Marine energy harvesting from low cut-in speeds horizontal axis ocean current turbine: design, optimization and analysis of the rotor

摘要

Energy extraction from tidal currents using marine current turbines has been gaining attention in recent years. In the first part of this thesis, the design and optimization of a horizontal axis turbine is proposed to harvest available ocean kinetic energy from very low speed flow regimes. A horizontal axis marine current turbine is modeled and NACA 4 series foils are selected as the two-dimensional blade foils design domain. Blade geometry and foil shape are then optimized using Response Surface (RSM) and Steepest Ascent Methodologies (SAM). The performance and accuracy of the proposed design is compared and validated with the developed turbine Blade Element Momentum (BEM) theory model. In the second part of the thesis, hydrodynamic properties of the optimized foil are simulated through a commercial Computational Fluid Dynamic (CFD) package and then compared with the conventional Eppler 61 foil properties. The two-dimensional analysis confirms the effectiveness of the optimization for the Reynolds number of 42000. A three dimensional start-up CFD simulation is then performed to calculate the unsteady load distribution over the blade surfaces which have been further utilized in a static Finite Element Analysis (FEA) to measure the rotor's blade tip deflection. This stage guarantees the safe and optimum structural performance of the rotor in regard to various existing material choices and manufacturing technologies.