Flow Stability Analysis of High-head Reversible Hydro-turbine Under No-load Conditions
The synchronization performance and operating stability of the pump-turbine are closely related to the operating status during no-load conditions.A domestic high-head pump-turbine was selected in this paper so as to probe into the stability problems under special working conditions.So the particular flow phenomena of the unit with three different guide vanes openings under no-load conditions were simulated and analyzed pursuant to the inner flow characteristics and pressure fluctuation rules.Based on the comparison and verification of characteristic curves,the calculation results show that:under no-load conditions,the vortex distribution inside the runner gradually develops from the suction to pressure side during the change of guide vanes opening from small to large.Due to the broken flow symmetry,the rotating stall is more obvious with the large opening,and the combined action of rotor-stator interaction leads to the maximum amplitude of the pressure pulsation at the downstream channel near the runner inlet.Therefore,it's necessary to avoid the unit running under no-load conditions with large opening for a long time,and pay attention to the structural stress distribution of downstream side near the runner inlet during maintenance and overhaul.
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