Dynamics of premixed hydrogen/air flames in microchannels |
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Authors: | Gianmarco Pizza John Mantzaras Konstantinos Boulouchos |
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Affiliation: | a Paul Scherrer Institute, Combustion Research, CH-5232, Villigen PSI, Switzerland b Aerothermochemistry and Combustion Systems Laboratory, Swiss Federal Institute of Technology, CH-8092, Zurich, Switzerland c Department of Engineering and Management of Energy Resources, University of Western Macedonia, 50100 Kozani, Greece |
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Abstract: | The stabilization and dynamics of lean (φ=0.5) premixed hydrogen/air atmospheric-pressure flames in planar microchannels of prescribed wall temperature are investigated with respect to the inflow velocity and channel height (0.3 to 1.0 mm) using direct numerical simulation with detailed chemistry and transport. Rich dynamics starting from periodic ignition and extinction of the flame and further transitioning to symmetric V-shaped flames, asymmetric flames, oscillating and pulsating flames, and finally again to asymmetric flames are observed as the inlet velocity is increased. The richest behavior is observed for the 1.0-mm-height channel. For narrower channels, some of the dynamics are suppressed. The asymmetric flames, in particular, vanish for channel heights roughly less than twice the laminar flame thickness. Stability maps delineating the regions of the different flame types in the inlet velocity/channel height parameter space are constructed. |
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Keywords: | Premixed flame dynamics Microchannel Combustion instabilities Pitchfork bifurcation Hopf bifurcation Asymmetric flames Spectral element method |
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