EAGER/CEMOR: A New Diagnostic for Quantitative Measurement of HO2 and RO2

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1142312 CernanskyImplementing new engine designs that operate utilizing Low Temperature Combustion (LTC) has been identified as key to lowering emissions, enhancing efficiency and thereby reducing the dependency of the United States on foreign sources of fuel. Unfortunately, the chemistry models describing LTC are inadequate to proceed with these designs and, while the best theories suggest that LTC is controlled by hydroperoxy radical (HO2) and alkylperoxy radical (RO2), these species are not readily measured in engines and other combustion systems by existing methodologies. Quantitative measurement of these radicals and development of LTC chemistry models will significantly shorten the time to implement the benefits of LTC. This program is focused on demonstrating that cavity enhanced magneto-optical rotation (CEMOR), a highly sensitive and selective laser diagnostic technique developed at Drexel University, can be applied for in situ measurement of HO2 and RO2 in reaction systems. CEMOR combines the sensitivity of cavity ringdown spectroscopy (CRDS) with the selectivity of magneto optic rotation (MOR) to provide selective detection of weakly absorbing species in complex reacting environments. We have shown in our laboratory that CEMOR allows selective observation of paramagnetic species, simplifying detection in otherwise complicated mixtures, and we also have made the first measurements of a radical, OH, in a lean premixed methane/air flame using MOR and CEMOR. These results demonstrate the effectiveness of measuring combustion generated radicals using the MOR and CEMOR techniques, and illustrates the increase in sensitivity CEMOR exhibits over MOR. The next step is to measure HO2 in the controlled environment of a photolysis cell using both CRDS and CEMOR in order to generate high resolution absorption cross section data and to calibrate the CEMOR technique for the subsequent demonstration of quantitative measurements in a combustion environment. Intellectual Merit Application of CEMOR for in situ measurements of HO2 and RO2 radicals will provide new insight into the reaction dynamics of low and intermediate temperature combustion systems. This will aid in the design of the next generation engine systems that use this reaction regime to achieve increased efficiency and reduced emissions. This new measurement capability also will be useful in other areas (e.g., atmospheric chemistry) where highly sensitive and selective peroxy radical measurements are desired. Broader Impact The societal impact of transitioning to engine designs employing low temperature combustion technologies could be enormous, and this research will provide an important tool to help enable such a transition. As such, the research is both appropriate and needed. The educational impact of the research will be through providing an opportunity to train students in optical diagnostics and combustion science, giving them the required skills to contribute to the combustion/energy community. One graduate research assistant will be supported by this project, and one or two undergraduate students are expected to participate in this project as part of our Honors Research Program experience. Special attention will be given to attracting underrepresented minority and female students building on successful programs existing at Drexel University. The results of the research will be presented as professional presentations, archival publications, website entries, and theses/dissertations, providing other researchers and the public with the information needed to understand newly important combustion processes.