Abstract
Vortex rope patterns at different load of hydro turbine model
Highlights
The integration of new energy sources into the existing electrical grid requires the expansion of hydraulic turbine operating range
Precession frequency registered by high-speed visualization technique at S = 0.45 is higher than at S = 1.2
Fernandes et al showed that there was critical swirl number below which the precession frequency increased with swirl number decreasing while the stable precessing vortex core (PVC) existed
Summary
The integration of new energy sources into the existing electrical grid requires the expansion of hydraulic turbine operating range. When the output flowrate of turbine is changed to execute the regulation function a residual swirl at the draft tube inlet remains, that results in emergence of phenomenon known as precessing vortex core (PVC). PVC leads to uneven pressure distribution in the draft tube that decreases the hydro turbine efficiency and safety. Depending on the turbine discharge relative to the discharge at BEP a number of operating zones are distinguished at which the flow pattern is differed. With discharge decreasing relative to BEP there are upper part load, part load and deep part load. Computational fluid dynamics (CFD) techniques and scaled down experimental modeling significantly enhances the understanding of PVC phenomena in a hydraulic turbine [1,2,3]. CFD requires experimental data for verification but experimental data obtained on scaled model requires a valid theory for interpreting and transferring data to full-scale models that makes experimental modelling of flow structures still highly demanded
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