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 (CP). 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 CP and the turbine design parameters, such as the skew (ϕ) and rake (γ) 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 (CP). A 3D computational domain in ANSYS Fluent software and the k-ω SST turbulence model were utilized, for the unsteady flow simulations. Under optimal design conditions, i.e., when ϕ and γ were equal to 13.30° and -18.06°, respectively, the highest CP 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 CP values obtained as a function of the tip speed ratio.