2025
Shen, Jiawei; Pei, Ji; Wang, Wenjie; Yuan, Shouqi; Pavesi, Giorgio
In: Renewable Energy, vol. 253, 2025, ISSN: 18790682.
Abstract | Links | BibTeX | Tags: Acceleration transition process, Flow instability, High-efficiency operation, Micro-pumped hydro storage, Reversible mixed-flow pump, Variable-speed regulation
@article{Shen2025,
title = {Broader high-efficiency zone of micro-pumped hydro storage enabled by a variable-speed reversible mixed-flow pump: Taking acceleration as an example},
author = {Jiawei Shen and Ji Pei and Wenjie Wang and Shouqi Yuan and Giorgio Pavesi},
doi = {10.1016/j.renene.2025.123642},
issn = {18790682},
year = {2025},
date = {2025-01-01},
journal = {Renewable Energy},
volume = {253},
publisher = {Elsevier Ltd},
abstract = {Given the burgeoning renewables-based microgrids, it is crucial for a stable power supply to enable more flexible micro-pumped hydro storage by the reversible mixed-flow pump (RMFP) with a broad high-efficiency zone (HEZ). Variable-speed operation is the most effective method to regulate operating conditions for scenarios of the RMFP without the guide vane. To reveal the effect of variable-speed regulation on the HEZ, we test the energy characteristics of RMFP at four speeds based on a bidirectional hydraulic test bench. The experiment shows that the RMFP receives an HEZ that is expanded by 53.4 % in pump mode and 60.3 % in turbine mode by accelerating from 830 r/min to 980 r/min. Moreover, the transition process of the acceleration regulation under full load is simulated based on a validated CFD numerical scheme. It is indicated that the acceleration regulation not only improves the efficiency and hydraulic dissipation but also alleviates the flow instabilities. The peak-to-peak value and the amplitude of the dominant frequency of the pressure fluctuation in the runner can be reduced by up to 49.4 % and 46.2 %, respectively. This study highlights the broad high-efficiency zone and stable internal flow that variable-speed regulation contributes to the RMFP, aiming at enhancing the flexibility of micro-pumped hydro storage.},
keywords = {Acceleration transition process, Flow instability, High-efficiency operation, Micro-pumped hydro storage, Reversible mixed-flow pump, Variable-speed regulation},
pubstate = {published},
tppubtype = {article}
}
Given the burgeoning renewables-based microgrids, it is crucial for a stable power supply to enable more flexible micro-pumped hydro storage by the reversible mixed-flow pump (RMFP) with a broad high-efficiency zone (HEZ). Variable-speed operation is the most effective method to regulate operating conditions for scenarios of the RMFP without the guide vane. To reveal the effect of variable-speed regulation on the HEZ, we test the energy characteristics of RMFP at four speeds based on a bidirectional hydraulic test bench. The experiment shows that the RMFP receives an HEZ that is expanded by 53.4 % in pump mode and 60.3 % in turbine mode by accelerating from 830 r/min to 980 r/min. Moreover, the transition process of the acceleration regulation under full load is simulated based on a validated CFD numerical scheme. It is indicated that the acceleration regulation not only improves the efficiency and hydraulic dissipation but also alleviates the flow instabilities. The peak-to-peak value and the amplitude of the dominant frequency of the pressure fluctuation in the runner can be reduced by up to 49.4 % and 46.2 %, respectively. This study highlights the broad high-efficiency zone and stable internal flow that variable-speed regulation contributes to the RMFP, aiming at enhancing the flexibility of micro-pumped hydro storage.
2015
Pavesi, Giorgio; Yang, Jun; Cavazzini, Giovanna; Ardizzon, Guido
Experimental analysis of instability phenomena in a high-head reversible pump-turbine at large partial flow condition Proceedings Article
In: 11th European Conference on Turbomachinery Fluid Dynamics and Thermodynamics, ETC 2015, pp. 1-2, euroturbo.eu, 2015, ISSN: 24104833.
Abstract | Links | BibTeX | Tags: Flow instability, Francis Turbine, Francis-type Reversible Turbine, Hump instability, PAT, Pump as Turbine
@inproceedings{pop00010,
title = {Experimental analysis of instability phenomena in a high-head reversible pump-turbine at large partial flow condition},
author = {Giorgio Pavesi and Jun Yang and Giovanna Cavazzini and Guido Ardizzon},
url = {http://www.euroturbo.eu/paper/ETC2015-060.pdf},
issn = {24104833},
year = {2015},
date = {2015-01-01},
urldate = {2015-01-01},
booktitle = {11th European Conference on Turbomachinery Fluid Dynamics and Thermodynamics, ETC 2015},
pages = {1-2},
publisher = {euroturbo.eu},
abstract = {Growing environmental concerns, and the need for better power balancing and frequency control have increased attention in renewable energy sources, such as, the reversible pump-turbine which can provide both power generation and energy storage. Pump-turbine operation along the hump-shaped curve can lead to unusual increases in water pressure pulsations, which lead to machine vibrations. Measurements of wall pressure in the stators were performed together with high-speed flow visualizations. Starting from the best efficiency point (BEP) and by decreasing the flowrate, a significant increase of the pressure fluctuations was observed mainly in the wicket gates channels. The analyses in frequency and time-frequency domains showed a rise of low frequency components. High-speed movies revealed a quite uniform flow pattern in the guide vanes channels at the normal operating range, whereas, the flow was highly disturbed by rotating stall passage at part load. The situation was more critical in the dump flow rate range, where backflow and vortices in the guide vanes channels developed during the stall cell passage.},
keywords = {Flow instability, Francis Turbine, Francis-type Reversible Turbine, Hump instability, PAT, Pump as Turbine},
pubstate = {published},
tppubtype = {inproceedings}
}
Growing environmental concerns, and the need for better power balancing and frequency control have increased attention in renewable energy sources, such as, the reversible pump-turbine which can provide both power generation and energy storage. Pump-turbine operation along the hump-shaped curve can lead to unusual increases in water pressure pulsations, which lead to machine vibrations. Measurements of wall pressure in the stators were performed together with high-speed flow visualizations. Starting from the best efficiency point (BEP) and by decreasing the flowrate, a significant increase of the pressure fluctuations was observed mainly in the wicket gates channels. The analyses in frequency and time-frequency domains showed a rise of low frequency components. High-speed movies revealed a quite uniform flow pattern in the guide vanes channels at the normal operating range, whereas, the flow was highly disturbed by rotating stall passage at part load. The situation was more critical in the dump flow rate range, where backflow and vortices in the guide vanes channels developed during the stall cell passage.
