Session: 04-22: Combustion Dynamics - Experiments I
Paper Number: 79706
79706 - Effect of Counter- and Co-Swirl on Low-Frequency Combustion Instabilities of Jet A-1 Spray Flames
The present experimental study investigates the influence of pilot swirling directions on low-frequency combustion instabilities of Jet A-1 pilot diffusion flames in a laboratory-scale combustor at atmospheric pressure. Airblast atomization nozzles with either co-rotating (COR) or counter-rotating (CTR) pilot swirl flows were examined using high-speed flame imaging measurements under idle and sub-idle operating conditions. We show that while the amplitude and frequency of limit cycle oscillations are observed to be similar for both cases, detailed examinations of measured experimental data reveal marked differences in stabilization mechanisms and pressure-heat release coupling processes. The spray flame dynamics subjected to counter-rotating swirl flows are governed by large-amplitude pressure oscillations, with maximum peak-to-peak amplitude of about 20 kPa, even under the influence of destructive pressure-heat release rate interference. The mechanism of phase cancellation is closely related to the interactions between a spiral diffusion flame and a periodically-detached reaction zone. Non-premixed liquid-fueled flames involving co-rotating swirl, on the other hand, feature a more compact, intense reaction zone, presumably due to enhanced mixing. In addition, the co-rotating swirl flames lead to the manifestation of aperiodic intermittent bursts before the system couples to Helmholtz-mode instability at a lower equivalence ratio. The intermittency is well defined by subcritical reverse period-doubling bifurcation.
Presenting Author: Byeonguk Ahn Norwegian University of Science and Technology
Presenting Author Biography: Byeonguk Ahn is a postdoc in the Department of Energy and Process Engineering at NTNU. His research focuses on understanding fundamental mechanisms driving thermoacoustic instbilities in gas turbines for aircraft or powerplants. The experimental investigations have been focused on low-frequency combustion instabilities of Jet A-1 spray flames in a model aero-engine gas turbine combustor, and azimuthal thermoacoustic instabilities of swirl stabilized hydrogen blended flames in a pressurized lab-scale annular combustor. In addition, he performed experimental studies on advances for a hydrogen peroxide hybrid rocket system with multi-port designs and an environmentlally friendly material produced by FDM method.
Authors:
Byeonguk Ahn Norwegian University of Science and TechnologyKyu Tae Kim Korea Advanced Institute of Science and Technology
Effect of Counter- and Co-Swirl on Low-Frequency Combustion Instabilities of Jet A-1 Spray Flames
Paper Type
Technical Paper Publication