Role of inertial forces in flame-flow interaction during premixed swirl flame flashback

Ranjan, Rakesh; Ebi, Dominik; Clemens, Noel T.

doi:10.1016/j.proci.2018.09.010

Cited by 13 publications

(9 citation statements)

References 12 publications

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“…The incoming stream is moreover radially deflected by the PVC 108 in proximity of the burner nozzle resulting in asymmetric heat release downstream. This deflection can assist upstream flame propagation by reducing the flame-normal approach speed of the incoming annular jet 109 .…”

Section: Please Cite This Articlementioning

confidence: 99%

A combined oscillation cycle involving self-excited thermo-acoustic and hydrodynamic instability mechanisms

2021

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The paper examines the combined effects of several interacting thermo-acoustic and hydrodynamic instability mechanisms that are known to influence self-excited combustion instabilities often encountered in the late design stages of modern lowemission gas turbine combustors. A compressible large eddy simulation approach is presented, comprising the flame burning regime independent, modelled probability density function evolution equation/stochastic fields solution method. The approach is subsequently applied to the PRECCINSTA (PREdiction and Control of Combustion INSTAbilities) model combustor and successfully captures a fully self-excited limit-cycle oscillation without external forcing. The predicted frequency and amplitude of the dominant thermo-acoustic mode and its first harmonic are found to be in excellent agreement with available experimental data. Analysis of the phaseresolved and phase-averaged fields leads to a detailed description of the superimposed mass flow rate and equivalence ratio fluctuations underlying the governing feedback loop. The prevailing thermo-acoustic cycle features regular flame lift-off and flashback events in combination with a flame angle oscillation, as well as multiple hydrodynamic phenomena, i.e. toroidal vortex shedding and a precessing vortex core. The periodic excitation and suppression of these hydrodynamic phenomena is confirmed via spectral proper orthogonal decomposition and shown to be controlled by an oscillation of the instantaneous swirl number. Their local impact on the heat release rate, which is predominantly modulated by flame-vortex roll-up and enhanced mixing of fuel and oxidiser, is further described and investigated. Finally, the temporal relationship between the flame 'surface area', flame-averaged mixture fraction and global heat release rate are found to be directly correlated.

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Section: Please Cite This Articlementioning

confidence: 99%

A combined oscillation cycle involving self-excited thermo-acoustic and hydrodynamic instability mechanisms

2021

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“…Recent experimental studies reported that, once a flame retreats into an enclosure (i.e. a confined reactive flow configuration), the influence of the flame on the approaching flow and on the heat transfer again impacts flashback behaviour (Eichler et al 2011;Eichler & Sattelmayer 2012;Duan et al 2013a,b;Baumgartner et al 2015;Ebi & Clemens 2016;Kalantari et al 2016;Ranjan, Ebi & Clemens 2019). There are several concurrent reasons causing the flame to retreat into an enclosure, such as tip temperature (Eichler et al 2011;Duan et al 2013a,b;Kalantari et al 2016), operation pressure (Daniele et al 2010;Kalantari et al 2016) and combustion dynamics (Eichler et al 2011).…”

Section: Introductionmentioning

confidence: 99%

“…Baumgartner et al (2015) performed an experimental study of the transition from a stable flame to flashback into a duct, where the velocity profile of the burner flow is distorted during the transition. Clemens et al (Ebi & Clemens 2016;Ranjan et al 2019) conducted experiments of boundary layer flashback of a swirling flame in a mixing tube with a bluff body, and observed the reverse-flow pockets associated with positively curved portions of the flame front (bulges). The above experimental studies concluded that flashback in a confined reactive flow configuration is significantly influenced by the interactions between the flame and the approaching flow.…”

Section: Introductionmentioning

confidence: 99%

Study of flame–flow interactions in turbulent boundary layer premixed flame flashback over a flat plate using direct numerical simulation

Chen,

Wang,

Gruber

et al. 2023

J. Fluid Mech.

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Lean hydrogen/air premixed flame flashback in a turbulent boundary layer over a flat plate is investigated using three-dimensional direct numerical simulation with detailed chemical kinetics. The upstream propagation of the flame takes place in near-wall turbulence and the interaction between the flame and the approaching reactant flow is studied. It is found that backflow regions are always present immediately upstream of flame bulges that are convex towards the reactants, confirming earlier observations. A flashback speed, including the effects of flame displacement speed and flow velocity, is introduced to quantify the flame flashback behaviour. This analysis indicates that the flashback speed is overall positive and it is considerably affected by the presence of the backflow regions. A budget analysis of the pressure transport equation is performed to explain the presence of the backflow regions. It is suggested that the positive dilatation and thermal diffusion terms near the leading edge of flame bulges are the main reasons for the pressure increase, leading to an adverse pressure gradient. The effects of the flame-induced adverse pressure gradient on the structures of the turbulent boundary layer are also investigated. It is revealed that the near-wall mean velocity and skin-friction coefficient are reduced due to the adverse pressure gradient. The coherent vortical structures of the boundary layer turbulence are lifted by the adverse pressure gradient. The analysis of the Reynolds stress component showed that the ejection event is augmented by combustion while the sweep event is attenuated, which facilitates the occurrence of flame flashback.

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“…Investigations of flashback in swirl burners, which have mainly been limited to atmospheric conditions, have shown that flashback can occur in the core of a swirling flow (flashback due to combustion-induced vortex-breakdown, CIVB) [6], the outer (mixing section wall) boundary layer [7] or the inner boundary layer in swirl burners with a central bluff body [8]. Recent detailed studies showed that the relevant flow-flame interaction and dominating mechanisms facilitating flashback in the boundary layer of a swirl flow can differ from BLF and CIVB type flashback [9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Swirl flame boundary layer flashback at elevated pressure: Modes of propagation and effect of hydrogen addition

Ebi

Bombach

Jansohn

2021

Proceedings of the Combustion Institute

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Role of inertial forces in flame-flow interaction during premixed swirl flame flashback

Cited by 13 publications

References 12 publications

A combined oscillation cycle involving self-excited thermo-acoustic and hydrodynamic instability mechanisms

A combined oscillation cycle involving self-excited thermo-acoustic and hydrodynamic instability mechanisms

Study of flame–flow interactions in turbulent boundary layer premixed flame flashback over a flat plate using direct numerical simulation

Swirl flame boundary layer flashback at elevated pressure: Modes of propagation and effect of hydrogen addition

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