流致振动能量收集的钝头体几何设计研究

THE EFFECT OF GEOMETRIC FEATURE OF BLUFF BODY ON FLOW-INDUCED VIBRATION ENERGY HARVESTING

流致振动蕴含着可观的能量,通过能量收集技术可将其转化为电能.为提高低速流场中能量转化效率,本文实验研究了不同截面下钝头体以及它们的宽厚比(W/T)对流致振动能量收集特性的影响,并通过计算流体动力学(computational fluid dynamic, CFD)仿真分析了尾流特性.流致振动能量收集装置由压电悬臂梁和不同截面的钝头体构成.首先搭建了流致振动能量收集风洞实验平台,钝头体的截面分别设置为矩形、三角形和D形,宽厚比分别设定为1, 1.3, 1.8和2.5.然后利用实验方法分析不同形状钝头体的宽厚比(W/T)对位移响应和电压响应的影响规律.最后通过计算流体动力学模拟揭示实验结果的内在力学机理.实验结果表明,当钝头体截面为矩形时,增大宽厚比可以显著提高电压输出峰值;当钝头体为三角形和D形时,增加宽厚比将使系统呈现"驰振"→"驰振+涡激振动"→"涡激振动"响应特性变化趋势,提高了低风速时的能量收集效果. CFD结果解释了实验现象,即随着宽厚比增加,钝头体尾流会产生更加强劲的涡街,显著提高流致振动能量收集效果.相关结果可优化流致振动能量收集装置结构,为提高低速流场的能量收集效果提供理论和实验依据.

Flow-induced vibration contains considerable energy, which can be converted into electrical energy through energy harvesting. To improve the energy conversion efficiency in low-speed flow fields, the influence of bluff body and the ratio between width and thickness(W/T) on flow-induced vibration energy harvesting performance under different cross-sections was investigated experimentally, and the wake characteristics were analyzed by computational fluid dynamics(computational fluid dynamic, CFD) simulation. The energy harvesting device consists of a piezoelectric cantilever beam and a bluff body with various cross-sections. Firstly, according to the flow-induced vibration theory, a wind tunnel experimental platform for flow-induced vibration energy harvesting was built. The section of the bluff body is set to be rectangular, triangular and D-shaped, and the ratio of width to thickness is set to 1, 1.3, 1.8 and 2.5,respectively. The influence of W/T of the bluff body on the flow-induced vibration energy harvesting was analyzed experimentally. Finally, the insight mechanism of the experimental results is revealed through the computational fluid dynamics simulation. If the section of bluff body is rectangular, increasing the value of W/T will significantly increase the maximum output voltage. However, if the section of bluff body is triangular and D-shape, the vortex-induced vibration(VIV) will occur in the low flow speed region with the increase of W/T, which could improve the energy harvesting effect for low wind speed. The experimental results can be revealed by the related CFD simulation. As the CFD simulation at U = 3 m/s shows, with the increase of W/T, the configuration will lead to more powerful vortex streets, which can significantly enhance the energy harvesting performance of flow-induced vibration. This study can provide a theoretical and experimental basis for the structure optimization of flow-induced vibration energy harvesters and improve the energy conversion efficiency for the low-speed wind.