Reverse engineering design and rehabilitation of a francis turbine runner

Francis type hydraulic turbine runners are equipped with complex shaped blades and their blades are iteratively designed with special design programs. Runner blades have rotational and variant three dimensional profiles, in order to direct incoming flow and provide performance values, so it is impossible to obtain technical drawing data. A reverse engineering design methodology is necessary for the redesign of an existing runner geometry especially in the hydroelectric power plant rehabilitation studies. In addition to traditional reverse engineering process, blade design parameters should be determined to obtain an analyzable blade geometry from the solid model. In this study, a reverse engineering design methodology is developed for Francis type hydraulic turbine runners. Traditional reverse engineering steps are applied to two different runners that have different specific speeds. The developed design methodology is verified by applying to BUSKI HEPP runner which is designed by our group (ETÜ Hidro). The verified methodology is utilized for Kahta HEPP which provides 70% of the installed capacity in order to find out the reasons of the lack of performance and rehabilitation studies are carried out. As a result of rehabilitation studies, a new runner geometry is obtained with power of 3539,6 kW and efficiency of 96,5%.