Rigidity-adjustable squirrel cage elastic supporting device

Abstract

The invention discloses a rigidity-adjustable squirrel cage elastic supporting device. The rigidity-adjustable squirrel cage elastic supporting device comprises a flange face, a cage bar, a hoop, a spring assembly, a bolt, a nut, a gasket and other fasteners. The structure is characterized in that the flange surface is provided with a bolt hole and is connected to the mounting surface of the rotor interface. The cage bars are evenly distributed in the circumferential direction and serve as a core part contributing to overall fixing bending rigidity of the elastic device. Fasteners such as the hoop, the spring assembly and the bolt are rigidity-adjustable parts, and the overall rigidity of the squirrel cage elastic support can be adjusted by adjusting the distribution form and the number of the fasteners. The design process is characterized in that the overall rigidity of the squirrel cage is estimated through a theoretical formula, then squirrel cage parameters are optimized through a preferable whale method, and parameters of the squirrel cage device, parameters of parts such as hoops and the number of spare parts are iteratively determined in combination with a finite element simulation method. According to the invention, the overall and local rigidity of the squirrel cage elastic device can be quickly and linearly adjusted, the cost of processing, mounting, testing and the like is reduced, and the vibration stability and safety of a high-speed and heavy-load rotor system are ensured.

Description

Technical Field

[0001] This invention relates to the field of high-speed, heavy-load rotor design for gas turbines / aero engines, and particularly to an elastic support device and design method for gas turbines / aero engines with adjustable stiffness. Background Technology

[0002] The flexible rotors of aero engines and gas turbines are often supported on squirrel-cage elastic support devices equipped with bearings. When the rotor accelerates from a standstill to its operating speed, it needs to pass its own critical speed. At this time, the vibration response will increase suddenly, which may cause faults such as rotor-stator rubbing, bearing jamming, blade or bearing damage, which will cause great harm to the normal operation of the whole machine.

[0003] Traditional squirrel cage elastic support design methods stipulate that once the elastic support device is manufactured, its stiffness is a fixed value. Therefore, to meet the needs of stiffness adjustment during testing or operation, spare parts with different stiffnesses often need to be prepared. However, this significantly increases the costs of design, manufacturing, and assembly. Furthermore, this replacement method makes it difficult to achieve continuous changes in the overall elastic support stiffness and may introduce other uncontrollable factors (such as human error), which has always been one of the design pain points of squirrel cage elastic supports.

[0004] Therefore, in order to avoid the above-mentioned shortcomings and ensure that the critical speed of the rotor is always within the resonance range (20%) of the operating speed, a reasonable squirrel cage elastic support design method is essential. Summary of the Invention

[0005] The purpose of this invention is to provide an adjustable stiffness elastic support device for a squirrel cage and its design method, so as to solve the existing problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a squirrel cage elastic support device, comprising a flange face, cage bars, clamps, spring assemblies, and fasteners such as bolts, nuts, and washers. The flange face is characterized by having bolt holes machined thereon, connecting to the mounting surface of the rotor interface. The cage bars are evenly distributed circumferentially, forming the core component contributing to the overall fixed bending stiffness of the elastic device. The clamps, spring assemblies, and bolts are adjustable stiffness components; the overall stiffness of the squirrel cage elastic support can be adjusted by changing their distribution and quantity.

[0007] Preferably, the lower contact surface of the clamp is in contact with the outer ring wall of the rat cage, and the inner side of the lower protrusion at the left and right ends of the clamp can be in contact with the side of the cage bars.

[0008] Preferably, the spring assembly is wrapped on the outside by a lightweight rigid hollow plastic tube and has a steel spring installed on the inside.

[0009] Preferably, the fastener serves to secure the clamp to the cage bars. A preload can be applied to the fastener to ensure a tight fit between the clamp and the cage bars.

[0010] Preferably, to achieve the adjustable stiffness effect of this solution, the specific design process is as follows: (1) Modal analysis of the rotor assembly is performed using the finite element method to estimate the stiffness fluctuation range of the squirrel cage elastic support that meets the critical speed requirement. (2) Based on the theoretical formula and the stiffness range obtained in step (1), estimate the squirrel cage parameters that meet the overall stiffness of the squirrel cage elastic support when there are no components such as clamps. (3) Based on the overall stiffness results of step (2), the structural parameters of the squirrel cage are determined by using a multi-objective optimization method, taking into account both the stiffness and strength performance of the elastic support of the squirrel cage. (4) Model the cage using the parameters obtained in step (3). Based on the stiffness fluctuation range in step (1), analyze the clamp assembly in two forms: "full ring" and "local". Determine the corresponding clamp structure parameters, quantity and distribution. (5) Develop a stiffness adjustment plan based on the results of step (4) and carry out the processing; (6) In actual testing or operation, based on the fluctuation range of rotor assembly stiffness, the predetermined scheme obtained in step (5) is used to achieve the effect of linearly adjusting the elastic support of the squirrel cage to a suitable stiffness value.

[0011] The rotor dynamics analysis model used in step (1) should include all rotor information (mast of each stage of rotor and stator, moment of inertia, etc.). Combined with the actual rotor support method, the fluctuation range of the equivalent support stiffness is confirmed when the critical speed is not within 20% of the operating speed. Then, the stiffness range of the squirrel cage elastic support is determined based on the stiffness value of the bearing [K]. min ,K max ].

[0012] In step (2), when the cross-section of the squirrel cage elastic support is approximately trapezoidal, according to Feng Guoquan et al.'s "Optimization Design and Experiment of Structural Parameters of Squirrel Cage Elastic Support", its stiffness is theoretically expressed as [K = NEab(a² + b²) / 2L³]. Where: a is the length of the long side of the trapezoidal cross-section of the cage bar; b is the length of the short side of the trapezoidal cross-section of the cage bar; L is the length of the cage bar; N is the number of cage bars; and E is the elastic modulus of the material.

[0013] In step (3), preferably, the "whale swallowing" optimization algorithm can be selected, with the minimization of the squirrel cage fatigue strength as the objective function. According to Feng Guoquan et al.'s "Parameter Optimization Design and Experiment of Squirrel Cage Elastic Support Structure", the fatigue stress can be calculated according to the formula [σ= 3Eu(a² + b²)^{0.5} / L²]. Where u is the radial deformation, the stiffness value obtained in step (2) can be used as the initial constraint condition, and the overall stiffness [K] can be set. 整体 Fluctuation range (e.g., [0.9K]) min 1.1K max The structural parameters (a, b, L, N) of the mouse cage are used as the combination of optimization parameters to begin optimization.

[0014] The "full-ring" clamp assembly method mentioned in step (4) is based on finite element simulation results, selecting full-ring clamps for assembly with the squirrel cage. The overall stiffness is adjusted by modifying the number of clamps, axial position, clearance, and fastener preload. When using full-ring clamps, the spring assembly is in a compressed state. When designing the maximum number of full-ring clamps [N'], it should satisfy [K... 整体 >5K max ].

[0015] The "local" clamp assembly method mentioned in step (4) involves assembling a non-full-ring circular arc clamp with the squirrel cage based on finite element simulation results. Local stiffness is adjusted by modifying the number of clamps, axial position, clearance, fastener preload, and clamp arc length. When using a local circular arc clamp, the spring assembly is in a stretched state. When designing the local clamp, the overall stiffness value K must be within [0.5K_overall, 1.5K_overall]. In actual assembly of the local clamp, it must be able to compensate for the maximum offset of the journal displacement [U_j] under gravity and unbalanced forces. max (e.g., 15mm).

[0016] The stiffness adjustment scheme formulated in step (5) can be divided into three types: "full-ring" clamp, "partial" clamp and "composite" clamp. By assembling and adjusting the type and number of clamp components, the overall and local stiffness of the squirrel cage elastic support can be linearly adjusted, so that the critical speed meets the requirements.

[0017] In step (6), the clamp combination (full ring type, partial type, full ring + partial type) can be adjusted according to the scheme determined in step (5) to adjust the actual stiffness of the squirrel cage elastic support device to the optimal level.

[0018] Compared with existing technologies, the advantages of this invention are: 1. This solution can quickly and continuously adjust the overall stiffness of the squirrel cage elastic support device, greatly reducing processing, installation, and testing costs, and effectively ensuring that the rotor critical speed falls within the safe operating speed range. 2. This solution can overcome the uncertainty of vibration response caused by gravity, unbalanced forces, and the squeezing oil film damper. By adjusting the local stiffness, it ensures that vibration measurement indicators (such as journal vibration amplitude) meet design requirements. Attached Figure Description

[0019] Figure 1 This is a three-dimensional structural diagram of the present invention.

[0020] Figure 2 This is a schematic diagram of a three-dimensional partial structure of the clamp of the present invention.

[0021] Figure 3 This is a schematic diagram of the clamp-on rat cage structure of the present invention.

[0022] Figure 4 This is a schematic diagram of an example of the "complete ring" type of the present invention.

[0023] Figure 5 This is a schematic diagram of a "partial" example of the present invention.

[0024] Figure 6 This is a design flowchart for the present invention.

[0025] In the diagram: 1. Flange face; 2. Cage bar; 3. Clamp; 4. Spring assembly; 5. Fastener. Detailed Implementation

[0026] To make the technical solution and advantages of this application clearer, the technical solution of this application will be described in a clearer and more complete manner below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only some embodiments of this application, and are only used to explain this application, not to limit this application. It should be noted that, for ease of description, only the parts related to this application are shown in the accompanying drawings. Other related parts can be referred to the general description. In the absence of conflict, the embodiments and technical features in the embodiments of this application can be combined with each other to obtain new embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0027] Furthermore, although the terminology used in this invention is selected from commonly known and used terms, some terms mentioned in this specification may have been selected by the applicant in his or her judgment, and their detailed meanings are explained in the relevant sections of the description herein.

[0028] Furthermore, the invention should be understood not only through the actual terminology used, but also through the meaning implied by each term.

[0029] Rotor dynamics analysis was performed on the rotor assembly designed with the elastic support of the squirrel cage to confirm the required range of overall stiffness of the squirrel cage (e.g., 1×10⁻⁶). 4 N / mm - 5×10 4 N / mm).

[0030] Based on the interface between the squirrel cage device and the bearing housing and rotor assembly, the material and geometric parameters of the squirrel cage elastic support are initially selected, including but not limited to the material elastic modulus, the length of the squirrel cage bars, the number of squirrel cage bars, and the cross-sectional parameters of the bars.

[0031] Figure 6 This is a design flowchart for the present invention. When the cross-section of the cage bars is approximated as a trapezoid, its fatigue strength can be calculated using the formula [σ = 3Eu(a² + b²)]. 0 · 5 The calculation is performed using [ / L²], where u is the radial deformation.

[0032] By approximating the cross-section of the cage bars as a trapezoid, the overall stiffness of the elastic support of the squirrel cage can be preliminarily estimated using the formula [K = NEab(a²+b²) / 2L³]. Where: a is the length of the long side of the trapezoidal cross-section of the cage bar; b is the length of the short side of the trapezoidal cross-section of the cage bar; L is the length of the cage bar; N is the number of cage bars; and E is the elastic modulus of the material.

[0033] Preferably, the "whale-swallowing" optimization algorithm is adopted, with the minimization of the fatigue strength of the mouse cage as the objective function, which can be calculated according to the formula [σ = 3Eu(a² + b²)]. 0 · 5 The calculation is performed using [ / L²]. Here, u represents the radial deformation. The stiffness value obtained in step (0032) can be used as the initial constraint, and its fluctuation range (e.g., 10%) can be set. The structural parameter values ​​(a, b, L, N) of the squirrel cage are used as the optimization parameter combination to begin optimization.

[0034] Based on the optimized parameters obtained in step (0033), a clamp-free squirrel cage model and finite element analysis are performed. When the stiffness results of the finite element simulation do not meet the design specifications ([0.9K)... min 1.1K max When the amplification factor is adjusted, the iteration should be repeated.

[0035] Based on the iterative optimization results obtained in step (0034), obtain the required cage parameters and start designing the clamp parameters.

[0036] Please see Figure 1 and Figure 2The figures show a three-dimensional schematic diagram of the cage and a partial schematic diagram of the clamp of the present invention. In the figures: 1. Flange face; 2. Cage bar; 3. Clamp; 4. Spring assembly; 5. Fastener.

[0037] Figure 3 The diagram and cross-sectional view of the rat cage structure of the present invention show that the lower contact surface of the clamp (3) is fitted with the outer ring of the rat cage, and the inner side of the lower protrusion at the left and right ends of the clamp (3) can be fitted with the side of the cage bar (2). The outer side of the spring assembly (4) is wrapped with a lightweight hollow plastic tube, and the inner side is equipped with a steel spring. The fastener serves to fix the clamp (3) to the cage bar (2). The stiffness of the clamp (3) can be finely adjusted by applying a pre-tightening force to the fastener (5) to ensure the tightness of the clamp (3) and the cage bar (2).

[0038] like Figure 3 The modeling and finite element simulation of the assembled ring clamp squirrel cage are shown, and it is determined that it meets the design requirements [K>5K]. 整体 The range of values ​​for the axial position, thickness t, and spacing c of the clamp (3).

[0039] Figure 4 The diagram shows an example of the "integral ring" clamp cage of the present invention. The range of values ​​for the clamp (3) gap t1 that meets the requirements and the maximum number of spare parts for the integral ring clamp are determined by sensitivity simulation.

[0040] Based on the results of steps (0038) and (0039), a spare part plan for clamp (3) is formulated. The overall stiffness range must meet the design stiffness variation margin [0%~500%] requirement when replacing clamp (3) according to engineering experience.

[0041] Figure 5 This is a schematic diagram of an example of the "local" clamp-type rat cage of the present invention. Finite element simulation was used to determine that it meets the design stiffness requirement [0.5K]. 整体 1.5K 整体 The range of values ​​for the axial position, clearance t1, and chord length L1 of the clamp (3).

[0042] Using the finite element method, the maximum displacement U of the journal under gravity and unbalanced forces is estimated. max And determine a spare parts scheme that includes information such as the location of the clamps to supplement local stiffness and the number of spare clamps.

[0043] The test or operation can be carried out according to the scheme determined in steps (0040) and (0042), and the combination of processed clamps (3) spare parts (whole ring type, partial type, whole ring + partial type) can be adjusted as appropriate to adjust the actual stiffness of the squirrel cage elastic support device to the optimal.

[0044] During the adjustment of clamp (3), the preload of fastener (5) needs to be adjusted to a suitable value, and the stiffness of the squirrel cage can be finely adjusted. When using a full-ring clamp, the spring assembly is in a compressed state. When using a partial arc clamp, the spring assembly is in a stretched state.

Claims

1. An elastic support device for a squirrel cage with adjustable stiffness, the structural features of which include a flange face (1), cage bars (2), clamps (3), spring assembly (4) and fasteners such as bolts, nuts, and washers (5).

2. A stiffness-adjustable squirrel cage elastic support device, the design process of which includes: initially estimating the overall stiffness based on theoretical formulas, then further determining the range of squirrel cage parameters using a whale-swallowing optimization algorithm, and combining finite element simulation method to determine the structural parameters of components such as the squirrel cage and clamps and the reasonable number of spare parts.

3. The adjustable stiffness elastic support device for a squirrel cage according to claim 1, characterized in that: The flange face (1) is machined with bolt holes and is connected to the mounting surface of the rotor interface.

4. The adjustable stiffness elastic support device for a squirrel cage according to claim 1, characterized in that: The cage bars (2) are evenly distributed circumferentially, and their roots are designed with rounded corners, which are the core part that contributes to the overall fixed bending stiffness of the elastic support device of the rat cage.

5. The adjustable stiffness elastic support device for a squirrel cage according to claim 1, characterized in that: The clamps (3), spring assembly (4) and fasteners (5) are adjustable stiffness parts. During the rotor dynamic balancing test or trial operation, the overall stiffness of the squirrel cage elastic support can be adjusted by adjusting the distribution form and number of clamps.

6. In the adjustable stiffness elastic support device for a rat cage according to claim 1, preferably, the lower contact surface of the clamp (3) is in contact with the outer ring wall of the rat cage, and the inner side of the lower protrusion at the left and right ends of the clamp can be in contact with the side of the cage bar (2).

7. In a preferred embodiment of the adjustable stiffness squirrel cage elastic support device according to claim 1, the spring assembly (4) is wrapped with a lightweight hollow plastic tube on the outside and fitted with a steel spring on the inside.

8. In the adjustable stiffness squirrel cage elastic support device according to claim 1, preferably, the fastener serves to fix the clamp (3) to the cage bars (2). A preload can be applied to the fastener (5) to ensure a tight fit between the clamp (3) and the squirrel cage bars (2).

9. The design process of an adjustable stiffness squirrel cage elastic support device according to claim 2 is as follows: (1) Modal analysis of the rotor assembly is performed using the finite element method to estimate the stiffness fluctuation range of the squirrel cage elastic support that meets the critical speed requirement (avoiding the range of 20% of the rotor operating speed). (2) Assuming the cage bar cross section is trapezoidal, based on the cage stiffness theory formula and the stiffness range obtained in step (1), estimate the cage parameters (cage bar length, cage bar cross section size, number of cage bars, etc.) that meet the overall stiffness of the cage elastic support when there are no components such as clamps. (3) Based on the overall stiffness results of step (2), the "whale swallowing" algorithm is preferred as the multi-objective optimization algorithm. According to the theoretical formula of the fatigue strength of the squirrel cage and with its minimization as the objective function, the stiffness value obtained in step (2) can be used as the initial constraint condition, and its fluctuation range (e.g., 10%) can be set. The structural parameter values ​​of the squirrel cage are used as the optimization parameter combination to start the optimization. (4) The cage parameters obtained in step (3) are used to model the cage. Based on the stiffness fluctuation range in step (1), the two clamp types, "full ring" and "local", are analyzed and the corresponding clamp structure parameters, quantity and distribution form are determined. (5) Develop a stiffness adjustment plan based on the results of step (4) and carry out the processing; (6) During testing or operation, based on the actual fluctuation range of the rotor assembly stiffness, the appropriate stiffness value of the squirrel cage elastic support is linearly adjusted according to the predetermined scheme obtained in step (5).

10. As described in claim 9, when a full-ring clamp is used, the spring assembly is in a compressed state; when a partial clamp is used, the spring assembly is in a stretched state. The predetermined scheme for achieving a suitable stiffness value can be achieved by adjusting the number of clamps or the clamp combination (full-ring, partial, full-ring + partial) as appropriate.

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