This Georgia Tech project will improve the state-of-the-art understanding of turbulent flame propagation characteristics of high hydrogen content (HHC) fuels. The turbulent flame speed has a leading order influence on important combustor performance metrics such as flashback and blow-off propensities, emissions, life of hot section components, and combustion instabilities limits, including operating limits required to prevent harmful combustion dynamics. This research specifically addresses three of the combustion topic areas identified by Department of Energy (DOE) as of great importance for HHC systems: (1) turbulent burning velocities, (2) flash-back, and (3) exhaust gas recirculation (EGR) impacts. The results of this effort will also enable advances in several other combustion topic areas; e.g., predicting combustion dynamics (which requires flame shape predictions) and improving large eddy simulation capabilities by providing turbulent burning rate sub-models for HHC fuels.
The project involves both experimental and modeling efforts. Prior work used optical flame emission in measurement of global turbulent consumption speeds of hydrogen (H2)/carbon monoxide (CO) fuels. For this project, researchers will extend these previous efforts to a broader reactant class, including mixtures diluted with CO2, water (H2O), and nitrogen (N2). Depending upon the degree of dilution, these mixtures will simulate both gasified fuel blends and systems with EGR. This data will be used to further the development of physics-based, mixture-dependent models of turbulent burning rates and to guide selection of conditions for determining more localized measurements of turbulence/chemistry interactions. Specifically, high-repetition-rate particle image velocimetry and hydroxyl radical planar laser induced fluorescence systems will be used to determine local flame speeds under realistic turbulent conditions. This is necessary for developing an improved understanding of strained flame statistics, and for testing and refining propagation models based on leading point concepts. The work plan will initially focus on uniform, premixed reactant mixtures, and then expand in focus by investigating turbulent burning rates in inhomogeneous premixed flows. An example would be obtaining measurements of turbulent propagation speeds in mixtures with stratified fuel/air profiles.
This project will improve the understanding of turbulent flame propagation characteristics of high hydrogen content fuels. Improved knowledge of flame propagation enables predicting combustion dynamics and improved large eddy simulation capabilities which will lead to hydrogen combustor designs that produce less emissions at higher heating rates. Specifically, this project will gather data using optical flame emission for mixtures that simulate syngas fuels and systems using exhaust gas recirculation that will improve physics based models of turbulent burning rates.
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