Aerodynamic analysis of bioinspired blades based on Cerrado seeds for small-scale wind turbines

Abstract

The increasing demand for sustainable energy sources has propelled intensive research in renewable technologies, with wind energy emerging as a critical player in the green energy landscape. In this context, optimizing wind turbine blades plays a crucial role in the overall efficiency of wind energy generation systems. Pursuing more efficient and innovative designs has led to applying bioinspired approaches, incorporating natural principles to enhance aerodynamic performance. This dissertation encompasses a novel investigation into the aerodynamic properties of Cerrado samara, focusing on autorotation behavior, flow patterns, and free-fall velocities. Experimental analysis in a wind tunnel was complemented by Reynolds-Averaged Navier-Stokes (RANS) simulations for the full-scale samara, a conventional reference blade based on SG6043 airfoils without angle of attack, and a bioinspired blade with reduced solidity. QBlade simulations were performed for the reference blade. The ANSYS Fluent® software, using the Moving Frame Reference (MRF) model, was employed to model airflow around the turbine. Simulations covered a wind speed range of 4 to 12 m/s, with increments of 2 m/s, and a rotation speed ranging from 300 to 700 RPM, with increments of 100 RPM. There was an agreement between simulations and experimental data, establishing the effective operational range of this rotor between 4.5 and 6 m/s. Consistent with previous studies, results reveal efficient autorotation patterns, significantly contributing to understanding underlying aerodynamic principles. Under these conditions, the proposed bioinspired turbine achieves a TSR of 5, with Ω ranging from 300 to 500 RPM, yielding CP,max of approximately 0.54. In comparison, the reference blade demonstrated a CP max of roughly 0.55 at TSR 6, around 460 RPM, using QBlade®, and a CP,max of approximately 0.55 at TSR 8, around 600 RPM, using Ansys Fluent®. A comparative analysis was also conducted between the bioinspired blade developed in this study and existing bioinspired blades. These detailed analyses provide a solid foundation for future innovations in wind turbines, offering crucial insights into the relative performance of blades, their initiation characteristics, and associated torques. All experiments were conducted at the LAEX (Laboratório de Aerodinâmica Experimental) of the Centro de Pesquisas Aerodinâmicas Experimentais (CPAERO) at the Universidade Federal de Uberlândia (UFU).