Airfoil design and testing of multi-stage horizontal axis wind turbine rotors
In this study, small horizontal-axis wind turbine blades operating at low wind speeds were optimized. An optimized design method based on blade element momentum (BEM) theory was used. The radius of the blade 0.2 m, 0.4 m and 0.6 m and blade geometry with single and multistage rotor was examined. MATLAB and XFoil programs were used to implement to BEM theory and devise a six novel airfoil (NAF-Series) suitable for application of small horizontal axis wind turbines at low Reynolds number. The experimental blades were developed using the 3D printing additive manufacturing technique. The new airfoils NAF3929, NAF4420, NAF4423, NAF4923, NAF4924, and NAF5024 were investigated using XFoil software at Reynolds numbers of 100,000. The investigation range included tip speed ratios from 3 to 10 and angle of attacks from 2° to 20°. These parameters were varied in MATLAB and XFoil software for optimization and investigation of the power coefficient, lift coefficient, drag coefficient and lift–drag ratio. The cut-in wind velocity of the single and multistage rotors was approximately 2.5 m/s. The optimized tip speed ratio and angle of attack were 5.5, 6° respectively. The proposed NAF-Series airfoil blades exhibited higher aerodynamic performances and maximum output power than those with the base SG6043 and NACA4415 airfoils at low Reynolds number.