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Water 2018, 10(7), 881; https://doi.org/10.3390/w10070881

The Tale of an Intake Vortex and Its Mitigation Countermeasure: A Case Study from Akkats Hydropower Station

1
Vattenfall AB Research and Development, Älvkarleby Laboratory, SE-81426 Älvkarleby, Sweden
2
Division of Resources, Energy and Infrastructure, Royal Institute of Technology, SE-10044 Stockholm, Sweden
3
Division of Fluid and Experimental Mechanics, Luleå University of Technology, SE-97187 Luleå, Sweden
*
Author to whom correspondence should be addressed.
Received: 8 May 2018 / Revised: 26 June 2018 / Accepted: 28 June 2018 / Published: 2 July 2018
(This article belongs to the Section Hydraulics)
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Abstract

The upgrade of Akkats power station in Sweden included a new, separate waterway for the addition of a 75 MW generating unit. The vertical intake of its headrace was formed by means of lake tapping. A physical model was used to help understand the blasting process involving fragmented rock, water, air, and gas. Upon commissioning of the unit, swirling flows occurred unexpectedly at the intake, which gave rise to negative consequences including limitations in power output. Echo-sounding showed that the blasted piercing resulted in an irregular intake. A hydraulic model, as part of the design process, was built to examine potential countermeasures for vortex suppression. The final solution was a segmented barrier between the intake and the dam. It effectively suppressed the intake flow circulations; only minor intermittent vortices were left. The fabricated steel segments were anchored into the bedrock, stretching to 1.0 m below the lowest legal reservoir level. The local intake headloss was also reduced. The implemented solution was tested under full turbine loading and the result was satisfactory. Even during winter seasons with ice cover above the wall, the power station ran normally. The case study is expected to provide guidance for solving similar problems with vortex formation. View Full-Text
Keywords: Akkats; intake; lake tapping; swirling flow; vortex suppression; model tests Akkats; intake; lake tapping; swirling flow; vortex suppression; model tests
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Yang, J.; Andreasson, P.; Högström, C.-M.; Teng, P. The Tale of an Intake Vortex and Its Mitigation Countermeasure: A Case Study from Akkats Hydropower Station. Water 2018, 10, 881.

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