Investigation of fragmentation during soot oxidation

烟灰氧化过程中碎片的研究

• 批准号: 1133480
• 负责人: Kerry Kelly
• 金额: $ 27.65万
• 依托单位: University of Utah
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-01 至 2015-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1133480&HistoricalAwards=false
• 关键词: Investigation; fragmentation; during; soot; oxidation

1133480LightySoot formation and oxidation are important because of soot's adverse health effects, role in climate forcing, and importance to ambient air quality and visibility. The adverse health effects of soot have been reported by numerous researchers. Soot has been implicated in climate forcing; however, its actual contribution is still somewhat uncertain. Manufacturers of air pollution control equipment, i.e. diesel particulate filters, are also interested in understanding the rates and mechanisms of soot oxidation at lower temperatures.Previous work has identified the fragmentation of soot particles under various combustion conditions, including high soot burnout (70% carbon burned) and low burnout, close to the burner (about 10% carbon burned) in a high temperature, flame environment. In addition, recent modeling has identified the importance of fragmentation in predicting the particle size distribution and other soot properties. However, little experimental data exist for fully understanding the conditions under which fragmentation potentially occurs and the mechanisms. Others have suggested that oxygen diffuses into the particles which allows for internal burning, breaking apart the soot agglomerate. The proposed work has the following three objectives:Objective 1. Identify the conditions, i.e. temperatures, equivalence ratios, radical pool, etc. where fragmentation occurs for ethylene flames at both low burnout and high burnout;Objective 2. Determine the mechanisms of fragmentation, such as oxygen diffusion in breaking of bridges and soot particle break down; Objective 3. Perform tests on surrogate liquid fuels to determine the applicability of the mechanisms identified in Objective 2 to these fuels and the role of aromatic versus aliphatic components.The experiments will be conducted in a two-stage, premixed burner system which can be used for both gaseous and liquid fuels. In this system the first burner generates soot, while the second burner is used to oxidize the soot under various temperatures and equivalence ratios. A Scanning Mobility Particle Sizer (SMPS), with a size range of 3-100 nm, will be used to determine particle size distributions as a function of height above burner. When needed, long-differential mobility analyzer measurements can extend the range to 660 nm. Gas-phase concentrations of key components (i.e. O2, H2, CO, CO2) and temperature profiles will be taken. Objective 1 will use ethylene to gather the data and develop mechanisms, while Objective 3 will explore liquid fuels. Utilizing TEM and HR-TEM and particle size distribution data, we will explore in Objective 2 the oxidation of "bridge" material between particles via oxygen diffusion and also increases in particle porosity which can lead to particle fragmentation. The intellectual merit of the study is in understanding the mechanisms of soot fragmentation during oxidation and the conditions under which it is likely to occur. The novelty of the work is exploring the phenomenon under the two scenarios: high and low soot burnout. Furthermore, soot oxidation has not been studied in depth, and recent advances in particle measurements can add to the existing knowledge. The data can be used to modify oxidation mechanisms which, when used in simulations, will more accurately predict the structure, size distribution and mean properties of soot as it oxidizes. In addition, this project will begin to address the role of different fuel constituents in fragmentation. The broader impacts are realized when industry can apply these fundamentals to their systems to reduce soot emissions, important to protect human health and to better understand/mitigate climate forcing. On the other hand, for industries producing carbon black, these data will add to the existing knowledge base of soot formation/oxidation.

1133480 LightySoot的形成和氧化是重要的，因为煤烟的不利健康影响，在气候强迫中的作用，以及对环境空气质量和能见度的重要性。 许多研究人员已经报道了煤烟对健康的不利影响。 煤烟与气候强迫有牵连;然而，其实际贡献仍然有些不确定。空气污染控制设备（即柴油机微粒过滤器）的制造商也有兴趣了解在较低温度下碳烟氧化的速率和机理。先前的工作已经确定了在各种燃烧条件下碳烟颗粒的破碎，包括在高温火焰环境中的高碳烟燃尽（70%碳燃烧）和靠近燃烧器的低燃尽（约10%碳燃烧）。 此外，最近的建模已经确定了预测颗粒尺寸分布和其他烟尘性质的破碎的重要性。 然而，很少有实验数据存在充分了解的条件下，可能发生的碎裂和机制。 另一些人认为，氧气扩散到颗粒中，这使得内部燃烧，使烟灰聚集体破裂。 拟议的工作有以下三个目标：目标1。 确定乙烯火焰在低燃尽和高燃尽时发生碎裂的条件，即温度、当量比、自由基池等;目标2。确定破碎的机制，如氧扩散中的桥梁和烟灰颗粒打破;目标3。 对替代液体燃料进行试验，以确定目标2中确定的机理对这些燃料的适用性，以及芳香族组分与脂肪族组分的作用。试验将在两级预混燃烧器系统中进行，该系统可用于气体和液体燃料。 在该系统中，第一燃烧器产生烟灰，而第二燃烧器用于在各种温度和当量比下氧化烟灰。将使用尺寸范围为3-100 nm的扫描迁移率粒度分析仪（SMPS）测定粒度分布与燃烧器上方高度的函数关系。需要时，长差分迁移率分析仪测量范围可扩展至660 nm。 将采集关键组分（即O2、H2、CO、CO2）的气相浓度和温度曲线。目标1将使用乙烯收集数据并开发机制，而目标3将探索液体燃料。利用TEM和HR-TEM以及粒度分布数据，我们将在目标2中探索通过氧扩散的颗粒之间的“桥”材料的氧化以及颗粒孔隙率的增加，这可能导致颗粒破碎。 这项研究的智力价值在于了解氧化过程中碳烟碎裂的机制以及可能发生的条件。这项工作的新奇在于探索了两种情况下的现象：高和低煤烟倦怠。 此外，烟尘氧化还没有得到深入研究，粒子测量的最新进展可以增加现有的知识。 这些数据可用于修改氧化机制，当用于模拟时，将更准确地预测碳烟氧化时的结构、尺寸分布和平均性质。 此外，该项目将开始研究不同燃料成分在碎裂中的作用。 当工业界能够将这些基本原理应用于其系统以减少烟尘排放时，就会实现更广泛的影响，这对保护人类健康和更好地理解/减轻气候强迫非常重要。 另一方面，对于生产炭黑的行业来说，这些数据将增加现有的烟灰形成/氧化知识库。