LDA measurements in the Francis-99 draft tube cone

27th IAHR Symposium on Hydraulic Machinery and Systems

Sundstrom, L.R.J.^1 ; Amiri, K.^1 ; Bergan, C.^2 ; Cervantes, M.J.^1,2 ; Dahlhaug, O.G.^2

Luleå University of Technology, Luleå, Sweden^1

Norwegian University of Science and Technology, Trondheim, Norway^2

关键词: Best efficiency point;    Dimensionless velocity;    Frequency spectra;    Hydraulic efficiency;    Hydropower plants;    Laser Doppler anemometry;    Rotational speed;    Velocity profiles;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/22/2/022012/pdf
DOI  :  10.1088/1755-1315/22/2/022012

来源: IOP

【 摘 要 】

Velocity measurements were performed in the draft tube cone of a 1:5.1 scaled model of the Tokke hydropower plant, Norway; also known as the Francis-99 model. Results from the laser Doppler anemometry measurements undertaken at three operating points will be used as validation data for an upcoming workshop on the state of the art of Francis turbine numerical simulation. With the turbine operating at the best efficiency point, a sensitivity analysis of the flow parameters head, flow rate and runner rotational speed shows that the effects on the dimensionless velocity profiles are small as long as nEDand QEDare held constant. The results indicate a well-functioning turbine at the best efficiency point and high load. At the part load operating point, a vortex breakdown occurs which distorts the velocity profiles and significantly lowers the turbine's hydraulic efficiency. Frequency spectrums of each LDA signal at part load reveals a peak which is asynchronous to that of the runner angular speed. The peaks might be related to the precession of a rotating vortex rope but the characteristics of the LDA signals are different compared to previous studies involving rotating vortex ropes.