超声导波驱动的疏水表面液滴输运行为机理研究

The low-energy-consumption and long-working-length droplet transportation technology has important significance of the frost suppression on cold surface. The ultrasonic guided wave and hydrophobic surface are combined to be used in the high-efficiency transportation and removal of droplets. Focusing on the oblique plate/circular tube, the theoretical model of ultrasonic guided wave transportation will be firstly established, which is the basis of the selection strategy investigation of mode/frequency selection of ultrasonic guided wave. Then the numerical and experimental investigation of the kinematics and dynamics features of single droplet on the surface under the effect of ultrasonic guided wave will be conducted and the ultrasonic radiation force conditions resulting in the single droplet rolling and sliding will be analyzed. On the above basis, the transportation effect of ultrasonic guided wave on time/space/scale non-uniform distributed droplet will be studied and it will be established that the technical strategies of droplet removal in the early stage of frost formation. According to the synergistic effect of ultrasonic guided wave and hydrophobic surface, on the one hand, the combinatorial effect of the substrate surface vibration and droplets movement strategy will be optimized and the droplet removal technology with lowest ultrasonic energy will be established; On the other hand, the ultrasonic actuation strategy with long-distance and low energy consuming will be designed to largely enhance the transportation and removal efficiency of droplet. The research work has direct relationship with many fields of production and living which is involved in frost suppression and defrosting. Furthermore, the results can also provide guidance on structure deicing, active desiccation and other industrial applications.

低能耗、长工作距离的液滴输运技术对冷表面高效抑霜具有重要价值。本项目研究利用超声导波联合疏水表面对液滴群进行高效输运和去除。针对表面疏水的倾斜薄板/圆管结构，首先建立超声导波传播的理论模型并据此研究导波模式／频率的选择策略；其次考虑结构表面存在单个液滴，理论和实验研究超声导波作用下液体的运动学和动力学行为，分析超声辐射力使液滴发生滑动和滚动的条件；以此为基础，研究导波对时间／空间／尺寸不均匀分布的大规模液滴群的输运作用，建立在成霜早期进行液滴去除的技术方案。通过超声导波和疏水表面协同作用，一方面对结构表面振动和液滴运动策略进行组合优化，形成一种“最低超声能耗”的除液技术；另一方面，设计一种传播距离长、耗散低的导波激发方案，大幅度提高液滴输运和去除效率。项目研究结果可直接应用于涉及冷表面抑/除霜的多个生产生活领域，也可为结构除冰、主动干燥等工业应用提供借鉴。

结霜现象广泛存在于制冷低温、空调系统、冷藏运输、航空航天等生产生活众多领域，具有严重危害。实现对液滴输运对高效的抑/除霜具有重要价值。本项目依托声学、相变动力学、热力学、界面科学、材料学等交叉学科相关理论，对超声导波激励金属表面液滴的作用机制及作用效果进行了理论及实验研究。本项目研究表明利用超声导波联合疏水表面作用于液滴，可实现对液滴的高效输运和去除。首先通过分析超声导波模式特性，结合推导出的超声换能器声压方程及适用于一阶问题和二阶问题的液滴声场控制方程，建立了超声导波激励液滴的理论模型，依据该理论模型研究了导波模式／频率的选择策略。建立了超声兰姆波作用于金属表面的液滴二维数值模拟，并进行了验证，获得了超声兰姆波频散曲线、平面活塞换能器声场以及液滴内二维声场，获得了超声兰姆波激励液滴内部所产生的声压、声速和声场特性，研究结果揭示了兰姆波模式、质点振幅、粒子半径、声辐射力的影响机制，发现了超声兰姆波激励液滴的本质特性。其次考虑结构表面存在单个液滴，设计并搭建了超声导波激励液滴可视化实验观测平台，实验研究了导波参数、表面结构参数、超声换能器等对液滴声流场的影响特性，揭示超声导波激励液滴的规律及特性。以此为基础，研究超声导波疏水表面耦合作用下，单个液滴及时间／空间／尺寸不均匀分布的液滴群的输运特征，分析了液滴运动、汇聚的运动学/动力学行为，掌握了超声导波作用下疏水表面单个液滴及液滴群输运行为特征及影响规律，实现了对液滴的高效输运和去除。此外，针对驱动液滴较小超声能耗技术方案进行了探索性研究。本研究为超声导波和疏水表面协同作用下，成霜早期液滴去除技术方案的建立提供了理论和技术策略，项目研究结果对于涉及冷表面抑/除霜的多个生产生活领域具有重要参考价值，也为除冰、主动干燥等工业应用提供借鉴。