A structural optimization method for a turbine blade bearing and its dual components

Abstract

The present invention discloses a structural optimization method for a turbine blade bearing and its dual components, which specifically includes the following steps: S1, force analysis of the bearing and the blade pivot part in the runner mechanism, the maximum support reaction force and the minimum support reaction force; S2, finite element simulation modeling based on the minimum support reaction force and the maximum support reaction force, and finite element modeling analysis combined with the maximum head working condition and the rated head working condition, to obtain the analysis results of the bearing contact pressure under different working conditions, and according to the analysis results, it is concluded that the cause of bearing wear is excessive end face contact pressure; S3, using an analytical method to perform force analysis on the bearing and calculate and analyze the bearing contact pressure, and compare the calculation results with the finite element analysis results; S4, an optimization plan is proposed based on the cause of bearing wear obtained by the finite element analysis and the verification results of the analytical method. The invention can effectively analyze the cause of the sweeping phenomenon in the turbine and propose a structural optimization plan.

Description

Technical Field

[0001] The invention relates to the technical field of water turbine runner mechanisms, and in particular to a method for optimizing the structure of a water turbine blade bearing and its dual components. Background Art

[0002] The axial wear of the blade bearing will cause the gap between the blade and the runner chamber to become smaller when the unit is running. Due to the operating characteristics of the bulb-type turbine, the gap changes at different operating positions of the blade. This operating state further aggravates the unevenness of the blade running gap, which will lead to increased pressure pulsation, increased vibration swing value of the unit, and increased noise. When the end face wear of the blade bearing reaches a certain value, it will cause metal collision between the blade and the runner chamber, and this collision is a periodic rotational impact, which is easy to cause fatigue cracks in the runner chamber and a catastrophic major accident in the power station.

[0003] The propeller turbine is mainly used in hydropower stations with low head and large flow. Its runner blade is a cantilever beam structure. The blade acts on the runner bearing through the pivot to apply axial water thrust, water torque, blade gravity and centrifugal force to the runner body. During the blade opening adjustment process of the unit, friction between the bearing and the pivot is inevitable, resulting in wear between the pivot and the bearing surface. If the bearing material performance is poor, the bearing matrix may even break under the action of pressure. Due to the inherent characteristics of the propeller turbine runner structure, there is a certain inclination angle between the blade pivot center and the runner bearing center, which causes uneven force on the bearing, and its wear state is bound to be eccentric wear. When the bearing wear is large or damaged, the inclination angle between the blade pivot center and the runner bearing center increases, the blade seal compensation is insufficient, and the runner leaks oil and water ingress occurs. Therefore, the performance of the impeller pivot bearing of a propeller turbine directly affects the effectiveness of the blade seal. The service life of the pivot bearing determines the overhaul period of the unit and even affects the normal operation of the unit. The end face wear of the blade bearing will lead to changes in the gap between the blade and the impeller chamber. In severe cases, the blade "sweeping the bore" phenomenon will occur, seriously affecting the economic and social benefits of the power plant.

[0004] However, the cost of replacing the impeller mechanism in the turbine is too high, and without targeted replacement, it is impossible to fundamentally optimize the impeller mechanism in the turbine to reduce the impact of wear. Therefore, the applicant believes that it is necessary to provide a method for wear analysis and optimization of the bearing and its mating parts. Summary of the invention

[0005] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0006] To achieve the above object, the present invention proposes a method for optimizing the structure of a turbine blade bearing and its counterpart, comprising the following steps:

[0007] S1. Perform force analysis on the bearing and blade pivot in the runner mechanism to obtain the support reaction force acting on the blade pivot when the blade is in the rotating state and the stopped state under the maximum water head condition;

[0008] S2. According to different working conditions, finite element simulation modeling is carried out in combination with two groups of support reaction forces, and finite element analysis of different parts of the bearing is carried out on the finite element modeling in combination with the maximum head working condition and the rated head working condition, and the analysis results of the bearing contact pressure under different working conditions are obtained. According to the analysis results, it is concluded that the cause of bearing wear is excessive end face contact pressure;

[0009] S3. Use analytical methods to analyze the bearing force and calculate the bearing contact pressure to obtain the bearing contact pressure under various working conditions, and compare the calculation results with the finite element analysis results to verify whether the bearing wear cause obtained in the finite element analysis is correct;

[0010] S4. Based on the causes of bearing wear obtained through finite element analysis and the results of analytical verification, an optimization plan is proposed. The structural specifications of the bearing are adjusted, the outer diameter of the bearing and its dual component is increased, and the optimization plan is again subjected to finite element analysis and analytical verification under various working conditions to verify the feasibility of the optimization plan.

[0011] The present invention performs finite element analysis on the bearing under different working conditions, thereby calculating and analyzing the end face contact pressure of the bearing and the radial contact pressure of the bearing, and then obtains the friction cause of the bearing, and uses an analytical method to calculate and analyze the end face contact pressure of the bearing and the radial contact pressure of the bearing under the same working conditions, so as to ensure that the friction cause obtained by the finite element analysis is in line with the actual result, and analyzes the bearing according to the friction cause to obtain a method for optimizing and improving the structural specifications of the bearing, so as to perform wear analysis on the bearing part and perform structural optimization and improvement without replacing the entire impeller operating mechanism.

[0012] Optionally, after the force analysis of the bearing and slurry pivot part in S1, the water torque and water thrust of the blade pivot in the wheel mechanism are calculated to obtain the maximum water head and minimum water head of the blade pivot in the working state, and the minimum operating oil pressure of the wheel mechanism is calculated based on the maximum water head and the minimum water head to obtain the maximum support reaction force acting on the lower blade pivot under the maximum water head condition and the minimum support reaction force acting on the blade pivot under the minimum water head condition.

[0013] Furthermore, in S2, both the bearing and the impeller are modeled during the finite element analysis, and when modeling the impeller, the analysis model established according to the periodic symmetry of the impeller is a period of the impeller including one blade, and periodic symmetric boundary conditions are applied on the section surface to constrain the circumferential degrees of freedom of the nodes at the blade pivot link; a contact unit is used at the contact between the impeller pivot and the bearing.

[0014] Furthermore, in S2, when simulating the working condition by the finite element method, it is necessary to simulate the working condition of the rated head and rated output as well as the working condition of the maximum head and rated output.

[0015] Furthermore, in S2, the finite element analysis of the bearing includes an analysis of the end face contact stress of the bearing and an analysis of the radial contact stress of the bearing, and finite element analysis is performed on the end face contact pressure and radial contact pressure of the bearing under the conditions of rated head and rated output and maximum head and rated output, respectively, to obtain the analysis results of the end face contact pressure and radial contact pressure of the bearing under different working conditions.

[0016] Furthermore, in S2, a constraint input for the edge contact pressure factor is added during the finite element analysis process, and the finite element analysis is performed again on the bearing end face contact pressure and the radial contact pressure under the conditions of rated head and rated output and maximum head and rated output, thereby obtaining the results of the bearing end face contact pressure and the bearing radial contact pressure under different working conditions when the influence of the edge contact pressure factor is considered, so as to determine the influence of the edge contact pressure on the bearing end face contact pressure and the radial contact pressure.

[0017] Furthermore, in the S2 analysis, a deformation distribution finite element analysis is performed on the bearing to simulate and observe the deformation position of the bearing. The deformation distribution finite element analysis includes:

[0018] The radial deformation distribution of the bearing and the deformation distribution of the bearing end face under the rated head and rated output conditions;

[0019] The radial deformation distribution of the bearing and the deformation distribution of the bearing end face under the conditions of maximum head and rated output;

[0020] The radial deformation distribution of the bearing under rated head and rated output conditions and the radial deformation distribution of the bearing;

[0021] The radial deformation distribution of the bearing under the maximum head and rated output conditions and the radial deformation distribution of the bearing.

[0022] Furthermore, when verifying the optimization scheme, the optimization scheme is verified by finite element analysis and analytical calculation according to steps S2 and S3 to determine the feasibility of the optimization scheme.

[0023] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0025] Figure 1 A flow chart of the steps for theoretically analyzing the bearing bush and its counterpart and proposing a structural optimization solution for the present invention;

[0026] Figure 2 It is a schematic diagram of finite element modeling of the runner in the theoretical analysis of the bearing and its dual components to propose a structural optimization plan;

[0027] Figure 3 It is a flow chart of the steps of testing and analyzing the bearing bush and its counterpart to propose a material optimization solution;

[0028] Figure 4 It is a flowchart of the specific steps of A2 in proposing a material optimization solution for the test analysis of the bearing and its counterpart. DETAILED DESCRIPTION

[0029] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0030] At present, turbines in hydroelectric power stations generally have faults caused by wear of blade bearings and their counterparts due to long-term use. Taking Hongjiang Power Plant as an example, the units have experienced blade ejection after 6-8 years of operation due to wear of blade bearings and their counterparts. The blade ejection causes the runner chamber to sweep, which seriously threatens the safe and stable operation of the unit. Therefore, it is necessary to optimize the structural design of blade bearings and their counterparts and the wear performance of the materials to enhance the wear resistance and self-lubricating performance of the bearings and their counterparts.

[0031] The present invention provides a method for optimizing a turbine blade bearing and its counterpart, including a method for optimizing the structure of the turbine blade bearing and its counterpart and a method for optimizing the material thereof, including a theoretical analysis part and an experimental analysis part. Through theoretical analysis, the contact stress and contact deformation of the bearing and the counterpart are analyzed. The counterpart includes a swing arm and a blade pivot. In order to find the position and the cause of wear, the slurry bearing and its counterpart are structurally optimized according to the cause of wear, and the bearing and its counterpart are materially analyzed and optimized according to the cause of wear, so as to enhance the wear resistance and self-lubricating and anti-friction performance of the bearing and its counterpart. The structural optimization and material optimization of the bearing and its counterpart are described in detail below.

[0032] Firstly, the bearing and its dual components are theoretically analyzed to propose a structural optimization scheme for the bearing and its dual components. Figure 1 , specifically including the following steps:

[0033] S1. Perform force analysis on the bearing and blade pivot in the runner mechanism to obtain the support reaction force acting on the blade pivot when the blade is in the rotating state and the stopped state under the maximum water head condition;

[0034] S2. According to different working conditions, finite element simulation modeling is carried out in combination with two groups of support reaction forces, and finite element analysis of different parts of the bearing is carried out on the finite element modeling in combination with the maximum head working condition and the rated head working condition, and the analysis results of the bearing contact pressure under different working conditions are obtained. According to the analysis results, it is concluded that the cause of bearing wear is excessive end face contact pressure;

[0035] S3. Use analytical methods to analyze the bearing force and calculate the bearing contact pressure to obtain the bearing contact pressure under various working conditions, and compare the calculation results with the finite element analysis results to verify whether the bearing wear cause obtained in the finite element analysis is correct;

[0036] S4. Based on the causes of bearing wear obtained through finite element analysis and the results of analytical verification, an optimization plan is proposed. The structural specifications of the bearing are adjusted, the outer diameter of the bearing and its dual component is increased, and the optimization plan is again subjected to finite element analysis and analytical verification under various working conditions to verify the feasibility of the optimization plan.

[0037] Among them, after the force analysis of the bearing and slurry pivot part in S1, the water moment and water thrust of the blade pivot in the wheel mechanism are calculated to obtain the maximum water head and minimum water head of the blade pivot in the working state, that is, the maximum force and minimum force generated by the water flow acting on the blade pivot in the radial direction, and the minimum operating oil pressure of the wheel mechanism is calculated according to the maximum water head and the minimum water head, and the support reaction force acting on the lower blade pivot when the blade is in the open state, i.e., the rotating state, under the maximum water head working condition and the support reaction force acting on the blade pivot when the blade is closed and loaded, i.e., the blade stops rotating, is obtained.

[0038] After the calculation in S1 is completed, two sets of support reaction forces acting on the blade pivot under different working conditions of the blade under the maximum water head are obtained. In order to carry out the finite element analysis in S2, it is also necessary to collect other load data when the blade pivot is working, mainly including water pressure, gravity and speed data. The two sets of support reaction forces can be used as pressure constraints on the blade pivot caused by water pressure during finite element modeling, thereby ensuring that the working condition data input during the finite element analysis process will not cause excessive deviations in the results.

[0039] In S2, ANSYS finite element software is used for analysis. The bearing and the runner are modeled in the finite element analysis. When modeling the runner, reference is made to Figure 2 The analytical model established according to the periodic symmetry of the runner is a cycle of the runner containing one blade. One cycle refers to the part of the runner corresponding to a single blade. Periodic symmetric boundary conditions are applied on the section surface to constrain the circumferential degrees of freedom of the nodes at the blade pivot link. Contact units are used at the contact between the runner pivot and the bearing.

[0040] In S2, when simulating working conditions using the finite element method, it is necessary to simulate the working conditions of rated head and rated output as well as the working conditions of maximum head and rated output. The finite element analysis of the bearing includes the analysis of the end contact stress of the bearing and the analysis of the radial contact stress of the bearing, that is, the finite element analysis of the end contact pressure and radial contact pressure of the bearing is performed under the working conditions of rated head and rated output and the working conditions of maximum head and rated output, respectively, so as to obtain the analysis results of the end contact pressure and radial contact pressure of the bearing under different working conditions. According to different working conditions and analysis positions, the following analysis objects are specifically included:

[0041] The contact pressure distribution of the bearing end face under the rated head and rated output conditions;

[0042] The radial contact pressure distribution of the bearing under the rated head and rated output conditions;

[0043] The contact pressure distribution of the bearing end face under the conditions of maximum water head and rated output;

[0044] Radial contact pressure distribution of bearing under maximum head and rated output conditions.

[0045] In S2, the constraint input of the edge contact pressure factor is added in the finite element analysis process, and the finite element analysis of the bearing end face contact pressure and radial contact pressure under the conditions of rated head and rated output and maximum head and rated output is performed again. The specific analysis objects include:

[0046] Under rated head and rated output conditions, consider the edge contact pressure and the contact pressure distribution of the bearing end face;

[0047] Under rated head and rated output conditions, consider the edge contact pressure and the radial contact pressure distribution of the bearing;

[0048] Under the condition of maximum water head and rated output, consider the edge contact pressure and the contact pressure distribution of the bearing end face;

[0049] Under the condition of maximum water head and rated output, considering the edge contact pressure, the radial contact pressure distribution of the bearing;

[0050] Thus, the results of the bearing end face contact pressure and the bearing radial contact pressure under different working conditions are obtained when the influence of the edge contact pressure factor is considered, so as to determine the influence of the edge contact pressure on the bearing end face contact pressure and the radial contact pressure.

[0051] In order to analyze the friction deformation of the bearing more intuitively, in the S2 analysis, the deformation distribution finite element analysis of the bearing is carried out to simulate and observe the deformation position of the bearing. Specifically, the end face and radial direction of the bearing need to be analyzed separately under different working conditions. The deformation distribution finite element analysis includes:

[0052] The radial deformation distribution of the bearing and the deformation distribution of the bearing end face under the rated head and rated output conditions;

[0053] The radial deformation distribution of the bearing and the deformation distribution of the bearing end face under the conditions of maximum head and rated output;

[0054] The radial deformation distribution of the bearing under rated head and rated output conditions and the radial deformation distribution of the bearing;

[0055] The radial deformation distribution of the bearing under the maximum head and rated output conditions and the radial deformation distribution of the bearing.

[0056] After finite element analysis and calculation, the analysis and calculation results of the bearing contact pressure and stress as well as the bearing deformation calculation results were summarized, and the finite element analysis results under various simulated working conditions were statistically analyzed, and it was found that the contact pressure on the end side of the bearing was relatively large. The large contact pressure will cause the corresponding friction force to be relatively large, that is, the large contact pressure on the end side of the bearing is the reason for the greater wear on the bearing position.

[0057] Furthermore, in the wheel mechanism, the end face of the bearing is in contact with the end face of the swing arm. The deformation of the swing arm itself due to the bearing will affect the end face of the bearing in contact with it. Therefore, when performing finite element analysis in S2, the contact stress between the swing arm and the retaining ring in the wheel mechanism is analyzed by finite element analysis, that is, the contact stress of the end face of the swing arm is analyzed by finite element analysis. Under the action of the contact stress, the swing arm itself will be deformed, so that the contact surface between the swing arm and the bearing will be worn. In the finite element analysis, it is necessary to obtain the maximum peak value and average stress of the compressive stress on the end face of the swing arm, so as to combine the finite element analysis results of the bearing to obtain the cause of the bearing wear, and see whether the swing arm yields under the action of the contact stress, resulting in wear of the swing arm and the bearing. In the finite element calculation process, it is only necessary to calculate the contact pressure, deformation and contact stress between the swing arm and the bearing. Therefore, when modeling the swing arm, the bearing is rigid, that is, there is no friction contact between the swing arm and the bearing, and the swing arm and the bearing are in elastic contact. When modeling, the elastic modulus and Poisson's ratio are selected as input data according to the bearing material. The force generated between the arm and the bearing is mainly caused by the force of the water thrust acting on the blade pivot. Therefore, when modeling, it is necessary to supplement the data input of the blade position where the water thrust is sourced. The water thrust of a single blade, the centrifugal force of the blade and the arm, and the blade mass are selected as input data to calculate and analyze the source of the water thrust.

[0058] According to the requirements of 4.2.2 working stress and safety factor of GB / T15468-2020 "Basic Technical Conditions for Water Turbines", the compressive stress of the workpiece should be ≤ tensile strength / 5 and yield strength / 3, and the stress analysis obtained by the finite element method should give the stress distribution, and the local stress cloud map should be pointed out, and the average stress and local stress of the component should be extracted. The average stress at the non-stress concentration point under normal working conditions and transitional working conditions shall not exceed the specified allowable stress, and the local stress (the calculation result of the finite element under the condition of considering the transition fillet) shall not exceed 2 / 3 of the material yield strength, and the local maximum stress under special working conditions shall not exceed the material yield strength. Fatigue strength calculation should be carried out for parts subjected to alternating stress. Therefore, when the contact stress of the swing arm is less than the allowable stress, it means that the swing arm will not produce strength yield, that is, the swing arm will not affect the bearing at this time; when the contact stress of the swing arm is close to or higher than the allowable stress, it means that the swing arm has produced strength yield, resulting in wear between the swing arm and the bearing, and it is necessary to consider replacing the materials of the swing arm and the bearing.

[0059] After analysis by the finite element analysis method, the stress distribution at the end and radial direction of the bearing and the deformation distribution of the bearing under different working conditions are determined. On the one hand, it can provide a theoretical basis for the structural optimization of the bearing and its dual components, and on the other hand, it can provide an experimental basis for the experimental analysis part. The experimental analysis part conducts material sampling and analysis on the wear part of the bearing and its dual components based on the finite element analysis part, and the dual components in this embodiment refer to the swing arm and the blade pivot.

[0060] Then, the bearing was subjected to stress analysis by analytical method to verify the results of finite element analysis. Due to the inherent characteristics of the impeller structure of the propeller turbine, there is a certain inclination angle between the center of the blade pivot and the center of the impeller bearing, which causes the blade pivot to tilt at the position of the bearing and its dual component, resulting in uneven force on the bearing. The wear of the end where the bearing and the blade pivot meet is more serious than that of the middle part of the bearing, and the wear state of the bearing must be eccentric wear. When the bearing wear is large or damaged, the inclination angle between the center of the blade pivot and the center of the impeller bearing increases, the blade seal compensation is insufficient, and the impeller leaks oil and water ingress occurs. At this time, due to eccentric wear, the end face friction of the bearing is serious, causing the blade pivot to deviate from the original rotation center line, and then the blade set on the blade pivot also deflects, the gap between the blade and the inner wall of the impeller chamber changes, and in severe cases, the bore is swept.

[0061] In S4, according to the cause of bearing wear obtained by finite element analysis and the results of analytical verification, it can be known that the cause of bearing wear is that the contact pressure of the bearing end face is too large, which makes the pressure at the contact position between the bearing and the blade pivot and the swing arm too large, resulting in bearing wear and deformation. Therefore, it is proposed to increase the outer diameter of the bearing and the swing arm in structure to reduce the compressive stress on the contact surface between the bearing and the swing arm, and between the bearing and the slurry pivot. In this embodiment, the outer diameter of the bearing and the swing arm is increased to 610mm. The optimization scheme is verified by finite element analysis again. According to the finite element analysis in S2, under the condition that other working conditions are exactly the same and only the outer diameter of the bearing and the outer diameter of the swing arm are changed, the specific finite element analysis of the bearing working conditions in the optimization scheme is as follows:

[0062] The contact pressure distribution of the bearing end face under the rated head and rated output conditions;

[0063] The radial contact pressure distribution of the bearing under the rated head and rated output conditions;

[0064] The contact pressure distribution of the bearing end face under the conditions of maximum water head and rated output;

[0065] The radial contact pressure distribution of the bearing under the conditions of maximum water head and rated output;

[0066] Under rated head and rated output conditions, consider the edge contact pressure and the contact pressure distribution of the bearing end face;

[0067] Under rated head and rated output conditions, consider the edge contact pressure and the radial contact pressure distribution of the bearing;

[0068] Under the condition of maximum water head and rated output, consider the edge contact pressure and the contact pressure distribution of the bearing end face;

[0069] Under the conditions of maximum head and rated output, the radial contact pressure distribution of the bearing is considered, taking into account the edge contact pressure.

[0070] By combining the finite element analysis results in S2 and the finite element analysis results of the optimization scheme in S4, the average compressive stress at the lower end and radial direction of the bearing under different working conditions before and after optimization is obtained, and the specific optimization data are compared to verify the feasibility of the optimization scheme. In this embodiment, the finite element analysis results before and after optimization of the water turbine of Hongjiang Power Plant are given as an example. The modeling simulation working conditions are collected through actual working conditions, specifically: the rated head is 20m, the maximum head is 27.3m, the rated speed of the turbine is 136.4rpm, the support reaction force of the blade pivot at the bearing when the blade rotates is 3378.23KN, and the support reaction force of the blade pivot at the bearing when the blade stops rotating is 2219.33KN; the rated head output is 45MW, the maximum head output is 47.3MW, and the gravity is 34.8KN. The optimization scheme increases the outer diameter of the bearing and the swing arm from 600mm to 610mm. The specific finite element analysis comparison results are as follows:

[0071]

[0072]

[0073] Comparison of the analysis results of the bearing end face proves that the structural optimization effect effectively reduces the average contact pressure of the bearing end under different working conditions, which means that the optimization scheme is feasible. At this time, the staff can optimize the structure of the slurry bearing and its dual components of the water turbine according to the optimization scheme. However, from the comparative finite element analysis results of the optimization scheme, the radial contact pressure changes little. The purpose of reducing the wear between the bearing and the blade pivot can be achieved by optimizing the materials of the bearing and the blade pivot. Considering that the blade pivot is not easy to replace, the bearing material is optimized to enhance the wear resistance of the bearing.

[0074] After the theoretical part of the structural optimization scheme for the bearing and its dual components was obtained, it was considered that if the bearing and its dual components were not optimized in terms of materials, the working environment of the bearing and its dual components would be relatively harsh. After a long period of work, only the structural modification and optimization would still cause the rotation centerline of the blade pivot to shift due to wear. Therefore, it is necessary to solve or reduce the wear problem from the material point of view, so as to further optimize the bearing and its dual components to solve the problem of "sweeping the bore" in the turbine after long-term use. Experimental analysis was carried out, referring to Figure 3 , specifically including the following steps:

[0075] A1. According to the above, the finite element modeling analysis of the bearing and its counterpart in the wheel operating mechanism is performed to determine the wear pair position between the bearing and its counterpart;

[0076] A2. Collect actual workpiece samples at the corresponding positions of the wear pairs, observe and analyze the samples, and determine the wear forms between different wear pairs;

[0077] A3. Collect the information on the materials used for domestic turbine bearings and their counterparts, and propose a preliminary material optimization plan for bearings and their counterparts based on the wear forms of different wear pairs;

[0078] A4. Conduct optimal friction tests on the optimization scheme to determine the optimal material combination of the bearing and the dual component in different material optimization schemes;

[0079] A5. Based on the actual working conditions, without changing the blade pivot material in the dual component, the preferred material combination of the bearing and the dual component is screened again to obtain the final optimized material combination that can be used to replace the bearing and its dual component.

[0080] Among them, the dual components in A1 are the same as those in the above-mentioned theoretical analysis part. In this embodiment, the dual components include a blade pivot and a swing arm. It can be known from the theoretical analysis part that the basic pressure of the bearing is mainly concentrated on the contact part of the blade pivot at the end, and the stress distribution of the swing arm is concentrated on the end face of the swing arm bearing. Therefore, the bearing produces two wear pairs: the friction between the thrust surface of the bearing and the end face of the swing arm, and the radial friction between the slurry pivot and the bearing.

[0081] After determining the good wear pair position, proceed to A2, refer to Figure 4 , and the observation analysis in A2 includes the following steps:

[0082] A21. Observe and analyze the macroscopic morphology of the sample and make a preliminary judgment on the cause of wear of the wear pair;

[0083] A22. Take metal samples from the samples, observe and analyze the metallographic microstructure of the samples, and verify the preliminary judgment results.

[0084] To be more specific, in A21, the macroscopic morphological observation of the sample includes observing the physical workpiece of the sample from the perspective of color, scratches, and wear position. The theoretical analysis of the existence of the friction pair is verified based on the darker color at the location with high compressive stress and the lighter color at the location with low compressive stress. At the same time, the first judgment of the wear form can be made on the wear position based on the color, scratches or pitting pits. It also includes scanning the wear surface morphological observation after scanning the wear surface of the workpiece sample. When scanning the morphological observation, it is necessary to conduct comparative observations of different viewing areas and different multiples at the same position, and make a second judgment on the wear form of the wear surface to verify the first judgment result observed by naked eyes, so as to determine the wear form of the wear pair and make a preliminary judgment. And the wear forms include adhesive wear, abrasive wear, fatigue wear, corrosive wear and micro-motion wear. In actual wear phenomena, several forms of wear usually exist at the same time, and one form of wear often induces other forms of wear. For example, the wear debris of fatigue wear will cause abrasive wear, and the clean surface formed by abrasive wear will cause corrosion or adhesive wear.

[0085] In A22, metal sampling of samples includes metal sampling of the corresponding wear surfaces of the bearing and its mating component, as well as metal sampling away from the wear surface. Metal samples at different positions of the same component are compared and analyzed in the metallographic microstructure observation to further judge the friction form and verify the preliminary judgment in A21.

[0086] In some embodiments, in step A2, it is necessary to collect samples of lubricating oil in the runner of the turbine and test the oil samples to check whether the lubricating oil contains excessive, large or abnormal wear debris. If necessary, the wear debris is analyzed to comprehensively analyze the wear form. Determining the wear form of the wear pair can provide a basis for material optimization. Since different materials have different wear amounts under the same wear form, for different wear forms of each group of wear pairs, materials with less wear amounts under the same wear form are preferably used as the optimized materials for the bearing and its counterpart, which provides a reference for the formulation of the optimized materials in S3.

[0087] In A3, the information on the materials used for the bearings and their counterparts of domestic turbines is collected, and various materials are compared and analyzed. It is known that, limited by the design, manufacturing level and economic conditions at that time, the early design of the propeller-type unit runner blade pivot material is mostly carbon steel (ZG20SiMn or ZG35). In order to ensure that the pivot is not worn as much as possible during the operation of the unit, the corresponding bearing material is basically made of tin bronze (phosphor bronze) with relatively low material hardness. With the advancement of technology, the quality of the pivot material has been improved, and the pivot material has been changed from carbon steel to stainless steel or alloy steel. At present, the propeller pivot material of the propeller-type unit in the industry is basically ZG06Cr13Ni5Mo or ZG35Cr1Mo. With the improvement of the performance of the pivot material, the bearing material has also been changed from tin bronze to aluminum bronze.

[0088] The optimization scheme needs to use a material scheme with a hardness difference. According to the selection of bearing materials in the above-mentioned industry, aluminum bronze is used as the material of the current sample bearing in this embodiment. The optimized material scheme for bricks and tiles in A3 is any one of aluminum brass, OI LES self-lubricating copper, and powder metallurgy. The optimized material scheme for the bearing dual component is any one of ZG20SiMn, ZG35Cr1Mo, forged steel 34CrNi3Mo, and ZG06Cr13Ni5Mo. In order to compare with the existing bearing materials, when conducting the optimization test for the optimization scheme in A4, a control benchmark group test material with the same material as the current bearing is added. That is, when conducting A4, the candidate test materials for the bearing are aluminum bronze, aluminum brass, OI LES self-lubricating copper, and powder metallurgy.

[0089] Before conducting the preferred friction test, the friction test blocks used to simulate the bearing and its counterpart are grouped for testing. One friction test block simulating the bearing corresponds to a friction test block of a counterpart of each selected material. In each group, the friction test blocks simulating the bearing and the friction test blocks simulating the counterpart are tested one by one.

[0090] When conducting A4, the friction test is preferably conducted using a thrust and high-load shaft diameter friction tester. The current bearing material and the material of each proposed replacement are made into friction test blocks, and friction tests are conducted separately. The friction test includes thrust friction test and radial friction test to obtain the material ranking of the corresponding dual components for each bearing material. When conducting the optimal friction test, the analysis direction includes the influence of friction temperature, wear amount and friction coefficient on wear.

[0091] Four bearing materials and four mating shaft materials were selected, and friction tests were carried out on them in the axial and radial directions under the designed load. The following data were collected during the experiment: friction coefficient, bearing temperature, dimensional change of the maximum wear part before and after the test, wear amount, and the wear parts of the bearing and mating materials were photographed to record the wear appearance. Comprehensive analysis of the obtained data can determine which friction couple has less wear and which bearing material or shaft material performs well.

[0092] In A5, a material solution with a certain hardness difference is selected according to the material of the blade pivot in the turbine, and the material with a certain hardness difference needs to ensure that the blade pivot is not worn when the bearing is worn. Therefore, the test results of each group in A4 are compared, analyzed and screened according to the material of the blade pivot to obtain the final material optimization solution. In order to ensure the feasibility and reliability of the preferred solution, a verification friction test is carried out on the final material optimization combination. The verification friction test is the same as the preferred friction test method, and the test time of the verification friction test is greater than the test time of the preferred friction test, that is, the radial test time and the thrust test time are extended, and the wear degree of the friction test corresponding to the bearing and its dual component in the optimization solution is compared with the wear degree of the actual sample, thereby proving the feasibility and reliability of the preferred solution.

[0093] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0094] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0095] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for optimizing the structure of a turbine blade bearing and its counterpart, characterized in that: The following steps are involved: S1. Perform force analysis on the bearing and blade pivot in the runner mechanism to obtain the support reaction force acting on the blade pivot when the blade is in the rotating state and the stopped state under the maximum water head condition; S2. According to different working conditions, finite element simulation modeling is carried out in combination with two groups of support reaction forces, and finite element analysis of different parts of the bearing is carried out on the finite element modeling in combination with the maximum head working condition and the rated head working condition, and the analysis results of the bearing contact pressure under different working conditions are obtained. According to the analysis results, it is concluded that the cause of bearing wear is excessive end face contact pressure; S3. Use analytical methods to analyze the bearing force and calculate the bearing contact pressure to obtain the bearing contact pressure under various working conditions, and compare the calculation results with the finite element analysis results to verify whether the bearing wear cause obtained in the finite element analysis is correct; S4. Propose an optimization plan based on the bearing wear causes obtained through finite element analysis and the analytical verification results, adjust the bearing structure specifications, increase the outer diameter of the bearing and its counterpart, and conduct finite element analysis and analytical verification of the optimization plan under various working conditions again to verify the feasibility of the optimization plan; After the force analysis of the bearing and slurry pivot in S1, the water moment and water thrust of the blade pivot in the wheel mechanism are calculated to obtain the maximum water head and minimum water head of the blade pivot in the working state, and the minimum operating oil pressure of the wheel mechanism is calculated based on the maximum water head and the minimum water head to obtain the maximum support reaction force acting on the lower blade pivot under the maximum water head condition and the minimum support reaction force acting on the blade pivot under the minimum water head condition.

2. A method for optimizing the structure of a turbine blade bearing and its counterpart according to claim 1, characterized in that: In S2, both the bearing and the impeller are modeled during the finite element analysis, and when modeling the impeller, the analysis model established according to the periodic symmetry of the impeller is a period of the impeller including one blade, and periodic symmetric boundary conditions are applied to the section surface to constrain the circumferential degrees of freedom of the nodes at the blade pivot connecting rod; a contact unit is used at the contact between the impeller pivot and the bearing.

3. A method for optimizing the structure of a turbine blade bearing and its counterpart as claimed in claim 2, characterized in that: In S2, when simulating working conditions using the finite element method, it is necessary to simulate the working conditions of rated head, rated output, and maximum head, rated output.

4. A method for optimizing the structure of a turbine blade bearing and its counterpart as claimed in claim 3, characterized in that: In S2, the finite element analysis of the bearing includes the analysis of the end face contact stress of the bearing and the analysis of the radial contact stress of the bearing, and the finite element analysis of the end face contact pressure and the radial contact pressure of the bearing are respectively performed under the conditions of rated head and rated output and the conditions of maximum head and rated output to obtain the analysis results of the end face contact pressure of the bearing and the radial contact pressure of the bearing under different working conditions.

5. A method for optimizing the structure of a turbine blade bearing and its counterpart as claimed in claim 4, characterized in that: In S2, the constraint input of the edge contact pressure factor is added in the finite element analysis process, and the finite element analysis is performed again on the bearing end face contact pressure and the radial contact pressure under the conditions of rated head and rated output and maximum head and rated output, so as to obtain the results of the bearing end face contact pressure and the bearing radial contact pressure under different working conditions when the influence of the edge contact pressure factor is considered, so as to determine the influence of the edge contact pressure on the bearing end face contact pressure and the radial contact pressure.

6. A method for optimizing the structure of a turbine blade bearing and its counterpart as claimed in claim 3, characterized in that: In the S2 analysis, the bearing is subjected to deformation distribution finite element analysis to simulate and observe the deformation position of the bearing. The deformation distribution finite element analysis includes: The radial deformation distribution of the bearing and the deformation distribution of the bearing end face under the rated head and rated output conditions; The radial deformation distribution of the bearing and the deformation distribution of the bearing end face under the conditions of maximum head and rated output; The radial deformation distribution of the bearing under rated head and rated output conditions and the radial deformation distribution of the bearing; The radial deformation distribution of the bearing under the maximum head and rated output conditions and the radial deformation distribution of the bearing.

7. The method for optimizing the structure of a turbine blade bearing and its counterpart according to claim 1, characterized in that: When verifying the optimization plan, the optimization plan is verified by finite element analysis and analytical calculation according to steps S2 and S3 to determine the feasibility of the optimization plan.

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