Unraveling Soot Inception in Diffusion Flames with State-of-the-Art Sampling, Conditioning and Analysis Techniques

碳质颗粒或煤烟的排放与燃烧装置有关，燃烧装置占全球总能源生产的80%以上。排放到大气中的煤烟颗粒对人类健康有害，被认为是气候变化中辐射强迫的第二大因素。该项目旨在揭示烟灰开始的机制，即最小烟灰核的形成，随后在燃烧装置中成长为负责大部分总体烟灰生产。虽然最近燃烧技术的改进降低了煤烟水平以符合现行法规，但这种改进导致了越来越多的小颗粒的释放。因此，由于纳米级烟尘颗粒的小尺寸和高毒性，烟尘排放的负面影响仍然很大。很可能，对烟灰起源的基本理解不仅有利于当前的减排努力，而且有利于未来的法规，以限制最小和最有毒颗粒的数量排放。在实际设置中，煤烟在扩散火焰中开始，这往往是最常见的配置，其中煤烟条件占上风。该研究利用专门开发的气溶胶采样、调理和分析技术，测量小于2 nm和3000 Da的火焰生成的碳质材料的浓度、大小、电荷和组成，而不管它们的物理状态如何。该技术将适用于在一种允许必要空间分辨率的新型燃烧器配置中稳定的可变最高温度的扩散火焰的研究。该项目将建立一个基础设施，在明确和良好控制的条件下研究扩散火焰中的（碳）纳米颗粒和分子团簇。更广泛地说，这一目标的实现将有利于理解气溶胶行为的基本原理，包括纳米粒子和分子团簇的离子碰撞充电。所提出的方法所提供的有关烟尘核结构和行为的详细信息将有助于提高现有烟尘模型的预测能力。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。

Emissions of carbonaceous particles, or soot, are associated with combustion devices that are responsible for more than 80% of the total energy production worldwide. Soot particles released to the atmosphere are harmful to human health and are considered the second largest contributor to radiative forcing in climate change. This project aims at unraveling the mechanisms of soot inception, that is the formation of the smallest soot nuclei that subsequently grow to be responsible for the bulk of the overall soot production in combustion devices. While recent improvements in combustion technologies have reduced soot levels to match current regulations, such improvements have resulted in the release of a larger number of ever smaller particles. As a result, the negative impact of soot emissions remains substantial because small sizes and high toxicity of nano-sized soot particles. It is likely that a fundamental understanding of soot inception will not only be beneficial for current abatement efforts but also for future regulations to limit emissions in terms of number of the smallest and most toxic particles.In practical settings, soot inception in diffusion flames that tend to be the most common configuration in which sooting conditions prevail. The proposed research takes advantage of purposely developed aerosol sampling, conditioning and analysis techniques to measure concentration, size, charge, and composition of flame generated carbonaceous materials smaller than 2 nm and 3000 Da, regardless of their physical state. The techniques will be adapted to the investigation of diffusion flames of variable maximum temperature stabilized in a novel burner configuration that allows for the necessary spatial resolution. The project will result in the establishment of an infrastructure to study (carbon) nanoparticles and molecular clusters in diffusion flames under well-defined and well-controlled conditions. More broadly, the achievement of this goal will benefit the understanding of the fundamentals of aerosol behavior, including ion collision charging of nanoparticles and molecular clusters. The details about the structure and behavior of soot nuclei provided with the proposed methods will be valuable to improve the predictive capabilities of existing soot models.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.