Finite element simulation method for response of complex rotor rotating inertia excitation of aero-engine

Abstract

This invention belongs to the field of aero-engine simulation technology, specifically relating to a finite element simulation method for the rotational inertial excitation response of complex aero-engine rotors. Addressing the problem that existing methods cannot simulate the continuous increase in the supercritical rotor response, this invention establishes a finite element model of the rotor, divides the rotor into mass structural elements based on the bending deformation distribution during rotor operation, stiffens the finite element nodes of these mass structural elements and couples them to the central node, applies unbalanced forces and rotational inertial torques to the central node, and simulates the rotor's rotational inertial excitation response. This invention can simulate the influence of rotor bending deformation and principal axis tilt on the dynamic response, improving the prediction accuracy of the dynamic response of complex aero-engine rotors, especially the characteristic of continuously increasing rotor dynamic response under supercritical high speeds, providing simulation method support for the vibration control of aero-engine rotors and the entire engine.

Description

Technical Field

[0001] This invention belongs to the field of aero-engine simulation technology, specifically relating to a finite element simulation method for the rotational inertial excitation response of a complex rotor in aero-engine. Background Technology

[0002] The aero-engine rotor system is a complex, high-speed rotating structural system. The rotational inertial excitation caused by the asymmetry of the rotor's mass distribution relative to the rotation centerline is one of the main sources of vibration excitation in the engine. Rotor mass distribution asymmetry can be divided into lateral and angular directions. Lateral mass asymmetry is caused by the rotor's center of mass deviating from its centroid, and is usually described as the product of the eccentricity and the mass, i.e., the imbalance. Angular mass distribution asymmetry is caused by the tilt of the rotor's principal axis of inertia relative to the rotation centerline, and is usually expressed as the product of the tilt angle and the difference between the rotor's pole / diameter moment of inertia. During rotation, the rotor's mass distribution asymmetry will cause rotational inertial excitation. Specifically, the rotor imbalance causes unbalanced forces, while the tilt of the principal axis of inertia causes rotational inertial torques. During the operation of the aero-engine rotor, the rotor will be subjected to rotational inertial excitation due to its asymmetric mass distribution, which may lead to increased vibration of the rotor and the entire engine, causing structural damage to the rotor and load-bearing system, seriously affecting the independent development and field use of the aero-engine. Therefore, accurately simulating the rotational inertial excitation response of aero-engine rotors is of great significance for aero-engine rotor dynamics design and overall vibration control.

[0003] Existing finite element simulation methods for rotational inertia excitation response only consider the unbalanced force caused by rotor imbalance, neglecting the rotational inertial torque caused by the tilt of the rotor's principal axis. The typical procedure involves applying an unbalanced force to the rotor based on the remaining unbalance on the balance correction surface measured after low-speed dynamic balancing, and then simulating the rotor's dynamic response. The simulation results mostly show that the rotor's dynamic response only peaks at the critical speed, and decreases rapidly and remains at a low level after deviating from the critical speed.

[0004] However, with the continuous development of aero-engine technology, the rotor operating speed is constantly increasing, and the rotor bending deformation under operating conditions is becoming increasingly significant. The rotor dynamic response is more sensitive to the rotational inertial torque caused by the tilt of the principal axis of inertia. Test results of multiple aero-engines show that the rotor dynamic response not only has a peak at the critical speed, but also increases continuously with speed in the supercritical range far from the critical speed. Therefore, the simulation accuracy of the rotational inertial excitation response of aero-engine rotors using existing methods is low, making it difficult to meet the dynamic design requirements of aero-engine rotors and the entire engine.

[0005] In summary, existing finite element simulation methods for rotational inertial excitation response have the following limitations:

[0006] 1) Existing simulation methods only consider the rotor dynamic response caused by unbalanced forces, and do not consider the rotational inertial torque caused by the tilt of the rotor's inertial principal shaft. It is difficult to accurately simulate the rotor dynamic response, especially the trend of continuous increase in rotor dynamic response in the supercritical speed range.

[0007] 2) Most existing methods are based on simplified rotor models such as two degrees of freedom and beam elements. No suitable rotational inertial excitation simulation method for complex aero-engine rotors has been proposed. These methods cannot accurately describe the complex features of aero-engine rotors such as multi-stage wheel disks, disc-drum configurations, and connection structures, making it difficult to improve the prediction accuracy of rotational inertial excitation response simulation.

[0008] Therefore, there is an urgent need to propose a finite element simulation method for the rotational inertial excitation response of complex rotors in aero-engines. Summary of the Invention

[0009] To overcome the shortcomings of existing simulation methods that only consider unbalanced forces and do not take into account the influence of rotational inertial torque and bending deformation on rotor dynamic response, this invention proposes a finite element simulation method for the rotational inertial excitation response of complex rotors in aero-engines. This method can simultaneously simulate rotor unbalanced forces and rotational inertial torque, and correct the load application form according to rotor bending deformation. It is applicable to rotor systems with complex structural features in aero-engines and can improve the simulation accuracy of rotor dynamic response under operating conditions.

[0010] This invention is implemented by providing a finite element simulation method for the rotational inertial excitation response of a complex rotor in an aero-engine, comprising the following steps:

[0011] S1: Simplify the complex rotor structure of the aero-engine, draw the rotor finite element mesh, and assign material properties to each element of the rotor to obtain the rotor finite element model.

[0012] S2: Aero-engine rotors typically use ball bearings and roller bearings. Considering the small axial length of the bearing, its angular stiffness can be ignored. Therefore, in finite element simulation, only the lateral support stiffness at the bearing is retained, while its angular degrees of freedom are released. The specific method is as follows: Define a bearing center node at the geometric center of the bearing, and create a 6-DOF mass element on the bearing center node, including 3 translational degrees of freedom and 3 rotational degrees of freedom. Stiffen the finite element node at the bearing support point and associate the motion degrees of freedom of the finite element node at the bearing support point with the bearing center node. Then, create a spring element with one end fixed and the other end connected to the bearing center node. By setting the stiffness coefficient of the spring element, the support constraint at the bearing is simulated.

[0013] S3: Calculate the rotor resonant speed distribution characteristics, and for each resonant speed, solve for the corresponding rotor mode shape;

[0014] S4: Combining the rotor mode shape, the rotor is divided into mass structural elements and elastic structural elements. The mass structural elements are the main source of rotor rotational inertial excitation. When simulating the rotor rotational inertial excitation response, in order to avoid deformation distortion caused by the finite element load applied to local nodes, it is necessary to stiffen the finite element model of the mass structural elements to simulate its characteristic of not undergoing bending deformation in the above-mentioned speed range. The specific method is as follows: stiffen the finite element nodes of the mass structural elements and couple them to the center node of the mass structural elements. Also define a 6-DOF mass element on the center node of the mass structural elements. The center node of the mass structural elements will be used to apply rotational inertial excitation.

[0015] S5: Based on the measured or preset imbalance of the rotor Inclination of the principal axis of inertia A rotational inertial excitation is applied to the central node of each mass structural element. The rotor rotational inertial excitation response and unbalance are obtained through rotor dynamics simulation. Inclination of the principal axis of inertia middle, m For the mass of the structural unit, e Let be the eccentricity of the mass structural element. I d The moment of inertia of the diameter. I p The moment of inertia is the polar rotation. τ This represents the tilt of the principal axis of inertia of the mass structural unit.

[0016] Preferably, in S1: for complex rotors of aero-engines that require rotational inertial excitation response, the geometric features are simplified based on the rotor structure system diagram, and the material grade and mechanical performance parameter values ​​of each component of the rotor are determined, and the rotor finite element mesh is drawn.

[0017] Preferably, S3 specifically includes:

[0018] No excitation load is applied to the rotor finite element model processed by S2. The rotor resonant speed distribution characteristics are simulated using the matrix eigenvalue solving algorithm. Considering that the rotor rotation speed has a significant impact on the resonant speed, different rotation speeds are applied to the rotor within the range of 0 to 1.5 times the maximum operating speed of the rotor. The rotor resonant speeds at different rotation speeds are calculated. The maximum order of the resonant speed analysis is selected based on the fact that only one modal frequency exists that is higher than the maximum operating speed of the rotor. After obtaining the rotor resonant speed, the corresponding rotor mode shape is solved for each resonant speed for subsequent simulation analysis.

[0019] Preferably, in S4, the mass structural unit refers to a structural unit whose mass / moment of inertia accounts for more than 30% of the rotor and does not undergo bending deformation within the range of 0 to 1.5 times the maximum operating speed, and the elastic structural unit refers to a structural unit whose mass / moment of inertia accounts for less than 10% and undergoes bending deformation within the range of 0 to 1.5 times the maximum operating speed.

[0020] Preferably, in step S5, the rotational inertial excitation includes an unbalanced force. With rotational inertia torque ,in ω is the rotor's rotational angular velocity.

[0021] Preferably, in the specific application of the present invention, it is not required to use any specific finite element simulation software; any commercial finite element simulation software or self-written program can be used for simulation analysis.

[0022] Compared with the prior art, the advantages of the present invention are as follows:

[0023] This invention is applicable to rotor systems of aero-engines with complex structural features. By dividing the rotor into mass structural units and elastic structural units, it effectively characterizes the bending deformation distribution during rotor operation and its influence on the axial distribution of rotor rotational inertial excitation. By applying force and torque at the central node, it equivalently simulates rotor unbalanced force and rotational inertial torque, which can improve the prediction accuracy of the rotational inertial excitation response of complex aero-engine rotors. Attached Figure Description

[0024] To more clearly illustrate the technical solution proposed in this invention, the accompanying drawings are briefly described below. Obviously, the drawings described below are merely some specific embodiments of this invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0025] Figure 1 This is a flowchart of the finite element simulation method for the rotational inertial excitation response of complex rotors in aero-engines proposed in this invention;

[0026] Figure 2 This is a finite element model diagram of a complex rotor of an aero-engine in a specific embodiment of the present invention;

[0027] Figure 3 This is the present invention. Figure 2 Enlarged view of section 1 in the middle;

[0028] Figure 4These are the first three mode shape diagrams of the complex rotor of the aero-engine in a specific embodiment of the present invention, wherein (a) is the first mode shape diagram, (b) is the second mode shape diagram, and (c) is the third mode shape diagram;

[0029] Figure 5 This is a schematic diagram of the application of rotor rotational inertia excitation in a specific embodiment of the present invention;

[0030] Figure 6 This is a comparison chart of the simulation results and measured data of the rotor rotational inertia excitation response in a specific embodiment of the present invention.

[0031] In the figure: 1-front journal, 2-compressor rotor, 3-drum shaft, 4-turbine rotor, 5-rear journal, 6-finite element node at bearing support, 7-bearing center node, 8-compressor rotor center node, 9-turbine rotor center node. Detailed Implementation

[0032] To make the technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] like Figures 1-6 As shown, a finite element simulation method for the rotational inertial excitation response of a complex rotor in an aero-engine is presented. The complex rotor is a high-pressure rotor of a low-bypass turbofan engine, composed of a front journal 1, a compressor rotor 2, a drum shaft 3, a turbine rotor 4, and a rear journal 5. Both the compressor rotor 2 and the turbine rotor 4 exhibit centroid shift and principal axis tilt. In this specific embodiment, ANSYS simulation software is used to conduct the rotor rotational inertial excitation response simulation, which includes the following steps:

[0034] S1: Based on the high-pressure rotor structure design drawing, the geometry was simplified in ANSYS simulation software, including local small chamfers, tooth tips, and connection interfaces. The rotor blades were simplified into circumferentially continuous rings using the equivalent ring method, ensuring that the mass and polar rotational inertia were equal before and after simplification. The rotor finite element mesh was drawn using SOLID185 solid elements, as shown below. Figure 2 As shown. Based on the material grades of each rotor component, for example, the first three stage disks of compressor rotor 2 are made of titanium alloy, the last three stage disks and the grate disk are made of high-temperature alloy, and turbine rotor 4 is made of powder high-temperature alloy. Their density, elastic modulus and Poisson's ratio are assigned to the corresponding finite element elements to obtain the high-pressure rotor finite element model.

[0035] S2: The high-pressure rotor is a two-support straddle rotor, and displacement constraints need to be established at both the front and rear supports. The support stiffnesses are respectively... , In finite element simulation, it is necessary to perform stiffening operations on the finite element nodes at the front and rear support points, such as... Figure 3 As shown, the finite element node 6 at the bearing support point is selected as a component. A stiffened region is generated using the CERIG command in ANSYS simulation software and coupled to the bearing center node 7. A MASS21 mass element is defined on the bearing center node, with a mass of 1g and a moment of inertia of 1g. To avoid affecting the rotor mass distribution, a COMBI214 spring element is defined, with one end of the spring fixed and the other end connected to the bearing center node 7. The corresponding stiffness values ​​are assigned to KX and KY in the element properties. This establishes the displacement constraint of the rotor bearing support point and releases the angular constraint at the support point, avoiding the additional angular constraint caused by using the CP command.

[0036] S3: For the established finite element model of the high-pressure rotor, the resonant speed distribution was simulated using the MODAL simulation method in ANSYS software. Specifically, the QRDAMP algorithm was employed, and complex frequencies and complex modes were calculated. This was mainly because the gyroscopic torque effect of the high-pressure rotor was significant, and the gyroscopic torque matrix was the coefficient matrix of the first derivative in the dynamic equation, requiring complex mode calculation. The CORIOLIS command was used to enable the gyroscopic torque effect. The maximum operating speed of the high-pressure rotor was 14000 rpm; therefore, the analysis range of the rotor's rotational speed was set to 0~21000 rpm, with increments of 3000 rpm. Seven analysis points were selected within this speed range, and the OMEGA command was used to apply the rotor's rotational speed to perform resonant speed calculations and obtain the mode shapes. The results are as follows: Figure 4 As shown, the first two modes of the high-pressure rotor are rigid body translation and rigid body pitch, respectively. In these two modes, the rotor bending deformation can be ignored, and the modal frequencies are all lower than the maximum operating speed of the rotor in the range of 0~21000rpm. The third mode is the overall first-order bending, in which the rotor bends significantly, and the compressor rotor 2 and the turbine rotor 4 undergo relative angular deformation. Its modal frequency is higher than the maximum operating speed of the rotor.

[0037] S4: Based on the simulation results of the resonant speed of the high-pressure rotor within the speed range of 0~21000rpm, the high-pressure rotor is divided into structural units, such as... Figure 5As shown, since the compressor rotor 2 and turbine rotor 4 have large masses and moments of inertia, and approximately do not undergo bending deformation in the aforementioned mode shapes, the compressor rotor 2 and turbine rotor 4 are classified as mass structural elements, while the lighter and less stiff front journal 1, drum shaft 3, and rear journal 5 are classified as elastic structural elements. Since the element type of the high-pressure rotor finite element model is SOLID185, it only has 3 translational degrees of freedom and no rotational degrees of freedom. To facilitate the subsequent application of rotational inertia torque to the compressor rotor 2 and turbine rotor 4, the compressor rotor 2 and turbine rotor 4 are stiffened. The CERIG command is used to generate stiffened regions, which are coupled to the compressor rotor center node 8 and turbine rotor center node 9, and MASS21 mass elements are defined on them, with a mass of 1g and a moment of inertia of 1g. To avoid affecting the rotor mass distribution;

[0038] S5: Based on the measured data during the assembly / balancing process, apply rotational inertia excitation to the finite element model of the high-pressure rotor and complete the rotational inertia excitation response simulation: Based on the unbalance, coaxiality, end face runout, and other results obtained during the assembly / balancing process, the unbalance of compressor rotor 2 can be calculated. Inclination angle of principal axes of inertia Inclination of principal axis of inertia The imbalance of turbine rotor 4 Inclination angle of principal axes of inertia Inclination of principal axis of inertia Subsequently, the rotor rotational inertial excitation response simulation was carried out using the HARMIC module of ANSYS simulation software. The SYNCHRO command was used to set the rotor motion to synchronous positive precession, ensuring that the excitation on the rotor was proportional to the square of its rotational speed. The F command was used to apply an unbalanced force at the compressor rotor center node 8. With rotational inertia torque Similarly, the F command is used to apply an unbalanced force to the center node 9 of the turbine rotor. With rotational inertia torque The SOLVE command is used to solve for the rotor rotational inertial excitation response.

[0039] like Figure 6 As shown, the simulation results of the high-pressure rotor rotational inertia excitation response of a specific embodiment of the present invention are as follows. It can be seen that the existing method only considers the unbalanced force, and the rotor dynamic response in the supercritical range in the simulation results is maintained in a low range, which is significantly different from the measured results. However, the present invention considers the influence of both the unbalanced force and the rotational inertia torque on the dynamic response, which can improve the simulation accuracy of the measured results.

[0040] The specific embodiments described above are merely preferred embodiments of the present invention. It should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Without departing from the principles of the present invention, any modifications, alterations, substitutions, or replacements of the simulation object made by those skilled in the art to the technical solutions of the present invention, or any changes to the simulation object, should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A finite element simulation method for the rotational inertial excitation response of a complex rotor in an aero-engine, characterized in that, Includes the following steps: S1: Simplify the complex rotor structure of the aero-engine, draw the rotor finite element mesh, and assign material properties to each element of the rotor to obtain the rotor finite element model. S2: Define a bearing center node at the geometric center of the bearing, and establish a 6-DOF mass element on the bearing center node, including 3 translational degrees of freedom and 3 rotational degrees of freedom. Stiffen the finite element node at the bearing support point and associate the motion degrees of freedom of the finite element node at the bearing support point with the bearing center node. Then, establish a spring element with one end fixed and the other end connected to the bearing center node. By setting the stiffness coefficient of the spring element, simulate the support constraint at the bearing. S3: Calculate the rotor resonant speed distribution characteristics, and for each resonant speed, solve for the corresponding rotor mode shape; S4: Combining the rotor mode shape, the rotor is divided into mass structural elements and elastic structural elements. The finite element nodes of the mass structural elements are stiffened and coupled to the center node of the mass structural elements. A 6-DOF mass element is also defined on the center node of the mass structural elements. The center node of the mass structural elements will be used to apply rotational inertia excitation. S5: Based on the measured or preset unbalance and inertial shaft tilt of the rotor, apply rotational inertial excitation to the center node of each mass structural unit, and obtain the rotor rotational inertial excitation response through rotor dynamics simulation.

2. The finite element simulation method for the rotational inertia excitation response of a complex rotor in an aero-engine according to claim 1, characterized in that, In S1: For complex rotors of aero-engines that require rotational inertial excitation response, the geometric features are simplified based on the rotor structure system diagram, and the material grade and mechanical performance parameter values ​​of each component of the rotor are determined, and the rotor finite element mesh is drawn.

3. The finite element simulation method for the rotational inertia excitation response of a complex rotor in an aero-engine according to claim 1, characterized in that, Specifically, S3 is: No excitation load is applied to the rotor finite element model processed by S2. The rotor resonant speed distribution characteristics are simulated using the matrix eigenvalue solving algorithm. Different rotation speeds are applied to the rotor within the range of 0 to 1.5 times the maximum operating speed of the rotor. The rotor resonant speeds at different rotation speeds are calculated. The maximum order of the resonant speed analysis is selected based on the fact that only one modal frequency exists that is higher than the maximum operating speed of the rotor. After obtaining the rotor resonant speed, the corresponding rotor mode shape is solved for each resonant speed.

4. The finite element simulation method for the rotational inertia excitation response of a complex rotor in an aero-engine according to claim 1, characterized in that, In S4, a mass structural unit refers to a structural unit whose mass / moment of inertia accounts for more than 30% of the rotor and does not undergo bending deformation within the range of 0 to 1.5 times the maximum operating speed. An elastic structural unit refers to a structural unit whose mass / moment of inertia accounts for less than 10% and undergoes bending deformation within the range of 0 to 1.5 times the maximum operating speed.

5. The finite element simulation method for the rotational inertia excitation response of a complex rotor in an aero-engine according to claim 1, characterized in that, In S5, the rotational inertial excitation includes unbalanced force and rotational inertial torque.

Images