空化对轴流式水轮机尾水管压力脉动和转轮振动的影响  

Effects of cavitation on pressure fluctuation of draft tube and runner vibration in a Kaplan turbine

作　　者：朱国俊[1] 李康 冯建军[1,2] 罗兴锜 Zhu Guojun;Li Kang;Feng Jianjun;Luo Xingqi(Institute of Water Resources and Hydro-electric Engineering,Xi’an University of Technology,Xi’an 710048,China;Zhejiang FINE Institute of Hydraulic Machinery,Hangzhou 311121,China)

机构地区：[1]西安理工大学水利水电学院,西安710048 [2]浙江富安水力机械研究所,杭州311121

出　　处：《农业工程学报》2021年第11期40-49,共10页Transactions of the Chinese Society of Agricultural Engineering

基　　金：国家重点研发计划(2018YFB1501900);国家自然科学基金(51909212,52079108)。

摘　　要：研究空化对轴流式水轮机尾水管压力脉动和转轮振动的影响规律,可为改善轴流式水轮机运行稳定性提供理论依据。该研究构建了包含高速摄像、激光测振仪(Laser Doppler Vibrometer,LDV)及高频压力脉动传感器的同步测试系统,并通过该系统获得了变空化系数下轴流式水轮机压力脉动数据、转轮径向振动数据及空化图像资料。综合变分模态分解(Variational Mode Decomposition,VMD)、频谱分析以及互相关分析法,揭示了空化对轴流式转轮振动和尾水管压力脉动的影响规律。结果表明:进入空化发展阶段后,尾水管锥管上的压力脉动幅值与转轮径向振动幅值会随空化程度的增加而提高;针对该研究的轴流式水轮机模型,转轮完全空化后,压力脉动峰峰值和转轮径向振动速度峰峰值是无空化时的9.16和10.12倍;空化所导致的转轮径向振动速度信号的中高频幅值提升局限于12.0~200.0倍转频的频率范围内;空化程度的增加还会导致压力脉动出现高频能量局部极值迁移现象,增加了其诱发机组共振的可能性。该研究对提升农业水利工程中轴流式水电站的经济性和运行稳定性有重要意义。Hydropower energy is one of the most important clean energy sources in the world.Since the medium and high head hydropower energy presents a high economic index and exploitability,only a few resources are available at present in China.By contrast,low head hydropower resources become one of the key directions of hydropower development in the future.A Kaplan turbine has also been one of the main unit types for the low head hydropower resources.Nevertheless,cavitation has been only one factor to limit the application,although a wide range was achieved in the high efficiency region.Furthermore,the runner erosion and vibration induced by the cavitation can greatly shorten the normal operating cycle of the Kaplan turbine,even seriously detrimental to the economic benefits of water stations.The vibration and pressure fluctuation are the commonly-used indicators to report the stability of hydraulic turbines.As such,the effect of cavitation on the vibration and pressure fluctuation directly determines the stability and optimization of the Kaplan turbine.In this study,a synchronous test system was constructed to investigate the influence of cavitation on the pressure fluctuation of the draft tube and the runner vibration in a Kaplan turbine.The system included a high-speed camera,a Laser Doppler Vibrometer(LDV),and a high-frequency pressure fluctuation sensor.A Kaplan turbine model was also selected as the research object.The pressure fluctuation,radial vibration,and cavitation images of the runner were first captured under different cavitation coefficients in the synchronous test system.The Variational Mode Decomposition(VMD),the spectrum analysis,and the cross-correlation were then combined to explore the influence of cavitation on the radial vibration of the runner,and the pressure fluctuation on the draft tube.Finally,it was found that there was a significant increase in the amplitudes of pressure fluctuation on the draft cone tube,and the radial vibration velocity of the runner,with the decrease of cavitation coeffici

关 键 词：水力发电 轴流式水轮机 空化 压力脉动 转轮径向振动 信号处理 频域分析 

分 类 号：TK733.3[交通运输工程—轮机工程]