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.

1133480Lighty烟灰的形成和氧化非常重要，因为烟灰对健康有不利影响、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告了烟灰对健康的不利影响。 烟尘与气候强迫有关；然而，其实际贡献仍然有些不确定。空气污染控制设备（即柴油颗粒过滤器）的制造商也有兴趣了解较低温度下烟灰氧化的速率和机制。之前的工作已经确定了在各种燃烧条件下烟灰颗粒的破碎，包括高烟灰燃尽率（70％碳）烧尽）且燃尽率低，在高温、火焰环境下接近燃烧器（约10%碳烧尽）。 此外，最近的模型已经确定了碎片在预测颗粒尺寸分布和其他烟灰特性中的重要性。 然而，很少有实验数据可以充分了解碎片可能发生的条件及其机制。 其他人则认为氧气扩散到颗粒中，从而实现内部燃烧，从而分解烟灰团聚体。 拟开展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. 确定碎裂的机制，例如桥梁破坏时的氧气扩散和烟灰颗粒分解； 目标 3. 对替代液体燃料进行测试，以确定目标 2 中确定的机制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。实验将在可使用的两级预混燃烧器系统中进行适用于气体和液体燃料。 在该系统中，第一个燃烧器产生烟灰，而第二个燃烧器用于在各种温度和当量比下氧化烟灰。粒度范围为 3-100 nm 的扫描迁移率粒度仪 (SMPS) 将用于确定作为燃烧器上方高度函数的粒度分布。当需要时，长差分迁移率分析仪测量可以将范围扩展到 660 nm。 将获取关键成分（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 中探索通过氧扩散对颗粒之间的“桥”材料进行氧化，以及颗粒孔隙率的增加，从而导致颗粒破碎。 这项研究的智力价值在于了解氧化过程中烟灰碎裂的机制以及可能发生这种情况的条件。这项工作的新颖之处在于探索了两种情况下的现象：高烟灰燃尽率和低烟灰燃尽率。 此外，烟灰氧化尚未得到深入研究，颗粒测量的最新进展可以丰富现有知识。 这些数据可用于修改氧化机制，当用于模拟时，将更准确地预测烟灰氧化时的结构、尺寸分布和平均特性。 此外，该项目将开始解决不同燃料成分在碎片化中的作用。 当工业界能够将这些基本原理应用到其系统中以减少烟尘排放时，就会实现更广泛的影响，这对于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，这些数据将添加到现有的烟灰形成/氧化知识库中。