Sensors that provide critical information about aero-engine performance are widely installed on static components but are rarely found on rotors because of their inaccessibility and extremely high rotation speeds. This dissertation presents a new monitoring method, integrating energy harvesting technology with wireless sensors to achieve online self-powered engine monitoring. Energy harvesters, used to generate power from ambient vibration, are sustainable alternatives to batteries for achieving self-sustained long-term operation of electronic devices. Thus, the proposed approach not only breaks limitations from bulky wired connections that are vulnerable to failures but also solves battery issues.

To achieve the proposed method, this study takes the lead to assess the energy harvesting potential in high-RPM turbine engines. Considering the harsh condition of extremely high rotation speed in the aero-engine, this study proposes a method to harvest the energy from the rotational parts of the aero-engine, in the meantime, largely avoiding the bad effect from the centrifugal force. In addition, by utilizing structural nonlinearity, force amplification mechanism, and the piezoelectric effect, a high-efficiency compressive-mode piezoelectric energy harvester (HC-PEH) that is characterized by high power output and wide working bandwidth is developed and then studied experimentally and theoretically. The theoretical solutions closely render experimental results and estimate a 172% growth in frequency bandwidth when exploiting the centrifugal force for bandwidth up-conversion. The experimental result shows that the HC-PEH has a better performance in the rotational excitation case, dominantly owing to the centrifugal force. Comparing with the traditional cantilever bending-mode energy harvesters, the proposed HC-PEH shows completely better performance in power generation, working bandwidth, and structural strength when tested in the rotational excitation. In demonstrations, the HC-PEH prototypes show a maximum output power of 78.87 mW, 1 mW- and 10 mW-bandwidths of 22.5 Hz and 11.17 Hz, and the capabilities of lighting up 112 LEDs and powering a wireless sensor.

Since the performance of the HC-PEH deteriorates when used in rotational environments with an offset distance, to overcome this problem, this dissertation introduces a method of using a magnetic force. The performance of the magnetically coupled and the normal rotational HC-PEH systems with offset distances are experimentally studied. The results show the proposed method is feasible and significantly improves the performance (peak-peak voltage) by 258.2%. To attain comprehensive insight into the electromechanical behaviors of the system, a theoretical model is developed. The simulation results closely render the experimental data and are used to characterize the system. Then, a parametric study is performed and the results indicate that the best performance improvement can be obtained via tuning the parameters related to the magnetic force, the centrifugal force, and the initial deformation of the elastic beams.

This dissertation also presents a modeling and dynamic analysis of a rotational HC-PEH with partially thickened bow-shaped beams. The developed distributed-parameter model is validated against experimental data and a good agreement is achieved. The stability and the nonlinear dynamic behavior of the rotational HC-PEH system in conditions of different offset distances and preloaded axial forces are investigated by numerical simulation results. A parametric study is also performed to study the effect of the design parameters on the voltage response of the system and the result shows that the design parameters of the bow-shaped beam and the PZT plate have noticeable effects on the electrical output of the harvester system.

In the last chapter, effects of the bending-torsional coupling vibration due to the misalignment of the centroid and the torsional axis, on the performance of the HC-PEH are studied experimentally and theoretically, respectively under translational displacement and rotational force excitations. Distributed-parameter models of the system respectively under translational and rotational excitations are developed. To validate the models, the finite element (FE) analysis and the experiment are performed. The simulation results by the method of this study closely render the modal result obtained by the FE method and the experimental result of the voltage response, respectively. Effects of the key parameters on the hardening resonance, steady-state response, and the jump-down phenomenon activated by the torsional vibration are revealed. The results show that the torsion-induced chaotic motion can activate the jump-down phenomenon, largely reducing the system’s performance, but it can be mitigated or even avoided by tuning the key parameters. Additionally, the occurrence of the torsion-induced jump-down phenomenon is sensitive to the system’s initial state when the structure is subjected to translational excitations.

This work not only paves a new way for developing future monitoring systems for advanced aero-engines and other rotating machinery applications, but also develops an in-depth theory of rotational compressive-mode piezoelectric energy harvesters.