Effects of Damköhler number on flame extinction and reignition in turbulent non-premixed flames using DNS

Lignell, David O.; Chen, Jacqueline H.; Schmutz, Hans

doi:10.1016/j.combustflame.2010.10.027

Cited by 55 publications

(47 citation statements)

References 26 publications

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“…7c, in which case shows a slight decrease with some fluctuations. Also, this trend of BO2 case is contrary to the results from a recent DNS of planar, non-premixed ethylene jet flames [55], where the area of instantaneous ξ st iso-surfaces increases as the local extinction degree increases. This may be attributed to the different mixing levels in the current recirculating flows and the jet ones, and their response to the occurrence of extinction.…”

Section: Localized Extinction and Re-ignition In Blow-offcontrasting

confidence: 55%

Prediction of Global Extinction Conditions and Dynamics in Swirling Non-premixed Flames Using LES/CMC Modelling

Zhang

Mastorakos

2015

Flow Turbulence Combust

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The Large Eddy Simulation (LES)/three-dimensional Conditional Moment Closure (CMC) model with detailed chemistry is applied to predict the operating condition and dynamics of complete extinction (blow-off) in swirling non-premixed methane flames. Using model constants previously selected to provide relatively accurate predictions of the degree of local extinction in the piloted jet flames Sandia D−F, the error in the blow-off air velocity predicted by LES/3D-CMC in short, recirculating flames with strong swirl for a range of fuel flow rates is within 25 % of the experimental value, which is considered a new and promising result for combustion LES that has not been applied before for the prediction of the whole blow-off curve in complex geometries. The results also show that during the blow-off transient, the total heat release gradually decreases over a duration that agrees well with experiment. The evolution of localized extinction, reactive scalars and scalar dissipation rate is analyzed. It has been observed that a consistent symptom for flames approaching blow-off is the appearance of high-frequency and high-magnitude fluctuations of the conditionally filtered stoichiometric scalar dissipation rate, resulting in an increased fraction of local extinction over the stoichiometric mixture fraction iso-surfaces. It is also shown that the blow-off time changes with the different blow-off conditions.

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Section: Localized Extinction and Re-ignition In Blow-offcontrasting

confidence: 55%

Prediction of Global Extinction Conditions and Dynamics in Swirling Non-premixed Flames Using LES/CMC Modelling

Zhang

Mastorakos

2015

Flow Turbulence Combust

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“…The velocity is initialized such that the Reynolds number is approximately 5,000. This configuration is being studied in detail and compared to DNS results [17]. The ODT parameters used in the simulation (and described in the "Appendix") are C = 10, Z = 200, and β = 0.9.…”

Section: Demonstrations and Discussionmentioning

confidence: 99%

“…This assumption is approached for small streamwise displacements in actual jets. The temporal configuration is commonly used in direct numerical simulation (DNS) where computational domain sizes are limited [17]. In DNS, there is a fixed streamwise expanse and the flow is periodic in the streamwise and spanwise directions so that there is a single direction of mean shear.…”

Section: Temporal Jetmentioning

confidence: 99%

Mesh adaption for efficient multiscale implementation of one-dimensional turbulence

Lignell

Kerstein

Sun

et al. 2012

Theor. Comput. Fluid Dyn.

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One-Dimensional Turbulence (ODT) is a stochastic model for turbulent flow simulation. In an atmospheric context, it is analogous to single-column modeling (SCM) in that it lives on a 1D spatial domain, but different in that it time advances individual flow realizations rather than ensemble-averaged quantities. The lack of averaging enables a physically sound multiscale treatment, which is useful for resolving sporadic localized phenomena, as seen in stably stratified regimes, and sharp interfaces, as observed where a convective layer encounters a stable overlying zone. In such flows, the relevant scale range is so large that it is beneficial to enhance model performance by introducing an adaptive mesh. An adaptive-mesh algorithm that provides the desired performance characteristics is described and demonstrated, and its implications for the ODT advancement scheme are explained.

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“…Lignell et al [14] performed a parametric study of flame extinction and reignition in non-premixed ethylene/air flames using a 3D DNS configuration with detailed chemistry similar to that of Hawkes et al [12]. Varying Damköhler number at fixed Reynolds was considered.…”

Section: Introductionmentioning

confidence: 99%

“…Several past DNS works and analysis using DNS data have focused on non-premixed flame extinction in various environments [9][10][11][12][13][14][15][16][17]. Dependence of local extinction and reignition on the overall mixing in CO/H 2 non-premixed turbulent jet flames were studied using the one-dimensional turbulence model by Hewson and Kerstein [9].…”

Section: Introductionmentioning

confidence: 99%

Direct numerical simulations of non-premixed ethylene–air flames: Local flame extinction criterion

Lecoustre

Arias

Roy

et al. 2014

Combustion and Flame

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a b s t r a c tDirect Numerical Simulations (DNS) of ethylene/air diffusion flame extinctions in decaying twodimensional turbulence were performed. A Damköhler-number-based flame extinction criterion as provided by classical large activation energy asymptotic (AEA) theory is assessed for its validity in predicting flame extinction and compared to one based on Chemical Explosive Mode Analysis (CEMA) of the detailed chemistry. The DNS code solves compressible flow conservation equations using high order finite difference and explicit time integration schemes. The ethylene/air chemistry is simulated with a reduced mechanism that is generated based on the directed relation graph (DRG) based methods along with stiffness removal. The numerical configuration is an ethylene fuel strip embedded in ambient air and exposed to a prescribed decaying turbulent flow field. The emphasis of this study is on the several flame extinction events observed in contrived parametric simulations. A modified viscosity and changing pressure (MVCP) scheme was adopted in order to artificially manipulate the probability of flame extinction. Using MVCP, pressure was changed from the baseline case of 1 atm to 0.1 and 10 atm. In the high pressure MVCP case, the simulated flame is extinction-free, whereas in the low pressure MVCP case, the simulated flame features frequent extinction events and is close to global extinction. Results show that, despite its relative simplicity and provided that the global flame activation temperature is correctly calibrated, the AEA-based flame extinction criterion can accurately predict the simulated flame extinction events. It is also found that the AEA-based criterion provides predictions of flame extinction that are consistent with those provided by a CEMA-based criterion. This study supports the validity of a simple Damköhler-number-based criterion to predict flame extinction in engineering-level CFD models.

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Effects of Damköhler number on flame extinction and reignition in turbulent non-premixed flames using DNS

Cited by 55 publications

References 26 publications

Prediction of Global Extinction Conditions and Dynamics in Swirling Non-premixed Flames Using LES/CMC Modelling

Prediction of Global Extinction Conditions and Dynamics in Swirling Non-premixed Flames Using LES/CMC Modelling

Mesh adaption for efficient multiscale implementation of one-dimensional turbulence

Direct numerical simulations of non-premixed ethylene–air flames: Local flame extinction criterion

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