TY - GEN
T1 - Proper orthogonal decomposition for flame dynamics of microwave plasma assisted swirl stabilized premixed flames
AU - Rajasegar, Rajavasanth
AU - Mitsingas, Constandinos M.
AU - Mayhew, Eric K.
AU - Yoo, Jihyung
AU - Lee, Tonghun
N1 - Funding Information:
Authors were supported by the U.S. Air Force Office of Scientific Research (AFOSR, FA9550-14-1-0343) with Dr. Chiping Li as the Technical Monitor for the development and algorithms and by AFRL (AFRL, FA 8650-15-C-2547) for development of the plasma enhanced combustion system.
Publisher Copyright:
© 2017 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.
PY - 2017
Y1 - 2017
N2 - The primary aim of this work is to establish the effectiveness of microwave plasma discharges to improve combustor flame dynamics and stability through minimizing heat release fluctuations. A continuous, volumetric, direct coupled, non-equilibrium, atmospheric microwave plasma discharge was applied to a swirl stabilized premixed methane-air flame to minimize combustion instabilities. Proper Orthogonal Decomposition (POD) is used to post-process data and extract information on flame dynamics that are usually lost through classical statistical approaches. POD analysis carried out on OH planar laser-induced fluorescence (PLIF) images reveal that even at coupled plasma powers corresponding to less than 5% of the thermal power output, significant improvement in mean energy content of flames (~23%) was observed. The corresponding decrease in heat release fluctuations resulted in improved combustor flame dynamics and flame stability, which was found to be in good agreement with acoustic pressure measurements. In the presence of plasma discharge, an effective decoupling between the flame oscillations and the fluid unsteadiness was established due to the differences in flame stabilization mechanisms resulting in up to 47% reduction in RMS pressure fluctuations. Thus, effective fluid-acoustic decoupling in addition to the accelerated combustion chemistry due to the non-thermal effects of plasma led to significantly improved combustor dynamics namely, decreased heat release and pressure fluctuations.
AB - The primary aim of this work is to establish the effectiveness of microwave plasma discharges to improve combustor flame dynamics and stability through minimizing heat release fluctuations. A continuous, volumetric, direct coupled, non-equilibrium, atmospheric microwave plasma discharge was applied to a swirl stabilized premixed methane-air flame to minimize combustion instabilities. Proper Orthogonal Decomposition (POD) is used to post-process data and extract information on flame dynamics that are usually lost through classical statistical approaches. POD analysis carried out on OH planar laser-induced fluorescence (PLIF) images reveal that even at coupled plasma powers corresponding to less than 5% of the thermal power output, significant improvement in mean energy content of flames (~23%) was observed. The corresponding decrease in heat release fluctuations resulted in improved combustor flame dynamics and flame stability, which was found to be in good agreement with acoustic pressure measurements. In the presence of plasma discharge, an effective decoupling between the flame oscillations and the fluid unsteadiness was established due to the differences in flame stabilization mechanisms resulting in up to 47% reduction in RMS pressure fluctuations. Thus, effective fluid-acoustic decoupling in addition to the accelerated combustion chemistry due to the non-thermal effects of plasma led to significantly improved combustor dynamics namely, decreased heat release and pressure fluctuations.
KW - Combustion instability
KW - Direct coupling
KW - Eigenmodes
KW - Flame dynamics
KW - Method of snapshots
KW - Non-equilibrium effects
KW - OH-PLIF
KW - Plasma assisted combustion
KW - Pressure fluctuations
KW - Proper orthogonal decomposition
KW - Swirl stabilization
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U2 - 10.2514/6.2017-1973
DO - 10.2514/6.2017-1973
M3 - Conference contribution
AN - SCOPUS:85017198343
T3 - AIAA SciTech Forum - 55th AIAA Aerospace Sciences Meeting
BT - AIAA SciTech Forum - 55th AIAA Aerospace Sciences Meeting
PB - American Institute of Aeronautics and Astronautics Inc.
T2 - 55th AIAA Aerospace Sciences Meeting
Y2 - 9 January 2017 through 13 January 2017
ER -