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

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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.