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Original research DIGITAL RECONSTRUCTION AND CFD-BASED PERFORMANCE MAPPING OF A FRANCIS TURBINE RUNNER USING 3D SCANNING UNDER VARIABLE HEAD AND GUIDE VANE OPENINGSPages 257-268
Abstract
The performance of Francis turbines in hydropower plants largely depends on the integrity of the runner geometry, which may be affected by wear and tear, cavitation effects, and structural deformation; hence, it requires evaluation with reference to its actual geometry. This research paper aims to address how to accurately reconstruct the runner of a Francis turbine and how to evaluate its hydraulic performance for various heads and vane opening values. The method involves 3D scanning of the runner surface using the structured light method and processing the data to reconstruct the runner geometry using SpaceClaim. The runner geometry is then analyzed for its hydraulic performance using steady-state CFD with the k-ε turbulence model in ANSYS CFX. The runner was simulated for various heads of 44m, 83m, and 122m and for various values of vane opening angles ranging from 1.3 to 19.3 degrees to find discharge, shaft power, and efficiency. The results show that for the given operating head of 83m, the maximum shaft power of 1.275 MW is developed for 19.3 degrees vane opening angle, and the highest efficiency of 91% occurs for 14.3 degrees (BEP). The occurrence of vortices and swirling motions is evident for the runner operating under partial load conditions. Thus, it may be concluded that 3D scanning and CFD are useful tools for runner performance evaluation.
Keywords: Francis turbine, 3D scanning, reverse engineering, CFD, hydraulic performance, guide vane opening, variable head.
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Irwanda Yuni Pungkiarto, 
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