WO2024066170A1 - Three-dimensional calculation system and calculation method for blade dynamic stress of steam turbine under ultra-low load - Google Patents

Three-dimensional calculation system and calculation method for blade dynamic stress of steam turbine under ultra-low load Download PDF

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WO2024066170A1
WO2024066170A1 PCT/CN2023/076899 CN2023076899W WO2024066170A1 WO 2024066170 A1 WO2024066170 A1 WO 2024066170A1 CN 2023076899 W CN2023076899 W CN 2023076899W WO 2024066170 A1 WO2024066170 A1 WO 2024066170A1
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blade
calculation
dynamic stress
flow field
module
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PCT/CN2023/076899
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French (fr)
Chinese (zh)
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关淳
张勇
马义良
赵洪羽
梁天赋
郭魁俊
翁振宇
祝海义
李宇峰
赫广迅
徐林峰
刘鑫
余海鹏
孙嘉
薛海亮
潘劭平
初世明
尉坤
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哈电发电设备国家工程研究中心有限公司
哈尔滨汽轮机厂有限责任公司
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Publication of WO2024066170A1 publication Critical patent/WO2024066170A1/en

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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • G06F30/23—Design optimisation, verification or simulation using finite element methods [FEM] or finite difference methods [FDM]
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • G06F30/28—Design optimisation, verification or simulation using fluid dynamics, e.g. using Navier-Stokes equations or computational fluid dynamics [CFD]
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T17/00—Three dimensional [3D] modelling, e.g. data description of 3D objects
    • G06T17/20—Finite element generation, e.g. wire-frame surface description, tesselation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2113/00—Details relating to the application field
    • G06F2113/08—Fluids
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
    • G06F2119/14—Force analysis or force optimisation, e.g. static or dynamic forces

Definitions

  • the invention relates to a system and method for calculating dynamic stress of a super-low-load blade of a steam turbine, and belongs to the technical field of blade dynamic stress prediction.
  • the three-dimensional simulation calculation and assessment methods of blade dynamic stress in the industry are mainly aimed at blade harmonic vibration, and the excitation factor is related to the harmonic number.
  • the excitation factor is related to the harmonic number.
  • the blade vibration characteristics under ultra-low load and turbulent flow field it is usually a random vibration caused by eddy current effect, which has nothing to do with harmonic vibration. It should start from the flow field characteristics, extract and analyze the exciting force, and then use it to calculate the blade dynamic stress.
  • the present invention provides a three-dimensional calculation method for the dynamic stress of a steam turbine blade under ultra-low load.
  • the present invention is developed to solve the problem of calculating the dynamic stress of the blade under ultra-low load conditions.
  • a brief overview of the present invention is given below to provide a basic understanding of certain aspects of the present invention. It should be understood that this overview is not an exhaustive overview of the present invention. It is not intended to determine the key or important parts of the present invention, nor is it intended to limit the scope of the present invention.
  • the three-dimensional calculation system for dynamic stress of ultra-low-load blades of steam turbines includes a thermal boundary calculation module, a blade three-dimensional flow field calculation module, a blade finite element calculation module and a blade dynamic stress calculation module;
  • Thermal boundary calculation module used to obtain thermal data of blade inlet and outlet flow, total enthalpy and pressure, and provide thermal boundary for blade three-dimensional flow field calculation;
  • Blade three-dimensional flow field calculation module used to obtain blade steady-state and transient flow field calculation results, and to calculate the blade structure field static state. Provide input data for stress and dynamic stress calculations;
  • the blade three-dimensional flow field calculation module includes: blade flow field calculation domain modeling module, steady-state flow field calculation module and transient flow field calculation module;
  • Blade finite element calculation module used to obtain the calculation results of blade static stress and resonance frequency, and provide input data for blade dynamic stress calculation
  • the blade finite element calculation module includes: blade structure field calculation domain modeling module, blade static stress calculation module and blade resonance frequency calculation module;
  • Blade dynamic stress calculation module used to obtain blade dynamic stress calculation results and provide data for the blade dynamic stress assessment module.
  • it also includes a blade dynamic stress assessment module: used to evaluate and assess the blade dynamic stress safety and guide the blade optimization design.
  • a blade dynamic stress assessment module used to evaluate and assess the blade dynamic stress safety and guide the blade optimization design.
  • the three-dimensional calculation method of dynamic stress of ultra-low load blades of steam turbine includes the following steps:
  • Step 1 Thermal boundary calculation: Using the thermal boundary calculation module, for the target blade, a thermal calculation program is used to obtain the thermal boundary of the blade under different load conditions of the turbine, and the blade inlet flow, total enthalpy value, outlet pressure and temperature values are extracted as the input boundary for the blade three-dimensional flow field calculation;
  • Step 2 blade three-dimensional flow field calculation; using the blade three-dimensional flow field calculation module, first use the blade flow field calculation domain modeling module to perform blade flow field calculation domain modeling, then use the steady-state flow field calculation module to perform steady-state calculation of the blade flow field, and finally use the transient flow field calculation module to perform transient calculation of the blade flow field;
  • Step 3 blade finite element calculation; using the blade finite element calculation module, first use the blade structure field calculation domain modeling module to perform blade structure field calculation domain modeling, then use the blade static stress calculation module to perform blade static stress calculation, and finally use the blade resonance frequency calculation module to perform blade resonance frequency calculation;
  • Step 4 Blade dynamic stress calculation, using blade dynamic stress calculation module.
  • the thermal boundary of the blade includes typical ultra-low load operating points of 5%, 10%, 15%, 20%, 25% and 30%.
  • blade flow field calculation domain modeling CFD calculation software is used to establish a blade three-dimensional flow field calculation domain model, the blade is meshed, the number of mesh nodes meets the mesh independence requirement, the calculation domain uses the static blade inlet as the calculation domain inlet, the inlet flow rate and total enthalpy value are given, and the moving blade outlet is the calculation domain outlet, the outlet pressure and temperature are given; the static blade calculation domain is stationary, the moving blade calculation domain is rotating, the rotation speed is the turbine operating speed, the cyclic symmetry method is used for simulation, and the calculation domain working fluid uses water vapor;
  • Steady-state calculation of blade flow field using steady-state CFD calculation mode, obtain steady-state results of blade flow field at blade thermal boundary, master the distribution characteristics of flow field separation and flow separation, and use the result file of steady-state CFD calculation as the input file of transient flow field calculation, and use the blade surface pressure data of steady-state CFD calculation as the input file of structural field finite element static stress calculation;
  • the transient calculation of the blade flow field adopts the transient CFD calculation mode.
  • the statistical parameters of the steam pressure on the blade surface are calculated to obtain the transient results of the blade flow field at the blade thermal boundary, extract the mean square error of the steam pressure at each node on the blade surface, and compile the exciting force input file of the dynamic stress calculation module.
  • the exciting force input file format is csv format, with a total of four columns of data. The first three columns are the coordinates of the nodes in the x, y, and z directions, and the fourth column is the mean square error of the steam pressure.
  • the blade structure field calculation domain modeling using finite element calculation software, the blade structure field model is established, the blade structure field model includes the blade and the wheel groove, the blade root is connected to the wheel groove, the blade structure field model is meshed, the calculation domain includes all the structural features of the blade, and its structural features include the shroud at the end of the blade, the ribs in the middle of the blade, and the blade Frictional contact is set between the blade body and the blade root at the end of the blade, between adjacent shrouds and between the tie bars; a friction base is set between the blade root and the wheel groove, and the cyclic symmetry method is used for simulation.
  • the wheel groove is a fixed constraint, and the rotation speed of the moving blade and the wheel groove is the working speed of the steam turbine to simulate the centrifugal force.
  • Blade static stress calculation Based on the blade structure field model, the blade surface pressure result of the blade flow field steady-state calculation of the steady-state flow field calculation module is used as the static stress calculation input file, the steam force is simulated, the blade static stress is calculated, the blade static stress distribution characteristics are obtained, and the static stress calculation result is used as the input data of the blade dynamic stress assessment module;
  • Blade resonance frequency calculation Based on the blade structure field model, the blade resonance frequency is calculated to obtain the first two orders of blade resonance frequencies at the turbine operating speed, and the resonance frequency results are used as the input of the blade dynamic stress calculation module.
  • step four based on the blade structure field model, the mean square error of the blade surface pressure calculated by the transient flow field calculation module of the transient flow field calculation module is used as the exciting force input file, and the resonance frequency corresponding to the resonance mode closest to the working speed calculated by the blade resonance frequency calculation module of the blade resonance frequency is used as the input file, the blade dynamic stress is calculated, the blade dynamic stress distribution characteristics are obtained, and the dynamic stress calculation results are used as input data for the blade dynamic stress assessment module.
  • the method further comprises step five: blade dynamic stress assessment, using a blade dynamic stress assessment module.
  • a blade dynamic stress assessment table is prepared
  • the second column “Blade Height” of the assessment table refers to the blade height of the blade, in mm;
  • the third column “Operating Condition” of the assessment table refers to the calculated ultra-low load operating point;
  • the "Assessment Position” given in the assessment table the assessment position is divided into blade body assessment and blade root assessment, the blade body assessment is divided into assessment position A and assessment position B, the blade root assessment is divided into assessment position C and assessment position D;
  • the allowable value of dynamic stress given in the assessment table refers to the maximum value of the blade dynamic stress that meets the design safety requirements
  • the process of obtaining the dynamic stress allowable value is as follows: based on the GOODMAN test curve of the blade material, taking the static stress data as input, querying the vibration resistance of the material, and calculating the dynamic stress allowable value based on the safety factor specified by the manufacturer;
  • the safety criterion for blade dynamic stress assessment is: the dynamic stress at the blade body and blade root assessment position ⁇ the allowable value of dynamic stress. When the assessment fails, it is necessary to increase the blade damping, blade rigidity or improve the blade material grade to optimize the blade design to ensure that the blade dynamic stress assessment passes.
  • the present invention is applicable to blade vibration characteristics under ultra-low load and turbulent flow fields, which are usually random vibrations caused by eddy current effects. Starting from the flow field characteristics, the exciting force is extracted and analyzed, thereby realizing the calculation of blade dynamic stress.
  • the present invention extracts the flow field pulsating pressure as the exciting force for blade dynamic stress calculation. Compared with the current two-way fluid-solid coupling calculation method, it can significantly reduce the dependence on computer resources and reduce the calculation time, and is suitable for engineering applications.
  • the effectiveness of the algorithm of the present invention has been verified through a blade dynamic stress test.
  • the deviation between the calculated value of the present invention and the test value is about 13.6%, which meets the requirements of engineering application.
  • FIG1 is a framework diagram of a three-dimensional calculation method for dynamic stress of a steam turbine ultra-low load blade
  • FIG2 is a schematic diagram of blade flow field calculation domain modeling
  • Figure 3 is the calculation result of the steady-state flow field of the blade under low load condition (taking 15% as an example);
  • FIG. 4 is a schematic diagram of the blade structure.
  • the connection mentioned in the present invention is divided into fixed connection and detachable connection.
  • the fixed connection is a non-detachable connection including but not limited to conventional fixed connection methods such as folding connection, rivet connection, bonding connection and welding connection.
  • the detachable connection includes but not limited to conventional detachable methods such as threaded connection, snap connection, pin connection and hinge connection.
  • a fixed connection is a welding connection
  • a detachable connection is a hinge connection.
  • the three-dimensional calculation system for dynamic stress of ultra-low-load blades of a steam turbine in this implementation method includes a thermal boundary calculation module, a blade three-dimensional flow field calculation module, a blade finite element calculation module and a blade dynamic stress calculation module;
  • Thermal boundary calculation module used to obtain thermal data of blade inlet and outlet flow, total enthalpy and pressure, and provide thermal boundary for blade three-dimensional flow field calculation;
  • Blade three-dimensional flow field calculation module used to obtain blade steady-state and transient flow field calculation results, and provide input data for blade structure field static stress and dynamic stress calculation;
  • the blade three-dimensional flow field calculation module includes: blade flow field calculation domain modeling module 2.1, steady-state flow field calculation module 2.2 and transient flow field calculation module 2.3;
  • Blade finite element calculation module used to obtain the calculation results of blade static stress and resonance frequency, and provide input data for blade dynamic stress calculation
  • the blade finite element calculation module includes: a blade structure field calculation domain modeling module 3.1, a blade static stress calculation module 3.2 and a blade resonance frequency calculation module 3.3;
  • Blade dynamic stress calculation module used to obtain blade dynamic stress calculation results and provide data for blade dynamic stress assessment module;
  • This implementation method is described in conjunction with Figures 1 to 4.
  • This implementation method is a three-dimensional calculation method for dynamic stress of ultra-low load blades of a steam turbine, including a thermal boundary calculation module, a blade three-dimensional flow field calculation module, a blade finite element calculation module and a blade dynamic stress calculation module;
  • Thermal boundary calculation module used to obtain thermal data of blade inlet and outlet flow, total enthalpy and pressure, and provide thermal boundary for blade three-dimensional flow field calculation;
  • Blade three-dimensional flow field calculation module used to obtain blade steady-state and transient flow field calculation results, and to calculate the blade structure field static state. Provide input data for stress and dynamic stress calculations;
  • the blade three-dimensional flow field calculation module includes: blade flow field calculation domain modeling module 2.1, steady-state flow field calculation module 2.2 and transient flow field calculation module 2.3;
  • Blade finite element calculation module used to obtain the calculation results of blade static stress and resonance frequency, and provide input data for blade dynamic stress calculation
  • the blade finite element calculation module includes: a blade structure field calculation domain modeling module 3.1, a blade static stress calculation module 3.2 and a blade resonance frequency calculation module 3.3;
  • Blade dynamic stress calculation module used to obtain blade dynamic stress calculation results and provide data for blade dynamic stress assessment module;
  • blade dynamic stress assessment module used to evaluate and assess the blade dynamic stress safety and guide blade optimization design
  • Step 1 Combined with Figure 1, thermal boundary calculation; using the thermal boundary calculation module, for the target blade, use the thermal calculation program to obtain the thermal boundary of the blade under different load conditions of the turbine, extract the blade inlet flow, total enthalpy value, outlet pressure and temperature value as the input boundary of the blade three-dimensional flow field calculation;
  • the thermal boundary of the blade includes typical ultra-low load operating points such as 5%, 10%, 15%, 20%, 25%, and 30%;
  • Step 2 blade three-dimensional flow field calculation; using the blade three-dimensional flow field calculation module, first use the blade flow field calculation domain modeling module 2.1 to perform blade flow field calculation domain modeling, then use the steady-state flow field calculation module 2.2 to perform steady-state calculation of the blade flow field, and finally use the transient flow field calculation module 2.3 to perform transient calculation of the blade flow field;
  • the blade flow field calculation domain modeling CFD calculation software is used to establish a blade three-dimensional flow field calculation domain model.
  • the blade consists of a stationary blade 1 and a moving blade 2.
  • the stationary blade 1 is connected to the moving blade 2.
  • the stationary blade side has a stationary blade inlet 3 and the moving blade side has a moving blade outlet 4.
  • the blade is meshed, and the number of grid nodes meets the grid independence requirement.
  • the calculation domain uses the stationary blade inlet as the calculation domain inlet, and the inlet flow rate and total enthalpy value are given.
  • the moving blade outlet is the calculation domain outlet, and the outlet pressure and temperature are given; the stationary blade calculation domain is stationary, and the moving blade calculation domain is rotating.
  • the rotation speed is the turbine operating speed (3000r/mim).
  • the cyclic symmetry method is used for simulation, and the cyclic symmetry boundary can be automatically generated by the CFD calculation software.
  • the calculation domain working fluid uses water vapor.
  • the water vapor physical property data comes from the NIST library and can be called by the CFD calculation software.
  • the blade flow field steady-state calculation using the steady-state CFD calculation mode, obtain the blade flow field steady-state results of the blade thermal boundary, master the flow field separation, the distribution characteristics of the flow separation, and the steady-state CFD calculation result file as the input file for the transient flow field calculation, and the blade surface pressure data calculated by the steady-state CFD as the input file for the structural field finite element static stress calculation;
  • the transient calculation of the blade flow field adopts the transient CFD calculation mode.
  • the statistical parameters of the steam pressure on the blade surface are calculated.
  • the statistical parameters include the pressure average value, mean square error value, maximum value, and minimum value within the calculation period.
  • the transient results of the blade flow field at the thermal boundary of the blade are obtained, and the mean square error value of the steam pressure at each node on the blade surface is extracted.
  • the excitation force input file of the dynamic stress calculation module is compiled.
  • the excitation force input file format is csv format, with a total of four columns of data. The first three columns are the coordinates of the nodes in the x, y, and z directions, and the fourth column is the mean square error value of the steam pressure.
  • step three blade finite element calculation; using the blade finite element calculation module, first use the blade structure field calculation domain modeling module 3.1 to perform blade structure field calculation domain modeling, then use the blade static stress calculation module 3.2 to perform blade static stress calculation, and finally use the blade resonance frequency calculation module 3.3 to perform blade resonance frequency calculation;
  • blade structure field calculation domain modeling finite element calculation software is used to establish the blade structure field model.
  • the blade structure field model includes blades and wheel grooves 5.
  • the blade root 6 is connected to the wheel groove 5.
  • the blade structure field model is meshed.
  • the calculation domain includes all the structural features of the blade, including the shroud 8 at the end of the blade, the tie rod 7 in the middle of the blade, the blade body of the blade and the blade root 6 at the end of the blade. Friction contact is set between adjacent shrouds 8 and tie rods 7, and the friction coefficient is 0.2; a friction base is set between the blade root 6 and the wheel groove 5, and the friction coefficient is 0.25.
  • the cyclic symmetry method is used for simulation.
  • the cyclic symmetry boundary is usually the periodic surface of the shroud and the wheel groove.
  • the wheel groove is a fixed constraint.
  • the rotation speed of the moving blade and the wheel groove is the working speed of the steam turbine (3000r/mim).
  • the centrifugal force is simulated.
  • the moving blade and the wheel groove material is derived from the material test data, mainly including elastic modulus, Poisson's ratio, and density.
  • Blade structure field calculation domain modeling When meshing the blade structure field model, the mesh is encrypted at the rounding of the moving blades, the rounding of the moving blades in and out, and the rounding of the wheel groove to ensure the calculation accuracy;
  • Blade static stress calculation Based on the blade structure field model, the blade surface pressure result of the blade flow field steady-state calculation of the steady-state flow field calculation module 2.2 is used as the static stress calculation input file, the steam force is simulated, the blade static stress is calculated, the blade static stress distribution characteristics are obtained, and the static stress calculation result is used as the input data of the blade dynamic stress assessment module;
  • Blade resonance frequency calculation Based on the blade structure field model, the blade resonance frequency is calculated to obtain the first two-order blade resonance frequencies at the turbine operating speed (3000r/min), and the resonance frequency results are used as the input of the blade dynamic stress calculation module;
  • Step 4 Blade dynamic stress calculation, using blade dynamic stress calculation module
  • step 4 based on the blade structure field model, the mean square error of the blade surface pressure calculated by the transient flow field calculation module 2.3 is used as the exciting force input file, and the resonance frequency corresponding to the resonance mode closest to the working speed (3000r/min) calculated by the blade resonance frequency calculation module 3.3 is used as the input file to calculate the blade dynamic stress, obtain the blade dynamic stress distribution characteristics, and use the dynamic stress calculation result as the input data of the blade dynamic stress assessment module;
  • step 5 blade dynamic stress assessment (monitoring), using a blade dynamic stress assessment module
  • step 5 prepare the blade dynamic stress assessment table, as shown in Table 1:
  • the second column “Blade Height” of the assessment table refers to the blade height of the blade, in mm;
  • the third column “Operating Condition” of the assessment table refers to the calculated ultra-low load operating point;
  • the "Assessment Position” given in the assessment table the assessment position is divided into blade body assessment and blade root assessment, the blade body assessment is divided into assessment position A and assessment position B, the blade root assessment is divided into assessment position C and assessment position D;
  • the assessment position A refers to the peak position of the static stress of the blade body; the static stress peak is extracted from the blade static stress calculation of the blade static stress calculation module 3.2; the dynamic stress value includes the first-order resonance assessment point and the second-order resonance assessment point; the resonance assessment point refers to the distance from the working speed calculated by the blade resonance frequency calculation module 3.3 (3000r/min) the nearest resonance mode; the dynamic stress values of the 1st order resonance test point and the 2nd order resonance test point are extracted from the blade dynamic stress calculation;
  • the assessment position B refers to the peak position of the dynamic stress of the blade body; the dynamic stress peak position includes the 1st-order resonance assessment point and the 2nd-order resonance assessment point; the resonance assessment point refers to the resonance mode closest to the working speed (3000r/min) calculated by the blade resonance frequency calculation of the blade resonance frequency calculation module 3.3; the dynamic stress peak values of the 1st-order resonance assessment point and the 2nd-order resonance assessment point are extracted from the blade dynamic stress calculation; the 1st-order and 2nd-order static stress values are extracted from the blade static stress calculation of the blade static stress calculation module 3.2.
  • the assessment position C refers to the peak position of the static stress at the blade root; the static stress peak is extracted from the blade static stress calculation module 3.2; the dynamic stress value includes the 1st order resonance assessment point and the 2nd order resonance assessment point; the resonance assessment point refers to the resonance mode closest to the working speed (3000r/min) calculated by the blade resonance frequency calculation module 3.3; the dynamic stress values of the 1st order resonance assessment point and the 2nd order resonance assessment point are extracted from the blade dynamic stress calculation module;
  • the assessment position D refers to the peak position of the dynamic stress at the blade root; the dynamic stress peak position includes the 1st order resonance assessment point and the 2nd order resonance assessment point; the resonance assessment point refers to the resonance mode closest to the working speed (3000r/min) calculated by the blade resonance frequency calculation module 3.3; the dynamic stress peak values of the 1st order resonance assessment point and the 2nd order resonance assessment point are extracted from the blade dynamic stress calculation module; the 1st order and 2nd order static stress values are extracted from the blade static stress calculation module of the blade static stress calculation module 3.2;
  • the allowable value of dynamic stress given in the assessment table refers to the maximum value of the blade dynamic stress that meets the design safety requirements
  • the process of obtaining the dynamic stress allowable value is as follows: based on the GOODMAN test curve of the blade material, taking the static stress data as input, querying the vibration resistance of the material, and calculating the dynamic stress allowable value based on the safety factor specified by the manufacturer;
  • the safety criterion for blade dynamic stress assessment is: the dynamic stress at the blade body and blade root assessment position is ⁇ the allowable value of dynamic stress. If the assessment fails, the blade damping, blade rigidity or blade material grade should be increased to optimize the blade design to ensure that the blade dynamic stress assessment passes.
  • the present invention is applicable to the calculation of blade dynamic stress under the ultra-low load operation condition of a steam turbine, and provides a technical means for the prediction and assessment of blade dynamic stress.

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Abstract

The present invention relates to the technical field of blade dynamic stress prediction, and relates to a three-dimensional calculation system and calculation method for blade dynamic stress of a steam turbine under an ultra-low load. The problem of blade dynamic stress calculation under an ultra-low load working condition is solved. The system comprises a thermal boundary calculation module, a blade three-dimensional flow field calculation module, a blade finite element calculation module, and a blade dynamic stress calculation module; the thermal boundary calculation module is configured to obtain thermal data of blade inlet and outlet flow, total enthalpy, and pressure and provide a thermal boundary for calculation of a blade three-dimensional flow field; the blade three-dimensional flow field calculation module is configured to obtain blade steady-state and transient-state flow field calculation results and provide input data for static stress and dynamic stress calculation of a blade structure field; the blade finite element calculation module is configured to obtain calculation results of blade static stress and resonance frequency and provide input data for blade dynamic stress calculation; and the blade dynamic stress calculation module is configured to obtain a blade dynamic stress calculation result and provide data for a blade dynamic stress assessment module.

Description

汽轮机超低负荷叶片动应力三维计算系统及其计算方法Three-dimensional calculation system and calculation method for dynamic stress of steam turbine blades under ultra-low load 技术领域Technical Field
本发明涉及汽轮机超低负荷叶片动应力计算系统及其计算方法，属于叶片动应力预测技术领域。The invention relates to a system and method for calculating dynamic stress of a super-low-load blade of a steam turbine, and belongs to the technical field of blade dynamic stress prediction.
背景技术Background technique
全球能源格局正在由依赖传统化石能源向增加、推广清洁高效能源的方向发展。风电、光电等为代表的新能源有利于减碳，但易受自然环境等因素影响，具有明显的波动、间歇、不稳定等属性。国内外实践证明，新能源大幅增长的同时必需增强与之协同且匹配的灵活、稳定、可调度电源作为支撑。中国的能源资源禀赋决定了安全可靠的燃煤电站将在相当长的时间内发挥关键作用。本着“兜底保供”这一原则，攻克电站主设备全工况灵活性运行关键技术难题势在必行。The global energy landscape is developing from reliance on traditional fossil energy to increasing and promoting clean and efficient energy. New energy represented by wind power and photovoltaic power is conducive to carbon reduction, but it is easily affected by factors such as the natural environment and has obvious fluctuations, intermittent, and unstable properties. Domestic and foreign practices have proved that while new energy sources are growing substantially, it is necessary to strengthen the support of flexible, stable, and dispatchable power sources that coordinate and match them. China's energy resource endowment determines that safe and reliable coal-fired power plants will play a key role for a considerable period of time. Based on the principle of "guaranteeing the bottom line and ensuring supply", it is imperative to overcome the key technical difficulties of flexible operation of the main equipment of the power station under all working conditions.
国内外相关企业大量的技术开发和工程实践表明，当代大型汽轮机全工况灵活运行的关键技术应聚焦在低压通流部分，特别是末级长叶片，其开发和研制水平是综合技术能力的重要标志。机组长期低负荷、变工况运行，低压模块中的长叶片将不可避免地伴随涡流激振响应，导致叶片动应力存在波动、高值区域难以确定。而叶片动应力试验测试成本高昂，且试验条件苛刻，很难实现，不利于汽轮机长叶片超低负荷运行安全性的考核和评估。为此，需要提出一种适用于汽轮机超低负荷运行工况下的叶片动应力计算方法，为叶片动应力评价提供技术手段。A large amount of technical development and engineering practice of related enterprises at home and abroad have shown that the key technology for flexible operation of contemporary large steam turbines under all working conditions should focus on the low-pressure flow part, especially the long blades of the last stage. Its development and research level is an important indicator of comprehensive technical capabilities. When the unit operates at low load and variable conditions for a long time, the long blades in the low-pressure module will inevitably be accompanied by vortex excitation response, resulting in fluctuations in blade dynamic stress and difficulty in determining the high-value area. However, the blade dynamic stress test is costly and the test conditions are harsh, which is difficult to achieve, and is not conducive to the assessment and evaluation of the safety of ultra-low load operation of long blades of steam turbines. To this end, it is necessary to propose a blade dynamic stress calculation method suitable for ultra-low load operation of steam turbines to provide technical means for blade dynamic stress evaluation.
目前行业内叶片动应力三维仿真计算和考核方法主要针对叶片谐波振动，激振因子与谐波数相关。对于超低负荷、紊乱流场下的叶片振动特征，通常属于涡流效应引起的随机振动，与谐波振动无关，应从流场特征入手，提取和分析激振力，从而用于叶片动应力的计算。但目前尚缺少有效的、针对于超低负荷工况的叶片动应力计算方法。At present, the three-dimensional simulation calculation and assessment methods of blade dynamic stress in the industry are mainly aimed at blade harmonic vibration, and the excitation factor is related to the harmonic number. For the blade vibration characteristics under ultra-low load and turbulent flow field, it is usually a random vibration caused by eddy current effect, which has nothing to do with harmonic vibration. It should start from the flow field characteristics, extract and analyze the exciting force, and then use it to calculate the blade dynamic stress. However, there is still a lack of effective blade dynamic stress calculation methods for ultra-low load conditions.
基于上述问题，亟需提出汽轮机超低负荷叶片动应力三维计算系统及其计算方法，以解决上述技术问题。Based on the above problems, it is urgent to propose a three-dimensional calculation system and calculation method for the dynamic stress of ultra-low load blades of steam turbines to solve the above technical problems.
发明内容Summary of the invention
本发明提供一种汽轮机超低负荷叶片动应力三维计算方法，本发明研发解决的是超低负荷工况下的叶片动应力计算的问题。在下文中给出了关于本发明的简要概述，以便提供关于本发明的某些方面的基本理解。应当理解，这个概述并不是关于本发明的穷举性概述。它并不是意图确定本发明的关键或重要部分，也不是意图限定本发明的范围。The present invention provides a three-dimensional calculation method for the dynamic stress of a steam turbine blade under ultra-low load. The present invention is developed to solve the problem of calculating the dynamic stress of the blade under ultra-low load conditions. A brief overview of the present invention is given below to provide a basic understanding of certain aspects of the present invention. It should be understood that this overview is not an exhaustive overview of the present invention. It is not intended to determine the key or important parts of the present invention, nor is it intended to limit the scope of the present invention.
本发明的技术方案：The technical solution of the present invention:
汽轮机超低负荷叶片动应力三维计算系统，包括热力边界计算模块、叶片三维流场计算模块、叶片有限元计算模块和叶片动应力计算模块；The three-dimensional calculation system for dynamic stress of ultra-low-load blades of steam turbines includes a thermal boundary calculation module, a blade three-dimensional flow field calculation module, a blade finite element calculation module and a blade dynamic stress calculation module;
热力边界计算模块：用于获得叶片进出口流量、总焓、压力的热力数据，为叶片三维流场计算提供热力边界；Thermal boundary calculation module: used to obtain thermal data of blade inlet and outlet flow, total enthalpy and pressure, and provide thermal boundary for blade three-dimensional flow field calculation;
叶片三维流场计算模块：用于获得叶片稳态、瞬态流场计算结果，为叶片结构场静 应力和动应力计算提供输入数据；Blade three-dimensional flow field calculation module: used to obtain blade steady-state and transient flow field calculation results, and to calculate the blade structure field static state. Provide input data for stress and dynamic stress calculations;
叶片三维流场计算模块包括：叶片流场计算域建模模块、稳态流场计算模块和瞬态流场计算模块；The blade three-dimensional flow field calculation module includes: blade flow field calculation domain modeling module, steady-state flow field calculation module and transient flow field calculation module;
叶片有限元计算模块：用于获得叶片静应力、共振频率的计算结果，为叶片动应力计算提供输入数据；Blade finite element calculation module: used to obtain the calculation results of blade static stress and resonance frequency, and provide input data for blade dynamic stress calculation;
叶片有限元计算模块包括：叶片结构场计算域建模模块、叶片静应力计算模块和叶片共振频率计算模块；The blade finite element calculation module includes: blade structure field calculation domain modeling module, blade static stress calculation module and blade resonance frequency calculation module;
叶片动应力计算模块：用于获得叶片动应力计算结果，为叶片动应力考核模块提供数据。Blade dynamic stress calculation module: used to obtain blade dynamic stress calculation results and provide data for the blade dynamic stress assessment module.
优选的：还包括叶片动应力考核模块：用于评估和考核叶片动应力安全性，指导叶片优化设计。Preferably: it also includes a blade dynamic stress assessment module: used to evaluate and assess the blade dynamic stress safety and guide the blade optimization design.
汽轮机超低负荷叶片动应力三维计算方法，包括以下步骤：The three-dimensional calculation method of dynamic stress of ultra-low load blades of steam turbine includes the following steps:
步骤一：热力边界计算；采用热力边界计算模块模块，针对目标叶片，采用热力计算程序获得汽轮机不同负荷条件下的叶片热力边界，提取叶片入口流量、总焓值、出口压力和温度值，作为叶片三维流场计算的输入边界；Step 1: Thermal boundary calculation: Using the thermal boundary calculation module, for the target blade, a thermal calculation program is used to obtain the thermal boundary of the blade under different load conditions of the turbine, and the blade inlet flow, total enthalpy value, outlet pressure and temperature values are extracted as the input boundary for the blade three-dimensional flow field calculation;
步骤二：叶片三维流场计算；采用叶片三维流场计算模块，首先采用叶片流场计算域建模模块进行叶片流场计算域建模，再次采用稳态流场计算模块进行叶片流场稳态计算，最后采用瞬态流场计算模块进行叶片流场瞬态计算；Step 2: blade three-dimensional flow field calculation; using the blade three-dimensional flow field calculation module, first use the blade flow field calculation domain modeling module to perform blade flow field calculation domain modeling, then use the steady-state flow field calculation module to perform steady-state calculation of the blade flow field, and finally use the transient flow field calculation module to perform transient calculation of the blade flow field;
步骤三：叶片有限元计算；采用叶片有限元计算模块，首先采用叶片结构场计算域建模模块进行叶片结构场计算域建模，再次采用叶片静应力计算模块进行叶片静应力计算，最后采用叶片共振频率计算模块进行叶片共振频率计算；Step 3: blade finite element calculation; using the blade finite element calculation module, first use the blade structure field calculation domain modeling module to perform blade structure field calculation domain modeling, then use the blade static stress calculation module to perform blade static stress calculation, and finally use the blade resonance frequency calculation module to perform blade resonance frequency calculation;
步骤四：叶片动应力计算，采用叶片动应力计算模块。Step 4: Blade dynamic stress calculation, using blade dynamic stress calculation module.
优选的：叶片热力边界包括5％、10％、15％、20％、25％、30％的典型超低负荷工况点。Preferably, the thermal boundary of the blade includes typical ultra-low load operating points of 5%, 10%, 15%, 20%, 25% and 30%.
优选的：步骤二中，叶片流场计算域建模：采用CFD计算软件，建立叶片三维流场计算域模型，对叶片进行网格划分，网格节点数量满足网格无关性要求，计算域以静叶片入口为计算域进口，给定进口流量和总焓值，以动叶片出口为计算域出口，给定出口压力和温度；静叶计算域为静止，动叶计算域为旋转，旋转速度为汽轮机工作转速，采用循环对称法模拟，计算域工质采用水蒸汽；Preferably: in step 2, blade flow field calculation domain modeling: CFD calculation software is used to establish a blade three-dimensional flow field calculation domain model, the blade is meshed, the number of mesh nodes meets the mesh independence requirement, the calculation domain uses the static blade inlet as the calculation domain inlet, the inlet flow rate and total enthalpy value are given, and the moving blade outlet is the calculation domain outlet, the outlet pressure and temperature are given; the static blade calculation domain is stationary, the moving blade calculation domain is rotating, the rotation speed is the turbine operating speed, the cyclic symmetry method is used for simulation, and the calculation domain working fluid uses water vapor;
叶片流场稳态计算，采用稳态CFD计算模式，获得叶片热力边界的叶片流场稳态结果，掌握流场分离、脱流的分布特征，并将稳态CFD计算的结果文件作为瞬态流场计算的输入文件，将稳态CFD计算的叶片表面压力数据作为结构场有限元静应力计算的输入文件；Steady-state calculation of blade flow field: using steady-state CFD calculation mode, obtain steady-state results of blade flow field at blade thermal boundary, master the distribution characteristics of flow field separation and flow separation, and use the result file of steady-state CFD calculation as the input file of transient flow field calculation, and use the blade surface pressure data of steady-state CFD calculation as the input file of structural field finite element static stress calculation;
叶片流场瞬态计算，采用瞬态CFD计算模式，瞬态计算过程中对叶片表面蒸汽压力进行统计学参数计算，获得叶片热力边界的叶片流场瞬态结果，提取叶片表面各个节点的蒸汽压力的均方差值，编制动应力计算模块的激振力输入文件，激振力输入文件格式为csv格式，共计四列数据，前三列为节点在x、y、z三个方向的坐标，第四列为蒸汽压力均方差值。The transient calculation of the blade flow field adopts the transient CFD calculation mode. During the transient calculation process, the statistical parameters of the steam pressure on the blade surface are calculated to obtain the transient results of the blade flow field at the blade thermal boundary, extract the mean square error of the steam pressure at each node on the blade surface, and compile the exciting force input file of the dynamic stress calculation module. The exciting force input file format is csv format, with a total of four columns of data. The first three columns are the coordinates of the nodes in the x, y, and z directions, and the fourth column is the mean square error of the steam pressure.
优选的：步骤三中，叶片结构场计算域建模：采用有限元计算软件，建立叶片结构场模型，叶片结构场模型包括叶片和轮槽，叶根与轮槽连接，对叶片结构场模型进行网格划分，计算域包括叶片全部结构特点，其结构特点包括叶片端部的围带、叶片中部的拉筋、叶 片的叶身和叶片端部的叶根，相邻围带之间、拉筋之间设置摩擦接触；叶根和轮槽之间设置摩擦基础，采用循环对称法模拟，轮槽为固定约束，动叶片和轮槽旋转速度为汽轮机工作转速，模拟离心力作用；Preferably, in step 3, the blade structure field calculation domain modeling: using finite element calculation software, the blade structure field model is established, the blade structure field model includes the blade and the wheel groove, the blade root is connected to the wheel groove, the blade structure field model is meshed, the calculation domain includes all the structural features of the blade, and its structural features include the shroud at the end of the blade, the ribs in the middle of the blade, and the blade Frictional contact is set between the blade body and the blade root at the end of the blade, between adjacent shrouds and between the tie bars; a friction base is set between the blade root and the wheel groove, and the cyclic symmetry method is used for simulation. The wheel groove is a fixed constraint, and the rotation speed of the moving blade and the wheel groove is the working speed of the steam turbine to simulate the centrifugal force.
叶片静应力计算：基于叶片结构场模型，将稳态流场计算模块的叶片流场稳态计算的叶片表面压力结果作为静应力计算输入文件，模拟蒸汽力作用，计算叶片静应力，获得叶片静应力分布特征，将静应力计算结果作为叶片动应力考核模块的输入数据；Blade static stress calculation: Based on the blade structure field model, the blade surface pressure result of the blade flow field steady-state calculation of the steady-state flow field calculation module is used as the static stress calculation input file, the steam force is simulated, the blade static stress is calculated, the blade static stress distribution characteristics are obtained, and the static stress calculation result is used as the input data of the blade dynamic stress assessment module;
叶片共振频率计算：基于叶片结构场模型，计算叶片共振频率，获得汽轮机工作转速下前2阶的叶片共振频率，将共振频率结果作为叶片动应力计算模块的输入。Blade resonance frequency calculation: Based on the blade structure field model, the blade resonance frequency is calculated to obtain the first two orders of blade resonance frequencies at the turbine operating speed, and the resonance frequency results are used as the input of the blade dynamic stress calculation module.
优选的：叶片结构场计算域建模：对叶片结构场模型进行网格划分时，在动叶片倒圆、动叶片进出汽倒圆、轮槽倒圆处加密网格。Optimized: Modeling of blade structure field calculation domain: When meshing the blade structure field model, the mesh is encrypted at the rounding of the moving blades, the rounding of the moving blade inlet and outlet steam, and the rounding of the wheel groove.
优选的：步骤四中，基于叶片结构场模型，以瞬态流场计算模块的瞬态流场计算的叶片表面压力均方差作为激振力输入文件，以叶片共振频率计算模块的叶片共振频率计算所计算出的与工作转速距离最近的共振模态对应的共振频率作为输入文件，计算叶片动应力，获得叶片动应力分布特征，将动应力计算结果作为叶片动应力考核模块的输入数据。Preferably: in step four, based on the blade structure field model, the mean square error of the blade surface pressure calculated by the transient flow field calculation module of the transient flow field calculation module is used as the exciting force input file, and the resonance frequency corresponding to the resonance mode closest to the working speed calculated by the blade resonance frequency calculation module of the blade resonance frequency is used as the input file, the blade dynamic stress is calculated, the blade dynamic stress distribution characteristics are obtained, and the dynamic stress calculation results are used as input data for the blade dynamic stress assessment module.
优选的：还包括步骤五：叶片动应力考核，采用叶片动应力考核模块。Preferably, the method further comprises step five: blade dynamic stress assessment, using a blade dynamic stress assessment module.
优选的：步骤五中，编制叶片动应力考核表；Preferably: in step 5, a blade dynamic stress assessment table is prepared;
所述考核表第二列“叶高”，指的是叶片的叶身高度，单位mm；所述考核表第三列“工况”，指的是所计算的超低负荷工况点；所述考核表中给出的“考核位置”，考核位置分为叶身考核和叶根考核两类，所述叶身考核分为考核位置A、考核位置B，所述叶根考核分为考核位置C、考核位置D；The second column "Blade Height" of the assessment table refers to the blade height of the blade, in mm; the third column "Operating Condition" of the assessment table refers to the calculated ultra-low load operating point; the "Assessment Position" given in the assessment table, the assessment position is divided into blade body assessment and blade root assessment, the blade body assessment is divided into assessment position A and assessment position B, the blade root assessment is divided into assessment position C and assessment position D;
所述考核表中给出的动应力许用值，指的是叶片动应力满足设计安全要求的最大值；The allowable value of dynamic stress given in the assessment table refers to the maximum value of the blade dynamic stress that meets the design safety requirements;
所述动应力许用值获得过程为：基于叶片材料的GOODMAN试验曲线，以静应力数据为输入，查询材料的耐振强度，以制造厂规定的安全系数为准则，计算动应力许用值；The process of obtaining the dynamic stress allowable value is as follows: based on the GOODMAN test curve of the blade material, taking the static stress data as input, querying the vibration resistance of the material, and calculating the dynamic stress allowable value based on the safety factor specified by the manufacturer;
所述动应力许用值采用以下公式计算：动应力许用值＝耐振强度/安全系数；The allowable value of dynamic stress is calculated using the following formula: allowable value of dynamic stress = vibration resistance / safety factor;
叶片动应力评估安全准则为：叶身和叶根考核位置的动应力≤动应力许用值，当考核不合格时，需要增加叶片阻尼、叶片刚性或提升叶片材料等级方式对叶片进行优化设计，确保叶片动应力考核合格。The safety criterion for blade dynamic stress assessment is: the dynamic stress at the blade body and blade root assessment position ≤ the allowable value of dynamic stress. When the assessment fails, it is necessary to increase the blade damping, blade rigidity or improve the blade material grade to optimize the blade design to ensure that the blade dynamic stress assessment passes.
本发明具有以下有益效果：The present invention has the following beneficial effects:
本发明适用于超低负荷、紊乱流场下的叶片振动特征，通常属于涡流效应引起的随机振动，从流场特征入手，提取和分析激振力，从而实现叶片动应力的计算。The present invention is applicable to blade vibration characteristics under ultra-low load and turbulent flow fields, which are usually random vibrations caused by eddy current effects. Starting from the flow field characteristics, the exciting force is extracted and analyzed, thereby realizing the calculation of blade dynamic stress.
本发明通过提取流场脉动压力作为激振力，用于叶片动应力计算，相比当前双向流固耦合计算方法，能够显著减少对计算机资源的依赖，降低计算时间，适用于工程应用。The present invention extracts the flow field pulsating pressure as the exciting force for blade dynamic stress calculation. Compared with the current two-way fluid-solid coupling calculation method, it can significantly reduce the dependence on computer resources and reduce the calculation time, and is suitable for engineering applications.
本发明已通过叶片动应力试验验证了算法有效性，本发明的计算值与试验值偏差约13.6％，满足工程应用要求。The effectiveness of the algorithm of the present invention has been verified through a blade dynamic stress test. The deviation between the calculated value of the present invention and the test value is about 13.6%, which meets the requirements of engineering application.
附图说明BRIEF DESCRIPTION OF THE DRAWINGS
图1是一种汽轮机超低负荷叶片动应力三维计算方法的框架图；FIG1 is a framework diagram of a three-dimensional calculation method for dynamic stress of a steam turbine ultra-low load blade;
图2是叶片流场计算域建模示意图； FIG2 is a schematic diagram of blade flow field calculation domain modeling;
图3是低负荷工况叶片稳态流场计算结果(以15％为例)；Figure 3 is the calculation result of the steady-state flow field of the blade under low load condition (taking 15% as an example);
图4是叶片结构示意图。FIG. 4 is a schematic diagram of the blade structure.
图中：1-静叶片，2-动叶片，3-静叶片入口，4-动叶片出口，5-轮槽，6-叶根，7-拉筋，8-围带。In the figure: 1-static blade, 2-moving blade, 3-static blade inlet, 4-moving blade outlet, 5-wheel groove, 6-blade root, 7-tensioning rod, 8-shroud.
具体实施方式Detailed ways
为使本发明的目的、技术方案和优点更加清楚明了，下面通过附图中示出的具体实施例来描述本发明。但是应该理解，这些描述只是示例性的，而并非要限制本发明的范围。此外，在以下说明中，省略了对公知结构和技术的描述，以避免不必要地混淆本发明的概念。In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is described below by the specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.
本发明所提到的连接分为固定连接和可拆卸连接，所述固定连接即为不可拆卸连接包括但不限于折边连接、铆钉连接、粘结连接和焊接连接等常规固定连接方式，所述可拆卸连接包括但不限于螺纹连接、卡扣连接、销钉连接和铰链连接等常规拆卸方式，未明确限定具体连接方式时，默认为总能在现有连接方式中找到至少一种连接方式能够实现该功能，本领域技术人员可根据需要自行选择。例如：固定连接选择焊接连接，可拆卸连接选择铰链连接。The connection mentioned in the present invention is divided into fixed connection and detachable connection. The fixed connection is a non-detachable connection including but not limited to conventional fixed connection methods such as folding connection, rivet connection, bonding connection and welding connection. The detachable connection includes but not limited to conventional detachable methods such as threaded connection, snap connection, pin connection and hinge connection. When the specific connection method is not clearly defined, it is assumed that at least one connection method can always be found in the existing connection methods to achieve the function. Those skilled in the art can choose according to their needs. For example: a fixed connection is a welding connection, and a detachable connection is a hinge connection.
具体实施方式一：结合图1-图4说明本实施方式，本实施方式的汽轮机超低负荷叶片动应力三维计算系统，包括热力边界计算模块、叶片三维流场计算模块、叶片有限元计算模块和叶片动应力计算模块；Specific implementation method 1: This implementation method is described in conjunction with Figures 1 to 4. The three-dimensional calculation system for dynamic stress of ultra-low-load blades of a steam turbine in this implementation method includes a thermal boundary calculation module, a blade three-dimensional flow field calculation module, a blade finite element calculation module and a blade dynamic stress calculation module;
热力边界计算模块：用于获得叶片进出口流量、总焓、压力的热力数据，为叶片三维流场计算提供热力边界；Thermal boundary calculation module: used to obtain thermal data of blade inlet and outlet flow, total enthalpy and pressure, and provide thermal boundary for blade three-dimensional flow field calculation;
叶片三维流场计算模块：用于获得叶片稳态、瞬态流场计算结果，为叶片结构场静应力和动应力计算提供输入数据；Blade three-dimensional flow field calculation module: used to obtain blade steady-state and transient flow field calculation results, and provide input data for blade structure field static stress and dynamic stress calculation;
叶片三维流场计算模块包括：叶片流场计算域建模模块2.1、稳态流场计算模块2.2和瞬态流场计算模块2.3；The blade three-dimensional flow field calculation module includes: blade flow field calculation domain modeling module 2.1, steady-state flow field calculation module 2.2 and transient flow field calculation module 2.3;
叶片有限元计算模块：用于获得叶片静应力、共振频率的计算结果，为叶片动应力计算提供输入数据；Blade finite element calculation module: used to obtain the calculation results of blade static stress and resonance frequency, and provide input data for blade dynamic stress calculation;
叶片有限元计算模块包括：叶片结构场计算域建模模块3.1、叶片静应力计算模块3.2和叶片共振频率计算模块3.3；The blade finite element calculation module includes: a blade structure field calculation domain modeling module 3.1, a blade static stress calculation module 3.2 and a blade resonance frequency calculation module 3.3;
叶片动应力计算模块：用于获得叶片动应力计算结果，为叶片动应力考核模块提供数据；Blade dynamic stress calculation module: used to obtain blade dynamic stress calculation results and provide data for blade dynamic stress assessment module;
还包括叶片动应力考核模块：用于评估和考核叶片动应力安全性，指导叶片优化设计。It also includes a blade dynamic stress assessment module: used to evaluate and assess the blade dynamic stress safety and guide blade optimization design.
具体实施方式二：结合图1-图4说明本实施方式，本实施方式的一种汽轮机超低负荷叶片动应力三维计算方法，包括热力边界计算模块、叶片三维流场计算模块、叶片有限元计算模块和叶片动应力计算模块；Specific implementation method 2: This implementation method is described in conjunction with Figures 1 to 4. This implementation method is a three-dimensional calculation method for dynamic stress of ultra-low load blades of a steam turbine, including a thermal boundary calculation module, a blade three-dimensional flow field calculation module, a blade finite element calculation module and a blade dynamic stress calculation module;
热力边界计算模块：用于获得叶片进出口流量、总焓、压力的热力数据，为叶片三维流场计算提供热力边界；Thermal boundary calculation module: used to obtain thermal data of blade inlet and outlet flow, total enthalpy and pressure, and provide thermal boundary for blade three-dimensional flow field calculation;
叶片三维流场计算模块：用于获得叶片稳态、瞬态流场计算结果，为叶片结构场静 应力和动应力计算提供输入数据；Blade three-dimensional flow field calculation module: used to obtain blade steady-state and transient flow field calculation results, and to calculate the blade structure field static state. Provide input data for stress and dynamic stress calculations;
叶片三维流场计算模块包括：叶片流场计算域建模模块2.1、稳态流场计算模块2.2和瞬态流场计算模块2.3；The blade three-dimensional flow field calculation module includes: blade flow field calculation domain modeling module 2.1, steady-state flow field calculation module 2.2 and transient flow field calculation module 2.3;
叶片有限元计算模块：用于获得叶片静应力、共振频率的计算结果，为叶片动应力计算提供输入数据；Blade finite element calculation module: used to obtain the calculation results of blade static stress and resonance frequency, and provide input data for blade dynamic stress calculation;
叶片有限元计算模块包括：叶片结构场计算域建模模块3.1、叶片静应力计算模块3.2和叶片共振频率计算模块3.3；The blade finite element calculation module includes: a blade structure field calculation domain modeling module 3.1, a blade static stress calculation module 3.2 and a blade resonance frequency calculation module 3.3;
叶片动应力计算模块：用于获得叶片动应力计算结果，为叶片动应力考核模块提供数据；Blade dynamic stress calculation module: used to obtain blade dynamic stress calculation results and provide data for blade dynamic stress assessment module;
还包括叶片动应力考核模块：用于评估和考核叶片动应力安全性，指导叶片优化设计；It also includes a blade dynamic stress assessment module: used to evaluate and assess the blade dynamic stress safety and guide blade optimization design;
包括以下步骤：The following steps are involved:
步骤一：结合图1，热力边界计算；采用热力边界计算模块模块，针对目标叶片，采用热力计算程序获得汽轮机不同负荷条件下的叶片热力边界，提取叶片入口流量、总焓值、出口压力和温度值，作为叶片三维流场计算的输入边界；Step 1: Combined with Figure 1, thermal boundary calculation; using the thermal boundary calculation module, for the target blade, use the thermal calculation program to obtain the thermal boundary of the blade under different load conditions of the turbine, extract the blade inlet flow, total enthalpy value, outlet pressure and temperature value as the input boundary of the blade three-dimensional flow field calculation;
叶片热力边界包括5％、10％、15％、20％、25％、30％等典型超低负荷工况点；The thermal boundary of the blade includes typical ultra-low load operating points such as 5%, 10%, 15%, 20%, 25%, and 30%;
步骤二：叶片三维流场计算；采用叶片三维流场计算模块，首先采用叶片流场计算域建模模块2.1进行叶片流场计算域建模，再次采用稳态流场计算模块2.2进行叶片流场稳态计算，最后采用瞬态流场计算模块2.3进行叶片流场瞬态计算；Step 2: blade three-dimensional flow field calculation; using the blade three-dimensional flow field calculation module, first use the blade flow field calculation domain modeling module 2.1 to perform blade flow field calculation domain modeling, then use the steady-state flow field calculation module 2.2 to perform steady-state calculation of the blade flow field, and finally use the transient flow field calculation module 2.3 to perform transient calculation of the blade flow field;
结合图2，步骤二中，叶片流场计算域建模：采用CFD计算软件，建立叶片三维流场计算域模型，叶片由静叶片1和动叶片2组成，静叶片1与动叶片2连通，静叶片侧具有静叶片入口3，动叶片侧具有动叶片出口4，对叶片进行网格划分，网格节点数量满足网格无关性要求，计算域以静叶片入口为计算域进口，给定进口流量和总焓值，以动叶片出口为计算域出口，给定出口压力和温度；静叶计算域为静止，动叶计算域为旋转，旋转速度为汽轮机工作转速(3000r/mim)，采用循环对称法模拟，循环对称边界可由CFD计算软件自动生成，计算域工质采用水蒸汽，水蒸汽物性数据源于NIST库，可由CFD计算软件调用；Combined with Figure 2, in step 2, the blade flow field calculation domain modeling: CFD calculation software is used to establish a blade three-dimensional flow field calculation domain model. The blade consists of a stationary blade 1 and a moving blade 2. The stationary blade 1 is connected to the moving blade 2. The stationary blade side has a stationary blade inlet 3 and the moving blade side has a moving blade outlet 4. The blade is meshed, and the number of grid nodes meets the grid independence requirement. The calculation domain uses the stationary blade inlet as the calculation domain inlet, and the inlet flow rate and total enthalpy value are given. The moving blade outlet is the calculation domain outlet, and the outlet pressure and temperature are given; the stationary blade calculation domain is stationary, and the moving blade calculation domain is rotating. The rotation speed is the turbine operating speed (3000r/mim). The cyclic symmetry method is used for simulation, and the cyclic symmetry boundary can be automatically generated by the CFD calculation software. The calculation domain working fluid uses water vapor. The water vapor physical property data comes from the NIST library and can be called by the CFD calculation software.
结合图3，叶片流场稳态计算，采用稳态CFD计算模式，获得叶片热力边界的叶片流场稳态结果，掌握流场分离、脱流的分布特征，并将稳态CFD计算的结果文件作为瞬态流场计算的输入文件，将稳态CFD计算的叶片表面压力数据作为结构场有限元静应力计算的输入文件；Combined with Figure 3, the blade flow field steady-state calculation, using the steady-state CFD calculation mode, obtain the blade flow field steady-state results of the blade thermal boundary, master the flow field separation, the distribution characteristics of the flow separation, and the steady-state CFD calculation result file as the input file for the transient flow field calculation, and the blade surface pressure data calculated by the steady-state CFD as the input file for the structural field finite element static stress calculation;
叶片流场瞬态计算，采用瞬态CFD计算模式，瞬态计算过程中对叶片表面蒸汽压力进行统计学参数计算，统计学参数包括计算周期内的压力平均值、均方差值、最大值、最小值，获得叶片热力边界的叶片流场瞬态结果，提取叶片表面各个节点的蒸汽压力的均方差值，编制动应力计算模块的激振力输入文件，激振力输入文件格式为csv格式，共计四列数据，前三列为节点在x、y、z三个方向的坐标，第四列为蒸汽压力均方差值；The transient calculation of the blade flow field adopts the transient CFD calculation mode. During the transient calculation process, the statistical parameters of the steam pressure on the blade surface are calculated. The statistical parameters include the pressure average value, mean square error value, maximum value, and minimum value within the calculation period. The transient results of the blade flow field at the thermal boundary of the blade are obtained, and the mean square error value of the steam pressure at each node on the blade surface is extracted. The excitation force input file of the dynamic stress calculation module is compiled. The excitation force input file format is csv format, with a total of four columns of data. The first three columns are the coordinates of the nodes in the x, y, and z directions, and the fourth column is the mean square error value of the steam pressure.
结合图4，步骤三：叶片有限元计算；采用叶片有限元计算模块，首先采用叶片结构场计算域建模模块3.1进行叶片结构场计算域建模，再次采用叶片静应力计算模块3.2进行叶片静应力计算，最后采用叶片共振频率计算模块3.3进行叶片共振频率计算；Combined with Figure 4, step three: blade finite element calculation; using the blade finite element calculation module, first use the blade structure field calculation domain modeling module 3.1 to perform blade structure field calculation domain modeling, then use the blade static stress calculation module 3.2 to perform blade static stress calculation, and finally use the blade resonance frequency calculation module 3.3 to perform blade resonance frequency calculation;
步骤三中，叶片结构场计算域建模：采用有限元计算软件，建立叶片结构场模型， 叶片结构场模型包括叶片和轮槽5，叶根6与轮槽5连接，对叶片结构场模型进行网格划分，计算域包括叶片全部结构特点，其结构特点包括叶片端部的围带8、叶片中部的拉筋7、叶片的叶身和叶片端部的叶根6，相邻围带8之间、拉筋7之间设置摩擦接触，摩擦系数0.2；叶根6和轮槽5之间设置摩擦基础，摩擦系数0.25，采用循环对称法模拟，循环对称边界通常为围带和轮槽的周期面，轮槽为固定约束，动叶片和轮槽旋转速度为汽轮机工作转速(3000r/mim)，模拟离心力作用，动叶片和轮槽材料源于材料试验数据，主要包括弹性模量、泊松比、密度；In step 3, blade structure field calculation domain modeling: finite element calculation software is used to establish the blade structure field model. The blade structure field model includes blades and wheel grooves 5. The blade root 6 is connected to the wheel groove 5. The blade structure field model is meshed. The calculation domain includes all the structural features of the blade, including the shroud 8 at the end of the blade, the tie rod 7 in the middle of the blade, the blade body of the blade and the blade root 6 at the end of the blade. Friction contact is set between adjacent shrouds 8 and tie rods 7, and the friction coefficient is 0.2; a friction base is set between the blade root 6 and the wheel groove 5, and the friction coefficient is 0.25. The cyclic symmetry method is used for simulation. The cyclic symmetry boundary is usually the periodic surface of the shroud and the wheel groove. The wheel groove is a fixed constraint. The rotation speed of the moving blade and the wheel groove is the working speed of the steam turbine (3000r/mim). The centrifugal force is simulated. The moving blade and the wheel groove material is derived from the material test data, mainly including elastic modulus, Poisson's ratio, and density.
叶片结构场计算域建模：对叶片结构场模型进行网格划分时，在动叶片倒圆、动叶片进出汽倒圆、轮槽倒圆处加密网格，确保计算精度；Blade structure field calculation domain modeling: When meshing the blade structure field model, the mesh is encrypted at the rounding of the moving blades, the rounding of the moving blades in and out, and the rounding of the wheel groove to ensure the calculation accuracy;
叶片静应力计算：基于叶片结构场模型，将稳态流场计算模块2.2的叶片流场稳态计算的叶片表面压力结果作为静应力计算输入文件，模拟蒸汽力作用，计算叶片静应力，获得叶片静应力分布特征，将静应力计算结果作为叶片动应力考核模块的输入数据；Blade static stress calculation: Based on the blade structure field model, the blade surface pressure result of the blade flow field steady-state calculation of the steady-state flow field calculation module 2.2 is used as the static stress calculation input file, the steam force is simulated, the blade static stress is calculated, the blade static stress distribution characteristics are obtained, and the static stress calculation result is used as the input data of the blade dynamic stress assessment module;
叶片共振频率计算：基于叶片结构场模型，计算叶片共振频率，获得汽轮机工作转速(3000r/mim)下前2阶的叶片共振频率，将共振频率结果作为叶片动应力计算模块的输入；Blade resonance frequency calculation: Based on the blade structure field model, the blade resonance frequency is calculated to obtain the first two-order blade resonance frequencies at the turbine operating speed (3000r/min), and the resonance frequency results are used as the input of the blade dynamic stress calculation module;
步骤四：叶片动应力计算，采用叶片动应力计算模块；Step 4: Blade dynamic stress calculation, using blade dynamic stress calculation module;
步骤四中，基于叶片结构场模型，以瞬态流场计算模块2.3的瞬态流场计算的叶片表面压力均方差作为激振力输入文件，以叶片共振频率计算模块3.3的叶片共振频率计算所计算出的与工作转速(3000r/min)距离最近的共振模态对应的共振频率作为输入文件，计算叶片动应力，获得叶片动应力分布特征，将动应力计算结果作为叶片动应力考核模块的输入数据；In step 4, based on the blade structure field model, the mean square error of the blade surface pressure calculated by the transient flow field calculation module 2.3 is used as the exciting force input file, and the resonance frequency corresponding to the resonance mode closest to the working speed (3000r/min) calculated by the blade resonance frequency calculation module 3.3 is used as the input file to calculate the blade dynamic stress, obtain the blade dynamic stress distribution characteristics, and use the dynamic stress calculation result as the input data of the blade dynamic stress assessment module;
还包括步骤五：叶片动应力考核(监测)，采用叶片动应力考核模块；It also includes step 5: blade dynamic stress assessment (monitoring), using a blade dynamic stress assessment module;
步骤五中，编制叶片动应力考核表,如表1所示：In step 5, prepare the blade dynamic stress assessment table, as shown in Table 1:
表1叶片动应力考核表
Table 1 Blade dynamic stress assessment table
所述考核表第二列“叶高”，指的是叶片的叶身高度，单位mm；所述考核表第三列“工况”，指的是所计算的超低负荷工况点；所述考核表中给出的“考核位置”，考核位置分为叶身考核和叶根考核两类，所述叶身考核分为考核位置A、考核位置B，所述叶根考核分为考核位置C、考核位置D；The second column "Blade Height" of the assessment table refers to the blade height of the blade, in mm; the third column "Operating Condition" of the assessment table refers to the calculated ultra-low load operating point; the "Assessment Position" given in the assessment table, the assessment position is divided into blade body assessment and blade root assessment, the blade body assessment is divided into assessment position A and assessment position B, the blade root assessment is divided into assessment position C and assessment position D;
所述考核位置A，指的是叶身静应力峰值位置；静应力峰值从叶片静应力计算模块3.2的叶片静应力计算提取；动应力值包括1阶共振考核点和2阶共振考核点；所述共振考核点，指的是叶片共振频率计算模块3.3的叶片共振频率计算所计算出的距离工作转速 (3000r/min)距离最近的共振模态；1阶共振考核点和2阶共振考核点的动应力值从叶片动应力计算中提取；The assessment position A refers to the peak position of the static stress of the blade body; the static stress peak is extracted from the blade static stress calculation of the blade static stress calculation module 3.2; the dynamic stress value includes the first-order resonance assessment point and the second-order resonance assessment point; the resonance assessment point refers to the distance from the working speed calculated by the blade resonance frequency calculation module 3.3 (3000r/min) the nearest resonance mode; the dynamic stress values of the 1st order resonance test point and the 2nd order resonance test point are extracted from the blade dynamic stress calculation;
所述考核位置B，指的是叶身动应力峰值位置；所述动应力峰值位置包括1阶共振考核点和2阶共振考核点；所述共振考核点，指的是叶片共振频率计算模块3.3的叶片共振频率计算所计算出的距离工作转速(3000r/min)距离最近的共振模态；1阶共振考核点和2阶共振考核点的动应力峰值从叶片动应力计算中提取；1阶和2阶的静应力值从叶片静应力计算模块3.2的叶片静应力计算提取。The assessment position B refers to the peak position of the dynamic stress of the blade body; the dynamic stress peak position includes the 1st-order resonance assessment point and the 2nd-order resonance assessment point; the resonance assessment point refers to the resonance mode closest to the working speed (3000r/min) calculated by the blade resonance frequency calculation of the blade resonance frequency calculation module 3.3; the dynamic stress peak values of the 1st-order resonance assessment point and the 2nd-order resonance assessment point are extracted from the blade dynamic stress calculation; the 1st-order and 2nd-order static stress values are extracted from the blade static stress calculation of the blade static stress calculation module 3.2.
所述考核位置C，指的是叶根静应力峰值位置；静应力峰值从叶片静应力计算模块3.2的中叶片静应力计算提取；动应力值包括1阶共振考核点和2阶共振考核点；所述共振考核点，指的是叶片共振频率计算模块3.3的叶片共振频率计算模块所计算出的距离工作转速(3000r/min)距离最近的共振模态；1阶共振考核点和2阶共振考核点的动应力值叶片动应力计算模块中提取；The assessment position C refers to the peak position of the static stress at the blade root; the static stress peak is extracted from the blade static stress calculation module 3.2; the dynamic stress value includes the 1st order resonance assessment point and the 2nd order resonance assessment point; the resonance assessment point refers to the resonance mode closest to the working speed (3000r/min) calculated by the blade resonance frequency calculation module 3.3; the dynamic stress values of the 1st order resonance assessment point and the 2nd order resonance assessment point are extracted from the blade dynamic stress calculation module;
所述考核位置D，指的是叶根动应力峰值位置；所述动应力峰值位置包括1阶共振考核点和2阶共振考核点；所述共振考核点，指的是叶片共振频率计算模块3.3的叶片共振频率计算所计算出的距离工作转速(3000r/min)距离最近的共振模态；1阶共振考核点和2阶共振考核点的动应力峰值从叶片动应力计算模块中提取；1阶和2阶的静应力值从叶片静应力计算模块3.2的叶片静应力计算模块提取；The assessment position D refers to the peak position of the dynamic stress at the blade root; the dynamic stress peak position includes the 1st order resonance assessment point and the 2nd order resonance assessment point; the resonance assessment point refers to the resonance mode closest to the working speed (3000r/min) calculated by the blade resonance frequency calculation module 3.3; the dynamic stress peak values of the 1st order resonance assessment point and the 2nd order resonance assessment point are extracted from the blade dynamic stress calculation module; the 1st order and 2nd order static stress values are extracted from the blade static stress calculation module of the blade static stress calculation module 3.2;
所述考核表中给出的动应力许用值，指的是叶片动应力满足设计安全要求的最大值；The allowable value of dynamic stress given in the assessment table refers to the maximum value of the blade dynamic stress that meets the design safety requirements;
所述动应力许用值获得过程为：基于叶片材料的GOODMAN试验曲线，以静应力数据为输入，查询材料的耐振强度，以制造厂规定的安全系数为准则，计算动应力许用值；The process of obtaining the dynamic stress allowable value is as follows: based on the GOODMAN test curve of the blade material, taking the static stress data as input, querying the vibration resistance of the material, and calculating the dynamic stress allowable value based on the safety factor specified by the manufacturer;
所述动应力许用值采用以下公式计算：动应力许用值＝耐振强度/安全系数；The allowable value of dynamic stress is calculated using the following formula: allowable value of dynamic stress = vibration resistance / safety factor;
叶片动应力评估安全准则为：叶身和叶根考核位置的动应力≤动应力许用值，当考核不合格时，需要增加叶片阻尼、叶片刚性或提升叶片材料等级等方式对叶片进行优化设计，确保叶片动应力考核合格；The safety criterion for blade dynamic stress assessment is: the dynamic stress at the blade body and blade root assessment position is ≤ the allowable value of dynamic stress. If the assessment fails, the blade damping, blade rigidity or blade material grade should be increased to optimize the blade design to ensure that the blade dynamic stress assessment passes.
本发明适用于汽轮机超低负荷运行工况下的叶片动应力计算，为叶片动应力预测和考核提供技术手段。The present invention is applicable to the calculation of blade dynamic stress under the ultra-low load operation condition of a steam turbine, and provides a technical means for the prediction and assessment of blade dynamic stress.
需要说明的是，在以上实施例中，只要不矛盾的技术方案都能够进行排列组合，本领域技术人员能够根据排列组合的数学知识穷尽所有可能，因此本发明不再对排列组合后的技术方案进行一一说明，但应该理解为排列组合后的技术方案已经被本发明所公开。It should be noted that in the above embodiments, as long as the technical solutions are not contradictory, they can be arranged and combined, and those skilled in the art can exhaust all possibilities based on the mathematical knowledge of arrangement and combination. Therefore, the present invention will no longer describe the technical solutions after arrangement and combination one by one, but it should be understood that the technical solutions after arrangement and combination have been disclosed by the present invention.
本实施方式只是对本专利的示例性说明，并不限定它的保护范围，本领域技术人员还可以对其局部进行改变，只要没有超出本专利的精神实质，都在本专利的保护范围内。 This implementation is only an exemplary description of this patent and does not limit its protection scope. Those skilled in the art may also make partial changes to it, as long as they do not exceed the spirit of this patent, they are all within the protection scope of this patent.

Claims (10)

  1. 汽轮机超低负荷叶片动应力三维计算系统，其特征在于：包括热力边界计算模块、叶片三维流场计算模块、叶片有限元计算模块和叶片动应力计算模块；The three-dimensional calculation system for dynamic stress of ultra-low-load blades of steam turbines is characterized by comprising a thermal boundary calculation module, a blade three-dimensional flow field calculation module, a blade finite element calculation module and a blade dynamic stress calculation module;
    热力边界计算模块：用于获得叶片进出口流量、总焓、压力的热力数据，为叶片三维流场计算提供热力边界；Thermal boundary calculation module: used to obtain thermal data of blade inlet and outlet flow, total enthalpy and pressure, and provide thermal boundary for blade three-dimensional flow field calculation;
    叶片三维流场计算模块：用于获得叶片稳态、瞬态流场计算结果，为叶片结构场静应力和动应力计算提供输入数据；Blade three-dimensional flow field calculation module: used to obtain blade steady-state and transient flow field calculation results, and provide input data for blade structure field static stress and dynamic stress calculation;
    叶片三维流场计算模块包括：叶片流场计算域建模模块(2.1)、稳态流场计算模块(2.2)和瞬态流场计算模块(2.3)；The blade three-dimensional flow field calculation module includes: a blade flow field calculation domain modeling module (2.1), a steady-state flow field calculation module (2.2) and a transient flow field calculation module (2.3);
    叶片有限元计算模块：用于获得叶片静应力、共振频率的计算结果，为叶片动应力计算提供输入数据；Blade finite element calculation module: used to obtain the calculation results of blade static stress and resonance frequency, and provide input data for blade dynamic stress calculation;
    叶片有限元计算模块包括：叶片结构场计算域建模模块(3.1)、叶片静应力计算模块(3.2)和叶片共振频率计算模块(3.3)；The blade finite element calculation module includes: a blade structure field calculation domain modeling module (3.1), a blade static stress calculation module (3.2) and a blade resonance frequency calculation module (3.3);
    叶片动应力计算模块：用于获得叶片动应力计算结果，为叶片动应力考核模块提供数据。Blade dynamic stress calculation module: used to obtain blade dynamic stress calculation results and provide data for the blade dynamic stress assessment module.
  2. 根据权利要求1所述的汽轮机超低负荷叶片动应力三维计算系统，其特征在于：还包括叶片动应力考核模块：用于评估和考核叶片动应力安全性，指导叶片优化设计。The three-dimensional calculation system for dynamic stress of ultra-low-load blades of a steam turbine according to claim 1 is characterized in that it also includes a blade dynamic stress assessment module: used to evaluate and assess the safety of blade dynamic stress and guide blade optimization design.
  3. 汽轮机超低负荷叶片动应力三维计算方法，其特征在于：采用权利要求2所述的汽轮机超低负荷叶片动应力三维计算系统，包括以下步骤：The three-dimensional calculation method of dynamic stress of ultra-low load blades of steam turbine is characterized by: using the three-dimensional calculation system of dynamic stress of ultra-low load blades of steam turbine according to claim 2, comprising the following steps:
    步骤一：热力边界计算；采用热力边界计算模块模块，针对目标叶片，采用热力计算程序获得汽轮机不同负荷条件下的叶片热力边界，提取叶片入口流量、总焓值、出口压力和温度值，作为叶片三维流场计算的输入边界；Step 1: Thermal boundary calculation: Using the thermal boundary calculation module, for the target blade, a thermal calculation program is used to obtain the thermal boundary of the blade under different load conditions of the turbine, and the blade inlet flow, total enthalpy value, outlet pressure and temperature values are extracted as the input boundary for the blade three-dimensional flow field calculation;
    步骤二：叶片三维流场计算；采用叶片三维流场计算模块，首先采用叶片流场计算域建模模块(2.1)进行叶片流场计算域建模，再次采用稳态流场计算模块(2.2)进行叶片流场稳态计算，最后采用瞬态流场计算模块(2.3)进行叶片流场瞬态计算；Step 2: blade three-dimensional flow field calculation; using the blade three-dimensional flow field calculation module, first use the blade flow field calculation domain modeling module (2.1) to perform blade flow field calculation domain modeling, then use the steady-state flow field calculation module (2.2) to perform steady-state calculation of the blade flow field, and finally use the transient flow field calculation module (2.3) to perform transient calculation of the blade flow field;
    步骤三：叶片有限元计算；采用叶片有限元计算模块，首先采用叶片结构场计算域建模模块(3.1)进行叶片结构场计算域建模，再次采用叶片静应力计算模块(3.2)进行叶片静应力计算，最后采用叶片共振频率计算模块(3.3)进行叶片共振频率计算；Step 3: blade finite element calculation; using the blade finite element calculation module, first use the blade structure field calculation domain modeling module (3.1) to perform blade structure field calculation domain modeling, then use the blade static stress calculation module (3.2) to perform blade static stress calculation, and finally use the blade resonance frequency calculation module (3.3) to perform blade resonance frequency calculation;
    步骤四：叶片动应力计算，采用叶片动应力计算模块。Step 4: Blade dynamic stress calculation, using blade dynamic stress calculation module.
  4. 根据权利要求2所述的汽轮机超低负荷叶片动应力三维计算方法，其特征在于：叶片热力边界包括5％、10％、15％、20％、25％、30％的典型超低负荷工况点。The three-dimensional calculation method for dynamic stress of ultra-low load blades of a steam turbine according to claim 2 is characterized in that the thermal boundary of the blades includes typical ultra-low load operating points of 5%, 10%, 15%, 20%, 25% and 30%.
  5. 根据权利要求4所述的汽轮机超低负荷叶片动应力三维计算方法，其特征在于：步骤二中，叶片流场计算域建模：采用CFD计算软件，建立叶片三维流场计算域模型，对叶片进行网格划分，网格节点数量满足网格无关性要求，计算域以静叶片入口为计算域进口，给定进口流量和总焓值，以动叶片出口为计算域出口，给定出口压力和温度；静叶计算域为静止，动叶计算域为旋转，旋转速度为汽轮机工作转速，采用循环对称法模拟，计算域工质采用水蒸汽；The three-dimensional calculation method for dynamic stress of ultra-low load blades of a steam turbine according to claim 4 is characterized in that: in step 2, the calculation domain of the blade flow field is modeled: CFD calculation software is used to establish a three-dimensional flow field calculation domain model of the blade, and the blade is meshed. The number of mesh nodes meets the mesh independence requirement. The calculation domain uses the inlet of the stationary blade as the calculation domain inlet, and the inlet flow rate and total enthalpy value are given. The outlet of the moving blade is used as the calculation domain outlet, and the outlet pressure and temperature are given; the calculation domain of the stationary blade is stationary, and the calculation domain of the moving blade is rotating. The rotation speed is the working speed of the steam turbine. The cyclic symmetry method is used for simulation, and the working fluid of the calculation domain is water vapor;
    叶片流场稳态计算，采用稳态CFD计算模式，获得叶片热力边界的叶片流场稳态结果，掌握流场分离、脱流的分布特征，并将稳态CFD计算的结果文件作为瞬态流场计算的输入文件，将稳态CFD计算的叶片表面压力数据作为结构场有限元静应力计算的输入文件； Steady-state calculation of blade flow field: using steady-state CFD calculation mode, obtain steady-state results of blade flow field at blade thermal boundary, master the distribution characteristics of flow field separation and flow separation, and use the result file of steady-state CFD calculation as the input file of transient flow field calculation, and use the blade surface pressure data of steady-state CFD calculation as the input file of structural field finite element static stress calculation;
    叶片流场瞬态计算，采用瞬态CFD计算模式，瞬态计算过程中对叶片表面蒸汽压力进行统计学参数计算，获得叶片热力边界的叶片流场瞬态结果，提取叶片表面各个节点的蒸汽压力的均方差值，编制动应力计算模块的激振力输入文件，激振力输入文件格式为csv格式，共计四列数据，前三列为节点在x、y、z三个方向的坐标，第四列为蒸汽压力均方差值。The transient calculation of the blade flow field adopts the transient CFD calculation mode. During the transient calculation process, the statistical parameters of the steam pressure on the blade surface are calculated to obtain the transient results of the blade flow field at the blade thermal boundary, extract the mean square error of the steam pressure at each node on the blade surface, and compile the exciting force input file of the dynamic stress calculation module. The exciting force input file format is csv format, with a total of four columns of data. The first three columns are the coordinates of the nodes in the x, y, and z directions, and the fourth column is the mean square error of the steam pressure.
  6. 根据权利要求5所述的汽轮机超低负荷叶片动应力三维计算方法，其特征在于：步骤三中，叶片结构场计算域建模：采用有限元计算软件，建立叶片结构场模型，叶片结构场模型包括叶片和轮槽(5)，叶根(6)与轮槽(5)连接，对叶片结构场模型进行网格划分，计算域包括叶片全部结构特点，其结构特点包括叶片端部的围带(8)、叶片中部的拉筋(7)、叶片的叶身和叶片端部的叶根(6)，相邻围带(8)之间、拉筋(7)之间设置摩擦接触；叶根(6)和轮槽(5)之间设置摩擦基础，采用循环对称法模拟，轮槽为固定约束，动叶片和轮槽旋转速度为汽轮机工作转速，模拟离心力作用；The three-dimensional calculation method for dynamic stress of ultra-low load blades of a steam turbine according to claim 5 is characterized in that: in step 3, the calculation domain of the blade structure field is modeled: a finite element calculation software is used to establish a blade structure field model, the blade structure field model includes blades and wheel grooves (5), the blade root (6) is connected to the wheel groove (5), the blade structure field model is meshed, and the calculation domain includes all structural features of the blade, and its structural features include a shroud (8) at the end of the blade, a tie rod (7) in the middle of the blade, the blade body of the blade and the blade root (6) at the end of the blade, and friction contact is set between adjacent shrouds (8) and between the tie rods (7); a friction base is set between the blade root (6) and the wheel groove (5), and the cyclic symmetry method is used for simulation, the wheel groove is a fixed constraint, and the rotation speed of the moving blade and the wheel groove is the working speed of the steam turbine to simulate the centrifugal force;
    叶片静应力计算：基于叶片结构场模型，将稳态流场计算模块(2.2)的叶片流场稳态计算的叶片表面压力结果作为静应力计算输入文件，模拟蒸汽力作用，计算叶片静应力，获得叶片静应力分布特征，将静应力计算结果作为叶片动应力考核模块的输入数据；Blade static stress calculation: Based on the blade structure field model, the blade surface pressure result of the blade flow field steady-state calculation of the steady-state flow field calculation module (2.2) is used as the static stress calculation input file, the steam force is simulated, the blade static stress is calculated, the blade static stress distribution characteristics are obtained, and the static stress calculation result is used as the input data of the blade dynamic stress assessment module;
    叶片共振频率计算：基于叶片结构场模型，计算叶片共振频率，获得汽轮机工作转速下前2阶的叶片共振频率，将共振频率结果作为叶片动应力计算模块的输入。Blade resonance frequency calculation: Based on the blade structure field model, the blade resonance frequency is calculated to obtain the first two orders of blade resonance frequencies at the turbine operating speed, and the resonance frequency results are used as the input of the blade dynamic stress calculation module.
  7. 根据权利要求6所述的汽轮机超低负荷叶片动应力三维计算方法，其特征在于：叶片结构场计算域建模：对叶片结构场模型进行网格划分时，在动叶片倒圆、动叶片进出汽倒圆、轮槽倒圆处加密网格。The three-dimensional calculation method for dynamic stress of ultra-low load blades of steam turbine according to claim 6 is characterized by: modeling of blade structure field calculation domain: when meshing the blade structure field model, the mesh is encrypted at the chamfering of the moving blades, the chamfering of the moving blades inlet and outlet, and the chamfering of the wheel groove.
  8. 根据权利要求6所述的汽轮机超低负荷叶片动应力三维计算方法，其特征在于：步骤四中，基于叶片结构场模型，以瞬态流场计算模块(2.3)的瞬态流场计算的叶片表面压力均方差作为激振力输入文件，以叶片共振频率计算模块(3.3)的叶片共振频率计算所计算出的与工作转速距离最近的共振模态对应的共振频率作为输入文件，计算叶片动应力，获得叶片动应力分布特征，将动应力计算结果作为叶片动应力考核模块的输入数据。The three-dimensional calculation method for dynamic stress of ultra-low load blades of a steam turbine according to claim 6 is characterized in that: in step 4, based on the blade structure field model, the mean square error of the blade surface pressure calculated by the transient flow field calculation module (2.3) is used as the exciting force input file, and the resonance frequency corresponding to the resonance mode closest to the working speed calculated by the blade resonance frequency calculation module (3.3) is used as the input file to calculate the blade dynamic stress, obtain the blade dynamic stress distribution characteristics, and use the dynamic stress calculation result as the input data of the blade dynamic stress assessment module.
  9. 根据权利要求8所述的汽轮机超低负荷叶片动应力三维计算方法，其特征在于：还包括步骤五：叶片动应力考核，采用叶片动应力考核模块。The three-dimensional calculation method for dynamic stress of ultra-low load blades of a steam turbine according to claim 8 is characterized in that it also includes step five: blade dynamic stress assessment, using a blade dynamic stress assessment module.
  10. 根据权利要求9所述的汽轮机超低负荷叶片动应力三维计算方法，其特征在于：步骤五中，编制叶片动应力考核表；The three-dimensional calculation method for dynamic stress of ultra-low load blades of a steam turbine according to claim 9 is characterized in that: in step 5, a blade dynamic stress assessment table is prepared;
    所述考核表第二列“叶高”，指的是叶片的叶身高度，单位mm；所述考核表第三列“工况”，指的是所计算的超低负荷工况点；所述考核表中给出的“考核位置”，考核位置分为叶身考核和叶根考核两类，所述叶身考核分为考核位置A、考核位置B，所述叶根考核分为考核位置C、考核位置D；The second column "Blade Height" of the assessment table refers to the blade height of the blade, in mm; the third column "Operating Condition" of the assessment table refers to the calculated ultra-low load operating point; the "Assessment Position" given in the assessment table, the assessment position is divided into blade body assessment and blade root assessment, the blade body assessment is divided into assessment position A and assessment position B, the blade root assessment is divided into assessment position C and assessment position D;
    所述考核表中给出的动应力许用值，指的是叶片动应力满足设计安全要求的最大值；The allowable value of dynamic stress given in the assessment table refers to the maximum value of the blade dynamic stress that meets the design safety requirements;
    所述动应力许用值获得过程为：基于叶片材料的GOODMAN试验曲线，以静应力数据为输入，查询材料的耐振强度，以制造厂规定的安全系数为准则，计算动应力许用值；The process of obtaining the dynamic stress allowable value is as follows: based on the GOODMAN test curve of the blade material, taking the static stress data as input, querying the vibration resistance of the material, and calculating the dynamic stress allowable value based on the safety factor specified by the manufacturer;
    所述动应力许用值采用以下公式计算：动应力许用值＝耐振强度/安全系数；The allowable value of dynamic stress is calculated using the following formula: allowable value of dynamic stress = vibration resistance / safety factor;
    叶片动应力评估安全准则为：叶身和叶根考核位置的动应力≤动应力许用值，当考核不合格时，需要增加叶片阻尼、叶片刚性或提升叶片材料等级方式对叶片进行优化设计，确保叶片动应力考核合格。 The safety criterion for blade dynamic stress assessment is: the dynamic stress at the blade body and blade root assessment position ≤ the allowable value of dynamic stress. When the assessment fails, it is necessary to increase the blade damping, blade rigidity or improve the blade material grade to optimize the blade design to ensure that the blade dynamic stress assessment passes.
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