Application of a central composite face-centered design in the optimization of an archimedean hydrokinetic turbine

Abstract

Currently, in the literature, there are no general guidelines for the optimal hydraulic design of Archimedean screw turbines (AST) used in hydrokinetic applications. Therefore, this study is aiming at selecting the most significant geometric factors, such as the diameter ratio between the inner (Di ) and the outer (Do) diameters (i.e.,Di/Do), the axle length (L) and the blade stride (p), influencing the AST performance by using a central composite face-centered (CCF) experimental design combined with the response surface methodology (RSM). The statistical analysis of variance (ANOVA) test identified with a significance level of 0.05 that the most significant variables on the performance of the turbine were p and Di/Do. The AST efficiency was evaluated by means of the power coefficient (Cp), which was calculated by means of computational fluid dynamics (CFD) methods coupled with the 6-degrees of freedom (6-DoF) approach. The second-order polynomial model was used to predict the Cp and the coefficient of determination (R2) was found to be 97.4%.