Renewable Energy Global Innovations features: Design technique to improve the energy efficiency of a counter rotating type pump-turbine

Significance Statement

The development of new renewable energy sources such as wind, hydro and tidal powers and their related studies has been on the raise since the adoption of laws on carbon dioxide which are presently stringent. Great mileage has already been achieved in the exploitation of these noble resources. However, it is difficult to control the amount of energy generated due to the precincts presented by natural conditions. The application of the pump-turbine has emerged as one of the key power stabilization technique that offers the advantages of minimizing energy loss and controlling the power generated. In depth studies have hitherto led to the development of the counter-rotating type pump-turbine which is a novel concept in the field of pump-turbines. Conversely, the energy efficiency of this counter-rotating type pump-turbine calls for thorough design review for its’ maximization since it is characterized by intrinsic internal flow patterns.

With a professor Toshiaki Kanemoto of Kyushu Institute of Technology, Jin-Hyuk Kim and his colleagues at Korea Institute of Industrial Technology proposed a study to address the design scheme in order to improve the energy efficiency of the counter rotating-type pump turbine based on its operating mode. They hoped to achieve this by developing more methodical and rational design techniques that would ensure the improved energy efficiency of the system. The research work is published in Renewable Energy.

First, the research team analyzed the influence of each design variable on the system performance based on the results of the performance evaluation on the test sets, as the regression analysis for the 2^k factorial design was performed. Furthermore, the respective model, whose efficiency was improved according to the operating mode, was then produced. Finally, they evaluated the performance of each generated model using numerical analysis.

The researchers observed that the range of error for numerical analyses and experimental results was smaller hence presenting a high reliability. By employing the design of experiment technique, performance improvement of the counter rotating type pump turbine was observed. The team also observed that the results of the regression analysis in accordance with the implementation of the 2^K factorial design confirmed that those design variables associated with the front runner (four blades) had a significant impact on the performance in the turbine mode. On the other hand those design variables associated with the front impeller (five blades) had a significant impact on the performance in the pumping mode. It was also confirmed that unstable flow components observed in the base model were suppressed through an analysis on the internal flow field. The team agreed that the overall performance of the system improved due to the suppression of these irregular flow components.

Herein, the preliminary design technique with the trade-off relation between both pumping and turbine modes of the counter-rotating type pump-turbine have been presented. A comparison between the standard centrifugal pump-turbine design and the axial type pump-turbine design show that the high specific speed is exceedingly useful in terms of efficiency at especially the condition of high flow rate and low head.Furthermore, the counter-rotating type is possible to make the compact size design in comparison with the general design with the same power, and consequentially is useful for the operation in the region of low head.

About The Author

Jin-Hyuk Kim received his Ph.D. degree in Thermodynamics and Fluid Mechanics at Inha University, Korea, in 2013. He was a postdoctoral researcher in Faculty of Engineering at Kyushu Institute of Technology, Japan, in 2013. He is currently a senior researcher at Korea Institute of Industrial Technology (KITECH) and an assistant professor at University of Science and Technology (UST), Korea.

His research interests are turbo machinery (fans, compressors, pumps, turbines, and pump-turbines) designs and developments; steady and unsteady numerical analyses; optimization methods; flow measurements and experimental techniques.

About The Author

Young-Seok Choi received his B.S. degree from Seoul National University in 1988, and his M.S. and Ph.D in Mechanical Engineering at the same university in 1990 and 1996, Korea, respectively. He is currently a principal researcher in KITECH and a Professor in Advanced Energy & System Technology at the UST (University of Science and Technology). Dr. Choi is a Director of KSFM (Korean Society for Fluid Machinery).

His research interests are turbo machinery (fans, compressors, pumps, turbines, and pump-turbines) designs and developments; steady and unsteady numerical analyses; optimization methods; flow measurements and experimental techniques.

About The Author

Toshiaki Kanemoto received his Doctor of Engineering from Tokyo Metropolitan University, Japan, in 1985. He is currently a research professor in Institute of Ocean Energy at Saga University, Japan, and an Emeritus professor at Kyushu Institute of Technology, Japan, and a consultant professor at South China University of Technology, China, and a visiting professor at Kanagawa University, Japan.

His research interests are turbo machinery (wind power unit, hydroelectric units, ocean stream power units, etc.) designs and developments.

Reference

Joon-Hyung Kim, Bo-Min Cho, Sung Kim, Jin-Woo Kim, Jun-Won Suh, Young-Seok Choi, Toshiaki Kanemoto, Jin-Hyuk Kim. Design technique to improve the energy efficiency of a counter rotating type pump-turbine. Renewable Energy volume 101 (2017) pages 647-659.

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