Structural design method of short-span membrane disc coupling in gas turbine

Abstract

The invention belongs to the field of aero-engine calculation, and particularly relates to a structural design method of a short-span membrane disc coupling in a gas turbine, which comprises the following steps: determining an axial span L and a mounting edge radial height R according to a coupling mounting environment; the material of the coupler is determined by eliminating the thermal deformation discordance of the coupler and the connected transmission shaft; the inner diameter R1 and the outer diameter R2 of the intermediate shaft are determined according to the bearing torque T of the coupler; and S4, a parameterized geometric model of the coupler is established, the parameterized geometric model comprises a load torque T and a given installation side radial non-concentric quantity 2 delta, the parameterized geometric model is optimized to determine the minimum L1 and the maximum L2 of a coupler diaphragm disc, and the step aims at rapidly determining the configuration, and optimization is carried out after the simplified model and the simplified load are adopted.

Description

Technical Field

[0001] The present application belongs to the field of aero-engine calculation, and in particular relates to a structural design method for a short-span diaphragm coupling inside a gas turbine. Background Art

[0002] The diaphragm coupling is an all-metal flexible structure that transmits torque and compensates for various deformations between the two shafts through an elastic element, the diaphragm, and is suitable for the connection of high-speed rotating shaft components. With the development of the power output function requirements of gas turbine engines, a gas turbine scheme with simultaneous front and rear outputs of the power turbine has emerged. However, the gas turbine in this scheme has a fulcrum span that is too long, and the rigid connection elements between the front and rear output shafts cannot meet the requirements of the rotor dynamic characteristics. There is also a need for radial non-concentric deformation coordination during the installation process. Therefore, it is necessary to design a flexible diaphragm coupling inside the gas turbine. The present invention relates to the field of gas turbine engine structural design, and in particular to the design of dimensional parameters of diaphragm couplings under actual working conditions.

[0003] Tonghua Normal University. An ultra-high-speed diaphragm coupling: CN202010272783.4[P].

[0004] 2020-04-09. This patent provides a structure of an ultra-high-speed diaphragm coupling, which can realize the radial non-concentric deformation compensation of two high-speed (100,000 rpm) main shafts under general external connection environment. However, this structural scheme does not take into account the influence of working environment such as high temperature inside the gas turbine and centrifugal force of high-speed turbine rotor. The axial span of the coupling installation side is large, which is not suitable for the compact and narrow actual installation environment between the front and rear output shafts of the gas turbine power turbine.

[0005] Northeastern University. A design method for a perforated diaphragm coupling: CN201911151702.9[P].2019-11-12. This patent provides a design method for a diaphragm coupling with only two perforated diaphragm structures, which can achieve radial non-concentric deformation compensation of two main shafts under general external connection environments, and has the characteristics of easy processing, light weight, and the ability to transmit large torque. However, this structural scheme does not take into account the influence of working environments such as high temperature inside the gas turbine and centrifugal force of the high-speed turbine rotor. The axial span of the coupling installation side is large and the perforated structure may cause stress concentration inside the gas turbine. It is not suitable for the compact and narrow actual installation environment between the front and rear output shafts of the gas turbine power turbine and the design requirements of long life and high reliability.

[0006] The prior art solutions related to the present invention are as described in the first section above, and have the following disadvantages:

[0007] 1) The diaphragm coupling of the existing technical solution is suitable for low temperature and space-unrestricted environments such as the outside of the gas turbine, but does not take into account the working environment influences such as the high temperature inside the gas turbine and the centrifugal force of the high-speed turbine rotor and the bearing load design requirements.

[0008] 2) The existing diaphragm coupling structure has a long span and is not suitable for the compact and narrow actual installation environment inside the gas turbine.

[0009] 3) The existing technical solutions do not provide a feasible design process and a method for determining key dimensional parameters according to the use requirements of gas turbines. Summary of the invention

[0010] In order to solve the above problems, the present application provides a structural design method for a short-span diaphragm coupling inside a gas turbine, characterized in that the coupling comprises an intermediate shaft and diaphragms of a cone wall structure located at both end surfaces of the intermediate shaft, and the diaphragms at both ends are respectively connected to the transmission shaft through mounting edges;

[0011] The design method comprises:

[0012] Step S1: Determine the axial span L and the radial height R of the installation edge according to the coupling installation environment;

[0013] Step S2: Determine the material of the coupling to eliminate the thermal deformation incompatibility between the coupling and the connected transmission shaft;

[0014] Step S3: determining the inner diameter R1 and the outer diameter R2 of the intermediate shaft according to the torque T borne by the coupling;

[0015] Step S4: Establish a parametric geometric model of the coupling, the parametric geometric model includes the load torque T and the given radial non-concentricity 2δ of the mounting edge, and optimize the parametric geometric model to determine the minimum L1 and the maximum L2 of the coupling diaphragm. The purpose of this step is to quickly determine the configuration, using a simplified model and a simplified load;

[0016] The optimization goal is: Min Fr = f(L1, L2);

[0017] The constraint condition is: n1 = σ b / σ 稳态 ≥x1, n2=σ -1 / σ 交变 ≥x2;

[0018] Where:

[0019] Fr is the fulcrum reaction force generated by compensating for radial misalignment of the mounting edge;

[0020] σ b is the ultimate tensile strength of the material;

[0021] σ 稳态 It is the maximum equivalent stress of the coupling under the action of torque load T only;

[0022] x1 is the steady-state stress safety factor, which needs to take into account the design requirements and leave a certain margin. It is recommended to be ≥3; σ -1 is the fatigue limit strength of the material under symmetrical cycles;

[0023] σ 交变 is the maximum equivalent stress of the coupling acting only on the given radial non-concentricity 2δ of the mounting side; x2 is the safety factor of the alternating stress, which needs to take into account the design requirements and leave a certain margin, and it is recommended to be ≥3; the optimization results determine the optimal dimensions of L1 and L2, and the sensitivity of their parameter changes to stress and bearing load;

[0024] Step S5: Perform strength check on the optimized parameterized geometric model, and output the final size after the strength check is qualified.

[0025] Preferably, the coupling is made of the same material as the connected transmission shaft or a material having the same expansion coefficient as the connected transmission shaft line.

[0026] Preferably, the thickness of the mounting edge of the coupling is not greater than the thickness of the mounting edge of the connecting shaft.

[0027] Preferably, the strength check includes:

[0028] Step S51: establishing a complete model of the transmission shaft, the turbine rotor and the coupling;

[0029] Step S52: obtaining a given maximum torque T, a given maximum speed N, applying the non-concentricity δ of step 4 at the coupling installation side position, and applying the deflection α1 of shaft 1 and the deflection α2 of shaft 2 at two bearing positions at the coupling installation side respectively;

[0030] It should be noted that the misalignment δ applied to the coupling mounting edge in the previous text should actually be applied to the support bearing near the mounting edge. Since the influence of the mounting edges of axis 1 and axis 2 was not considered, the δ applied directly to the mounting edge was too large.

[0031] In addition, due to the tilt and sway of the gas turbine with the ship in the wind and wave environment, the coupling and shaft 1 and shaft 2 will be relatively deflected. The deflection amounts α1 and α2 are calculated based on the worst combination of the misalignment of the bearing hole centers of shaft 1 and shaft 2. In the initial design, a simplified model and simplified loads are used to quickly determine the structural parameters, and only the misalignment δ is considered. A higher reserve of ≥3 is reserved to offset the influence of the deflection amounts α1 and α2, and there is a certain error in the calculation result itself.

[0032] Step S53: calculating the steady-state stress generated by the complete model under the torque T and the maximum speed N, that is, the centrifugal force load;

[0033] Step S54: calculating the alternating stress generated by the radial misalignment δ and the deflection amounts α1 and α2;

[0034] Step S55: Calculate the fatigue strength of the coupling and the bearing load according to the steady-state stress and the alternating stress to see whether they meet the index requirements. It should be noted that in the strength design of gas turbines, it is generally believed that a fatigue strength reserve ≥ 1.4 meets the fatigue strength design requirements.

[0035] Preferably, after step S5, there is a step S6:

[0036] When the bearing load does not meet the index requirements, the given radial non-concentricity 2δ of the mounting edge in step S4 is modified to the actual non-concentricity δ in step S52 and the mounting edge deflection α1 and α2 calculated according to the influence of the gyroscopic moment, and the process returns to step S4;

[0037] When the fatigue strength does not meet the index requirements: adjust the calculated load of step S4, where the steady-state load requires additional radial force to be applied to the mounting edge connected to shaft 2 to simulate the influence of centrifugal force, and the alternating load is changed to the radial non-concentricity δ and deflection α1, α2 of the mounting edge actually applied in step S52. It should be noted that according to the stress only at the maximum speed N in step S5, that is, the stress generated by the centrifugal load, the maximum radial stress m of the mounting edge of the coupling is extracted from the calculation result, and the maximum radial stress n of the mounting edge of the coupling is calculated by applying any radial force F0 on the mounting edge, then the equivalent radial Fr = F0 / n*m.

[0038] The general idea is to simplify the model into a single coupling model in the initial optimization, simplify the load and amplify the rigorous test to quickly determine the parameters; if the optimization cannot be continued, consider the real load, that is, the actual eccentricity δ1 and the deflection β1 and β2 for detailed analysis.

[0039] Preferably, after step S6, there is a step S7:

[0040] When the index requirements are met, the final size and processing technology are determined, the drawings are completed and put into production, and the minimum L1 of the coupling diaphragm is inspected by fluorescent flaw detection before use.

[0041] Advantages of this application include:

[0042] 1) The specific requirements for the design space, operating environment, load and other inputs required for the structural design of the short-span diaphragm coupling inside the gas turbine are clarified to guide the rapid determination of design requirements during the scheme design stage.

[0043] 2) Provide a short-span diaphragm coupling structure solution inside a gas turbine, which can be suitable for the compact and narrow actual installation environment inside the gas turbine. Provide an optional solution for the situation where the rotor dynamic characteristics of the gas turbine power turbine front and rear simultaneous output scheme do not meet the requirements. At the same time, it can provide displacement compensation to solve the problem of eccentricity between the front and rear output shafts of the power turbine, avoiding the risk of excessive rigid coupling stress and bearing load.

[0044] 3) Provide a structural design process and a method for determining key dimensional parameters of a short-span diaphragm coupling for a gas turbine, which can meet the use requirements between the front and rear output shafts of the power turbine inside the gas turbine and avoid the risk of damage caused by excessive coupling stress or excessive bearing load due to improper coupling parameter design.

[0045] 4) Provide guidance on the design of test plans for gas turbine components, such as the selection of load parameters.

[0046] 5) Promote the rapid integrated design of gas turbine structural strength, reduce the existing iterative processes of the two disciplines of "structure-strength", improve the efficiency of structural design, and further improve the engine R&D system. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a flow chart of a structural design method for a short-span diaphragm coupling inside a gas turbine of the present application; FIG.

[0048] Figure 2 It is a schematic diagram of the structure scheme and installation environment of the short-span diaphragm coupling inside the gas turbine;

[0049] Figure 3 It is a schematic diagram of the radial misalignment δ of the coupling installation side;

[0050] Figure 4 It is a schematic diagram of the coupling mounting side deflection α (including axis 1 and axis 2). DETAILED DESCRIPTION

[0051] In order to make the technical solution and advantages of the present application clearer, the technical solution of the present application will be further described in detail in detail and in detail in conjunction with the accompanying drawings. It can be understood that the specific embodiments described here are only partial embodiments of the present application, which are only used to explain the present application, not to limit the present application. It should be noted that, for the convenience of description, only the parts related to the present application are shown in the accompanying drawings, and other related parts can refer to the general design. In the absence of conflict, the embodiments in the present application and the technical features in the embodiments can be combined with each other to obtain new embodiments.

[0052] like Figure 1 As shown in the figure, the design method of the short span diaphragm coupling structure inside the gas turbine requires the following preparations:

[0053] Determine the design inputs for the coupling structure

[0054] The existing technical solutions do not provide detailed descriptions of specific inputs such as the design space, operating environment, and load inside the gas turbine. To carry out the structural design of the short-span diaphragm coupling inside the gas turbine, the following parameters need to be prepared:

[0055] a. Installation side interface dimensions

[0056] Used to determine the design space of the coupling, such as Figure 2 As shown, the axial span L and the radial height R of the mounting edge can be regarded as forming a cylinder. This scheme is suitable for structural design in the compact space inside the gas turbine, with the minimum dimension of L ≯100mm and the minimum dimension of R ≯200mm.

[0057] b. Connection location model

[0058] Used for detailed strength check of couplings, such as Figure 2 As shown, it mainly includes the 2D model of the two main shafts connected to the coupling and the turbine rotor, and also includes the relative positions of the bearings.

[0059] c. Working environment

[0060] To determine the material selection, structural design and detailed strength verification of the coupling, the operating ambient temperature and maximum speed N of the coupling are required.

[0061] Due to the influence of the rotational inertia of the power turbine rotor, this scheme needs to consider the influence of the centrifugal force caused by the rotation speed; however, the centrifugal force can be strengthened by Figure 2 The journal stiffness is limited to a smaller range. To ensure rapid determination of the structural dimension scheme, this load is only considered during detailed strength verification.

[0062] d. Load

[0063] It is used to determine the structural design of the coupling and the detailed strength verification of the coupling. It is necessary to provide the maximum torque T of the coupling and the radial non-concentricity δ and deflection α of the two mounting sides of the coupling (see Figure 3-Figure 4 , calculated based on the gyroscopic moment M).

[0064] The radial misalignment δ compensation requirement for gas turbine design is relatively low (generally ≯0.5mm), but it is necessary to consider the maximum value under the influence of the position deviation of the bearing seat axis and the bearing clearance combination caused by factors such as design tolerance and assembly control.

[0065] The deflection of the installation side α is mainly due to the gyroscopic moment M generated by the gas turbine swing load. Figure 2The axial direction of the middle shaft 2 and the connected mounting edge are deformed. Figure 2 The journal stiffness is limited to a smaller range. To ensure rapid determination of the structural dimension scheme, this load is only considered during detailed strength verification.

[0066] It should be noted that the coupling designed in this scheme is located between the shafts of the front and rear output schemes of the gas turbine power turbine, has no axial displacement compensation requirements, and is hardly subjected to axial force.

[0067] e. Design requirements

[0068] The standard used to judge whether the coupling structure parameters are reasonable. The design requirements of the coupling can be divided into (fatigue) strength requirements and bearing load requirements.

[0069] The strength requirement needs to meet the coupling's infinite life under steady-state load at maximum torque T and maximum speed N (centrifugal force) and alternating loads caused by the worst radial misalignment δ and deflection α of the coupling's mounting side.

[0070] The bearing load requirement is due to the compensation of the radial non-concentricity δ and deflection α of the coupling mounting edge. Figure 2 The radial reaction force Fr (generally not ≯10000N) generated by the middle bearing 1 and the bearing 2 is calculated based on the actual allowable load capacity of the bearing minus the load capacity requirement of the gas turbine rotor under maneuvering conditions.

[0071] Step 1: Determine the initial coupling structure plan

[0072] The existing coupling diaphragm has a long span, which is not suitable for the compact and narrow installation environment inside the gas turbine. Figure 2 The short-span U-type diaphragm coupling shown in the figure mainly compensates for the radial non-concentricity δ and deflection α of the mounting edge through two diaphragms. It has a simple structure and a small span L (≯100mm), and can be applied to the compact and narrow actual installation environment inside the gas turbine.

[0073] In addition to the diaphragm, the coupling can also be divided into two parts during the design process: the mounting edge and the bottom edge. The diaphragm adopts a conical wall structure, which helps to reduce the stress level at the connection between the diaphragm and the bottom edge. The connection between the diaphragm and the mounting edge and bottom edge adopts a large fillet transition (5 to 10, between the thickness of the diaphragm and the thickness of the mounting edge / bottom edge) to minimize the impact of stress concentration.

[0074] Step 2: Determine the material selection for the coupling

[0075] The material selection of the existing technical scheme does not consider the impact of the high temperature environment of the gas turbine. This technical scheme can take into account the actual working problems of the gas turbine (the highest temperature exceeds 300℃, and the local temperature is approximately uniform), and the material selection process is determined as follows:

[0076] Prioritize and Figure 2 The materials of the middle axis 1 and axis 2 and the main axis are generally made of high-temperature alloy and stainless steel. The advantage of this solution is that it can eliminate the influence of thermal deformation incompatibility caused by different materials, and the material strength is high, but the disadvantage is that the elastic modulus is high (about 200GPa), and the ability to compensate for the radial non-concentricity δ and deflection α of the thermal installation edge is relatively poor.

[0077] If this solution is not feasible, select a material with the same linear expansion coefficient for axis 1 and axis 2, and select a material with a lower elastic modulus and higher strength according to actual conditions.

[0078] Step 3: Determine the coupling bottom edge dimensions R1, R2 and installation edge dimensions

[0079] The existing technical solution does not provide a detailed description of the determination of the specific size parameters of the coupling. The design process of the coupling bottom edge dimensions R1, R2 and the installation edge dimension parameters introduced in this technical solution is as follows:

[0080] Since the bottom edge has a low radial height, it mainly bears the shear stress generated by the torque T. The design should ensure the ultimate tensile strength σ of the material. b The ratio of the torsional section coefficient W of the most dangerous section shall not be less than Figure 2 The lowest value of the straight section of the middle axis 1 or axis 2. The torsional section coefficient is calculated by the formula W = π*

[0081] (R2 4 -R1 4 ) / (2*R2). In general, for the convenience of design, when the coupling material is consistent with the connected main shaft material, R1 and R2 can be consistent with the size of the dangerous section of the straight section of shaft 1 or shaft 2.

[0082] The mounting edge is less affected by various loads and the actual stress level is low. In general, the mounting edge structure of axis 1 and axis 2 can be used. Figure 2 As shown, due to the low thickness L1 of the diaphragm disk, the thickness of the mounting edge cannot be too large (try not to exceed the thickness of the mounting edge of axis 1 or axis 2), which will cause high local stress at the position of the diaphragm disk L1 due to drastic changes in local stiffness.

[0083] Step 4: Determine the thickness dimensions L1 and L2 of the coupling diaphragm. The prior art solution does not provide a detailed description of the determination of the specific dimension parameters of the coupling. The design process of the dimension parameters of the coupling diaphragm thickness dimensions L1 and L2 introduced in this technical solution is as follows:

[0084] a. Simplified finite element analysis model

[0085] Due to the complex load environment of the coupling and the strength calculation results are subject to Figure 2 Due to the influence of the stiffness of shaft 1, shaft 2 and turbine rotor, it is difficult to directly carry out parameter optimization. Therefore, considering its structure and load characteristics, minor factors are ignored and a simplified model is established.

[0086] The simplified model does not consider the influence of axis 1, axis 2 and turbine rotor stiffness, but only considers Figure 2 Middle membrane disc coupling.

[0087] The simplified model load ignores the secondary load centrifugal force (generated by the rotational speed N) and the mounting side deflection α, and only considers the main load torque T and the radial non-concentricity δ of the mounting side, and amplifies them according to design experience to compensate for the influence of other loads (the main mounting side radial non-concentricity δ is recommended to be considered as 2 times).

[0088] b. Establish parametric geometric model

[0089] Figure 2 The coupling structure shown is a symmetrical structure. A parametric model of the coupling diaphragm thickness dimensions L1 and L2 is established. For the convenience of processing, it is recommended that the inner side of the diaphragm cone wall be set as a straight surface and the outer side be set as an inclined surface.

[0090] The lower limit of L1 and L2 size parameters is recommended to be ≮1mm, and the upper limit is recommended to be ≯ the thickness of the installation edge.

[0091] c. Perform parameter optimization to obtain specific values ​​of L1 and L2 sizes and establish a parameter optimization model as follows.

[0092] Min Fr=f(L1, L2)

[0093] stn1=σ b / σ 稳态 ≥x1

[0094] n2=σ -1 / σ 交变 ≥x2

[0095] Where:

[0096] Fr is the fulcrum reaction force generated by compensating for radial misalignment of the mounting edge;

[0097] σ b is the ultimate tensile strength of the material;

[0098] σ 稳态 It is the maximum equivalent stress of the coupling under the action of torque load T only;

[0099] x1 is the steady-state stress safety factor, which needs to take into account the design requirements and leave a certain margin. It is generally recommended to be ≥3;

[0100] σ -1 is the fatigue limit strength of the material under symmetrical cycles;

[0101] σ 交变 It is the maximum equivalent stress of the coupling acting only on the radial misalignment δ of the mounting side.

[0102] x2 is the alternating stress safety factor, which needs to take into account the design requirements and leave a certain margin. It is generally recommended to be ≥3.

[0103] The optimization results can determine the optimal dimensions of L1 and L2, as well as the sensitivity of their parameter changes to stress and bearing load.

[0104] Step 5: Perform detailed strength check on the initially optimized coupling model

[0105] In order to quickly determine the structural parameters of the diaphragm coupling, the optimization process was simplified. In order to ensure that the optimization model can meet the design requirements in the actual working environment of the gas turbine, it is necessary to perform a detailed strength check on the initial structure formed after optimization.

[0106] Compared with step 4, the model needs to consider the influence of shaft 1, shaft 2 and turbine rotor stiffness (establish a complete model), as well as the load centrifugal force (generated by the rotational speed N) and the mounting edge deflection α (calculated based on the deformation of the gyroscopic moment condition, with the inclination angles of the mounting edges of shaft 1 and shaft 2 being α1 and α2 respectively).

[0107] During strength verification, the stress generated by torque T and centrifugal force is taken as steady-state stress, and the stress generated by radial misalignment δ and deflection α of the two mounting edges is taken as alternating stress. The fatigue strength of the coupling and the bearing load are calculated to see whether they meet the design requirements of the gas turbine.

[0108] Step 6: Decide whether to further optimize based on the detailed strength verification results

[0109] If step 5 proves that the initial optimization results meet the design requirements, this step is not required and step 7 can be performed directly.

[0110] If step 5 proves that the initial optimization results do not meet the design requirements, then execute this step. According to the situation where the indicators are not met, the optimization model adjustment measures are formulated for further optimization:

[0111] a. If the bearing load does not meet the index requirements

[0112] This situation rarely occurs. Generally, the bearing load calculated by the simplified model is too large because it does not take into account Figure 2The deformation of the journal position can compensate for a certain proportion of the radial misalignment δ. The main reason for this is that the deflection angle α of the mounting edge caused by the gyroscopic moment is large, and the alternating stress calculation load in step 4 needs to be adjusted, that is, it is changed to the radial misalignment δ1 and deflection α1, α2 of the mounting edge actually applied in step 5.

[0113] b. If the fatigue strength does not meet the index requirements

[0114] The reason for this situation is generally that the centrifugal load (speed N) has a large influence or the installation edge deflection angle α1, α2 (caused by the gyroscopic moment) is large. The calculated load in step 5 needs to be adjusted, where the steady-state load needs to apply an equivalent radial force to the installation edge connected to shaft 2 to simulate the influence of centrifugal force, and the alternating load is changed to the radial non-concentricity δ and deflection α1, α2 of the installation edge actually applied in step 6.

[0115] Step 7: Output

[0116] According to the final structural size optimization design results, the transfer position connection is refined, large rounded corners are used for smooth transition, and the final size and processing technology are determined by the manufacturer to complete the drawing and put into production. It should be noted that generally Figure 2 The size of L1 is relatively small (maybe ≯1.5mm). To ensure product quality, fluorescent flaw detection should be added before use.

[0117] Advantages of this application include:

[0118] 1) The specific requirements for the design space, operating environment, load and other inputs required for the structural design of the short-span diaphragm coupling inside the gas turbine are clarified to guide the rapid determination of design requirements during the scheme design stage.

[0119] 2) Provide a short-span diaphragm coupling structure solution inside a gas turbine, which can be suitable for the compact and narrow actual installation environment inside the gas turbine. Provide an optional solution for the situation where the rotor dynamic characteristics of the gas turbine power turbine front and rear simultaneous output scheme do not meet the requirements. At the same time, it can provide displacement compensation to solve the problem of eccentricity between the front and rear output shafts of the power turbine, avoiding the risk of excessive rigid coupling stress and bearing load.

[0120] 3) Provide a structural design process and a method for determining key dimensional parameters of a short-span diaphragm coupling for a gas turbine, which can meet the use requirements between the front and rear output shafts of the power turbine inside the gas turbine and avoid the risk of damage caused by excessive coupling stress or excessive bearing load due to improper coupling parameter design.

[0121] 4) Provide guidance on the design of test plans for gas turbine components, such as the selection of load parameters.

[0122] 5) Promote the rapid integrated design of gas turbine structural strength, reduce the existing iterative processes of the two disciplines of "structure-strength", improve the efficiency of structural design, and further improve the engine R&D system.

[0123] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A structural design method for a short-span diaphragm coupling inside a gas turbine, characterized in that: The coupling comprises an intermediate shaft and a diaphragm disk with a cone wall structure located at both end surfaces of the intermediate shaft, and the diaphragm disks at both ends are respectively connected to the transmission shaft through mounting edges; The design method comprises: Step S1: Determine the axial span L and the radial height R of the installation edge according to the coupling installation environment; Step S2: Determine the material of the coupling to eliminate the thermal deformation incompatibility between the coupling and the connected transmission shaft; Step S3: determining the inner diameter R1 and the outer diameter R2 of the intermediate shaft according to the torque T borne by the coupling; Step S4: establishing a parameterized geometric model of the coupling, the parameterized geometric model including the load torque T and a given radial non-concentricity 2δ of the mounting edge, and optimizing the parameterized geometric model to determine the minimum L1 and the maximum L2 of the coupling diaphragm; The optimization goal is: Min Fr = f(L1, L2); The constraint condition is: n1 = σ b / σ 稳态 ≥x1, n2=σ -1 / σ 交变 ≥x2; Where: Fr is the fulcrum reaction force generated by compensating for radial misalignment of the mounting edge; σ b is the ultimate tensile strength of the material; σ 稳态 It is the maximum equivalent stress of the coupling under the action of torque load T only; x1 is the steady-state stress safety factor, which needs to take into account the design requirements and leave a certain margin, and is recommended to be ≥3; σ -1 is the fatigue limit strength of the material under symmetrical cycles; σ 交变 is the maximum equivalent stress of the coupling acting only on the given radial non-concentricity 2δ of the mounting side; x2 is the safety factor of the alternating stress, which needs to take into account the design requirements and leave a certain margin, and it is recommended to be ≥3; the optimization results determine the optimal dimensions of L1 and L2, and the sensitivity of their parameter changes to stress and bearing load; Step S5: Perform strength check on the optimized parameterized geometric model, and output the final size after the strength check is qualified.

2. The structural design method of the short span diaphragm coupling inside the gas turbine according to claim 1, characterized in that: The coupling is made of the same material as the connected transmission shaft or of a material having the same expansion coefficient as the connected transmission shaft line.

3. The structural design method of the short-span diaphragm coupling inside a gas turbine according to claim 1, characterized in that: The thickness of the mounting edge of the coupling is not greater than the thickness of the mounting edge of the connecting shaft.

4. The structural design method of the short-span diaphragm coupling inside a gas turbine according to claim 1, characterized in that: Strength checks include: Step S51: establishing a complete model of the transmission shaft, the turbine rotor and the coupling; Step S52: obtaining a given maximum torque T, a given maximum speed N, applying the non-concentricity δ of step 4 at the coupling installation side position, and applying the deflection α1 of shaft 1 and the deflection α2 of shaft 2 at the two bearing positions at the coupling installation side; Step S53: calculating the steady-state stress generated by the complete model under the torque T and the maximum speed N; Step S54: calculating the alternating stress generated by the radial misalignment δ and the deflection amounts α1 and α2; Step S55: Calculate the fatigue strength of the coupling and the bearing load to see whether they meet the index requirements according to the steady-state stress and the alternating stress.

5. The structural design method of the short-span diaphragm coupling inside a gas turbine according to claim 4, characterized in that: After step S5, there is step S6: When the bearing load does not meet the index requirements, the given radial non-concentricity 2δ of the mounting edge in step S4 is modified to the actual non-concentricity δ in step S52 and the mounting edge deflection α1 and α2 calculated according to the influence of the gyroscopic moment, and the process returns to step S4; When the fatigue strength does not meet the index requirements: adjust the calculated load in step S4, where the steady-state load requires an additional radial force to be applied to the mounting edge connected to shaft 2 to simulate the influence of centrifugal force, and the alternating load is changed to the radial eccentricity δ and deflection α1, α2 of the mounting edge actually applied in step S52.

6. The structural design method of the short-span diaphragm coupling inside a gas turbine according to claim 5, characterized in that: After step S6, there is step S7: When the index requirements are met, the final size and processing technology are determined, the drawings are completed and put into production, and the minimum L1 of the coupling diaphragm is inspected by fluorescent flaw detection before use.

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