Collaborative Research: Soot Formation in Time-Varying Nonpremixed Flames

陆地燃烧产生的烟尘颗粒现在被认为对健康构成重大威胁，并已成为美国环保署严格的新规定的对象。从发动机设计师的角度来看，对烟灰的关注超越了这些监管问题。燃烧室初级区烟灰浓度高，导致燃烧室衬板的热辐射负荷高。烟灰涂层在衬板表面急剧增加下垫金属的温度。由于烟尘的产生对压力非常敏感，新燃烧器运行时的高压使这些问题更加严重。如果煤烟和与之相关的问题要得到控制，对煤烟生长和氧化机制的定量了解是必不可少的。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。主要的物质浓度、小的自由基浓度、速度和温度是用一套基于激光的技术来测定的。主要的和痕量的碳氢化合物物种取样使用一种新型脉冲微探针耦合到质谱仪。他们还在进行新的光学诊断，以量化探针取样无法进入的区域中乙炔的浓度，并跟踪多环芳烃分子的生长和聚集。实验工作将辅以火焰结构的时间相关计算，包括分子生长化学。提出的工作将为分子生长化学和流体经历的时间-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获得实验数据，以严格测试相互竞争的烟尘生长模型，而且还指导我们对这一过程的直观理解的发展。在团队中，每个PI领导特定的项目领域：Marshall Long协调光学诊断活动，J. Houston Miller监督提取采样和视线光学诊断活动，Mitchell Smooke领导计算工作。数据“挖掘”和解释协同进行。提出的工作的一个重要组成部分是教育本科和研究生在化学和机械工程。这项工作的成果将用于他们社区的教育推广活动，包括(1)为期六周的科学前沿项目，旨在让高中三年级和四年级学生接触最前沿的科学研究；(2)耶鲁-纽黑文未来科学研究奖学金，支持纽黑文高中生与耶鲁大学研究生或博士后之间的暑期研究合作，由耶鲁大学教员指导。(3)皮埃蒙特环境与教育基金会（Piedmont environmental and Education Foundation），这是马里兰州新成立的非营利组织，旨在促进哥伦比亚特区和马里兰州郊区中小学的环境科学教育项目。

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.