Optimization design method of common support structure based on dynamic vibration absorption

Abstract

The application discloses an optimization design method of a common support structure based on dynamic vibration absorption, and takes a transition section of a gas generator rotor and a common support structure as a dynamic vibration absorber of a power turbine rotor, so that dynamic vibration absorption among engine components is realized through a stiffness matching method, stable operation of the engine in a full speed range is realized without increasing the structure weight, and the problem of heat stress concentration of outer supports of the transition section of the common support structure is solved, wherein the method comprises the following steps: determining a mode to be optimized and a node to be optimized of a common support structure double-rotor system, selecting a key stiffness of the common support structure and a selection principle, and using a common support structure stiffness combination optimization reference diagram, and finally obtaining the key stiffness of the common support structure double-rotor system, which is the optimized common support structure double-rotor system, and the common support structure double-rotor system has obvious advantages in reducing vibration of the power turbine rotor, fully utilizes the existing structure of the aero-engine, and is beneficial to improving the power-weight ratio and the thrust-weight ratio of the aero-engine.

Description

Technical Field

[0001] This invention relates to the field of aero-engine design and vibration control, specifically a design optimization method for the internal stiffness of a shared support structure, used for vibration reduction design of aero-engines with this structure. Background Technology

[0002] In recent years, the shared support structure, where the power turbine rotor and gas generator rotor share a common load-bearing frame, has been widely used in new-generation turboshaft engines. This structure effectively shortens the axial length of the turboshaft engine and reduces exhaust losses, thus becoming an important means of weight reduction and improving the power-to-weight ratio. However, because the shared support structure is located between the gas generator turbine and the power turbine, the high ambient temperature during operation leads to a weakening of the support stiffness. Furthermore, since the shared support structure simultaneously supports the gas generator rotor and the power turbine rotor, which operate at different speeds, vibration coupling between the rotors can occur. In common turboshaft engines, the gas generator rotor is generally a quasi-rigid rotor with a squeeze film damper, exhibiting only translational and pitch modes within its operating speed range. During operation, the squeeze film damper provides significant vibration reduction, and vibration problems are relatively easy to solve. However, the power turbine rotor of a turboshaft engine generally has a large length-to-diameter ratio, and the turbine disk is usually located at one end of the rotor. Within its operating range, it needs to traverse multiple bending modes, and the mode nodes often fall at the location of the squeeze film damper, causing the damper to lose its vibration reduction effect. Therefore, compared with the vibration of the gas generator rotor, the vibration problem of the power turbine rotor is more prominent and more complex, and has always been a difficult problem in the design of turboshaft engines.

[0003] Currently, the mainstream design method for shared support structures is to preset the critical speed of the rotor system based on the engine's operating speed, and then design the stiffness of the rotor support based on the critical speed and rotor geometry. In a typical dual-rotor system with shared support, in order to prevent the vibrations of the two rotors from interfering with each other and coupling, resulting in stronger vibration signals, the design generally adopts the method of enhancing the stiffness of the external support of the shared support structure. This makes the stiffness of the external support of the shared support structure much higher than the stiffness of other supports in the rotor, so as to isolate the vibration between the two rotors. This design method is called the decoupling design method for dual-rotor systems.

[0004] However, in their article "Key Technologies for the Design of Interstage Support Structure of Turbine Shaft Engine [J]" (Aero Engine), 2014, 40(4):7. (DOI:10.13477 / j.cnki.aeroengine.2014.04.007), Ma Yanhong, Cao Chong, et al. proposed that to reduce the temperature sensitivity of the shared support structure, improve the weakening of support stiffness and thermal stress concentration caused by the shared support structure in high-temperature working environments, and ensure low stress distribution and stable support stiffness under variable temperature conditions, it is extremely important. One of the main methods is to reduce the external support stiffness of the shared support structure to reduce thermal stress and stiffness stability. Therefore, it is evident that the design requirement of reducing the external support stiffness of the shared support structure conflicts with the design concept of improving the external support stiffness of the shared support structure in the decoupling design method.

[0005] Regarding the research on the coupling characteristics of shared support structures, a representative work is the paper "Research on Coupled Vibration Characteristics of Bearing Common Cavity-Dual Rotor System" by Tang Zhenhuan, Mi Dong, et al. [J]. Propulsion Technology, 2022(002):043. Taking a certain type of advanced civilian turboshaft engine with a shared support structure as an example, they established a corresponding nonlinear dynamic model. Through simulation analysis, they concluded that the coupled vibration of the dual rotor system with a shared support structure mainly manifests as the cross-excitation phenomenon between the two rotors. The angular stiffness of the support structure has a significant impact on the coupled vibration. Shortening the axial distance between the inner and outer mounting edges of the common cavity structure can improve the angular stiffness and weaken the coupled vibration. (Hong Jie, Yang Zhenchuan, Wang Yong...) In their paper "Vibration Isolation Design Method and Experiment of Load-Bearing Structure of Aero-Engine [J]. Journal of Beijing University of Aeronautics and Astronautics, 2019(1):8." (DOI:10.13700 / j.bh.1001-5965.2018.0196), Feng et al. took the load-bearing frame of the common support structure of a turboshaft engine as the object. They discretized the common support structure into multiple different structural units and analyzed the vibration transmission characteristics and vibration transmission coefficient between the common support structure and the turbine casing through numerical simulation and experiments. They utilized the discontinuous design of the plate shell support structure to achieve a large mechanical impedance and good vibration isolation performance within the structure.

[0006] In summary, reducing the vibration of a dual-rotor system requires increasing the stiffness of the shared support structure's squirrel-cage drum to decouple the power turbine rotor and the gas generator rotor. Conversely, improving the system's stiffness stability necessitates reducing the stiffness of the shared support structure's squirrel-cage drum as the point of minimum stiffness and stress relief. Regardless of the design, it's difficult to simultaneously meet both engineering requirements; a compromise must be made. Therefore, this invention proposes a method for optimizing the design of a dual-rotor system with a shared support structure using the fundamental principles of dynamic vibration absorbers.

[0007] Currently, the types of dynamic vibration absorbers used for rotating structures include the following. He Lidong, Zhang Zhenkun, and others proposed a hydraulic multi-frequency dynamic vibration absorber for rotating machinery rotors in their invention application CN201310163488.5. This absorber uses liquids such as oil or water to fill the tuned body, changing the mass of the tuned body, and achieves dynamic vibration absorption over a wide frequency range by changing the mass of the tuned body in real time through a control system. The advantages of this patent are a wide absorption frequency range and good absorption effect; the disadvantages are the need for an additional liquid supply device and control system on the equipment, a larger weight, and a more complex design and control process. Yao Hongliang, Cao Yanbo, and others proposed a rotor system dynamic vibration absorber utilizing a nonlinear energy trap mechanism in their invention application CN201810125902.6. Its structure includes a vibration absorber body and a support component fixing device. The vibration absorber body includes a support assembly, a connecting assembly, and a vibration-absorbing mass block. The support assembly includes bearings, supports, and bushings; the connecting assembly includes nuts, connecting rods, and piecewise linear rods, etc., capable of fitting nonlinear cubic stiffness to achieve passive control. The advantages of this invention are its small added mass and high reliability, requiring no external energy source or additional control mechanism. The disadvantages are the relatively complex structure of the vibration absorber itself, the greater design difficulty, and the need to add additional components to the rotor system. There are many similar patents for dynamic vibration absorbers, but they all require the addition of additional components or control systems, and the tuning mass is always a non-rotating part. Currently, there is no existing literature on dynamic vibration absorption design methods utilizing existing structural components and rotating structures. Summary of the Invention

[0008] To overcome the shortcomings of existing technologies that cannot simultaneously meet the engineering requirements of reducing vibration and improving stiffness and stability of dual-rotor systems, this invention proposes an optimized design method for a shared support structure based on dynamic vibration absorption.

[0009] The specific process of this invention is as follows:

[0010] Step 1: Determine the modes and nodes to be optimized in the dual-rotor system with shared support structure:

[0011] Determine the non-adjustable parameters of the dual-rotor system with a shared support structure.

[0012] The non-adjustable parameters of the shared support structure dual-rotor system include the geometric dimensions and material parameters of the power turbine rotor, the stiffness of the front support point of the power turbine rotor, the dimensions and material parameters of the gas generator rotor, and the dimensions and material parameters of the transition section of the shared support structure; each parameter is obtained based on the engine aerodynamic design and spatial dimension technical specifications.

[0013] The stiffness of the front support point of the gas generator, the stiffness of the rear support point of the gas generator, and the stiffness of the external support of the common support structure are each assigned a rigid support stiffness, the value of which is 1×10. 8 N / m. The initial imbalance of the disc structure closest to the common support structure of the gas generator rotor; the initial imbalance is 5 g·cm.

[0014] The unadjusted parameters of the dual rotor system with shared support structure, the support stiffness of the front support point of the gas generator, the support stiffness of the rear support point of the gas generator, the support stiffness of the external support of the shared support structure, and the initial unbalance of the disk structure are substituted into the one-dimensional finite element method to calculate the strain energy ratio of each structural component corresponding to each mode of the dual rotor system with shared support structure in the operating speed range, as well as the unbalance response amplitude of the key structural components of the power turbine rotor in the operating speed range.

[0015] Among the strain energy proportions of each structural component corresponding to each of the various modes, the mode with the highest proportion of strain energy of the power turbine rotor shaft to the total strain energy is the mode to be optimized in the dual-rotor system with shared support structure. At the mode to be optimized, the structural component with the largest unbalanced response amplitude is the node to be optimized in the power turbine rotor of the dual-rotor system with shared support structure.

[0016] Step 2, determine the stiffness of the front support point of the gas generator:

[0017] The stiffness of the front support of the gas generator is the lowest usable stiffness that the spring support of the front support of the gas generator can physically achieve.

[0018] Factors affecting the stiffness of the cage spring support, which serves as the front fulcrum, include the material of the cage spring support, the length of the cage bars, the number of cage bars, the width of the cage bars, the cross-section of the cage bars, and the rounding dimensions at the base of the cage bars.

[0019] When determining the stiffness of the rat cage spring support structure:

[0020] Ⅰ. Select the material for the rat cage spring support.

[0021] II. According to the design requirements, the length of the spring support at the front support of the gas generator is determined based on the axial spatial dimensions at the front support of the gas generator. The minimum number of cage bars is selected based on the material strength and the requirements of the aero-engine design manual; the selected number of cage bars for this squirrel cage spring support is ≥8; the width of the cage bars is determined to be ≥5mm according to design requirements.

[0022] Ⅲ. Determine the minimum rounding radius at the root of the cage bars based on the allowable stress of the material. The selected minimum rounding radius at the root of the cage bars is ≥5mm.

[0023] IV. Determine the material of the cage spring supports and the cross-section of the cage bars according to the design requirements. The cross-section of the cage bars includes the cross-sectional area, cross-sectional moment, and cross-sectional shape of the cage bars.

[0024] V. Based on the determined material of the cage spring support, the length of the cage bars, the number of cage bars, the width of the cage bars, the cross-section of the cage bars, and the radius of the rounded corner at the root of the cage bars, the minimum usable stiffness of the front support of the gas generator is obtained through simulation calculation using commercial software such as ANSYS, NX, Abaqus, or NASTRAN. This minimum usable stiffness of the front support of the gas generator is the stiffness of the front support of the gas generator selected in this invention.

[0025] Step 3: Determine the range of values ​​for the stiffness of the rear support point of the gas generator:

[0026] The upper limit of the stiffness range of the rear support point of the gas generator is the stiffness of the bearing model at the rear support point of the gas generator.

[0027] The upper limit of the stiffness range of the rear support point of the gas generator is 2×10. 7 N / m. The lower limit of the stiffness range for the rear support of the gas generator is the lowest usable stiffness that the spring support of the rear support of the gas generator can physically achieve. Its selection method is the same as that for the front support stiffness of the gas generator in step 2. To ensure rotor stability, the lower limit of the stiffness of the rear support of the gas generator should be greater than or equal to 5 × 10 N / m. 5 N / m.

[0028] Step 4: Determine the range of values ​​for the external support stiffness of the shared support structure:

[0029] The upper limit of the stiffness value of the external support of the shared support structure is the decoupling stiffness of the dual-rotor system of the shared support structure; this decoupling stiffness should be 10 times the upper limit of the stiffness value of the rear support of the gas generator. The lower limit of the range of values ​​for the external support stiffness of the shared support structure should be the lowest usable stiffness that the shared support structure can physically achieve, and its selection method is the same as the method for determining the stiffness of the front support of the gas generator in step 2. The external support stiffness of the shared support structure is greater than or equal to 5 × 10⁻⁶. 6 N / m.

[0030] Step 5: Calculate the unbalanced response of the dual-rotor system with shared support structure under different stiffness combinations:

[0031] The different stiffness combinations mentioned are combinations of the rear support stiffness of the gas generator and the external support stiffness of the common support structure.

[0032] When determining the stiffness value of the rear support point of the gas generator, the lower limit of 5 × 10⁻⁶ determined in step 3 is used. 5 Starting with N / m, and using 1×10 6 The N / m increments are gradually increased until all stiffness values ​​between the lower and upper limits of the rear support stiffness of the gas generator are obtained, with the interval between all the obtained stiffness values ​​being 1×10. 6 N / m.

[0033] When incrementing sequentially, an arithmetic sequence is generated by starting with an initial value and using a step size as the interval.

[0034] All stiffness values ​​between the lower and upper limits of the obtained gas generator rear support stiffness are combined with all stiffness values ​​between the lower and upper limits of the external support stiffness of the common support structure to obtain all stiffness combinations to be solved. The specific process of pairwise combination is as follows: the upper limit value of the stiffness of the rear support of the gas generator is combined with all stiffness values ​​between the lower limit and the upper limit value of the stiffness of the outer support of the common support structure to obtain the first set of pairwise combination points; then, adjacent values ​​of the upper limit value of the stiffness of the rear support of the gas generator are combined with all stiffness values ​​between the lower limit and the upper limit value of the stiffness of the outer support of the common support structure to obtain the second set of pairwise combination points; the process of obtaining the first set of pairwise combination points and obtaining the second set of pairwise combination points is repeated to complete all stiffness combinations to be solved, that is, to complete the combination of each value of the stiffness of the rear support of the gas generator with all stiffness values ​​between the lower limit and the upper limit value of the stiffness of the outer support of the common support structure, forming a two-dimensional array composed of the stiffness of the gas generator and the outer support of the common support structure.

[0035] Substitute all the stiffness combinations to be solved, the front support stiffness of the gas generator obtained in step 2, and the unadjusted parameters of all the shared support structure dual rotor systems obtained in step 1 into the one-dimensional finite element method to obtain the unbalanced response of the node to be optimized in the mode to be optimized of the shared support structure dual rotor system; this unbalanced response is the unbalanced response of the shared support structure dual rotor system under different stiffness combinations.

[0036] Step 6: Establish a reference diagram for the stiffness combination optimization of the shared support structure.

[0037] The reference diagram for optimizing the stiffness combination of the shared support structure includes three dimensions, with the dependent variable distributed as a surface. Its specific establishment process is as follows:

[0038] I. Establish a spatial rectangular coordinate system

[0039] The spatial rectangular coordinate system includes three dimensions: x-axis, y-axis, and z-axis. Specifically: the x-axis represents the stiffness K4 of the rear support point of the gas generator, in N / m; the y-axis represents the stiffness K of the external support of the shared support structure. g The unit is N / m; the z-axis represents the unbalanced response of the dual rotor system with shared support structure to be optimized, as well as the unbalanced response of the nodes to be optimized.

[0040] The x-axis coordinate range is the lower to upper limit of the range of the stiffness of the rear support of the gas generator rotor; the y-axis coordinate range is the lower to upper limit of the range of the stiffness of the external support of the common support structure; the z-axis coordinate range is determined by drawing step II.

[0041] II. Plot the rotor unbalance response surface:

[0042] The unbalance response of the dual rotor system with shared support structure under the mode to be optimized and the node to be optimized under the excitation of 5 g·cm unbalance is calculated by the one-dimensional finite element method for each stiffness combination to be solved in step 5. The unbalance response is plotted in the coordinate system according to the x and y axis coordinates corresponding to the unbalance response.

[0043] Constructing grid curves enhances the readability of the unbalanced response surface. Specifically, the process involves connecting identical unbalanced response points along the x-axis using a curve parallel to the x-axis, and connecting identical unbalanced response points along the y-axis using a curve parallel to the y-axis. The z-axis ranges from the minimum to the maximum unbalanced response value.

[0044] III. Draw the optimal stiffness line

[0045] Select the point with the lowest z-axis value for each grid curve parallel to the x-axis; connect the selected data points to obtain the optimal value line for the stiffness of the rear support of the gas generator. This optimal value line for the stiffness of the rear support of the gas generator is also the optimal value line for stiffness K4.

[0046] Select the point with the lowest z-axis value for each grid curve parallel to the y-axis; connect these data points to obtain the optimal stiffness line for the shared support structure. This optimal stiffness line for the shared support structure is the stiffness K. g The optimal value line.

[0047] Using the curve concave point definition method, points located on each grid line parallel to the y-axis and whose z-coordinates are lower than the z-coordinates of the two points on either side are selected as concave points of the curve; connecting the concave points of the curve yields the suboptimal value line of the stiffness of the shared support structure.

[0048] Step 7, Determine the stiffness:

[0049] The stiffness is divided into optimal stiffness and suboptimal stiffness.

[0050] The optimal stiffness is determined by the intersection of the optimal stiffness line of the rear support of the gas generator and the optimal stiffness line of the common support structure, or the suboptimal stiffness is determined by the intersection of the optimal stiffness line of the rear support of the gas generator and the suboptimal stiffness line of the common support structure.

[0051] When the rear support point of the gas generator and the shared support structure, the squirrel-cage drum, are structurally unconstrained and can be designed freely:

[0052] The intersection point of the optimal stiffness curve of the rear support point of the gas generator and the optimal stiffness curve of the squirrel-cage drum of the shared support structure is selected. This intersection point is taken as the optimal combination of the stiffness of the rear support point of the gas generator and the stiffness of the external support of the shared support structure in the dual-rotor system. The stiffness of the rear support point of the gas generator, the stiffness of the external support of the shared support structure, and the stiffness of the front support point of the gas generator rotor are the optimal stiffness of each support point after optimization in the dual-rotor system of the shared support structure. When the stiffness of the rear support point of the rotor gas generator, the stiffness of the external support of the shared support structure, and the stiffness of the front support point of the gas generator rotor all adopt the optimal stiffness of this support point, the gas generator rotor achieves the maximum dynamic vibration absorption efficiency.

[0053] When interference occurs between the engine fuel supply line and accessory transmission structure and the shared support structure (squirrel cage drum structure), resulting in the intersection of the optimal stiffness value line 16 of the gas generator rear support and the optimal stiffness value line curve 17 of the shared support structure (squirrel cage drum) being impractical in engineering:

[0054] When the intersection of the optimal stiffness curve of the rear support of the gas generator and the optimal stiffness curve of the squirrel cage drum of the common support structure is not feasible in engineering, the intersection of the optimal stiffness curve of the rear support of the gas generator and the suboptimal stiffness curve of the squirrel cage drum of the common support structure shall be taken as the suboptimal stiffness combination of the dual rotor system of the common support structure; when the rotor adopts the above stiffness, the gas generator rotor achieves the suboptimal dynamic vibration absorption efficiency.

[0055] This completes the optimized design of the shared support structure based on dynamic vibration absorption.

[0056] This invention uses the transition section of the gas generator rotor and the common support structure as a dynamic vibration absorber for the power turbine rotor. It achieves dynamic vibration absorption between engine components through a stiffness matching design method. All vibration-absorbing components are existing components on the engine. Without increasing the structural weight, the engine can operate stably across the entire speed range. It can also solve the problem of thermal stress concentration on the outer support of the transition section of the common support structure.

[0057] This invention includes the determination method of the modes to be optimized and the nodes to be optimized of a dual-rotor system with a shared support structure, the selection method and selection principle of the key stiffness of the shared support structure, and the reference diagram for the combination optimization of the stiffness of the shared support structure to be used. Finally, the key stiffnesses selected are the dual-rotor system with a shared support structure optimized by this design optimization method.

[0058] The method for determining the modes and nodes to be optimized involves determining the non-adjustable parameters of the dual-rotor system with a shared support structure. These non-adjustable parameters include the geometric dimensions and material parameters of the power turbine rotor, the stiffness of the front support point of the power turbine rotor, the dimensions and material parameters of the gas generator rotor, and the dimensions and material parameters of the transition section of the shared support structure. These parameters generally depend on the engine's aerodynamic design and spatial dimensional specifications, similar to conventional aero-engine design methods, and are unrelated to the optimization method described in this study. Rigid support stiffness is assigned to the front support point, rear support point, and rear support point of the gas generator; typically, the rigid support stiffness value is 1 × 10⁻⁶. 8 N / m. Given an initial unbalance, typically 5 g·cm, substitute the above data and use the one-dimensional finite element method from Liao Mingfu's textbook "Rotor Dynamics" published by Northwestern Polytechnical University Press to calculate the strain energy ratio of each structural component corresponding to each mode in the shared support structure dual-rotor system within the operating speed range, as well as the unbalance response amplitude of the key structural components of the power turbine rotor within the operating speed range. The strain energy ratio should include the proportion of strain energy of the power turbine rotor shaft to the total strain energy, the proportion of strain energy of the gas generator rotor shaft to the total strain energy, the proportion of strain energy with the front and rear supports of the rotor to the total strain energy, and the proportion of strain energy of the squirrel cage drum of the shared support structure to the total strain energy. The key structural components of the unbalance response are the power turbine rotor disk, the front and rear supports of the power turbine, and the midpoint of the span of the power turbine shaft, i.e., the midpoint of the line connecting the two farthest adjacent bearings on the power turbine shaft. Among the strain energy proportions of each structural component corresponding to each mode, the first mode with the highest proportion of strain energy to total strain energy of the power turbine rotor shaft is the mode to be optimized in the dual-rotor system with shared support structure. At the mode to be optimized, the structural component with the largest unbalanced response amplitude is the node to be optimized in the power turbine rotor of the dual-rotor system with shared support structure.

[0059] The key stiffness of the shared support structure includes three key stiffnesses: the stiffness of the front support point of the gas generator, the stiffness of the rear support point of the gas generator, and the stiffness of the external support of the shared support structure.

[0060] The principle for selecting the stiffness of the gas generator's front support point is that the stiffness should be the lowest usable stiffness that the gas generator's front support spring can physically achieve. Here, we take the squirrel cage spring support structure, the most common structure in aero-engine support design, as an example to introduce the selection process for the lowest usable stiffness. The stiffness influencing factors of the squirrel cage spring support structure include the material of the squirrel cage spring support, the length of the cage bars, the number of cage bars, the width of the cage bars, the cross-section of the cage bars, and the rounding dimensions at the base of the cage bars. First, the material of the spring support is selected based on the operating temperature of the spring support and the processing conditions of the manufacturing plant; this is the same as the material selection method for conventional engines. Second, the length of the gas generator's front support spring support is selected based on the axial spatial dimensions at the gas generator's front support point. The minimum number of cage bars is selected based on the material's strength and the requirements of the aero-engine design manual; generally, the minimum number of cage bars should not be less than eight. The width of the cage bars is selected based on the material's heat treatment requirements and processing conditions; this needs to be determined based on the designer's experience. Then, the minimum rounding dimension at the root of the cage bars is selected based on the allowable stress of the material. When selecting this dimension, it should be ensured that the stress at the root of the cage bars does not exceed the allowable stress of the material; generally, the rounding radius at the root of the cage bars should not be less than 5mm. Finally, based on the selected influencing factor parameters, the minimum usable stiffness of the front support of the gas generator is obtained through simulation calculation using commercial software such as ANSYS or NX. This minimum usable stiffness is the front support stiffness of the gas generator selected in this invention.

[0061] The stiffness of the rear support point of the gas generator and the stiffness of the external support of the common support structure are a set of combined parameters. It is necessary to first determine the range of values ​​for the two stiffness parameters, and then select them according to the reference diagram of the combined stiffness of the common support structure in the patent within the range of values.

[0062] The range of stiffness values ​​for the rear support point of the gas generator is determined by the upper and lower limits of the stiffness value for the rear support point. The upper limit of the stiffness value is the stiffness of the bearing model at the rear support point of the gas generator, which is given by the bearing manufacturer at the time of bearing delivery. The lower limit of the stiffness value is the lowest usable stiffness that the spring support of the rear support point of the gas generator can physically achieve, and its selection method is the same as the selection principle for the stiffness of the front support point of the gas generator.

[0063] The external support of the shared support structure is a general term for the external supports of the transition section of the shared support structure, including the turbine guide bearing spokes and the squirrel cage drum of the shared support structure. Its stiffness is the series stiffness of the turbine guide bearing spokes and the squirrel cage drum of the shared support structure. The range of stiffness values ​​is determined by the upper and lower limits of the stiffness values ​​of the external supports of the shared support structure. The upper limit of the stiffness value is the decoupling stiffness of the dual-rotor system of the shared support structure, and should be 10 times the upper limit of the stiffness value of the rear support point of the gas generator. For example, when the upper limit of the stiffness value of the rear support point of the gas generator is 1×10... 8 When N / m, the upper limit of the stiffness value of the external support of the shared support structure is 1×10. 9N / m. The lower limit of the stiffness value should be the lowest usable stiffness that the squirrel-cage drum of the shared support structure can physically achieve, and its selection method is the same as the selection principle of the front support stiffness of the gas generator. To ensure rotor stability, the external support stiffness of the shared support structure should not be less than 5 × 10 N / m. 6 N / m.

[0064] The reference diagram for optimizing the stiffness combination of the shared support structure serves as the basis for selecting the optimal combination of the stiffness of the rear support point of the gas generator and the stiffness of the external support of the shared support structure. For example... Figure 3 As shown, the reference diagram for stiffness combination optimization of the shared support structure includes three dimensions, with the dependent variable distributed as a curved surface. Its specific constituent elements include a spatial rectangular coordinate system, a rotor unbalanced response surface, and stiffness combination value lines.

[0065] The spatial rectangular coordinate system includes three dimensions: the x-axis, the y-axis, and the z-axis. The x-axis represents the stiffness of the rear support point of the gas generator rotor, denoted by K4, with units of N / m. Its value ranges from the lower limit to the upper limit of the range described in step 4 for the stiffness of the rear support point of the gas generator rotor. The y-axis represents the stiffness of the rear support point of the gas generator rotor, denoted by K. g The unit is N / m, and the value range is from the lower limit of the value range of the external support stiffness of the shared support structure described in step 5 to the upper limit of the value range of the external support stiffness of the shared support structure. The coordinate of the z-axis is the unbalanced response of the dual rotor system of the shared support structure to be optimized and the node to be optimized in step 1. The coordinate axis range is selected according to the stiffness value range selection method given in steps 4 and 5. The x-axis coordinate range is the stiffness value range of the rear support of the gas generator, the y-axis coordinate range is the stiffness range of the external support of the shared support structure, and the z-axis coordinate range is selected by the maximum and minimum values ​​of the rotor unbalanced response surface.

[0066] The rotor unbalance response surface is a surface formed by the response amplitudes of the nodes to be optimized in a dual-rotor system with a shared support structure under different stiffness combinations at the order to be optimized. The specific drawing method is as follows. In K4 and K... gWithin the stiffness range, 100 points were sampled at equal intervals. The one-dimensional finite element method proposed by Liao Mingfu in the textbook "Rotor Dynamics" published by Northwestern Polytechnical University Press was used to calculate the unbalanced response of the optimized node under a 5 g·cm unbalance excitation in the optimized mode for the shared support structure dual-rotor system under these 100x100 stiffness combinations. These unbalanced response points were then plotted in the coordinate system of drawing step I according to the coordinates of the unbalanced response values. Next, a mesh curve was constructed to enhance the readability of the unbalanced response surface. Specifically, unbalanced response points with the same x-axis coordinates were connected using a curve parallel to the x-axis, and unbalanced response points with the same y-axis coordinates were connected using a curve parallel to the y-axis. The z-axis ranged from the minimum to the maximum unbalanced response value.

[0067] The stiffness value lines include the optimal stiffness value line for the rear support of the gas generator, the optimal stiffness value line for the external support of the shared support structure, and the suboptimal stiffness value line for the external support of the shared support structure. Their plotting method is shown below. Connect the lowest points of each grid curve parallel to the x-axis, as shown below. Figure 3 Curve 16 in the figure shows the optimal value line for the stiffness K4 of the rear support of the gas generator. Connecting the lowest points of each grid line parallel to the y-axis, as shown... Figure 3 Curve 17 in the figure represents the stiffness of the shared support structure, i.e., stiffness K. g The optimal value line is obtained by selecting the points on each grid line parallel to the y-axis where the z-coordinate is lower than the z-coordinates of the two points on either side, i.e., the concave points of the curve, and connecting them gives the suboptimal value line for the stiffness of the shared support structure.

[0068] This invention uses a transition section between a gas generator rotor and a shared support structure as a dynamic vibration absorber for the power turbine rotor, and achieves dynamic vibration absorption between engine components through a stiffness matching design method.

[0069] The basic principle of this invention is to use the gas generator rotor as a dynamic vibration absorber for the power turbine rotor in a dual-rotor system with a shared support structure. Through a reasonable stiffness matching design, the vibration energy generated by the imbalance of the power turbine rotor is transferred to the front end of the gas generator rotor via the transition section of the shared support structure, where it is absorbed and dissipated by the gas generator rotor's compression oil film damper. Its advantage lies in utilizing only existing components of the dual-engine system with a shared support structure, without increasing structural weight, thus achieving economic efficiency.

[0070] After optimization by this invention, the design requirements for releasing thermal stress on the external support of the shared support structure can be met. All modes of the dual-rotor system are strongly coupled modes, and the squeeze film damper in the gas generator rotor can achieve high operating efficiency. Taking a dynamic similarity test apparatus for a dual-rotor turboshaft engine with a shared support structure as an example, the unbalanced response curve of the power turbine obtained by the decoupling design method is shown in Figure 19. Figure 4 As shown, the unbalanced response curve 22 of the power turbine optimized using the dynamic vibration absorption design optimization method of the present invention is as follows: Figure 4 As shown.

[0071] As shown in the image, the peak response of the dual-rotor system with a shared support structure designed by the optimization method of this invention is higher than that of the dual-rotor system with a shared support structure designed by the decoupling design method, although the peak response is significantly lower. Under an unbalanced excitation of 50 g·cm, the peak response of the power turbine of the rotor system designed by the method of this invention is 476.5 μm. Figure 4 The peak value of the unbalanced response of the power turbine obtained by the present invention is shown in the figure; the rotor system designed using the decoupling design method, under the same excitation and the same damper configuration, has a peak power turbine response of 2134 μm, as shown in the figure. Figure 4 The peak value of the unbalanced response of the power turbine obtained by the decoupling design method shown in the figure is 20. The peak vibration value of the rotor system obtained by the present invention is only 21.91% of the peak vibration value of the rotor system designed by the decoupling design method, and the vibration reduction effect is as high as 78.09%. It can be seen that the design optimization method proposed in this invention has significant advantages over the traditional decoupling design method in reducing the vibration of the power turbine rotor.

[0072] Compared with the technical solution disclosed in CN201310163488.5, the present invention does not require additional control and power supply systems, resulting in a simpler structure and lower cost. Compared with the technical solution disclosed in CN201810125902.6, the present invention makes full use of the existing structure within the aero-engine, eliminating the need for additional vibration damping structures and reducing the structural weight of the aero-engine, which is beneficial for improving the power-to-weight ratio / thrust-to-weight ratio of the aero-engine. Attached Figure Description

[0073] Figure 1 This is a simplified structural diagram of a dual-rotor system with a shared support structure.

[0074] Figure 2 This is a simplified cross-sectional diagram of the shared support structure.

[0075] Figure 3 This is an example of a reference diagram for optimizing the stiffness combination of a shared support structure.

[0076] Figure 4 This is a diagram showing the effect of the optimization method.

[0077] Figure 5 This is a flowchart of the present invention.

[0078] In the diagram: 1. Front support of the power turbine rotor; 2. Front support of the gas generator rotor; 3. Gas generator rotor; 4. Rear support of the gas generator rotor; 5. Common support structure; 6. Power turbine rotor; 7. Rear support spring of the gas generator; 8. Turbine guide bearing spoke; 9. Squirrel cage drum of the common support structure; 10. Rear support spring of the power turbine; 11. Transition section of the common support structure; 12. Rear support compression oil film damper of the gas generator; 13. Rear support bearing of the gas generator; 14. Rear support bearing assembly of the power turbine; 15. Rear support compression oil film damper of the power turbine. 16. Optimal value line for the stiffness of the rear support point of the gas generator; 17. Optimal value line for the stiffness of the squirrel cage drum of the shared support structure; 18. Suboptimal value line for the stiffness of the squirrel cage drum of the shared support structure; 19. Unbalanced response curve of the power turbine obtained by the decoupling design method; 20. Peak value of the unbalanced response of the power turbine obtained by the decoupling design method; 21. Peak value of the unbalanced response of the power turbine obtained by this invention; 22. Optimized unbalanced response curve of the power turbine. Detailed Implementation

[0079] This implementation example demonstrates the use of a dynamic vibration-damping-based design optimization method for a shared-support structure of a dual-rotor aero-engine to optimize stiffness. The specific process is as follows:

[0080] Step 1: Determine the modes and nodes to be optimized in the dual-rotor system with shared support structure:

[0081] The unadjustable parameters of the dual-rotor system with a shared support structure are determined. These unadjustable parameters include the geometric dimensions and material parameters of the power turbine rotor, the stiffness of the power turbine rotor's front support point, the dimensions and material parameters of the gas generator rotor, and the dimensions and material parameters of the transition section of the shared support structure. These parameters are obtained using conventional methods based on the engine's aerodynamic design and spatial dimensional specifications.

[0082] The stiffness of the front support point of the gas generator, the stiffness of the rear support point of the gas generator, and the stiffness of the external support of the common support structure are each assigned a rigid support stiffness, the value of which is 1×10. 8 N / m. The initial imbalance of the disc structure closest to the common support structure of the gas generator rotor; the initial imbalance is 5 g·cm.

[0083] The unadjusted parameters of the shared-support structure dual-rotor system, the support stiffness of the front support point of the gas generator, the support stiffness of the rear support point of the gas generator, the support stiffness of the external support of the shared-support structure, and the initial unbalance of the disk structure are substituted into the one-dimensional finite element method to calculate the strain energy ratio of each structural component corresponding to each mode of the shared-support structure dual-rotor system within the operating speed range, as well as the unbalance response amplitude of the key structural components of the power turbine rotor within the operating speed range. The one-dimensional finite element method is disclosed in the textbook *Rotor Dynamics*, edited by Liao Mingfu and published by Northwestern Polytechnical University Press.

[0084] The aforementioned modes refer to the critical speed values ​​for each positive precession obtained by the one-dimensional finite element method and the vibration mode of the rotor system at that critical speed. Each critical speed and its corresponding vibration mode together constitute a first-order mode.

[0085] The strain energy ratio should include the ratio of strain energy of the power turbine rotor shaft to the total strain energy, the ratio of strain energy of the gas generator rotor shaft to the total strain energy, the ratio of strain energy with rotor front and rear supports to the total strain energy, and the ratio of strain energy of the squirrel cage drum with shared support structure to the total strain energy.

[0086] The key structural components of the unbalanced response are the power turbine rotor disk, the front and rear supports of the power turbine, and the midpoint of the span of the power turbine shaft, which is the midpoint of the line connecting the two farthest adjacent bearings on the power turbine shaft.

[0087] Among the strain energy proportions of each structural component corresponding to each of the various modes, the mode with the highest proportion of strain energy of the power turbine rotor shaft to the total strain energy is the mode to be optimized in the dual-rotor system with shared support structure. At the mode to be optimized, the structural component with the largest unbalanced response amplitude is the node to be optimized in the power turbine rotor of the dual-rotor system with shared support structure.

[0088] Step 2, determine the stiffness of the front support point of the gas generator:

[0089] The stiffness of the front support of the gas generator is the lowest usable stiffness that the front support spring of the gas generator can physically achieve. In this embodiment, the front support spring of the gas generator is a squirrel cage spring structure.

[0090] The front support point of the gas generator refers to the location of the supporting structure. An aero-engine has at least two support points, front and rear; a squirrel cage is a structural form of support point. In this embodiment, the front support point of the gas generator is a squirrel cage structure.

[0091] In all aero-engines, the pivot points serve as supports for the rotor structure. The gas generator is part of the rotor structure. Since the rotor structure cannot levitate, pivot points are necessary to maintain its existence in space. These pivot points connect the rotor structure to the casing and are thus designated as the front and rear pivot points for the gas generator. The "Principles of Aero-engine Structure" defines the engine's forward and backward directions as follows: the intake direction is forward, and the exhaust direction is rearward.

[0092] The stiffness of the cage spring support, which serves as the front fulcrum, is affected by factors including the cage spring support material, cage bar length, number of cage bars, cage bar width, cage bar cross-section, and the rounded dimensions at the bar root. When determining the stiffness of this cage spring support structure:

[0093] I. Select the material for the rat cage spring support using conventional methods.

[0094] II. According to the design requirements, the length of the spring support at the front support of the gas generator is determined based on the axial spatial dimensions at the front support of the gas generator. The minimum number of cage bars is selected based on the material strength and the requirements of the aero-engine design manual; the selected number of cage bars for this squirrel cage spring support is ≥8; the width of the cage bars is determined to be ≥5mm according to design requirements.

[0095] Ⅲ. Determine the minimum rounding radius at the root of the cage bars based on the allowable stress of the material. The selected minimum rounding radius at the root of the cage bars is ≥5mm.

[0096] IV. Determine the material of the cage spring supports and the cross-section of the cage bars according to the design requirements. The cross-section of the cage bars includes the inner diameter, outer diameter, width at the outer diameter, and cross-sectional shape of the cage bars.

[0097] In this embodiment, the material of the cage spring is determined to be 65Mn; the inner diameter of the cage bar is determined to be 179mm, the outer diameter to be 185mm, the width at the outer diameter to be 6.07mm, and the cross-sectional shape and the cross-sectional shape of a single cage bar are fan-shaped.

[0098] V. Based on the determined material of the cage spring support, the length of the cage bars, the number of cage bars, the width of the cage bars, the cross-section of the cage bars, and the radius of the rounded corner at the root of the cage bars, the minimum usable stiffness of the front support of the gas generator is obtained through simulation calculation using commercial software such as ANSYS, NX, Abaqus, or NASTRAN. This minimum usable stiffness of the front support of the gas generator is the stiffness of the front support of the gas generator selected in this invention.

[0099] In this embodiment, the stiffness of the squirrel cage spring support, which serves as the front support point of the gas generator, is determined using ANSYS software.

[0100] Step 3: Determine the range of values ​​for the stiffness of the rear support point of the gas generator:

[0101] The upper limit of the stiffness range of the rear support point of the gas generator is the stiffness of the bearing model at the rear support point of the gas generator; this stiffness of the rear support point of the gas generator is provided by the bearing manufacturer; in this embodiment, the upper limit of the stiffness range of the rear support point of the gas generator is 2×10. 7 N / m. The lower limit of the stiffness range for the rear support of the gas generator is the lowest usable stiffness that the spring support of the rear support of the gas generator can physically achieve. Its selection method is the same as that for the front support stiffness of the gas generator in step 2. To ensure rotor stability, the lower limit of the stiffness of the rear support of the gas generator should be greater than or equal to 5 × 10 N / m. 5 N / m.

[0102] Step 4: Determine the range of values ​​for the external support stiffness of the shared support structure:

[0103] The upper limit of the stiffness value of the external support stiffness of the shared support structure is the decoupling stiffness of the dual-rotor system of the shared support structure; this decoupling stiffness should be 10 times the upper limit of the stiffness value of the rear support of the gas generator. When the upper limit of the stiffness value of the rear support of the gas generator is 1×10... 8 When N / m, the upper limit of the stiffness value of the external support of the shared support structure is 1×10. 9 N / m. The lower limit of the range of external support stiffness values ​​for the shared support structure should be the lowest usable stiffness that the shared support structure can physically achieve, and its selection method is the same as the method for determining the stiffness of the gas generator front support point in step 2. To ensure rotor stability, the external support stiffness of the shared support structure is greater than or equal to 5 × 10 N / m. 6 N / m.

[0104] Step 5: Calculate the unbalanced response of the dual-rotor system with shared support structure under different stiffness combinations:

[0105] The different stiffness combinations mentioned are combinations of the rear support stiffness of the gas generator and the external support stiffness of the common support structure.

[0106] When determining the stiffness value of the rear support point of the gas generator, the lower limit of 5 × 10⁻⁶ determined in step 3 is used. 5 Starting with N / m, and using 1×10 6 The N / m increments are gradually increased until all stiffness values ​​between the lower and upper limits of the rear support stiffness of the gas generator are obtained, with the interval between all the obtained stiffness values ​​being 1×10. 6 N / m.

[0107] The incremental process involves generating an arithmetic sequence with an initial value as the starting point and a step size as the interval, resulting in progressively increasing values. In this embodiment, the first value is 5 × 10. 5 N / m, the second value is 1.5 × 10 6 N / m, the third value is 2.5 × 106 N / m, the fourth value is 3.5 × 10 6 N / m.

[0108] The process involves combining all stiffness values ​​between the lower and upper limits of the gas generator's rear support stiffness with all stiffness values ​​between the lower and upper limits of the shared support structure's external support stiffness in pairs to obtain all possible stiffness combinations. Specifically, the upper limit of the gas generator's rear support stiffness is combined with each of the stiffness values ​​between the lower and upper limits of the shared support structure's external support stiffness to obtain a first set of pairwise combinations. Then, adjacent values ​​of the upper limit of the gas generator's rear support stiffness are combined with each of the stiffness values ​​between the lower and upper limits of the shared support structure's external support stiffness to obtain a second set of pairwise combinations. This process of obtaining the first and second sets of pairwise combinations is repeated to complete all possible stiffness combinations, i.e., completing the combination of each value of the gas generator's rear support stiffness with each of the stiffness values ​​between the lower and upper limits of the shared support structure's external support stiffness, forming a two-dimensional array composed of the gas generator stiffness and the shared support structure's external support stiffness.

[0109] In this embodiment, the number of all stiffness values ​​between the lower and upper limits of the stiffness of the rear support of the gas generator is 100, and the number of all stiffness values ​​between the lower and upper limits of the stiffness of the external support of the shared support structure is , resulting in a total of 10,000 combinations.

[0110] Substitute all the stiffness combinations to be solved, the front support stiffness of the gas generator obtained in step 2, and the unadjusted parameters of all the shared support structure dual rotor systems obtained in step 1 into the one-dimensional finite element method to obtain the unbalanced response of the node to be optimized in the mode to be optimized of the shared support structure dual rotor system; this unbalanced response is the unbalanced response of the shared support structure dual rotor system under different stiffness combinations.

[0111] Step 6: Establish a reference diagram for the stiffness combination optimization of the shared support structure.

[0112] The reference diagram for optimizing the stiffness combination of the shared support structure includes three dimensions, with the dependent variable distributed as a surface, such as... Figure 3 As shown. The specific establishment process is as follows:

[0113] I. Establish a spatial rectangular coordinate system

[0114] The spatial rectangular coordinate system includes three dimensions: x-axis, y-axis, and z-axis. Specifically: the data on the x-axis represents the stiffness of the rear support point of the gas generator, K4, in N / m; the data on the y-axis represents the stiffness K of the external support of the shared support structure. gThe unit is N / m; the coordinate of the z-axis represents the unbalanced response of the unbalanced mode and the unbalanced node of the dual rotor system with shared support structure.

[0115] The x-axis coordinate range is the lower to upper limit of the range of the stiffness of the rear support point of the gas generator rotor; the y-axis coordinate range is the lower to upper limit of the range of the stiffness of the external support of the common support structure; the z-axis coordinate range is to be determined and will be determined through drawing step II.

[0116] II. Plot the rotor unbalance response surface:

[0117] The unbalance response of the dual rotor system with shared support structure under the mode to be optimized and the node to be optimized under the excitation of 5 g·cm unbalance is calculated using the one-dimensional finite element method for each stiffness combination to be solved in step 5. Based on the x and y axis coordinates corresponding to the unbalance response, the unbalance response is plotted in the coordinate system of drawing step I.

[0118] To enhance the readability of the unbalanced response surface, a grid of curves is constructed. Specifically, a curve parallel to the x-axis is used to connect identical unbalanced response points in the x-axis coordinate system; a curve parallel to the y-axis is used to connect identical unbalanced response points in the y-axis coordinate system. The z-axis ranges from the minimum to the maximum unbalanced response value.

[0119] III. Draw the optimal stiffness line

[0120] Select the point with the lowest z-axis value for each grid curve parallel to the x-axis; connect the selected data points to obtain the optimal value line 16 for the stiffness of the rear support of the gas generator. This optimal value line 16 for the stiffness of the rear support of the gas generator is also the optimal value line for stiffness K4. Figure 3 As shown.

[0121] Select the point with the lowest z-axis value for each grid curve parallel to the y-axis; connect these data points to obtain the optimal stiffness line 17 for the shared support structure. This optimal stiffness line for the shared support structure is the stiffness K. g The optimal value line. For example... Figure 3 As shown.

[0122] Using the curve concave point definition method, points located on each grid line parallel to the y-axis and whose z-coordinates are lower than the z-coordinates of the two points on both sides are selected as concave points of the curve; connecting the concave points of the curve, the suboptimal value line 18 of the stiffness of the common support structure is obtained.

[0123] Step 7, Determine the stiffness:

[0124] The stiffness is divided into optimal stiffness and suboptimal stiffness.

[0125] The optimal stiffness is determined by the intersection of the optimal stiffness value line 16 of the gas generator rear support and the optimal stiffness value line 17 of the common support structure, or the suboptimal stiffness is determined by the intersection of the optimal stiffness value line 16 of the gas generator rear support and the suboptimal stiffness value line 18 of the common support structure.

[0126] When the rear support point of the gas generator and the shared support structure, the squirrel-cage drum, are structurally unconstrained and can be designed freely:

[0127] The intersection point of curve 16, representing the optimal value of the rear support stiffness of the gas generator, and curve 17, representing the optimal value of the stiffness of the squirrel-cage drum of the shared support structure, is selected. This intersection point is taken as the optimal combination of the rear support stiffness of the gas generator and the external support stiffness of the shared support structure in the dual-rotor system. The rear support stiffness of the gas generator, the external support stiffness of the shared support structure, and the front support stiffness of the gas generator rotor represent the optimal stiffness of each support point after optimization in the dual-rotor system with the shared support structure. When the rear support stiffness of the rotor gas generator, the external support stiffness of the shared support structure, and the front support stiffness of the gas generator rotor all adopt the optimal stiffness of this support point, the gas generator rotor achieves the maximum dynamic vibration absorption efficiency.

[0128] When interference occurs between the engine fuel supply line and accessory transmission structure and the shared support structure (squirrel cage drum structure), resulting in the intersection of the optimal stiffness value line 16 of the gas generator rear support and the optimal stiffness value line curve 17 of the shared support structure (squirrel cage drum) being impractical in engineering:

[0129] The intersection of the optimal stiffness line 16 of the rear support stiffness of the gas generator and the suboptimal stiffness line 18 of the squirrel cage drum stiffness of the common support structure is taken as the suboptimal stiffness combination of the dual rotor system of the common support structure; when the rotor adopts the above stiffness, the gas generator rotor achieves the suboptimal dynamic vibration absorption efficiency.

[0130] This completes the optimized design of the shared support structure based on dynamic vibration absorption.

Claims

1. An optimized design method for a shared support structure based on dynamic vibration absorption, characterized in that, The specific process is as follows: Step 1: Determine the modes and nodes to be optimized in the dual-rotor system with shared support structure: Determine the non-adjustable parameters of the dual-rotor system with a shared support structure; The non-adjustable parameters of the shared support structure dual-rotor system include the geometric dimensions and material parameters of the power turbine rotor, the stiffness of the front support point of the power turbine rotor, the dimensions and material parameters of the gas generator rotor, and the dimensions and material parameters of the transition section of the shared support structure; each parameter is obtained based on the engine aerodynamic design and spatial dimension technical specifications. The unadjusted parameters of the dual rotor system with shared support structure, the support stiffness of the front support of the gas generator, the support stiffness of the rear support of the gas generator, the support stiffness of the external support of the shared support structure, and the initial unbalance of the disk structure are substituted into the one-dimensional finite element method to calculate the strain energy ratio of each structural component corresponding to each mode of the dual rotor system with shared support structure in the operating speed range, as well as the unbalance response amplitude of the key structural components of the power turbine rotor in the operating speed range. Step 2, determine the stiffness of the front support point of the gas generator: The stiffness of the front support of the gas generator is the lowest usable stiffness that the spring support of the front support of the gas generator can physically achieve. The stiffness of the cage spring support, which serves as the front fulcrum, is affected by factors including the material of the cage spring support, the length of the cage bars, the number of cage bars, the width of the cage bars, the cross-section of the cage bars, and the rounding dimensions at the root of the cage bars. Step 3: Determine the range of values ​​for the stiffness of the rear support point of the gas generator: The upper limit of the stiffness range of the rear support point of the gas generator is the stiffness of the bearing model at the rear support point of the gas generator. Step 4: Determine the range of values ​​for the external support stiffness of the shared support structure: The upper limit of the stiffness value of the external support stiffness of the shared support structure is the decoupling stiffness of the dual-rotor system of the shared support structure; this decoupling stiffness should be 10 times the upper limit of the stiffness value of the rear support of the gas generator; the lower limit of the range of values ​​for the external support stiffness of the shared support structure should be the lowest usable stiffness that the shared support structure can physically achieve, and its selection method is the same as the method for determining the stiffness of the front support of the gas generator in step 2; the external support stiffness of the shared support structure is greater than or equal to 5 × 10 6 N / m; Step 5: Calculate the unbalanced response of the dual-rotor system with shared support structure under different stiffness combinations: The different stiffness combinations mentioned are combinations of the stiffness of the rear support point of the gas generator and the stiffness of the external support of the common support structure; when determining the value of the stiffness of the rear support point of the gas generator, it is based on the lower limit of 5 × 10⁻⁶ determined in step 3. 5 Starting with N / m, and using 1×10 6 The N / m increments are gradually increased until all stiffness values ​​between the lower and upper limits of the rear support stiffness of the gas generator are obtained, with the interval between all the obtained stiffness values ​​being 1×10. 6 N / m; All stiffness values ​​between the lower and upper limits of the stiffness of the rear support of the gas generator are combined with all stiffness values ​​between the lower and upper limits of the stiffness of the external support of the common support structure to obtain all stiffness combinations to be solved. Substitute all the stiffness combinations to be solved, the stiffness of the front support of the gas generator obtained in step 2, and the unadjusted parameters of all the shared support structure dual rotor systems obtained in step 1 into the one-dimensional finite element method to obtain the unbalanced response of the node to be optimized in the mode to be optimized of the shared support structure dual rotor system; this unbalanced response is the unbalanced response of the shared support structure dual rotor system under different stiffness combinations. Step 6: Establish a reference diagram for the stiffness combination optimization of the shared support structure. The reference diagram for optimizing the stiffness combination of the shared support structure includes three dimensions, with the independent variables distributed as a surface; its specific establishment process is as follows: I. Establish a spatial rectangular coordinate system The spatial rectangular coordinate system includes three dimensions: x-axis, y-axis, and z-axis; wherein: the x-axis represents the stiffness K4 of the rear support point of the gas generator, in N / m; the y-axis represents the stiffness K of the external support of the shared support structure. g The unit is N / m; the z-axis represents the unbalanced response of the unbalanced mode and node to be optimized in the dual rotor system with shared support structure. II. Plot the rotor unbalance response surface: The unbalance response of the dual rotor system with shared support structure under the mode to be optimized and the node to be optimized under the 5 g·cm unbalance excitation is calculated by the one-dimensional finite element method for each stiffness combination to be solved in step 5. The unbalance response is plotted in the coordinate system according to the x and y axis coordinates corresponding to the unbalance response. Constructing grid curves enhances the readability of unbalanced response surfaces; III. Draw the optimal stiffness line Select the point with the lowest z-axis value for each grid curve parallel to the x-axis; connect the selected data points to obtain the optimal value line for the stiffness of the rear support of the gas generator; the optimal value line for the stiffness of the rear support of the gas generator is the optimal value line for stiffness K4. Select the point with the lowest z-axis value for each grid curve parallel to the y-axis; connect the selected data points to obtain the optimal value line for the stiffness of the common support structure; this optimal value line for the stiffness of the common support structure is the stiffness K. g The optimal value line; Using the curve concave point definition method, points located on each grid line parallel to the y-axis and whose z-coordinates are lower than the z-coordinates of the two points on either side are selected as concave points of the curve; connecting the concave points of the curve yields the suboptimal value line of the stiffness of the common support structure. Step 7, Determine the stiffness: The stiffness is divided into optimal stiffness and suboptimal stiffness; The optimal stiffness is determined by the intersection of the optimal stiffness value line of the rear support of the gas generator and the optimal stiffness value line of the common support structure, or the suboptimal stiffness is determined by the intersection of the optimal stiffness value line of the rear support of the gas generator and the suboptimal stiffness value line of the common support structure. When the rear support point of the gas generator and the shared support structure, the squirrel-cage drum, are structurally unconstrained and can be designed freely: The intersection point of the optimal value curve of the rear support stiffness of the gas generator and the optimal value curve of the stiffness of the squirrel cage drum of the common support structure is selected. This intersection point is taken as the optimal combination of the rear support stiffness of the gas generator and the external support stiffness of the common support structure in the dual rotor system of the common support structure. The rear support stiffness of the gas generator, the external support stiffness of the common support structure, and the front support stiffness of the gas generator rotor are the optimal stiffness of each support point after optimization in the dual rotor system of the common support structure. When the rear support stiffness of the rotor gas generator, the external support stiffness of the common support structure, and the front support stiffness of the gas generator rotor all adopt the optimal stiffness of this support point, the gas generator rotor achieves the maximum dynamic vibration absorption efficiency. When interference occurs between the engine fuel supply line and accessory transmission structure and the shared support structure (squirrel cage drum structure), resulting in the infeasibility of the support stiffness combination at the intersection of curve 17 (the optimal value line for the rear support stiffness of the gas generator and the optimal value line for the stiffness of the shared support structure (squirrel cage drum)): When the intersection of the optimal stiffness curve of the rear support of the gas generator and the optimal stiffness curve of the squirrel cage drum of the common support structure is not feasible in engineering, the intersection of the optimal stiffness curve of the rear support of the gas generator and the suboptimal stiffness curve of the squirrel cage drum of the common support structure shall be taken as the suboptimal stiffness combination of the dual rotor system of the common support structure; when the rotor adopts the above stiffness, the gas generator rotor achieves suboptimal dynamic vibration absorption efficiency. This completes the optimized design of the shared support structure based on dynamic vibration absorption.

2. The optimization design method for a shared support structure based on dynamic vibration absorption as described in claim 1, characterized in that, The stiffness of the front support point of the gas generator, the stiffness of the rear support point of the gas generator, and the stiffness of the external support of the common support structure are each assigned a rigid support stiffness, the value of which is 1×10. 8 N / m; the initial imbalance of the disc structure closest to the common support structure of the gas generator rotor; the initial imbalance is 5 g·cm.

3. The optimization design method for a shared support structure based on dynamic vibration absorption as described in claim 1, characterized in that, Among the strain energy proportions of each structural component corresponding to each of the various modes, the first mode with the highest proportion of strain energy of the power turbine rotor shaft to the total strain energy is the mode to be optimized in the dual-rotor system with shared support structure; at the mode to be optimized, the structural component with the largest unbalanced response amplitude is the node to be optimized in the power turbine rotor of the dual-rotor system with shared support structure.

4. The optimization design method for a shared support structure based on dynamic vibration absorption as described in claim 1, characterized in that, When determining the stiffness of the rat cage spring support structure: I. Select the material for the rat cage spring support; II. According to the design requirements, determine the length of the spring support at the front support of the gas generator based on the axial space dimension at the front support of the gas generator; select the minimum number of cage bars according to the strength of the materials and the requirements of the aero-engine design manual. The number of spring bars selected for this rat cage is ≥8; the width of the cage bars is determined to be ≥5mm according to the design requirements; Ⅲ. Determine the minimum rounding dimension at the root of the cage bars based on the allowable stress of the material; the selected minimum rounding radius at the root of the cage bars is ≥5mm; IV. Determine the material of the cage spring support and the cross-section of the cage bars according to the design requirements; the cross-section of the cage bars includes the cross-sectional area, cross-sectional moment and cross-sectional shape of the cage bars; V. Based on the determined material of the cage spring support, the length of the cage bars, the number of cage bars, the width of the cage bars, the cross-section of the cage bars, and the radius of the rounded corner at the root of the cage bars, the minimum usable stiffness of the front support of the gas generator is obtained through simulation calculation using commercial software such as ANSYS, NX, Abaqus, or NASTRAN. This minimum usable stiffness of the front support of the gas generator is the stiffness of the front support of the gas generator selected in this invention.

5. The optimization design method for a shared support structure based on dynamic vibration absorption as described in claim 1, characterized in that, The upper limit of the stiffness range of the rear support point of the gas generator is 2×10. 7 N / m; The lower limit of the stiffness range for the rear support of the gas generator is the lowest usable stiffness that the spring support of the rear support of the gas generator can physically achieve. Its selection method is the same as that for the front support stiffness of the gas generator in step 2. To ensure rotor stability, the lower limit of the stiffness of the rear support of the gas generator should be greater than or equal to 5 × 10 N / m. 5 N / m.

6. The optimization design method for a shared support structure based on dynamic vibration absorption as described in claim 1, characterized in that, When incrementing sequentially, an arithmetic sequence is generated by starting with an initial value and using a step size as the interval.

7. The optimization design method for a shared support structure based on dynamic vibration absorption as described in claim 1, characterized in that, The specific process is as follows: the upper limit of the stiffness of the rear support of the gas generator is combined with all stiffness values ​​between the lower and upper limits of the stiffness of the external support of the shared support structure to obtain a first set of pairwise combination points; then, adjacent values ​​of the upper limit of the stiffness of the rear support of the gas generator are combined with all stiffness values ​​between the lower and upper limits of the stiffness of the external support of the shared support structure to obtain a second set of pairwise combination points; the process of obtaining the first and second sets of pairwise combination points is repeated to complete all stiffness combinations to be solved, that is, to complete the combination of each value of the stiffness of the rear support of the gas generator with all stiffness values ​​between the lower and upper limits of the stiffness of the external support of the shared support structure, forming a two-dimensional array composed of the stiffness of the gas generator and the external support of the shared support structure.

8. The optimization design method for a shared support structure based on dynamic vibration absorption as described in claim 1, characterized in that, The range of values ​​for the x-axis coordinate is from the lower limit to the upper limit of the range of values ​​for the rear support stiffness of the gas generator rotor; The range of values ​​for the y-axis coordinate is from the lower limit to the upper limit of the range of values ​​for the external support stiffness of the shared support structure; The range of z-axis coordinates is determined by drawing step II.

9. The optimization design method for a shared support structure based on dynamic vibration absorption as described in claim 1, characterized in that, The specific method for constructing the grid curve is as follows: use a curve parallel to the x-axis to connect the same unbalanced response points in the x-axis coordinate; use a curve parallel to the y-axis to connect the same unbalanced response points in the y-axis coordinate; the z-axis ranges from the minimum unbalanced response value to the maximum unbalanced response value.

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