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微粒排放对健康的不利影响。这些小于2.5微米的细颗粒物与过早的心血管和呼吸道死亡以及肺癌有关。虽然静电除尘在1824年首次被证明，但迄今为止，使用该技术去除燃烧颗粒物仅限于能够容纳大型二级处理装置的大型发电厂。缩小这项技术的总体尺寸是必要的，以开辟静电除尘在移动的源，如船舶和卡车的新的应用。我们的方法静电除尘使用等离子体（过热状态的物质）与超高频高压脉冲代表了一个新的应用旧技术。初步结果显示，在减少颗粒物排放方面有很大的希望，但对潜在的机制知之甚少。本项目的目标是解决这些知识差距，并确定等离子体增强静电除尘中颗粒物去除的机制。如果成功的话，这种方法将能够开发出更紧凑的静电除尘器，这可能会改变移动的污染源的柴油机微粒减排技术。对社会的进一步好处来自于对洛杉矶地区高中教师的外展，以改善代表性不足的学生的STEM教学。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，纳秒高压脉冲等离子体在去除柴油发动机微粒方面比传统的静电除尘器有显着的增强。然而，这种增强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除尘方法的应用。为实现这一目标而设计的具体研究目标包括：i）纳秒高压脉冲放电产生的离子迁移率和物种的光谱检查，ii）尺寸依赖的颗粒电荷分布的表征，iii）纳秒高压脉冲静电除尘的多物理场计算流体动力学建模，以及iv）流光在ESP过程中的作用的调查。从这个系统的研究结果将提供等离子体增强静电除尘过程的机理洞察。这些信息对于设计克服当前限制并进一步提高颗粒去除效率的系统是必要的。这项工作的性质本质上是跨学科的，涉及高压电子学，静电学和流体动力学，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NSF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.