Collaborative Research: Soot Formation in Time-Varying Non-Premixed Flames

CBET-0828802Smooke燃烧产生的陆源烟尘颗粒现在被认为构成了重大的健康风险，并已成为严格的EPA新法规的主题。从发动机设计者的角度来看，对烟尘的担忧超出了这些监管问题的范畴。燃烧室主要区域的高烟尘浓度导致燃烧室衬里的高热辐射负荷。衬里表面的烟尘涂层极大地提高了底层金属温度。新燃烧器运行时的高压加剧了这些问题，因为烟尘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至关重要的。在这个合作研究奖中，耶鲁大学和乔治华盛顿大学的研究小组正在研究强迫、时变火焰中的分子生长化学。使用一套基于激光的技术来确定主要组分浓度、小分子自由基浓度、速度和温度。使用与质谱仪连接的新型脉冲微探头对主要和微量碳氢化合物进行采样。他们还在进行新的光学诊断，以量化探测采样无法到达的区域的乙炔浓度，并跟踪多环芳烃分子的生长和聚集。实验工作将得到包括分子生长化学在内的火焰结构的时间相关计算的补充。拟议的工作将为分子生长化学和一包流体经历的时间-温度历史之间的微妙相互作用提供关键的见解。这项工作的目标不仅是为严格测试竞争烟尘增长模型获得实验数据，而且还为了指导我们对这一过程的直观理解。在团队内部，每个PI领导特定的项目领域：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·斯穆克领导计算工作。数据挖掘和解释是协同进行的。拟议工作的一个重要组成部分是对本科生和研究生进行化学和机械工程方面的教育。这项工作的成果将用于社区的教育推广活动，包括(1)为期六周的科学前沿计划，旨在让高三和高年级学生接触尖端科学研究；(2)耶鲁-纽黑文未来科学研究奖学金，支持纽黑文高中生和耶鲁大学研究生或博士后在耶鲁教职员工的指导下进行暑期研究合作；(3)皮德蒙特环境和教育基金会，一个新注册的非营利性组织，在马里兰州成立，旨在促进哥伦比亚特区和马里兰州郊区中学的环境科学教育计划。

CBET-0828802SmookeCombustion-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.