CAREER: Gas-Liquid Interface Dynamics and Dissipation Mechanisms in Capillary-Scale Two-Phase Flow

CBET-0748049大系统中的Allen两相流一直是流体力学和传热学领域的重要研究课题。MEMS分析设备、微型热交换器、空间处理和热控制技术以及燃料电池等陆基技术的进步突出表明，需要更好地了解具有强大毛细管组件的气液两相流动。由于不能很好地考虑毛细管力、弯月面运动引起的耗散和气液界面相互作用的影响，为小规模系统开发通用流型图的尝试失败了。PI将在毛细管尺度上对两相流动进行系统的实验和分析研究，并开发工程设计工具。为大学预科、本科生和研究生提供的教育机会贯穿整个研究项目。前三个重叠的研究阶段包括研究气液界面动力学的定性实验和高速共聚焦显微镜技术的发展。该计划的第二阶段侧重于利用高速共聚焦显微镜技术在动态气液界面附近进行微粒子图像测速(Micro-PIV)的定量研究；这是目前任何现有的Micro-PIV方法都无法到达的流动区域。第二阶段的分析和实验研究将分离和量化表面张力、界面曲率、界面剪切、气相惯性和可压缩性、弯月运动引起的流体动力耗散以及动态接触线对微通道内两相流动形态的影响。所有这些效应在毛细管尺度的两相流中都观察到了，但没有被量化。第三阶段将构建和测试用于设计和开发先进技术的预测工具，并改进水管理战略，以实现更可靠的燃料电池运行。研究结果将有助于汽车燃料电池的开发，在汽车燃料电池中，无法有效管理氢-氧反应产生的水是大规模部署的主要困难之一。这项研究的影响有教育方面和社会方面。研究生和本科生培养是这项工作的重要组成部分。学生将通过现有的密歇根理工教育合作伙伴关系从代表性不足的群体中招生。这项研究的教育方面的一个关键要素是对研究生到本科生以及本科生到预科学生的分层指导，学生通过示范和向其他学生的指导来学习。先进技术的开发将产生最明显的社会影响；特别是在燃料电池等替代能源转换技术方面。这项研究的结果将是对毛细管力很重要的系统中的两相流动有更全面、更定量的了解，并应用这一理解来促进技术进步，同时培养不断增长的微型设备和燃料电池领域的学生人才。

CBET-0748049AllenTwo-phase flow in large-scale systems has historically been important to the fields of hydrodynamics and heat transfer. Advances in MEMS analytical devices, microscale heat exchangers, space-based processing and thermal control technologies, and terrestrial-based technologies such as fuel cells have highlighted the need for improved understanding of gas-liquid flow with a strong capillary component. Attempts at developing universal flow regime maps for small scale systems have been unsuccessful due to the inability to properly account for the effects of capillary forces, dissipation due to menisci motion and gas-liquid interface interaction. The PI will conduct a systematic experimental and analytical investigation of two-phase flow at the capillary scale and develop engineering design tools. Educational opportunities for pre-college, undergraduate and graduate students are integrated throughout the research program. The first three overlapping research phases consists of qualitative experiments to study gas-liquid interface dynamics and development of a high-speed confocal microscopy technique. The second phase of this program focuses on quantitative studies utilizing the high-speed confocal microscopy technique for micro-Particle Image Velocimetry (micro-PIV) near dynamic gas-liquid interfaces; a region of flow not accessible with any currently available micro-PIV methods. The analytical and experimental studies of the second phase will isolate and quantify the effects of surface tension, interface curvature, interface shear, gas phase inertia and compressibility, hydrodynamic dissipation due to menisci motion and dynamic contact lines on the morphology of the two-phase flow through microchannels. All of these effects have been observed in capillary-scale two-phase flow, but not quantified. The third phase will construct and test predictive tools for design and development of advanced technologies and to improve water management strategies for more reliable fuel cell operation. The results of research will help in development of automotive fuel cells where inability to effectively manage the water produced by the hydrogen-oxygen reaction constitutes one of the major difficulties in mass deployment. Impacts of this research have an educational aspect and a societal aspect. Graduate and undergraduate student training is an important part of this work. Students will be recruited from under-represented groups through existing Michigan Tech educational partnerships. A key element of the educational aspect of this study is the tiered mentoring of graduate to undergraduate students and undergraduate to pre-college students where students learn through demonstration and instruction from other students. The societal impact will be most evident in advanced technology development; particularly with respect to alternative energy conversion technologies such as fuel cells. The results of this study will be a more thorough, quantitative understanding of two-phase flow in systems where capillary forces are important and application of this understanding to advance technology while developing student talent in the growing field of microscale devices and fuel cells.