Micro-Plasmas Through Porous Media

多孔介质可以被认为是对流体流动（例如气体或液体）基本上是透明的材料。这种材料的内表面积很大，使其非常适合化学加工应用。多孔介质在现代社会中发挥着重要作用，其应用范围从水过滤，如活性炭过滤器，到空气过滤。事实上，催化转化器利用多孔介质的高表面积体积比来实现汽车尾气的高减排效率。多孔介质的新兴应用包括燃料电池和清洁燃烧。多孔介质的燃烧尤其发生在孔隙中。在那里释放的能量提高了介质温度，因此注入的燃料在进入时自动点燃。这项技术有可能减少汽车排放，并通过非常稀薄的燃料燃烧显着提高燃油效率。在孔隙中引入少量电离气体，即微等离子体，可以进一步降低点火温度，从而进一步提高效率。此外，在孔隙中产生的反应性微等离子体有可能分解有毒的燃烧副产物，并清洁孔隙，从而大大提高使用寿命。目前，人们对多孔介质中微等离子体的产生还不是很了解。本研究旨在通过实验与模拟相结合的方法，提高对多孔介质中微等离子体产生的认识，并对其进行优化。这项工作的目标是弥合对多孔介质中等离子体产生的科学理解与实际应用之间的差距。从这项工作中获得的理解有助于开发和实现清洁燃烧，高效，低排放的汽车，先进的燃料电池和先进的工业烟囱洗涤器。在可靠地控制和利用多孔介质中的微等离子体（MPPM）之前，有必要对导致等离子体在孔与孔之间相互连接传播的物理条件有一个基本的了解。我们期望孔隙间的扩散输运和孔隙内等离子体雪崩的结合，以及表面电荷和辐射输运的增强，在相邻孔隙间建立等离子体互联性中起关键作用。然而，现在很少有实验或理论证实这些或其他理论。在本研究项目中，我们将研究大气压等离子体在化学反应环境中进入和通过多孔介质传播的基本特性。目标是通过综合实验测量和第一性原理、流体、混合和动力学建模相结合的合作研究，提高我们对导致MPPM的等离子体表面相互作用的理解。我们将研究两种构型。第一种是结构多孔材料，由填充床反应器表示，该反应器由介电珠或棒组成，介电珠或棒具有可控的半径、介电常数、电导率和放置在金属电极之间的布局。第二种配置将是真正随机结构的多孔材料，陶瓷和/或金属泡沫，正如商业上可用的那样。该项目还包括针对低收入学生的K-12外展工作。该课程旨在通过动手实验和科学课程模块向学生介绍等离子体科学和等离子体辅助燃烧的新兴领域。

Porous media may be thought of as material that is essentially transparent to fluid flow (e.g. gas or liquid). The internal surface area of such materials is substantial, making the material excellent for chemical processing applications. Porous media play an important role in modern society with applications ranging from water filtration, such as activated charcoal filters, to air filtration. Indeed, a catalytic converter exploits porous media's high surface area to volume ratio to achieve high emission reduction efficiency in automobile exhausts. New and emerging applications of porous media include fuel cells and clean combustion. Porous media combustion in particular takes place in the pores. The energy released there elevates the medium temperature so that injected fuel automatically ignites upon entry. This technology has the potential to reduce auto emissions and significantly increase fuel efficiency by enabling very lean fuel burns. The introduction of small amounts of ionized gas, a micro-plasma, inside the pores can further reduce ignition temperature thereby allowing for further increases in efficiency. Additionally, reactive micro-plasmas produced in the pores have the potential to decompose toxic combustion byproducts as well as to clean the pores to greatly improve service lifetime. Currently, the micro-plasma production in porous media is not well understood. This effort aims to improve the understanding and optimize the production of micro-plasmas in porous media by using a combination of experiments and simulations. The goal of the effort is to bridge the gap between scientific understanding of plasma production in porous media and actual applications. The understanding obtained from this effort contributes to the development and realization of clean burning, highly efficient, low emission automobiles, advanced fuel cells and advanced industrial smoke stack scrubbers. A fundamental understanding of the physical conditions that lead to interconnected plasma propagation from pore to pore is necessary before one can credibly control and thus exploit micro-plasmas in porous media (MPPM). We expect that a combination of diffusive transport between pores and plasma avalanche within the pores, augmented by surface charging and radiation transport, play key roles in establishing plasma interconnectivity between adjacent pores. However there is now little experimental or theoretical confirmation of these or other theories. In this research project, we will investigate the basic properties of atmospheric pressure plasmas propagating into and through porous media in chemically reacting environments. The goals are to improve our understanding of plasma-surface interactions, which lead to MPPM, through a collaborative investigation combining comprehensive experimental measurements and first-principles, fluid, hybrid and kinetic modeling. Two configurations will be studied. The first is a structured porous material represented by a pack-bed reactor consisting of dielectric beads or rods having a controlled radius, permittivity, conductivity and layout placed between metal electrodes. The second configuration will be a truly randomly structured porous material, ceramic and/or metal foam, as is commercially available. The project also includes a K-12 outreach effort targeting low-income students. The effort aims to introduce the students to plasma science and the emerging field of plasma-aided combustion through both hands on experiments and science lesson modules.