High-Fidelity Modeling and Investigation on Blade Shape and Twist Angle Effects on the Efficiency of Small-Scale Wind Turbines

Abstract

A high-fidelity analysis is carried out in order to evaluate the effects of blade shape, airfoil cross-section. as well as twist angle distribution on the yielded torque and generated power of a horizontal axis Small-Scale Wind Turbine (SSWT). A computational modeling and an effective design for a small turbine with a blade length of 25 cm subject to a 4 m/s freestream velocity are presented, in which a segregated RANS solver is utilized. Four airfoil profiles are assessed, namely NACA0012, NACA0015, NACA4412, and NACA4415, and two blade shape configurations, rectangular and tapered, are evaluated. The flow around the rotating turbines is investigated along with blade stresses and performance output for each configuration. Subsequently, the impact of various linear and nonlinear twist distributions on SSWT efficiency is also examined. Results show that for the studied operating conditions corresponding to low-speed flows, the rectangular blade configuration outperforms the tapered blade shape from the generated torque and power perspectives, while the tapered shape configuration represents an attractive design choice from the yielded stresses point of view. Additionally, while the nonlinear twist configuration results in the best performance among the configurations studied, an SSWT blade design implementing a linear twist distribution can be highly competitive provided that a good slope is carefully selected.

Keywords

• small-scale horizontal axis wind turbines
• high-fidelity simulations
• flow visualization
• blade geometry
• twist angle
• energy efficiency