Rigidity design method and application of compact main load-bearing structure of three-fulcrum engine

Abstract

The invention discloses a three-fulcrum engine compact type main load-bearing structure rigidity design method and application, and the method comprises the steps: firstly, carrying out the iterative optimization design of the determined rotor structure fulcrum rigidity, and determining the rigidity of each fulcrum; secondly, the static strength of the initial stator assembly and the stiffness of each fulcrum are analyzed, if the static strength and fulcrum stiffness requirements are not met, the stator assembly is optimized, and a stator assembly structure determined for the first time is obtained after optimization is completed; then, the coaxiality of all supporting points of the stator assembly determined for the first time is analyzed, if the requirement is not met, the main bearing structure is optimized, and a stator assembly structure determined again is obtained after optimization; finally, static strength and fulcrum rigidity analysis is conducted on the stator assembly determined again, if the requirements are met, the final stator assembly structure is obtained, and if not, iterative optimization is conducted. The vibration performance and the structural reliability of the whole machine can be remarkably improved, and the method is suitable for engineering design of aero-engines, gas turbines and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of complete vibration control of aircraft engines and gas turbines, and relates to the stiffness design of engine support structures. Specifically, the present invention 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 complete engine and to improve the reliability and service life of the engine. Background Art

[0002] The whole-machine vibration control technology is one of the core technologies in aircraft engine design. Its purpose is to reduce the whole-machine vibration of the engine to an acceptable level and provide guarantee for the safe and reliable operation of the aircraft. The main structural factors affecting the whole-machine vibration are the rotor stiffness and the load-bearing structure stiffness. When the rotor stiffness is determined, the load-bearing structure stiffness becomes the decisive factor affecting the vibration characteristics of the whole machine, especially the stiffness design of the main load-bearing structure, which is the main load-bearing structure of the entire rotor and plays the main supporting role. Insufficient stiffness or unreasonable distribution of the load-bearing structure will cause a large vibration response during the operation of the engine, which will affect its dynamic stability and reliability.

[0003] When the rotor of an aircraft engine is a slender structure, in order to meet the requirements of rotor dynamics, three fulcrums are usually designed to enhance the support stiffness of the rotor and increase the bending critical speed to beyond the operating speed. However, the problem that the three fulcrums of the engine with a three-point support structure are prone to is that the three fulcrums are not aligned, resulting in large vibration of the whole machine and adversely affecting the operating performance of the engine. The occurrence of the three fulcrums not being aligned is usually closely related to the stiffness design of the main load-bearing fulcrum. If the stiffness design of the main load-bearing fulcrum is unreasonable, it will cause a large difference in the deformation of the three fulcrums, resulting in large misalignment.

[0004] Large aircraft engines are usually equipped with an independent main load-bearing casing, which mainly serves as a support. It does not bear the function of aerodynamic supercharging, but mainly bears inertial loads such as vibration and overload, and has a larger structural rigidity and smaller aerodynamic load. In contrast, due to the small size and compact structure of small aircraft engines, 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, and the bearing seat of the main load-bearing fulcrum is integrated with the installation section of the compressor's last-stage stator blades and the outer ring of the stator blades as the main load-bearing structure. The pressure on one side of the main load-bearing bearing seat is the outlet pressure of the compressor's last-stage stator blades. After aerodynamic supercharging, 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, and 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-transmitting bearing seat. When the main load-bearing structure has a small deformation, the front and rear support points will both have a large deformation, resulting in an increase in the different axial degrees of the three support points.

[0005] From the perspective of engineering practice, the existing main support structure stiffness design mainly focuses on meeting the rotor dynamics requirements and the static strength design of the stator assembly, and rarely considers the impact of the three-point structural stiffness on the coaxiality of the support. In particular, after meeting the static strength requirements of the main bearing structure, the engineering design experience and theoretical research on further optimizing the support stiffness to improve the coaxiality of the three supports are still incomplete. In addition, the traditional design method does not adequately analyze the deformation characteristics of the stator assembly under complex loads, which leads to the problem of excessive vibration of the whole machine in actual application.

[0006] In summary, the existing technology has obvious defects and deficiencies in the design of the main bearing support stiffness of the three-pivot engine. On the one hand, the main bearing support stiffness design fails to fully consider the combined effects of the static strength of the stator assembly, the rotor dynamics, and the coaxiality of the support; on the other hand, the existing design method lacks systematicity and is difficult 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 the static strength and dynamic performance requirements while ensuring the coaxiality requirements of the support is a technical problem that needs to be solved in the field of engine vibration control. Summary of the invention

[0007] 1. Purpose of the invention In view of the above defects and deficiencies in the prior art, in order to solve the problems of increased whole machine vibration, insufficient static strength of stator assembly and limited rotor dynamics performance caused by different axes of fulcrums in the stiffness design of the main bearing structure of the three-pivot engine, the present invention provides a three-pivot engine compact main bearing structure stiffness design method and application for the main bearing structure stiffness design requirements of the three-pivot engine. First, by iteratively optimizing the structure of the stator assembly, the static strength and the stiffness of each fulcrum are analyzed to meet the static strength requirements and rotor dynamics requirements; second, by optimizing the iterative main bearing structure, the different axes of each fulcrum are analyzed according to the deformation of each fulcrum to meet the different axes requirements; third, by analyzing the static strength, fulcrum stiffness and different axes of the optimized stator assembly, it is ensured that the static strength, fulcrum stiffness and different axes of the fulcrum of the final structure meet the requirements. It is achieved that while meeting the strength requirements of the stator assembly and the rotor dynamics requirements, the whole machine vibration is effectively reduced, the reliability and applicability of the main bearing structure are improved, and effective guidance is provided for the design of similar structures of aircraft engines and gas turbines.

[0008] (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 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 rotor dynamics performance and the coaxiality of the fulcrum, and solve the problem of increased vibration of the whole machine caused by the non-coaxiality of the fulcrum. The method is implemented in the following steps: SS1. Establishment of finite element model for rotor dynamics analysis According to 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 among 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 of the two-order rigid body vibration mode critical speed and the bending critical speed. SS2. Optimization of support stiffness and determination of each support stiffness Based on the rotor dynamics analysis results of step SS1, the stiffness of each support point is optimized through repeated iterations, and the support point stiffness distribution is adjusted to meet the requirements of critical speed and strain energy, to ensure that the margin of the rigid body vibration mode critical speed of the rotor from the operating speed is greater than 20%, and the bending critical speed is greater than the maximum operating speed and the margin is not less than 20%, and finally determine the optimized stiffness values ​​of the compressor front support point, the main load-bearing support point, and the turbine end support point that meet the critical speed and strain energy requirements; SS3. Establish the initial finite element model for static strength analysis of stator components According to the fulcrum stiffness value optimized and determined in step SS2, a static strength analysis finite element model of a complete initial stator assembly including the main load-bearing structure is established, and by constraining the degree of freedom of the installation node position in the stator assembly, a steady-state static load and a maneuvering flight load 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 according to the deformation result of each fulcrum to determine whether the actual stiffness of each fulcrum meets the rotor dynamics design requirements; SS4. Iteratively optimize the structure of the stator assembly to meet the static strength and stiffness requirements In view of the situation in step SS3 where the static strength of the stator assembly is insufficient or the fulcrum stiffness does not meet the rotor dynamics requirements, the structure of the stator assembly is repeatedly optimized by iteration, including changing its geometric dimensions, material distribution and / or local structural design, until the stator assembly meets the requirements of the static strength design criteria and ensures that the stiffness of each fulcrum meets the rotor dynamics design requirements, thereby forming a first determined stator assembly structure scheme; SS5. First determination of the different axiality analysis of each support point in the stator assembly structure Based on the static strength analysis result of the stator assembly determined for the first time in step SS4, the deformation of the front support point of the compressor, the main load-bearing support point and the turbine end support point in the vertical direction is analyzed, and the different axiality between the support points is analyzed according to the deformation results of each support point, and it is determined whether the different axiality of the three support points is less than the preset threshold value. If the different axiality 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 it is less than the preset threshold value, the process proceeds to step SS7; SS6. Iteratively optimize the main load-bearing structure and re-determine the structure of the stator assembly In the case where the misalignment of the three fulcrums exceeds the preset threshold in step SS5, the main load-bearing structure of the stator assembly is repeatedly optimized by iteration, 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 fulcrums meets the requirement of being less than the preset threshold, and the stator assembly structure is re-determined; SS7. Verify the optimized stator assembly and determine the final structure 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 the static strength requirements and rotor dynamics design requirements are met at the same time. If not, return to step SS4 for a loop iteration. If the requirements are met, the stator assembly and its main load-bearing structure are determined as the final design scheme to ensure its high reliability and high applicability under complex load conditions.

[0009] Through the above steps, the present invention comprehensively considers the requirements of static strength of stator assembly, dynamic performance of rotor and coaxiality of fulcrum, provides a systematic main load-bearing fulcrum stiffness design method, significantly reduces the vibration of the whole machine, improves the reliability and applicability of the main load-bearing structure, and can be widely used in the optimization design of the main load-bearing structure of aircraft engines and gas turbines.

[0010] The second inventive object of the present invention is to provide a three-pivot engine compact main load-bearing structure, whose stiffness design is based on the above-mentioned three-pivot engine compact main load-bearing structure stiffness design method of the present invention.

[0011] The third inventive object of the present invention is to provide a three-pivot compact engine, including the above-mentioned three-pivot engine compact main load-bearing structure of the present invention.

[0012] (III) Technical Effect Compared with the prior art, the three-pivot engine compact main bearing structure stiffness design method and application of the present invention have the following beneficial and significant technical effects: (1) The present invention designs the stiffness of the main load-bearing structure from multiple angles in view of the various factors that cause large vibration of the whole machine. Not only the strength of the stator assembly and the stiffness of the main load-bearing structure are designed from the aspects of the static strength of the stator assembly and the rotor dynamics, but also the stiffness of the main load-bearing structure is designed from the aspects of the different axiality of the three fulcrums in order to avoid the large vibration of the whole machine caused by the different axes of the three fulcrums. The comprehensive optimization design of the static strength of the stator assembly, the rotor dynamics performance and the coaxiality of the fulcrum is achieved, and finally the main load-bearing structure that meets all design requirements is obtained, thereby significantly reducing the vibration amplitude of the whole machine and improving the dynamic stability of the system.

[0013] (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 a low probability of large vibration problems of the whole machine. 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

[0014] Figure 1 It is a schematic diagram of the structure of the stator assembly; Figure 2 A flow chart for the stiffness design of the compact main load-bearing structure of a three-pivot engine provided by the present invention; Figure 3 The schematic diagram of the preliminarily determined main load-bearing structure, where: (a) is the fourth-stage stator, (b) is the installation section; Figure 4 It is a schematic diagram of the static deformation of the stator assembly in the vertical direction; 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

[0015] 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 2 The process shown realizes the stiffness design of the compact main bearing structure of the three-pivot engine. It should be noted that the described embodiments are part of the embodiments of the present invention, not all of the embodiments, and the described embodiments are exemplary and intended to be used to explain the present invention, but cannot be understood as limiting the present invention.

[0016] In an embodiment of the present invention, Figure 2 As shown, the three-pivot engine compact main bearing structure stiffness design method mainly includes the following steps when implemented: SS1. Establishment of finite element model for rotor dynamics analysis According to 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 end support, the main load-bearing support and the turbine end support among 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 of the two-order rigid body vibration mode critical speed and the bending critical speed.

[0017] Preferably, the establishment of the finite element model for rotor dynamics analysis includes at least the definition of 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 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.

[0018] SS2. Optimization of support stiffness and determination of each support stiffness 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 meet the requirements of critical speed and strain energy. It is ensured that the margin of the rigid body vibration critical speed of the rotor from the operating speed is greater than 20%, and 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.

[0019] In this embodiment, the final stiffness of the front 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.

[0020] SS3. Establish the initial finite element model for static strength analysis of stator components 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, and 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.

[0021] Preferably, 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 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 applying steady-state static load and maneuvering flight load, is the yield strength of the material and 0.9 is the safety factor.

[0022] In this embodiment, based on the established initial static strength analysis finite element model of the stator assembly, the installation node 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, elastic ring stiffness is 8.4×10 6 N / m, after the stiffness combination, the compressor front support stiffness is 6.3×10 6 The stiffness of the compressor rear support, i.e. the main load-bearing support, is 8.6×10 7 N / m, the turbine end support stiffness is 3.7×10 6 N / m, under this stiffness, there are two-order rigid body vibration critical speeds within the working range, the margin from the working speed is greater than 20%, the bending critical is greater than the maximum speed, the margin is 30%, which meets the rotor dynamics requirements, and the corresponding stator assembly structure is the stator assembly structure determined for the first time, see Figure 3 .

[0023] SS4. Iteratively optimize the structure of the stator assembly to meet the static strength and stiffness requirements In response to the situation in step SS3 where the static strength of the stator assembly is insufficient or the fulcrum stiffness does not meet the rotor dynamics requirements, the stator assembly structure is repeatedly optimized by iterative optimization, including 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 fulcrum meets the rotor dynamics design requirements, thereby forming the first determined stator assembly structure scheme.

[0024] Preferably, iterative optimization of the stator assembly structure includes thickening the thin-wall structure of the stator assembly, reinforcing 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, while the fulcrum stiffness is improved to meet the rotor dynamics design requirements and avoid the fulcrum misalignment problem caused by excessive deformation.

[0025] In this embodiment, the deformation of each support in the vertical direction 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, i.e. 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 different axialities of the front support of the compressor and the turbine end support relative to the main load-bearing support are both greater than 0.03mm, which does not meet the support coaxiality requirement of less than 0.03mm. Analyzing the reasons, 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 node is directly integrated with the fourth-stage stator casing. The low rigidity of the casing leads to low rigidity of the mounting node.

[0026] SS5. Secondary determination of the different axiality analysis of each support point in the stator assembly structure 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 misalignment between the supports is analyzed according to the deformation results of each support to determine whether the misalignment of the three supports is less than a preset threshold. If the misalignment of the three supports exceeds 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.

[0027] 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 loads 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.

[0028] 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, and the other is to set reinforcing 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 front support of the compressor under the static load of the main load-bearing structure is 0.003mm, the vertical displacement of the rear support of the compressor, i.e. the main load-bearing support, is approximately zero, and 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.

[0029] SS6. Iteratively optimize the main load-bearing structure and re-determine the structure of the stator assembly In response to the situation in step SS5 where the misalignment of the three fulcrums exceeds the preset threshold, the main load-bearing structure of the stator assembly is iteratively optimized, 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 fulcrums meets the requirement of being less than the preset threshold, thereby obtaining a re-determined stator assembly structure.

[0030] Preferably, the iterative optimization of the main load-bearing structure includes: improving the overall stiffness of the main load-bearing fulcrum by adjusting the thickness of the load-bearing support plate, locally strengthening the thin-walled structure with reinforcing ribs to reduce deformation, optimizing the geometry of the main load-bearing fulcrum to improve load distribution, enhancing the material properties of the main load-bearing structure, and verifying the effectiveness of the optimization measures in combination with finite element analysis, until the misalignment of the three fulcrums is less than a preset threshold.

[0031] In this embodiment, after optimization, the compressor front support bearing casing stiffness is 5.4×10 7 N / m, 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, i.e. the main load-bearing support, is 1.3×10 8 N / m, 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, the margin from the working speed is greater than 20%, the bending critical is greater than the maximum speed, and the margin is 46%, which meets the rotor dynamics requirements. After calculation, the static stress of the stator assembly after optimization also meets The stator assembly structure is the final stator assembly structure.

[0032] SS7. Verify the optimized stator assembly and determine the final structure 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 the static strength requirements and rotor dynamics design requirements are met at the same time. If not, return to step SS4 for a loop iteration. If the requirements are met, the stator assembly and its main load-bearing structure are determined as the final design scheme to ensure its high reliability and high applicability under complex load conditions.

[0033] As a preference, the final verification of the stator assembly structure includes a comprehensive evaluation 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.

[0034] In summary, the present invention clarifies the stiffness design method of the compact main bearing structure of the three-pivot engine. The stiffness design of the main bearing fulcrum is not only designed from the static strength and rotor dynamics of the stator assembly, but also from the coaxiality of the three fulcrums, thereby reducing the probability of vibration problems of the whole machine. In addition, the design method is highly feasible in engineering practice and can directly guide the engineering design of similar structures of aircraft engines and gas turbines.

[0035] 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 designing the stiffness of a compact main bearing structure of a three-pivot engine, characterized in that: The design method comprises at least the following steps when implemented: SS1. According to 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 of the two-order rigid body vibration mode critical speed and the bending critical speed; SS2. 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 requirements of critical speed and strain energy, ensuring that the margin of the rigid body vibration mode critical speed of the rotor from the operating speed is greater than 20%, and the bending critical speed is greater than the maximum operating speed with a margin of not less than 20%, and finally determine the optimized stiffness values ​​of the compressor front support point, main load-bearing support point and turbine end support point that meet the critical speed and strain energy requirements; SS3. 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, and by constraining the degrees of freedom of the installation node position in the stator assembly, a steady-state static load and a maneuvering flight load 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, the actual stiffness value of each fulcrum is calculated according to the deformation results of each fulcrum to determine whether the stiffness of each fulcrum meets the rotor dynamics design requirements; SS4. In case the static strength of the stator assembly is insufficient or the fulcrum stiffness does not meet the rotor dynamics requirements in step SS3, the structure of the stator assembly is optimized repeatedly, including 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 fulcrum meets the rotor dynamics design requirements, thus forming the first determined stator assembly structure scheme; SS5. 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 point, the main load-bearing support point and the turbine end support point in the vertical direction is analyzed, and the different axiality between the support points is analyzed according to the deformation results of each support point, and it is determined whether the different axiality of the three support points is less than the preset threshold value. If the different axiality 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 it is less than the preset threshold value, the process proceeds to step SS7; SS6. In case the misalignment of the three fulcrums exceeds the preset threshold in step SS5, the main load-bearing structure of the stator assembly is optimized repeatedly and iteratively, including adjusting the thickness of the load-bearing support plate, changing the structure shape and / or adding reinforcing ribs at key positions, so as to increase the stiffness of the main load-bearing structure and reduce its deformation under load, until the misalignment meets the requirement of being less than the preset threshold, and the stator assembly structure is re-determined; SS7. For the stator assembly structure re-determined in step SS6, the static strength and support stiffness of the stator assembly re-determined are analyzed using the static strength finite element model to verify whether both the static strength requirements and the rotor dynamics design requirements are met. If not, return to step SS4 for a loop iteration. If the requirements are met, the stator assembly and its main load-bearing structure are determined as the final design solution.

2. The method for designing the rigidity 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 at least includes the definition of geometric parameters, material properties, boundary conditions and load conditions of the rotor structure. The boundary conditions are set by simulating the constraint forms 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 operating range of the engine.

3. The method for designing the rigidity 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 aerodynamic loads, inertial loads and installation loads under steady-state static loads. The maneuvering flight loads include overloads 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 it is judged whether the stator assembly meets the static strength design criteria by the static stress distribution.

4. The method for designing the rigidity 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 the 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 applying steady-state static load and maneuvering flight load, σ 0.2 is the yield strength of the material and 0.9 is the safety factor.

5. The method for designing the rigidity 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 rigidity 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 front support of the compressor, 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 loads 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.

7. The method for designing the rigidity 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 fulcrum 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 fulcrum 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 fulcrum misalignment is less than a preset threshold.

8. The method for designing the rigidity 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, where 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: The stiffness design thereof is based on the stiffness design method of the 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 compact main load-bearing structure of the three-pivot engine as described in claim 9.

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