Structure and dynamics of CH2O, OH, and the velocity field of a confined bluff-body premixed flame, using simultaneous PLIF and PIV at 10 kHz.

Fugger, Christopher A.; Roy, Sukesh; Caswell, Andrew W.; Rankin, Brent A.; Gord, James R.

doi:10.1016/j.proci.2018.05.014

Cited by 34 publications

(4 citation statements)

References 37 publications

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“…In a fully premixed flame, the flame edge can be identified using a maximum gradient definition from an OH-PLIF image (Fugger et al. 2019). Even though the flame in the present experiment is nominally partially premixed, instantaneous acetone-PLIF images obtained concurrently with the OH-PLIF images show good mixing of fuel and air ahead of the regions with significant OH-PLIF signal intensity.…”

Section: Discussionmentioning

confidence: 99%

Impact of precessing vortex core dynamics on the thermoacoustic instabilities in a swirl-stabilized combustor

et al. 2022

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Global instabilities in swirling flows can significantly alter the flame and flow dynamics of swirl-stabilized flames, such as those in modern gas turbine engines. In this study, we characterize the interaction between the precessing vortex core (PVC), which is the consequence of a global hydrodynamic instability, and thermoacoustic instabilities, which are the result of a coupling between combustor acoustics and the unsteady heat release rate. This study is performed using experimental data obtained from a model gas turbine combustor employing two concentric swirling nozzles of air, separated by a ring of fuel injectors, operating at five bar pressure. The flow split between the two streams is systematically varied to observe the impact of flow structure variation on the system dynamics at both non-reacting and reacting conditions. High-speed stereoscopic particle image velocimetry, OH planar laser-induced fluorescence and acetone planar laser-induced fluorescence are used to obtain information about the velocity fields, flame and fuel flow behaviour, respectively. Spectral proper orthogonal decomposition and a complex network analysis are used to identify and characterize the dominant oscillation mechanisms driving the system. In the non-reacting data, a PVC is present in most cases and the amplitude of the oscillation increases with increasing flow through the centre nozzle. In the reacting data, three dominant modes are seen: two thermoacoustic modes and the PVC. Our results show that in the cases where the frequency of the PVC overlaps with either of the thermoacoustic modes, the thermoacoustic modes are suppressed. The complex network analysis coupled with a weakly nonlinear theoretical analysis suggests the mechanisms by which this coupling and suppression of the thermoacoustic mode occur.

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Section: Discussionmentioning

confidence: 99%

Impact of precessing vortex core dynamics on the thermoacoustic instabilities in a swirl-stabilized combustor

et al. 2022

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“…Therefore, the flame surface can be detected by the tomography technique [29][30][31]. Compared to other simultaneous measurements such as LIF [39][40][41][42][43][44][45][46][47], it is possible to eliminate errors caused by time and space mismatching during data integration because the flow distribution and the flame surface can be detected simultaneously from the same image. The experiments were conducted under firing conditions.…”

Section: Resultsmentioning

confidence: 99%

The Interaction between In-Cylinder Turbulent Flow and Flame Front Propagation in an Optical SI Engine Measured by High-Speed PIV

Ikeda¹

2022

Energies

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The relationship between the flow field and flame propagation is essential in determining the dynamics and effects of turbulent flow in an optical SI engine. In this study, high turbulence flow at stable operations was achieved using 12,000 rpm engine speed, 60 kPa absolute intake pressure, 14.7 A/F, and 15 deg. BTDC spark timing. The turbulent flow field and flame propagation interplay were analyzed through the simultaneous high-speed PIV measurements of the in-cylinder flow and flame front propagation under firing conditions. The intensity of the seeder used was optimized by changing the crank angle. Successful simultaneous detection of the flame front and turbulent flow was demonstrated. Strong turbulence was produced at the flame front simultaneously with the flame movement. After ignition timing, the flame accelerated in the unburned region, and a vital turbulence region occurred.

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“…Here, we assume that the flame edge can be defined at the edge of the OH-PLIF signal. In a fully-premixed flame, the flame edge could be identified using a maximum gradient definition from an OH-PLIF image [33]. In a non-premixed flame, the flame is typically identified using maximum OH-PLIF signals [34].…”

Section: Flame Edge Analysismentioning

confidence: 99%

Relative Effects of Velocity- and Mixture-Coupling in a Thermoacoustically Unstable, Partially-Premixed Flame

Karmarkar

Boxx

O’Connor

2021

Volume 3A: Combustion, Fuels, and Emissions

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Combustion instability, which is the result of a coupling between combustor acoustic modes and unsteady flame heat release rate, is a severely limiting factor in the operability and performance of modern gas turbine engines. This coupling can occur through different coupling pathways, such as flow field fluctuations or equivalence ratio fluctuations. In realistic combustor systems, there are complex hydrodynamic and thermo-chemical processes involved, which can lead to multiple coupling pathways. In order to understand and predict the mechanisms that govern the onset of combustion instability in real gas turbine engines, we consider the influences that each of these coupling pathways can have on the stability and dynamics of a partially-premixed, swirl-stabilized flame. In this study, we use a model gas turbine combustor with two concentric swirling nozzles of air, separated by a ring of fuel injectors, operating at an elevated pressure of 5 bar. The flow split between the two streams is systematically varied to observe the impact on the flow and flame dynamics. High-speed stereoscopic particle image velocimetry, OH planar laser-induced fluorescence, and acetone planar laser-induced fluorescence are used to obtain information about the velocity field, flame, and fuel-flow behavior, respectively. Depending on the flow conditions, a thermoacoustic oscillation mode or a hydrodynamic mode, identified as the precessing vortex core, is present. The focus of this study is to characterize the mixture coupling processes in this partially-premixed flame as well as the impact that the velocity oscillations have on mixture coupling. Our results show that, for this combustor system, changing the flow split between the two concentric nozzles can alter the dominant harmonic oscillation modes in the system, which can significantly impact the dispersion of fuel into air, thereby modulating the local equivalence ratio of the flame. This insight can be used to design instability control mechanisms in real gas turbine engines.

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Structure and dynamics of CH2O, OH, and the velocity field of a confined bluff-body premixed flame, using simultaneous PLIF and PIV at 10 kHz.

Cited by 34 publications

References 37 publications

Impact of precessing vortex core dynamics on the thermoacoustic instabilities in a swirl-stabilized combustor

Impact of precessing vortex core dynamics on the thermoacoustic instabilities in a swirl-stabilized combustor

The Interaction between In-Cylinder Turbulent Flow and Flame Front Propagation in an Optical SI Engine Measured by High-Speed PIV

Relative Effects of Velocity- and Mixture-Coupling in a Thermoacoustically Unstable, Partially-Premixed Flame

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Structure and dynamics of CH2O, OH, and the velocity field of a confined bluff-body premixed flame, using simultaneous PLIF and PIV at 10 kHz.

Cited by 34 publications

References 37 publications

Impact of precessing vortex core dynamics on the thermoacoustic instabilities in a swirl-stabilized combustor

Impact of precessing vortex core dynamics on the thermoacoustic instabilities in a swirl-stabilized combustor

The Interaction between In-Cylinder Turbulent Flow and Flame Front Propagation in an Optical SI Engine Measured by High-Speed PIV

Relative Effects of Velocity- and Mixture-Coupling in a Thermoacoustically Unstable, Partially-Premixed Flame

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Structure and dynamics of CH2O, OH, and the velocity field of a confined bluff-body premixed flame, using simultaneous PLIF and PIV at 10 kHz.