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

碳质颗粒或烟尘的排放与燃烧装置有关，燃烧装置占全球总能源产量的80%以上。排放到大气中的烟尘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贡献者。该项目旨在解开烟尘形成的机制，即形成最小的烟尘核，然后成长为燃烧装置中大部分烟尘产生的原因。虽然最近燃烧技术的改进降低了烟尘水平，以符合当前的法规，但这种改进导致了更多更小的颗粒物的释放。因此，烟尘排放的负面影响仍然很大，因为纳米烟尘颗粒尺寸小，毒性高。很可能，对烟尘初生的基本了解不仅有利于当前的减排努力，也将有助于未来的法规，以限制最小和最有毒颗粒的数量。在实际环境中，烟尘始于扩散火焰中，这往往是最常见的烟尘条件占上风的配置。这项研究利用特意开发的气溶胶采样、调节和分析技术来测量火焰产生的小于2 nm和3000 Da的碳质材料的浓度、尺寸、电荷和组成，而不考虑它们的物理状态。这些技术将被用于研究最高温度可变的扩散火焰，这种火焰稳定在一种允许必要的空间分辨率的新型燃烧器结构中。该项目将导致建立一个基础设施，在明确定义和良好控制的条件下研究扩散火焰中的(碳)纳米颗粒和分子簇。更广泛地说，这一目标的实现将有助于理解气溶胶行为的基本原理，包括纳米粒子和分子簇的离子碰撞荷电。建议的方法提供的有关烟尘核结构和行为的详细信息将对改进现有烟尘模型的预测能力很有价值。该奖项反映了NSF的法定使命，并已通过使用基金会的智力优势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.