Cavitation on MicroElectro Mechanical Systems

微机电系统中的空化

• 批准号: 0520604
• 负责人: Yoav Peles
• 金额: --
• 依托单位: Rensselaer Polytechnic Institute
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-08-15 至 2007-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0520604&HistoricalAwards=false
• 关键词: Cavitation; MicroElectro; Mechanical; Systems

ABSTRACT - 0520604Rensselaer Polytechnic InstituteThe proposed research will greatly advance the exceedingly limited fundamental knowledge ofcavitation in microsystems through a meticulous study of cavitating flows in rudimentary micro scale configurations such as orifices and venturis. Establishing a micro-scale cavitation knowledge base will ameliorate the design of numerous innovative microfluidic systems, such as micro-rockets, micro-coolers, micro-refrigerators, micro mixers, drug delivery systems, micro power systems including launch vehicles and high density power sources, electronic chip cooling systems, chemical micro-reactors, DNA synthesis assays and bio-MEMS systems. The current state-of-the-art technology in MEMS has enabled the integration and assembly of assorted independent micro components such as pump, valves, and nozzles into complex high-speed microfluidic machines. These neoteric systems posses geometrical dimensions in the range of 1-1000 microns, which are 103-104 times less than conventional machines, and operate at liquid flow speeds up to 300 m/s. Recent studies performed by our group on cavitation in Microsystems have yielded unexpected results and major deviations from conventional scale behavior. Therefore, an extensive scientific investigation of cavitation in microfluidic systems is exigent and imperative for the pragmatic realization of numerous novel micro machines.Cavitation, the formation of vapor pockets in liquid when the pressure falls below the vapor pressure, has long been a concern in the engineering of fluid machines. The deleterious effects of cavitation on conventional fluid machinery are well documented and have been aggressively researched in the last century. Cavitation in hydraulic machinery can limit performance, lower efficiency, modify the hydrodynamics of the flow, introduce severe structural vibration, generate acoustic noise, choke flow and cause catastrophic damage. Research on cavitation has contributed immensely towards improving the design of macro-scale hydraulic machinery. In the current scenario, it is indeed tempting to scale down the available information on cavitation in macro-scale machinery and employ it in the design of microscale devices. Although concomitant scaling effects of cavitation have been investigated, they are at best applicable for scaling between prototypes and real-world paragons at the macro-scale. Thus, the objectives of this research are to establish quantitative and qualitative understanding of nuclei effects on cavitation in microsystems, to assess the applicability of conventional scale models to predict cavitation inception in micro devices, and to study cavitating flow mechanisms pertinent to microfluidic systems under various conditions. To accomplish these objectives, a comprehensive experimental investigation is proposed. The proposed work will involve microfabrication and subsequent experiments on micro venturis and microorifices with various surface (topography and chemistry) and flow (stream nuclei) conditions, over a range of hydraulic diameters, surface geometries and dimensions, flow rates, pressures, and power levels. Two commonly encountered working fluids (ethanol and water) will be employed in this study. Highspeed, microscopic flow visualization studies will be undertaken to complement the quantitative measurements. Both cavitation inception and developed cavitation for various surfaces and flow conditions will be studied and flow patterns will be mapped under various flow conditions. The results will then be compared against models developed for conventional scale systems. All these tasks will provide means to enhance the understanding and unveil the mechanism of cavitation in microsystems.The Intellectual merit of the proposed research will be to establish pioneering engineeringknowledge quantifying the effects of surface topography and chemistry and stream nuclei on cavitation in microsystems. The derived engineering information will greatly clarify the role played by surface and stream nuclei in cavitation inside microsystems, and provide guidelines to properly design micro power devices. Additionally, this research work will stimulate research on cavitation in microsystems.The Broader impact of this research will be to provide vital scientific information to the MEMS and cavitation community and highlight the pernicious effects of cavitation in microsystems via seminars and presentations at national and scientific forums. Additionally, the proposed work will educate one minority female graduate student (from the University of Puerto Rico-Mayaguez) in the emerging field of MEMS technology, especially high-speed microfluidics. The results from the proposed research endeavor will be disseminated in archival journal and conference publications, and will also be incorporated into the undergraduate and graduate courses taught by the PI.

摘要-0520604伦斯勒理工学院通过对微小尺度结构如小孔和文氏管中空化流动的细致研究，这项研究将极大地推进微系统中空化的极其有限的基础知识。建立微尺度空化知识库将改进许多创新微流体系统的设计，例如微型火箭、微型冷却器、微型制冷机、微型混合器、药物输送系统、包括运载火箭和高密度电源的微型动力系统、电子芯片冷却系统、化学微反应器、DNA合成测定和生物MEMS系统。目前MEMS的最新技术已经能够将各种独立的微部件（如泵、阀和喷嘴）集成和组装到复杂的高速微流体机器中。这些新系统的几何尺寸在1-1000微米的范围内，比传统机器小103-104倍，并且在高达300 m/s的液体流速下操作。我们小组最近对微系统中的空化现象进行的研究产生了意想不到的结果和与传统尺度行为的重大偏差。因此，对微流体系统中的气穴现象进行深入的研究，对于实现各种新型微机械具有重要意义。气穴现象是指当压力福尔斯蒸汽压时，液体中形成的汽囊，它一直是流体机械工程中的一个重要问题。在上个世纪，空化对传统流体机械的有害影响得到了很好的证明，并得到了积极的研究。水力机械中的气穴会限制性能、降低效率、改变流体的流体动力学、引起严重的结构振动、产生噪声、阻塞流动并导致灾难性的损坏。空化的研究对改进大型水力机械的设计做出了巨大贡献。在目前的情况下，它确实是诱人的按比例缩小现有的信息空化在宏观尺度的机械和使用它在设计中的微尺度设备。虽然已经研究了空化的伴随缩放效应，但它们最多适用于宏观尺度上原型和真实世界的典范之间的缩放。因此，本研究的目标是建立定量和定性的理解核的空化效应在微系统中，以评估传统的规模模型的适用性，预测在微器件中的空化开始，并研究空化流动机制相关的微流体系统在各种条件下。为了实现这些目标，提出了一个全面的实验研究。拟议的工作将涉及微文氏管和微孔与各种表面（地形和化学）和流动（流核）条件下，在一系列的水力直径，表面几何形状和尺寸，流速，压力和功率水平的微细加工和后续实验。两种常见的工作流体（乙醇和水）将在这项研究中使用。高速，微观流动可视化研究将进行补充定量测量。将研究各种表面和流动条件下的空化起始和发展空化，并绘制各种流动条件下的流型。然后将结果与为传统规模系统开发的模型进行比较。所有这些任务将提供手段，以提高理解和揭示微系统中的空化机制。拟议的研究的智力价值将是建立开拓性的engineeringknowledge量化的表面形貌和化学和流核的影响，在微系统中的空化。所得到的工程信息将大大澄清表面和流核在微系统内空化中所起的作用，并为正确设计微功率器件提供指导。此外，这项研究工作将促进对微系统中空化现象的研究。这项研究的更广泛影响将是为MEMS和空化社区提供重要的科学信息，并通过国家和科学论坛上的研讨会和演讲突出微系统中空化现象的有害影响。此外，拟议的工作将教育一个少数民族女研究生（从波多黎各大学马亚圭斯）在新兴领域的MEMS技术，特别是高速微流体。从拟议的研究奋进的结果将在档案杂志和会议出版物传播，也将被纳入PI教授的本科生和研究生课程。