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的形成和氧化很重要，因为烟灰的健康影响，在气候强迫中的作用以及对环境空气质量和可见性的重要性。 众多研究人员已经报道了烟灰对烟灰的不利影响。 烟灰与气候强迫有关；但是，其实际贡献仍然不确定。空气污染控制设备的制造商，即柴油颗粒过滤器，也有兴趣了解较低温度下的烟灰氧化的速率和机制。预防的工作已经确定了在各种燃烧条件下烟灰的分裂，包括高烟灰耗尽（包括高碳酸盐）（70％碳燃烧）和低耗散的燃烧量，燃烧到燃烧的环境（约10％碳燃烧的碳水化量），均为10％碳燃烧（均为10％碳）。 此外，最近的建模已经确定了碎片化在预测粒径分布和其他烟灰特性中的重要性。 但是，几乎没有实验数据，无法充分理解碎裂可能发生的条件和机制。 其他人则建议氧扩散到颗粒中，从而可以内部燃烧，从而分解烟灰团聚。 拟议的工作具有以下三个目标：目标1。确定条件，即温度，等效比，自由基池等。在低倦怠和高倦怠时发生乙烯火焰发生碎片，目的2。确定碎片的机制，例如在铜和sot颗粒破裂中的氧气扩散; 目标3。对替代液体燃料进行测试，以确定目标2中对这些燃料的机制的适用性以及芳香族与脂肪族组件的作用。该实验将在可用于二级燃烧器系统中进行，该实验可用于同时和液体燃料。 在该系统中，第一个燃烧器会产生烟灰，而第二个燃烧器则用于在各种温度和等效比率下氧化烟灰。尺寸范围为3-100 nm的扫描迁移率粒子sizer（SMP）将用于确定粒度分布，这是燃烧器高度的函数。在需要时，长距离迁移率分析仪的测量可以将范围扩展到660 nm。 将采用关键成分的气相浓度（即O2，H2，CO，CO2）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和粒度分布数据，我们将在目标2中探索颗粒之间的“桥”材料通过氧扩散的氧化，并增加颗粒孔隙率的增加，从而导致粒子碎片化。 该研究的智力优点在于了解氧化过程中烟灰破碎的机制以及可能发生的条件。这项工作的新颖性是在两种情况下探索现象：高和低烟灰倦怠。 此外，尚未深入研究烟灰氧化，粒子测量的最新进展可以增加现有知识。 数据可用于修饰氧化机制，当在模拟中使用时，该机制将更准确地预测烟灰的结构，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破碎化中的作用。 当行业可以将这些基本原理应用于其系统以减少烟灰排放，对于保护人类健康和更好地理解/减轻气候强迫的重要性时，就会实现更广泛的影响。 另一方面，对于生产碳黑色的行业，这些数据将增加烟灰形成/氧化的现有知识库。