Numerical and experimental analysis of guide vane pivot torque prediction in the reversible pump-turbine

In the last decades, Computational Fluid Dynamics (CFD) has played an important role in the numerical prediction of different characteristics of all types of hydraulic turbomachinery. Relative results of the characteristics curves for different hydraulic shapes can be predicted very accurately. On the contrary the prediction of the absolute values of various characteristics is still a challenge. In the paper, we would like to present the comparison between the results of the model testing and numerical analysis of the main reversible pump-turbine characteristics in pump and turbine mode: head, torque, efficiency and detailed analysis of prediction of the guide vane pivot torque for various operating regimes. Detailed model reversible pump-turbine measurements were done in hydraulic laboratory according to the international standard IEC 60193. Special attention was paid to the measurements of the guide vane torque. The research results include efficiency and QH curves derived from model tests and numerical analyses across various operating regimes. Dimensionless guide vane pivot torque values from both model tests and numerical analysis are compared and presented in diagram form. The comparison shows good agreement between the model test and CFD results. While steady-state CFD is generally accurate enough for turbine mode operation, unsteady calculations provide better results for pump mode operation. Numerous unsteady CFD analyses in turbine and pump mode operation demonstrate that CFD is equivalent or superior to model test in terms of speed, cost and accuracy. This research establishes that using CFD to predict guide vane pivot torque in hydraulic machines is now the most reasonable approach, eliminating the need for model tests.