NUMERICAL SIMULATION OF FLOW IN THE INLET PASSAGE OF A RADIAL-DIAGONAL HYDROTURBINE

This paper presents the results of a numerical investigation into the hydrodynamic characteristics of the inlet passage of a novel high-head radialdiagonalhydroturbine design. A comprehensive analysis of the primary challenges associated with the flow paths of hydraulic units designed for highhead applications is conducted. It is established that conventional Francis turbines exhibit significant operational limitations in this range, including a narrow efficiency band and a high susceptibility to cavitation phenomena when operating off-design. The primary focus of this research is to verify the hydrodynamic performance of the inlet components of the innovative turbine, whose design incorporates a double-row runner blade system and an intermediate guide vane apparatus. This configuration is intended to enhance overall energy efficiency and provide greater operational flexibility. To facilitate this study, a detailed three-dimensional geometric model of the inlet passage was developed within the SolidWorks CAD environment. Based on this geometric model, a numerical analysis of the three-dimensional fluid flow was performed using computational fluid dynamics methods within the Ansys CFX software suite. The Reynolds-Averaged Navier-Stokes equations were employed, with the k-ε turbulence model utilized to ensure closure and accurately simulate turbulent flow behavior. The resulting velocity and pressure distribution fields were thoroughly analyzed, andstreamlines were visualized to provide a qualitative assessment of the flow structure. The simulation results demonstrate that the proposed designensures the formation of a highly stable and uniform flow field at the runner inlet, which is a critical precondition for preventing uneven blade loadingand achieving optimal performance. The total calculated hydraulic losses within the inlet passage were found to be 4.7 %. These findings confirm thehigh quality of the inlet components' design and provide an essential foundation for a subsequent comprehensive analysis of the entire flow path.Future work will aim to determine the complete energy characteristics and evaluate the cavitation performance of the turbine. This research representsa crucial step in the validation of the new design, contributing to the development of more reliable and adaptive hydropower systems.