Assessment of fairing geometry effects on H-Darrieus hydro turbine performance using 2D URANS CFD simulations

Abstract

This study aims to enhance the hydrodynamic efficiency of the fairing system and increase the power coefficient Cp of a three-bladed H-Darrieus turbine by investigating various geometries and configurations in comparison to the reference model. 2D CFD modeling and URANS calculations along with the k-ω SST turbulence model are employed for conducting parametric studies. The analysis focuses on assessing the geometric parameters of the fairing system that affect its behavior, such as the angle of incidence α and the chord length C of the fairing profile. It was found that at x/C=0.39934, the normalized power coefficient Cp/Cp,max of H-Darrieus equipped with the fairing amounts to 0.967581, whereas at x/C=0.750825, it attains Cp=0.486284. A power coefficient of Cp=0.621315 is achieved when an angle of attack α=10∘ and a tip speed ratio λ=2 are combined. In addition, the optimal operating point Cp for both fairing profiles is λ=2. In addition, maximum performance is reached at α=18∘ for the Eppler-420 profile, with a peak Cp=0.662, whereas the S1223-RTL profile demonstrates optimal performance at α=30∘ , with a peak Cp=0.728. Differences in the maximum and minimum ΔP∗ values between the Eppler-420 and S1223-RTL are also noted. It is observed that the S1223-RTL profile displays lower drag Cd and lift Cl coefficient values than the Eppler-420 profile up to α≈22∘. finally yet importantly, the highest Cp is observed at a chord length of C=4.0R, while the lowest occurs at a chord length of C=2.5R. Both Cd and Cl exhibit relative constancy for chord lengths shorter than C=4.0R.