Optimization of guide vanes for variable speed Francis turbines – Human controlled vs. automated approach

Abstract

Guide vanes of hydraulic turbines can maximise turbine efficiency and directly influence on turbine operating characteristics. A hydraulic analysis is carried out on geometrically parameterised guide vane foils, to maximise efficiency and potentially observe which configuration gives operating range expansion. Variable-speed operated turbines in hydropower plants tend to run with improved performance at off-design operating points due to the speed variations. A combination of variable speed turbine operation and guide vane shape optimization gives a win-win situation in water to energy usage ratio. Human controlled developed designs and CFD calculations were previously done. The obtained results are compared with automated approach in ANSYS Workbench using Design of Experiments. The numerical tests were made on parametrically developed guide vane cascades, where the turbine efficiency is the evaluated parameter and it is observed in the range of several rotational speeds and calculated flow rates. The cascade design which produces less turbine efficiency deviations for the tested rotational speed range is later exported and hydraulically and geometrically compared with the developed design from the manual approach. The tested configurations of the guide vanes are developed on the basis of Francis 99 turbine model from the Waterpower Laboratory at the Norwegian University of Science and Technology in the existing geometric space for the guide vanes and blades axis positioning circumference.