Experimental investigation of the draft tube inlet flow of a bulb turbine

27th IAHR Symposium on Hydraulic Machinery and Systems

Vuillemard, J.^1 ; Aeschlimann, V.^1 ; Fraser, R.^1 ; Lemay, S.^1 ; Deschênes, C.^1

Hydraulic Machine Laboratory (LAMH), Laval University, Department of Mechanical Engineering, Pavillon Adrien-Pouliot, QC

G1V 0A6, Canada^1

关键词: Circumferential velocity;    Experimental database;    Experimental investigations;    Indirect measurements;    Laser Doppler Velocimetry;    Operating condition;    Phase-averaged velocity;    Velocity gradients;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/22/3/032010/pdf
DOI  :  10.1088/1755-1315/22/3/032010

来源: IOP

【 摘 要 】

In the BulbT project framework, a bulb turbine model was studied with a strongly diverging draft tube. At high discharge, flow separation occurs in the draft tube correlated to significant efficiency and power drops. In this context, a focus was put on the draft tube inlet flow conditions. Actually, a precise inlet flow velocity field is required for comparison and validation purposes with CFD simulation. This paper presents different laser Doppler velocimetry (LDV) measurements at the draft tube inlet and their analysis. The LDV was setup to measure the axial and circumferential velocity on a radius under the runner and a diameter under the hub. A method was developed to perform indirect measurement of the mean radial velocity component. Five operating conditions were studied to correlate the inlet flow to the separation in the draft tube. Mean velocities, fluctuations and frequencies allowed characterizing the flow. Using this experimental database, the flow structure was characterized. Phase averaged velocities based on the runner position allowed detecting the runner blade wakes. The velocity gradients induced by the blade tip vortices were captured. The guide vane wakes was also detected at the draft tube inlet. The recirculation in the hub wake was observed.