Designing manufacturable high performance rotor blades for micro wind turbines through cambered plate airfoil optimization

Abstract

Conventional methods for manufacturing rotor blades, such as composite construction and die casting, are hindered by high costs due to expensive molds, while 3D printing often results in poor quality or high production costs with unfavorable cost-per-part scaling. Moreover, conventional airfoil designs perform poorly at Reynolds numbers below 100,000, necessitating larger rotors. This becomes especially problematic in wind tunnel studies, where multiple rotors must fit within a single wind tunnel for wake or multirotor research, significantly increasing both building costs and wind tunnel requirements. To address these challenges, this study develops high-performance rotor blades for micro wind turbines that are aerodynamically efficient under low Reynolds number conditions and easy to manufacture. Using cambered plate airfoils, the optimization process employed a class shape transformation and seventh-degree Bernstein polynomials. Aerodynamic performance was analyzed using XFOIL, with evaluations conducted at Reynolds numbers of 30,000, 40,000, and 50,000 to ensure robust performance across realistic operating scenarios. The iterative optimization employed both single-objective and (genetic) multi-objective algorithms, targeting both aerodynamic efficiency and manufacturability. The blade tested with the optimized MB-LR2-7.5 airfoil exhibited superior performance in wind tunnel tests, closely matching Blade Element Momentum (BEM) simulations. This research highlights the potential of cambered plate airfoils to improve micro wind turbine performance while maintaining ease of manufacturing, with potential applications in UAVs, drone propellers, and HVAC systems. The findings advance the understanding of aerodynamic optimization in low Reynolds number environments, paving the way for more efficient and cost-effective rotor designs.