Abstract
The features of unsteady flow such as pressure variation and fluctuation in a large hydraulic turbine usually lead to the instability of operation. This article reports the recent in site investigation concerning the characteristic frequencies in pressure fluctuation, shaft torsional oscillation and structural vibration of a prototype 700 MW Francis turbine unit. The investigation was carried out for a wide load range of 200 MW-700 MW in the condition of water head 57 m-90 m. An extensive analysis of both time-history and frequency data of these unsteady hydraulic behaviours was conducted. It was observed that the pressure fluctuation in a draft tube is stronger than that in upstream flow passage. The low frequency with about one third of rotation frequency is dominative for the pressure fluctuation in part load range. Also the unsteady features of vibration of head cover and torsional oscillation of shaft exhibited the similar features. Numerical analysis showed that the vibration and oscillation are caused by vortex rope in the draft tube. In addition, a strong vibration with special characteristic frequency was observed for the head cover in middle load range. The pressure fluctuation in the draft tube with the same frequency was also recorded. Because this special vibration has appeared in the designed normal running condition, it should be avoided by carefully allocating power load in the future operation.
Similar content being viewed by others
References
SUSAN-RESIGA R., CIOCAN G. D. and ANTON I. et al. Analysis of the swirling flow downstream a Francis turbine runner[J]. Journal of Fluids Engineering, Transactions of ASME, 2006, 128(1): 177–189.
ARZOLA F., AZUAJE C. and ZAMBRANO P. et al. Undesired power oscillations at high load in large Francis turbines: Experimental study and solution[C]. Proceedings of the 23rd Iahr Symposium on Hydraulic Machinery and Systems. Yokohama, Japan, 2006, 1–9.
ILIESCU M. S., CIOCAN G. D. A. Analysis of the cavitating draft tube vortex in a Francis turbine using particle image velocimetry measurements in two-phase flow[J]. Journal of Fluids Engineering, Transactions of ASME, 2008, 130(2): 0211051–02110510.
LACEY R. M., GRIFFIN F. M. Resolving vibration problems on a 25 Mw Kaplan unit[J]. International Journal on Hydropower and Dams, 2003, 10(3): 84–88.
CHEN G. Q. Operation analysis and stabilization measures for the 700Mw Tghp Lb units[C]. Proceedings of the 1st International Conference on Hydropower Technology and Key Equipment. Beijing, China, 2006, 174–179.
SHIRAZI F. A., MAHJOOB M. J. Draft tube surge detection in Francis hydroturbines using bispectrum analysis[C]. Proceedings of the 2007 Ieee International Conference on Mechatronics and Automation. Haerbin, China, 2007, 2077–2081.
SIROK B., BLAGOJEVIC B. and BAJCAR T. et al. Simultaneous study of pressure pulsation and structural fluctuations of a cavitated vortex core in draft tube of a Francis turbine[J]. Journal of Hydraulic Research, 2003, 41(5): 541–548.
WU Yu-lin, WU Xiao-jing and LIU Shu-hong. Correlation analysis of the internal vortex flow of hydro turbine with the pressure fluctuation inside draft tube[J]. Journal of Hydroelectric Engineering, 2007, 26(5):122–127(in Chinese).
QIAN Zhong-dong, YANG Jian-dong and HUAI Wen-xin. Numerical simulation and analysis of pressure pulsation in Francis hydraulic turbine with air 19 admission[J]. Journal of Hydrodynamics, Ser. B, 2007, 19(4): 467–472.
LAI Xi-de. Analysis and estimation of hydraulic stability of Francis hydro turbine[J]. Journal of Hydrodynamics, Ser. B, 2004, 16(2): 194–200.
ZHU Yu-liang, XIONG Hao and XU Dong-hai. Stability analysis on Alstom units installed in Three Gorges Left Bank Hydropower Plant[C]. Proceedings of the 1st International Conference on Hydropower Technology and Key Equipment. Beijing, China, 2006, 1281–1289.
LIAO Cui-lin. Study on hydraulic stability of large Francis turbine[D]. Ph. D. Thesis, Beijing: China Agricultural University, 2008, 61–75(in Chinese).
WANG Fu-jun. Computational fluid dynamics analysis — Cfd principles and application[M]. Beijing: Tsinghua University Press, 2004, 114–126 (in Chinese).
LIU Xiao-Bing, ZENG Yong-Zhong and CAO Shu-You. Numerical prediction of vortex flow in hydraulic turbine draft tube for LES[J]. Journal of Hydrodynamics, Ser. B, 2005, 17(4): 448–454.
WANG Wen-quan, ZHANG Li-xiang and YAN Yan et al. Large-eddy simulation of turbulent flow considering inflow wakes in a Francis turbine blade passage[J]. Journal of Hydrodynamics, Ser. B, 2007, 19(2): 201–209.
WANG Zhen-wei, ZHOU Ling-jiu. Simulations and measurements of pressure oscillations caused by vortex ropes [J]. Journal of Fluids Engineering, Transactions of the ASME, 2006, 128(4): 649–655.
Author information
Authors and Affiliations
Corresponding author
Additional information
Project supported by the National Nature Science Foundation of China (Grant Nos.50779070, 90510007), the Beijing Nature Science Foundation of China (Grant No. 3071002).
Biography: WANG Fu-jun (1964-), Male, Ph. D., Professor
Rights and permissions
About this article
Cite this article
Wang, Fj., Li, Xq., Ma, Jm. et al. Experimental Investigation of Characteristic Frequency in Unsteady Hydraulic Behaviour of a Large Hydraulic Turbine. J Hydrodyn 21, 12–19 (2009). https://doi.org/10.1016/S1001-6058(08)60113-4
Received:
Revised:
Published:
Issue Date:
DOI: https://doi.org/10.1016/S1001-6058(08)60113-4