Collaborative Research: Plasma-enhanced Electrostatic Precipitation of Diesel Particulates using High Voltage Nanosecond Pulses

在过去的几十年里，许多毒理学研究已经确定了柴油发动机颗粒物排放对健康的不利影响。这些小于2.5微米的细颗粒物与心血管和呼吸系统过早死亡以及肺癌有关。虽然静电沉淀法在1824年首次被证明，但到目前为止，使用该技术去除燃烧颗粒的技术仅限于能够容纳大型二级处理设备的大型发电厂。减小该技术的整体尺寸对于在船舶和卡车等移动源中开辟静电沉淀的新应用是必要的。我们利用等离子体（物质的过热状态）和超高频高压脉冲进行静电沉淀的方法代表了一种旧技术的新应用。初步结果显示，在减少颗粒物排放方面有很大的希望，但其潜在机制尚不清楚。该项目的目标是解决这些知识空白，并确定在等离子体增强静电沉淀中去除颗粒的机制。如果成功，这种方法将有助于开发更紧凑的静电除尘器，这可能会改变移动源的柴油颗粒减缓技术。与洛杉矶地区的高中教师接触，为代表性不足的学生改善STEM教学，这对社会有进一步的好处。通过专业协会的推广将改善化学教学，并为本科生提供研究机会，从而提高科学素养。研究小组的初步结果表明，纳秒级高压脉冲等离子体在去除柴油机微粒方面比传统的静电除尘器有显著的增强。然而，这种增强背后的基本机制仍然知之甚少。本研究的总体目标是探索等离子体增强纳秒高压脉冲放电作为一种新的静电沉淀方法的应用。为实现这一目标而设计的具体研究目标包括：1)纳秒级高压脉冲放电产生的离子迁移率和种类的光谱检测；2)尺寸相关粒子电荷分布的表征；3)纳秒级高压脉冲静电沉淀的多物理场计算流体动力学建模；4)研究拖缆在ESP过程中的作用。该系统研究的结果将为等离子体增强静电沉淀过程提供机理见解。这些信息对于设计克服当前限制和进一步提高颗粒去除效率的系统是必要的。这项工作本质上是跨学科的，涉及高压电子学，静电学，流体动力学，以及燃烧和气溶胶科学。该项目汇集了具有互补专业知识的研究人员来进行研究，并为学生研究人员提供合作培训机会。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The adverse health effects of diesel engine particulate emissions have been firmly established by many toxicological studies over the past few decades. These fine particulates smaller than 2.5 microns have been linked to premature cardiovascular and respiratory deaths, as well as lung cancer. While electrostatic precipitation was first demonstrated in 1824, thus far, use of the technology to remove combustion particulates has been limited to large power plants that can accommodate large secondary treatment devices. Reducing the overall size of this technology is necessary to open up new applications for electrostatic precipitation in mobile sources, such as ships and trucks. Our approach to electrostatic precipitation using plasma (a superheated state of matter) together with ultra-high frequency high voltage pulsing represents a novel application of an old technology. Preliminary results have shown significant promise in reducing particulate emissions, but the underlying mechanisms are poorly understood. The goal of this project is to address these knowledge gaps and identify the mechanisms for particulate removal in plasma enhanced electrostatic precipitation. If successful, this approach will enable development of much more compact electrostatic precipitators that could potentially transform diesel particulate mitigation technology for mobile sources. Further benefits to society result from outreach to high school teachers in the Los Angeles area to improve STEM teaching for underrepresented students. Outreach through professional societies will improve chemistry teaching and provide research opportunities for undergraduate students, thus improving scientific literacy.Preliminary results by the research team show that nanosecond high voltage pulsed plasma provides significant enhancement over conventional electrostatic precipitators in removing diesel engine particulates. However, the fundamental mechanism(s) underlying this enhancement remain poorly understood. The overall goal of this research is to explore the application of plasma enhanced nanosecond high voltage pulsed discharges as a novel approach for electrostatic precipitation. The specific research objectives designed to achieve this goal include: i) spectroscopic examination of ion mobilities and species generated by nanosecond high voltage pulse discharge, ii) characterization of size-dependent particle charge distributions, iii) multi-physics computational fluid dynamics modeling of nanosecond high voltage pulse electrostatic precipitation, and iv) investigation of the role of streamers in the ESP process. Results from this systematic study will provide mechanistic insight into the plasma enhanced electrostatic precipitation process. Such information is necessary to design systems to overcome current limitations and further improve particle removal efficiency. The nature of this work is inherently interdisciplinary, involving high voltage electronics, electrostatics, and fluid-dynamics, as well as combustion and aerosol science. This project brings together researchers with complimentary expertise to perform the research, as well as provide collaborative training opportunities for the student researchers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.