Taguchi and CFD-based hydrodynamic performance investigations of diffuser-augmented hydrokinetic turbines

Abstract

In recent years, interest in renewable energy technologies has been increasing as part of the effort to obtain clean energy. One of these technologies, Hydrokinetic Turbines (HKT), converts the kinetic energy of water flow into electricity. However, these turbines fail to reach the theoretically calculated power coefficient (CP). To overcome this issue, researchers are developing various diffuser designs to enhance efficiency. In this study, the effects of the parameters used in diffuser design (foil type, diffuser length, tip clearance, and angle of attack) on the CP were investigated using Taguchi analysis, and an optimum diffuser design was developed for the Horizontal Axis Hydrokinetic Turbine (HAHT) based on the obtained experimental results. For the validation study of HAHT and CP calculations of the Diffuser-Augmented Hydrokinetic Turbine (DAHT), the Computational Fluid Dynamics (CFD) method was employed. According to the results of the Taguchi analysis, it was determined that diffuser length is the most influential parameter on the CP. Additionally, it was found that the effect of tip clearance on CP is relatively limited compared to other parameters. For the optimum operating parameters, maximum CP value was calculated as 0.7006. Consequently, a 67 % increase in the CP of the existing HAHT was achieved.