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Open AccessArticle

Runner Lifting-Up during Load Rejection Transients of a Kaplan Turbine: Flow Mechanism and Solution

1
State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China
2
Construction Management Company for Chushandian Reservoir Project of Henan Province, Zhengzhou 450000, China
*
Author to whom correspondence should be addressed.
Energies 2019, 12(24), 4781; https://doi.org/10.3390/en12244781
Received: 18 October 2019 / Revised: 10 December 2019 / Accepted: 12 December 2019 / Published: 15 December 2019
(This article belongs to the Section Sustainable Energy)
Dangerous runner lifting-up (RLU) accidents regarding Kaplan turbines, which are widely used in low-head hydropower stations, were frequently reported. Three-dimensional (3D) computational fluid dynamics (CFD) was used to simulate the load rejection transients with guide-vane closing to predict the RLU possibility of the fixed-blade Kaplan turbine in an under-construction hydropower station. It was found that using any linear closing rule, the upward axial water force on the runner was larger than the weight of rotating parts that started before the guide-vanes were closed, which indicated a RLU possibility. It was the pumping effect that caused the imbalance, during which the high rotational speed runner propels water downstream with a low discharge. We proposed a piecewise closing rule based on this finding. By keeping the opening unchanged in a period in the closing process, the rotational speed can be reduced by using the braking effect, and the concurrence of high speed and low discharge can be prevented. Simulations verified this effective measure and accepted by the manufacturer. Although this study used a fixed-blade Kaplan turbine, the revealed mechanism and verified solution to the RLU problem have reference value for all of the Kaplan turbines. View Full-Text
Keywords: Kaplan turbine; load rejection transients; runner lifting-up; CFD simulation; flow patterns Kaplan turbine; load rejection transients; runner lifting-up; CFD simulation; flow patterns
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MDPI and ACS Style

Liu, K.; Yang, F.; Yang, Z.; Zhu, Y.; Cheng, Y. Runner Lifting-Up during Load Rejection Transients of a Kaplan Turbine: Flow Mechanism and Solution. Energies 2019, 12, 4781.

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