Measurement of Flame Frequency Response Functions Under Exhaust Gas Recirculation Conditions

Abstract

Exhaust gas recirculation has been proposed as a potential strategy for reducing the cost and efficiency penalty associated with postcombustion carbon capture. However, this approach may cause as-yet unresolved effects on the combustion process, including additional potential for the occurrence of thermoacoustic instabilities. Flame dynamics, characterized by the flame transfer function, were measured in traditional swirl stabilized and low-swirl injector combustor configurations, subject to exhaust gas circulation simulated hy N2 and CO2 dilution. The flame transfer functions exhibited behavior consistent with a low-pass filter and showed phase dominated by delay. Flame transfer function frequencies were nondimensionalized using Strouhal number to highlight the convective nature of this delay. Dilution was observed to influence the dynamics primarily through its role in changing the size of the flame, indicating that it plays a similar role in determining the dynamics as changes in the equivalence ratio. Notchlike features in the flame transfer function were shown to be related to interference behaviors associated with the convective nature of the flame response. Some similarities between the two stabilization configurations proved limiting and generalization of the physical behaviors will require additional investigation.

Investigation on the Flame Front and Flow Field in Acoustically Excited Swirling Flames with and without Confinement

“…4, 6 and 7, the base part of the flame front locates in a narrow region while the tip part disperse in a wide region. Similar phenomenon has also been studied by Palies (Palies et al, 2010) and Ranalli (Ranalli and Ferguson, 2012)using the CH* and OH* chemiluminescence emission images. The chemiluminescence images are divided into an upper window and a lower window.…”

Investigation of Harmonic Response in Non-Premixed Swirling Combustion to Low-Frequency Acoustic Excitations

“…Further calculations for the ratio of vortex axial convective velocity to the mean inlet jet velocity U j (1.105 m/s) revealed that under excitation frequencies of 20 Hz, the axial vortex convective velocity is slightly less than the jet velocity. This supported the assumption that the vortex convective velocity was often regarded as the jet velocity [6,47]. Future research is necessary to explore the influence of flame thermal expansion on vortex convective velocity under reacting conditions.…”

Thermoacoustic Stability Boundaries in the Model Combustion Chamber with a Gas-Centered Swirl Coaxial Injector

“…In the former, the instability occurs spontaneously without external perturbation [15,16]. On the other hand, forced instability is triggered by perturbation [7,17]. A gas-centered swirl coaxial (GCSC) injector has been adopted widely in high-performance rocket engines, especially, with a staged combustion cycle.…”