Performance Analysis and Parametric Design of an Airfoil-Based Piezoaeroelastic Energy Harvester

Abstract

Energy harvesters are designed to convert energy from ambient sources to recharge batteries or power low-power-consumption microsystems. The piezoelectric transduction of aeroelastic vibrations is a scalable option for energy harvesting. To design an efficient harvester, the harvesting performance needs to be studied and hence enhanced. The purpose of this paper is to analyze the dynamic response and harvesting performance of an airfoilbased piezoaeroelastic energy harvester by investigating the effects of the system parameters and external discrete disturbances. The airfoil, with plunge and pitch degrees of freedom (DOFs), is supported by linear flexural springs and nonlinear torsional springs. Piezoelectric transducers are attached to the plunge DOF. The unsteady aerodynamics due to arbitrary motions are obtained from Jones’ approximation of the Wagner function. A state-space model is obtained for numerical simulation. Parameters including the load resistance, the nonlinear torsional stiffness coefficient, the free play gap and the locations of both elastic axis and gravity center axis of the airfoil are concerned. In addition, the effects of 1-cosine gust disturbances are studied. The results show that: as the resistance increases, each of the plunge and pitch motions has a minimum amplitude. But the minimum response amplitudes do not affect the variations of the electric outputs. There is one optimal resistance maximizing the power output. Besides, the increase of the free play gap enhances harvesting performance linearly, whereas large nonlinear torsional stiffness would significantly decrease the power output. The variations of the voltage output with the structural nonlinearities resemble that of the plunge motion. Moreover, there is one optimal eccentricity of the airfoil for the highest harvesting performance as the elastic axis is fixed and the flow velocity is certain. The rearward shift of the elastic axis helps enhance the power output whereas it demands larger eccentricities to maintain limit cycle oscillations (LCOs). Last but not the least, under a relative large wind scale, the discrete gust loads may change the equilibrium position of both plunge and pitch responses under special gust vertical velocities. The jumps may affect the phase of the electric outputs, but they make no difference on the amplitude of power output.