EXPLORING STRUCTURAL DESIGN OF THE FRANCIS HYDRO-TURBINE BLADES USING COMPOSITE MATERIALS

Composite materials are increasingly exploited in industry especially replacing metallic structures due to their strength/weight ratio. Amongst the notable applications, for which composite materials have not challenged metals yet are hydro-turbines, which are overwhelmingly made of steel or copper alloys. Replacing blade material by laminate composites can reduce weight and inertia, as well as achieve smaller cross-sectional thicknesses, better fatigue strength, damping, and resistance to cavitation. Manufacturing techniques are mature enough to respond to the challenge, provided that the laminate composite blades are properly designed. In the current work, the design of the Francis carbon blades was studied by employing finite element analysis. The blades were designed sub-optimally with various stratification patterns and different failure and maximum displacement limitations following a systematic methodology for gradual addition of laminate layers or patches. The methodology is still of a trial and error nature driven by the designer but guesses in the individual steps are much more informed due to model analysis and optimization tools available.