Primary and Secondary Aerosol Formation in Low-Temperature Combustion of Alcohol Biofuels

对环境清洁汽车的渴望导致了在发动机中使用生物衍生燃料的想法，以在较低的温度下运行。这样的系统将最大限度地减少导致光化学烟雾的废气排放。搭载低温内燃发动机的下一代乘用车有望在不久的将来大量出现。然而，与这些车辆有关的环境影响尚未得到全面评估。该研究项目结合了大气和燃烧科学的技术，以确定先进生物燃料低温燃烧排放的污染物对空气质量和气候的影响。这项研究的结果将为这些车辆在市场上部署之前设计有效的排放控制策略提供宝贵的价值。该项目将为本科生和高中暑期实习生提供通过研究进行教育的机会，研究团队将制定有关生物燃料、可再生能源和空气质量的课程计划，并将在高中STEM课程中实施。通过与雅典克拉克县少数民族和经济弱势学生入学率高的学校合作，这些教育项目将增加这些群体在STEM教育中的包容性。与传统柴油燃烧相比，低温燃烧减少了两种主要污染物的产生：氮氧化物（NOx）和黑碳。然而，目前尚不清楚低温燃烧，特别是当使用酒精生物燃料时，如何影响初级和次级有机气溶胶的形成——就其对空气质量和气候系统的影响而言，这两种污染物都是重要的污染物。这项研究将利用控制燃烧实验来阐明生物燃料的分子结构和导致气溶胶形成的气相反应之间的联系，这些反应在低温内燃机中遇到的温度、压力和等效比范围内。为了分离燃料结构对气溶胶形成和特性的影响，研究将涉及三种酒精生物燃料及其碳氢化合物类似物：1-丁醇和正丁烷、异戊醇和异戊烷、环戊醇和环戊烷。气溶胶排放的特性决定了它们对空气质量和气候的影响，包括化学成分以及微物理和光学特性。此外，排放物将通过模拟大气氧化的氧化流反应器发送，形成的二次有机气溶胶将被表征。同时，将对气体排放进行分类，以确定与初级有机气溶胶形成有关的中间体以及重要的次级有机气溶胶前体，这将阐明气相燃烧化学与气溶胶形成之间的联系。该奖项反映了美国国家科学基金会的法定使命，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。

A desire for environmentally cleaner automobiles has led to the idea of using biologically derived fuels in engines that operate at lower temperatures. Such systems would minimize exhaust emissions that contribute to photochemical smog. Next-generation passenger vehicles equipped with low-temperature combustion engines are expected to appear in larger numbers soon. However, the environmental impacts associated with these vehicles have not yet been completely assessed. This research project combines techniques from atmospheric and combustion sciences to determine the air-quality and climate impacts of pollutants emitted from the low-temperature combustion of advanced biofuels. Results from this research will be valuable for designing efficient emission-control strategies for these vehicles in advance of their deployment in the market. The project will afford education-through-research opportunities for undergraduates and high-school summer interns, and the research team will develop lesson plans on biofuels, renewable energy, and air quality to be implemented in high-school STEM curricula. By working with schools in Athens Clarke County that have high enrollments of minorities and economically disadvantaged students, these educational programs will increase the inclusion of such groups in STEM education.Low-temperature combustion reduces the production of two key pollutants compared to conventional diesel combustion: Nitrogen oxides (NOx) and black carbon. However, it is not clear how low-temperature combustion, especially when utilizing alcohol biofuels, affects the formation of primary and secondary organic aerosol – both important pollutants in terms of their effect on air quality and the climate system. This research will utilize controlled combustion experiments that will elucidate the connections between the molecular structure of biofuels and the gas-phase reactions leading to aerosol formation within the ranges of temperatures, pressures, and equivalence ratios encountered in low-temperature combustion engines. To isolate the effects of fuel structure on aerosol formation and properties, the investigation will involve three alcohol biofuels and their hydrocarbon analogues: 1-butanol and n-butane, iso-pentanol and iso-pentane, and cyclopentanol and cyclopentane. The aerosol emissions will be characterized for their properties that dictate their air-quality and climate impacts, including chemical composition as well as microphysical and optical properties. Furthermore, the emissions will be sent through an oxidation flow reactor that simulates atmospheric oxidation, and the secondary organic aerosol formed will be characterized. In parallel, the gaseous emissions will be speciated to identify intermediates implicated in primary organic aerosol formation as well as prominent secondary organic aerosol precursors, which will shed light on the connections between gas-phase combustion chemistry and aerosol formation.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.