Synthetic Study on Unstable Flow Phenomena in Turbomachineries under Extreme Operating Conditions and the Flow Control and Advance Detection

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The purpose of this research project is to find the guiding principles for developing turbomachineries, which are equipped with active and passive control devices and mechanisms for unstable flow phenomena under extreme operating conditions. As unstable flow phenomena in turbomachineries, the following subjects were focused in this research ; (1) the cavitation induced oscillation in pump-inducers, (2) the positive slope head characterisitics of ultra-low specific speed pump with extremely high pressure, (3) the unsteady characteristics, due to the vortex collapse, of the draft tube for ultra-low head hydro turbine, (4) the dynamic stall behavior of wind turbine blade under the extreme wind flow conditions and (5) Pressure fluctuations, due to the rotor/stator flow interaction, in diffuser pumps.. As these unstable flow behaviors might occur the shaft vibration, in addition of the above, the subject on the stable control of shaft vibration and the performance of sliding bearings under ultra-high speed shaft rotating conditions was also picked up. These researches ware carried out in each individual laboratory and the results were discussed together from the synthetic standpoint. Then, the flow mechanisms of unstable behaviors due to cavitation, stall, swirling vortex and blade-rows interaction were clarified and the useful information for the design and operation of turbomachineries to control and detect the unstable behaviors in advance.