Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/2422
標題: Francis水輪機尾管穴蝕特性之研究
Study on Cavitation Characteristics in Francis Turbine Draft-Tube
作者: 余培華
Yih, Per-Wha
關鍵字: hydraulic turbine;水輪機;cavitation;spectra;穴蝕;頻譜
出版社: 機械工程學系所
引用: 參考文獻 1.F. Avellan“Introduction To Cavitation In Hydraulic Machinery” The 6th International Conference on Hydraulic Machinery and Hydrodynamics Timisoara, Romania, October 21 - 22, 2004. 2.B. Bajic, and A. Keller, "Spectrum Normalization Method in Vibro-Acoustical Diagnostic Measurements of Hydroturbine Cavitation", Journal of Fluids Engineering, Vol. 118, No. 4, 1996, pp. 756-761. 3.C. E. Brennen, Cavitation And Bubble Dynamics, Oxford University Press,Pasadena,California,1995. 4.C. E. Brennen,”Hydrodynamics of Pumps”, Oxford University Press,Pasadena,California,1994. 5.X. Escaler, E. Egusquiza, M. Farhat,F. Avellan, M. Coussir” Detection of Cavitation in Hydraulic Turbines” Mechanical Systems and Signal Processing 20 (2006) 983–1007. 6.X. Escaler, E. Egusquiza, M.Farhat ,P. Ausoni, F. Avellan, M. Coussir”Cavitation Monitoring of Hydroturbines:Test in a Francis Turbine Model”Sixth International Symposium on Cavitation 006, Netherland, Sep. 2006. 7.M.S.Iliescu, G.D. Ciocan, F. Avellan “Analysis of the Cavitating Draft Tube Vortex in a Francis Turbine Using Particle Image Velocimetry Measurements in Two-Phase Flow” Journal of Fluids Engineering ,Feb.2008, Vol. 130 / 021105-1. 8.S. Liu , L. Zhang , M. Nishi , Y. Wu “Cavitating Turbulent Flow Simulation in a Francis Turbine Based on Mixture Model” Journal of Fluids Engineering ,MAY. 2009, Vol.131/051302-1. 9.C. Nicolet, J.-J. Herou, B. Greiveldinger, P. Allenbach,J.-J. Simond, F. Avellan” Methodology for Risk Assessment of Part Load Resonance in Francis Turbine Power Plant”IAHR Int. Meeting of WG on Cavitation and Dynamic Problems in Hydraulic Machinery and Systems ,Barcelona, 28-30 June 2006. 10.F. A. Shirazi and M. J. Mahjoob “Draft Tube Surge Detection in Francis Hydroturbines Using Bispectrum Analysis” Proceedings of the 2007 IEEE International Conference on Mechatronics and Automation August 5 - 8, 2007, Harbin, China. 11.R. Zhang,F. Mao, J.Z. Wu , S.Y. Chen, Y.L. Wu,S.H. Liu ,“Characteristics and Control of the Draft-Tube Flow in Part-Load Francis Turbine”Journal of Fluids Engineering" Feb. 2009, Vol. 131 / 021101-1. 12.廖偉麗, ”水輪機主軸中心孔補氣對尾水管內部流態的影響”水利學報, 2008 年 8月,1005-7. 13.王正傳,流體機械基礎,清華大學出版社,北京, 2006. 14.李太保,計算聲學聲場的方程和計算方法,科學出版社北京, 2003. 15.徐科軍, 信號分析處理, 第1版, 清華大學出版社,北京, 2005. 16.程正興,小波與小波變換導論,機械工業出版社,北京, 2007. 17.鄭源,張強,水電站動力設備,中國水力水電出版社,北京, 2003. 18.李文廣,水力機械流動理論,中國石化出版社,北京, 2000. 19.台灣電力公司新天輪工程竣工圖面及測試報告,台灣,1994. 20.台灣電力公司馬鞍機組竣工圖面及測試報告,台灣,1997. 21.台灣電力公司卓蘭機組竣工圖面及測試報告,台灣,2000.
摘要: 
摘要
本文主要是研究水輪機組尾管穴蝕的現象。安裝加速度規在一部出力67MW及另一部105MW的原型Francis水輪機組尾管人孔上方,分別在10個特定負載量進行振動訊號的量測,振動訊號均以FFT轉換頻譜;另以小波變換解析馬鞍機組時頻訊號,研究尾管穴蝕特性。另整理、分析水輪機峻工試驗、模型試驗、尾管水壓及電力脈動等測試報告,輔助說明量測結果。
研究結論為:(1)尾管穴蝕是由動輪葉尾流區的3個特徵結構產生,分別是:在低負載是大量的氣泡、在中負載是卡氏渦漩、在高負載時無明顯穴蝕現象,3者的頻率特徵均集中於3KHz,頻寬分佈在1KHz~5KHz之間;(2)在300Hz~500Hz有明顯且集中的訊號,推論是由動輪葉出口壓力脈動產生的週期訊號。(3)在40%~80%負載出力時,尾管渦帶的壓力脈動最嚴重;(4)經由中空軸的補氣機構,改變進氣量及補氣管長度可以降低渦帶的強度,但也因進氣量及補氣位置改變使低載穴蝕的強度增加。動輪冠下方安裝補氣管可以改善低載穴蝕,但會造成尾管流場紊亂,而且補氣管的尾流區產生嚴重的渦流及穴蝕。
關鍵字:水輪機、穴蝕、頻譜

Abstract
This study focuses on the cavitation detection in the draft tube of hydraulic turbines. One seismic transducers is installed on the 67MW and the other on the draft tube of a 105MW prototype Francis turbine to measure the structural vibration for ten varying loads. The signal is proceses via FFT and wavelet to analyze the spectra and the time-frequency characteristics. In additions, sorting the data from new Tienlun、Maan and Shihlin hydropower test records of Taiwan power company can help to illustrate the experimental results.
The experimental results show that:(1)The cavitation detected in the draft tube is caused by three different flow conditions from the runner impeller outlet. While the machine operates at low load , massive bubbles are produced. The Karman vortex cavitation is formed when operated at the middle load the middle load.And at high load, no obvious cavitation is observed. Their characteristic frequencies are concentrated around 3KHz with a frequency band ranging within 1 KHz ~5 KHz.(2)The signal frequency ranged within 300Hz~500 Hz is probably caused by the period pressure pulse induced at the runner outlets.(3)when operating around 40%~80% full load ,the period pressure pulse is significantly induced by the swirl at draft tube.(4)Not only the amount of purged air and the length of air-supply pipe can leviate the strength of swirl at the draft tube.Meanwhile but they will also lead to series cavitation at low loads, .On the other hand, if the air-supply pipe is stalled below the runner cone, the cavitation at the low load will be largely improved.However this will also induce the more turbulent flow in draft tube,which may cause serious vortex and cavitation in the wake of the air- supply pipe.

Keywords:hydraulic turbine , cavitation , spectra
URI: http://hdl.handle.net/11455/2422
其他識別: U0005-0906201013273700
Appears in Collections:機械工程學系所

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