基于多稳态相干共振的低速流体动能能量收集理论与实验研究

The low-velocity fluid, such as river stream and air flow, contains a huge amount of kinetic energy, transforming which into electric energy has a realistic significance. Based on this background, this project will carry out theoretical and experimental studies on harvesting energy from low-velocity fluid by multi-stable devices. The multi-stable characteristic will be used to attain coherence resonance, which can bring about a large deflection and give a high output energy. In the transformation of the kinetic energy of water stream, first the fluid-elastic-piezoelectric coupling equations are derived, and the method of solving the equation is studied. Then the equations are solved for different velocities, thereby obtaining the dynamical responses and output voltages. Subsequently the multi-stability is introduced to construct a multi-stable dynamical model. The corresponding coupling equations with multi-stability are derived and solved. Conditions for occurrence of jumping between the stable positions can be obtained. Internal resonance will be exploited to excite jumping between different equilibrium positions and realize coherence resonance. Finally the multi-stable harvester will be optimized to realize a dense jump between the stable positions and generate the highest output power. For validation the corresponding experiments will be designed and carried out. For low-velocity air flow, the multi-stability will be realized by magnetic forces. The device can be excited to make snap-through between the stable positions and attain coherence resonance by wind, thereby obtaining a high output electric power. The corresponding validation experiments will be designed and carried out. This study on harvesting fluid energy can be used to improve the transforming efficiency of low-velocity fluid in natural environments.

自然界的低速流体，如河流、空气流动等，蕴含着巨大的动能，将其转化为电能具有重要的实际意义。本项目以此为背景，开展基于多稳态与相干共振的低速流体动能转换理论方法与实验研究，目的在于通过內共振与相干共振使多稳态结构产生大幅度的动态跳跃响应，提高流体动能转换效率。在水流动能收集方面，建立流体-弹性体-压电动力学耦合方程，研究其稳定性与分叉；对方程求解，得到动力学响应及输出电压；建立多稳态俘能结构，由内共振激发结构响应在各稳态间跳跃，进而实现在随机激励下的相干共振。建立多稳态结构-流体-压电耦合方程，研究流场与相干共振关系，保证俘能结构在流速变化下保持相干共振，实现最大的电能输出。建立相应的实验装置，进行实验验证。在低速空气动能收集方面，建立基于磁力的多稳态压电俘能结构，在风速大范围变化下保持结构实现多稳态跳跃及相干共振，得到较高的风能转换效率及输出电能功率。进行由相干共振收集风能的验证实验。

针对自然界中存在的低速流体，比如水流与气流，设计能量收集结构，利用非线性多稳态及相干共振，实现低速流体动能的高效收集。基于双稳态能量收集结构，提出了变势能的概念。变势能的双稳态能量收集结构，可以降低势能垒，提高能量收集的效率；提出了四稳态结构压电能量收集结构，发现由于稳态的增多以及势能垒的降低，可以使阱间跳跃容易发生，进而提高输出电压。针对低速流体的动能收集，主要进行了流体激励下的多稳态能量收集结构的设计。对于方形筒的弛振流体能量收集结构进行了势能调节设计，进行了动力学分析及实验验证，结果表明调节势能的弛振结构相比传统的弛振结构，能量收集效率有很大提高；对于低速弱风，提出了颤振双稳态风能能量收集结构，实验结果证明了其可以发生频繁的阱间跳跃，甚至可以达到相干共振。进行了复合式的流体能量收集结构设计，提出了带有弯曲翼的多稳态风能收集结构，开展了理论分析与实验研究，证明了其有效性。提出了多稳态弛振与涡激振动结合的风能收集结构，其可以在低风速与高风速下均保持密集的阱间跳跃，实现大的电能输出。此外，提出了一种带有摆动球的风能收集结构，流体激励两个小球产生运动，然后驱动双稳态能量收集结构振动，实现弱风能量的收集，实验结果表明其在宽风速范围内会发生相干共振。此外，为了提高流体能量收集的效率，提出了一些新型的收集结构，如单摆-竖直梁复合能量收集结构，这种结构存在模态耦合，高阶模态的能量会转移到一阶模态，因此在随机激励下能够产生大位移运动，输出大的电压；还有利用驻极体耦合的压电双折梁能量收集结构，在随机激励下，两个折梁的振动耦合在一起，在一个宽频带内产生大振幅振动，有利于能量收集；还设计了利用结构动态压力收集流体能量的结构，这种结构在外激励下，会产生动态压力，其作用在压电材料上，与传统的梁弯曲压电型能量收集设计相比，会产生更大的电压输出。