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Reconstruction methodology of a Francis runner blade using numerical tools

Abstract:

In a hydraulic turbine, the search of a better energy exchange with the fluid has led to designs of runner blade of geometrical shapes so complex that they are considered as free-form surfaces. Since such blade characteristics are unable to be expressed by analytic functions, its complete and realistic geometrical reconstruction requires an excessive quantity of design parameters. This study proposes a coherent and robust full 3D blade numerical reconstruction methodology in which the geometrical definition of the blade is independent of its design parameters. A quantitative and qualitative fit evaluation shows that the blade surface reconstruction needs an important quantity of discrete data along the spanwise and streamwise direction to achieve a continuous and smooth definition. The results infer that the shape characteristics of damaged and worn blades without an original CAD model could be recovered, making this methodology attractive for industrial and optimization applications.