A fluid–structure interaction (FSI) system has been solved using the coupled acoustic structural finite element method (FEM) to simplify the cavitating flow conditions around a hydrofoil. The modes of vibration and the added mass effects have been numerically simulated for various flow conditions including leading edge attached partial cavitation on a two-dimensional NACA0009 hydrofoil. The hydrofoil has been first simulated surrounded by only air and by only water. Then, partial cavities with different lengths have been modeled as pure vapor fluid domains surrounded by the corresponding water and solid domains. The obtained numerical added mass coefficients and mode shapes are in good agreement with the experimental data available for the same conditions. The study confirms that the fluid added mass effect decreases with the cavitation surface ratio (CSR) and with the thickness of the cavitation sheet. Moreover, the simulations also predict slight mode shape variations due to cavitation that have also been detected in the experiments. Finally, the effects of changes in cavity location have been evaluated with the previously validated model.

In order to promote the development of new power systems and the consumption of clean energy, pumped storage hydropower stations tend to become increasingly larger in capacity and higher in head height. In this paper, a three-dimensional model of the full channel of a high-head pump turbine is established, and the influence of the gap thickness between the runner crown and the headcover on the internal flow field characteristics, pressure fluctuation characteristics and axial water thrust are studied by means of computational fluid dynamics (CFD). The results indicate that the area where the pressure and velocity vary greatly in the flow field of the crown clearance is at the seal of the labyrinth ring. In addition, the pressure balance pipe has a greater impact on the pressure and flow rate of the water passing through the clearance, and the crown clearance near the pressure balance pipe generates a vortex, resulting in energy loss. Decreasing the thickness of the clearance has no obvious effect on the pressure on the flow-passing components, and increasing the thickness of the clearance has a great change in the pressure values at the upper crown inlet, in front of the labyrinth ring of the crown and in front of the labyrinth ring of the band. The upper part of the vaneless area, the crown inlet and the lower ring inlet are close to the runner; hence, the interference from the rotating parts is the strongest. The effect of increasing the thickness of the crown clearance on the axial water thrust is greater than that of decreasing the thickness of the crown clearance. The pulsation frequency of the axial thrust on the crown, band and blade and the resultant force of the axial thrust increase with the increase in the crown clearance thickness.

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.

With a large-range-operation head, the Francis turbine unit is the most widely used type of hydraulic turbine in the world. The general range of the Francis turbine is 20–700 m. Because of this, the operating stability of the Francis turbine needs to be focused on. In this paper, a multi-dimensional hill chart is applied to a low-head Francis turbine unit to describe its vibration characteristics. Firstly, a field test was conducted on the unit in order to obtain vibration data under different operating conditions. Secondly, the condition indicators were calculated and extracted from the experimental data. Then, the condition indicators under different head values and outputs were fitted to form a multi-dimensional hill chart. In the end, the vibration characteristics of the researched low-head Francis turbine unit were analyzed based on the multi-dimensional hill chart.