Aerospace engine squirrel cage vibration stress calibration device and design method thereof

Abstract

The present application relates to the field of aero-engines and rotating machinery, and discloses an aero-engine squirrel cage vibration stress calibration device and a design method thereof. The calibration device comprises a transfer shaft, a transfer disc, a counterweight disc and counterweight blocks. The axial spacing of the counterweight disc and the transfer disc and the upper limit of the mass of the counterweight blocks are determined by the corresponding device design method. The counterweight blocks can generate real unbalanced centrifugal load by rotating with the rotating shaft. The squirrel cage actual assembly form and unbalanced stress working condition of the aero-engine can be accurately simulated. The deviation caused by the simulation boundary condition and the average stress calculation in the original finite element calibration scheme is avoided. The accurate corresponding relationship between the squirrel cage strain and the actual vibration displacement is established by relying on the calibration device. The squirrel cage vibration stress calibration precision can be improved. In the engine whole machine test, the calibration result can truly reflect the vibration state of the fulcrum, and effectively avoid the technical drawbacks of misjudging the engine operating state and inducing structure failure due to distorted vibration data.

Description

Technical Field

[0001] This invention relates to the field of aero-engines and rotating machinery, and discloses an aero-engine squirrel cage vibration stress calibration device and its design method. Background Technology

[0002] As advanced aero-engines operate at increasingly higher speeds, their rotors often exceed first-order or even multiple critical speeds. For such engines, reliability and structural integrity become critical issues, and the vibration and stability design of the rotor-support system is often the crux of the problem. In rotor dynamics design, a squirrel cage (structure such as...) is employed. Figure 3 (As shown) The elastic element used as a support is used to adjust the critical speed of the rotor. During whole-machine testing, vibration measuring points are added near the engine support or outside the casing to monitor the engine vibration state or verify the engine's dynamic design results. The ideal installation location for the vibration measuring point is at the support bearing, but in reality, vibration sensors cannot be installed due to the small space in the bearing cavity, oil and gas, high temperature, etc. In this case, strain gauges are usually attached to the cage bars of the elastic support, and the vibration of the support is indirectly obtained by observing the change in the dynamic stress of the cage.

[0003] The current method for determining the relationship between dynamic stress and support displacement is to establish this relationship through finite element analysis. This method involves three steps: first, applying a unit lateral displacement at the bearing mounting location in the squirrel cage to obtain the stress distribution under unit lateral deformation; second, selecting a strain gauge patch area based on the stress distribution of the cage bars; and third, calculating the average stress of the strain gauges based on the size of the patch area, thus obtaining the relationship between the strain gauge stress and the support displacement. During whole-machine testing, the rotor vibration displacement is obtained based on this correspondence. The main problem with this method is that the simulation calculation is highly sensitive to boundaries, leading to a certain deviation between the calculated results and actual conditions. Furthermore, the calculation of the average stress in the strain gauge area is significantly influenced by human factors, resulting in a large difference between the final measured strain value and the actual deformation of the squirrel cage. This makes it impossible to realistically simulate the actual assembly form and unbalanced stress conditions of the engine rotor, failing to achieve the purpose of monitoring engine vibration and verifying rotor dynamics design. In severe cases, it may lead to incorrect judgments about the engine's condition, resulting in serious malfunctions. Summary of the Invention

[0004] The purpose of this invention is to provide a vibration stress calibration device and its design method for aero-engine squirrel cages, which can accurately simulate the actual assembly form and unbalanced stress conditions of aero-engine squirrel cages and improve the calibration accuracy of squirrel cage vibration stress.

[0005] To achieve the above-mentioned technical effects, the technical solution adopted by the present invention is as follows:

[0006] A vibration stress calibration device for a squirrel cage of an aircraft engine, comprising: The adapter shaft has its driving end connected to a drive motor. The adapter plate is coaxially mounted on the adapter shaft via a bearing, and the adapter plate is used to coaxially fix the rat cage to be calibrated. A counterweight plate is fixedly mounted on the adapter shaft, and the counterweight plate and the drive end are respectively located on both sides of the adapter plate; A counterweight is mounted on the counterweight plate to generate an unbalanced force by rotation.

[0007] Furthermore, the counterweight disc is coaxially fixed to the adapter shaft by a locking mechanism.

[0008] Furthermore, the counterweight is a counterweight bolt, the counterweight plate has mounting holes, and the counterweight bolt is threaded into the mounting holes.

[0009] Furthermore, a sleeve is coaxially disposed at the center of the adapter plate and fitted onto the adapter shaft, and the sleeve is provided with locking screws for fixing the adapter plate onto the adapter shaft.

[0010] A design method for a vibration stress calibration device for an aircraft engine squirrel cage, used to design the aforementioned vibration stress calibration device for an aircraft engine squirrel cage, comprising: Based on the geometric parameters of the squirrel cage to be calibrated, a three-dimensional model of the vibration stress calibration device for the aero-engine squirrel cage is constructed. Based on the diameter of the adapter shaft, the distance between the adapter plate and the drive end of the adapter shaft, and the mechanical performance parameters of the adapter shaft in the three-dimensional model of the aero-engine squirrel cage vibration stress calibration device, the axial distance between the counterweight plate and the adapter plate is obtained by analysis. Based on the installation radius of the counterweight from the axis of the adapter shaft, the stiffness of the squirrel cage, the mechanical performance parameters of the adapter shaft, the limiting clearance of the squirrel cage, and the design speed required for the vibration stress calibration of the squirrel cage, the upper limit of the counterweight mass is obtained through the counterweight mass analysis model. Based on the axial distance between the counterweight plate and the transfer plate and the upper limit of the mass of the counterweight block, the design of the vibration stress calibration device for the squirrel cage of the aero-engine is completed.

[0011] Furthermore, the mechanical performance parameters of the adapter shaft include the design bending stiffness and elastic modulus of the adapter shaft.

[0012] Furthermore, the axial distance between the counterweight plate and the adapter plate is determined by the following formula:

[0013] in: The axial distance between the counterweight plate and the adapter plate. Design bending stiffness for the adapter shaft, The elastic modulus of the adapter shaft material. The diameter of the adapter shaft. This is the distance between the adapter plate and the end of the adapter shaft drive.

[0014] Furthermore, the expression for the counterweight mass analysis model is:

[0015] in, This represents the upper limit of the counterweight's mass. The limiting gap for the rat cage. For the rigidity of the mouse cage, Design bending stiffness for the adapter shaft, The installation radius of the counterweight from the axis of the adapter shaft. The design rotational speed required for calibrating the vibration stress of the squirrel cage.

[0016] Compared with the prior art, the beneficial effects of this invention are: This invention relies on a calibration device comprising an adapter shaft, an adapter plate, a counterweight plate, and a counterweight block. Combined with a corresponding device design method, it determines the axial distance between the counterweight plate and the adapter plate, as well as the upper limit of the counterweight block's mass. By utilizing the counterweight block's rotation with the shaft to generate a realistic unbalanced centrifugal load, it accurately simulates the actual assembly form and unbalanced stress conditions of an aero-engine squirrel cage. This avoids the deviations caused by simulation boundary conditions and average stress calculations in traditional finite element calibration schemes. Furthermore, by establishing a precise correspondence between squirrel cage strain and actual vibration displacement using the calibration device, it improves the accuracy of squirrel cage vibration stress calibration. In engine whole-machine testing, the calibration results can accurately reflect the vibration state of the support points, effectively avoiding the technical drawbacks of misjudging engine operating status and inducing structural failures due to distorted vibration data. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the vibration stress calibration device for the aero-engine squirrel cage after assembly with the squirrel cage in the embodiment. Figure 2 This is a schematic diagram of the vibration stress calibration device for a squirrel cage of an aero-engine in the embodiment. Figure 3 This is a schematic diagram of the structure of the aircraft engine squirrel cage in the embodiment; Figure 4 This is a cross-sectional view of the vibration stress calibration device for the squirrel cage of an aero-engine in the embodiment. Figure 5 This is a schematic diagram showing the bonding position of strain gauges when calibrating the vibration stress of the squirrel cage of an aero-engine in the embodiment. Figure 6 This is a flowchart illustrating the design method of the vibration stress calibration device for aero-engine squirrel cage in the embodiment. Among them, 1-adapter shaft, 2-drive motor, 3-adapter plate, 4-counterweight plate, 41-mounting hole, 6-squirrel cage. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings. However, this should not be construed as limiting the scope of the above-described subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0019] See Figures 1 to 5 The present invention provides a vibration stress calibration device for a squirrel cage of an aircraft engine, comprising: Adapter shaft 1, the drive end of which is connected to drive motor 2; The adapter plate 3 is coaxially mounted on the adapter shaft 1 via a bearing. The adapter plate 3 is used to coaxially fix the rat cage 6 to be calibrated. The counterweight plate 4 is fixedly installed on the adapter shaft 1, and the counterweight plate 4 and the drive end are respectively located on both sides of the adapter plate 3; A counterweight is installed on the counterweight disk 4 to generate an unbalanced force by rotation.

[0020] Based on the same inventive concept, see Figure 6 The present invention also provides a design method for an aircraft engine squirrel cage vibration stress calibration device, used to design the aforementioned aircraft engine squirrel cage vibration stress calibration device, comprising: Based on the geometric parameters of the squirrel cage 6 to be calibrated, a three-dimensional model of the vibration stress calibration device for the aero-engine squirrel cage is constructed. Based on the diameter of the adapter shaft 1, the distance between the adapter disk 3 and the drive end of the adapter shaft 1, and the mechanical performance parameters of the adapter shaft 1 in the three-dimensional model of the aero-engine squirrel cage vibration stress calibration device, the axial distance between the counterweight disk 4 and the adapter disk 3 is analyzed and obtained. Based on the installation radius of the counterweight from the axis of the adapter shaft 1, the stiffness of the squirrel cage 6, the mechanical performance parameters of the adapter shaft 1, the limiting gap of the squirrel cage 6, and the design speed required for the vibration stress calibration of the squirrel cage 6, the upper limit of the mass of the counterweight is obtained through the counterweight mass analysis model. Based on the axial distance between the counterweight plate 4 and the adapter plate 3 and the upper limit of the mass of the counterweight block, the design of the vibration stress calibration device for the squirrel cage of the aero-engine is completed.

[0021] This invention relies on a calibration device comprising a transfer shaft 1, a transfer plate 3, a counterweight plate 4, and a counterweight block. Combined with a corresponding device design method, it determines the axial distance between the counterweight plate 4 and the transfer plate 3, as well as the upper limit of the counterweight block's mass. This allows the counterweight block to generate a realistic unbalanced centrifugal load as it rotates with the shaft, accurately simulating the actual assembly form and unbalanced stress conditions of the aero-engine squirrel cage 6. This avoids the deviations caused by simulation boundary conditions and average stress calculations in traditional finite element calibration schemes. Furthermore, by establishing a precise correspondence between squirrel cage strain and actual vibration displacement using the calibration device, it improves the accuracy of the squirrel cage 6 vibration stress calibration. In engine whole-machine testing, this calibration result can accurately reflect the vibration state of the support point, effectively avoiding the technical drawbacks of misjudging the engine's operating status due to distorted vibration data and inducing structural failures.

[0022] Example This embodiment further elaborates on the vibration stress calibration device for aero-engine squirrel cages and its design method.

[0023] See Figures 1 to 4 The vibration stress calibration device for the aero-engine squirrel cage includes a transfer shaft 1, a transfer plate 3, a counterweight plate 4, and a counterweight block.

[0024] One end of the adapter shaft 1 is connected to the drive motor 2, and the other end is fixed with a counterweight plate 4 by a locking nut. The adapter shaft 1 is a stepped shaft with a step at the end. The locking nut is threaded to the adapter shaft 1. The step and the locking nut are used to fix the counterweight plate 4 to the adapter shaft 1.

[0025] The adapter plate 3 is coaxially mounted on the adapter shaft 1 via bearings and is positioned close to the counterweight plate 4. During calibration, the adapter plate 3 is used to coaxially fix the squirrel cage 6 to be calibrated. The counterweight plate 4 has a ring of mounting holes 41, and the counterweight is installed in the mounting holes 41. During calibration, the drive motor 2 drives the counterweight plate 4 with the counterweight to rotate via the adapter shaft 1, thereby generating an unbalanced centrifugal force, which drives the adapter shaft 1 to produce eccentric vibration. The adapter shaft 1 transmits the vibration to the squirrel cage 6 to be calibrated through the adapter plate 3, so as to simulate the unbalanced load generated during the operation of the engine rotor and cause the squirrel cage 6 to vibrate laterally.

[0026] In this embodiment, the counterweight is a counterweight bolt, the mounting hole 41 is a threaded hole or a through hole without threads, and the counterweight bolt is equipped with a nut so that the counterweight bolt is fixed on the counterweight plate 4 and will not loosen due to vibration.

[0027] In this embodiment, a sleeve is coaxially mounted on the adapter shaft 1 at the center of the adapter plate 3. The sleeve is equipped with a locking screw for fixing the adapter plate 3 to the adapter shaft 1. After adjusting the position of the adapter plate 3 as needed, the locking screw is screwed in from the side wall of the sleeve and pressed against the outer wall of the adapter shaft 1 to lock the axial position of the adapter plate 3. This adapts to the installation and calibration requirements of different sized and specifications of the calibrated mouse cage 6.

[0028] Based on the same inventive concept, see Figure 6 This embodiment also provides a design method for an aircraft engine squirrel cage vibration stress calibration device, used to design the aforementioned aircraft engine squirrel cage vibration stress calibration device, including: Step 1: Based on the geometric parameters such as the outer diameter and inner diameter of the squirrel cage 6 to be calibrated, construct a three-dimensional model of the vibration stress calibration device for the aero-engine squirrel cage.

[0029] Step 2: See Figure 4 According to the diameter of the adapter shaft 1 in the three-dimensional model of the aero-engine squirrel cage vibration stress calibration device. The distance between adapter plate 3 and the drive end of adapter shaft 1 Design bending stiffness of adapter shaft 1 ; Elastic modulus of the material of adapter shaft 1 ,pass The axial distance between the counterweight plate 4 and the adapter plate 3 was obtained through analysis. This embodiment determines the axial distance between the counterweight plate 4 and the adapter plate 3. The design of the adapter shaft 1 takes into account its bending stiffness and elastic characteristics, which allows the eccentric vibration generated by the counterweight plate 4 to be transmitted to the calibrated squirrel cage 6 more efficiently, avoiding excessive cancellation of vibration energy inside the adapter shaft 1, and ensuring that the vibration stress obtained by the squirrel cage 6 during the calibration process meets the test accuracy requirements.

[0030] Step 3: Determine the installation radius of the counterweight from the axis of adapter shaft 1. The stiffness of the rat cage 6 The mechanical performance parameters of the adapter shaft 1, the amplitude limiting gap of the squirrel cage 6, and the design speed required for the vibration stress calibration of the squirrel cage 6 are analyzed using the counterweight mass analysis model to obtain the upper limit of the counterweight mass.

[0031] The expression for the mass analysis model of the counterweight is:

[0032] in, This represents the upper limit of the counterweight's mass. The limiting gap for the mouse cage 6, Let be the stiffness of cage 6. The design bending stiffness of adapter shaft 1, The installation radius of the counterweight from the axis of the adapter shaft 1 is equal to the radius of the mounting hole 41 from the axis of the adapter shaft 1. The design rotational speed required for calibrating the vibration stress of the squirrel cage 6.

[0033] In determining the upper limit of the counterweight mass, this embodiment considers multiple parameters such as the stiffness of the squirrel cage 6 itself, the amplitude limiting gap, and the calibration design speed. This avoids the squirrel cage 6 being damaged due to excessive counterweight mass causing the vibration amplitude to exceed the allowable range. At the same time, it ensures that the vibration excitation that meets the calibration requirements can be output at the design speed, so that the calibration has both test safety and calibration effectiveness. This ensures that the amplitude of vibration stress is always within a controllable range that meets the test requirements, and that the calibration device can accurately simulate the unbalanced force condition of the squirrel cage 6.

[0034] Step 4: Based on the axial distance between the counterweight plate 4 and the adapter plate 3 and the upper limit of the mass of the counterweight block, complete the design of the vibration stress calibration device for the aero-engine squirrel cage.

[0035] It should be noted that the weight of the adapter plate 3 should be as light as possible when designing it. The design of the aircraft engine squirrel cage vibration stress calibration device also needs to consider the natural frequency of the calibration device excluding the drive motor 2, which can be determined using the formula... Calculations are performed, in which, The natural frequency of the vibration stress calibration device for the squirrel cage of an aircraft engine without drive motor 2. Let be the stiffness of cage 6. The design bending stiffness of adapter shaft 1, The mass of counterweight plate 4. For the natural frequency of the aircraft engine squirrel cage vibration stress calibration device, it should be higher than the upper limit rotational frequency of the drive motor 2 during calibration, preferably greater than 50Hz.

[0036] Furthermore, the weight of counterweight plate 4 is Where the structure of the counterweight disk 4 allows, the radius of the mounting hole 41 on the counterweight disk 4 should be as large as possible in order to obtain a greater centrifugal force with minimal counterweight.

[0037] The calibration is performed using the aircraft engine squirrel cage vibration stress calibration device described in this invention. The calibration method includes the following steps: S1: Strain gauges for dynamic stress testing are attached to the rat cage 6. Based on the stress mode of cage 6, under alternating loads, the maximum stress in cage 6 generally occurs at the root of the cage bars. Therefore, dynamic stress test strain gauges are attached to the outer surface of the cage bar roots. Figure 5Position A or position B in the cage. To obtain more comprehensive test data and avoid damage to the measuring points, one cage bar is typically selected at each of the 12 o'clock, 3 o'clock, 6 o'clock, and 9 o'clock positions of cage 6, and a strain gauge is attached to the same position on each cage bar, for a total of four strain gauges. The direction of the strain gauge wires should be consistent with the direction of the cage bar.

[0038] S2: Strain calibration of the squirrel cage Assemble the squirrel cage 6 with the designed adapter shaft 1, adapter plate 3, counterweight plate 4, counterweight block, and drive motor 2. After assembly, it should look like... Figure 6 As shown. The mounting edge of the squirrel cage 6 is fixedly connected to the adapter plate 3 by bolts. Displacement sensor A and displacement sensor B are set on the mounting edge where the squirrel cage 6 connects to the adapter plate 3. One displacement sensor is in the vertical direction and the other is in the horizontal direction, with the two forming a 90-degree angle, which is used to obtain the vibration displacement of the squirrel cage 6 during the calibration process.

[0039] After assembly, the weight is determined according to the upper limit of the counterweight. Install a mass on the counterweight plate 4 After adjusting the counterweight screws, start the drive motor 2 and begin the calibration process. Simultaneously collect the dynamic stress and displacement of the squirrel cage 6 to obtain the corresponding table of squirrel cage strain and displacement. At this point, the squirrel cage strain calibration is complete. It should be noted that if the vibration displacement of the squirrel cage 6 is not ideal during the calibration process, heavier or lighter counterweight screws can be replaced, or the distance between the counterweight plate 4 and the adapter plate 3 can be adjusted.

[0040] Step 4: Install the calibrated squirrel cage 6 onto the engine. Once the calibrated squirrel cage 6 is installed on the engine, it can be used with the whole machine or core machine. During the test, the vibration state of the engine rotor can be accurately monitored based on the correspondence between the squirrel cage strain and the squirrel cage displacement.

[0041] The calibration method based on the vibration stress calibration device of the aero-engine squirrel cage involves attaching strain gauges at the root of the cage bars of squirrel cage 6 under high stress buckling. Then, the actual assembly state of squirrel cage 6 is simulated. The calibration device is used to simulate the unbalanced load of the rotor to obtain the correspondence between different unbalanced loads and the lateral displacement of the squirrel cage and the strain of the squirrel cage. This allows for accurate determination of the correlation between the squirrel cage stress and the squirrel cage vibration displacement, enabling precise monitoring of the vibration state of the engine rotor in more complex overall engine environments and avoiding serious malfunctions caused by misjudgment of the engine vibration state.

[0042] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A device for calibrating vibration stress in a squirrel cage of an aircraft engine, characterized in that, include: The adapter shaft (1) is driven by the drive end of the adapter shaft (1) and is connected to the drive motor (2). The adapter plate (3) is coaxially mounted on the adapter shaft (1) via a bearing. The adapter plate (3) is used to coaxially fix the rat cage (6) to be calibrated. The counterweight plate (4) is fixedly installed on the adapter shaft (1), and the counterweight plate (4) and the drive end are located on both sides of the adapter plate (3); A counterweight is used to be installed on the counterweight plate (4) to generate an unbalanced force by rotation.

2. The aircraft engine squirrel cage vibration stress calibration device according to claim 1, characterized in that, The counterweight plate (4) is coaxially fixed to the adapter shaft (1) by a locking mechanism.

3. The aircraft engine squirrel cage vibration stress calibration device according to claim 2, characterized in that, The counterweight is a counterweight bolt, and the counterweight plate (4) is provided with a mounting hole (41). The counterweight bolt is threaded into the mounting hole (41).

4. The vibration stress calibration device for aero-engine squirrel cages according to claim 1, characterized in that, The adapter plate (3) is coaxially provided with a sleeve on the adapter shaft (1) at its center position, and the sleeve is provided with a locking screw for fixing the adapter plate (3) on the adapter shaft (1).

5. A design method for a vibration stress calibration device for an aero-engine squirrel cage, used to design the vibration stress calibration device for an aero-engine squirrel cage as described in any one of claims 1-4, characterized in that, include: Based on the geometric parameters of the squirrel cage (6) to be calibrated, a three-dimensional model of the vibration stress calibration device for the aero-engine squirrel cage is constructed. Based on the diameter of the transfer shaft (1), the distance between the transfer plate (3) and the drive end of the transfer shaft (1), and the mechanical performance parameters of the transfer shaft (1) in the three-dimensional model of the aero-engine squirrel cage vibration stress calibration device, the axial distance between the counterweight plate (4) and the transfer plate (3) is obtained by analysis. Based on the installation radius of the counterweight from the axis of the adapter shaft (1), the stiffness of the squirrel cage (6), the mechanical performance parameters of the adapter shaft (1), the limiting gap of the squirrel cage (6), and the design speed required for the vibration stress calibration of the squirrel cage (6), the upper limit of the mass of the counterweight is obtained by analyzing the counterweight mass analysis model. Based on the axial distance between the counterweight plate (4) and the transfer plate (3) and the upper limit of the mass of the counterweight block, the design of the vibration stress calibration device for the squirrel cage of the aero-engine is completed.

6. The design method according to claim 5, characterized in that, The mechanical performance parameters of the adapter shaft (1) include the design bending stiffness and elastic modulus of the adapter shaft (1).

7. The design method according to claim 6, characterized in that, The axial distance between the counterweight plate (4) and the adapter plate (3) is determined by the following formula: in: The axial distance between the counterweight plate (4) and the adapter plate (3) is... For the design bending stiffness of the adapter shaft (1), The elastic modulus of the material of the adapter shaft (1) is The diameter of the adapter shaft (1) is The distance between the adapter plate (3) and the drive end of the adapter shaft (1).

8. The design method according to claim 5, characterized in that, The expression for the mass analysis model of the counterweight is: in, This represents the upper limit of the counterweight's mass. The limiting gap of the rat cage (6), For the stiffness of the mouse cage (6), For the design bending stiffness of the adapter shaft (1), The installation radius of the counterweight from the axis of the adapter shaft (1) is given. The design rotation speed required for the vibration stress calibration of the mouse cage (6).

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