Extending the operating range of axial turbines with the protrusion of radially adjustable flat plates: An experimental investigation

Shahab Shiraghaee, Joel Sundström, Mehrdad Raisee and Michel J. Cervantes

Renewable Energy, 2024, vol. 225, issue C

Abstract: The implementation of hydropower to stabilize electrical grids dictates more frequent off-design operations of these renewable energy resources. Flow instabilities under such conditions reduce the efficiency of hydro turbines. Part-load operation is particularly detrimental since the development of a rotating vortical structure termed rotating vortex rope (RVR) in the draft tube leads to periodic pressure pulsations that jeopardize turbine performance. This paper experimentally explores a novel solution involving the protrusion of flat plates into the turbine draft tube. Three flat plates equally separated by 120° were vertically installed on the draft tube wall. The plates were protruded up to 83% of the draft tube local radius under four different part-load conditions. Their impact was observed through time-resolved pressure measurements in the draft tube and vaneless space, as well as efficiency measurements. The results demonstrated successful RVR mitigation, achieving a maximum 85% reduction in pressure oscillation amplitudes. Protruding flat plates disrupted RVR periodicity and coherence, confining its orbit to the draft tube center. This approach proved particularly effective at lower part-load conditions, enhancing turbine hydraulic efficiency by increasing torque extraction. Reducing the adverse effects under part load, the proposed method appears promising in extending the operational range of hydraulic turbines.

Keywords: Hydropower; Part-load; Rotating vortex rope; Turbine efficiency; Pressure measurement; Vortex rope mitigation (search for similar items in EconPapers)
Date: 2024
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Persistent link: https://EconPapers.repec.org/RePEc:eee:renene:v:225:y:2024:i:c:s0960148124002970

DOI: 10.1016/j.renene.2024.120232

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