Stability characteristics and flowfields of turbulent non-premixed swirling flames

Al-Abdeli, Yasir M.; Masri, Assaad R.

doi:10.1088/1364-7830/7/4/007

Cited by 79 publications

(89 citation statements)

References 28 publications

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“…Different extinction modes, i.e. base and neck blow-off, have been observed in an unconfined swirl burner and the measured stability limits and flame topologies were strongly influenced by the swirl and Reynolds numbers [23]. The blow-off transient, visualized by OH* chemiluminescence and OH-PLIF for confined swirling non-premixed flames, were studied by Cavaliere et al [15].…”

Section: Introductionmentioning

confidence: 99%

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: Introductionmentioning

confidence: 99%

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 numerical and computational detailed are presented in section 4, and in section 5 LES results obtained are compared with experimental measurements and discussed. Figure 1 shows the Sydney swirl burner configuration, which is an extension of the wellcharacterised Sydney bluff body burner to swirling flames (Al-Abdeli and Masri, 2003). It has a 60mm diameter annulus for a primary swirling air stream surrounding the circular bluff body of diameter D=50mm.…”

Section: Introductionmentioning

confidence: 99%

LES of Recirculation and Vortex Breakdown in Swirling Flames

Malalasekera

Ranga-Dinesh

Ibrahim

et al. 2008

Combustion Science and Technology

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In this study large eddy simulation (LES) technique has been applied to predict a selected swirling flame from the Sydney swirl burner experiments. The selected flame is known as the SM1 flame operated with fuel CH 4 at a swirl number of 0.5. In the numerical method used, the governing equations for continuity, momentum and mixture fraction are solved on a structured Cartesian grid. Smagorinsky eddy viscosity model with the localised dynamic procedure of Piomelli and Liu is used as the subgrid scale turbulence model. The conserved scalar mixture fraction based thermo-chemical variables are described using the steady laminar flamelet model. The GRI 2.11 is used as the chemical mechanism. The Favre filtered scalars are obtained from the presumed beta probability density function ( β -PDF) approach. The results show that with appropriate inflow and outflow boundary conditions LES successfully predicts the upstream recirculation zone generated by the bluff body and the downstream vortex breakdown zone induced by swirl with a high level of accuracy. Detailed comparison of LES results with experimental measurements show that the mean velocity field and their rms fluctuations are predicted very well. The predictions for the mean mixture fraction, subgrid variance and temperature are also reasonably successful at most axial locations. The study demonstrates that LES together with the laminar flamelet model in general provides a good technique for predicting the structure of turbulent swirling flames.

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“…In our computations we assumed x mm as axial distance and r mm as radial distance. In the present study only the pure methane SM1 flame from the experimental data base (Kalt et al 2002, Al-Abdeli and Masri, 2003, Masri et al 2004) is considered, which has a fuel jet velocity of 32.7m/s with a swirl number S=0.5. The flame contains two recirculation zones, the first closer to the bluff body which stagnates at about 43mm and the second further downstream which stagnates at 70mm on the centreline.…”

Section: Swirl Burner and Flame Conditionsmentioning

confidence: 99%

“…Therefore selecting a stoichimetric mixture fraction value as a threshold could help to determine the similarities and differences between the mixture 23 fraction and temperature intermittency. Here we used a threshold value of 0.054 th f  which is a stoichiometric mixture fraction for pure methane SM1 swirling flame (Kalt et al 2002, Al-Abdeli andMasri, 2003). As seen in Figure 18 the radial variation of the mixture fraction intermittency follows a Gaussian shape at all axial locations for all three cases.…”

Section: Mixture Fraction Intermittencymentioning

confidence: 99%

“…The swirl burner used in this work is the Sydney burner (Al-Abdeli and Masri, 2003, Kalt et al 2002, Masri et al 2004, which is frequently used in modelling unconfined swirling flames. Our previous LES investigations targeted some of the Sydney flames for LES validation (Malalasekera et al 2007(Malalasekera et al , 2008 and instability analysis of swirling flames (RangaDinesh et al 2009).…”

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confidence: 99%

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