Large eddy simulation of mean and oscillating flow in a side-dump ramjet combustor

Roux, Anthony; Gicquel, Laurent; Sommerer, Y.; Poinsot, Thiérry

doi:10.1016/j.combustflame.2007.06.015

Cited by 64 publications

(39 citation statements)

References 47 publications

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“…A compressible LES code [4,12,[22][23][24][25][26][27][28][29][30][31][32] is used to solve the Navier-Stokes equations on hybrid (structured and unstructured) grids with real thermo-chemistry. A Taylor-Galerkin weighted residual central distribution scheme is used for the numerical integration [28,33,34].…”

Section: The Numerical Setupmentioning

confidence: 99%

Large Eddy Simulation of combustion instabilities in a lean partially premixed swirled flame

Franzelli

Riber

Gicquel

et al. 2012

Combustion and Flame

280

162

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a b s t r a c tThis paper investigates one issue related to Large Eddy Simulation (LES) of self-excited combustion instabilities in gas-fueled swirled burners: the effects of incomplete mixing between fuel and air at the combustion chamber inlet. Perfect premixing of the gases entering the combustion chamber is rarely achieved in practical applications and this study investigates its impact by comparing LES assuming perfect premixing and LES where the fuel jets are resolved so that fuel/air mixing is explicitely computed. This work demonstrates that the perfect premixing assumption is reasonable for stable flows but is not acceptable to predict self-excited unstable cases. This is shown by comparing LES and experimental fields in terms of mean and RMS fields of temperature, species, velocities as well as mixture fraction pdfs and unsteady activity for two regimes: a stable one at equivalence ratio 0.83 and an unstable one at 0.7. IntroductionThe instabilities of swirled turbulent flows have been the subject of intense research in the last ten years. One important issue has been to identify the possibilities offered by simulation and especially Large Eddy Simulation (LES) to predict self-excited combustion oscillations. The specific example of swirled combustors where flames couple with acoustic modes has received significant attention [1-4] because such oscillations are often found in real gas turbines [5,6]. An important question in swirled unstable flames is the effect of mixing on stability. In most real systems, combustion is not fully premixed and even in laboratories, very few swirled flames are truly fully premixed. The effects of equivalence ratio fluctuations on flame stability in combustors have been known for a long time [7,8]: changes in air inlet velocity induce variations of the flow rate through the flame but may also induce mixing fluctuations and the introduction into the combustion zone of nonconstant equivalence ratio pockets. These pockets create unsteady combustion and can generate instabilities.In many experiments, LES is performed assuming perfect mixing mainly because the computational work is simpler: there is no need to mesh the fuel injection holes or to resolve the zone where these jets mix with air. However, this assumption totally eliminates fluctuations of equivalence ratio as a mechanism of instability, thereby limiting the validity of the LES. One specific example of such limitations is reported in the experiment of [9][10][11] which has been computed by multiple groups [12][13][14][15][16]. This methane/air swirled combustor was especially built to study combustion instabilities in such systems and for all computations up to now, perfect mixing has been assumed by LES experts because methane was injected in the swirler, far upstream of the combustor, suggesting that perfect mixing is achieved before the combustion zone. Interestingly, all computations performed with perfect mixing assumptions have failed to predict the unstable modes observed in the experiments. Moreover, recent...

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Section: The Numerical Setupmentioning

confidence: 99%

Large Eddy Simulation of combustion instabilities in a lean partially premixed swirled flame

Franzelli

Riber

Gicquel

et al. 2012

Combustion and Flame

280

162

View full text Add to dashboard Cite

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“…It is a cell-vertex/finite element code, explicit in time, which solves the compressible Navier-Stokes equations on unstructured meshes for the conservative variables (mass density, momentum and total energy). AVBP is dedicated to Large-Eddy Simulations and Direct Numerical Simulations and has been widely used and validated in the past years in all kinds of configurations (Schönfeld and Rudgyard, 1999;Moureau et al, 2005;Schmitt et al, 2007;Prière et al, 2004;Roux et al, 2008;Mendez and Nicoud, 2008b). The numerical scheme is the TTGC (Twostep Taylor Galerkin C) scheme (Colin and Rudgyard, 2000): this essentially non dissipative scheme was specifically developed to handle unsteady turbulent flows with unstructured meshes.…”

Section: The Les Codementioning

confidence: 99%

Acoustic modeling of perforated plates with bias flow for Large-Eddy Simulations

Mendez

Eldredge

2009

Journal of Computational Physics

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The study of the acoustic effect of perforated plates by Large-Eddy Simulations is reported. The ability of compressible Large-Eddy Simulations to provide data on the flow around a perforated plate and the associated acoustic damping is demonstrated. In particular, assumptions of existing models of the acoustic effect of perforated plate are assessed thanks to the Large-Eddy Simulations results. The question of modeling the effect of perforated plates is then addressed in the context of thermoacoustic instabilities of gas turbine combustion chambers. Details are provided about the implementation, validation and application of a homogeneous boundary condition modeling the acoustic effect of perforated plates for compressible Large-Eddy Simulations of the flow in combustions chambers cooled by full-coverage film cooling.

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“…with a pre-exponential factor A=3.2916×10 10 [cgs] and an activation energy E a =31,126 cal.mol −1 . f (φ) allows to correctly predict laminar flame speed for an extended range of equivalence ratio.…”

Section: Combustion Model: Avbpmentioning

confidence: 99%

“…This experiment is of first interest because of the strong variation of equivalent ratio in the "dome zone", the downstream zone of the main chamber placed before the air inlet. It has been shown that predicting mixing was hardly possible with Reynolds Average Numerical Simulation (RANS) whereas Large Eddy Simulation method (LES) gives good agreement with the experiment [8,9,10]. A second experiment explores reacting flows inside a dump combustor with two opposed lateral air inlet curved at 45 • .…”

Section: Introductionmentioning

confidence: 99%

Comparison of numerical methods and combustion models for LES of a ramjet

Roux

Reichstadt

Bertier

et al. 2009

Comptes Rendus. Mécanique

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Ramjets are very sensitive to instabilities and their numerical predictions can only be addressed adequately by Large Eddy Simulation (LES). With this technique, solvers can be implicit or explicit and handle structured, unstructured or hybrid meshes... Turbulence and combustion models are other sources of differences. The impact of these options is here investigated for the ONERA ramjet burner. To do so, two LES codes developed by ONERA and CERFACS compute one stable operating condition. Preliminary LES results of the two codes underline the overall robustness of LES. Mean flow features at the various critical sections are reasonably well predicted by both codes. Disagreement mainly appear in the chamber where combustion positions differ pointing to the importance of the combustion and subgrid mixing models. The two LES produce different energy containing motions. With CEDRE, a low frequency dominates while AVBP produces different ranges of low frequencies that can be linked with acoustic modes of the configuration. To cite this article : A. Roux et al., C. R. Mecanique (2009). RésuméStratégie numérique pour la simulation aux grandeséchelles de statoréacteurs. L'impact des méthodes numériques ainsi que du modèle de combustion sur la simulation aux grandeséchelles d'un statofuséeétudié expérimentalement par l'ONERA est analys. Pour ce faire, deux codes développés respectivement par l'ONERA et le CERFACS sont utilisés pour calculer un point de fonctionnement stable. Les caractéristiques moyennes sont raisonnablement bien prédites par les deux codes. Les désaccords apparaissent dans la chambre de combustion où la position des zones réactives diffèrent soulignant l'importance des modèles utilisés. Les deux SGE produisent des contenusénergétiques fréquentiels différents. Avec CEDRE, une basse fréquence domine le spectre tandis qu'AVBP montre toute une gamme de basses fréquences qui peutêtre liée aux modes acoustiques de la configuration. Pour citer cet article : A. Roux et al., C. R. Mecanique (2009).

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Large eddy simulation of mean and oscillating flow in a side-dump ramjet combustor

Cited by 64 publications

References 47 publications

Large Eddy Simulation of combustion instabilities in a lean partially premixed swirled flame

Large Eddy Simulation of combustion instabilities in a lean partially premixed swirled flame

Acoustic modeling of perforated plates with bias flow for Large-Eddy Simulations

Comparison of numerical methods and combustion models for LES of a ramjet

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