Flow Field Measurement at the Distributor of Francis Turbines

Unsteady flow at the stator level in reaction turbines was experimentally investigated in a doctoral project. The goal is to develop an integrated expertise to measure the unsteady flow at the stator level of reaction turbines using PIV and other measurement techniques. In this paper, we present the experimental efforts and results of the flow measurement at the stator level in a model Francis turbine with PIV and miniature pressure sensors. Flow fields between the two neighboring guide vanes are measured with PIV and a specific optical access. Instantaneous results such as velocity vector map and average results such as velocity fluctuation vs. phase angle and velocity magnitude contours were presented. The pressure distribution around the pressure side and suction side of the two neighboring guide vanes was measured with miniature pressure sensors with a specially designed mounting method on the surfaces without any geometry alteration. Static and dynamic pressure distribution and spectral analysis are presented. Based on the measurements, the effects of operation points on the flow behavior are analyzed