A stiffness design method and application of a compact main bearing structure of a three-point engine

Abstract

The present invention discloses a three-pivot engine compact main load-bearing structure stiffness design method and application. When the method is implemented: first, the determined rotor structure support stiffness is iteratively optimized and designed to determine the stiffness of each support; second, the static strength and each support stiffness of the initial stator assembly are analyzed. If the static strength and support stiffness requirements are not met, the stator assembly is optimized, and the stator assembly structure determined for the first time is obtained after optimization; then, the coaxiality of each support of the stator assembly determined for the first time is analyzed. If the requirements are not met, the main load-bearing structure is optimized, and the stator assembly structure determined again is obtained after optimization; finally, the static strength and support stiffness of the stator assembly determined again are analyzed. If the requirements are met, the final stator assembly structure is obtained, otherwise iterative optimization is performed. The present invention can significantly improve the vibration performance and structural reliability of the whole machine, and is suitable for the engineering design of aircraft engines and gas turbines.

Description

Technical Field

[0001] The present invention belongs to the technical field of vibration control of aircraft engines and gas turbines, and relates to the stiffness design of engine support structures. Specifically, it provides a stiffness design method and application of a compact main load-bearing structure of a three-point engine, which is used to reduce the vibration of the entire engine and improve the reliability and service life of the engine. Background Art

[0002] Whole-engine vibration control technology is a core technology in aircraft engine design. Its purpose is to reduce the overall engine vibration to an acceptable level, ensuring safe and reliable aircraft operation. The main structural factors affecting whole-engine vibration are rotor stiffness and load-bearing structure stiffness. Once the rotor stiffness is determined, the load-bearing structure stiffness becomes the decisive factor influencing the overall engine vibration characteristics. In particular, the stiffness design of the main load-bearing structure is of paramount importance. As the primary load-bearing structure of the entire rotor, it plays a primary supporting role. Insufficient load-bearing structure stiffness or improper distribution can lead to significant vibration responses during engine operation, thereby affecting its dynamic stability and reliability.

[0003] When an aircraft engine's rotor is slender, three pivots are typically designed to enhance the rotor's support stiffness and raise the critical bending speed beyond the operating speed to meet rotor dynamics requirements. However, engines with three-pivot support structures often suffer from misalignment, leading to significant vibration and adversely affecting engine performance. This misalignment is often closely related to the stiffness design of the primary support. Improper stiffness design of the primary support can lead to significant differences in deformation among the three pivots, resulting in significant misalignment.

[0004] Large aircraft engines are usually equipped with an independent main load-bearing casing, which mainly plays a supporting role and does not bear the aerodynamic boosting function. It mainly bears inertial loads such as vibration and overload, and has a larger structural rigidity and smaller aerodynamic load. In contrast, small aircraft engines are small in size and compact in structure. The front and rear bearing seats of the compressor are usually integrated with the compressor stator blades to play a supporting role. The rear fulcrum of the compressor is the main load-bearing fulcrum. The bearing seat of the main load-bearing fulcrum is integrated with the installation section of the compressor last stage stator blade and the stator blade outer ring to form the main load-bearing structure. The pressure on one side of the main load-bearing bearing seat is the outlet pressure of the compressor last stage stator blade. After aerodynamic boosting, the pressure is high, and the pressure on the other side is low. The aerodynamic pressure difference on both sides of the bearing seat is large. At the same time, it also has to bear inertial loads such as vibration and overload. That is, the compact main load-bearing structure of a small aircraft engine has to bear more complex loads than that of a large engine. See the structural diagram. Figure 1 The turbine end support point of a small aircraft engine is connected to the main load-bearing support point through an internal force transmission bearing seat. When the main load-bearing structure has a small deformation, it will cause large deformation of the front and rear support points, resulting in an increase in the misalignment of the three support points.

[0005] From an engineering perspective, existing main support structure stiffness design focuses primarily on meeting rotor dynamics requirements and the static strength design of the stator assembly, with limited consideration given to the impact of the three-point structural stiffness on support misalignment. In particular, after meeting the static strength requirements of the main bearing structure, engineering design experience and theoretical research on further optimizing support stiffness to improve three-point coaxiality is still incomplete. Furthermore, traditional design methods fail to adequately analyze the deformation characteristics of the stator assembly under complex loads, resulting in design solutions that are prone to exceeding the vibration standard of the entire machine in actual application.

[0006] In summary, existing technologies have significant flaws and deficiencies in the design of the main bearing support stiffness for three-pivot engines. On the one hand, the design of the main bearing support stiffness fails to fully consider the combined effects of the static strength of the stator assembly, rotor dynamics, and support coaxiality. On the other hand, existing design methods lack systematicity and are unable to meet the multi-dimensional requirements of small engines under complex load conditions. Therefore, how to systematically optimize the main bearing support stiffness design to meet both static strength and dynamic performance requirements while ensuring support coaxiality requirements is a technical problem that needs to be urgently addressed in the field of engine vibration control. Summary of the Invention

[0007] (1) Purpose of the invention

[0008] In response to the above-mentioned defects and deficiencies in the prior art, and to address the problems of increased overall vibration, insufficient static strength of the stator assembly, and limited rotor dynamics performance caused by misalignment of the fulcrums in the stiffness design of the main bearing structure of a three-pivot engine, the present invention provides a compact main bearing structure stiffness design method for a three-pivot engine and its application. The method comprises the following steps: first, by iteratively optimizing the stator assembly structure, analyzing the static strength and stiffness of each fulcrum to ensure that the static strength requirements and rotor dynamics requirements are met; second, by iteratively optimizing the main bearing structure, analyzing the misalignment of each fulcrum based on the deformation of each fulcrum to ensure that the misalignment requirements are met; and third, by analyzing the static strength, fulcrum stiffness, and misalignment of the optimized stator assembly, ensuring that the static strength, fulcrum stiffness, and misalignment of the final structure all meet the requirements. This method effectively reduces overall vibration while meeting the stator assembly strength and rotor dynamics requirements, improving the reliability and applicability of the main bearing structure, and providing effective guidance for the design of similar structures in aircraft engines and gas turbines.

[0009] (2) Technical solution

[0010] In order to achieve the purpose of the invention and solve the technical problems, the present invention adopts the following technical solutions:

[0011] The first object of the present invention is to provide a method for designing the stiffness of a compact main bearing structure of a three-pivot engine, which is used to optimize the stiffness design of the main bearing structure in the three-pivot engine, meet the comprehensive design requirements of the static strength of the stator assembly, the dynamic performance of the rotor, and the coaxiality of the fulcrum, and solve the problem of increased vibration of the entire engine caused by the misalignment of the fulcrums. The method is implemented in the following steps:

[0012] SS1. Establishing a finite element model for rotor dynamics analysis

[0013] Based on the determined three-point supported engine rotor structure, a finite element model for rotor dynamics analysis was established. Assuming initial stiffness values ​​for the compressor front support, the main load-bearing support, and the turbine end support, critical speed and rotor strain energy analysis of the rotor structure were performed to identify dynamic constraints within the operating range, including margins for the two-order rigid body modal critical speed and bending critical speed.

[0014] SS2. Support stiffness optimization and determination of each support stiffness

[0015] Based on the rotor dynamics analysis results of step SS1, the stiffness of each support point is optimized through repeated iterations, and the support stiffness distribution is adjusted to meet the critical speed and strain energy requirements. This ensures that the margin between the critical speed of the rigid body vibration mode of the rotor and the operating speed is greater than 20%, and that the bending critical speed is greater than the maximum operating speed with a margin of not less than 20%. Finally, the optimized stiffness values ​​of the compressor front support point, the main bearing support point, and the turbine end support point that meet the critical speed and strain energy requirements are determined;

[0016] SS3. Establish the initial finite element model for static strength analysis of the stator assembly

[0017] Based on the fulcrum stiffness values ​​optimized and determined in step SS2, a static strength analysis finite element model of the complete initial stator assembly including the main load-bearing structure is established, and by constraining the degrees of freedom of the mounting node position in the stator assembly, steady-state static loads and maneuvering flight loads are applied to calculate the static stress distribution of the stator assembly to determine whether its static strength meets the requirements of the static strength design criteria. At the same time, based on the deformation results of each fulcrum, the actual stiffness value of each fulcrum is calculated to determine whether the actual stiffness of each fulcrum meets the rotor dynamics design requirements.

[0018] SS4. Iteratively optimize the stator assembly structure to meet static strength and stiffness requirements

[0019] In case the static strength of the stator assembly is insufficient or the support stiffness does not meet the rotor dynamics requirements in step SS3, the stator assembly structure is repeatedly optimized by changing its geometric dimensions, material distribution and / or local structural design until the stator assembly meets the static strength design criteria and ensures that the stiffness of each support meets the rotor dynamics design requirements, thereby forming a first determined stator assembly structure scheme;

[0020] SS5. First determination of the misalignment analysis of each support point in the stator assembly structure

[0021] Based on the static strength analysis results of the stator assembly initially determined in step SS4, the deformation of the compressor front support point, the main load-bearing support point, and the turbine end support point in the vertical direction are analyzed, and the misalignment between the support points is analyzed based on the deformation results of each support point to determine whether the misalignment of the three support points is less than a preset threshold value. If the misalignment of the three support points exceeds the preset threshold value, the process proceeds to step SS6 to optimize the main load-bearing structure in the stator assembly. If the misalignment is less than the preset threshold value, the process proceeds to step SS7.

[0022] SS6. Iteratively optimize the main load-bearing structure and re-determine the stator assembly structure

[0023] In the case where the misalignment of the three support points exceeds the preset threshold in step SS5, the main load-bearing structure of the stator assembly is repeatedly optimized by iterative optimization, including adjusting the thickness of the load-bearing support plate, changing the structural shape and / or adding reinforcement ribs at key positions to increase the stiffness of the main load-bearing structure and reduce its deformation under load, until the misalignment of the support points meets the requirement of being less than the preset threshold, thereby obtaining a re-determined stator assembly structure;

[0024] SS7. Verify the optimized stator assembly and determine the final structure

[0025] For the stator assembly structure determined again in step SS6, the static strength and support stiffness of the stator assembly determined again are analyzed using the static strength finite element model to verify whether they meet both the static strength requirements and the rotor dynamics design requirements. If not, return to step SS4 for a loop iteration. If they meet the requirements, the stator assembly and its main load-bearing structure are determined as the final design scheme to ensure its high reliability and applicability under complex load conditions.

[0026] Through the above steps, the present invention comprehensively considers the requirements of the static strength of the stator assembly, the dynamic performance of the rotor and the coaxiality of the support point, and provides a systematic main load-bearing support stiffness design method, which significantly reduces the vibration of the whole machine and improves the reliability and applicability of the main load-bearing structure. It can be widely used in the optimization design of the main load-bearing structure of aircraft engines and gas turbines.

[0027] The second object of the present invention is to provide a three-pivot engine compact main load-bearing structure, the stiffness design of which is based on the above-mentioned three-pivot engine compact main load-bearing structure stiffness design method of the present invention.

[0028] The third object of the present invention is to provide a three-pivot compact engine, including the above-mentioned three-pivot engine compact main bearing structure of the present invention.

[0029] (3) Technical effects

[0030] Compared with the prior art, the stiffness design method and application of the three-pivot engine compact main bearing structure of the present invention has the following beneficial and significant technical effects:

[0031] (1) The present invention designs the main load-bearing structure stiffness from multiple perspectives, targeting various factors that cause large vibrations of the entire machine. The stator assembly strength and main load-bearing structure stiffness are designed not only from the perspectives of the static strength of the stator assembly and the dynamics of the rotor, but also from the perspective of the axiality of the three supports to avoid large vibrations of the entire machine caused by the misalignment of the three supports. This achieves a comprehensive optimization design of the static strength of the stator assembly, the dynamic performance of the rotor, and the coaxiality of the supports. Ultimately, a main load-bearing structure that meets all design requirements is obtained, thereby significantly reducing the vibration amplitude of the entire machine and improving the dynamic stability of the system.

[0032] (2) The design process proposed in the present invention combines finite element analysis with engineering optimization methods. By iteratively optimizing the geometric parameters, material distribution and local stiffness design of the stator assembly and the main load-bearing structure, the designed main load-bearing structure has high reliability and the probability of large vibration problems of the whole machine is low. It has strong operability in technical implementation and can directly guide the engineering design of similar structures of aircraft engines and gas turbines. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of the stator assembly structure;

[0034] Figure 2 A flow chart for stiffness design of a compact main bearing structure of a three-point engine provided by the present invention;

[0035] Figure 3 Schematic diagram of the preliminarily determined main load-bearing structure, where: (a) is the fourth-stage stator, (b) is the installation section;

[0036] Figure 4 Schematic diagram of the vertical static deformation of the stator assembly;

[0037] Figure 5 Schematic diagram of the main load-bearing structure that has been re-determined, where: (a) is the optimized fourth-stage stator, and (b) is the optimized installation section. DETAILED DESCRIPTION

[0038] In order to better understand the present invention, the following embodiments are further described to further illustrate the content of the present invention. In order to better understand the characteristics and engineering applicability of the present invention, Figure 2The process shown achieves the stiffness design of the compact main load-bearing structure of the three-pivot engine. It should be noted that the embodiments described are only part of the embodiments of the present invention, not all of them, and the embodiments described are exemplary and intended to be used to explain the present invention, and should not be understood as limiting the present invention.

[0039] In an embodiment of the present invention, Figure 2 As shown, the stiffness design method for the compact main bearing structure of a three-pivot engine mainly includes the following steps when implemented:

[0040] SS1. Establishing a finite element model for rotor dynamics analysis

[0041] Based on the determined three-point supported engine rotor structure, a finite element model for rotor dynamics analysis is established. Assuming the initial stiffness values ​​of the compressor front support, the main load-bearing support and the turbine end support in the three-point support, the critical speed and rotor strain energy of the rotor structure are analyzed, and the dynamic constraints within the working range are identified, including the margins for the two-order rigid body vibration mode critical speed and the bending critical speed.

[0042] Preferably, the establishment of the finite element model for rotor dynamics analysis includes at least the definition of the geometric parameters, material properties, boundary conditions and load conditions of the rotor structure, wherein the boundary conditions are set by simulating the constraints of each support point, the load conditions include the rotor inertia load and aerodynamic load, and the analysis content includes the rotor rigid body vibration critical speed, bending critical speed and rotor strain energy distribution, to ensure that the calculation results cover all key dynamic states within the engine operating range.

[0043] SS2. Support stiffness optimization and determination of each support stiffness

[0044] Based on the rotor dynamics analysis results of step SS1, the stiffness of each support is optimized through repeated iterations and the support stiffness distribution is adjusted to ensure that the critical speed and strain energy meet the requirements, ensure that the margin between the critical speed of the rigid body vibration mode of the rotor and the operating speed is greater than 20%, and that the bending critical speed is greater than the maximum operating speed with a margin of not less than 20%. Finally, the optimized stiffness values ​​of the compressor front support, main load-bearing support, and turbine end support that meet the critical speed and strain energy requirements are determined.

[0045] In this embodiment, the final stiffness of the front section support of the compressor is determined to be 1×10 7 N / m, the stiffness of the compressor rear end support point, i.e. the main load-bearing support point, is 1×10 8 N / m, the turbine end support stiffness is 1×10 7 N / m.

[0046] SS3. Establish the initial finite element model for static strength analysis of the stator assembly

[0047] According to the fulcrum stiffness value optimized and determined in step SS2, a static strength analysis finite element model of the complete initial stator assembly including the main load-bearing structure is established. By constraining the degrees of freedom of the installation node position in the stator assembly, steady-state static loads and maneuvering flight loads are applied, and the static stress distribution of the stator assembly is calculated to determine whether its static strength meets the requirements of the static strength design criteria. At the same time, the actual stiffness value of each fulcrum is calculated based on the deformation results of each fulcrum to determine whether the actual stiffness of each fulcrum meets the rotor dynamics design requirements.

[0048] As a preference, the establishment of a finite element model for static strength analysis of the stator assembly includes the definition of the geometric model, material model, load conditions and boundary conditions of the stator assembly. The static load conditions include aerodynamic loads, inertial loads and installation loads under steady-state static loads. The maneuvering flight loads include the overload and vibration loads of the engine under different flight conditions. The boundary conditions are set by constraining the degrees of freedom of the connection between the stator assembly and the rotor assembly, and the static stress distribution is used to determine whether the stator assembly meets the static strength design criteria. The static strength analysis criteria are based on the relationship between the yield strength and maximum stress of the material, and are adopted. As a design criterion to ensure that the stator assembly has sufficient strength margin under the design conditions, is the maximum stress value in the structure of the stator assembly after the steady-state static load and maneuvering flight load are applied, is the yield strength of the material and 0.9 is the safety factor.

[0049] In this embodiment, based on the established initial static strength analysis finite element model of the stator assembly, the installation joint position freedom is constrained, and steady-state static loads and maneuvering flight loads are applied. After calculation, the static stress of the stator assembly meets The calculation shows that the compressor front support bearing casing stiffness is 2.5×10 7 N / m, and the elastic ring stiffness is 8.4×10 6 N / m, and after the stiffness combination, the stiffness of the front support point of the compressor is 6.3×10 6 The stiffness of the compressor rear support point, i.e. the main load-bearing support point, is 8.6×10 7 N / m, and the turbine end support stiffness is 3.7×10 6 N / m. Under this stiffness, there are two-order rigid body vibration mode critical speeds within the working range, with a margin of more than 20% from the working speed. The bending critical speed is greater than the maximum speed, with a margin of 30%, which meets the rotor dynamics requirements. The corresponding stator assembly structure is the stator assembly structure determined for the first time, see Figure 3 .

[0050] SS4. Iteratively optimize the stator assembly structure to meet static strength and stiffness requirements

[0051] In response to the situation in step SS3 where the static strength of the stator assembly is insufficient or the support stiffness does not meet the rotor dynamics requirements, the stator assembly structure is repeatedly optimized iteratively, including changing its geometric dimensions, material distribution and / or local structural design, until the stator assembly meets the static strength design criteria requirements and ensures that the stiffness of each support meets the rotor dynamics design requirements, thereby forming the first determined stator assembly structure scheme.

[0052] Preferably, the iterative optimization of the stator assembly structure includes thickening the thin-wall structure of the stator assembly, strengthening the material of the stator assembly, and optimizing the local support structure of key parts. By gradually adjusting the geometric parameters and material properties of the stator assembly, the safety of the stator assembly under complex load conditions is ensured, and the fulcrum stiffness is improved to meet the rotor dynamics design requirements and avoid the fulcrum misalignment problem caused by excessive deformation.

[0053] In this embodiment, the vertical deformation of each support point is obtained from the static strength result of the stator assembly determined for the first time, see Figure 4 . The vertical deformation of the front support of the compressor is 0.095mm, the vertical displacement of the rear support of the compressor, that is, the main load-bearing support, is approximately zero, and the vertical displacement of the turbine end support is -0.12mm. It can be seen that the axial misalignment of the front support of the compressor and the turbine end support relative to the main load-bearing support is greater than 0.03mm, which does not meet the support coaxiality requirement of less than 0.03mm. Analysis of the reasons shows that, first, the pressure difference on both sides of the main load-bearing structure is large, reaching 3-5 atmospheres; second, the fourth-stage stator casing of the compressor is a thin-walled structure with low rigidity. The mounting section is directly integrated with the fourth-stage stator casing. The low casing rigidity leads to low mounting section rigidity.

[0054] SS5. Secondary determination of the axial misalignment of each support point in the stator assembly structure

[0055] Based on the static strength analysis results of the stator assembly determined for the first time in step SS4, the deformation of the compressor front support, the main load-bearing support and the turbine end support in the vertical direction are analyzed, and the different axialities between the supports are analyzed according to the deformation results of each support to determine whether the different axialities of the three supports are less than the preset threshold. If the different axialities of the three supports exceed the preset threshold, proceed to step SS6 to optimize the main load-bearing structure in the stator assembly. If it is less than the preset threshold, proceed to step SS7.

[0056] Preferably, the analysis of the different axialities of the three supports includes calculating the deformation of the compressor front support, the main load-bearing support and the turbine end support in the vertical direction, and determining the different axialities by comparing the deformation differences of each support. At the same time, combined with the static strength analysis results of the stator assembly, the main reasons for the excessive different axialities are identified, including insufficient stiffness of the main load-bearing structure, excessive difference in support load or excessive deformation of the thin-walled structure, and providing specific improvement directions for the optimization of the main load-bearing structure; and wherein, the preset threshold is determined to be 0.03 mm based on the vibration control requirements of the engine as a whole and engineering experience, so as to ensure that the coaxiality of the three supports meets the requirements for stable operation of the engine.

[0057] In this embodiment, the main load-bearing structure stiffness is optimized from two aspects: one is to thicken the thickness of the main load-bearing structure support plate; the other is to set reinforcement ribs at the fourth-stage stator casing of the compressor to enhance the stiffness of the installation section. The optimized main load-bearing structure is shown in FIG. Figure 5 After optimization, the vertical displacement of the compressor front support under the static load of the main load-bearing structure is 0.003mm. The vertical displacement of the compressor rear support, the main load-bearing support, is approximately zero. The vertical displacement of the turbine end support is -0.01mm. The coaxiality of the three supports meets the requirement of less than 0.03mm. The stator assembly after the optimization of the main load-bearing structure is the re-determined stator assembly structure.

[0058] SS6. Iteratively optimize the main load-bearing structure and re-determine the stator assembly structure

[0059] In the case where the misalignment of the three supports exceeds the preset threshold in step SS5, the main load-bearing structure of the stator assembly is repeatedly optimized by iterative optimization, including adjusting the thickness of the load-bearing support plate, changing the structural shape and / or adding reinforcing ribs at key positions to increase the stiffness of the main load-bearing structure and reduce its deformation under load, until the misalignment of the supports meets the requirement of being less than the preset threshold, and the stator assembly structure is re-determined.

[0060] Preferably, the iterative optimization of the main load-bearing structure includes: improving the overall stiffness of the main load-bearing support by adjusting the thickness of the load-bearing support plate, locally strengthening the thin-walled structure with reinforcing ribs to reduce deformation, optimizing the geometric shape of the main load-bearing support to improve load distribution, and enhancing the material properties of the main load-bearing structure at the same time, and verifying the effectiveness of the optimization measures in combination with finite element analysis, until the misalignment of the three supports is less than a preset threshold.

[0061] In this embodiment, after optimization, the compressor front support bearing casing stiffness is 5.4×10 7 N / m, and the elastic ring stiffness is 8.4×10 6 N / m, the combined stiffness of the front support of the compressor is 7.2×10 6 N / m. The stiffness of the compressor rear support point, i.e. the main load-bearing support point, is 1.3×10 8N / m, and the turbine end support stiffness is 6.2×10 6 N / m. Under this stiffness, there are two-order rigid body vibration critical speeds within the working range, with a margin of more than 20% from the working speed, and the bending critical speed is greater than the maximum speed, with a margin of 46%, meeting the rotor dynamics requirements. After calculation, the static stress of the stator assembly after optimization also meets This stator assembly structure is the final stator assembly structure.

[0062] SS7. Verify the optimized stator assembly and determine the final structure

[0063] For the stator assembly structure determined again in step SS6, the static strength and support stiffness of the stator assembly determined again are analyzed using the static strength finite element model to verify whether they meet both the static strength requirements and the rotor dynamics design requirements. If not, return to step SS4 for a loop iteration. If they meet the requirements, the stator assembly and its main load-bearing structure are determined as the final design scheme to ensure its high reliability and applicability under complex load conditions.

[0064] As a preference, the final verification of the stator assembly structure includes a comprehensive assessment of the static strength, fulcrum stiffness and fulcrum coaxiality of the stator assembly, wherein the static strength of the stator assembly must meet The design criteria are as follows: the fulcrum stiffness must meet the rotor dynamics performance requirements, the fulcrum coaxiality must be less than 0.03mm, and the reliability under different design conditions is verified through multiple cycles of iteration to ensure the high reliability and high applicability of the stator assembly under complex load conditions.

[0065] In summary, this invention defines a method for designing the stiffness of a compact three-pivot engine's primary load-bearing structure. This design considers not only the static strength of the stator assembly and rotor dynamics but also the coaxiality of the three pivots, thereby reducing the likelihood of overall engine vibration. Furthermore, this design method is highly applicable in engineering practice and can directly guide the design of similar structures for aircraft engines and gas turbines.

[0066] 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 designing the stiffness of a compact main bearing structure of a three-point engine, characterized in that: The design method comprises at least the following steps when implemented: SS1. Based on the determined three-point supported engine rotor structure, a finite element model for rotor dynamics analysis was established. Assuming initial stiffness values ​​for the compressor front support, the main load-bearing support, and the turbine end support, critical speed and rotor strain energy analysis of the rotor structure was performed. Dynamic constraints within the operating range were identified, including margins for the second-order rigid body modal critical speed and bending critical speed. SS2. Based on the rotor dynamics analysis results from step SS1, optimize the stiffness of each pivot point through repeated iterations and adjust the pivot stiffness distribution to meet critical speed and strain energy requirements. Ensure that the rotor's rigid-body mode critical speed has a margin greater than 20% from the operating speed and that the bending critical speed is greater than the maximum operating speed by at least 20%. Finally, determine the optimized stiffness values ​​for the compressor front pivot point, main bearing pivot point, and turbine end pivot point that meet the critical speed and strain energy requirements. SS3. Based on the pivot stiffness values ​​optimized and determined in step SS2, a static strength analysis finite element model of the complete initial stator assembly, including the primary load-bearing structure, is established. By constraining the degrees of freedom of the mounting joint positions within the stator assembly, steady-state static loads and maneuvering flight loads are applied to calculate the static stress distribution of the stator assembly to determine whether its static strength meets the static strength design criteria. Furthermore, the actual stiffness of each pivot is calculated based on its deformation results to determine whether the stiffness of each pivot meets the rotor dynamics design requirements. SS4. If the static strength of the stator assembly is insufficient or the support stiffness does not meet the rotordynamic requirements in step SS3, iteratively optimize the stator assembly structure, including changing its geometric dimensions, material distribution, and / or local structural design, until the stator assembly meets the static strength design requirements and ensures that the stiffness of each support meets the rotordynamic design requirements, thus forming a preliminary stator assembly structural solution. SS5. Based on the static strength analysis results of the stator assembly initially determined in step SS4, analyze the vertical deformation of the compressor front support, the main load-bearing support, and the turbine end support. Based on the deformation results of each support, analyze the misalignment between the support points and determine whether the misalignment between the three support points is less than a preset threshold. If the misalignment between the three support points exceeds the preset threshold, proceed to step SS6 to optimize the main load-bearing structure of the stator assembly. If the misalignment is less than the preset threshold, proceed to step SS7. SS6. If the misalignment at the three supports exceeds the preset threshold in step SS5, iteratively optimize the stator assembly's primary load-bearing structure. This may involve adjusting the thickness of the load-bearing support plates, modifying the structural shape, and / or adding reinforcement ribs at key locations to increase the primary load-bearing structure's stiffness and reduce its deformation under load, until the misalignment is below the preset threshold. This results in a redefined stator assembly structure. SS7. Analyze the static strength and support stiffness of the stator assembly re-determined in step SS6 using the static strength finite element model to verify whether it meets both the static strength requirements and the rotor dynamics design requirements. If not, return to step SS4 and iterate. If so, determine the final design for the stator assembly and its primary load-bearing structure.

2. The method for designing the stiffness of a compact main bearing structure of a three-pivot engine according to claim 1, characterized in that: In the above step SS1, the establishment of the finite element model for rotor dynamics analysis includes at least the definition of the geometric parameters, material properties, boundary conditions and load conditions of the rotor structure. The boundary conditions are set by simulating the constraints of each support point. The load conditions include rotor inertia load and aerodynamic load. The analysis content includes the rotor rigid body vibration critical speed, bending critical speed and rotor strain energy distribution, ensuring that the calculation results cover all key dynamic states within the engine operating range.

3. The method for designing the stiffness of a compact main bearing structure of a three-pivot engine according to claim 1, characterized in that: In the above step SS3, the establishment of the finite element model for static strength analysis of the stator assembly includes the definition of the geometric model, material model, load conditions and boundary conditions of the stator assembly. The static load conditions include the aerodynamic load, inertial load and installation load under the action of steady-state static load. The maneuvering flight load includes the overload and vibration load of the engine under different flight conditions. The boundary conditions are set by constraining the degrees of freedom of the connection between the stator assembly and the rotor assembly, and the static stress distribution is used to determine whether the stator assembly meets the static strength design criteria.

4. The method for designing the stiffness of a compact main bearing structure of a three-pivot engine according to claim 1, characterized in that: In the above step SS3, the static strength analysis criterion is based on the relationship between the yield strength and maximum stress of the material, using σ max <0.9 σ 0.2 As a design criterion to ensure that the stator assembly has sufficient strength margin under the design conditions, σ max is the maximum stress value in the structure of the stator assembly after the steady-state static load and maneuvering flight load are applied, σ 0.2 is the yield strength of the material and 0.9 is the safety factor.

5. The method for designing the stiffness of a compact main bearing structure of a three-pivot engine according to claim 1, characterized in that: In the above step SS4, the iterative optimization of the stator assembly structure includes thickening the thin-wall structure of the stator assembly, strengthening the material of the stator assembly, and optimizing the local support structure of key parts. By gradually adjusting the geometric parameters and material properties of the stator assembly, the safety of the stator assembly under complex load conditions is ensured, and the fulcrum stiffness is improved to meet the rotor dynamics design requirements and avoid the fulcrum misalignment problem caused by excessive deformation.

6. The method for designing the stiffness of a compact main bearing structure of a three-pivot engine according to claim 1, characterized in that: In the above step SS5, the analysis of the different axialities of the three supports includes calculating the deformation of the compressor front support, the main load-bearing support and the turbine end support in the vertical direction, and determining the different axialities by comparing the deformation differences of each support. At the same time, combined with the static strength analysis results of the stator assembly, the main reasons for the excessive different axialities are identified, including insufficient stiffness of the main load-bearing structure, excessive difference in support load or excessive deformation of the thin-walled structure, and providing specific improvement directions for the optimization of the main load-bearing structure; and wherein, the preset threshold is determined to be 0.03 mm based on the vibration control requirements of the engine as a whole and engineering experience to ensure that the coaxiality of the three supports meets the requirements for stable operation of the engine.

7. The method for designing the stiffness of a compact main bearing structure of a three-pivot engine according to claim 1, characterized in that: In the above step SS6, the iterative optimization of the main load-bearing structure includes: improving the overall stiffness of the main load-bearing support by adjusting the thickness of the load-bearing support plate, locally strengthening the thin-walled structure with reinforcing ribs to reduce deformation, optimizing the geometric shape of the main load-bearing support to improve load distribution, and enhancing the material properties of the main load-bearing structure at the same time, and verifying the effectiveness of the optimization measures in combination with finite element analysis, until the axial misalignment of the support is less than the preset threshold.

8. The method for designing the stiffness of a compact main bearing structure of a three-pivot engine according to claim 1, characterized in that: In the above step SS7, the final verification of the stator assembly structure includes a comprehensive evaluation of the static strength, support stiffness and support coaxiality of the stator assembly, wherein the static strength of the stator assembly must meet σ max <0.9 σ 0.2 The design criteria are as follows: the fulcrum stiffness must meet the rotor dynamics performance requirements, the fulcrum coaxiality must be less than 0.03mm, and the reliability under different design conditions is verified through multiple cycles of iteration to ensure the high reliability and high applicability of the stator assembly under complex load conditions.

9. A three-point engine compact main bearing structure, characterized by: Its stiffness design is based on the stiffness design method of a compact main load-bearing structure of a three-pivot engine as described in any one of claims 1 to 8.

10. A three-pivot compact engine, characterized in that: It includes the three-point engine compact main load-bearing structure described in claim 9.

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