【作者】 王岩；

【导师】 潘新祥； 徐敏义；

【作者基本信息】 大连海事大学 ， 轮机工程， 2022， 博士

【摘要】 自然界中蕴藏着多种形式的流动能量,诸如风能和海流能等形式的流动能量由于其蕴藏广泛,储量巨大,绿色无污染的特点,受到了越来越多的关注。流致振动是一种常见的流固耦合现象,同时也是流动能量向结构物振动能量的一种转化方式。流致振动型摩擦纳米发电机可将流致振动过程中产生的振动能高效转化为电能,是一种全新的流动能量收集方式。采用摩擦纳米发电机收集环境中的流动能量,有助于实现传感器节点和传感网络的自供能,对于解决分布式传感节点的供电问题,提升这些传感节点和传感网络的续航能力有着十分现实的应用价值。本文通过设计多种形式的流致振动摩擦纳米发电机,实现了对包括风能和海流能在内的多种形式流动能量的有效收集。研究成果对创新传感系统供能模式、丰富流动能量转换理论具有重要意义。本文的研究工作主要包括以下几方面:（1）设计并构建了一种涡激振动摩擦纳米发电机,并分别研究了结构的振动特性和发电特性。约化速度和质量比是影响其振动特性的关键参数。因此,本文研究了约化速度和质量比对方柱振幅、加速度和锁频区的影响。结果表明方柱的涡激振动分为两个阶段,在初始分支内,约化速度升高,方柱的振幅和加速度都随之增大;而在下部分支内,约化速度继续升高,方柱的振幅和加速度都随之降低。对于高质量比的系统来说,相对较低的质量比的系统可以获得较大的锁频区。质量比为308.57的系统,在锁频区内,聚四氟乙烯小球的数量越多,发电性能越好。而在最大振动范围内,约化速度即使改变,也不会影响其输出,在此区间内发电性能保持稳定。在约化速度在29.49-44.48范围内时,最大输出电压为115V,最大功率密度为62.2 W/m³。（2）设计并构建了一种颤振摩擦纳米发电机,并分别研究了柔性薄膜的振动特性和颤振摩擦纳米发电机的发电特性。材料刚度和薄膜垂跨比是影响其振动的关键参数。因此,本文首先研究了不同材料和垂跨比对薄膜临界速度的影响。结果表明材料刚度和垂跨比越高,其对应的临界风速越高。其次从结构参数和来流条件两方面分析了其对发电性能的影响。结果表明薄膜垂度与结构流道间隙存在对应关系,当其比值为1:2的时候可获得较好的输出性能。当结构尺寸为100×20×3mm时,30m/s的风速下,输出电压的最大值能达到114.1V,输出电流可达17.9μA,最大的功率为5.2m W,对应的功率密度为870 W/m³。在不同来流条件下测试了颤振摩擦纳米发电机的发电性能,其发电性能可随流速的升高而增大;其有效能量收集角度为25°-155°;在10%湍流度范围内,发电性能将随湍流度增大而升高。（3）针对摩擦纳米发电机在工作过程中会受到环境湿度影响的弱点,设计了一种基于颤振现象的旗形防潮摩擦纳米发电机,并分别研究了柔性结构的振动和发电特性。弯曲刚度和质量比是影响其振动的关键参数。因此,本文研究了弯曲刚度和质量比对旗形摩擦纳米发电机振幅、频率和临界速度的影响。结果表明在测试范围内,随着弯曲刚度的降低,旗形摩擦纳米发电机的振幅、振动频率增大,而临界速度随之降低;质量比发生变化时,其振动频率并没有明显变化,斯特劳哈尔数处于0.5-0.6范围内,但质量比增大后,系统对应的临界速度也会升高。其次,研究了弯曲刚度、质量比和相对湿度对其发电性能的影响,在一定范围内降低弯曲刚度和质量比有利于获得较大的输出。由于良好的密封性,旗形摩擦纳米发电机的发电性能并不会随相对湿度的增加而减弱。尺寸为150×75mm的旗形摩擦纳米发电机,优化布置方式后,7.5m/s风速下,最大输出功率为36.72μW,对应功率密度48 W/m³,相比独立布置的旗形摩擦纳米发电机,功率提升了近40倍。（4）结合旗形摩擦纳米发电机防潮抗湿的特性,进一步构建了一种用于收集海流能量的水下旗形摩擦纳米发电机。本文研究了前置钝体、弯曲刚度和质量比对水下旗形摩擦纳米发电机振幅和临界速度的影响。采用前置钝体的方式,可以有效增大其振幅和降低其临界速度,进而增强了其发电性能。同时,弯曲刚度的降低可使水下旗形摩擦纳米发电机的振幅增大和临界速度降低。但质量比增大后,器件对应的临界速也却会降低,这与空气中旗形结构的振动特性存在明显差异。其次,研究了前置钝体、弯曲刚度和质量比对发电性能的影响。结果表明通过前置钝体、降低弯曲刚度、增加质量比可有效提升发电性能。对比了尺寸为(=0.55×10^-4,/（2=4,^*=1270）的水下旗形摩擦纳米发电机和前置钝体的水下旗形摩擦纳米发电机的发电性能。在0.461m/s流速下,前置钝体后水下旗形摩擦纳米发电机的开路电压升高了170%,短路电流和转移电荷量也分别增大了100%和167%。弯曲刚度从1.33×10^-4降低至0.05×10^-4时,输出电压可从6.2V升高至14.4V。在0.461m/s流速下,水下旗形摩擦纳米发电机的质量比从955升高至1590时,短路电流也从0.8μA上升到了1.43μA。尺寸为175×87.5mm的旗形摩擦纳米发电机,最大输出电压为14.4 V,最大输出功率为9.1μW,对应功率密度为22.4 W/m³。更多还原

【Abstract】 There are many forms of fluid energy in nature.Fluid energy in the form of wind energy and ocean current energy has attracted more and more attention due to its wide existence,huge reserves,and pollution-free characteristics.Flow-induced vibration is a common phenomenon of fluid-solid interaction,and it is a way of transforming fluid energy into structural vibration energy.The flow-induced vibration type triboelectric nanogenerator（TENG）can efficiently convert the vibration energy generated in the flow-induced vibration process into electrical energy,which is a new fluid energy harvesting method.Harvesting fluid energy in ambient environment by TENG is helpful for realizing the self-powered of sensor node and sensor network.Effectively harvesting wind energy and ocean current energy has been realized by flow-induced vibration TENG in this paper.The research results are of great significance for innovating the energy supply mode of the sensing system and enriching the theory of fluid energy conversion.The research work of this article mainly includes the following aspects:（1）A vortex-induced vibration triboelectric nanogenerator（VIV-TENG）is designed and constructed.The vibration and power generation characteristics are studied.Reduced velocity and mass ratio are the key parameters that affect its vibration.Hence,this thesis studies the influence of reduced velocity and mass ratio on the amplitude,acceleration and lock-in region.The results show that the vortex-induced vibration of the square cylinder is divided into two branches.In the initial branch,the reduced velocity increases,the amplitude and acceleration of the square cylinder increase accordingly;while in the lower branch,the reduced velocity continues to increase,the amplitude and acceleration of the square cylinder are reduced accordingly.For system with high mass ratio,a larger lock-in region can be obtained by reducing the mass ratio appropriately.For a system with a mass ratio of 308.57,more PTFE balls results in the better the power generation performance within the lock-in region.In the maximum vibration range,even if the reduced velocity is changed,it will not affect its output,and the power generation performance remains stable in this range.When the reduced velocity is within the range of 29.49-44.48,the maximum output voltage is 115V and the maximum power density is 62.2 W/m³.（2）A flutter triboelectric nanogenerator（F-TENG）is designed and constructed.The vibration characteristics of the flexible membrane and the power generation characteristics of the F-TENG are studied respectively.Material stiffness and membrane sag ratio are the key parameters that affect its vibration.Hence,this part first studied the effects of different materials and sag ratios on the critical speed of the membrane.The results show that the higher the material stiffness and sag ratio,the higher the corresponding critical wind speed.Secondly,it analyzes its influence on power generation performance from two aspects of structural parameters and incoming flow conditions.The results show that there is a corresponding relationship between the membrane sag and the gap of the flow channel.When the ratio is 1:2,a better output performance can be obtained.When the structure dimension is 100×20×3mm,at a wind speed of 30m/s,the maximum output voltage can reach about114.1V,the output current can reach 17.9μA,the maximum power is 5.2m W,and the corresponding power density is 870 W/m³.The power generation performance of the F-TENG is tested under different incoming flow conditions.Its power generation performance can increase with the increase of the flow speed;its effective energy harvesting angle is 25°-155°;within the range of 10%turbulence,the power generation performance will increase with the increase of turbulence.（3）A novel moisture-proof flag-type triboelectric nanogenerator（flag-type TENG）is proposed to overcome the disadvantage of weak performance of TENG in humidity condition.The vibration and power generation characteristics of the flexible structure are studied.Bending stiffness and mass ratio are the key parameters that affect its vibration.Hence,this part studies the influence of bending stiffness and mass ratio on the amplitude,frequency and critical speed of the flag-type TENG.The results show that within the test range,as the bending stiffness decreases,the amplitude and vibration frequency of the flag-type TENG increase,while the critical speed decreases.When the mass ratio changes,the vibration frequency does not change significantly.The Strouhal number is in the range of 0.5-0.6,but when the mass ratio increases,the critical speed corresponding to the system will also increase.Secondly,the influence of bending stiffness,mass ratio and relative humidity on its power generation performance is studied.It is beneficial to reduce the bending stiffness and mass ratio within a certain range to obtain a larger output.Due to the waterproof ability,the power generation performance of the flag-type TENG will not decrease with the increase of relative humidity.After optimizing the layout,the output of the flag-type TENG with a dimension of 150×75mm can reach 36.72μW,corresponding to a power density of48 W/m³.Compared with the independently arranged flag-type TENG,the power is increased by nearly 40 times.（4）Combining the water-proof characteristics of the flag-type TENG,an underwater flag-shaped triboelectric nanogenerator（UF-TENG）for harvesting ocean current energy is further constructed.The combined structure of flexible electrodes printed with conductive ink,dielectric materials and waterproof tape realizes the harvesting of ocean current energy at extremely low flow speed.This part studies the influence of front bluff body,bending stiffness and mass ratio on the amplitude and critical speed of the UF-TENG.The use of a front bluff body can effectively increase its amplitude and reduce its critical speed.In turn,its power generation performance is enhanced.Meanwhile,as the bending stiffness decreases,the amplitude of the UF-TENG increases and the critical speed decreases.When the mass ratio increases,the critical speed corresponding to the system will decrease,which is obviously different from the vibration characteristics of the flag-type TENG in the air.Secondly,the influence of front bluff body,bending stiffness and mass ratio on power generation performance is studied.The results show that the front bluff body can effectively improve the power generation performance by reducing the bending stiffness and increasing the mass ratio.The UF-TENG with=0.55×10^-4,/(2=4,^*=1270 is compared with the UF-TENG installed with a bluff body ahead.At a flow speed of 0.461m/s,the open circuit voltage of the UF-TENG with a front bluff body can be increased by 170%,and the short-circuit current and the amount of transferred charge have also increased 100%and 167%,respectively.When the bending stiffness is reduced from 1.33×10^-4 to 0.05×10^-4,the output voltage can be increased from 6.2V to 14.4V.At a flow speed of 0.461m/s,when the mass ratio of the UF-TENG increases from 955 to 1590,the short-circuit current also rises from0.8μA to 1.43μA.The UF-TENG with a dimension of 175×87.5mm has a maximum output voltage of 14.4 V,a maximum output power of 9.1μW,and a corresponding power density of 22.4 W/m³.更多还原