Abstract
Francis type hydraulic turbines that have a wide range of operating range for head and flow rates are commonly used in hydropower generation. Every power plant needs its custom designed turbine because the available head and flow rates, which are the main parameters to start the design process, are different for each plant. Guide vanes are the only movable parts of Francis turbines. They control the flow rate through the turbine. In this study, a generalized Computational Fluid Dynamics (CFD) aided design methodology is developed and applied to the design of the turbines of two different power plants. The effects of several parameters, including the shape of the guide vane profile, eccentricity, blade angles, overlapping percentage of the blades, number of guide vanes, and rotor-stator distance are examined. Results are investigated for each parameter in terms of flow physics and important outcomes are determined for turbine designers.
Highlights
Francis turbines are applicable to a wide range of head and flow rates; they are commonly used in hydropower generation
Shape of Hydrofoil: Different NACA profiles for the guide vane hydrofoils are simulated to observe the effect of the shape on outlet flow angles, head loss, meridional velocity profile and torque exerted by the flow to the guide vanes
Different NACA profiles for the guide vane hydrofoils are simulated to see the effect of the shape on outlet flow angles, head loss, meridional velocity profile and torque exerted by the flow to the guide vanes
Summary
Francis turbines are applicable to a wide range of head and flow rates; they are commonly used in hydropower generation. Guide vanes control and direct the flow to the runner By rotating around their axis, they change the net inflow area, which directly alters the mass flow rate passing through the turbine. They form the necessary swirl at the entrance of the runner [1]. Any change in guide vane opening results in changes in mass flow rate and runner inlet flow angle [2]. They are the only components which can control the mass flow rate and the generated power [3]. They play an important role in operating the turbine at the best efficiency point where the hydraulic losses reach their minimum values [5]
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