Study On Sound Energy Harvesting Of Vehicle Based On Local Resonant Phononic Crystal

In recent years, Micro-Electro-Mechanical System(MEMS) and wireless sensor are widely used in many engineering fields, such as environmental monitoring. The chemical batteries, as power for wireless sensors, need to be replaced regularly. However, harvesting environmental energy for self-powered sensors is conductive to reduce the chemical battery usage, which possesses economic values and social environmental benefits. With the sustainable growth of automobile ownership, the increasingly rich vehicle noise energy is becoming more accessible. In this thesis, the Quarter-wave-Resonator-Phononic Crystal(QRPC) is proposed to harvest the vehicle noise energy below 1000 Hz. It is verified through theoretical and experimental analysis.Firstly, Mathematical model of QRPC is established based on the impedance characteristics of quarter-wave-resonator, the band structures of QRPC are calculated and analyzed by Transfer Matrix(TM) method, and the results show that the 1st band gap is caused by the local resonance of unit vibrators. Based on the mathematical models of QRPC, some influence factors on the band structures, such as the distance and length of branch tubes, the area ratio between branch tube and waveguide, are investigated. The obtained results may be provided as a theoretical guidance for the local resonant band designing.Secondly, the acoustic Finite Element Models(FEM) of QRPC are established and used for exploration of sound localization effect. Through calculating and analyzing, sound pressure distributions of QRPC show that the local resonant effect appears at the initial and cut-off frequency of band gap. The FEM simulated results agree reasonably well with the results of TM method. The sound localization effect is characterized by amplification factor of sound pressure(ASP) of each branch tube and total average amplification factor of sound pressure(TASP) of QRPC, respectively. The influences of the structural parameters, such as the distance and length of branch tubes, the number of branch tubes and the area ratio between branch tube and waveguide, on ASP and TASP are further studied. The results have reference values for the design of high-efficiency sound energy localization devices.Finally, the multi-physics coupling FEM of the piezoelectric QRPC is established to predict the output voltage of energy harvesting under the excitation of incident sound pressure. The results indicate that the output voltage enhances sharply at the initial and cut-off frequency of band gap. Moreover, the sound energy harvesting experiment is carried out. The experimental results agree reasonably well with the FEM results, which verify the feasibility of harvesting sound energy using QRPC.This thesis aims at proposing a vehicle sound energy harvesting method. The obtained conclusion may be provided as a theoretical guidance for harvesting low frequency, wide band sound energy, which is practical significant and instructive to environmental energy harvesting field.