UNS: GROWTH KINETICS AND MICROPHYSICAL PROPERTIES OF SOOT SUPERAGGREGATES

1511964（Chakrabarty）最近的研究表明，大规模明火释放出一种以前未被认识到的烟尘颗粒超聚集体（SAs），其数量和质量浓度超过70%。这些颗粒可能对人类健康和环境造成先前无法解释的影响。本研究的目的是在可控的情况下，模拟大规模露天燃烧产生的煤烟sa，并研究其颗粒形成机制和排放颗粒的性质。本科生和研究生将参与研究工作。PI还将在夏季为20名学校教师举办教师培训讲习班。传统观点认为，新排放烟尘微粒的终点形貌为迁移率直径（Dm）小于等于700 nm，气动直径（Da）小于等于300 nm，分形维数约为1.8。初步研究表明，其Dm和比表面积分别是常规烟尘颗粒的10倍和3倍。异常大的Dm值使得使用气溶胶迁移率测定仪器无法检测到烟尘sa。另外，用于估计肺内沉积概率的这些颗粒的Da与传统烟灰颗粒的Da相似。这些相互矛盾的烟尘SA特性的观察结果留下了几个基本的问题没有得到回答：火焰中的超聚集体生长动力学如何取决于工艺参数，如颗粒体积分数、停留时间、燃料的烟尘指数、燃料/空气流速和温度？聚集动力学在正重力（向上上升）火焰系统中有何不同？超聚集体颗粒的形态和性质对火焰过程参数的变化有多敏感？该项目旨在回答这些问题，这将带来对煤烟SA生长动力学及其微物理特性的潜在变革理解。

1511964(Chakrabarty)Recent studies have shown that large-scale open fires emit a previously unrecognized form of soot particle-superaggregates (SAs), in quantities greater than 70% by number and mass concentration. These particles could have previous unaccounted-for impacts on human health and the environment. The objective of this research is to generate, in a controlled manner, soot SAs that mimic those from large-scale open burns, and investigate the particle formation mechanism and the emitted particle properties. Undergraduate and graduate students will participate in the research effort. The PI will also conduct teachers training workshop for twenty school teachers over the summer.The conventional view holds that mobility diameter (Dm) less than or equal to 700 nm, aerodynamic diameter (Da) less than or equal to 300 nm, and fractal dimension approximately 1.8 is the end-point morphology of freshly-emitted soot particles. Preliminary investigations indicate that Dm and specific surface areas of soot SAs are ten and three times greater, respectively, than those of conventional soot particles. The unusually large Dm values render soot SAs undetectable using aerosol mobility sizing instruments. Alternatively, Da of these particles, which is used for estimating the probability of deposition within lungs, are similar to those of conventional soot particles. These contradicting observations of soot SA properties have left several fundamental questions unanswered: How does the superaggregate growth kinetics in a flame depend on the process parameters such as particle volume fraction, residence time, sooting index of the fuel, fuel/air flow rates, and temperature? How is the aggregation kinetics different in a positive gravity (upward rising) flame system? How sensitive are the superaggregate particle morphologies and properties to changes in the flame process parameters? This project proposes to answer these questions, which will bring about a potentially transformative understanding of soot SA's growth kinetics and their microphysical properties.