Technische Universität München Tackling Combustor Design Problems with Large Eddy Simulation of Reacting Flows Wolfgang Polifke Fachgebiet für Thermodynamik Technische Universität München Acknowledgements: Joao Carneiro, Patrick Dems, Stephan Föller, Thomas Komarek, Rohit Kulkarni, Luis Tay, Matthieu Zellhuber AG Turbo, Alstom, DFG, DST, KW21, Siemens MUSAF II Colloquium Sep. 18-20, 2013, CERFACS, Toulouse
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Technische Universität München
Tackling Combustor Design Problems with Large Eddy Simulation of Reacting Flows
Wolfgang PolifkeFachgebiet für ThermodynamikTechnische Universität München
Acknowledgements:Joao Carneiro, Patrick Dems, Stephan Föller, Thomas Komarek, Rohit Kulkarni, Luis Tay, Matthieu Zellhuber
AG Turbo, Alstom, DFG, DST, KW21, Siemens
MUSAF II ColloquiumSep. 18-20, 2013, CERFACS, Toulouse
Technische Universität München
W. Polifke - MUSAF II, Sep. 2013
Overview
Gas turbine combustor design challenges
• stability
• emissions
This talk
• mixing and auto-ignition in turbulent flow
• flame dynamics from system identification
• spray dispersion, evaporation & combustion
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control & optimization,
c
ode couplingreacting flo
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multi-physis, multi-scale
Technische Universität München
W. Polifke - MUSAF II, Sep. 2013
Sequential combustion in Alstom GT24/26
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multi-stream mixing in swirling, turbulent flow
auto-ignition & flame propagation
Technische Universität München
W. Polifke - MUSAF II, Sep. 2013
Composite PV lookup from PSRs
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Autoignition tabulation (0D reactors):!
Tabulated Chemistry Concept!
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Tabulated Chemistry Concept!
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Technische Universität München
W. Polifke - MUSAF II, Sep. 2013
Stochastic fields for subgrid scale fluctuations
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Technische Universität München!
Turbulence-Chemistry Interaction models!
Presumed PDF! Transported PDF!
Deterministic transport equations! Stochastic partial differential equations!
Tychonov Regularization for inversion of Wiener Filter:
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Generation of optimal excitation signals:
Technische Universität München
W. Polifke - MUSAF II, Sep. 2013
Advanced SI for low signal-to-noise
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maximumentropy
non-Gaussiansimulation
Föller & Polifke, ICSV ’11:Transmission and reflectionof sound at duct discontinuity
Technische Universität München
W. Polifke - MUSAF II, Sep. 2013
Aero-acoustic scattering at an orifice
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input to excite acoustic eigenmodes of the pipe network. If the acoustic lossesare weaker than the acoustic gain provided by the orifice the eigenmode willgrow rapidly and the system becomes acoustically unstable.
Due to the high amplification potential and the regular appearance in pipenetworks, orifices were studied by several research groups. Experimentally,the scattering coefficients of cylindrical orifices with different diameters andthicknesses were determined and analyzed by Testut et al. [TAMH09]. In com-parison to experimental studies, orifices were investigated more frequently byresearches with different numerical approaches. Kirkegaard et al. [KAEÅ12]applied the linearized Navier-Stokes equations to solve for the scattering coef-ficients of a 2-dimensional orifice configuration. Rupp et al. [RCS10] analyzednumerically the aero-acoustic interactions in the vicinity of an orifice geom-etry based on unsteady 3-dimensional Navier-Stokes simulations. In previ-ous years, results for the scattering coefficients and for the whistling crite-rion [AS99] of the here introduced geometry were already published by La-combe et al. [LMF+10, Lac11, LFJ+13]. All these results base on the SI method-ology presented by Föller et al. in 2012 [FP12] where a FIR model structurewithout individual time lag adaption was employed.
The aero-acoustical network element representation of the orifice configu-ration is shown in Fig. 6.2. There are potentially two directions for incidentacoustic waves with fu as the corresponding upstream ingoing characteris-tic wave amplitude and gd as the downstream ingoing counterpart. The twooutgoing characteristic wave amplitudes are upstream gu and downstreamfd, respectively. Since the orifice configuration represents a 2x2 aero-acoustic
Figure 6.2: Acoustical network element representation of the cylindrical orifice in a pipe
MIMO system, its scattering matrix (Eq. (6.1)) agrees with the acoustic ele-
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6.3 Results
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Figure 6.5: Amplitudes of the scattering coefficients for the cylindrical orifice in a pipe vs. Srnumber; LES/SI results with 99% confidence intervals at 2 M numbers (MLES/SI =0.0252: black, MLES/SI = 0.0349: red) in comparison with experimental data of La-combe [Lac11] (Mexp = 0.026: black, Mexp = 0.0335: red)
highest model frequency of interest fmax,mod. The remaining frequency con-tent in ranges above fmax,mod in the acoustic responses gu and fd is not mod-eled and thus, causes a reduction of the prediction quality.
Comparing the results in Figs. 6.5 and 6.6 to the LES/SI results presentedin earlier publications [LMF+10, LFJ+13], methodological improvements ledto the significant better quality of the solutions. Especially, the occurrenceof wavy deviations over the entire frequency range could be successfully re-
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M = 0.026M = 0.034
Technische Universität München
W. Polifke - MUSAF II, Sep. 2013
Summary
Status Quo
• LES/SI can give flame dynamics with quantitative accuracy
Ongoing work
• optimal model structures for identification
• non-linear effects
• high frequencies, acoustic losses
• combustion noise
• LES model for (partially) premixed (spray) combustion
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Technische Universität München
W. Polifke - MUSAF II, Sep. 2013 22
Poly-Celerity MOM for polydisperse sprays
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Technische Universität München
W. Polifke - MUSAF II, Sep. 2013
Test case: sedimentation of bubbles
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2.4 Test Case
Figure 2.2: Contours of the Sauter Mean Diameter obtained with the Moments Model in Open-FOAM.
Figure (2.4) shows the evolution of the bubble size distribution function at several positionsinside the channel (corresponding to axial positions x = 1,5; 5,7 cm and vertical positions y =0,1; 10; 19,9 mm). As bubbles tend to move towards the upper side of the channel, the numberdensity is higher for the vertical coordinate corresponding to y = 19,9 mm, and smaller at y =0,1 mm. Furthermore, a very reasonable agreement can be noted between both methods, withthe Moments Model being able to reproduce not only the shape of the distribution function, butalso its variation along the channel. However, the distribution obtained with the Moments Modelnear the upper wall at the most downstream axial position in the channel deviates considerablyfrom that of the Multi-Fluid solution. This occurs because the shape of the spectral distributionat that location is dominated by the high accumulation of big bubbles near the top wall, whichis not appropriately reproduced by a Gamma distribution.
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(Carneiro et al)
Experiments (Sommerfeld & Qiu, ’91) vs. LES (Dems et al, 2012)