机械增频式波浪压电发电装置特性的研究

发布时间：2018-04-02 09:51

本文选题：波浪能转换　切入点：压电俘能　出处：《清华大学》2015年博士论文

【摘要】：波浪压电发电为海上远离陆地传感监测仪器的持续供电用电需求提供了新的解决方案。因此,波浪压电发电装置的研发具有十分良好的应用前景,将成为未来海上监测仪器持续供电的发展方向之一。本文研究一种具有自主知识产权的新型压电式波浪能利用装置。该装置采用增频传动将低频不规则的波浪运动转换为发电所需的高频稳定机械振动,利用压电发电实现电能转化。本文采用物理模型试验和数值模拟相结合的方法,围绕波浪、浮体、压电振子和负载间的耦合及相互作用,对装置实现波能到电能的转换特性进行了机理性研究。本文首先基于势波理论和欧拉-伯努利梁理论,建立了时域三维波浪-浮体-振子耦合的数学模型,并通过试验验证了模型的有效性。采用验证的数学模型,探索了振子的杨氏模量、振子数以及波要素对波浪-浮体-振子传动特性的影响规律;发现了振子的振动频率几乎不随入射波波周期的变化而变化,而随振子的材料和结构特性(杨氏模量)的变化而显著变化。随着振子杨氏模量和振子数的增加,表征波浪-浮体-振子耦合作用状态的反弹比增加。当振子杨氏模量和振子数各自超过一定阈值后,“传动+释放”的增频传动机制将失效,浮体与振子进入“缓冲+反弹”的相互作用状态。随着浮体发生反弹的频率增加,传递的振子应变能功率下降。压电振子(在上述振子上下表面粘贴压电薄膜)是实现电能转化的系统单元。压电振子和负载的耦合特性对压电振子的输出功率和转换效率有重要影响。无量纲化的机电耦合系数是表征压电振子所受电致阻尼的重要参数,决定了压电振子的机电转换效率。本文系统地研究了压电薄膜和基板的物理和几何参数对压电振子机电转换特性的影响规律;发现了压电薄膜与振子不等长时能够取得更好的机电耦合特性。在大多数条件下,两者的最适长度比介于0.55和0.75之间。开展了机械增频式波浪压电发电装置性能的物理试验研究,并记录了不同波周期条件下浮体振动和输出电压的历时曲线。考虑了波浪、浮体、振子、压电、负载的相互作用,建立了波浪-浮体-振子-压电-负载的耦合模型。系统地研究了外接电路电阻、压电振子数、压电体长度、压电振子和拨片的初始交叠长度以及波要素变化与系统输出功率的相关关系。研究发现,适当地增加压电振子数不仅能够增加系统的输出功率,同时还能提高装置输出功率的带宽。
[Abstract]:Wave piezoelectric power generation provides a new solution for the continuous power demand of offshore remote land sensor monitoring instruments.Therefore, the research and development of wave piezoelectric power generation equipment has a very good application prospect, which will become one of the development directions of continuous power supply for offshore monitoring instruments in the future.In this paper, a new piezoelectric wave energy utilization device with independent intellectual property rights is studied.In this device, the frequency increasing drive is used to convert the irregular wave motion of low frequency into the high frequency stable mechanical vibration needed for power generation, and the piezoelectric power generation is used to realize the electric energy conversion.In this paper, the coupling and interaction between wave, floating body, piezoelectric oscillator and load are combined with physical model test and numerical simulation. The mechanism of the conversion from wave energy to electric energy is studied.Based on the theory of potential wave and Euler-Bernoulli beam theory, a three-dimensional wave-floating-oscillator coupling mathematical model in time domain is established in this paper, and the validity of the model is verified by experiments.However, the material and structural characteristics (Young's modulus) of the oscillator vary significantly.With the increase of the Young's modulus and the number of oscillators, the rebound ratio of the wave-floating-oscillator coupling state increases.When the Young's modulus and the number of oscillators each exceed a certain threshold, the frequency-increasing transmission mechanism of "transmission release" will fail, and the floating body and the oscillator will enter the interaction state of "buffer rebound".With the increase of the frequency of the floating body rebound, the transmitted oscillator strain energy power decreases.Piezoelectric vibrator (sticking piezoelectric film on the upper and lower surface of the vibrator) is the system unit to realize electric energy conversion.The coupling characteristics of piezoelectric oscillator and load have an important effect on the output power and conversion efficiency of piezoelectric oscillator.The dimensionless electromechanical coupling coefficient is an important parameter to characterize the electrically induced damping of piezoelectric oscillators, which determines the electromechanical conversion efficiency of piezoelectric oscillators.The effect of physical and geometric parameters of piezoelectric film and substrate on the electromechanical conversion characteristics of piezoelectric oscillator is systematically studied, and a better electromechanical coupling property can be obtained when the piezoelectric film and oscillator are unequal in length.In most cases, the optimum length ratio of the two is between 0.55 and 0.75.The physical experiments on the performance of mechanical frequency increasing wave piezoelectric generator are carried out, and the diachronic curves of the vibration and output voltage of the floating body under different wave periods are recorded.The interaction of wave, floating body, oscillator, piezoelectric and load is considered, and a coupling model of wave, floating body, oscillator, piezoelectric and load is established.The dependence of the external circuit resistance, the number of piezoelectric oscillators, the piezoelectric body length, the initial overlap length of the piezoelectric oscillator and the patch, and the variation of the wave elements on the output power of the system are systematically studied.It is found that properly increasing the number of piezoelectric oscillators can not only increase the output power of the system, but also increase the bandwidth of the output power of the device.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TM61

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