Collaborative Research: Soot Formation in Time-Varying Nonpremixed Flames

CBET-0828950米勒燃烧产生的烟尘颗粒从陆基来源，现在被公认为构成重大的健康风险，并已成为严格的新的环保署法规的主题。从发动机设计者的角度来看，对烟灰的关注超出了这些监管问题。燃烧室主燃区中的高烟灰浓度导致燃烧室衬套上的高热辐射负荷。缸套表面的烟灰涂层会大大增加底层金属的温度。这些问题由于新燃烧器运行时的高压而加剧，因为烟灰的产生对压力非常敏感。如果要控制烟尘和与之相关的问题，对烟尘生长和氧化机制的定量了解是必不可少的。在这项合作研究奖中，耶鲁大学和乔治华盛顿大学的研究小组正在研究强制的、随时间变化的火焰中的分子生长化学。主要物种的浓度，小自由基的浓度，速度和温度确定使用一套基于激光的技术。主要和痕量烃类物种的采样使用一种新的脉冲微探针耦合到质谱仪。他们还在进行新的光学诊断，以量化探针采样无法到达的区域中的乙炔浓度，并跟踪PAH分子的生长和聚集。实验工作将得到补充的火焰结构，包括分子生长化学随时间变化的计算。拟议中的工作将提供关键的洞察到微妙的相互作用之间的分子生长化学和时间-温度的历史所经历的一包流体。这项工作的目标不仅是获得实验数据，对竞争性碳烟增长模型进行严格的测试，而且还指导我们对该过程的直观理解。在团队中，每个PI负责特定的项目领域：马歇尔龙协调光学诊断活动，J.休斯顿米勒监督提取采样和视线光学诊断活动，米切尔斯莫克领导计算工作。数据“挖掘”和解释合作进行。一个重要组成部分的拟议工作是本科生和研究生的教育在化学和机械工程。这项工作的结果将投入到他们社区的教育推广活动中，包括（1）为期六周的科学前沿项目，旨在使高中三年级和四年级学生接触前沿科学研究，（2）耶鲁-纽黑文未来科学研究奖学金，它支持纽黑文高中学生和耶鲁大学研究生或博士后之间的夏季研究合作，由耶鲁大学教职员工监督，以及（3）皮埃蒙特环境和教育基金会，一个新成立的非营利组织，在马里兰州注册成立，旨在促进哥伦比亚特区和马里兰州郊区的中学和中学的环境科学教育计划。

CBET-0828950MillerCombustion-generated soot particulates from land-based sources are now acknowledged to pose a significant health risk and have been the subject of stringent new EPA regulations. From the engine designer's standpoint, the concern about soot goes beyond these regulatory issues. High soot concentrations in combustor primary zones contribute to high thermal radiation loads on combustor liners. Soot coatings on liner surfaces drastically increase underlying metal temperatures. These issues are exacerbated by the high pressures at which new combustors are operated, because soot production is very sensitive to pressure. If soot and the problems associated with it are to be controlled, quantitative understanding of the soot growth and oxidation mechanisms is essential.In this collaborative research award, groups at Yale and George Washington University are studying molecular-growth chemistry in forced, time-varying flames. Major species concentrations, small radical concentrations, velocity, and temperature are determined using a suite of laser-based techniques. Both major and trace hydrocarbon species are sampled using a novel pulsed microprobe coupled to a mass spectrometer. They are also performing new optical diagnostics to quantify the concentration of acetylene in regions inaccessible to probe sampling and to follow PAH molecular growth and aggregation. The experimental work will be complemented by time-dependent computations of flame structure that include molecular growth chemistry. The proposed work will provide critical insight into the subtle interplay between molecular growth chemistry and the time-temperature history experienced by a packet of fluid. The goal of the work is not only to obtain experimental data for a rigorous test of competing soot growth models, but also to guide the development of our intuitive understanding of the process. Within the team, each PI leads specific project areas: Marshall Long coordinates the optical diagnostics activities, J. Houston Miller supervises the extractive sampling and line-of-sight optical diagnostic activities, and Mitchell Smooke leads the computational efforts. Data "mining" and interpretation proceed collaboratively.An essential component of the proposed work is education of undergraduate and graduate students in chemistry and mechanical engineering. Results of this work will feed into educational outreach activities in their communities, including (1) the six-week Frontiers of Science program, designed to expose high school juniors and seniors to leading-edge scientific research, (2) the Yale-New Haven Futures in Science Research Fellowship, which supports a summer research collaboration between a New Haven high school student and a Yale graduate student or post-doc supervised by a Yale faculty member, and (3) the Piedmont Environment and Education Foundation, a newly-chartered nonprofit incorporated in the State of Maryland, established to promote environmental science educational programs for middle and secondary schools in the District of Columbia and suburban Maryland.