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

• Published in: Water (Basel) Vol. 11; no. 12; p. 2554
• Main Authors: Kim, Seung-Jun, Suh, Jun-Won, Choi, Young-Seok, Park, Jungwan, Park, No-Hyun, Kim, Jin-Hyuk
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.12.2019
• Subjects: Aerodynamics; Alternative energy sources; Analysis; Cavitation; Computational fluid dynamics; Computer software industry; Draft tubes; Energy resources; Energy sources; Finite volume method; Flow characteristics; Flow distribution; Flow rates; Flow velocity; Fluid flow; Investigations; Low flow; Multiphase flow; Numerical analysis; Power plants; Power supply; Pumped storage; Renewable resources; Rope; Shear stress; Sustainable yield; Three dimensional flow; Turbines; Turbulence models; Turbulent flow; Two phase flow; Visualization; Vortices; United States; South Korea
• ISSN: 2073-4441; 2073-4441
• DOI: 10.3390/w11122554

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.