Large eddy simulation of a model gas turbine combustor

Mare, Francesca di; Jones, W.P.; Menzies, Kevin

doi:10.1016/j.combustflame.2004.01.008

Cited by 160 publications

(106 citation statements)

References 40 publications

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“…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][2][3][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.…”

Section: Introductionmentioning

confidence: 99%

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

Franzelli

Riber

Gicquel

et al. 2012

Combustion and Flame

275

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: Introductionmentioning

confidence: 99%

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

Franzelli

Riber

Gicquel

et al. 2012

Combustion and Flame

275

162

View full text Add to dashboard Cite

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“…The concept of explicitely solving for the large geometry-dependent turbulent scales while modelling the dissipative behavior of the smaller scales, combined with high order numerical schemes and optimized unstructured meshes, has already shown its accuracy for turbulent non-reacting [20][21][22] and reacting flows [23][24][25] and recent results obtained on burners of gas turbine configurations have revolutionized the field of CFD combustion [26][27][28][29][30].…”

Section: Numerical Simulations Of Rocket Ignition Are Mainly Based Onmentioning

confidence: 99%

Large eddy simulation of laser ignition and compressible reacting flow in a rocket-like configuration

Lacaze

Cuenot

Poinsot

et al. 2009

Combustion and Flame

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“…Even with the greater spatial resolution of LES compared to RANS the combustion process still takes place on a scale which cannot be resolved by the grid, and as such some form of turbulent combustion modelling must be employed. These include steady (Di Mare et al, 2004) and unsteady (Pitsch and Steiner, 2000) flamelet models, the flamelet/progress variable (FPV) model (Pierce and Moin, 2004) and the Stochastic Fields or Eulerian Monte Carlo method (Mustata et al, 2006).…”

Section: Introductionmentioning

confidence: 99%