Numerical Analysis of the Transient Behaviour of a Variable Speed Pump-Turbine during a Pumping Power Reduction Scenario
2. Numerical Model
3.1. Validation of Numerical Model under Constant Flow Rate Conditions
3.2. Numerical Analysis of the Pump-Turbine in a Power Reduction Scenario
- During the beginning of the power reduction process, the vortex, partially blocking the regular flow, moves from one channel to the subsequent one in the runner rotation direction with increasing intensity during the load rejection. Each steady channel alternates partial blocked flow according to the rotation frequency of the stall cell. The unsteady pattern in return channel strengthened, emphasizing its characteristic frequency with the rotational velocity decreasing, reaching a maximum and then disappearing. During this phase, the variation of force and torque on wicket gate pins is moderate.
- For lower rotational speed, the periodic flow oscillation inside the return channels disappeared. The flow field into the wicket gates channel start to manifest a full three-dimensional flow structure. The path analyses show that only the vortexes with intensity and structure changed stochastically. Hence, the fluctuations of pressure and torque for different monitoring points show relatively low variation.
- Close to the end of the power reduction process, serious fluctuations of both pressure and velocity could be observed, and the highest level occurs in the stay vanes showing a rotating stall. The parameters show serious fluctuations of torque and force on the guide vanes.
Conflicts of Interest
|B||Impeller or guide vane or return channel width||m|
|Gxx||Power spectra|| 2|
|n||Rotational speed of the impeller||rpm|
|nb||Impeller number of blades||-|
|nbR||Return Vane number of blades||-|
|nbW||Wicket Guide number of blades||-|
|Pressure averaged along the time||Pa|
|Blade Passage Frequency||Hz|
|λ||Guide vanes’ azimuthally position||degree|
|ω||Angular rotational velocity||rad·s−1|
Pumped Hydro Energy Storage
Computational Fluid Dynamics
Best Efficiency Point
Blade Passage Frequency
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|D2 (mm)||B2 (mm)||nb||β2b (°)||φDes|
|Wicket Guide Data|
|D3 (mm)||B3 (mm)||nbW||α3b (°)||λ (°)|
|410||40||22||10 ÷ 30||−8 ÷ 8|
|Return Channel Vanes Data|
|D4 (mm)||B4 (mm)||nbR||α4b (°)|
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Pavesi, G.; Cavazzini, G.; Ardizzon, G. Numerical Analysis of the Transient Behaviour of a Variable Speed Pump-Turbine during a Pumping Power Reduction Scenario. Energies 2016, 9, 534. https://doi.org/10.3390/en9070534
Pavesi G, Cavazzini G, Ardizzon G. Numerical Analysis of the Transient Behaviour of a Variable Speed Pump-Turbine during a Pumping Power Reduction Scenario. Energies. 2016; 9(7):534. https://doi.org/10.3390/en9070534Chicago/Turabian Style
Pavesi, Giorgio, Giovanna Cavazzini, and Guido Ardizzon. 2016. "Numerical Analysis of the Transient Behaviour of a Variable Speed Pump-Turbine during a Pumping Power Reduction Scenario" Energies 9, no. 7: 534. https://doi.org/10.3390/en9070534