Investigation of Channel Vortices in Francis Turbines

28th IAHR symposium on Hydraulic Machinery and Systems

Liu, M.^1 ; Zhou, L.J.^1 ; Wang, Z.W.^2 ; Liu, D.M.^3 ; Zhao, Y.Z.^3

College of Water Conservancy and Civil Engineering, China Agriculture University, Beijing

100083, China^1

Department of Thermal Engineering, Tsinghua University, Beijing

100084, China^2

Research and Test Center Dongfang Electrical Machine, Dongfang Electrical Machinery Co. Ltd, Sichuan

618000, China^3

关键词: Draft tubes;    Main frequency;    Pressure pulsation;    Reversed flow;    Rotating frequencies;    Suction side;    Vortex rope;    Wideband spectrum;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/49/8/082003/pdf
DOI  :  10.1088/1755-1315/49/8/082003

来源: IOP

【 摘 要 】

In this paper the characteristics of one type of channel vortex and the effect of different parameters on this channel vortex have been investigated experimentally with the aid of high speed photography. The results show that locations of the channel vortices move from near the hub down to near the band with the increase n11or the decrease Q11Meanwhile, with the decrease of Q11or σ channel vortices become thicker with increasing appearing frequency. When the channel vortices come out near the hub or in the middle of the blade at low or moderate n11, the main frequency of pressure pulsation in the draft tube is the swirling frequency of vortex rope. However when the channel vortices come out near the band at high n11, the pressure pulsation in the draft tube has a wide-band spectrum with the frequency within 0.7∼1fn(rotating frequency). Then detailed numerical simulations were carried out to investigate the observed phenomenon. The results reveal this channel vortex is caused by the reversed flow in the draft tube. The mechanism is that channel vortices are induced when the reversed fluid flows up along the suction side of the blade and meets the upstream main flow.