The Role of HO2 and RO2 Radicals in Preignition Reaction Chemistry

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1335760CernanskyIn an effort to reduce emissions and fuel consumption, next generation ground transportation engines are expected to operate on cycles that employ Low Temperature Combustion (LTC). However, the underlying chemical kinetics and rate limiting steps in LTC have not been directly explored because of an inability to measure the key chemical constituents, hydroperoxy (HO2) and alkylperoxy (RO2) radicals, that control the process. In this study, a new laser absorption diagnostic combining two more traditional techniques will be employed to overcome this measurement problem and allow direct measurement of these peroxy radicals at preignition conditions, with the goal of developing a fundamental understanding of the underlying chemistry. The new diagnostic, cavity enhanced magneto-optical rotation (CEMOR), combines cavity enhanced ringdown spectroscopy which provides the sensitivity to measure the radicals and magneto-optic rotation which provides the selectivity necessary to eliminate interference from other compounds with similar absorption characteristics. This work will aid in the design of the next generation engine systems with increased efficiency and reduced emissions. The broader impact of the work will include training students in combustion science and state-of-the-art optical diagnostics techniques. The data collected in this effort will provide necessary information to further understand combustion chemistry, its role in the generation of greenhouse gases, and the subsequent effect on climate change. Efforts will be made to enhance minority student recruitment and participation in research and graduate education. Outreach activities include NSF's RET and REU site programs.