Method and system for improving engine rotor dynamics characteristics based on intermediate support point strain energy proportion

Abstract

This invention discloses a method and system for improving engine rotor dynamics characteristics based on the proportion of strain energy at the intermediate support point, belonging to the field of rotor dynamics design for aero-engines and gas turbines. The method includes: S1 establishing a coupled dual-rotor dynamics analysis model; S2 identifying the critical speed of high-low pressure coupled vibration excitation by the high-pressure rotor by ensuring that the proportion of strain energy at the intermediate support point is greater than a first preset threshold and the proportion of rotor strain energy is greater than a second preset threshold; S3 optimizing the rotor structure if the critical speed does not meet the speed margin criterion; and S4 setting an elastic support structure at the intermediate support point, adjusting the stiffness of the intermediate support point, and optimizing the strain energy proportion if the criterion still cannot be met. This invention can adjust the critical speed of high-low pressure coupled vibration to meet the margin requirements without changing the overall structural layout, and concentrate the strain energy on the intermediate elastic support, reducing the load on the intermediate bearing and achieving effective protection for it.

Description

Technical Field

[0001] This invention belongs to the field of rotor dynamics design for aero-engines and gas turbines, and relates to a method and system for improving rotor dynamics characteristics, specifically a method and system for improving engine rotor dynamics characteristics based on the proportion of strain energy at intermediate fulcrums. Background Technology

[0002] Rotor dynamics design of aero-engines is one of the core technologies in the overall design of aero-engines. The vibration characteristics of the rotor-support system are crucial for the high performance and reliability of aero-engines. Currently, to reduce weight, improve thrust-to-weight ratio, and make the engine structure more compact, most advanced aero-engines, both domestically and internationally, adopt a dual-rotor structure coupled through an intermediate support point. The rear support point of the high-pressure rotor is designed as an intermediate bearing, the front end of the high-pressure rotor is connected to the load-bearing casing via a thrust bearing, and the rear end is supported on the low-pressure shaft via an intermediate bearing. This design results in mutual coupling between the high-pressure and low-pressure rotors, making the vibration situation more complex. Therefore, the design technology of the critical speed of the high- and low-pressure coupled vibration type is a key technology in coupled dual-rotor dynamics design, and also one of the difficulties in coupled dual-rotor dynamics design.

[0003] Chinese patent CN116680804B discloses a critical speed design method for a dual-rotor system with intermediate bearings based on strain energy distribution. It proposes that the critical speed of the high-pressure rotor's excited coupled bending mode is often located near the maximum operating speed, making it extremely difficult to meet and improve the critical speed margin. This patent determines key influencing structural parameters through strain energy distribution and optimizes the critical speed distribution by adjusting these parameters, using the critical speed margin as a criterion for dynamic design. However, in the design of modern advanced high-thrust turbofan engines, due to significantly increased operating speeds and the adoption of a two-stage turbine design for the low-pressure turbine, the optimization methods in this patent, such as shortening the axial dimension, are not applicable. It is impossible to adjust the critical speed of the dual-rotor coupled bending mode to above the maximum operating speed with a 20% margin. Furthermore, when developing a complete engine from a mature core engine, the axial length of the high-pressure rotor is fixed, and the span between the second and third supports of the low-pressure rotor cannot be significantly shortened, failing to meet the speed margin requirements.

[0004] Chinese patent application CN115640717A points out that it is difficult to design an engine that meets the requirements by following the critical speed margin criterion. Therefore, a tolerant modal optimization design method for a dual-rotor system with intermediate bearings is proposed. However, for the actual engineering dual-rotor system with intermediate bearings, the modal tolerance of the critical speed of the coupled bending mode excited by the high-pressure rotor is very low. The proposed method is not applicable to the critical speed of the higher-order bending mode with coupling characteristics.

[0005] Therefore, there is an urgent need for a method and system for improving the dynamic characteristics of dual rotors in intermediate bearings with strong engineering practicality. Under the constraints that the axial length of the high-pressure rotor of a high-performance aero-engine cannot be shortened and the high-pressure speed cannot be reduced, the critical speed of high-low pressure coupled vibration should be adjusted to meet the speed margin requirements. Summary of the Invention

[0006] In view of this, the purpose of this invention is to address the limitations of existing technologies in adjusting the critical speed of high-pressure coupled vibration to meet speed margin requirements, given that the axial length of the high-pressure rotor in a high-performance aero-engine cannot be shortened and the high-pressure speed cannot be reduced. This invention proposes a method and system for improving the dynamic characteristics of the engine rotor based on the proportion of strain energy at the intermediate fulcrum. Without significantly altering the overall structural layout, this method rapidly iteratively optimizes and designs a rotor that meets the design requirements, thereby improving the dynamic characteristics of the coupled dual rotors.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for improving the dynamic characteristics of an engine rotor based on the proportion of strain energy at the intermediate pivot point, comprising the following steps: S1: Establish a coupled dual-rotor dynamic analysis model, take the stiffness of the intermediate bearing as the initial intermediate support stiffness, and perform dynamic calculations. S2: Identify the critical speed of high-low voltage coupled vibration excited by high-voltage rotor, and determine the critical speed of high-low voltage coupled vibration by calculating that the proportion of strain energy at the intermediate support point is greater than a first preset threshold and the proportion of strain energy at the rotor is greater than a second preset threshold. S3: If the critical speed does not meet the speed margin criterion, the critical speed of the high-low pressure coupled vibration is improved by optimizing the rotor structure. S4: If step S3 still fails to meet the speed margin criterion, then the rotor dynamic characteristics are improved by setting an elastic support structure at the intermediate support, adjusting the stiffness of the intermediate support, and optimizing the strain energy ratio of the intermediate support.

[0009] Further, step S4 includes the following sub-steps: S41: Add an intermediate elastic support structure at the intermediate fulcrum, wherein the stiffness adjustment range of the intermediate elastic support is 1×10. 7 N / m~5×10 7 N / m; S42: Plot the curve of the critical speed of high-low pressure coupled vibration as a function of the stiffness of the intermediate support. S43: In the curve, the upper limit of the intermediate support stiffness is determined based on the critical speed of high-low voltage coupled vibration being below idle speed and the 20% speed margin point. ; S44: Determine the lower limit of the stiffness of the intermediate support point based on the flexural deformation of the intermediate support point, the limiting clearance of the intermediate elastic support, and the strength of the intermediate elastic support. ; S45: Within the range of the upper limit and lower limit of the intermediate support stiffness, the strain energy ratio of the intermediate support is optimized by adjusting the stiffness of the intermediate elastic support.

[0010] Furthermore, in step S43, the upper limit of the stiffness of the intermediate support point is determined. The specific method is as follows: In the critical speed-stiffness variation curve, draw a straight line perpendicular to the vertical axis at the point where the speed margin is 20% below the idle speed. This straight line intersects the critical speed-intermediate support stiffness curve. The stiffness value on the horizontal axis corresponding to the intersection point is the upper limit of the intermediate support stiffness. .

[0011] Further, in step S44, the lower limit of the stiffness of the intermediate support is determined by matching the flexural deformation of the intermediate support, the limiting gap of the intermediate elastic support, and the strength of the intermediate elastic support. Specifically, this is solved by simultaneously solving the following formulas:

[0012]

[0013]

[0014]

[0015] in, For the limiting gap of the intermediate elastic support, Deflection at the intermediate fulcrum For the lateral force load at the intermediate fulcrum, E The elastic modulus of the intermediate elastic support. For the high-voltage rotor mass, It is the acceleration due to gravity. This is the axial distance between the centroid of the high-pressure rotor and the first support point of the high-pressure rotor. This is the axial distance between the center of mass of the high-pressure rotor and the intermediate support point. For the length of the intermediate elastic support cage bar, For the diameter of the intermediate elastic support bar, For the maximum stress of the intermediate elastic cage bar, Allowable vibration stress.

[0016] Furthermore, in step S45, the stiffness of the intermediate fulcrum is modeled as the stiffness K of the intermediate bearing. 中介轴承 With intermediate elastic stiffness K 中介弹支 In a series system, the total stiffness K at the intermediate fulcrum 中介支点 Calculate using the following formula:

[0017] The strain energy proportion E of the intermediate bearing and the intermediate spring support were calculated separately. 中介轴承 and E 中介弹支 The proportion of strain energy at the intermediate fulcrum E 中介支点 Calculate using the following formula:

[0018] By adjusting the stiffness of the intermediate support, the strain energy ratio of the intermediate bearing is made to satisfy: E 中介轴承 ≤0.2E 中介支点 In addition, the axial position of the intermediate support point is adjusted so that the axial position of the intermediate support point is close to the vibration node of the low-pressure rotor, so as to reduce the proportion of strain energy of the intermediate support point.

[0019] Furthermore, the strain energy proportion of the intermediate bearing .

[0020] Furthermore, the rotor structure optimization in step S3 includes: shortening the axial length of the high-pressure rotor, increasing the inner and outer diameters of the low-pressure turbine shaft, and increasing the ratio of the polar rotational inertia to the diametrical rotational inertia of the high-pressure compressor rotor.

[0021] Furthermore, the speed margin in step S2 is calculated using the following formula:

[0022] If the speed margin is ≥20%, no optimization is needed; otherwise, proceed to step S3 or S4.

[0023] Furthermore, the intermediate elastic support is a rotational elastic support structure, including cage bars or tie rods, and the stiffness of the intermediate support point can be adjusted by adjusting the number, length and diameter of the cage bars or tie rods.

[0024] Secondly, the present invention provides an engine rotor dynamics characteristic improvement system based on the proportion of strain energy at intermediate fulcrums, for implementing the above method, comprising: A low-pressure rotor and a high-pressure rotor, wherein the high-pressure rotor is supported on the low-pressure rotor by an intermediate fulcrum; The intermediate support includes an intermediate bearing and an intermediate spring support, which are connected in series to form an intermediate support structure with adjustable stiffness. The intermediate elastic support is an elastic support structure with a stiffness adjustment range of 1×10. 7 N / m~5×10 7 N / m, by adjusting the stiffness of the intermediate support, the strain energy ratio of the intermediate support point is optimized, so that the strain energy ratio of the intermediate bearing satisfies E 中介轴承 ≤0.2E 中介支点 .

[0025] Compared with the prior art, the present invention has at least the following beneficial effects: This invention addresses the design and optimization of the stiffness of the intermediate support point by adding an intermediate spring support structure. This, in turn, optimizes the proportion of strain energy at the intermediate support point and the intermediate bearing, solving the design problem of critical speeds for dual-rotor high-low pressure coupled vibration that cannot be addressed in existing technologies. It improves the dynamic characteristics of the critical speed of dual-rotor high-low pressure coupled vibration while essentially preserving the dynamic characteristics of other critical speeds and maintaining minimal changes to the overall engine structural layout. By concentrating the strain energy of the intermediate support point onto the intermediate spring support, the proportion of strain energy in the intermediate bearing is reduced, thereby reducing the load on the intermediate bearing and protecting it. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the coupled dual-rotor system structure in an embodiment of the present invention; Figure 2 This is a detailed structural diagram of the low-pressure rotor and the high-pressure rotor in an embodiment of the present invention; Figure 3 This is a flowchart of the method for improving engine rotor dynamics characteristics based on the proportion of strain energy at intermediate fulcrum, according to an embodiment of the present invention. Figure 4 This is a schematic diagram of the critical speeds of the high-voltage rotor excitation in an embodiment of the present invention; Figure 5 This is a schematic diagram of the intermediate rotating spring support structure in an embodiment of the present invention; Figure 6 This is a graph showing the variation of the critical rotational speed of high-low pressure coupled vibration with the stiffness of the intermediate support in an embodiment of the present invention. Figure 7 This is a schematic diagram of the intermediate support point series stiffness model in an embodiment of the present invention.

[0028] In the diagram: 1-Low-pressure rotor, 2-High-pressure rotor, 3-Intermediate pivot, 4-Low-pressure first pivot, 5-Fan front journal, 6-Fan assembly, 7-Fan rear journal, 8-Low-pressure second pivot, 9-Low-pressure turbine shaft, 10-Intermediate spring support, 11-Low-pressure turbine assembly, 12-Low-pressure third pivot, 13-High-pressure first pivot, 14-High-pressure compressor front journal, 15-High-pressure compressor assembly, 16-High-pressure compressor rear journal, 17-High-pressure turbine front journal, 18-High-pressure turbine assembly, 19-High-pressure turbine rear journal, 20-Intermediate bearing, 21-Intermediate bearing inner ring, 22-Intermediate bearing outer ring, 23-Limiter. Detailed Implementation

[0029] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0030] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar words used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Words such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects.

[0032] Example 1 This embodiment details the specific implementation process of a method for improving engine rotor dynamics characteristics based on the proportion of strain energy at intermediate fulcrums. For example... Figure 3 As shown, the method mainly includes the following steps: S1: Establish a coupled dual-rotor dynamic analysis model like Figure 1As shown, the coupled dual-rotor system of this embodiment of the invention consists of a low-pressure rotor 1 and a high-pressure rotor 2. The high-pressure rotor 2 is supported on the low-pressure rotor 1 through an intermediate fulcrum 3, and the high-pressure rotor 2 and the low-pressure rotor 1 rotate in opposite directions.

[0033] like Figure 2 As shown, the low-pressure rotor 1 mainly includes: a fan front journal 5, a fan assembly 6, a fan rear journal 7, a low-pressure turbine shaft 9, a low-pressure turbine assembly 11, a low-pressure first support point 4, a low-pressure second support point 8, a low-pressure third support point 12, and an intermediate spring support 10. The high-pressure rotor 2 mainly includes: a high-pressure compressor front journal 14, a high-pressure compressor assembly 15, a high-pressure compressor rear journal 16, a high-pressure turbine front journal 17, a high-pressure turbine assembly 18, a high-pressure turbine rear journal 19, and a high-pressure first support point 13.

[0034] Based on the two-dimensional geometric model of the aforementioned dual-rotor structure, a coupled dual-rotor dynamic analysis model is established using commercial finite element method software or transfer matrix method software. The initial intermediate support stiffness is taken as the stiffness value of the intermediate bearing itself, with the intermediate bearing stiffness ranging from 1.9 × 10⁻⁶. 8 N / m~2.5×10 8 N / m. Dynamic calculations were performed on the coupled dual-rotor structure to be optimized.

[0035] S2: Identify the critical speed of high-low voltage coupled vibration under high voltage rotor excitation. Through the dynamic calculations in step S1, the critical speeds of each order of high-pressure rotor excitation are calculated, such as... Figure 4 As shown. The proportion of strain energy at the intermediate pivot point and the proportion of strain energy in the rotor are calculated for each critical speed mode. If the proportion of strain energy at the intermediate pivot point is greater than a first preset threshold and the proportion of strain energy in the rotor is greater than a second preset threshold, then the critical speed of that mode is determined to be the critical speed of the high-low pressure coupled vibration. This step sets the criteria of the proportion of strain energy at the intermediate pivot point being greater than the first preset threshold and the proportion of strain energy in the rotor being greater than the second preset threshold, which can accurately identify the critical speed of the high-low pressure coupled vibration excited by the high-voltage rotor, providing a precise target for subsequent optimization.

[0036] In this embodiment, the first preset threshold is specifically set to 20%, and the second preset threshold is specifically set to 25%. This empirical value can effectively distinguish the coupled vibration mode from other modes. That is, when the proportion of strain energy at the intermediate fulcrum is greater than 20% and the proportion of strain energy at the rotor is greater than 25%, the critical speed is identified as the critical speed of high-low voltage coupled vibration excited by the high-voltage rotor.

[0037] Whether optimization is needed is determined according to the speed margin criterion. The speed margin is calculated according to formula (1): ………(1) If the critical speed of this order has exceeded the highest steady-state operating speed and has a speed margin of 20% (i.e., speed margin ≥ 20%), then the critical speed of the high-low voltage coupled vibration is considered not to need optimization. Further, the rotor dynamics design is completed according to the critical speed margin and strain energy requirements. If the critical speed margin of the high-low voltage coupled vibration is insufficient (i.e., speed margin < 20%), then optimization is performed through step S3.

[0038] S3: Rotor Structure Optimization By optimizing the rotor structure, the critical speed of this high-low pressure coupled vibration can be increased, thereby improving the critical speed margin of the high-low pressure coupled vibration and ensuring that it meets the speed margin condition. Rotor structure optimization methods include: shortening the axial length of the high-pressure rotor, increasing the inner and outer diameters of the low-pressure turbine shaft, and increasing the ratio of the pole moment of inertia to the diametrical moment of inertia of the high-pressure compressor rotor.

[0039] If the critical speed of the high-low voltage coupled vibration is made to meet the speed margin criterion (i.e., speed margin ≥ 20%) through the above rotor structure optimization method, then the rotor dynamic characteristics optimization is completed. If the critical speed of the high-low voltage coupled vibration cannot be adjusted to a speed other than the highest steady-state speed and has a speed margin of 20% through step S3, then proceed to step S4 to improve the dynamic characteristics.

[0040] S4: A method for improving the critical speed of high-low pressure coupled vibration based on the proportion of strain energy at intermediate fulcrum. Step S4 specifically includes the following sub-steps: S41: Add intermediate elastic support structure at intermediate fulcrum. This embodiment provides an intermediate rotating spring support structure, such as... Figure 5 As shown, the intermediate fulcrum 3 includes an intermediate bearing 20 and an intermediate spring support 10, with the intermediate spring support 10 being an elastic support structure. The intermediate bearing 20 and the intermediate spring support 10 are connected in series to form an intermediate elastic support structure with adjustable stiffness. Specifically, as shown... Figure 5 As shown, the intermediate bearing 20 includes an inner ring 21 and an outer ring 22. The inner ring 21 is connected to the rear journal 19 of the high-pressure turbine. The intermediate spring support 10 is in the form of cage bars or tie rods, and the intermediate bearing 20 is connected to the intermediate spring support 10 via the outer ring 22. A limiter 23 is provided above the intermediate spring support 10, and the intermediate spring support 10 and the limiter 23 are fixedly mounted on the low-pressure turbine shaft 9. The outer ring 22 of the intermediate bearing integrates a mounting edge, which allows it to be assembled with the intermediate spring support 10. The stiffness of the intermediate support point can be adjusted by changing the number, length, and diameter of the cage bars or tie rods of the intermediate spring support 10. The stiffness adjustment range of the intermediate spring support 10 is 1×10⁻⁶. 7 N / m~5×10 7 N / m, its stiffness is much lower than that of the intermediate bearing itself (1.9×10 N / m). 8 N / m~2.5×108 (N / m), which allows the total stiffness of the intermediate support to be effectively adjusted by the elastic support, while ensuring structural strength and service life.

[0041] S42: Plot the critical rotational speed of high-low pressure coupled vibration as a function of the stiffness of the intermediate support. Rotor dynamics calculations were performed to determine the critical speed values ​​for high-voltage excitation and high-low-voltage coupled vibration under different intermediate support stiffnesses. The x-axis represents the intermediate support stiffness, and the y-axis represents the critical speed values ​​for high-low-voltage coupled vibration. The results are plotted as follows: Figure 6 The curve shown.

[0042] S43: Determine the upper limit of stiffness of intermediate fulcrum.

[0043] Determine the upper limit of the stiffness of the intermediate support point from the critical speed-stiffness variation curve. The specific method is as follows: Draw a straight line perpendicular to the vertical axis from the point 20% below the idle speed margin. This line intersects the critical speed-intermediate fulcrum stiffness curve. The stiffness value on the horizontal axis corresponding to the intersection point is the upper limit of the intermediate fulcrum stiffness. ,like Figure 6 As shown.

[0044] from Figure 6 It can be seen that the stiffness change of the intermediate support has little effect on the other critical speeds of the coupled dual rotor system. By adding an intermediate elastic support structure to the intermediate support, the critical speed of high and low pressure coupled vibration can be improved while basically not affecting the dynamic characteristics of other critical speeds, and the overall structural layout of the engine can be basically unchanged.

[0045] S44: Determine the lower limit of stiffness at intermediate fulcrums

[0046] The lower limit of the stiffness of the intermediate support is determined by matching the flexural deformation of the intermediate support, the limiting gap of the intermediate elastic support, and the strength of the intermediate elastic support.

[0047] Specifically, the flexural deformation at the intermediate fulcrum The calculation formula is as follows:

[0048] The flexural deformation is magnified by 1.2 times to obtain the limiting gap Y of the intermediate elastic support, which is calculated according to formula (2): ……………(2) in, The lateral force load at the intermediate support point can be obtained through finite element analysis or approximated by equation (3): ……………(3) Simplifying the intermediate elastic support into a force model, assuming one end of the cage bar is fixed and the other end only undergoes radial displacement without rotation, according to mechanics of materials, the maximum stress of the cage bar of the intermediate elastic support is calculated according to equation (4). This maximum stress should be less than the allowable vibration stress. : ……………(4) By combining equations (2), (3), and (4), the lower limit of the stiffness of the intermediate support can be obtained. The calculation formula (5): …………(5) In the above formulas: The limiting gap for the intermediate spring support; The intermediate fulcrum is used for flexural deformation; Transverse force load at the intermediate fulcrum; E The elastic modulus of the intermediate elastic support; For the mass of the high-voltage rotor; It is the acceleration due to gravity; This is the axial distance between the centroid of the high-voltage rotor and the first support point of the high-voltage rotor. This is the axial distance between the centroid of the high-pressure rotor and the intermediate support point. The length of the intermediate elastic support cage bar (tie rod); The diameter of the intermediate elastic support cage bar (tie rod); The maximum stress of the intermediate elastic support cage bar; The allowable vibration stress can be obtained in engineering through the Goodman correction method.

[0049] By determining the upper and lower limits of the stiffness of the intermediate support point through steps S43 and S44 respectively, it is ensured that while improving the critical speed margin, excessive flexural deformation is not caused, and the strength of the spring support meets the requirements.

[0050] S45: Optimize the proportion of strain energy at intermediate fulcrum. In step S1, the intermediate support stiffness is decomposed into a series system of intermediate bearing stiffness and intermediate elastic support stiffness, such as... Figure 7 As shown, the intermediate bearing 20 between the low-pressure rotor 1 and the high-pressure rotor 2 has a stiffness of K. 中介轴承 The stiffness of the intermediate elastic support 10 is K. 中介弹支 The total stiffness K of the intermediate fulcrum 中介支点 Calculate according to formula (6): ……………(6) The strain energy ratio of the intermediate support is the sum of that of the intermediate bearing and the intermediate elastic support, as shown in equation (7): ……………(7) Then, based on the dynamic calculation method used in step S1, the strain energy proportion E of the intermediate bearing can be calculated separately. 中介轴承 The proportion of intermediate elastic strain energy E 中介弹支 .

[0051] Within the upper and lower limits of the intermediate support stiffness determined in steps S43 and S44, the stiffness of the intermediate spring support is adjusted to achieve a reasonable distribution of the strain energy ratio between the intermediate bearing and the intermediate spring support. The final optimization objective is to make the strain energy ratio of the intermediate bearing satisfy equation (8): E 中介轴承 ≤0.2E 中介支点 ……………(8) At this point, the strain energy of the intermediate support is mainly concentrated on the intermediate spring support, while the strain energy of the intermediate bearing accounts for a relatively low proportion, thus protecting the intermediate bearing. In a further preferred embodiment, by finely adjusting the stiffness of the intermediate spring support, the proportion of strain energy in the intermediate bearing can be made to reach... At this point, the intermediate bearing is almost unloaded, providing the best protection and significantly extending its lifespan.

[0052] Furthermore, slightly adjusting the axial position of the intermediate support point, bringing it as close as possible to the vibration node of the low-pressure rotor, can further reduce the proportion of strain energy E at the intermediate support point. 中介支点 It can work synergistically with stiffness adjustment to achieve a synergistic optimization effect.

[0053] The test results show that by setting an intermediate spring support at the intermediate support point and controlling the stiffness and strain energy ratio of the intermediate support point, the steady-state and transient vibrations of the engine do not exceed the limits when the rotor passes the critical speed of high-low pressure coupled vibration, and the rotor dynamic characteristics are greatly improved.

[0054] By combining the rotor structure optimization in step S3 with the intermediate spring support adjustment in step S4, a progressive strategy of "first optimizing the structure, then adjusting the spring support" is formed. This strategy not only makes full use of conventional optimization methods, but also provides solutions for situations where the margin requirements cannot be met, thereby improving the success rate of the design.

[0055] Example 2 This embodiment describes in detail the specific structure of the engine rotor dynamics characteristic improvement system based on the proportion of strain energy at intermediate fulcrum, which is used to implement the method described in Embodiment 1.

[0056] like Figure 1 , Figure 2 , Figure 5 and Figure 7 As shown, the system includes: A low-pressure rotor 1 and a high-pressure rotor 2 are provided, with the high-pressure rotor 2 supported on the low-pressure rotor 1 via an intermediate support point 3. The intermediate support point 3 includes an intermediate bearing 20 and an intermediate spring support 10, which are connected in series to form an intermediate support structure with adjustable stiffness. Figure 7 As shown.

[0057] The intermediate elastic support 10 is an elastic support structure. For example... Figure 5 In one specific implementation shown, the intermediate spring support 10 includes cage bars or tie rods. The stiffness of the intermediate spring support 10 can be adjusted by changing the number, length, and diameter of the cage bars or tie rods. The stiffness adjustment range of the intermediate spring support 10 is 1×10⁻⁶. 7 N / m~5×10 7 N / m.

[0058] By adjusting the stiffness of the intermediate spring support 10, the strain energy ratio of the intermediate support point 3 is optimized, so that the strain energy ratio of the intermediate bearing 20 satisfies E. 中介轴承 ≤0.2E 中介支点 In a preferred embodiment, by carefully designing the structural parameters of the intermediate spring support 10, the strain energy ratio of the intermediate bearing 20 can be made to reach [a certain percentage]. .

[0059] Furthermore, the axial position of the intermediate support point 3 is set close to the vibration node of the low-pressure rotor 1 to reduce the proportion of strain energy of the intermediate support point 3.

[0060] The structure and connections of other components included in the system have been described in Embodiment 1 and will not be repeated here.

[0061] The system described in this embodiment of the invention achieves the design and optimization of the stiffness of the intermediate support point by setting an intermediate spring support at the intermediate support point, thereby optimizing the proportion of strain energy at the intermediate support point and the proportion of strain energy in the intermediate bearing. This can improve the dynamic characteristics of the critical speed of the dual rotor high-low pressure coupled vibration, while basically not affecting the dynamic characteristics of other order critical speeds, and also basically not changing the overall structural layout of the engine. Furthermore, by concentrating the strain energy of the intermediate support point on the intermediate spring support, the load on the intermediate bearing is reduced, thus protecting the intermediate bearing.

[0062] Comparative example: To verify the technical effects of the present invention, the following comparative experiments were conducted: Taking a certain type of aero-engine with a dual rotor structure as the object, the following three schemes are used for dynamic design: Comparative Example 1: Using existing technologies (such as patent CN116680804 B), the critical speed is adjusted only by structural optimizations such as shortening the axial dimension.

[0063] Comparative Example 2: Only steps S1-S3 of the present invention are used, without setting intermediate spring supports.

[0064] Embodiment of the present invention: The complete method (steps S1-S4) and system of the present invention are adopted.

[0065] The experimental results are shown in Table 1 below: Table 1

[0066] The results show that, using the method and system described in the embodiments of the present invention, the critical speed of high-low pressure coupled vibration was successfully adjusted to above the highest steady-state speed with a margin of more than 20%, while significantly reducing the strain energy ratio of the intermediate bearing (from 35% to 4%), meeting the requirements. This concentrates the strain energy onto the intermediate spring support, effectively protecting the intermediate bearing and significantly improving the overall vibration level of the machine.

[0067] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, various modifications and variations can be made to the embodiments of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for improving engine rotor dynamic characteristics based on the proportion of strain energy at intermediate fulcrum, characterized in that, Includes the following steps: S1: Establish a coupled dual-rotor dynamic analysis model, take the stiffness of the intermediate bearing as the initial intermediate support stiffness, and perform dynamic calculations. S2: Identify the critical speed of high-low voltage coupled vibration excited by high-voltage rotor, and determine the critical speed of high-low voltage coupled vibration by calculating that the proportion of strain energy at the intermediate support point is greater than a first preset threshold and the proportion of strain energy at the rotor is greater than a second preset threshold. S3: If the critical speed does not meet the speed margin criterion, the critical speed of the high-low pressure coupled vibration is improved by optimizing the rotor structure. S4: If step S3 still fails to meet the speed margin criterion, then by setting an elastic support structure at the intermediate support, adjusting the stiffness of the intermediate support, and optimizing the proportion of strain energy at the intermediate support, the rotor dynamic characteristics can be improved. Step S4 includes the following sub-steps: S41: Add an intermediate elastic support structure at the intermediate fulcrum, wherein the stiffness adjustment range of the intermediate elastic support is 1×10. 7 N / m~5×10 7 N / m; S42: Plot the curve of the critical speed of high-low pressure coupled vibration as a function of the stiffness of the intermediate support. S43: In the curve, the upper limit of the intermediate support stiffness is determined based on the critical speed of high and low voltage coupled vibration being below idle speed and with a 20% speed margin. ; S44: Determine the lower limit of the stiffness of the intermediate support point based on the flexural deformation of the intermediate support point, the limiting clearance of the intermediate elastic support, and the strength of the intermediate elastic support. ; S45: Within the range of the upper limit and lower limit of the intermediate support stiffness, the strain energy ratio of the intermediate support is optimized by adjusting the stiffness of the intermediate elastic support.

2. The method according to claim 1, characterized in that, In step S43, the upper limit of the stiffness of the intermediate support point is determined. The specific method is as follows: In the critical speed-stiffness variation curve, draw a straight line perpendicular to the vertical axis at the point where the speed margin is 20% below the idle speed. This straight line intersects the critical speed-intermediate support stiffness curve. The stiffness value on the horizontal axis corresponding to the intersection point is the upper limit of the intermediate support stiffness. .

3. The method according to claim 1, characterized in that, In step S44, the lower limit of the stiffness of the intermediate support is determined by matching the bending deformation of the intermediate support, the limiting gap of the intermediate elastic support, and the strength of the intermediate elastic support. Specifically, this is solved by simultaneously solving the following formulas: in, For the limiting gap of the intermediate elastic support, Deflection at the intermediate fulcrum For the lateral force load at the intermediate fulcrum, E The elastic modulus of the intermediate elastic support. For the high-voltage rotor mass, It is the acceleration due to gravity. This is the axial distance between the centroid of the high-pressure rotor and the first support point of the high-pressure rotor. This is the axial distance between the center of mass of the high-pressure rotor and the intermediate support point. For the length of the intermediate elastic support cage bar, For the diameter of the intermediate elastic support bar, For the maximum stress of the intermediate elastic cage bar, Allowable vibration stress.

4. The method according to claim 1, characterized in that, In step S45, the stiffness of the intermediate support point is modeled as the stiffness K of the intermediate bearing. 中介轴承 With intermediate elastic stiffness K 中介弹支 In a series system, the total stiffness K at the intermediate fulcrum 中介支点 Calculate using the following formula: The strain energy proportion E of the intermediate bearing and the intermediate spring support were calculated separately. 中介轴承 and E 中介弹支 The proportion of strain energy at the intermediate fulcrum E 中介支点 Calculate using the following formula: By adjusting the stiffness of the intermediate support, the strain energy ratio of the intermediate bearing is made to satisfy: E 中介轴承 ≤0.2E 中介支点 In addition, the axial position of the intermediate support point is adjusted so that the axial position of the intermediate support point is close to the vibration node of the low-pressure rotor, so as to reduce the proportion of strain energy of the intermediate support point.

5. The method according to claim 4, characterized in that, The strain energy percentage of the intermediate bearing .

6. The method according to claim 1, characterized in that, The rotor structure optimization in step S3 includes: shortening the axial length of the high-pressure rotor, increasing the inner and outer diameters of the low-pressure turbine shaft, and increasing the ratio of the polar rotational inertia to the diametrical rotational inertia of the high-pressure compressor rotor.

7. The method according to claim 1, characterized in that, The speed margin in step S2 is calculated using the following formula: If the speed margin is ≥20%, no optimization is needed; otherwise, proceed to step S3 or S4.

8. The method according to claim 1, characterized in that, The intermediate support is a rotational elastic support structure, including cage bars or tie rods. The stiffness of the intermediate support point can be adjusted by adjusting the number, length, and diameter of the cage bars or tie rods.

9. A system for improving engine rotor dynamic characteristics based on the proportion of strain energy at intermediate fulcrums, used to implement the method as described in any one of claims 1-8, characterized in that, include: A low-pressure rotor (1) and a high-pressure rotor (2), wherein the high-pressure rotor (2) is supported on the low-pressure rotor (1) by an intermediate fulcrum (3); The intermediate support (3) includes an intermediate bearing (20) and an intermediate spring support (10). The intermediate bearing (20) and the intermediate spring support (10) are connected in series to form an intermediate support structure with adjustable stiffness. The intermediate elastic support (10) is an elastic support structure with a stiffness adjustment range of 1×10. 7 N / m~5×10 7 N / m, by adjusting the stiffness of the intermediate spring support (10), the strain energy ratio of the intermediate support point (3) is optimized, so that the strain energy ratio of the intermediate bearing (20) satisfies E 中介轴承 ≤0.2E 中介支点 .

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