Grants and Contributions:

Grant or Award spanning more than one fiscal year. (2017-2018 to 2022-2023)

To achieve higher thermal efficiencies and smaller engine volumes, combustion engines are designed to operate at pressures much higher than the atmospheric. One of the major pollutants emitted from the gas turbines and diesel engines is soot, also known as particulate matter or black carbon, which forms during the combustion process when the mode of operation is non-premixed or partially-premixed, and its formation rate is significantly increased by increasing the combustion pressure. Soot aerosols affect the Earth's temperature and climate, both regionally and globally by altering the radiative properties of the atmosphere. The contribution to global warming may be substantial, perhaps second only to that of CO 2 . In addition, the deposition of soot on snow and ice reduces the surface reflectivity thus trapping the radiation; this could be responsible for a quarter of the global warming. As a result, the Intergovernmental Panel on Climate Change states that the soot aerosol is the third largest contributor to the positive radiative forcing that causes climate change. Furthermore, exposure to soot aerosol is responsible for hundreds of thousands of global deaths each year. A significant portion of soot is emitted from engines used in land, air and sea transportation. Controls on soot aerosol can produce rapid regional and global climate benefits as well as reductions of ill effects on human health. One of the approaches in control is prevention or reduction of soot generation in combustion. A fundamental understanding of the soot formation processes in combustion is an integral part of this control approach. However, the details of the chemical and physical mechanisms of the soot formation process in combustion remain uncertain due to the highly complex nature of hydrocarbon flames, and only a few principles are firmly established mostly for atmospheric conditions. In spite of the fact that most combustion devices used for transportation operate at very high pressures, our understanding of soot formation at high pressures is not at a desirable level, and there is a fundamental lack of experimental data and complementary predictive models. Sooting characteristics of liquid bio-fuels are not known well, especially at high pressures where most engines operate, and this lack of understanding has implications in adopting bio-fuels and blends in gas turbines and other land transportation engines. The current proposal aims to address these issues by contributing to the advancement of knowledge in soot formation and its characteristics at engine-relevant pressures and helping with the soot emissions control efforts. This will be accomplished by carefully planned experiments using the unique high-pressure combustion facility, and optical and intrusive combustion diagnostics at the University of Toronto Institute for Aerospace Studies.