Engine pull rod type rotor rigid sleeve gear coupling connection rigidity robustness design method and application thereof

Abstract

The invention discloses an engine pull rod type rotor rigid sleeve tooth coupling connection rigidity robustness design method and application thereof. The method is used for dynamic optimization design of a three-fulcrum supporting slender center pull rod rotor structure in an aero-engine or a gas turbine. According to the method, the rotor kinetic analysis finite element model is established, the critical rotating speed and strain energy density distribution of the rotor are calculated and analyzed, and the position and the structure of the coupler are optimally designed by combining static and dynamic strength requirements. The method comprises the steps of optimizing fulcrum rigidity and rotor structure parameters, analyzing the positioning reliability of a coupling positioning spigot, moving a coupling to a low strain energy density and low stress area, performing iterative verification and optimization and the like. By optimizing the position and the structure of the coupler, the connecting rigidity robustness of the coupler is improved, the dynamic performance of the rotor is optimized, the vibration risk of the rotor is reduced, and the method can be directly applied to engineering design of aero-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 a rotor structure, and specifically is a method for designing the connection stiffness robustness of a rigid sleeve gear coupling of an engine pull-rod rotor and its application, which is used to optimize the design of the rigid sleeve gear coupling. Background Art

[0002] Aeroengine rotor dynamics design is one of the core technologies of aeroengine design. Its main goal is to reduce the vibration of the entire engine to an acceptable level and provide a guarantee for the high reliability of the aircraft flight. To this end, rotor dynamics design must comply with strict design criteria. To meet the rotor dynamics design criteria, the first is to design the rotor stiffness, and the second is to design the support stiffness. When the support stiffness is constant, the rotor stiffness becomes the main factor affecting the rotor dynamic characteristics.

[0003] In the rotor system of an aircraft engine, when the shaft system structure is long and the overall structure is slender, in order to meet the actual needs of processing and assembly, a segmented shaft design is usually adopted. For example, the shaft can be made into a two-section shaft structure. The two sections of the shaft 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 needs to achieve a rigid connection between the two sections of the shaft through a precise sleeve gear structure, so that the rigidity of the rigid sleeve gear connection shaft is consistent with the rigidity of a whole shaft without connection, thereby minimizing the vibration problem caused by insufficient connection rigidity. However, in the prior art, 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 state of the locating spigot of the rigid sleeve gear coupling is an important factor in determining its stability. The locating spigot achieves precise connection of the shaft segments at both ends of the coupling through axial and radial fit. However, since the rotor is subjected to centrifugal force and other complex loads during operation, the fit state of the locating spigot may be affected, which is manifested as partial or complete detachment of the locating spigot. The instability of this fit state will further weaken the connection performance of the coupling.

[0006] In addition, in view of the special requirements of slender shaft structures, the 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] Although the concept of connection structure rigidity robustness has been proposed in rotor dynamics design, the connection structure robustness design is only a design requirement, without specific practical methods or the practical methods are only qualitative guidance, and a systematic optimization design method has not yet been formed. In view of the specific rotor structural characteristics, how to achieve the robustness design requirements of the rigid sleeve gear coupling, due to the lack of reliable reference basis, designers need to rely on experience and repeated tests to achieve the design goals according to the detailed situation, which is not only time-consuming and laborious, but also difficult to ensure the reliability and optimality of the design.

[0008] In summary, the existing technology still has many defects and shortcomings in the design of the connection stiffness of the rigid sleeve gear coupling. 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 urgently solved in the field of engine rotor dynamics design. Summary of the invention

[0009] 1. Purpose of the invention 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 a three-point supported slender center tie rod rigid sleeve gear coupling of an aircraft engine or gas turbine, the present invention provides a robustness design method for an engine tie rod type rigid sleeve gear coupling and its application. When the tie 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.

[0010] (II) Technical solution In order to achieve the purpose of the invention and solve the technical problems, the present invention adopts the following technical solutions: The first invention object of the present invention is to provide a method for designing the connection stiffness robustness 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 aero-engine or gas turbine, so as to improve the connection stiffness robustness of the rigid sleeve gear coupling, optimize the rotor dynamics performance, and reduce the risk of rotor vibration. The implementation steps of the design method are as follows: SS1. Initial structural rotor dynamics analysis finite element model establishment According to the two-dimensional structure diagram of the slender center tie 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. The initial support stiffness of each pivot point is assumed, and the critical speed and strain energy of the rotor within the preset speed range are calculated based on the FEM model. SS2. Optimization of rotor structural parameters and determination of support stiffness of each support point 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 vibration mode characteristics meet the design criteria, and finally determine the rotor structural parameters and the support stiffness of each support; SS3. Analysis of strain energy density distribution at the coupling at critical speed Based on the rotor structure and the support stiffness of each fulcrum 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, then proceed to step SS4; if it is at a high strain energy density level, then proceed to step SS5; SS4. Reliability analysis of the positioning of the coupling locating stop Analyze the positioning state of the positioning stop of the rigid sleeve gear coupling at the working speed, 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 stop length and is in a reliable positioning state. If the stop positioning length is less than 1 / 2 of the total stop length, proceed to step SS5 to optimize the coupling position and structure design. If it is not less than 1 / 2 of the total stop length, the stop positioning length meets the requirements and the design is completed. SS5. Optimized design of coupling position and structure Firstly, the equivalent stress distribution of the rotor structure at the working 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 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 the improved coupling structure is designed, and its geometric parameters and stop structure are adjusted; SS6. Verification and optimization of strain energy density of improved coupling structure 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 for loop iteration until the requirement is met. SS7. Verification and optimization of the positioning stop state of the improved coupling structure 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.

[0011] The second invention object of the present invention is to provide an engine tie rod type rigid sleeve gear coupling obtained based on the above-mentioned engine tie rod type rotor rigid sleeve gear coupling connection stiffness robustness design method. The coupling is located in the low strain energy density and low stress uniform deformation zone optimized and determined by the design method, has the advantages of high connection stiffness robustness, excellent rotor dynamics performance, and low vibration risk, and can effectively improve the stability and reliability of the three-point support slender center tie rod rotor system.

[0012] The third inventive 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.

[0013] (III) Technical Effect Compared with the prior art, the engine tie rod rotor rigid sleeve gear coupling connection stiffness robustness design method and application of the present invention have the following beneficial and significant technical effects: (1) This invention establishes a finite element model (FEM) for rotor dynamics analysis, combines quantitative analysis of critical speed, strain energy density and positioning reliability of the locating stop, and proposes a robust design of the rigid sleeve gear coupling from three aspects: rotor dynamic strength (i.e. rotor strain energy density during vibration) and static strength (i.e. the matching state of the locating stop under the action of centrifugal force), as well as the characteristics of the three-point rotor support structure. It also gives clear quantitative design requirements, which significantly improves the scientificity 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.

[0014] (2) The design method proposed in the present 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 and low stiffness loss, which can reduce the risk factors of large rotor vibration.

[0015] (3) By optimizing the stiffness configuration of the rotor support system and the layout position of the coupling, the present invention achieves a reasonable margin between the critical speed of the rotor and the operating speed, thereby avoiding resonance. In particular, under high-speed conditions, the present invention optimizes the radial deformation consistency of the positioning stop to ensure the stable connection of the coupling, thereby improving the dynamic performance of the rotor system and the reliability of the overall operation.

[0016] (4) The design method of the present invention has clear steps, rigorous logic, 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 general optimization design idea, which can be applied to a wide range of rotor dynamics optimization design scenarios and has important engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A flowchart of the implementation of the method for robustness design of the connection stiffness of the engine tie rod rotor rigid sleeve gear coupling provided by the embodiment of the present invention; Figure 2 It is a schematic diagram of the engine pull rod rotor structure; Figure 3 This is the original structural diagram of the rigid sleeve gear coupling; Figure 4 It is a schematic diagram of rotor strain energy density at the first critical speed; Figure 5 It is a schematic diagram of rotor strain energy density at the second critical speed; Figure 6 This is a schematic diagram of the stopper positioning state of the original structure; Figure 7 It is a schematic diagram of the improved structure of the coupling; Figure 8 This is a schematic diagram of the stop positioning status of the improved coupling structure. DETAILED DESCRIPTION

[0018] In order to better understand the present invention, the engine tie rod rotor rigid sleeve gear coupling connection stiffness robustness design method and its application are described in detail below in combination 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, and gradually analyzes and optimizes the structural parameters, positioning stop state and strain energy density distribution of the coupling to ultimately achieve coordinated optimization of dynamic and static performance. The following content is intended to provide a repeatable, scientific and rigorous implementation method that is convenient for direct application in engineering design.

[0019] in accordance with Figure 1 The process shown in the figure, the present invention realizes the robustness design of the connection stiffness of the engine tie rod type rigid sleeve gear coupling. Specifically, the design method of the present invention mainly includes the following steps when implemented: SS1. Initial structural rotor dynamics analysis finite element model establishment According to the two-dimensional structure diagram of the three-point supported slender center rod rotor in the engine, the rigid sleeve gear coupling is simplified to 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 3 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 rotor pivots are marked as pivot 1, pivot 2, and pivot 3 from the intake side to the exhaust side. Pivot 2 is the main load-bearing pivot and is designed as a rigid support with a support stiffness of 10 8 N / m level; pivot 1 and pivot 3 are the two end pivots, designed as elastic supports, and the support stiffness is 10 7 N / m level to simulate the rotor support characteristics under actual working conditions. By assuming the initial support stiffness of each support point, the critical speed and rotor strain energy of the rotor are calculated within the preset speed range based on the FEM model. 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 to ensure the completeness and accuracy of the analysis; the initial support stiffness of each support point is preliminarily set based on experience or design parameters of similar rotor systems for subsequent iterative optimization.

[0020] 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 assumptions, the alignment accuracy of the sleeve gear mating surfaces 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 dynamics behavior.

[0021] SS2. Optimization of rotor structural parameters and determination of support stiffness of each support point 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, under the overall structural boundary conditions, combine the FEM model to optimize the rotor structural parameters and the elastic support stiffness of each support, iterate repeatedly until the rotor critical speed, strain energy distribution and vibration mode characteristics meet the design criteria, and determine the final rotor structure and the support stiffness of each support. The final stiffness of the elastic supports at both ends is 1e7N / m, and the stiffness of the main load-bearing support is 1e8 N / m.

[0022] Preferably, the preset rotor dynamics design criteria at least include: there is only a rigid body vibration mode critical speed within the working range, the rigid body vibration mode critical speed has a margin of more than 20% from the main working speed zone, and the rigid body vibration mode 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 rotor structural parameters at least includes adjusting the rotor shaft diameter, shoulder transition radius, shaft length and structural shape of the coupling connection; the optimization of support stiffness includes adjusting the stiffness coefficient of each support point, and at the same time, the elastic support stiffness of the support point is linearly iterated by 20% up and down 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.

[0023] SS3. Analysis of strain energy density distribution at the coupling at critical speed Based on the rotor structure and the support stiffness of each support point determined after iterative optimization in step SS2, the FEM model is used to calculate the support stiffness and the rotor strain energy density at the critical speed under the determined structure, see 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 5It can be seen that at the first critical speed, the rotor strain energy density at the coupling is at the 8th to 10th level, and at the second critical speed, the rotor strain energy density at the coupling is also at the 8th to 10th level, which is a high strain energy density level; while the strain energy density at the main bearing support point 2 at the first critical speed and the second critical speed is at the first level, which is a low strain energy density level. According to the present invention, the rigid sleeve gear coupling can be moved to the main bearing support point 2.

[0024] Preferably, the strain energy density level classification method in the present invention is: the rotor strain energy density is divided into 10 levels from zero to maximum, the smallest strain energy density is the first level, the largest strain energy density is the tenth level, the 8th to 10th levels are defined as high strain energy density areas, and the 1st to 3rd levels are defined as low strain energy density areas. The calculation of the strain energy density is based on the determined rotor structural parameters and support stiffness, and is performed at the critical speed.

[0025] SS4. Reliability analysis of the positioning of the coupling locating stop Calculate the positioning state of the rigid sleeve gear coupling positioning stop at the working speed, see Figure 6 , analyze the radial deformation and positioning reliability of the locating stop, and determine whether the positioning length of the locating 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 stop positioning length is less than 1 / 2 of the total length of the stop, proceed to step SS5 to optimize the coupling position and structure design. If it is not less than 1 / 2 of the total length of the stop, the stop positioning length meets the requirements and the design is completed.

[0026] from Figure 6 It can be seen that at the working speed, only the corner point of the positioning stop is positioned, and the other positions of the stop are in a separated state, that is, the length of the positioning stop does not meet the requirement of the stop length greater than 1 / 2 proposed in the invention of this article. The main reason for the analysis is that the radial deformation of the positioning stop is inconsistent, one end is large and the other end is small. For this reason, the positioning stop needs to be moved to a position with greater rigidity. When the rigid sleeve gear coupling is moved to the fulcrum 2, the requirement of consistent radial deformation of the positioning stop can be achieved.

[0027] SS5. Optimal design of coupling position and structure Firstly, 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 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 the improved coupling structure is designed, and its geometric parameters and stop structure are adjusted.

[0028] Preferably, 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 rigid sleeve gear coupling is moved to the main load-bearing fulcrum 2 to improve the coupling structure design. Figure 7 .

[0029] 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 determine 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.

[0030] SS6. Verification and optimization of strain energy density of improved coupling structure Based on the coupling position and structure optimized in step SS5, the critical speed of the improved coupling structure and the strain energy density at the coupling are recalculated 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 for loop iteration until the requirement is met. In this embodiment, the position of the maximum strain energy density of the rotor at the critical speed is equivalent to that before the improvement, but because the position of the rigid sleeve gear coupling is changed to the main bearing support point 2, the strain energy density there is at a low strain energy density, so that the connection stiffness of the coupling will not be weakened when the rotor vibrates.

[0031] SS7. Verification and optimization of the positioning stop state of the improved coupling structure Based on the optimized coupling position and structure in step SS6, the positioning state of the positioning stop at the working speed of the improved coupling structure 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 to iterate until the stopper positioning length meets the requirement. Figure 8 It is known that the coupling has an improved structure and the positioning stop is well positioned within the entire length range. At this point, the robustness design of the rigid sleeve gear coupling is completed.

[0032] In summary, the present invention clarifies the robustness quantitative design method of the tie rod type rigid sleeve gear coupling. The method designs the robustness of the coupling from two aspects: strain energy density at the coupling and positioning reliability of the positioning stop. The rigid sleeve gear coupling designed according to the method has high robustness and low stiffness loss, and can reduce the risk factor of large rotor vibration. The design method is simple and easy to understand, has strong feasibility, and can directly guide the design of similar structural engineering of aircraft engines and gas turbines.

[0033] Through the above embodiments, the purpose of the present invention is fully and effectively achieved. Those skilled in the art can understand that the present invention includes but is not limited to the contents described in the drawings and the above specific embodiments. Although the present invention has been described with respect to the most practical and preferred embodiments currently considered, it should be understood that the present invention is not limited to the disclosed embodiments, and any modification that does not deviate from the functional and structural principles of the present invention will be included in 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. According to the two-dimensional structure diagram of the slender center tie 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 FEM model of the initial structure is established. The initial support stiffness of each pivot point is assumed, and the critical speed and strain energy of the rotor within the preset speed range are calculated based on the FEM model; SS2. 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, 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 by combining the FEM model until the rotor critical speed, strain energy distribution and vibration mode characteristics meet the design criteria, and finally the rotor structural parameters and the support stiffness of each support point are determined; SS3. Based on the rotor structure and the 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; SS4. Analyze the positioning state of the positioning stop of the rigid sleeve gear coupling at the working speed, 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, proceed 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 requirement and the design is completed. SS5. 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 is improved and designed, and its geometric parameters and stop structure are adjusted; 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 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 for loop iteration 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 positioning stop at the working speed of the improved coupling structure 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.

2. The method for robustness 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 SS1, the establishment of the FEM model includes the simplification of the geometric features of the rotor shaft and the setting of parametric constraints for 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 assumptions, the alignment accuracy of the sleeve gear mating surface and the symmetry of the coupling geometric center to the rotor shaft center.

3. The method for designing the connection stiffness robustness of the engine tie rod rotor rigid sleeve gear coupling 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; and when establishing the FEM model, the structure of the three-point support slender center rod rotor is simplified to a three-point support, and the three fulcrums are marked as fulcrum I, fulcrum II and fulcrum III from the intake side to the exhaust side, where fulcrum I and fulcrum III are elastic supports, fulcrum II is the main load-bearing rigid support, and it is assumed that the support stiffness of fulcrum I and fulcrum III is 10 7 N / m level, the support stiffness of fulcrum II is 10 8 N / m order of magnitude.

4. The method for robustness 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 SS2, the preset rotor dynamics design criteria at least include: only rigid body vibration mode critical speed is allowed to appear within the working range, and the margin of rigid body vibration mode critical speed from the main working speed zone must be greater than 20%, and the rigid body vibration mode rotor strain energy must be less than 25%; the bending critical speed must be greater than the maximum working speed, and the margin from the maximum working speed must be greater than 20%.

5. The method for robustness design of connection stiffness of engine tie rod rotor rigid sleeve gear coupling 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, the shoulder transition radius, the shaft length and the structural shape of the coupling connection; the optimization of the support stiffness includes adjusting the stiffness coefficient of each fulcrum, and at the same time performing a linear iteration of 20% up and down on the elastic support stiffness of the fulcrum 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.

6. The engine tie rod rotor rigid sleeve gear coupling connection stiffness robustness design method according to claim 1, characterized in that: In the above step SS3, the strain energy density level is divided into 10 levels from zero to the maximum, the smallest strain energy density is the first level, the largest strain energy density is the tenth level, the 8th to 10th levels are defined as high strain energy density areas, and the 1st to 3rd levels are defined as low strain energy density areas.

7. The method for designing the connection stiffness robustness of the engine tie rod rotor rigid sleeve gear coupling 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 robustness 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 for 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 the first level, and the highest stress is the tenth level, and the 1st to 2nd levels 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, the static deformation of the locating 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 as described in any one of claims 1 to 8.

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

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