Vibration coupling suppression method for shared bearing frame-double-rotor system of aero-engine

Abstract

The invention belongs to the technical field of aero-engine complete machine vibration, and particularly relates to an aero-engine shared bearing frame-double rotor system vibration coupling suppression method which comprises the steps that structural parameters of a shared bearing frame-double rotor system of an aero-engine are input; establishing a finite element model, and calculating to obtain a Campbell graph; selecting a dangerous rotating speed point in the working rotating speed range, calculating the transient dynamic response of the shared bearing frame-birotor system, and judging whether the transient dynamic response meets the requirement or not; and carrying out optimization design on the dangerous rotating speed points which do not meet the requirements, and repeating the steps until the transient dynamic response of the dangerous rotating speed points of the shared bearing frame-birotor system in the working rotating speed range meets the requirements. According to the invention, the vibration coupling of the common bearing frame-double rotor system of the high thrust turbofan engine under complex working conditions is effectively suppressed, so that the aero-engine has a relatively stable working state within a working speed range.

Description

Technical Field

[0001] The invention belongs to the technical field of aircraft engine complete machine vibration, and in particular relates to a method for suppressing vibration coupling of an aircraft engine common load-bearing frame-dual rotor system. Background Art

[0002] In the overall structure of a high thrust-to-weight ratio turbofan engine, the use of a common load-bearing frame, especially a common load-bearing frame between turbine stages, can reduce the total number of load-bearing frames, effectively shorten the axial size of the engine, and reduce the engine mass. Therefore, the use of a common load-bearing frame between turbine stages has become a relatively common structural layout design scheme for aircraft engines. However, due to the large radial size variation of the common load-bearing frame between turbine stages, the limited axial space, and the complex load environment of multiple rotors and multiple pivots, there are serious vibration coupling problems in terms of dynamic response. The structural and dynamic design of the common load-bearing frame-dual rotor system faces severe challenges.

[0003] The vibration coupling suppression problem of the common load-bearing frame-dual rotor system is the key technical difficulty in the design of the common load-bearing frame structure layout between turbine stages of high thrust-to-weight ratio turbofan engines. However, there is still a gap in the research on the independent design of the dynamic characteristics of the common load-bearing frame in my country, and there is a lack of relevant basic theoretical methods. In engineering practice, there is a lack of experience in the structural layout and dynamic design of high thrust-to-weight ratio turbofan engines. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for suppressing vibration coupling of a common load-bearing frame-dual rotor system of an aircraft engine, so as to effectively suppress the vibration coupling of the common load-bearing frame-dual rotor system of a high thrust turbofan engine under complex working conditions, thereby making the aircraft engine have a relatively stable working state within the working speed range.

[0005] The present invention is implemented by providing a method for suppressing vibration coupling of a common load-bearing frame-dual rotor system of an aircraft engine, wherein the common load-bearing frame is a common load-bearing frame between turbine stages of a high-thrust turbofan engine, and the method comprises the following steps: Step S1: inputting structural parameters of the common load-bearing frame-dual rotor system of the aircraft engine to be analyzed; Step S2: Establish a finite element model and calculate the Campbell diagram of the common load-bearing frame-dual rotor system; Step S3: selecting a dangerous speed point within the working speed range, calculating the transient dynamic response of the common load-bearing frame-dual rotor system, and determining whether the transient dynamic response meets the requirements; Step S4: When the requirements are not met, the common load-bearing frame is optimized and steps S2 and S3 are repeated until the transient dynamic response of the common load-bearing frame-dual rotor system within the operating speed range meets the requirements.

[0006] Preferably, the structural parameters in step S1 include material parameters, structural geometric parameters, and loads received during operation.

[0007] Preferably, the step S2 is specifically: Based on the structural parameters extracted in step S1, a finite element model is established, and the resonant speed distribution characteristics of the common load-bearing frame-dual rotor system are calculated and analyzed to obtain the Campbell diagram of the common load-bearing frame-dual rotor system within the operating speed range.

[0008] Preferably, the step S3 is specifically: Based on the resonant speed distribution characteristics obtained in step S2, the intersection of the speed line and the modal frequency line is selected as a potential dangerous speed point. Considering that the speed directions of the dual rotors are generally different, it is necessary to determine the dangerous speed point based on the modal vibration type. Specifically, if a certain order of modal vibration type is mainly high-pressure rotor vibration, the intersection of the high-pressure rotor speed line and the modal positive precession frequency line of this order is selected as the dangerous point, which is consistent with the concept of conventional critical speed points. In addition, since the shared load-bearing frame can transmit the interactive excitation between rotors, the intersection of the low-pressure rotor speed line and the modal reverse precession frequency line of this order is selected as the dangerous point; the transient dynamic response of the shared load-bearing frame-dual rotor system when it is at the dangerous speed point is calculated, and whether the transient dynamic response meets the requirements for long-term stable operation of the aircraft engine is judged according to the calculation results.

[0009] Preferably, the step S4 is specifically: Based on the judgment result of step S3, if the transient dynamic response of a certain dangerous speed point does not meet the requirements, it is considered that the common load-bearing frame-dual rotor system has a vibration coupling problem, and the common load-bearing frame needs to be optimized. The optimization design includes improving the geometric configuration of the common load-bearing frame and designing a vibration absorption-energy dissipation structure in the common load-bearing frame. After completing the optimization design, repeat steps S2 and S3 until the transient dynamic response of the common load-bearing frame-dual rotor system within the operating speed range meets the requirements for long-term stable operation of the aircraft engine.

[0010] Further preferably, the geometric configuration of the common load-bearing frame is improved as follows: The common bearing seat of two bearings in the common load-bearing frame is changed into two bearings which are respectively installed on the inner ring of the load-bearing frame through their own bearing seats, cone shells and flange edges.

[0011] The above-mentioned improved design optimizes the force transmission route in the common load-bearing frame, reduces the intersection of the dynamic response force transmission routes of the high-pressure rotor and the low-pressure rotor in the common load-bearing frame structure, reduces the mutual excitation of the dynamic response between the high-pressure rotor and the low-pressure rotor, reduces the dynamic response of the dual rotor-common load-bearing frame system within the operating speed range, and realizes effective suppression of vibration coupling.

[0012] Further preferably, designing the vibration absorption-energy dissipation structure in the common load-bearing frame is to design the vibration absorption-energy dissipation structure for the common load-bearing frame according to the frequency range corresponding to the dangerous rotation speed point.

[0013] The design of the above-mentioned vibration absorption and energy dissipation structure absorbs and dissipates the vibration energy transmitted to the common load-bearing frame by the high-pressure rotor and the low-pressure rotor respectively, so as to reduce the dynamic response near the dangerous speed point and effectively suppress the vibration coupling of the dual rotor-common load-bearing frame system.

[0014] Compared with the prior art, the advantages of the present invention are: The present invention is based on the analysis of vibration coupling phenomena and mechanisms, and geometrically modifies the common load-bearing frame and designs a vibration absorption-energy dissipation structure. Through these two aspects, the vibration coupling of the common load-bearing frame-dual rotor system is suppressed. The method flow is concise and clear, and the operation process is clear and convenient. On the basis of relevant engineering experience, better optimization design results can be quickly obtained. Using the optimization design method proposed in the present invention, during the development and design stage of aircraft engine models, the vibration coupling of the common load-bearing frame-dual rotor system can be effectively suppressed, and the dynamic response within the working speed range can be greatly reduced, so that the common load-bearing frame-dual rotor system can meet the structural and dynamic design requirements. It has important engineering significance for promoting the overall structural design and model development progress of aircraft engines. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a flow chart of the present invention; Figure 2 It is a structural schematic diagram of a common load-bearing frame-dual rotor system; Figure 3 It is the vibration coupling situation of the common load-bearing frame-dual rotor system; Figure 4 It is the Campbell diagram of the common load-bearing frame-dual rotor system; Figure 5 The original design scheme (1) and the geometric configuration improvement scheme (2) of the common load-bearing frame; Figure 6 It is a schematic diagram of the vibration absorption and energy dissipation structure in the common load-bearing frame; Figure 7 The dynamic response of the common load-bearing frame-dual rotor system varies with the speed in different design schemes. DETAILED DESCRIPTION

[0016] In order to make the technical solution and advantages of the present invention clearer, the technical solution of the present application will be further described in detail in detail with reference to the accompanying drawings. It is understandable that the specific embodiments described herein are only partial embodiments of the present application, which are only used to explain the present application, not to limit the present application. It should be noted that, for ease of description, only the parts related to the present application are shown in the accompanying drawings, and other related parts can refer to the usual design. In the absence of conflict, the embodiments in the present application and the technical features in the embodiments can be combined with each other to obtain new embodiments.

[0017] Figure 1 The flowchart of the vibration coupling suppression method of the common load-bearing frame-dual rotor system of the aircraft engine provided by the present invention is as follows: Figure 2~Figure 7 This application is described in further detail.

[0018] The use of a common load-bearing frame is a common overall structural layout scheme for high thrust-to-weight ratio turbofan engines. Figure 2 The schematic diagram of the structure of a common load-bearing frame-dual rotor system in a typical high thrust-to-weight ratio turbofan engine is shown, in which a is the low-pressure rotor, b is the high-pressure rotor, and c is the common load-bearing frame.

[0019] Figure 3 This is a deformation cloud diagram of the shared load-bearing frame-dual rotor system at a certain operating speed point, which is used to reflect the vibration coupling situation. There is often an obvious vibration coupling problem between the high-pressure rotor, the low-pressure rotor and the shared load-bearing frame, which is the most severe dynamic problem faced by the overall structural layout scheme using a shared load-bearing frame.

[0020] Figure 4 It is the Campbell diagram of the shared load-bearing frame-dual rotor system. Since the high-pressure rotor and the low-pressure rotor rotate in opposite directions, the intersection of the high-pressure speed line and the positive precession modal line, and the intersection of the low-pressure speed line and the reverse precession modal line correspond to the resonant speed points that may be excited during the operation of the engine. Within the operating speed range, there are two intersections, indicating that there is a potential possibility of causing resonance in the shared load-bearing frame-dual rotor system near these two speeds. It should be specially noted that not every intersection in the Campbell diagram will cause resonance, and further confirmation is required by further transient calculation to obtain the dynamic response of the system at the corresponding speed. The shared load-bearing frame-dual rotor system of this embodiment is a dangerous speed point near the intersection of the high-pressure speed line and the second-order mode positive precession modal line. Through calculation, it is found that near this speed point, the dynamic response of the bearing position exceeds the maximum dynamic response required by the design, that is, it does not meet the requirements of long-term stable operation of the aircraft engine.

[0021] like Figure 5 As shown in Figure 2, the geometrical configuration of the common load-bearing frame is optimized. Figure 5 In the original design in (1), Figure 5 The improvement of the geometric configuration in (2) is mainly to modify the common bearing seat into a separate bearing seat, and the two bearings are installed on the inner ring of the load-bearing frame through the bearing seat, cone shell, and flange edge. Through the above modification, the dynamic response transmitted by the two rotors to the load-bearing frame will be transmitted along their respective force transmission routes until they intersect at the overlap position between the cone shells. Compared with the shared bearing seat of the original scheme, the improved design optimizes the force transmission route, delays and reduces the spatial range of the interaction between the high-pressure and low-pressure rotor dynamic responses, thereby achieving the effect of suppressing vibration coupling.

[0022] The method of optimizing the geometric configuration can appropriately adjust the modal frequency of the relevant mode, thereby achieving the effect of "avoiding resonance". However, the adjustment range of the modal frequency is generally small. In engineering, it is often the case that the adjusted modal frequency is still close to the working speed, making it difficult to achieve the ideal "avoiding resonance" effect. In this case, a vibration absorption and energy dissipation structure can be added to the common load-bearing frame, such as Figure 6 As shown in the figure, d represents a schematic diagram of the vibration absorption-energy dissipation structure. It should be noted that the vibration absorption-energy dissipation structure in the figure is only for illustration, and its specific structure and specific setting position need to be set according to specific circumstances. For example, patent CN118364588A introduces a metal rubber vibration absorption-energy dissipation structure and its design method, and it has been applied in relevant shared load-bearing frame structures.

[0023] By adjusting the parameters of the vibration absorption and energy dissipation structure, the dynamic response of the common load-bearing frame-dual rotor system within a specific speed range can be reduced. By absorbing and dissipating the vibration energy at dangerous working speeds in the common load-bearing frame structure, the vibration coupling of the high-pressure and low-pressure rotors in the common load-bearing frame can be effectively reduced, thereby significantly reducing the dynamic response, which meets the requirements for long-term stable operation of aircraft engines.

[0024] Figure 7The graphs showing the change in dynamic response of the shared load-bearing frame-dual rotor system with speed in different design schemes are shown. In the original design scheme, there is a resonance point within the operating speed range that can be excited by the rotor rotation effect, resulting in a dynamic response that does not meet the requirements. By improving the geometric configuration of the shared load-bearing frame, the resonance phenomenon moves corresponding to the operating speed, and the dynamic response within the operating speed range has been greatly reduced, but it still does not fully meet the requirements. On the basis of the improvement of the geometric configuration, after adding a vibration absorption-energy dissipation structure, the peak value of the resonance response has been greatly reduced, and the dynamic response within the operating speed range has been greatly reduced and meets the requirements for long-term stable operation of aircraft engines. The vibration coupling suppression design method proposed in the present invention has achieved ideal results.

[0025] So far, the technical solution of the present application has been described in conjunction with the preferred embodiments shown in the accompanying drawings. Those skilled in the art should understand that the scope of protection of the present application is obviously not limited to these specific embodiments. Without departing from the principles of the present application, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the scope of protection of the present application.

Claims

1. A method for suppressing vibration coupling of a common bearing frame-dual rotor system of an aircraft engine, characterized in that: The common load-bearing frame is a common load-bearing frame between turbine stages of a high-thrust turbofan engine, and the method comprises the following steps: Step S1: inputting structural parameters of the common load-bearing frame-dual rotor system of the aircraft engine to be analyzed; Step S2: Establish a finite element model and calculate the Campbell diagram of the common load-bearing frame-dual rotor system; Step S3: selecting a dangerous speed point within the working speed range, calculating the transient dynamic response of the common load-bearing frame-dual rotor system, and determining whether the transient dynamic response meets the requirements; Step S4: When the requirements are not met, the common load-bearing frame is optimized and steps S2 and S3 are repeated until the transient dynamic response of the common load-bearing frame-dual rotor system within the operating speed range meets the requirements.

2. The method for suppressing vibration coupling of a common bearing frame-dual rotor system of an aircraft engine according to claim 1, characterized in that: The structural parameters in step S1 include material parameters, structural geometric parameters and loads received during the working process.

3. The method for suppressing vibration coupling of a common bearing frame-dual rotor system of an aircraft engine according to claim 1, characterized in that: The step S2 is specifically as follows: Based on the structural parameters extracted in step S1, a finite element model is established, and the resonant speed distribution characteristics of the common load-bearing frame-dual rotor system are calculated and analyzed to obtain the Campbell diagram of the common load-bearing frame-dual rotor system within the operating speed range.

4. The method for suppressing vibration coupling of a common bearing frame-dual rotor system of an aircraft engine according to claim 3, characterized in that: The step S3 is specifically as follows: Based on the resonant speed distribution characteristics obtained in step S2, the intersection of the speed line and the modal frequency line is selected as a potential dangerous speed point, and the transient dynamic response of the shared load-bearing frame-dual rotor system at the dangerous speed point is calculated. According to the calculation results, it is judged whether the transient dynamic response meets the requirements for long-term stable operation of the aircraft engine.

5. The method for suppressing vibration coupling of a common bearing frame-dual rotor system of an aircraft engine according to claim 1, characterized in that: The step S4 is specifically as follows: Based on the judgment result of step S3, if the transient dynamic response of a certain dangerous speed point does not meet the requirements, it is considered that the common load-bearing frame-dual rotor system has a vibration coupling problem, and the common load-bearing frame needs to be optimized. The optimization design includes improving the geometric configuration of the common load-bearing frame and designing a vibration absorption-energy dissipation structure in the common load-bearing frame. After completing the optimization design, repeat steps S2 and S3 until the transient dynamic response of the common load-bearing frame-dual rotor system within the operating speed range meets the requirements for long-term stable operation of the aircraft engine.

6. The method for suppressing vibration coupling of a common bearing frame-dual rotor system of an aircraft engine according to claim 5, characterized in that: The geometric configuration of the common load-bearing frame is specifically improved as follows: The common bearing seat of two bearings in the common load-bearing frame is changed into two bearings which are respectively installed on the inner ring of the load-bearing frame through their own bearing seats, cone shells and flange edges.

7. The method for suppressing vibration coupling of a common bearing frame-dual rotor system of an aircraft engine according to claim 5, characterized in that: The vibration absorption and energy dissipation structure is designed in the common load-bearing frame according to the frequency range corresponding to the dangerous rotation speed point.

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