Horizontal-axis propeller hydrokinetic turbine optimization by using the response surface methodology: Performance effect of rake and skew angles

The design of a horizontal-axis propeller hydrokinetic turbine (HPHT) depends on several geometric parameters affecting its hydrodynamic efficiency which is measured through the power coefficient (C-P). In this study, a 1 kW turbine with 1.6 m of rotor diameter (D) was used as the prototype to know the relationship between the C-P and the turbine design parameters, such as the skew (phi) and rake (gamma) angles. A full-factorial design of experiments, as a response surface methodology technique, and computational fluid dynamics simulation were used to determine the significance of the factors considered and their interaction in the maximization of the response variable (C-P). A 3D computational domain in ANSYS Fluent software and the k-omega SST turbulence model were utilized, for the unsteady flow simulations. Under optimal design conditions, i.e., when phi and gamma were equal to 13.30 degrees and -18.06 degrees, respectively, the highest C-P was 0.4571. For these optimal values, a scaled model with 0.24 m of diameter was numerical and experimentally studied and the findings were compared. A good agreement was found between the numerical results regarding the lab-scale turbine and the experimental data for the C-P values obtained as a function of the tip speed ratio.