OUTPUT CHARACTERISTICS INVESTIGATION OF AIRFOIL-BASED FLUTTER PIEZOELECTRIC ENERGY HARVESTER

Piezoelectric energy harvesters can persistently drive the low-power micro-electromechanical systems in the natural environment. For simulating two degrees of freedom plunge-pitch motions of the airfoil and harvesting effectively the aeroelastic vibration energy, this paper proposes a novel airfoil-based flutter piezoelectric energy harvester. Based on the unsteady aerodynamic model, the mathematical model of the fluid-structure-electric coupling fields of the airfoil-based flutter piezoelectric energy harvester is derived. The finite element model is established to simulate the two degrees of freedom plunge-pitch motions of the airfoil and obtain the vortex shedding and flow field characteristics around the airfoil. A wind tunnel experimental system is designed and the prototype of the piezoelectric energy harvester is fabricated. The correctness of the mathematical and simulation models is verified by using the experimental method, and the determined effects of structural parameters of the piezoelectric energy harvester on its aeroelastic vibration response and harvesting performance are analyzed numerically. The obtained results show that the output voltage obtained from theoretical analyses, simulation analyses and experimental investigation demonstrate the good consistency, which verifies the correctness of the mathematical and simulation models. The simulation analyses demonstrate that the changed pressure fields around the airfoil can be obtained, which indicate that the alternated pressure difference drives the airfoil to take place two degrees of freedom plunge-pitch motions. When the airflow velocity exceeds the flutter onset of one, the piezoelectric energy harvester takes place the flutter and occurs the limit cycle oscillations. When the eccentricity is 0.3 and the airflow velocity is 16 m/s, the maximum output voltage is up to 17.88 V and the corresponding output power is 1.278 mW. The power density is up to 7.99 mW/cm³, which achieves the superior harvesting performance over other. The research results provide an important guidance for further designing more efficient airfoil-based flutter piezoelectric energy harvesters.