A robust design method for the connection stiffness of an engine pull-rod rotor rigid sleeve gear coupling and its application

Abstract

The present invention discloses a method for designing the robustness of the connection stiffness of a rigid sleeve gear coupling of an engine tie rod rotor and its application, which is used for the dynamic optimization design of a three-point supported slender center tie rod rotor structure in an aircraft engine or a gas turbine. The present invention optimizes the position and structure of the coupling by establishing a finite element model for rotor dynamics analysis, calculating and analyzing the critical speed and strain energy density distribution of the rotor, and combining static and dynamic strength requirements. The method includes the steps of optimizing the fulcrum stiffness and rotor structural parameters, analyzing the positioning reliability of the coupling locating stop, moving the coupling to a low strain energy density and low stress area, and iterative verification and optimization. The present invention improves the robustness of the coupling connection stiffness, optimizes the rotor dynamics performance, and reduces the risk of rotor vibration by optimizing the coupling position and structure. It can be directly applied to the engineering design of aircraft engines and gas turbines and has important engineering application value.

Description

Technical Field

[0001] The present invention belongs to the field of aero-engine and gas turbine rotor dynamics and relates to the rigid connection design of rotor structures. Specifically, the present invention provides a method for robustly designing the connection stiffness of a rigid sleeve gear coupling of an engine pull-rod rotor and its application, which are used to optimize the design of the rigid sleeve gear coupling. Background Art

[0002] Aeroengine rotordynamics design is one of the core technologies in aeroengine design. Its primary goal is to reduce overall engine vibration to an acceptable level, ensuring high-reliability flight for the aircraft. To achieve this, rotordynamics design must adhere to strict design criteria. To meet these criteria, rotor stiffness and support stiffness must be designed. Given a certain support stiffness, rotor stiffness becomes the primary factor influencing rotordynamic characteristics.

[0003] In aircraft engine rotor systems, when the shaft system is long and the overall structure is slender, a segmented shaft design is often adopted to meet the actual requirements of processing and assembly. For example, the shaft can be made into a two-section structure. The two shaft sections need to be connected by a rigid sleeve gear coupling. The rigid sleeve gear coupling needs to transmit torque under high speed and high load conditions, and it needs to achieve a rigid connection between the two shaft sections through a precise sleeve gear structure to achieve the goal of achieving the same stiffness of the rigid sleeve gear connection shaft as that of a single unconnected shaft, thereby minimizing vibration problems caused by insufficient connection stiffness. However, in the existing technology, the design of rigid sleeve gear couplings still faces many challenges.

[0004] First of all, in terms of dynamic design, the design quality of the rigid sleeve gear coupling directly affects the size of the connection stiffness and directly affects the dynamic characteristics of the rotor. Since the rotor is subjected to the coupling of multiple vibration modes during operation, if the coupling is not well designed and the connection stiffness is insufficient, the rotor vibration will be aggravated. High vibration will not only accelerate the fatigue damage of the coupling, but may also cause the vibration of the entire machine to exceed the standard.

[0005] Secondly, in terms of static strength design, the fit of the locating spigots in a rigid sleeve gear coupling is a crucial factor in determining its stability. The locating spigots precisely connect the shaft segments at both ends of the coupling through axial and radial fit. However, due to the centrifugal forces and other complex loads that the rotor is subjected to during operation, the fit of the locating spigots may be affected, resulting in partial or complete disengagement. This instability in the fit further weakens the coupling's connection performance.

[0006] In addition, in response to the special requirements of slender shaft structures, existing design methods lack clear quantitative design guidance, especially in three-point support structures. Due to the uneven distribution of support stiffness and the high stiffness of the main load-bearing support, the coupling connection stiffness is affected by both dynamic strength, i.e. vibration, and static strength, i.e. the positioning state of the stop. The coupling design needs to balance the load distribution between the supports while meeting the dual requirements of dynamic strength and static strength.

[0007] While the concept of robust connection structure stiffness has been proposed in rotor dynamics design, robust connection design is merely a design requirement, lacking specific practical methods or providing only qualitative guidance. A systematic optimization design methodology has yet to be established. Achieving robust design requirements for rigid sleeve gear couplings based on specific rotor structural characteristics is a challenge due to the lack of reliable references. Designers rely on experience and trial and error to achieve design goals, which is not only time-consuming and labor-intensive, but also makes it difficult to ensure design reliability and optimality.

[0008] In summary, the existing technology still has many defects and deficiencies in the design of the connection stiffness of rigid sleeve gear couplings. Therefore, how to achieve the robustness of the coupling connection stiffness and balance the dynamic and static performance is a technical problem that needs to be solved urgently in the field of engine rotor dynamics design. Summary of the Invention

[0009] (1) Purpose of the invention

[0010] In view of the above-mentioned defects and shortcomings in the prior art, in order to improve the connection stiffness and stability of the rotor structure of the three-point supported slender center rod rigid sleeve gear coupling of an aircraft engine or gas turbine, the present invention provides a robustness design method for an engine pull rod type rigid sleeve gear coupling and its application. When the pull rod preload is determined, the rotor strain energy density at the sleeve gear coupling within the full speed range, the matching state of the coupling locating stop at the operating speed and the position of the main load-bearing fulcrum of the three-point supported rotor are analyzed, and the coupling is placed at a position with low rotor strain energy density to ensure that at least 1 / 2 of the length of the locating stop is in a reliable positioning state, and the coupling should be as close to the main load-bearing fulcrum as possible to achieve a robustness design of the coupling that takes into account both dynamic strength and static strength requirements, thereby effectively reducing the risk of rotor vibration, improving the overall stability and reliability of the rotor system, and ensuring reliable operation of the engine.

[0011] (2) Technical solution

[0012] In order to achieve the purpose of the invention and solve the technical problems, the present invention adopts the following technical solutions:

[0013] The first object of the present invention is to provide a method for designing the robustness of the connection stiffness of a rigid sleeve gear coupling of an engine tie rod rotor, which is used for the dynamic optimization design of a three-point supported slender center tie rod rotor structure in an aircraft engine or gas turbine, thereby improving the robustness of the connection stiffness of the rigid sleeve gear coupling, optimizing the rotor dynamics performance, and reducing the risk of rotor vibration. The design method is implemented in the following steps:

[0014] SS1. Initial Structural Rotor Dynamics Analysis Finite Element Model Establishment

[0015] Based on a two-dimensional diagram of a slender center-tie rod rotor supported at three points in an engine, the rigid sleeve gear coupling was simplified into a rigid connection. A finite element model (FEM) for rotor dynamics analysis of the initial structure was established. The initial support stiffness of each point was assumed, and the critical speed and strain energy of the rotor within a preset speed range were calculated based on the FEM model.

[0016] SS2. Optimize rotor structural parameters and determine support stiffness at each support point

[0017] For the critical speed and strain energy of the rotor under the initial support stiffness calculated in step SS1, analyze and determine whether they meet the preset rotor dynamics design criteria: if they do, proceed to step SS3; if not, within the allowable range of the overall structural boundary conditions, combine the FEM model to iteratively optimize the rotor structural parameters and the support stiffness of each support until the rotor critical speed, strain energy distribution and mode shape characteristics meet the design criteria, and finally determine the rotor structural parameters and the support stiffness of each support;

[0018] SS3. Analysis of strain energy density distribution at the coupling at critical speed

[0019] Based on the rotor structure and support stiffness of each pivot point determined after iterative optimization in step SS2, the strain energy density distribution of the rotor at the critical speed under the determined support stiffness is calculated and analyzed using the FEM model, and the strain energy density level of the rotor at the rigid sleeve gear coupling is determined: if it is at a low strain energy density level, proceed to step SS4; if it is at a high strain energy density level, proceed to step SS5;

[0020] SS4. Reliability Analysis of Coupling Locating Seat Positioning

[0021] Analyze the positioning state of the rigid sleeve gear coupling's positioning spigot at the operating speed, analyze the radial deformation and positioning reliability of the positioning spigot, and determine whether the positioning length of the positioning spigot meets the requirement of at least 1 / 2 of the total spigot length and is in a reliable positioning state. If the spigot positioning length is less than 1 / 2 of the total spigot length, proceed to step SS5 to optimize the coupling position and structure. If it is not less than 1 / 2 of the total spigot length, the spigot positioning length meets the requirements and the design is complete.

[0022] SS5. Optimized design of coupling position and structure

[0023] First, the FEM model is used to calculate and analyze the equivalent stress distribution of the rotor structure at the operating speed, and the rotor equivalent stress that meets the static strength requirements is divided into several different levels. Then, based on the calculated equivalent stress distribution of the rotor and combined with the strain energy density distribution calculated in step SS3, the rigid sleeve gear coupling is moved to a low strain energy density and low stress uniform deformation position, and an improved coupling structure design is performed, adjusting its geometric parameters and stop structure.

[0024] SS6. Verification and Optimization of Strain Energy Density of Improved Coupling Structure

[0025] Based on the coupling position and structure optimized in step SS5, the strain energy density of the improved coupling structure at the critical speed is recalculated and analyzed based on the FEM model. If the strain energy density of the coupling does not meet the low strain energy density level requirement, return to step SS3 and iterate until the requirement is met.

[0026] SS7. Verification and Optimization of the Positioning Seam Status of the Improved Coupling Structure

[0027] Based on the coupling position and structure optimized in step SS6, the positioning state of the positioning stop at the working speed of the improved coupling structure is recalculated and analyzed based on the FEM model. If the positioning length of the stop is less than 1 / 2 of the total length of the stop, return to step SS3 for loop iteration until the positioning length of the stop meets the requirements, complete the design, and finally determine the optimization plan.

[0028] A second object of the present invention is to provide an engine tie-rod rigid sleeve gear coupling based on the aforementioned method for robust design of the connection stiffness of an engine tie-rod rotor rigid sleeve gear coupling. This coupling is located in a uniform deformation zone with low strain energy density and low stress, optimized and determined by this design method. It exhibits high robustness of connection stiffness, excellent rotor dynamics performance, and low vibration risk, effectively improving the stability and reliability of a three-point supported slender center-tie-rod rotor system.

[0029] The third object of the present invention is to provide an aircraft engine or gas turbine, comprising the above-mentioned engine tie rod type rigid sleeve gear coupling of the present invention, which can effectively improve the overall performance, stability and reliability of the aircraft engine or gas turbine.

[0030] (3) Technical effects

[0031] Compared with the prior art, the engine tie rod rotor rigid sleeve gear coupling connection stiffness robustness design method and its application of the present invention have the following beneficial and significant technical effects:

[0032] (1) This invention establishes a finite element model (FEM) for rotor dynamics analysis and combines quantitative analysis of critical speed, strain energy density, and positioning reliability of the locating spigot. It proposes a robust design of the rigid sleeve gear coupling from three aspects: rotor dynamic strength (i.e., rotor strain energy density during vibration), static strength (i.e., the state of the locating spigot fit under centrifugal force), and the characteristics of the three-point rotor support structure. It also provides clear quantitative design requirements, significantly improving the scientific nature and standardization of the design. This method clarifies the key design criteria and optimization goals by gradually iteratively optimizing the rotor structural parameters, the fulcrum support stiffness, and the geometric position and structure of the coupling, providing clear guidance for engineering design.

[0033] (2) The design method proposed in this invention designs the robustness of the coupling from two aspects: the strain energy density at the coupling and the reliability of the positioning of the locating stop. Combined with the analysis results of the strain energy density distribution, the coupling is arranged in a low strain energy density area to avoid the weakening of the coupling connection stiffness due to high strain energy density. In addition, by optimizing the geometric parameters and stop structure of the coupling, the reliable fit of the locating stop at the operating speed is ensured, reducing the problem of connection stiffness reduction due to positioning failure. The rigid sleeve gear coupling designed according to this method has high robustness, low stiffness loss, and can reduce the risk factors of large rotor vibration.

[0034] (3) By optimizing the stiffness configuration of the rotor support system and the layout of the coupling, the present invention achieves a reasonable margin between the rotor's critical speed and operating speed, thus avoiding resonance. Particularly under high-speed operating conditions, the present invention ensures a stable connection of the coupling by optimizing the radial deformation consistency of the positioning stop, thereby improving the dynamic performance of the rotor system and the overall operational reliability.

[0035] (4) The design method of the present invention has clear steps, rigorous logic, and strong feasibility, and can directly guide the engineering design of similar structures of aircraft engines and gas turbines. In particular, for similar three-point supported slender rotor structures, the present invention provides a universal optimization design approach that can be applied to a wide range of rotor dynamics optimization design scenarios and has important engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A flowchart of the implementation of the method for robust design of the connection stiffness of a rigid sleeve gear coupling of an engine pull-rod rotor provided by an embodiment of the present invention;

[0037] Figure 2 This is a schematic diagram of the engine pull rod rotor structure;

[0038] Figure 3 This is a schematic diagram of the original structure of the rigid sleeve gear coupling;

[0039] Figure 4 Schematic diagram of rotor strain energy density at the first critical speed;

[0040] Figure 5 Schematic diagram of rotor strain energy density at the second critical speed;

[0041] Figure 6 This is a schematic diagram of the positioning state of the original structure;

[0042] Figure 7 This is a schematic diagram of the improved structure of the coupling;

[0043] Figure 8 This is a schematic diagram of the positioning status of the improved coupling structure. DETAILED DESCRIPTION

[0044] In order to better understand the present invention, the following detailed description of the engine pull-rod rotor rigid sleeve gear coupling connection stiffness robustness design method and its application is given in conjunction with specific embodiments to help better understand the technical features of the present invention and its actual operation process. The method of the present invention is based on finite element analysis and dynamic optimization design. By gradually analyzing and optimizing the structural parameters, positioning stop state and strain energy density distribution of the coupling, the coordinated optimization of dynamic and static performance is ultimately achieved. The following content is intended to provide a repeatable, scientific and rigorous implementation method that is convenient for direct application in engineering design.

[0045] in accordance with Figure 1 The present invention realizes the robustness design of the connection stiffness of the engine pull rod type rigid sleeve gear coupling according to the process shown in the figure. Specifically, the design method of the present invention mainly includes the following steps when implemented:

[0046] SS1. Initial Structural Rotor Dynamics Analysis Finite Element Model Establishment

[0047] According to the two-dimensional structure diagram of the slender center rod rotor supported by three pivot points in the engine, the rigid sleeve gear coupling is simplified into a rigid connection, and the rotor dynamics analysis finite element model (FEM) of the initial structure is established. Figure 2 , the original structure diagram of the coupling is shown in Figure 3When establishing the FEM model, the structure of the three-point support slender center rod rotor is simplified to a three-point support. The three rotor supports are marked as support 1, support 2, and support 3 from the intake side to the exhaust side. Support 2 is the main load-bearing support and is designed as a rigid support with a support stiffness of 10 8 N / m level; support point 1 and support point 3 are the two end supports, designed as elastic supports, and the support stiffness is 10 7 The rotor supports are simulated in N / m to simulate actual operating conditions. By assuming an initial support stiffness at each support point, the critical speed and rotor strain energy are calculated within a preset speed range based on the FEM model. This preset speed range encompasses the entire rotor system speed range from startup to maximum operating speed, as well as all possible resonant speed ranges, to ensure completeness and accuracy of the analysis. The initial support stiffness at each support point is initially set based on experience or design parameters of similar rotor systems to facilitate subsequent iterative optimization.

[0048] Preferably, the establishment of the FEM model includes simplifying the geometric features of the rotor shaft and setting parametric constraints on the rigid sleeve gear coupling, wherein: the geometric features of the rotor shaft include at least the shaft diameter, shaft length and key section positions, and the parametric constraints of the rigid sleeve gear coupling include at least the rigid connection assumption conditions, the alignment accuracy of the sleeve gear mating surface and the symmetry of the coupling geometric center with respect to the rotor shaft center, to ensure that the FEM model can accurately characterize the rotor dynamic behavior.

[0049] SS2. Optimize rotor structural parameters and determine support stiffness at each support point

[0050] The critical speed and strain energy of the rotor at the initial support stiffness calculated in step SS1 are analyzed to determine whether they meet the preset rotor dynamics design criteria. If so, the process proceeds to step SS3. If not, the rotor structural parameters and the elastic support stiffness of each support point are optimized using the FEM model within the overall structural boundary conditions. This process is repeated until the rotor critical speed, strain energy distribution, and mode shape characteristics meet the design criteria. The final rotor structure and support stiffness of each support point are determined. The final stiffness of the elastic supports at both ends is determined to be 1e7 N / m, and the stiffness of the main load-bearing support point is 1e8 N / m.

[0051] Preferably, the preset rotor dynamics design criteria include at least: there is only a rigid body modal critical speed within the working range, the rigid body modal critical speed has a margin of more than 20% from the main working speed zone, and the rigid body modal rotor strain energy is less than 25%; the bending critical speed is greater than the maximum working speed, and the margin from the maximum working speed is more than 20%. In addition, the optimization of the rotor structural parameters includes at least adjusting the rotor shaft diameter, shoulder transition radius, shaft length and the structural shape of the coupling connection; the optimization of the support stiffness includes adjusting the stiffness coefficient of each support point, and at the same time performing a linear iteration of 20% on the elastic support stiffness of the support point based on the initial assumed value; on the premise of meeting the rotor dynamics design criteria, a design scheme with simple structure and high processing accuracy is selected to improve the engineering feasibility and reliability of the rotor system.

[0052] SS3. Analysis of strain energy density distribution at the coupling at critical speed

[0053] Based on the rotor structure and the support stiffness of each support point determined after the iterative optimization in step SS2, the support stiffness and the rotor strain energy density at the critical speed under the structure are calculated using the FEM model. Figure 4 、 Figure 5 And judge the strain energy density level of the rotor at the rigid sleeve gear coupling: if it is at a low strain energy density level, go to step SS4; if it is at a high strain energy density level, go to step SS5. Figure 4 and Figure 5 It can be seen that at the first critical speed, the rotor strain energy density at the coupling is between levels 8 and 10, and at the second critical speed, it is also between levels 8 and 10, indicating high strain energy density. Meanwhile, at the main support point 2, the strain energy density is at level 1, indicating low strain energy density, at both the first and second critical speeds. According to the present invention, the rigid sleeve gear coupling can be moved to the main support point 2.

[0054] Preferably, the strain energy density classification method in the present invention is to divide the rotor strain energy density into 10 levels from zero to maximum, with the lowest strain energy density being level 1 and the highest strain energy density being level 10. Levels 8 to 10 are defined as high strain energy density regions, and levels 1 to 3 as low strain energy density regions. The strain energy density is calculated based on the determined rotor structural parameters and support stiffness and is performed at the critical speed.

[0055] SS4. Reliability Analysis of Coupling Locating Seat Positioning

[0056] Calculate the positioning state of the locating mouth of the rigid sleeve gear coupling at the working speed, see Figure 6, analyze the radial deformation and positioning reliability of the positioning stop, and determine whether the positioning length of the positioning stop meets the requirement of at least 1 / 2 of the total length of the stop and is in a reliable positioning state. If the positioning length of the stop is less than 1 / 2 of the total length of the stop, go to step SS5 to optimize the position and structure of the coupling. If it is not less than 1 / 2 of the total length of the stop, the positioning length of the stop meets the requirements and the design is completed.

[0057] from Figure 6 It can be seen that at the operating speed, only the corners of the stopper are in position, while the rest of the stopper is separated. This means that the stopper length does not meet the requirement of greater than 1 / 2 the stopper length proposed in this invention. Analysis indicates that the main cause is inconsistent radial deformation of the stopper, with one end larger and the other smaller. This requires moving the stopper to a position with greater rigidity. When the rigid sleeve gear coupling is moved to fulcrum 2, the requirement for consistent radial deformation of the stopper is achieved.

[0058] SS5. Optimized design of coupling position and structure

[0059] First, the equivalent stress distribution of the rotor structure at the operating speed is calculated and analyzed based on the FEM model, and the rotor equivalent stress that meets the static strength requirements is divided into several different levels; then, based on the calculation results of the rotor equivalent stress distribution and combined with the strain energy density distribution calculated in step SS3, the rigid sleeve gear coupling is moved to a low strain energy density and low stress uniform deformation position, and the coupling structure is improved and its geometric parameters and stop structure are adjusted.

[0060] As a preference, if the rigid sleeve gear coupling is located near the main load-bearing rigid fulcrum, the coupling position is moved as close to the main load-bearing fulcrum as possible to fully utilize the high rigidity characteristics of the main load-bearing rigid fulcrum to further strengthen the rigidity of the coupling, while reducing the bending moment and shear force transmitted by the coupling and improving the robustness of the connection rigidity. In this embodiment, the coupling structure is improved by moving the rigid sleeve gear coupling to the main load-bearing fulcrum 2. Figure 7 .

[0061] Preferably, the rotor equivalent stress levels are divided as follows: the rotor equivalent stress that meets the static strength requirements is divided into 10 levels from zero to maximum, the lowest stress is level 1, and the highest stress is level 10, and levels 1 to 2 are defined as low stress areas, which are used to judge whether the stress state of the coupling position is appropriate; low stress uniform deformation is defined as: meeting the structural function and assembly conditions of the sleeve gear coupling, being in the low stress area, and having uniform static deformation over the entire length of the locating stop, and being able to achieve reliable positioning of at least 1 / 2 of the positioning length.

[0062] SS6. Verification and Optimization of Strain Energy Density of Improved Coupling Structure

[0063] Based on the optimized coupling position and structure in step SS5, the critical speed and strain energy density at the coupling of the improved coupling structure are recalculated using the FEM model. If the coupling strain energy density does not meet the low strain energy density level requirement, the process returns to step SS3 and iterates until the requirement is met. In this embodiment, the position of the rotor's maximum strain energy density at the critical speed is the same as before the improvement. However, because the rigid sleeve gear coupling is relocated to the main bearing support point 2, the strain energy density there is low, which prevents the coupling's connection stiffness from being weakened during rotor vibration.

[0064] SS7. Verification and Optimization of the Positioning Seam Status of the Improved Coupling Structure

[0065] Based on the coupling position and structure optimized in step SS6, the positioning state of the improved coupling structure at the working speed is recalculated based on the FEM model. Figure 8 If the stopper positioning length is less than 1 / 2 of the total stopper length, then return to step SS3 and iterate until the stopper positioning length meets the requirement. Figure 8 As we know, the coupling structure is improved and the positioning spigot is well positioned throughout the entire length range. At this point, the robustness design of the rigid sleeve gear coupling is completed.

[0066] In summary, this invention defines a quantitative robustness design method for tie-rod rigid sleeve gear couplings. This method evaluates coupling robustness based on two key aspects: strain energy density at the coupling and positioning reliability of the locating spigot. Rigid sleeve gear couplings designed using this method exhibit high robustness, minimize stiffness loss, and mitigate the risk of significant rotor vibration. This design method is simple to understand and highly applicable, and can directly guide the design of similar structural designs for aircraft engines and gas turbines.

[0067] The above embodiments fully and effectively achieve the objectives of the present invention. Those skilled in the art will appreciate that the present invention includes, but is not limited to, the contents described in the accompanying drawings and the above specific embodiments. Although the present invention has been described with reference to the embodiments currently considered to be the most practical and preferred, it should be understood that the present invention is not limited to the disclosed embodiments, and any modifications that do not deviate from the functional and structural principles of the present invention are intended to be included within the scope of the claims.

Claims

1. A method for robust design of connection stiffness of a rigid sleeve gear coupling of an engine pull-rod rotor, characterized in that: The design method comprises at least the following steps when implemented: SS1. Based on the two-dimensional structure of a slender center-tie rod rotor supported at three points in an engine, the rigid sleeve gear coupling was simplified into a rigid connection. A rotor dynamics analysis FEM model for the initial structure was established. The initial support stiffness of each point was assumed, and the critical speed and strain energy of the rotor within a preset speed range were calculated based on the FEM model. SS2. Analyze and determine whether the critical speed and strain energy of the rotor under the initial support stiffness calculated in step SS1 meet the preset rotor dynamics design criteria: if so, proceed to step SS3; If not, then within the allowable range of the overall structural boundary conditions, the rotor structural parameters and the support stiffness of each support point are iteratively optimized using the FEM model until the rotor critical speed, strain energy distribution, and vibration mode characteristics meet the design criteria, and the rotor structural parameters and the support stiffness of each support point are finally determined; SS3. Based on the rotor structure and support stiffness determined after iterative optimization in step SS2, use the FEM model to calculate and analyze the rotor strain energy density distribution at the critical speed for the determined support stiffness. Determine the rotor strain energy density level at the rigid sleeve gear coupling. If the strain energy density level is low, proceed to step SS4; if the strain energy density level is high, proceed to step SS5. SS4. Analyze the positioning status of the rigid sleeve gear coupling's locating spigot at the operating speed, analyze the spigot's radial deformation and positioning reliability, and determine whether the spigot's positioning length meets the requirement of at least 1 / 2 of the spigot's total length, ensuring reliable positioning. If the spigot's positioning length is less than 1 / 2 of the spigot's total length, proceed to step SS5 for coupling position and structural optimization. If it is not less than 1 / 2 of the spigot's total length, the spigot's positioning length meets the requirements, and the design is complete. SS5. First, the FEM model is used to calculate and analyze the rotor structure's equivalent stress distribution at operating speed. The rotor's equivalent stress, which meets static strength requirements, is classified into several levels. Next, based on the rotor's equivalent stress distribution and the strain energy density distribution calculated in step SS3, the rigid sleeve gear coupling is moved to a position with low strain energy density and uniform deformation. An improved coupling structure is then designed, with adjustments made to its geometric parameters and stop structure. SS6. Based on the coupling position and structure optimized in step SS5, recalculate and analyze the strain energy density of the improved coupling structure at the critical speed using the FEM model. If the coupling strain energy density does not meet the low strain energy density level requirement, return to step SS3 and iterate until the requirement is met. SS7. Based on the coupling position and structure optimized in step SS6, recalculate and analyze the positioning state of the improved coupling structure at the operating speed using the FEM model. If the positioning length of the positioning length is less than 1 / 2 of the total positioning length, return to step SS3 and iterate until the positioning length meets the requirements. This completes the design and ultimately determines the optimization solution.

2. The engine rod rotor rigid sleeve gear coupling connection stiffness robustness design method according to claim 1, characterized in that: In the above step SS1, the establishment of the FEM model includes the simplification of the geometric features of the rotor shaft and the setting of parametric constraints on the rigid sleeve gear coupling, wherein: the geometric features of the rotor shaft include at least the shaft diameter, shaft length and key section position, and the parametric constraints of the rigid sleeve gear coupling include at least the rigid connection assumption conditions, the alignment accuracy of the sleeve gear mating surface and the symmetry of the coupling geometric center with respect to the rotor shaft center.

3. The method for robust design of connection stiffness of a rigid sleeve gear coupling of an engine pull-rod rotor according to claim 2, characterized in that: In the above step SS1, the preset speed range includes the entire speed range from the start-up of the rotor system to the maximum operating speed and all possible resonant speed ranges; The initial support stiffness is preliminarily set based on experience or design parameters of similar rotor systems. When establishing the FEM model, the structure of the three-point support slender center rod rotor is simplified to a three-point support. The three supports are marked as support I, support II and support III from the intake side to the exhaust side, where support I and support III are elastic supports, support II is the main load-bearing rigid support, and the support stiffness of support I and support III is assumed to be 10 7 The support stiffness of support point II is 10 8 N / m level.

4. The method for robust design of connection stiffness of a rigid sleeve gear coupling of an engine pull-rod rotor according to claim 1, characterized in that: In step SS2 above, the preset rotor dynamics design criteria include at least: only rigid body mode critical speed is allowed to appear within the working range, and the margin between the rigid body mode critical speed and the main working speed zone must be greater than 20%, and the rigid body mode rotor strain energy must be less than 25%; the bending critical speed must be greater than the maximum working speed, and the margin between the bending critical speed and the maximum working speed must be greater than 20%.

5. The method for robust design of connection stiffness of a rigid sleeve gear coupling of an engine pull-rod rotor according to claim 4, characterized in that: In the above step SS2, the optimization of the rotor structural parameters at least includes adjusting the rotor shaft diameter, shaft shoulder transition radius, shaft length and the structural shape of the coupling connection; the optimization of the support stiffness includes adjusting the stiffness coefficient of each support point, and at the same time performing a linear iteration of the elastic support stiffness of the support point by 20% above and below the initial assumed value; on the premise of meeting the rotor dynamics design criteria, a design scheme with simple structure and high processing accuracy is selected.

6. The method for designing the connection stiffness robustness of a rigid sleeve gear coupling of an engine pull-rod rotor according to claim 1, characterized in that: In step SS3, the strain energy density levels are divided into 10 levels from zero to maximum, with the lowest strain energy density being level 1 and the highest strain energy density being level 10. Levels 8 to 10 are defined as high strain energy density regions, and levels 1 to 3 are defined as low strain energy density regions.

7. The method for designing the connection stiffness robustness of a rigid sleeve gear coupling of an engine pull-rod rotor according to claim 1, characterized in that: In the above step SS5, if the rigid sleeve gear coupling is located near the main load-bearing rigid fulcrum, the coupling position is moved as close to the main load-bearing fulcrum as possible to fully utilize the high rigidity characteristics of the main load-bearing rigid fulcrum to further strengthen the rigidity of the coupling, while reducing the bending moment and shear force transmitted by the coupling.

8. The method for robust design of connection stiffness of a rigid sleeve gear coupling of an engine pull-rod rotor according to claim 1, characterized in that: In the above step SS5, the method of dividing the rotor equivalent stress level is: the rotor equivalent stress that meets the static strength requirements is divided into 10 levels from zero to maximum, the lowest stress is level 1, and the highest stress is level 10, and levels 1 to 2 are defined as low stress areas, which are used to judge whether the stress state of the coupling position is appropriate; low stress uniform deformation is defined as: meeting the structural function and assembly conditions of the sleeve gear coupling, being in the low stress area, and the static deformation of the positioning stop is uniform over the entire length range, and being able to achieve reliable positioning of at least 1 / 2 of the positioning length.

9. An engine tie rod type rigid sleeve gear coupling obtained based on the engine tie rod type rotor rigid sleeve gear coupling connection stiffness robustness design method according to any one of claims 1 to 8.

10. An aircraft engine or gas turbine, characterized in that: The invention comprises the engine pull rod type rigid sleeve gear coupling as described in claim 9.

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