Purpose: This study analyzes the blade channel vortices inside Francis runner with a particular focus on the identification of different types of vortices and their causes. Design/methodology/approach: A single-flow passage of the Francis runner with refined mesh and periodic boundary conditions was used for the numerical simulation to reduce the computational resource. The steady-state Reynolds-averaged Navier–Stokes equations closed with the k-ω shear–stress transport (SST) turbulence model were solved by ANSYS CFX to determine the flow field. The vortices were identified by the second largest eigenvalue of velocity. Findings: Four types of vortices were identified inside the runner. Three types were related to the inlet flow. The last one (Type 4) was caused by the reversed flow near the runner crown and had the lowest pressure inside the core near the runner outlet. Thus, in the blade channel vortex inception line, Type 4 vortex would appear earlier than the other three ones. Besides, the Type 4 vortex emerged from the crown and shed toward the blade-trailing edge. And its location moved from near the crown down to near the band when the unit speed increased or unit discharge decreased. Research limitations/implications: Although the refined mesh was used and the main vortices in the Francis runner were well predicted, the current mesh is not enough to accurately predict the lowest pressure in the channel vortex core. Practical/implications: This knowledge is instructive in the runner blade design and troubleshooting related to the channel vortex. Originality/value: This study gives an overview of the main observed blade channel vortices and their causes, and points out the important role the reversed flow plays in the formation of blade channel vortices. This knowledge is instructive in the runner blade design and troubleshooting related to blade channel vortices.

A large number of pumped storage power plants will be put into operation in China. The current development of modern pump storage power plants aims towards a higher flexibility and stability in operation, and an extended operation range of the hydraulic machine. These projects have a large number of problems. For problems of the turbine units, the optimization of pump turbine is very crucial to ensure the unit's high efficiency and stability. The velocity distribution on the runner outlet is very important to optimize the pump turbine. In this paper, the velocity on runner outlet was tested by LDV (Laser Doppler Velocimetry). The axial velocity and circumferential velocity on runner outlet were tested at different working points by LDV. The velocity distribution can provide important reference for the runner design.

In order to understand the complex nature of the system dynamic phenomena, such as the strong vibration and noise caused by blade passage in the pump turbine, a state-of-the-art three-dimensional (3D) compressible transient simulation would be desirable to study the problem in depth. This study investigated the phase resonance (PR) that occurred during a full-load operation in the turbine mode of a pump turbine on a prototype scale. As a first step, the wave reflection at the boundaries, and the influence of the timestep and sound speeds on the behavior of traveling pressure waves inside a spiral casing, were studied. It was found that nonreflective boundary conditions and an appropriately small timestep are critical to capturing the wave reflection and superposition process inside a spiral casing; a certain kind of direct PR risk was detected in its system design. The detected direct PR differed from the well-known PR with two features: firstly, it was almost independent of the sound speeds, and secondly, the pressure distribution over the spiral circumference varied among the amplitudes. The latter feature was caused by pressure waves at every stator channel induced by a rotor stator interaction (RSI). The 3D flow simulation with an acoustic model, which couples the RSI and PR phenomena, would predict better results for understanding the problem than the simplified one-dimensional (1D) method.