Structural Analysis of an Archimedes Screw and a Kinetic Hydro Turbine

Finite Element Analysis (FEA) can be a great tool for analyzing the structural integrity of any mechanical design. Paired with Computational Fluid Dynamics (CFD) the forces can be evaluated on a hydro turbine allowing for such an analysis. In this case, two micro hydro turbines were analyzed, an Archimedes Screw design, in the case of an available head, and a hydrokinetic design, aiming at extracting the kinetic energy of a river. The Archimedes Screw design features two non-uniform pitch blades with three rotations, a 19.5" runner length, and a 6" blade diameter, while the shape of the hydrokinetic design follows a more conventional design similar to a propeller using two blades with a NACA 8406 profile swept over 140 degrees with an average span angle of 70 degrees. Rotating frame of reference was a concept used in both simulation types to ease the computational modeling. For the Archimedes Screw design this test was conducted at a volumetric flow rate of 0.1 m3/s and 1000 RPM, while for the hydrokinetic design this test was conducted at a flow rate of 4.0 m/s and 225 RPM. Pressure distributions were imported from CFD simulations, fixed supports were used at the edge of the shaft, and tetrahedral elements were used. In the case of both designs, changes were made in order to improve the structural integrity based on the findings of the FEA study. Factors of safety of each design ultimately were at the least 1.5, given that the studies were completed under the highest loading rather than the optimal loading. Further the deflection found at the tip of the blade in hydrokinetic design reached 8 mm, which is enough to be concerned about the accuracy of the power and efficiency as well as the dynamic stability.