Water-turbine generator set top cover fastening bolt safety assessment method and equipment

Abstract

The invention belongs to the field of water-turbine generators, and particularly relates to a water-turbine generator set top cover fastening bolt safety assessment method and equipment, and the method comprises the steps: calculating a top cover fastening bolt under a normal operation condition and a load shedding condition through an empirical formula method and a finite element method, comparing the obtained stress values, and determining the safety of the top cover fastening bolt under the same condition. When the calculation deviation value is not larger than 10%, it is determined that the finite element calculation value of the top cover engagement bolt is correct, parameters obtained through calculation of the two calculation methods are evaluated, and it is determined that the top cover engagement bolt meets the safety use requirement on the premise that the two calculation methods both meet the evaluation standard. The method is of great significance to the accuracy of the strength checking and model selection calculation work of the top cover bolt of the water-turbine generator set, and the problem of stable operation of the set caused by the strength and model selection problem of the top cover bolt can be effectively prevented.

Description

Technical Field

[0001] The invention belongs to the field of hydro-generators, and in particular relates to a method and equipment for evaluating the safety of a top cover bolt of a hydro-generator set. Background Art

[0002] The top cover bolts are important components that connect the top cover and the seat ring. If the top cover bolts are loose or broken, the top cover will be greatly deformed or even damaged under the action of water pressure, which will cause great harm to the turbine and the hydropower plant, causing severe vibration of the unit and even leading to serious accidents such as flooding of the plant. In actual hydropower station projects, the operating environment of the turbine is complex, and its structure is subjected to various alternating cyclic loads for a long time. Therefore, there is a high possibility that the connecting bolts will be damaged. In order to ensure the safety and reliability of the turbine top cover connecting bolts, it is necessary to combine the empirical formula numerical calculation method and the finite element analysis method to carry out strength verification and selection calculation.

[0003] Although mechanical design manuals have given empirical formulas for bolt selection, these formulas are reasonable and effective, but they require clear input of various bolt loads, which are usually difficult to determine using theoretical calculations or empirical estimation methods. While finite element analysis can handle bolt-connected structures, bolt connections in finite element analysis are usually greatly simplified, resulting in inaccurate bolt stress results that cannot be used as a basis for bolt verification and selection.

[0004] In summary, both the traditional empirical formula selection and the finite element analysis have certain defects and cannot accurately determine whether the top cover bolts meet the safety requirements, causing harm to the turbine and the hydropower station plant. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method and device for evaluating the safety of the top cover bolts of a hydro-turbine generator set, which can accurately determine whether the safety of the top cover bolts meets the use requirements.

[0006] The content of the present invention includes:

[0007] A method for assessing the safety of a top cover bolt of a hydro-turbine generator set comprises:

[0008] Obtain the initial design parameters of the top cover handle bolts;

[0009] According to the initial design parameters of the top cover bolt, the top cover bolts under normal operating conditions and load rejection conditions are numerically calculated using empirical formulas to obtain a first stress value σ1 generated by the working load under normal operating conditions and a second stress value σ2 generated by the working load under load rejection conditions;

[0010] According to the initial design parameters of the top cover bolt, finite element calculations are performed on the top cover bolt under normal operating conditions and load rejection conditions under preload conditions to obtain the first comprehensive average stress value of the middle section of the top cover bolt. and the second comprehensive mean stress value

[0011] Compare the first stress value σ1 and the first comprehensive average stress value under normal operating conditions The first deviation value and the second stress value σ2 and the second comprehensive average stress value under the load rejection condition are compared. If both the first deviation value and the second deviation value are less than 10%, it is determined that the finite element calculation is correct, otherwise the finite element calculation is performed again;

[0012] According to the initial design parameters of the top cover bolt, a finite element calculation is performed on the top cover bolt without considering the preload state under normal operating conditions to obtain the third comprehensive average stress value of the middle section of the top cover bolt.

[0013] According to the initial design parameters of the top cover bolt, finite element calculation is performed on the top cover bolt in the normal operation condition and the load rejection condition, considering the pre-tightening state, to obtain the comprehensive local maximum stress value δ1 of the first bolt and the comprehensive local maximum stress value δ2 of the second bolt;

[0014] When the finite element calculation is correct, if the first comprehensive average stress value and the second integrated mean stress value are all less than the first stress standard value and the third comprehensive average stress value If the value of the comprehensive average stress is less than the standard value, the comprehensive local maximum stress value δ1 of the first bolt and the comprehensive local maximum stress value δ2 of the second bolt are both less than the standard value of the comprehensive local maximum stress of the bolt, and the ratio ρ1 of the bolt preload to the working load is greater than the standard ratio, it is determined that the top cover bolt calculated by the finite element method meets the safety requirements. Otherwise, it is determined that the top cover bolt calculated by the finite element method does not meet the safety requirements, and the first stress standard value is 4σ s / 5, the standard value of comprehensive average stress is min(σ s / 3,σ b / 5), the standard value of the comprehensive local maximum stress of the bolt is min(σ s / 3,σ b / 5), the standard ratio is 2, where σ s is the yield limit value of the bolt material, σ b is the strength limit value of the bolt material;

[0015] The initial design parameters of the top cover bolts are numerically calculated using empirical formulas to obtain the minimum cross-sectional comprehensive stress value σ3 of the bolts under normal operating conditions, the minimum cross-sectional comprehensive stress value σ4 of the bolts under load rejection conditions, and the empirical formula ratio ρ2 of the bolt preload to the working load under normal operating conditions;

[0016] If the first stress value σ1 and the second stress value σ2 are both smaller than the standard empirical stress value, the minimum cross-sectional comprehensive stress value σ3 of the bolt under the normal operating condition and the minimum cross-sectional comprehensive stress value σ4 of the bolt under the load rejection condition are both smaller than the standard value of the minimum cross-sectional comprehensive stress of the bolt, and the empirical formula ratio ρ2 is greater than the standard empirical formula ratio, then it is determined that the top cover bolt calculated by the empirical formula meets the safety requirements; otherwise, it is determined that the top cover bolt calculated by the empirical formula does not meet the safety requirements, and the standard empirical stress value is 0.8σ s The standard value of the minimum cross-sectional comprehensive stress of the bolt is min(σ s / 3,σ b / 5), the standard empirical formula ratio is 2, where σ s is the yield limit value of the bolt material, σ b is the strength limit value of the bolt material;

[0017] If the top cover handle bolt calculated by finite element calculation meets the safety requirements and the top cover handle bolt calculated by numerical calculation of the empirical formula meets the safety requirements, then it is determined that the top cover handle bolt corresponding to the initial parameters meets the safety requirements for use; if it does not meet the safety requirements, then the initial design parameters of the top cover handle bolt are modified and the above steps are repeated.

[0018] Optionally, the performing finite element calculation of the top cover bolt under the pre-tightening state under normal operating conditions and load rejection conditions according to the initial design parameters of the top cover bolt includes:

[0019] Establish an overall joint model based on the turbine's top cover, seat ring and top cover bolts;

[0020] Meshing the overall joint model, setting boundary conditions and setting loads to obtain a processing model;

[0021] The initial design parameters of the top cover handle bolts are input into the processing model, and finite element calculations are performed on the top cover handle bolts under normal operating conditions and load rejection conditions considering the preload state, and finite element calculations are performed on the top cover handle bolts under normal operating conditions without considering the preload state.

[0022] Optionally, performing numerical calculations of the top cover bolts under normal operating conditions and load rejection conditions using empirical formulas according to initial design parameters of the top cover bolts includes:

[0023] The initial design parameters include the number of bolts N, the water thrust load P1 of the top cover under normal operating conditions, the water thrust load P2 of the top cover under load rejection conditions, and the minimum diameter of the bolt thread d min , elastic modulus E of the bolt material, bolt length l, nut outer diameter d nut , bolt hole diameter d hole , top cover flange thickness h, bolt preload F v , Bolt material yield limit value σ s And the bolt material strength limit value σ b ;

[0024] The empirical formula includes a stress formula generated by a working load under normal operating conditions, a stress formula generated by a working load under load shedding conditions, a comprehensive stress formula for the minimum cross-section of bolts under normal operating conditions, a comprehensive stress value formula for the minimum cross-section of bolts under normal operating conditions, a comprehensive stress formula for the minimum cross-section of bolts under load shedding conditions, and a ratio formula for the bolt preload to the working load under normal operating conditions, wherein the stress formula generated by the working load under normal operating conditions is used to calculate a first stress value σ1, the stress formula generated by the working load under load shedding conditions is used to calculate a second stress value σ2, the comprehensive stress formula for the minimum cross-section of bolts under normal operating conditions is used to calculate a comprehensive stress value σ3 of the minimum cross-section of bolts under normal operating conditions, the comprehensive stress formula for the minimum cross-section of bolts under load shedding conditions is used to calculate a comprehensive stress value σ4 of the minimum cross-section of bolts under load shedding conditions, and the ratio formula for the bolt preload to the working load under normal operating conditions is used to calculate an empirical formula ratio ρ2;

[0025] The stress formula generated by the working load under normal operating conditions is:

[0026]

[0027] The stress formula generated by the working load of the load rejection condition is:

[0028]

[0029] The formula for the minimum cross-sectional comprehensive stress of bolts under normal operating conditions is:

[0030] The formula for the minimum cross-sectional comprehensive stress of bolts under load rejection conditions is:

[0031]

[0032] The formula for the ratio of bolt preload to working load under normal operating conditions is:

[0033]

[0034] The bolt preload stress is: The ratio of preload stress to bolt material yield limit is: The residual preload force under normal operating conditions is: F y1 =F v -(1-λ)F1; the residual preload force under load rejection is: F y2 =F v -(1-λ)F2; The working load of a single bolt under normal operating conditions is: The working load of a single bolt in the load shedding condition is: The minimum cross-sectional area of ​​the bolt is: The bolt stiffness is: The seat ring stiffness is:

[0035] The relative stiffness of the bolt and seat ring connection is:

[0036] A terminal device includes a memory and a processor. The memory stores a computer program that can be run on the processor. When the processor loads and executes the computer program, a method for assessing the safety of the top cover bolts of a hydro-turbine generator set is adopted.

[0037] A computer-readable storage medium stores a computer program. When the computer program is loaded and executed by a processor, a method for assessing the safety of a top cover bolt of a hydro-turbine generator set is adopted.

[0038] The beneficial effects of the present invention are:

[0039] 1. Effectively avoid the problem of insufficient accuracy in the strength verification and selection calculation of the top cover bolts caused by using only the empirical formula method or the finite element method for calculation. Avoid the problem of excessive calculation deviation caused by the determination of various empirical values ​​of bolt loads in the empirical formula for bolt selection in the mechanical design manual and the problem of poor accuracy of bolt stress results due to a large amount of simplification of bolt connections in finite element analysis.

[0040] 2. An empirical formula method or finite element method evaluation criteria for strength verification and selection calculation of the top cover bolts has been established. Through the respective advantages of the empirical formula method and the finite element method in strength verification and selection calculation, and on the premise that both methods meet the evaluation criteria, the accuracy of strength verification and selection calculation of the top cover bolts of the hydro-generator set can be effectively guaranteed, so as to guide designers to make the right choice when selecting, avoid major accidents caused by loose or broken top cover bolts, and ensure the safe and stable operation of the unit and key components. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1The present invention is a flow chart of a method for assessing the safety of bolts on a top cover of a hydro-turbine generator set. DETAILED DESCRIPTION

[0042] A method for assessing the safety of the top cover bolts of a hydro-turbine generator set. Figure 1 As shown, the present invention includes:

[0043] S1. Obtain the initial design parameters of the top cover handle bolts.

[0044] S2. According to the initial design parameters of the top cover bolts, the top cover bolts under normal operating conditions and load rejection conditions are numerically calculated using empirical formulas to obtain the first stress value σ1 generated by the working load under normal operating conditions and the second stress value σ2 generated by the working load under load rejection conditions.

[0045] S3. According to the initial design parameters of the top cover bolt, finite element calculations are performed on the top cover bolt under normal operating conditions and load rejection conditions under preload conditions to obtain the first comprehensive average stress value of the middle section of the top cover bolt. and the second comprehensive mean stress value

[0046] S4. Compare the first stress value σ1 and the first comprehensive average stress value under normal operating conditions. The first deviation value and the second stress value σ2 and the second comprehensive average stress value under the load rejection condition are compared. If the first deviation value and the second deviation value are both less than 10%, it is determined that the finite element calculation is correct, otherwise the finite element calculation is performed again.

[0047] S5. According to the initial design parameters of the top cover bolts, finite element calculation is performed on the top cover bolts in the normal operating condition and the load rejection condition, considering the preload state, to obtain the comprehensive local maximum stress value δ1 of the first bolt and the comprehensive local maximum stress value δ2 of the second bolt.

[0048] S6. According to the initial design parameters of the top cover bolts, finite element calculation is performed on the top cover bolts in the normal operating condition and the load rejection condition, considering the preload state, to obtain the comprehensive local maximum stress value δ1 of the first bolt and the comprehensive local maximum stress value δ2 of the second bolt.

[0049] S7. When the finite element calculation is correct, if the first comprehensive average stress value and the second comprehensive mean stress value Both are smaller than the first stress standard value and the third comprehensive average stress value. If the comprehensive average stress is less than the standard value, the comprehensive local maximum stress value of the first bolt δ1 and the comprehensive local maximum stress value of the second bolt δ2 are both less than the standard value of the comprehensive local maximum stress of the bolt, and the ratio of the bolt preload to the working load ρ1 is greater than the standard ratio, it is determined that the top cover bolt calculated by the finite element method meets the safety requirements. Otherwise, it is determined that the top cover bolt calculated by the finite element method does not meet the safety requirements, and the standard value of the first stress is 4σ s / 5, the standard value of comprehensive average stress is min(σ s / 3,σ b / 5), the standard value of the comprehensive local maximum stress of the bolt is min(σ s / 3,σ b / 5), the standard ratio is 2, where σ s is the yield limit value of the bolt material, σ b is the ultimate strength value of the bolt material.

[0050] S8. The initial design parameters of the top cover bolts are numerically calculated using empirical formulas to obtain the minimum cross-sectional comprehensive stress value σ3 of the bolts under normal operating conditions, the minimum cross-sectional comprehensive stress value σ4 of the bolts under load rejection conditions, and the empirical formula ratio ρ2 of the bolt preload force to the working load under normal operating conditions.

[0051] S9. If the first stress value σ1 and the second stress value σ2 are both smaller than the standard empirical stress value, the minimum cross-sectional comprehensive stress value σ3 of the bolt under normal operating conditions and the minimum cross-sectional comprehensive stress value σ4 of the bolt under load rejection conditions are both smaller than the standard value of the minimum cross-sectional comprehensive stress of the bolt, and the empirical formula ratio ρ2 is greater than the standard empirical formula ratio, then it is determined that the top cover bolt calculated by the empirical formula meets the safety requirements. Otherwise, it is determined that the top cover bolt calculated by the empirical formula does not meet the safety requirements, and the standard empirical stress value is 0.8σ s The standard value of the minimum cross-sectional comprehensive stress of the bolt is min(σ s / 3,σ b / 5), the standard empirical formula ratio is 2,

[0052] Among them, σ s is the yield limit value of the bolt material, σ b is the ultimate strength value of the bolt material.

[0053] S10. If the top cover handle bolt calculated by finite element method meets the safety requirements and the top cover handle bolt calculated by numerical formula meets the safety requirements, then determine that the top cover handle bolt corresponding to the initial parameters meets the safety requirements; if it does not meet the safety requirements, modify the initial design parameters of the top cover handle bolt and repeat the above steps.

[0054] In one implementation of this embodiment, step S2, i.e., performing finite element calculations on the top cover handle bolts under normal operating conditions and load rejection conditions considering the pre-tightening state according to the initial design parameters of the top cover handle bolts, includes:

[0055] S21. Establish an overall joint model based on the turbine's top cover, seat ring and top cover bolts.

[0056] S22. Meshing the overall joint model, setting boundary conditions and setting loads to obtain a processing model.

[0057] S23. Input the initial design parameters of the top cover bolts into the processing model, perform finite element calculations on the top cover bolts under normal operating conditions and load rejection conditions with preload states in mind, and perform finite element calculations on the top cover bolts under normal operating conditions without preload states in mind.

[0058] In one implementation of this embodiment, step S3, namely, performing numerical calculations of the top cover bolts in normal operation and load rejection conditions according to the initial design parameters of the top cover bolts, includes:

[0059] S31. Initial design parameters include the number of bolts N, the water thrust load of the top cover under normal operating conditions P1, the water thrust load of the top cover under load rejection conditions P2, and the minimum diameter of the bolt thread d min , elastic modulus E of the bolt material, bolt length l, nut outer diameter d nut , bolt hole diameter d hole , top cover flange thickness h, bolt preload F v , Bolt material yield limit value σ s And the bolt material strength limit value σ b .

[0060] S32. The empirical formula includes the stress formula generated by the working load under normal operating conditions, the stress formula generated by the working load under load shedding conditions, the comprehensive stress formula of the minimum cross-section of bolts under normal operating conditions, the comprehensive stress value formula of the minimum cross-section of bolts under normal operating conditions, the comprehensive stress formula of the minimum cross-section of bolts under load shedding conditions, and the ratio formula of the bolt preload to the working load under normal operating conditions. The stress formula generated by the working load under normal operating conditions is used to calculate the first stress value σ1, the stress formula generated by the working load under load shedding conditions is used to calculate the second stress value σ2, the comprehensive stress formula of the minimum cross-section of bolts under normal operating conditions is used to calculate the comprehensive stress value σ3 of the minimum cross-section of bolts under normal operating conditions, the comprehensive stress formula of the minimum cross-section of bolts under load shedding conditions is used to calculate the comprehensive stress value σ4 of the minimum cross-section of bolts under load shedding conditions, and the ratio formula of the bolt preload to the working load under normal operating conditions is used to calculate the empirical formula ratio ρ2.

[0061] The stress formula generated by the working load under normal operating conditions is:

[0062]

[0063] The stress formula generated by the working load of the load rejection condition is:

[0064]

[0065] The formula for the minimum cross-sectional comprehensive stress of bolts under normal operating conditions is:

[0066] The formula for the minimum cross-sectional comprehensive stress of bolts under load rejection conditions is:

[0067]

[0068] The formula for the ratio of bolt preload to working load under normal operating conditions is:

[0069]

[0070] The bolt preload stress is: The ratio of preload stress to bolt material yield limit is: The residual preload under normal operating conditions is: F y1 =F v -(1-λ)F1. The residual preload force under load rejection is: F y2 =F v -(1-λ)F2. The working load of a single bolt under normal operating conditions is: The working load of a single bolt in the load shedding condition is: The minimum cross-sectional area of ​​the bolt is: The bolt stiffness is: The seat ring stiffness is:

[0071] The relative stiffness of the bolt and seat ring connection is:

[0072] In this embodiment, an empirical formula numerical calculation method is used to calculate the stress generated by the working load of the top cover bolt under normal operating conditions and load rejection conditions and the comprehensive stress of the minimum cross-section of the bolt, as well as the ratio of the bolt preload to the working load under normal operating conditions, so as to make an accurate evaluation.

[0073] The embodiment of the present application also discloses a terminal device, including a memory and a processor. The memory stores a computer program that can be run on the processor. When the processor loads and executes the computer program, a method for evaluating the safety of the top cover bolts of a hydro-turbine generator set is adopted.

[0074] The terminal device may be a computer device such as a desktop computer, a laptop computer or a cloud server, and the terminal device includes but is not limited to a processor and a memory. For example, the terminal device may also include input and output devices, a network access device and a bus.

[0075] Among them, the processor can adopt a central processing unit (CPU). Of course, according to actual usage, other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. can also be adopted. The general-purpose processor can adopt a microprocessor or any conventional processor, etc., and this application does not impose any restrictions on this.

[0076] Among them, the memory can be an internal storage unit of the terminal device, such as a hard disk or memory of the terminal device, or it can be an external storage device of the terminal device, such as a plug-in hard disk, a smart memory card (SMC), a secure digital card (SD) or a flash memory card (FC) equipped on the terminal device, etc., and the memory can also be a combination of an internal storage unit and an external storage device of the terminal device. The memory is used to store computer programs and other programs and data required by the terminal device. The memory can also be used to temporarily store data that has been output or is to be output, and this application does not impose any restrictions on this.

[0077] Among them, through this terminal device, a method for assessing the safety of the bolts of the top cover of a hydro-turbine generator set in the above embodiment is stored in the memory of the terminal device, and is loaded and executed on the processor of the terminal device for easy use.

[0078] An embodiment of the present application further discloses a computer-readable storage medium, and the computer-readable storage medium stores a computer program, wherein when the computer program is executed by a processor, a method for assessing the safety of the top cover bolts of a hydro-turbine generator set in the above embodiment is adopted.

[0079] Among them, the computer program can be stored in a computer-readable medium, the computer program includes computer program code, the computer program code can be in the form of source code, object code, executable file or certain middleware, etc. The computer-readable medium includes any entity or device that can carry the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal and software distribution medium, etc. It should be noted that the computer-readable medium includes but is not limited to the above-mentioned components.

[0080] Among them, through this computer-readable storage medium, a method for assessing the safety of the bolts of the top cover of a hydro-turbine generator set in the above embodiment is stored in a computer-readable storage medium, and is loaded and executed on a processor to facilitate the storage and application of the above method.

[0081] A person skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of protection of the present application is limited to these examples. In line with the concept of the present application, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of different aspects of one or more embodiments of the present application as above, which are not provided in detail for the sake of simplicity.

[0082] One or more embodiments of the present application are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the present application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of the present application should be included in the protection scope of the present application.

Claims

1. A method for assessing the safety of the top cover bolts of a hydro-turbine generator set, characterized in that: include: Obtain the initial design parameters of the top cover handle bolts; According to the initial design parameters of the top cover bolt, the top cover bolts under normal operating conditions and load rejection conditions are numerically calculated using empirical formulas to obtain a first stress value σ1 generated by the working load under normal operating conditions and a second stress value σ2 generated by the working load under load rejection conditions; According to the initial design parameters of the top cover bolt, finite element calculations are performed on the top cover bolt under normal operating conditions and load rejection conditions under preload conditions to obtain the first comprehensive average stress value of the middle section of the top cover bolt. and the second comprehensive mean stress value Compare the first stress value σ1 and the first comprehensive average stress value under normal operating conditions The first deviation value and the second stress value σ2 and the second comprehensive average stress value under the load rejection condition are compared. If both the first deviation value and the second deviation value are less than 10%, it is determined that the finite element calculation is correct, otherwise the finite element calculation is performed again; According to the initial design parameters of the top cover bolt, a finite element calculation is performed on the top cover bolt without considering the preload state under normal operating conditions to obtain the third comprehensive average stress value of the middle section of the top cover bolt. According to the initial design parameters of the top cover bolt, finite element calculation is performed on the top cover bolt in the normal operation condition and the load rejection condition, considering the pre-tightening state, to obtain the comprehensive local maximum stress value δ1 of the first bolt and the comprehensive local maximum stress value δ2 of the second bolt; When the finite element calculation is correct, if the first comprehensive average stress value and the second integrated mean stress value are all less than the first stress standard value and the third comprehensive average stress value If the value of the comprehensive average stress is less than the standard value, the comprehensive local maximum stress value δ1 of the first bolt and the comprehensive local maximum stress value δ2 of the second bolt are both less than the standard value of the comprehensive local maximum stress of the bolt, and the ratio ρ1 of the bolt preload to the working load is greater than the standard ratio, it is determined that the top cover bolt calculated by the finite element method meets the safety requirements. Otherwise, it is determined that the top cover bolt calculated by the finite element method does not meet the safety requirements, and the first stress standard value is 4σ s / 5, the standard value of comprehensive average stress is min(σ s / 3,σ b / 5), the standard value of the comprehensive local maximum stress of the bolt is min(σ s / 3,σ b / 5), the standard ratio is 2, where σ s is the yield limit value of the bolt material, σ b is the strength limit value of the bolt material; The initial design parameters of the top cover bolts are numerically calculated using empirical formulas to obtain the minimum cross-sectional comprehensive stress value σ3 of the bolts under normal operating conditions, the minimum cross-sectional comprehensive stress value σ4 of the bolts under load rejection conditions, and the empirical formula ratio ρ2 of the bolt preload to the working load under normal operating conditions; If the first stress value σ1 and the second stress value σ2 are both smaller than the standard empirical stress value, the minimum cross-sectional comprehensive stress value σ3 of the bolt under the normal operating condition and the minimum cross-sectional comprehensive stress value σ4 of the bolt under the load rejection condition are both smaller than the standard value of the minimum cross-sectional comprehensive stress of the bolt, and the empirical formula ratio ρ2 is greater than the standard empirical formula ratio, then it is determined that the top cover bolt calculated by the empirical formula meets the safety requirements; otherwise, it is determined that the top cover bolt calculated by the empirical formula does not meet the safety requirements, and the standard empirical stress value is 0.8σ s The standard value of the minimum cross-sectional comprehensive stress of the bolt is min(σ s / 3,σ b / 5) The standard empirical formula ratio is 2, where σ s is the yield limit value of the bolt material, σ b is the strength limit value of the bolt material; If the top cover handle bolt calculated by finite element calculation meets the safety requirements and the top cover handle bolt calculated by numerical calculation of the empirical formula meets the safety requirements, then it is determined that the top cover handle bolt corresponding to the initial parameters meets the safety requirements for use; if it does not meet the safety requirements, then the initial design parameters of the top cover handle bolt are modified and the above steps are repeated.

2. The method for evaluating the safety of the top cover bolts of a hydro-generator set according to claim 1, characterized in that: The finite element calculation of the top cover bolt under the pre-tightening state under the normal operating condition and the load rejection condition according to the initial design parameters of the top cover bolt comprises: Establish an overall joint model based on the turbine's top cover, seat ring and top cover bolts; Meshing the overall joint model, setting boundary conditions and setting loads to obtain a processing model; The initial design parameters of the top cover handle bolts are input into the processing model, and finite element calculations are performed on the top cover handle bolts under normal operating conditions and load rejection conditions considering the preload state, and finite element calculations are performed on the top cover handle bolts under normal operating conditions without considering the preload state.

3. The method for evaluating the safety of the top cover bolts of a hydro-generator set according to claim 1, wherein: The empirical formula numerical calculation of the top cover bolts under normal operating conditions and load rejection conditions according to the initial design parameters of the top cover bolts includes: The initial design parameters include the number of bolts N, the water thrust load P1 of the top cover under normal operating conditions, the water thrust load P2 of the top cover under load rejection conditions, and the minimum diameter of the bolt thread d min , elastic modulus E of the bolt material, bolt length l, nut outer diameter d nut , bolt hole diameter d hole , top cover flange thickness h, bolt preload F v , Bolt material yield limit value σ s And the bolt material strength limit value σ b ; The empirical formula includes a stress formula generated by a working load under normal operating conditions, a stress formula generated by a working load under load shedding conditions, a comprehensive stress formula for the minimum cross-section of bolts under normal operating conditions, a comprehensive stress value formula for the minimum cross-section of bolts under normal operating conditions, a comprehensive stress formula for the minimum cross-section of bolts under load shedding conditions, and a ratio formula for the bolt preload to the working load under normal operating conditions, wherein the stress formula generated by the working load under normal operating conditions is used to calculate a first stress value σ1, the stress formula generated by the working load under load shedding conditions is used to calculate a second stress value σ2, the comprehensive stress formula for the minimum cross-section of bolts under normal operating conditions is used to calculate a comprehensive stress value σ3 of the minimum cross-section of bolts under normal operating conditions, the comprehensive stress formula for the minimum cross-section of bolts under load shedding conditions is used to calculate a comprehensive stress value σ4 of the minimum cross-section of bolts under load shedding conditions, and the ratio formula for the bolt preload to the working load under normal operating conditions is used to calculate an empirical formula ratio ρ2; The stress formula generated by the working load under normal operating conditions is: The stress formula generated by the working load of the load rejection condition is: The formula for the minimum cross-sectional comprehensive stress of bolts under normal operating conditions is: The formula for the minimum cross-sectional comprehensive stress of bolts under load rejection conditions is: The formula for the ratio of bolt preload to working load under normal operating conditions is: The bolt preload stress is: The ratio of preload stress to bolt material yield limit is: The residual preload force under normal operating conditions is: F y1 =F v -(1-λ)F1; The residual preload force under load rejection condition is: F y2 =F v -(1-λ)F2; The working load of a single bolt under normal operating conditions is: The working load of a single bolt in the load shedding condition is: The minimum cross-sectional area of ​​the bolt is: The bolt stiffness is: The seat ring stiffness is: The relative stiffness of the bolt and seat ring connection is:

4. A terminal device, comprising a memory and a processor, characterized in that: The memory stores a computer program that can be run on the processor, and when the processor loads and executes the computer program, the method according to any one of claims 1 to 3 is adopted.

5. A computer-readable storage medium, wherein a computer program is stored in the computer-readable storage medium, characterized in that: When the computer program is loaded and executed by a processor, the method according to any one of claims 1 to 3 is adopted.

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