TY - GEN
T1 - Flame leading edge and flow dynamics in a swirling, lifted flame
AU - Malanoski, Michael
AU - Aguilar, Michael
AU - O'Connor, Jacqueline
AU - Shin, Dong Hyuk
AU - Noble, Bobby
AU - Lieuwen, Tim
PY - 2012
Y1 - 2012
N2 - Flames in high swirl flow fields with vortex breakdown often stabilize aerodynamically in front of interior flow stagnation points. In contrast to shear layer stabilized flames with a nearly fixed, well defined flame attachment point, the leading edge of aerodynamically stabilized flames can move around substantially, due to both the inherent dynamics of the vortex breakdown region, as well as externally imposed oscillations. Motion of this flame stabilization point relative to the flow field has an important dynamical role during combustion instabilities, as it creates flame front wrinkles and heat release fluctuations. For example, a prior study has shown that nonlinear dynamics of the flame response at high forcing amplitudes were related to these leading edge dynamics. This heat release mechanism exists alongside other flame wrinkling processes, arising from such processes as shear layer rollup and swirl fluctuations. This paper describes an experimental investigation of acoustic forcing effects on the dynamics of leading edge of a swirl stabilized flame. Vortex breakdown bubble dynamics were characterized using both high-speed particle image velocimetry (PIV) and line-of-sight high-speed CH* chemiluminescence. A wide array of forcing conditions was achieved by varying forcing frequency, amplitude, and acoustic field symmetry. These results show significant differences in instantaneous and time averaged location of the flow stagnation points. They also show motion of the flame leading edge that are of the same order of magnitude as corresponding particle displacement associated with the fluctuating velocity field. This observation suggests that heat release fluctuations associated with leading edge motion may be just as significant in controlling the unsteady flame response as the flame wrinkles excited by velocity fluctuations.
AB - Flames in high swirl flow fields with vortex breakdown often stabilize aerodynamically in front of interior flow stagnation points. In contrast to shear layer stabilized flames with a nearly fixed, well defined flame attachment point, the leading edge of aerodynamically stabilized flames can move around substantially, due to both the inherent dynamics of the vortex breakdown region, as well as externally imposed oscillations. Motion of this flame stabilization point relative to the flow field has an important dynamical role during combustion instabilities, as it creates flame front wrinkles and heat release fluctuations. For example, a prior study has shown that nonlinear dynamics of the flame response at high forcing amplitudes were related to these leading edge dynamics. This heat release mechanism exists alongside other flame wrinkling processes, arising from such processes as shear layer rollup and swirl fluctuations. This paper describes an experimental investigation of acoustic forcing effects on the dynamics of leading edge of a swirl stabilized flame. Vortex breakdown bubble dynamics were characterized using both high-speed particle image velocimetry (PIV) and line-of-sight high-speed CH* chemiluminescence. A wide array of forcing conditions was achieved by varying forcing frequency, amplitude, and acoustic field symmetry. These results show significant differences in instantaneous and time averaged location of the flow stagnation points. They also show motion of the flame leading edge that are of the same order of magnitude as corresponding particle displacement associated with the fluctuating velocity field. This observation suggests that heat release fluctuations associated with leading edge motion may be just as significant in controlling the unsteady flame response as the flame wrinkles excited by velocity fluctuations.
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U2 - 10.1115/GT2012-68256
DO - 10.1115/GT2012-68256
M3 - Conference contribution
AN - SCOPUS:84880204269
SN - 9780791844687
T3 - Proceedings of the ASME Turbo Expo
SP - 199
EP - 209
BT - ASME Turbo Expo 2012
T2 - ASME Turbo Expo 2012: Turbine Technical Conference and Exposition, GT 2012
Y2 - 11 June 2012 through 15 June 2012
ER -