Enhancement of vibration based energy harvesting using compound acoustic black holes

Acoustic black hole (ABH) effects can be obtained via proper structural tailoring to induce a gradual reduction of the flexural wave velocity, thus creating high energy density structural areas. The wave energy focalization effect shows promising features for establishing novel vibration energy harvester configurations in terms of the high energy level and broadband characteristics. In this study, an energy harvesting structure with ABH features which ensures the structural strength as well as enhances the harvesting performance is proposed and investigated. Considering the wavelength compression in ABHs, piezoelectric patches bonded on the surfaces of ABHs are sliced into micro arrays to convert the mechanical energy effectively, which make sure that the positive and negative electric charge generated on the surfaces of harvesters won't be neutralized. Each of the transducers is shunted with a resistor impedance. Fully coupled numerical models which consist of vibrational structures and electrical circuits are built to assess the energy harvesting performance of ABH-feature beam and uniform beam under both steady state and transient excitations. Experiments are also conducted to verify the significant performance enhancement in the ABH beam as compared that in the uniform beam. It is shown that the ABH structural tailoring can be used for broadband vibration energy harvesting and boost the harvested power by more than one order of magnitude. (C) 2019 Elsevier Ltd. All rights reserved.