A comparative study of the scale effect on the s-shaped characteristics of a pump-turbine unit

Jun Won Suh, Seung Jun Kim, Hyeon Mo Yang, Moo Sung Kim, Won Gu Joo, Jungwan Park, Jin Hyuk Kim, Young Seok Choi

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)


S-shaped characteristics in turbine mode are prone to instabilities in associated transient processes. A single value of the speed factor corresponds to multiple values of the discharge factor, having the possibility of changing the operating point among the turbine, turbine brake, and reverse pump modes. Because of this characteristic, the S-shaped curves induce instability in transient processes. Understanding the hydraulic behavior of a turbine on the four-quadrant characteristic is important since it provides detailed performance information through the whole discharge range of the turbine. This study was numerically and experimentally investigated the scale effect on the S-shaped characteristics in the turbine transition region. The four-quadrant characteristic curves (full-and laboratory-scale) in the turbine mode were predicted by numerical simulations. To verify the predicted results, a laboratory-scale experiment was performed in the turbine, turbine brake, and reverse pump modes. Although the full-scale experiment was performed in the normal operating head range, the scale effect can be validated by comparing steady operating points between the two models. Based on the verified results, the internal flow and pressure pulsation characteristics were determined at the operating point in a specific transition region.

Original languageEnglish
Article number525
Issue number3
Publication statusPublished - 2021 Feb 1

Bibliographical note

Funding Information:
Funding: This work was supported by Korea Hydro & Nuclear Power Co., Ltd. (No. 2017-Tech-16). The authors are grateful for this support.

Publisher Copyright:
© 2021 by the authors. Licensee MDPI, Basel, Switzerland.

All Science Journal Classification (ASJC) codes

  • Renewable Energy, Sustainability and the Environment
  • Fuel Technology
  • Energy Engineering and Power Technology
  • Energy (miscellaneous)
  • Control and Optimization
  • Electrical and Electronic Engineering


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