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Open AccessArticle

Inter-Blade Vortex and Vortex Rope Characteristics of a Pump-Turbine in Turbine Mode under Low Flow Rate Conditions

1
Industrial Technology (Green Process and Energy System Engineering), Korea University of Science & Technology, Daejeon 34113, Korea
2
Thermal & Fluid System R&D Group, Korea Institute of Industrial Technology, Cheonan 31056, Korea
3
Hydropower Design & Technology Group, Korea Hydro & Nuclear Power Co. Ltd, Daejeon 34101, Korea
4
Kumsung Engineering & Construction Co. Ltd, Nonsan 33020, Korea
*
Author to whom correspondence should be addressed.
Water 2019, 11(12), 2554; https://doi.org/10.3390/w11122554
Received: 2 October 2019 / Revised: 24 November 2019 / Accepted: 1 December 2019 / Published: 3 December 2019
(This article belongs to the Section Hydraulics)
Pump-turbines are often used to provide a stable power supply with a constant frequency in response to intermittent renewable energy resources. However, existing pumped-storage power stations often operate under off-design conditions because of the increasing amounts of inconsistent renewable resources that have been added to the grid. Under off-design low flow rate conditions, inter-blade vortex and vortex rope phenomena usually develop in the runner and draft tube passages, respectively, in turbine mode. These vortices cause complicated flow patterns and pressure fluctuations that destabilize the operation of the pump-turbine system. Therefore, this study investigates the influence of correlation between the inter-blade vortex and vortex rope phenomena under low flow rate conditions. Three-dimensional steady- and unsteady-state Reynolds-averaged Navier–Stokes equations were calculated with a two-phase flow analysis using a shear stress transport as the turbulence model. The inter-blade vortices in the runner passages were captured well at the low flow rate conditions, and the vortex rope was found to develop within a specific range of low flow rates. These vortex regions showed a blockage effect and complicated flow characteristics with backflow in the passages. Moreover, higher unsteady pressure characteristics occurred at locations where the vortices were especially pronounced.
Keywords: pump-turbine; turbine mode; inter-blade vortex; vortex rope; internal flow characteristics; unsteady pressure pump-turbine; turbine mode; inter-blade vortex; vortex rope; internal flow characteristics; unsteady pressure
MDPI and ACS Style

Kim, S.-J.; Suh, J.-W.; Choi, Y.-S.; Park, J.; Park, N.-H.; Kim, J.-H. Inter-Blade Vortex and Vortex Rope Characteristics of a Pump-Turbine in Turbine Mode under Low Flow Rate Conditions. Water 2019, 11, 2554.

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