CAREER: Progression from soot to nanocrystalline carbon in elevated temperature flames

烟尘的形成仍然是影响燃烧性能、公众健康和环境的一个关键因素。由于煤油燃料火箭、氧燃料燃烧系统和其他新兴燃烧过程的突出，越来越需要表征极热火焰中烟灰的形成。科学的目标是阐明火焰中烟灰的形成比传统的研究更热。一个互补的实验和计算建模方法将被用来隔离的基本现象，独特的烟尘形成制度。即将到来的空间货运和旅游企业需要烟灰模型用于火箭推进器设计和颗粒排放预测。纳米晶碳在由煤油和其他碳氢化合物推进剂驱动的火箭飞行过程中形成。更全面地考虑性能和未知的环境影响（即公共健康、气候等）通过研究在高温下的烟灰形成来促进。高温富氧燃烧、预热空气系统和富氧空气处理也是比常规燃烧更热的新兴燃烧技术的例子。在社会影响方面，通过与麦克奈尔计划和布里奇斯社区学院计划的合作，将加强对研究生院和学术生涯更具包容性的参与的迫切需要。还将开发热流体理论和应用的虚拟教学模块，以增加当地高中学生的参与。富燃料火焰化学模型导致气相碳烟前体变化很大，为传统的燃烧温度和高温火焰的研究存在。这同样适用于底层的气溶胶动力学和烟尘纳米结构的演变。中心假设是，量化的可逆烟灰前体反应，减少碰撞效率，极端的颗粒石墨化，也许，电离过程需要准确地捕捉烟灰行为在高温下。在拟议活动结束时，PI将：（一）系统地测量在表征良好的层流和湍流实验室火焰中的单个PAH分布和烟尘颗粒尺寸分布;（二）表征高温火焰中形成的颗粒的碳纳米结构和形态的演变;（三）评估电离过程对该区域烟尘形成的作用;（iv）将新的实验观察结果纳入高温烟灰形成的新模型;（v）展示了从烟灰到新发现的纳米碳结构转变的独特高温过程。该项目的重要性在于，综合性实验和建模方法将促进烟尘形成理论的自洽发展，从而使常规和高温区域受益。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Soot formation remains a crucial factor in combustion performance, public health and the environment. There is a rising need to characterize soot formation in extremely hot flames due to prominence of kerosene-fueled rockets, oxy-fuel combustion systems and other emerging combustion processes. The scientific objective is to shed light on soot formation in flames hotter than traditionally studied. A complementary experimental and computational modeling approach will be used to isolate fundamental phenomena unique to this soot formation regime. Imminent space cargo and tourism enterprises require soot models for rocket thruster design and particulate emissions predictions. Nanocrystalline carbon forms during rocket flight powered by kerosene and other hydrocarbon propellants. A more thorough consideration of performance and unknown environmental impacts (i.e. public health, climate, etc.) is facilitated by studying soot formation at elevated temperature. High temperature oxyfuel combustion, preheated air systems and enriched air processing are also examples of emerging combustion technologies operating hotter than conventional combustion. In terms of societal impact, the urgent need for more inclusive participation in graduate school and academic careers will be enhanced through collaboration with the McNair program and Bridges Community College program. Virtual teaching modules for thermofluids theory and applications will also be developed to increase participation of local high-school students.Quantification of competing soot formation processes remains a challenge. Fuel-rich flame chemistry models leading to gas-phase soot precursors vary widely for conventional combustion temperatures and no studies for elevated temperature flames exist. The same can be said for the underlying aerosol dynamics and evolution in soot nanostructure. The central hypothesis is that quantification of reversible soot precursor reactions, reduction in collision efficiency, extreme particle graphitization and, perhaps, ionization processes are required to accurately capture soot behavior at elevated temperatures. At the conclusion of the proposed activities the PI will have: (i) systematically measured individual PAH profiles and soot particle size distributions in well-characterized laminar and turbulent laboratory flames; (ii) characterized evolution in carbon nanostructure and morphology for particles formed in elevated temperature flames; (iii) assessed the role of ionization processes on soot formation in this regime; (iv) incorporated new experimental observations into new models for higher temperature soot formation; (v) demonstrated unique higher-temperature processes governing the transition from soot to newly discovered nanocrystalline carbon structure. The proposed project is significant because self-consistent development of soot formation theory will be facilitated by the comprehensive experimental and modeling approach for the benefit of conventional and higher-temperature regimes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.