Effective hydraulic turbine design prevents sediment and cavitation erosion from impacting the performance and reliability of the machine. Using computational fluid dynamics (CFD) techniques, this study investigated the performance characteristics of sediment and cavitation erosion on a hydraulic Francis turbine by ANSYS-CFX software. For the erosion rate calculation, the particle trajectory Tabakoff–Grant erosion model was used. To predict the cavitation characteristics, the study’s source term for interphase mass transfer was the Rayleigh–Plesset cavitation model. The experimental data acquired by this study were used to validate the existing evaluations of the Francis turbine. Hydraulic results revealed that the maximum difference was only 0.958% compared with the CFD data, and 0.547% compared with the experiment (Korea Institute of Machinery and Materials (KIMM)). The turbine blade region was affected by the erosion rate at the trailing edge because of their high velocity. Furthermore, in the cavitation–erosion simulation, it was observed that abrasion propagation began from the pressure side of the leading edge and continued along to the trailing edge of the runner. Additionally, as sediment flow rates grew within the area of the attached cavitation, they increased from the trailing edge at the suction side, and efficiency was reduced. Cavitation–sand erosion results then revealed a higher erosion rate than of those of the sand erosion condition.

The Kaplan turbine is an axial propeller-type turbine that can simultaneously control guide vanes and runner blades, thus allowing its application in a wide range of operations. Here, turbine tip clearance plays a crucial role in turbine design and operation as high tip clearance flow can lead to a change in the flow pattern, resulting in a loss of efficiency and finally the breakdown of hydro turbines. This research investigates tip clearance flow characteristics and undertakes a transient fast Fourier transform (FFT) analysis of a Kaplan turbine. In this study, the computational fluid dynamics method was used to investigate the Kaplan turbine performance with tip clearance gaps at different operating conditions. Numerical performance was verified with experimental results. In particular, a parametric study was carried out including the different geometrical parameters such as tip clearance between stationary and rotating chambers. In addition, an FFT analysis was performed by monitoring dynamic pressure fluctuation on the rotor. Here, increases in tip clearance were shown to occur with decreases in efficiency owing to unsteady flow. With this study’s focus on analyzing the flow of the tip clearance and its effect on turbine performance as well as hydraulic efficiency, it aims to improve the understanding on the flow field in a Kaplan turbine.

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Cavitation is an abnormal physical phenomenon which occurs in relatively low–pressure regions in turbomachinery such as pumps and hydraulic turbines. A comparison between the pump and turbine cavitation behavior is a significant and essential process. The work investigates feasibility of turbineusing existing pump and a comparative study of the cavitation characteristics on a centrifugal pump asturbine numerically and experimentally. The current work adopted the Rayleigh–Plesset cavitation model as the source term for inter–phase mass transfer to predict cavitation characteristics.The experimental data were compared with the numerical results and were found to be in good agreement.Results of the comparative study showed that cavitation first occurred at the suction leading edge on the impeller blades and attached cavitation observed on the impeller blade at the lower suction head in pump mode; however, for the turbine mode, the development of vortex cavitation happened at the runner outlet near thetrailing edge on the impeller blades. Also, in the pump, the cavitation became largerfromshroud to the hub and the cavitation rapidly extended from the suction side to the pressure side. On the other hand in the turbine mode, as the cavitation number decreased more vapor bubbles are drawnup at the runner outlet near trailing edge on the blade suction side.