Enhanced airfoil-based flutter piezoelectric energy harvester via coupling magnetic force

This paper proposes a novel magnetic coupled airfoil-based flutter piezoelectric energy harvester, for decreasing the critical velocity, broadening the working bandwidth, and achieving more efficient harvesting performance at lower airflow velocity. The conceptual designing of the harvester system via coupling magnetic force is first conducted, the mathematical and simulation models of the fluid–structure-electric–magnetic coupled fields are then established, and the experimental prototypes are finally fabricated. The influences of the structural parameters of the harvester system on the vibration response and output performance are fully studied. The results show that the magnetic repulsion force decreases the equivalent stiffness of the harvester system and makes it easy to couple plunge-pitch motions. A decrease in the magnet spacing distances leads to decreasing the critical velocity and improving the output performance. Compared with the magnetic spacing distance of 25 mm, the critical velocity with the magnetic spacing distance of 17 mm decreases by 70%, and the enhancement ratio of output power increases by 50% at 13.8 m/s. The flow field demonstrates that the alternating pressure difference drives the harvester system to take place two DOF plunge-pitch motions. The experimental results are in good agreement with the theoretical values, which verified the established mathematical model. The designed magnetic coupled airfoil-based flutter harvester system achieves a larger vibration response and better harvesting performance at lower airflow velocity. This work provides essential foundations for achieving better harvesting performance via coupling magnetic force.