The Influence of Yaw and Coning on Small Bio-Inspired Wind Turbines

Abstract

This thesis is inspired by the coning mechanism of samaras. The study consists of wind tunnel measurements of low aspect ratio horizontal-axis wind turbine models. The tested coning angles (β) ranged from 5◦ to 25◦, and power and tip-speed ratio were measured at Reynolds numbers Re_D = [0.46 ×10^5, 1.8 ×10^5]. Results show that coning improves the power performance of a low aspect ratio small wind turbine. Compared to the reference rotor, i.e., rotor with zero-coning, coned rotors achieve higher power coefficients, especially at high Reynolds numbers Re_D ≥ 1.2 × 10^5. Additionally, the optimal power coefficient of coned rotors is less sensitive to Reynolds number variation. The study also investigates the effect of yaw on the small wind turbine models for yaw angles (γ) of 10◦ and 20◦. Power coefficient measurements revealed that coning had a more pronounced effect on the turbine model in yawed inflows than in zero-yaw. Rotor with β = 15◦ had a 14% higher power coefficient than the planar rotor at Re_D = 1.8 × 10^5 and γ = 20◦. Furthermore, coned rotors exhibited lower power loss due to yaw, with β = 15◦ rotor being the most robust turbine model in yaw, showing an output power loss of 4% compared to 10% of the planar rotor at γ = 20◦. Overall, the study suggests that the optimal coning angle for this small wind turbine design is 15◦. The findings provide valuable insights into the design and performance optimization of small wind turbines.