In this study, a series of field experiments are carried out on hydro-turbine unit 1 and unit 5, respectively, in Goupitan hydropower plant to solve the problems such as too large vibration acceleration in unit 1, vibration and hydraulic instability in unit 5 at high flow rates. In the prototype experiments, an advanced data acquisition software LabVIEW and a testing program proposed by NI Hardware are adopted. The experimental results are processed and the reasons for the instability are inferred; subsequently, several measures are proposed, implemented and validated experimentally. It is confirmed that for unit 1 once the runner nut is changed into a cone from the original cylinder the severe pressure pulsation phenomenon disappears at high flow rates. For unit 5, however, even though the thickness of the trailing edge of wicket gate foils has been reduced, the severe pressure pulsation also persists, suggesting Karman vortex street is irresponsible for this effect. This outcome has a referential significance for safe operation of hydro-turbine units in a hydropower plant.
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