Turbulent flame-vortex dynamics of bluff-body premixed flames

Geikie, Marissa K.; Rising, Cal; Morales, Anthony J.; Ahmed, Kareem A.

doi:10.1016/j.combustflame.2020.09.023

Cited by 18 publications

(6 citation statements)

References 53 publications

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“…At φ = 0.5, the growth rate at non-ignited conditions is 5.3 s −1 , while the ignited flow is stable with the largest growth rate of −20.3s −1 . Such a stabilising effect of ignition has often been observed in experiments and numerical simulations (Bill & Tarabanis 1986;Mehta & Soteriou 2003;Erickson & Soteriou 2011;Kedia & Ghoniem 2014;Oberleithner et al 2015b;Geikie et al 2021).…”

Section: Stabilisation By Ignition: a Wavemaker Analysismentioning

confidence: 62%

“…Performing linear eigenmode analysis on ignited and non-ignited base flows, at identical flow parameters, we first addressed the question of why ignition stabilises the flame, as has been often observed in previous studies (Bill & Tarabanis 1986;Mehta & Soteriou 2003;Erickson & Soteriou 2011;Kedia & Ghoniem 2014;Oberleithner et al 2015b;Geikie et al 2021). It is found that reaction strongly weakens the base flow shear in the portion of the recirculation bubble where the wavemaker is located.…”

Section: Discussionmentioning

confidence: 91%

“…2015 b ; Geikie et al. 2021). It is found that reaction strongly weakens the base flow shear in the portion of the recirculation bubble where the wavemaker is located.…”

Section: Discussionmentioning

confidence: 99%

“…2015 b ; Geikie et al. 2021).

Figure 7.Comparison of base flow quantities between ignited (upper half, ) and non-ignited case (lower half, ) at .…”

Section: Reacting Flow: Eigenmodes Of the Steady Base Statementioning

confidence: 99%

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Global linear stability analysis of a flame anchored to a cylinder

2022

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This study investigates the linear stability of a laminar premixed flame, anchored on a square cylinder and confined inside a channel. Many modern linear analysis concepts have been developed and validated around non-reacting bluff-body wake flows, and the objective of this paper is to explore whether those tools can be applied with the same success to the study of reacting flows in similar configurations. It is found that linear instability analysis of steady reacting flow states accurately predicts critical flow parameters for the onset of limit-cycle oscillations, when compared to direct numerical simulation performed with a simple one-step reaction scheme in the low Mach number limit. Furthermore, the linear analysis predicts a strong stabilising effect of flame ignition, consistent with documented experiments and numerical simulations. Instability in ignited wake flows is, however, found to set in at sufficiently high Reynolds number, and a linear wavemaker analysis characterises this instability as being driven by hydrodynamic mechanisms of a similar nature as in non-reacting wake flows. The frequency of nonlinear limit-cycle flame oscillations in this unstable regime is retrieved accurately by linear eigenmode analysis performed on the time-averaged mean flow, under the condition that the full set of the reacting flow equations is linearised. If, on the contrary, unsteadiness in the density and in the reaction rate are excluded from the linear model, then the congruence between linear and nonlinear dynamics is lost.

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Section: Stabilisation By Ignition: a Wavemaker Analysismentioning

confidence: 62%

Section: Discussionmentioning

confidence: 91%

“…2015 b ; Geikie et al. 2021). It is found that reaction strongly weakens the base flow shear in the portion of the recirculation bubble where the wavemaker is located.…”

Section: Discussionmentioning

confidence: 99%

“…2015 b ; Geikie et al. 2021).

Figure 7.Comparison of base flow quantities between ignited (upper half, ) and non-ignited case (lower half, ) at .…”

Section: Reacting Flow: Eigenmodes Of the Steady Base Statementioning

confidence: 99%

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Global linear stability analysis of a flame anchored to a cylinder

2022

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“…The flame stabilizing principle of the bluff-body is to generate recirculation flow inside the wake zones to extend the residence time of reactants and achieve a stabilized flame . Based on flow field and combustion measurements, recent studies have acquired a deeper understanding of the flow-flame coupled dynamics , and lean blow-off (LBO) or near LBO characteristics − for the bluff-body stabilized flame.…”

Section: Introductionmentioning

confidence: 99%

Partially Premixed Ignition for a Bluff-Body Flameholder under Various Igniter and Inlet Conditions

Zhang

2021

ACS Omega

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This study applies experimental methods to investigate the partially premixed ignition characteristics of a bluff-body flameholder with a pilot stage. The ignition fuel–air ratio (FAR) under different igniter and inlet conditions is obtained, while the ignition process is recorded with a high-speed photography device. Numerical simulations are carried out to investigate the relationship between the flow field, fuel distribution, and ignition process. The results show that a higher total capacitance energy storage of the igniter, inlet Mach number, or total pressure inside the combustion chamber will help increase the ignition performance, accelerate the development of the flame, and shorten the ignition delay. The flame propagation routine of the flameholder is controlled by several pairs of symmetrical recirculation zones behind the flameholder structure and the specific uneven fuel distribution caused by the flow field. This study provides a detailed understanding of the ignition process for the bluff-body flameholder.

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