fully considers the rotor working characteristics and response characteristics to carry out structural design based on the mechanical properties of the elastic ring.

[0015] (2) This method determines the target vibration reduction modal characteristics and speed corresponding to the elastic ring supports at different positions through sensitivity evaluation, so that the vibration reduction structure design can be carried out for the rotor working characteristics of aircraft engines with multi-order criticality and a wide operating speed range. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 This is a schematic diagram of the structural features of an aircraft engine rotor-support system in an embodiment;

[0018] Figure 2 This is a schematic diagram of an elastic ring support structure in an embodiment;

[0019] Figure 3This is a flow chart of the optimization design method for the multi-point elastic ring support structure of the aircraft engine rotor system;

[0020] Figure 4 is the relationship between the critical speed of the rotor-support system and the elastic ring support stiffness;

[0021] Figure 5 This is a comparison chart of the effect of different elastic ring support damping on reducing the rotor response amplitude at different critical speed orders;

[0022] Figure 6 is the relationship between the elastic ring support stiffness and the number of bosses;

[0023] Figure 7 This is a diagram showing the influence of oil film clearance or boss height on oil film damping characteristics;

[0024] Figure 8 This is a diagram showing the influence of damping aperture on oil film damping characteristics. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] The present invention proposes a method for optimizing the design of a multi-point elastic ring support structure for an aero-engine rotor system, and the technical solution adopted is:

[0028] Step S1, establish a coupled dynamic model of the rotor-support system. The elastic ring squeeze film damper is aimed at the vibration reduction of the high-speed flexible rotor system, so the design of the elastic ring should not be limited to itself, but should revolve around the optimization design process of the dynamic response characteristics of the rotor-support system. Therefore, first of all, it is necessary to establish a rotor-elastic ring support deformation coupled dynamic model based on the high-speed rotor structural characteristics and the elastic ring support structural characteristics. When modeling the rotor, the finite element method, transfer matrix method or lumped unit model method is usually used to model the rotor and its supporting structure. For example, when establishing a lumped unit model, the establishment of the rotor's dynamic equation is based on the Lagrangian equation method, and the generalized coordinate equation of the rotor is obtained based on the second-kind Lagrangian equation, which is recorded as:

[0029] ,

[0030] where, is the rotor model mass matrix, is the elastic ring model mass matrix, T is the kinetic energy of the rotor, U is the potential energy of the rotor, D represents the damping dissipation energy of the system, q is the generalized coordinate, is the applied force. For high speed flexible rotor, the flexural deformation of the rotor and its influence on the displacement and angle at the support need to be explicitly considered, and the finite element discretization of solid elements or shell elements is used to obtain the rotor mass matrix M r , stiffness matrix K r , gyro matrix G r and internal damping matrix C r .

[0031] For the elastic ring, a thin-walled shell element theory is used to establish a finite element model. In the polar coordinate system, the stiffness and mass matrices of the elastic ring body are obtained by integrating the Jacobian matrix, the strain-displacement matrix and the material property matrix , . For the oil film of the elastic ring, the oil film fluid domain and its coupling equation are established. The inner and outer oil films are formed between the inner and outer rings of the elastic ring and between the outer side of the elastic ring and the bearing shell, respectively, and a number of through holes are arranged on the elastic ring to allow oil to flow between the cavities. According to the inner oil film Reynolds equation:

[0032] ,

[0033] where, is the radial deformation of the elastic ring, is the wall radial velocity, is the radius of the elastic ring, is the cylindrical angular coordinate, is the elastic axial coordinate, is the time parameter, represents the inner oil film thickness (considering factors such as rotor eccentricity, elastic ring deformation and angular deflection), is the inner oil film pressure, μ is the viscosity coefficient, is the eddy velocity. The outer oil film Reynolds equation is:

[0034] ,

[0035] where, is the outer oil film pressure, represents the outer oil film thickness.

[0036] The distribution is determined by the deformation of the elastic ring, rotor eccentricity, angular deflection, etc. μ is the oil viscosity. If the elastic ring has multiple bosses, the chambers are correspondingly divided into multiple circumferential segments; the orifices arranged on the elastic ring serve as passages between adjacent chambers, and the orifice flow rate is calculated by the Hagen-Poiseuille equation:

[0037] ,

[0038] wherein, is the flow rate, is the aperture, is the axial length of the aperture, is the pressure difference between the two ends of the aperture, is the length of the aperture, and the pressure field distribution of the inner and outer oil films and the orifice flow rate distribution are obtained by iteratively solving the orifice flow rate conservation condition and the oil film pressure. In the coupling calculation, the explicit step-by-step solution is mainly used, and the rotor-support deformation characteristics are obtained by converging multiple iterations at each time, and the oil film thickness is corrected according to the new deformation of the elastic ring, and the pressure distribution is solved by the oil film equation and the orifice flow equation, and the oil film force is updated and the elastic ring model is mapped. If the maximum change of the oil film force coefficient or the pressure distribution in the adjacent two iterations is less than the preset threshold, it is considered to be converged. Since the elastic ring and the rotor only contact in the boss area of the half-angle (θ π ) bearing the main radial force, the half-angle contact surface can be divided separately, and the other half-angle is regarded as a free boundary, so as to be closer to the actual working condition.

[0039] The coupling of the deformation of the elastic ring and the oil film flow can be expressed as:

[0040] ,

[0041] wherein, is the generalized coordinate, is the elastic ring excitation force, the rotor and the elastic ring are combined to obtain the coupling dynamics equation of the entire rotor-support system, which is denoted as:

[0042] ,

[0043] wherein, is the generalized coordinate of the rotor equation, , are the damping coefficients of the rotor and the elastic ring, , are cross-term dampings, , are the stiffness matrices of the rotor and the elastic ring, , Both are cross terms stiffness, the excitation term on the right side of the equation includes the oil film force with unbalance force etc. If only the intrinsic influence of the oil film force is concerned, the unbalance excitation can be temporarily ignored to simplify the study of the oil film mechanical properties of the elastic ring.

[0044] Step S2, sensitivity evaluation of critical speed to support stiffness. In this step, the law of the critical speed changing with the support stiffness of the elastic ring is mainly evaluated, and the influence of the stiffness of each support point on the vibration response of the system is evaluated. This step ignores the oil film force and the oil film equation, and the critical speed curve of the rotor system under different support stiffness is obtained by changing the stiffness parameters of the rotor support system. Based on the dynamic model of the rotor-support system established in step S1, the critical speed is calculated by using modal analysis, and the influence of the support stiffness on the critical speed is evaluated by calculating the margin of the working speed (i.e. safety margin).

[0045] The calculation of the critical speed can be obtained by solving the eigenvalue problem of the rotor system:

[0046] ,

[0047] where det is the determinant for solving the matrix, λ is the eigenvalue, which represents the square of the critical speed, and are the stiffness matrix and mass matrix of the rotor. At the same time, the sensitivity analysis of the response of the rotor system is also needed. By simulating the response of the rotor under different support stiffness, the vibration amplitude near the critical speed is evaluated, and the safety margin of the rotor system is evaluated according to the relationship between the working speed and the critical speed. Finally, based on the safety margin, the appropriate support stiffness value of the elastic ring is determined according to the working speed of the engine rotor.

[0048] Step S3, sensitivity evaluation of rotor response to damping coefficient. This step is to evaluate the sensitivity of the elastic ring damping characteristics, and to analyze the influence of different damping coefficients on the vibration response of the rotor system. Specifically, based on the dynamic model of the rotor-support system established in S1, the harmonic response of the rotor-support system is solved by applying an unbalanced excitation force to the disc position in the model, and the change of the response amplitude of the rotor system under different damping coefficients is evaluated by changing a series of different damping coefficients of the elastic ring, and the effect of damping on vibration suppression is analyzed combined with the vibration response in the critical speed region. Methodologically, by changing the damping coefficient of the elastic ring support (such as the oil film damping coefficient, the material damping of the elastic ring itself, etc.), the change of the vibration amplitude of the rotor and the critical speed under different damping coefficients is calculated. For different damping coefficients, the change of the response can be represented by the following formula:

[0049] ,

[0050] where ξ is the damping ratio, ω n ω is the natural frequency, x x is the displacement, F F is the external excitation force. By calculating the vibration response of the rotor system under different damping conditions, it is determined that the damping coefficient of the elastic ring at different positions is more sensitive to the modal response suppression under a certain order critical, so as to determine the vibration reduction target speed corresponding to the elastic ring at different positions, so as to realize effective vibration suppression.

[0051] Step S4, analysis of the influence law of the elastic ring structure parameters. By analyzing the structure characteristics of the elastic ring, the structure characteristics are extracted, including the number of bosses, boss height, thin wall thickness, damping hole diameter, axial length, boss matching relationship, ring diameter and other factors, a number of sensitive parameters are extracted, and a series of change ranges are set. Numerical analysis of the influence law of mechanical properties is carried out, and the influence law of structure parameters on the mechanical properties of the elastic ring support is obtained.

[0052] Step S5, iterative optimization of elastic ring structure parameters. In the optimization design process, an iterative optimization method is used, combined with a multi-objective optimization algorithm (such as genetic algorithm or particle swarm optimization algorithm) to optimize the structure parameters of the elastic ring. The goal is to minimize the vibration amplitude of the rotor and ensure the strength and durability of the elastic ring. The optimization objective function can be defined as the weighted sum of the vibration amplitude of the rotor and the damping characteristic function, and the parameter optimization is carried out through the genetic algorithm or particle swarm algorithm. Update the structure parameters of the elastic ring (such as the number of bosses, damping hole diameter, etc.) in each iteration until the optimization goal is reached.

[0053] Based on the above optimization and iteration of design parameters, the structure design and processing of the elastic ring are carried out, and the elastic squeeze-film damper structure for multi-pivot flexible rotor systems is obtained.

[0054] In order to clearly explain the technical features of the present application, the present application will be further described in detail below through specific embodiments, and in conjunction with the accompanying drawings. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0055] In order to further verify and illustrate the multi-pivot elastic ring support structure optimization design method for the rotor system of the aero-engine, a model of the elastic ring support-rotor system is taken as a representative example, and dynamic numerical solution and result comparison analysis are carried out. The structure diagram of the elastic ring support-rotor system is as follows Figure 1As shown, in structural composition, it includes the first fulcrum 1, the second fulcrum 2, the third fulcrum 4, the fourth fulcrum 5, the shaft 3 and the turbine assembly 6, wherein the elastic ring is arranged on the third fulcrum 4 and the fourth fulcrum 5, the rotor length is 130 mm, the turbine assembly mass is 63 kg, and the material elastic modulus is 195 GPa; the elastic ring structure is as shown in Figure 2 As shown, wherein the elastic ring is provided with an elastic ring boss 7 and a damping hole 8, in the design working state, the gap between the elastic ring and the matching surface is filled with lubricating oil, so that the lubricating oil can flow through the damping hole during the process of the elastic ring being deformed by the rotor extrusion, and flow damping is generated to inhibit and dissipate vibration energy, in structure, the elastic ring axial length is 21 mm, the material elastic modulus is 205 GPa, the ring thin wall thickness is 1 mm, the damping hole diameter is 0.8 mm, the ring diameter is 80 mm, the boss height is 0.2 mm, and the boss number is 8.

[0056] Step S1, as shown in Figure 3 The embodiment first simplifies the three-dimensional geometry of the rotor in the CAD software according to the overall structural characteristics of the engine power turbine rotor, removes the local small chamfer and non-key boss, and only retains the main shaft and disc drum structure which has a decisive role on the overall bending stiffness and mass distribution. Then the rotor is discretized into solid / beam / shell elements by using finite element software (such as ANSYS, ABAQUS or NASTRAN, etc.), and the mass matrix M r , the stiffness matrix K r , the gyro matrix G r and the internal damping matrix C r are obtained, so that the flexible bending and gyro effect under high-speed rotation can be accurately reflected in subsequent analysis. At the same time, the elastic ring is modeled by using thin-walled shell elements, and the specific method is as follows: first, according to the geometric definition of the elastic ring, four-node or eight-node shell elements are selected as the discrete base element, and the shape function, Jacobian matrix and strain-displacement matrix of the shell element are established in the polar coordinate system. In the "oil film mechanical property analysis" stage concerned in the embodiment, F the unbalance force of the rotor is not considered at present, so as to focus on the intrinsic influence of the elastic ring-oil film on the vibration characteristics; if the real running condition needs to be evaluated in the future, the unbalance force term can also be integrated into the equation for comprehensive calculation. For the oil film of the elastic ring, the oil film fluid domain and its coupling equation are established, the gap between the inner wall of the elastic ring and the outer surface of the rotor is defined as the inner oil film area, the gap between the outer wall of the elastic ring and the casing or bearing shell is defined as the outer oil film area, and a plurality of oil film chambers are formed by encapsulating in the end face seal or boss area. According to the Reynolds equation of the inner oil film:

[0057] ,

[0058] where, is the radial deformation of the elastic ring, is the radial velocity of the wall surface, is the radius of the elastic ring, is the cylindrical angular coordinate, is the axial coordinate of the elastic ring, is the time variable, represents the inner oil film thickness (considering the rotor eccentricity, elastic ring deformation, and angular deflection, etc.), is the inner oil film pressure, μ is the viscosity coefficient, is the whirl velocity. The outer oil film Reynolds equation:

[0059] ,

[0060] where, is the outer oil film pressure, represents the outer oil film thickness. Its distribution is determined together with the elastic ring deformation, rotor eccentricity, angular deflection, etc. μ is the oil viscosity. If the elastic ring has multiple bosses, the cavities are correspondingly divided into multiple circumferential segments; the orifices arranged on the elastic ring serve as passages between adjacent cavities, and the Hagen-Poiseuille equation is used to describe the relationship between the orifice diameter d and the pressure difference Δ

[0061] ,

[0062] where, is the flow rate, is the orifice diameter, is the axial length along the orifice, is the orifice length, is the orifice pressure difference, to depict the relationship between the orifice diameter d and the pressure difference Δ p and the flow rate Q . The flow conservation condition is set at each orifice to link the oil film pressures of the cavities. In this way, the fluid domain equations of the inner and outer oil films and the orifices are coupled on a discrete level, laying a foundation for subsequent iterative solution of the oil film forces.

[0063] Step S2, sensitivity evaluation of the critical speed to the elastic ring support stiffness. In this step, the law of the critical speed changing with the elastic ring support stiffness, and the influence of the support stiffness of each support point on the system vibration response are mainly evaluated. The oil film force and the oil film equation are ignored in this step, and the critical speed curve of the rotor under different support stiffnesses is obtained by changing the support stiffness of the elastic ring. On the basis of the rotor-support coupling model established in step S1, the critical speed is calculated using modal analysis, and the influence of the elastic ring support stiffness on the critical speed is evaluated by calculating the margin of the working speed (i.e., the safety margin).

[0064] The calculation of the critical speed can be obtained by solving the eigenvalue problem of the rotor:

[0065] ,

[0066] where det denotes the determinant function, λ is the eigenvalue, and K r is the square of the critical speed, M r is the stiffness matrix and mass matrix of the rotor. It is necessary to carry out sensitivity evaluation and analysis of the critical speed of the rotor system to the elastic ring support stiffness, and to take the critical speed distribution and its relative working speed safety margin as the core, according to the critical speed distribution-support stiffness characteristics, combined with the working speed (working speed, maximum speed, slow speed, etc.), the sensitivity analysis of the critical speed to the support stiffness of the rotor multi-support point is carried out, and the support stiffness range of the elastic ring is selected to meet the requirements of the critical speed and strain energy distribution design criteria. The example takes the elastic ring of the 4th support point of the rotor in Figure 1 as the object, and carries out sensitivity evaluation of the critical speed distribution, as shown in Figure 4 , wherein the stiffness of the 4th support point is set to 0.7×10 7 N / m. According to the sensitivity analysis results, in order to ensure the safety margin of the working critical speed of the rotor, the support stiffness interval of the elastic ring of the 3rd support point 4 is selected as 0.5~1×10 7 N / m, and the stiffness of the 4th support point 5 is kept as 0.7×10 7 N / m.

[0067] Step S3, sensitivity evaluation of the rotor response to the damping coefficient. This step carries out sensitivity evaluation of the damping characteristics of the elastic ring, and analyzes the influence of different damping coefficients on the vibration response of the rotor. Specifically, based on the rotor-support coupling model established in S1, the unbalanced excitation force is applied to the disc position of the model, the dynamic harmonic response of the rotor-support system is solved, and the change of the rotor system response amplitude under different damping conditions is evaluated by changing a series of different elastic ring support damping ratios, and the effect of damping on vibration suppression is analyzed combined with the vibration response in the critical speed region. On the method, the damping coefficient of the elastic ring support (such as oil film damping coefficient, material damping of the elastic ring itself, etc.) can be changed, and the change of the vibration amplitude and the critical speed of the rotor system under different damping conditions can be calculated. For different damping coefficients, the change of the harmonic response can be represented by the following formula:

[0068] ,

[0069] where ξ is the damping ratio, ω n is the natural frequency,x is the system displacement, F is the external excitation force. By calculating the vibration response of the rotor under different damping conditions, it is determined that the elastic ring support damping at different positions is more sensitive to the modal response suppression under a certain order critical, thereby determining the vibration reduction target speed corresponding to the elastic ring at different positions to achieve effective vibration suppression. In this embodiment, based on the rotor-support system model established in step S1, the same support damping coefficient is set for the elastic rings at the 3rd and 4th support points 4 and 5, and three groups of rotor-support system dynamic harmonic response analysis are carried out, including no damping, only the 3rd support point 4 has damping, and only the 4th support point 5 has damping. The response amplitudes at the positions of the first turbine disc and the second turbine disc are taken, normalized and compared with the influence of the elastic ring at different positions on the rotor response amplitude, as shown in Figure 5 . It can be seen that in this embodiment, the elastic ring damping at the 3rd support point 4 position is more effective in reducing the 2nd order critical speed, and the elastic ring damping at the 4th support point 5 position is more effective in reducing the 1st order critical speed. Therefore, in this embodiment, the 3rd support point 4 targets the 2nd order critical speed for vibration reduction, and the 4th support point 5 targets the 1st order critical speed for vibration reduction.

[0070] Step S4, analysis of the influence law of the elastic ring structure parameters. After the stiffness range of the elastic ring and the target vibration reduction speed are determined, the working mechanism of the elastic ring needs to be further studied. The structural characteristic parameters are extracted through structural analysis, stress and deformation characteristic analysis, etc. In this part, a finite element model reflecting the characteristics of the elastic ring-oil film needs to be established. For example, the number of elastic ring bosses is the main influencing parameter of the support stiffness of the elastic ring. By studying the influence of the number of elastic ring bosses on the support stiffness, the support stiffness corresponding to the best critical speed distribution obtained by the rotor-support system analysis is taken as the target value to determine the number of elastic ring bosses, as shown in Figure 6 . Since the axial length and radial size of the elastic ring are basically determined after the overall scheme of the engine is designed, the axial length and elastic ring diameter parameters are not modified in this embodiment. Since the damping mainly plays a vibration absorption and energy dissipation role when the rotor-support system passes through the critical speed, the best damping performance at the design critical speed is taken as the target to establish the fluid-structure coupling model in step S1. By changing the excitation frequency, the simulation analysis of the mechanical properties of the elastic ring-oil film and the influence law of the number of bosses, oil film gap (boss height), damping hole diameter, boss transition roundness, etc. are carried out, as shown in Figure 7 and Figure 8 .

[0071] Step S5, iteration optimization of elastic ring structure parameters. In the optimization design process, an iteration optimization method is adopted, combined with a multi-objective optimization algorithm (such as a genetic algorithm or a particle swarm optimization algorithm), to optimize the elastic ring structure parameters. The goal is to minimize the vibration amplitude of the rotor system and ensure the strength and durability of the elastic ring. The optimization objective function can be defined as the weighted sum of the vibration amplitude of the rotor system and the damping characteristic function, and the parameter optimization is performed through the genetic algorithm or the particle swarm algorithm. The structure parameters of the elastic ring (such as the number of bosses, the damping hole diameter, etc.) are updated in each iteration until the optimization goal is reached. The optimization range of the number of bosses is 6-12, the dimensionless oil film gap is 0.1-2.5%, the optimization range of the damping hole diameter is 0-2 mm, the boss transition fillet is 1-10 mm, the target vibration reduction critical speed is 7350 r / min, and the elastic ring stiffness is close to the target design stiffness when the number of bosses is 8 Figure 6 ); by designing the boss height to be 0.2 mm, the dimensionless oil film gap is 0.25%, so that the elastic ring can deform sufficiently and achieve a larger oil film damping effect Figure 7 ); when the damping hole diameter is 0.4 mm, the elastic ring support damping reaches a maximum value Figure 8 ).

[0072] Obtain the elastic ring structure design. Based on the above optimization iteration design parameters, the elastic ring structure design and processing are carried out, and the elastic squeeze-film damper structure for a multi-pivot flexible rotor system is obtained.

[0073] The above-described specific embodiments are only used to describe the preferred modes of the present application, and it should be understood that the protection scope of the present application is not limited to the specific embodiments. Without departing from the principles of the present application, those skilled in the art can make various modifications, changes, replacements, or replacement of simulation objects to the technical solutions of the present application, which should fall within the protection scope determined by the claims of the present application.

Claims

1. A method for optimizing the design of a multi-point elastic ring support structure for an aircraft engine rotor system, characterized in that: include: Step S1: establishing a coupled dynamic model of the rotor-support system; Conduct dynamic modeling of the rotor and finite element modeling of the elastic ring, establish the oil film fluid domain inside and outside the elastic ring and the oil film coupling equation, and characterize the oil film pressure distribution and orifice flow rate; The rotor is coupled with the elastic ring to form the coupled dynamic equation of the rotor-support system; Step S2: evaluating the sensitivity of critical speed to support stiffness; Based on the coupled dynamics model, the rotor's eigenvalue problem is solved to obtain the critical speed. By analyzing the critical speed and operating speed safety margin under different support stiffnesses, the reasonable range of support stiffness for elastic rings at different support points is determined. Step S3: Evaluate the sensitivity of the rotor response to the damping coefficient; change the damping coefficient of the elastic ring and evaluate the vibration amplitude of the rotor in each critical speed region under different damping coefficients; determine the target vibration reduction speed range of the elastic ring at different support points based on the sensitivity of the modal response of different support points to each critical speed region; Step S4: Analyzing the influence of elastic ring structural parameters: Based on the geometric characteristics and material properties of the elastic ring, extract the elastic ring structural parameters and analyze their influence on the elastic ring support stiffness and damping coefficient; combining the critical speed and vibration response requirements of the rotor, screen the elastic ring structural parameter range that meets the target support stiffness and damping coefficient requirements; Step S5: Iteratively optimize the elastic ring structural parameters; use the elastic ring structural parameter range as the optimization variable, and minimize the rotor vibration amplitude and the strength and durability of the elastic ring as the optimization goals; calculate the vibration response of each structural parameter at different speeds until the target vibration reduction effect and structural reliability requirements are met, and obtain the optimal structural parameter combination.

2. The method for optimizing the design of a multi-point elastic ring support structure for an aircraft engine rotor system according to claim 1, characterized in that: In step 1, the lumped element method is used to perform dynamic modeling of the rotor, including obtaining the generalized coordinate equation of the rotor based on the second-kind Lagrangian equation, which is expressed as: ， in, is the mass matrix of the rotor, is the mass matrix of the elastic ring, T is the kinetic energy of the rotor, U is the potential energy of the rotor, D represents the damping dissipation energy, q are generalized coordinates, is the applied force.

3. The method for optimizing the design of a multi-point elastic ring support structure for an aircraft engine rotor system according to claim 2, characterized in that: In step 1, the elastic ring is modeled by finite element using thin-walled shell elements, including: obtaining the stiffness matrix of the elastic ring by integrating the Jacobian matrix, strain-displacement matrix and material property matrix in the polar coordinate system With the mass matrix .

4. The method for optimizing the design of a multi-point elastic ring support structure for an aircraft engine rotor system according to claim 3, characterized in that: In step 1, the fluid domain equations of the inner and outer oil films of the elastic ring are established, including: the Reynolds equation of the inner oil film is: ， in, is the radial deformation of the elastic ring, is the radial velocity of the elastic ring wall, is the radius of the elastic ring, are cylindrical angular coordinates, is the axial coordinate of the elastic ring, is the time parameter, Indicates the inner oil film thickness, is the internal oil film pressure, μ is the viscosity coefficient, is the vortex velocity.

5. The method for optimizing the design of a multi-point elastic ring support structure for an aircraft engine rotor system according to claim 4, characterized in that: In step 1, the fluid domain equations of the inner and outer oil films of the elastic ring are established, including: the Reynolds equation of the outer oil film is: ， in, is the external oil film pressure, represents the thickness of the outer oil film, μ is the oil viscosity.

6. The method for optimizing the design of a multi-point elastic ring support structure for an aircraft engine rotor system according to claim 5, characterized in that: Furthermore, if the elastic ring has multiple bosses, the chamber is correspondingly divided into multiple circumferential segments; the orifices arranged on the elastic ring serve as channels between adjacent chambers, and the Hagen-Poiseuille equation is used: ， in, is the orifice flow rate, is the orifice diameter, is the axial length of the hole, is the orifice pressure difference, is the hole length, and the orifice flow conservation condition and the oil film pressure of the adjacent chamber are iteratively solved together to obtain the pressure field distribution of the inner and outer oil films and the orifice flow distribution; the dynamic equation of the elastic ring-oil film coupling is expressed as: ， in, is the generalized coordinate of the elastic ring, is the excitation force of the elastic ring. Combining the rotor and the elastic ring, the coupled dynamic equation of the rotor-support system is obtained, which is expressed as: ， in, are the generalized coordinates of the rotor, 、 are the damping coefficients of the rotor and elastic ring respectively, 、 are cross-term damping, 、 are the stiffness matrices of the rotor and elastic ring respectively, 、 are cross-term stiffnesses, 、 are the oil film force and the unbalanced force respectively.

7. The method for optimizing the design of a multi-point elastic ring support structure for an aircraft engine rotor system according to claim 1, characterized in that: In step S2, the critical speed is calculated by solving the eigenvalue problem of the rotor: ， Among them, det is used to find the determinant of the square matrix, λ is the characteristic value, which represents the square of the critical speed, Kr and Mr are the stiffness matrix and mass matrix of the rotor.

8. The method for optimizing the design of a multi-point elastic ring support structure for an aircraft engine rotor system according to claim 1, characterized in that: In step S3, the damping coefficient of the elastic ring is changed at different supporting points, the coupling effect of multiple supporting points on different-order critical vibration modes is evaluated, and the vibration reduction target speed and damping coefficient range of each supporting point are determined.

9. The method for optimizing the design of a multi-point elastic ring support structure for an aircraft engine rotor system according to claim 8, characterized in that: By changing the damping coefficient, the changes in the vibration amplitude and critical speed of the rotor under different damping coefficients are calculated. For different damping coefficients, the change in response is expressed by the following formula: ， in, is the damping ratio, is the natural frequency, is the displacement, F The vibration response of the rotor under different support damping coefficients is calculated by using the external excitation force. It is determined that the damping coefficient of the elastic ring at different supports is more sensitive to the modal response suppression under a certain critical order, thereby determining the vibration reduction target speed corresponding to the elastic ring at different supports.

10. The method for optimizing the design of a multi-support elastic ring support structure for an aircraft engine rotor system according to claim 1, characterized in that: The structural parameters in step S4 include: the number of bosses, boss height, thin wall thickness, damping aperture, axial length and ring diameter.

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