Pressure gradient tailoring effects on the mechanisms of bluff-body flame extinction

Morales, Anthony J.; Reyes, Jonathan; Joo, Peter H.; Boxx, Isaac; Ahmed, Kareem A.

doi:10.1016/j.combustflame.2020.01.035

Cited by 18 publications

(10 citation statements)

References 32 publications

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“…The experimental facility used in this study is the same facility detailed by Morales et al (2020a), and consist of a flow conditioning plenum which exhausts into a combustion test section. A full schematic of the experimental facility, including the flow control network, are detailed in previous work (Morales et al 2020a); however, the experiment is also described below for completeness.…”

Section: Experimental Facilitymentioning

confidence: 99%

“…The experiment and diagnostic systems used in this study have been described by the authors in previous literature (Morales et al 2020a), and a brief summary is provided here for completeness. Three simultaneous high-speed diagnostics are implemented to capture the transient blowout process: (1) a wide-field, two-component PIV system, (2) a highresolution, three-component stereoscopic PIV system, and (3) a line-of-sight C 2 */CH* chemiluminescence imaging system.…”

Section: High-speed Diagnosticsmentioning

confidence: 99%

“…Imaging two radical species is advantageous, as the ratio of C 2 */CH* can be used to evaluate the instantaneous equivalence ratio (Morales et al 2020a;Reyes and Kailasanathan 2018;Clark 1958;Jeong et al 2006). In this study, the equivalence ratio is not a primary parameter of interest; however, temporal equivalence ratio curves were evaluated for each turbulence condition to verify the blowout equivalence ratio, which is presented in Table 1 and will be discussed later.…”

Section: Chemiluminescence Imaging Systemsmentioning

confidence: 99%

“…The first stage consist of localized extinctions along the flame front, which occur at lean conditions due to a decreased flame speed and decreased density ratio between reactants and products. The decreased flame speed causes the flame front to reside closer to the shear layer vorticity regions (Chaudhuri et al 2010), while the decreased density ratio diminishes the production of baroclinic and dilatation vorticity and allows the shear layer vorticity to increase in magnitude (Morales et al 2019(Morales et al , 2020a. Combined, these effects lead to flame and shear layer interactions, which invoke high strain rate magnitudes along the flame front (Chaudhuri et al 2010;Tuttle et al 2013).…”

Section: Introductionmentioning

confidence: 99%

“…The topological alteration of the flame is linked with a transition from a convective shear layer instability to an absolute instability (which is more easily destabilized) in the bluff-body wake (Emerson and O'connor 2012). The transition to an absolute instability causes the flow field oscillation frequencies to decrease with the equivalence ratio (Morales et al 2019(Morales et al , 2020a, until global blowout occurs and the wake locks into the BVK instability (Emerson and O'connor 2012). Thus, the characteristics of the flame are highly sensitive to hydrodynamic instabilities near blowout.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Turbulence-Driven Blowout Instabilities of Premixed Bluff-Body Flames

Morales

Genova

Reyes

et al. 2021

Flow Turbulence Combust

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Bluff-body flame instabilities are experimentally investigated under varying turbulence conditions during lean blowout. For all turbulence conditions, the blowout process is induced through a temporal reduction of the fuel flow rate to capture the flame-flow dynamics approaching blowout. Simultaneous high-speed particle image velocimetry (PIV), stereoscopic PIV, and C 2 */CH* chemiluminescence imaging are employed, along with an independent CH* imaging system, to capture flame-flow instabilities. Proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) techniques are used to identify prominent flame oscillations and evaluate recurring spatiotemporal modes during blowout. The results reveal that the dominant flame oscillations and wrinkling characteristics are directly dependent on the turbulence conditions in the combustor. Specifically, the flame-flow oscillations are strongly coupled with the integral length scales, which were able to collapse the oscillation frequencies to a unified value. The turbulence-driven flameflow oscillations are shown to largely impact the magnitude, temporal evolution, and oscillatory behavior of the flame strain rate. As the turbulence intensity is increased, the oscillation of the flame strain rate increases in frequency, making it more likely for localized extinctions to occur. Additionally, the magnitude of the flame strain rate increases at high turbulence intensities and accelerates the lean blowout process.

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Section: Experimental Facilitymentioning

confidence: 99%

Section: High-speed Diagnosticsmentioning

confidence: 99%

Section: Chemiluminescence Imaging Systemsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Turbulence-Driven Blowout Instabilities of Premixed Bluff-Body Flames

Morales

Genova

Reyes

et al. 2021

Flow Turbulence Combust

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Investigation of the applicability of conditioned particle image velocimetry under conditions close to lean blow-off

Wang

Liu

et al. 2023

Exp Fluids

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In recent years, conditioned particle image velocimetry (CPIV) has attracted much attention for flame front extraction. It is an economical and straightforward technique because the flame front can be obtained simply from Mie-scattering images. In the current work, Mie-scattering and hydroxyl planar laser-induced fluorescence (OH-PLIF) measurements were taken simultaneously to study the applicability of CPIV under conditions with varying equivalence ratios, and the reliable working range of the CPIV method and the source of bias were clarified quantitatively. The premixed dimethyl ether (DME)/air flames stabilized on a two-dimensional bluff body were tested. It is found that the accuracy of the CPIV method worsens as the equivalence ratio decreases. The bias of CPIV is supposed to be related to the flame structure and aerodynamics. The extraction deviation in the upstream region for the stable flames is more significant than that in the downstream area due to the intensified interaction between the shear layer and flame near the bluff body. However, for the flames approaching the lean blow-off (LBO), the bias in the upstream part is smaller than that in the downstream area, which is related to the “back-support” of the hot recirculation zone (RZ). In addition, the difference between the results obtained by CPIV and OH-PLIF is usually the preheat layer of flame and concave-wrinkled location of OH-PLIF filled with CH2O radicals, especially under conditions close to the LBO, which can be used to estimate the spatial distribution of CH2O. Graphical Abstract

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