TY - GEN
T1 - Impact of flow non-axisymmetry on swirling flow dynamics and receptivity to acoustics
AU - Hansford, Samuel
AU - O'connor, Jacqueline
AU - Manoharan, Kiran
AU - Hemchandra, Santosh
N1 - Publisher Copyright:
Copyright © 2015 by ASME.
PY - 2015
Y1 - 2015
N2 - In this study, we experimentally investigate both the intrinsic instability characteristics and forced response to transverse acoustic excitation of a non-reacting, swirling flow for application to combustion instability in annular gas turbine engines. The non-axisymmetry of the velocity field is quantified using an azimuthal mode decomposition of the time-averaged velocity field that shows that(1) the flow field is largely axisymmetric,(2) axisymmetry decreases with downstream distance, and (3) forcing does not significantly alter the time averaged shape of the flow field. The flow field is analyzed in a companion linear stability analysis that shows that the most unstable modes in the flow field are m=-1 and m=-2, which agrees with the experimental observations and shows that the intrinsic dynamics of this flow field are non-axisymmetric with respect to the jet axis. The linear stability analysis captures the spatial variation of mode strength for certain modes, particularly mode m=-1, but there are some deviations from the experimental results. Most notably, these deviations occur for mode m=0 at radii away from the jet axis. Experimental results of the forced response of the flow indicate that the intrinsic instability characteristics of the flow field have an impact on the forced-response dynamics. Response of the flow field to a velocity anti-node in a standing transverse acoustic field shows non-axisymmetric vortex rollup and the dominance of the m=-1 and m=1 azimuthal modes in the fluctuating flow field. In the presence of a pressure anti-node, the m=0 mode of the fluctuating flow field is very strong at the jet exit, indicating an axisymmetric response, and ring vortex shedding is apparent in the flow measurements from high-speed PIV. However, further downstream, the strength of the axisymmetric mode decreases and the m=-1 and m=1 modes dominate, resulting in a tilting of the vortex ring as it convects downstream. Implications for flame response to transverse acoustic fields are discussed.
AB - In this study, we experimentally investigate both the intrinsic instability characteristics and forced response to transverse acoustic excitation of a non-reacting, swirling flow for application to combustion instability in annular gas turbine engines. The non-axisymmetry of the velocity field is quantified using an azimuthal mode decomposition of the time-averaged velocity field that shows that(1) the flow field is largely axisymmetric,(2) axisymmetry decreases with downstream distance, and (3) forcing does not significantly alter the time averaged shape of the flow field. The flow field is analyzed in a companion linear stability analysis that shows that the most unstable modes in the flow field are m=-1 and m=-2, which agrees with the experimental observations and shows that the intrinsic dynamics of this flow field are non-axisymmetric with respect to the jet axis. The linear stability analysis captures the spatial variation of mode strength for certain modes, particularly mode m=-1, but there are some deviations from the experimental results. Most notably, these deviations occur for mode m=0 at radii away from the jet axis. Experimental results of the forced response of the flow indicate that the intrinsic instability characteristics of the flow field have an impact on the forced-response dynamics. Response of the flow field to a velocity anti-node in a standing transverse acoustic field shows non-axisymmetric vortex rollup and the dominance of the m=-1 and m=1 azimuthal modes in the fluctuating flow field. In the presence of a pressure anti-node, the m=0 mode of the fluctuating flow field is very strong at the jet exit, indicating an axisymmetric response, and ring vortex shedding is apparent in the flow measurements from high-speed PIV. However, further downstream, the strength of the axisymmetric mode decreases and the m=-1 and m=1 modes dominate, resulting in a tilting of the vortex ring as it convects downstream. Implications for flame response to transverse acoustic fields are discussed.
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U2 - 10.1115/GT201543377
DO - 10.1115/GT201543377
M3 - Conference contribution
AN - SCOPUS:84954348524
T3 - Proceedings of the ASME Turbo Expo
BT - Combustion, Fuels and Emissions
PB - American Society of Mechanical Engineers (ASME)
T2 - ASME Turbo Expo 2015: Turbine Technical Conference and Exposition, GT 2015
Y2 - 15 June 2015 through 19 June 2015
ER -