Study on the energy capture efficiency of flapping airfoil power generator using semiactive dual‐layer airfoils

AbstractTo address the problem that the energy capture efficiencies of existing flapping airfoil power generators are lower than those of traditional turbine generators, a dual‐layer flapping airfoil structure was adopted to improve the energy capture performance of the semiactive flapping airfoil, inspired by the multiwing flying mode of dragonflies in nature. The influence of the dual‐layer flapping airfoil structure on the energy capture performance of a semiactive flapping airfoil was systematically analyzed by a Taguchi experimental design and computational fluid dynamics simulations. The results showed that the dual‐layer flapping airfoil structure mainly improved the energy capture efficiency of the flapping airfoil by increasing the lift force and reducing the maximum sweep distance. Under the optimized parameter combination, the energy capture efficiency of the dual‐layer flapping airfoil reached 28.80%, which was 17.74% higher than that of the single‐layer flapping airfoil. Furthermore, the influence of the dual‐layer flapping airfoil structure on the energy capture performance of a semiactive flapping airfoil was related to the mass ratio of the system, and a larger mass ratio (M* ≥ 40) caused the performance of the dual‐layer flapping airfoil to deteriorate. Analysis of the vortices around the flapping airfoil revealed that there were more attached vortices on the surface of the dual‐layer flapping airfoil, but the increase in the mass ratio led to an advance of the separation of the leading edge vortex, which was the reason that the dual‐layer flapping airfoil with a smaller mass ratio had a better energy capture performance.