Design, Performance and Maintenance of Francis Turbines
The aim for turbine design is to increase the efficiency and avoid cavitation and fractures during operation.. A brief discussion on a the design philosophy during the last 60 years with will be presented. The structural design has moved from castings and riveted plates to fully fabricated structures of high tensile strength steel in the stationary parts and stainless 13/4 Cr/Ni or 16/5 (17/4) Cr/Ni steel have substituted the 13/1 Cr/Ni in runners. The paper also includes an ancient runner design with plate steel blades moulded in cast steel at crown and band. Such high head runners, put in operation in 1950, hve been in operation in good condition Norway until about 15 years ago. A discussion on stress analyses and fatigue problems of pressure loaded parts and high frequency fatigue in runners, will be presented.
