Spatially Resolved Atomic Hydrogen Concentration Measurements in Sooting Hydrocarbon Flames Using Femtosecond Two-Photon LIF
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© 2017, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. Partial oxidation and soot formation in hydrocarbon flames is one of the major challenges during development of efficient and clean combustion systems such as internal combustion engines, gas turbine combustors and numerous industrial burners. Although numerous studies have been performed in order to characterize soot chemistry and develop viable soot models, fundamental atomic and molecular level understanding of reaction pathways and initiation mechanisms leading to soot chemistry remains largely unknown. One of the major difficulties in developing such fundamental understanding is the lack of experimental measurements of key reactive species such as H and O atoms in realistic combustion conditions. Although these atomic species play a critical role in chain-branching reactions, they exist in very small number densities—typically on the order of 10 15 cm -3 in atmospheric pressure flames—making quantitative experimental measurements very challenging. Hence the objective of this work is to apply the recently demonstrated, femtosecond-laser-based, twophoton laser-induced fluorescence (fs-TPLIF) technique to measure H-atom concentration in a series of sooting hydrocarbon flames. The fs-TPLIF scheme is employed to generate H-atom concentration plots in a range of ethylene flames stabilized over a Hencken calibration burner with the equivalence ratios ranging from very lean to very rich. In these cases, carbon monoxide (CO) concentration can be used as an indicator of the level of oxidation. These measurements are then compared with previous soot volume fraction measurements in similar flame conditions in order to identify a correlation between the H-atom concentration and soot formation.
author list (cited authors)
Jain, A., Wang, Y., & Kulatilaka, W. D.