抽蓄机组轴系结构单元选取对模态分析的影响

Effect of shafting structural unit selection on modal analysis in pumped storage units

摘要

【目的】抽水蓄能机组安全稳定运行和轴系无共振发生是抽水蓄能电站有效支撑新型电力系统调节需求的重要保证。【方法】针对抽水蓄能电站中机组轴系选取不同结构单元开展模态特性研究，基于有限元方法，选取400.0~3 000.0 r/min的6种旋转速度工况，对比分析独立水轮机转轮、水轮机转轮-轴、水轮机转轮-轴-发电机转子三种结构单元的6阶激振频率与振型。【结果】结果表明：对于不同结构单元，部件的固有频率与振型均不相同，但不同的结构下亦会出现相同的振型；独立水轮机转轮结构的6阶固有频率最大，且没有出现临界转速；转轮-轴-转子结构的6阶固有频率最小，且在前2阶模态中出现临界转速。对水泵水轮机旋转部件进行模态分析时，第1阶和第2阶模态均出现了临界转速，大小分别为1 387.1 r/min和2 164.0 r/min;而仅考虑水泵水轮机转轮和轴部件下，只在第1阶出现了临界转速，转速大小和转轮-轴-发电机转子的第2阶临界转速相同，为2 164.0 r/min,且对应的振型和固有频率均相同；只考虑水泵水轮机转轮部件时没有出现临界转速。【结论】在对水泵水轮机旋转部件进行模态分析时，考虑发电机转子与轴部件更能精确地发现旋转部件的临界转速并预测共振频率与模态振型，有利于避免机组共振的情况出现。研究成果为抽水蓄能机组轴系结构设计提供了理论依据和工程实践支撑。

Abstract

[Objective] The safe and stable operation of pumped storage units and the avoidance of shafting resonance are essential for pumped storage power stations to effectively meet the regulation demands of new-type power systems. [Methods] Different structural units were selected to study the modal characteristics of the unit shafting in the pumped storage power stations. Based on the finite element method, six rotational speed conditions of 400.0~3 000.0 r/min were selected to conduct a comparative analysis of the sixth-order excitation frequencies and vibration modes of three structural units: independent turbine runner, turbine runner-shaft, and turbine runner-shaft-generator rotor. [Results] The result showed that for different structural units, the natural frequencies and vibration modes of the components were different, though identical vibration modes could occur under different structures. The independent turbine runner structure had the highest sixth-order natural frequency, with no critical speed observed. The runner-shaft-rotor structure had the lowest sixth-order natural frequency, with critical speeds occurring in the first two modes. In the modal analysis of the rotating components of the pump turbine, critical speeds were observed at the 1st and 2nd modes, with speeds of 1 387.1 r/min and 2 164 r/min, respectively. However, when only the runner and shaft components of the pump turbine were considered, the critical speed was observed only at the 1st mode, with a speed identical to the 2nd mode critical speed of the runner-shaft-generator rotor, which was 2 164.0 r/min. The corresponding vibration mode and natural frequency were identical. No critical speed was observed when considering only the runner components of pump turbine. [Conclusion] Therefore, in the modal analysis of the rotating components of the pump turbine, considering the generator rotor and shaft components can more accurately identify the critical speeds of the rotating components and predict the resonance frequencies and vibration modes, which is beneficial for avoiding resonance in the unit. The research findings provide a theoretical basis and engineering support for the design of shafting structure in pumped storage units.

关键词

水泵水轮机 / 模态分析 / 振动特性 / 水轮机轴系 / 抽水蓄能电站

Key words

pump turbine / modal analysis / vibration characteristic / hydraulic turbine shafting / pumped storage power station

基金资助

内蒙古电力(集团)有限责任公司内蒙古电力科学研究院分公司自筹项目(2023-ZC-10)

国家自然科学基金项目(52379086)

江苏省创新支撑计划国际科技合作项目(BZ2023047)