Pump-turbines experience complex flow phenomena and fluid–structure interactions during transient operations, which can significantly impact their stability and performance. This paper presents a comprehensive field test study of the pump mode startup process for a 150 MW prototype pump-turbine. By analyzing pressure fluctuations, structural vibrations, and their short-time Fourier transform (STFT) results, multiple stages were identified, each exhibiting distinct characteristics. These characteristics were influenced by factors such as runner rotation, free surface sloshing in the draft tube, and rotor–stator interactions. The natural frequencies of the metallic components varied during the speed-up and water-filling stages, potentially due to gyroscopic effects or stress-stiffening phenomena. The opening of the guide vanes and dewatering valve inside the guide vanes significantly altered the amplitude of the rotor–stator interaction frequency, transitioning the vibration behavior from forced to self-excited regimes. Interestingly, the draft tube pressure fluctuations exhibited sloshing frequencies that deviated from existing prediction methods. The substantial phenomena observed in this study can help researchers in the field to deepen the understanding of the complex behavior of pump-turbines during transient operations and identify more meaningful research directions.

The pumped-storage power station needs to adjust the load to meet the needs of the power grid at any time and cannot always operate under the best working conditions. In practical operation, vibration phenomenon with complex inducements occasionally occurs. In the stable operation of the Baishan energy storage power station, the headcover vibrates obviously. To find the cause of vibration, this paper modeled the unit flow area, used the numerical simulation method for steady and unsteady calculation, extracted the pressure fluctuation information in the flow field, and then analyzed the possibility of strong vibration caused by the instability of the flow field. The results show that there is a low frequency component of pressure fluctuation caused by the spiral motion of the fluid in the sealing groove in the upper canopy clearance flow, which may be the inducer of the vibration of the headcover.

In practical operation, pump turbines typically operate far from their designed working points, which has a significant impact on the stability of the unit’s operation. In this paper, we conducted a field test to investigate the stability characteristics of prototype pump turbines at different working points. By adjusting the given power of the generator in a stepwise manner to control its working point, we obtained the statistical and spectral characteristics of pressure signals and acceleration signals. In turbine mode, the result shows that, at low, medium, and high power, the variation in pressure fluctuation characteristics is influenced by three different factors, while vibration generally reaches its maximum value at approximately 50 MW. In pump mode, variations in pressure were observed among different measurement points in the low-frequency range, and the characteristics of vibration acceleration were influenced by both the rotor–stator interaction (RSI) and the structural modal frequencies. We emphasized that the high-frequency bands have influences on the unit comparable in magnitude to those of the rotor–stator interaction, which has rarely been mentioned in previous studies. Through detailed testing and analysis of the unit’s actual operation, we can gain a better understanding of its behavior and performance in the turbine and pump modes, and these results hold significant importance for ensuring the stability and reliability of the unit.

With the requirement of flexible operation of hydraulic turbine units, Francis turbine units have to adjust their output into extended operating ranges in order to match the demand of the power grid, which leads to more off-design conditions. In off-design conditions, hydraulic excitation causes excessive stress, pressure pulsation, and vibration on the machines. Different designs of Francis turbines cause different hydraulic excitations and vibrational behaviors. To conduct better condition monitoring and fault prognosis, it is of paramount importance to understand the vibrational behavior of a machine. In order to reveal the influence factors of the vibration behavior of Francie turbine units, field tests have been conducted on two similar-designed Francis turbine units and vibration features have been compared in this research. The vibrational behavior of two Francis turbine units installed in the same power station is compared under extended operating condition. Field tests have been performed on the two researched units and the vibration has been compared using the spectrum analysis method. The vibration indicators are extracted from the test data and the variation rules have been compared. By comparing the vibration behavior of the two machines, the design and installation difference of the two machines have been analyzed. This research reveals the effects of different designs and installations of Francis turbines on the vibration performance of the prototype units. The obtained results give guidance to the designers and operators of Francis turbine units.

Kaplan turbines are generally used in working conditions with a high flow and low head. These are a type of axial-flow hydro turbine that can adjust the opening of the guide vanes and blades simultaneously in order to achieve higher efficiency under a wider range of loads. Different combinations of the opening of the guide vanes and blades (cam relationship) will lead to changes in the efficiency of the turbine unit as well as its vibration characteristics. A bad cam relationship will cause the low efficiency or unstable operation of the turbine. In this study, the relative efficiency and vibration of a large-scale Kaplan turbine with 200 MW output were tested with different guide vane and blade openings. The selection of the cam relationship curve for both optimal efficiency and optimal vibration is discussed. Compared with the cam relationship given by the model test, the prototype cam relationship improves the efficiency and reduces the vibration level. Compared to the optimal efficiency cam relationship, the optimal vibration cam relationship reduces the efficiency of the machine by 1% to 2%, while with the optimal efficiency cam relationship, the vibration of the unit increases significantly. This research provides guidance for the optimization of the regulation of a large adjustable-blade Kaplan turbine unit and improves the overall economic benefits and safety performance of the Kaplan turbine power station.