Simulating expanding flame kernels and turbulent jet flames with

Simulating expanding flame kernels and turbulent
jet flames with tabulated chemistry
C. Gruselle, F. Pecquery, V. Moureau, D. Taieb, G. Lartigue,
P. Domingo, L. Vervisch, G. Ribert, Y. D’Angelo
CNRS-CORIA, UMR 6614, Rouen
http://www.coria-cfd.fr
V. Moureau, CORIA
CNRS – UNIVERSITE et INSA de Rouen
1
The tabulated chemistry approach
 The basic notion of flamelet dates back to the Eighties (Bradley et
al 1988). In such a flamelet, a few parameters are sufficient to
describe the slowly evolving species and temperature
 FPI (Gicquel 2000) and FGM (Van Oijen 2002) methods are recent
models based on the tabulation of premixed flamelets
 These approaches became widely used in the latest decade
•  A Google query on “tabulated chemistry approach”: 2.8 million pages…
V. Moureau, CORIA
CNRS – UNIVERSITE et INSA de Rouen
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Some applications of tabulated chemistry
 Tabulated chemistry is well suited for 2-inlets
applications: aeronautical burners, some furnaces, …
industrial
Aeronautical burner, YALES2 code
160 million tets, 4096 cores
D. Taieb
V. Moureau, CORIA
CNRS – UNIVERSITE et INSA de Rouen
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YALES2
www.coria.cfd.fr
 YALES2 is an unstructured low-Mach number code for the
DNS and LES of reacting two-phase flows in complex geometries.
It solves the unsteady 3D Navier-Stokes equations. It is used by
more than 60 people in labs and in the industry.
PRECCINSTA Burner
2.6 billion cells, 16384 cores of BG/P
Moureau et al, Comb. Flame, 2011
V. Moureau, CORIA
T7.2 turbine blade
1.6 billion cells, 8192 cores of Curie
Maheu et al, THMT conference, 2012
CNRS – UNIVERSITE et INSA de Rouen
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Outline
 Context
 Modeling of flame kernel expansion in a stratified mixture
 Modeling of the SANDIA D flame with tabulated chemistry
 Conclusions
V. Moureau, CORIA
CNRS – UNIVERSITE et INSA de Rouen
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Modeling of flame kernel expansion in a
stratified mixture
C. Gruselle, V. Moureau, Y. D’Angelo, F. Ravet
V. Moureau, CORIA
CNRS – UNIVERSITE et INSA de Rouen
6
Context
 In direct injection gasoline engines,
stratified combustion brings some
interesting features
•  Improves the ignition performances and
the stability
•  Reduces the pollutant emissions (NOx)
 However, the flame propagation is
affected by the mixture stratification
and by Exhaust Gas Recirculation
(EGR) and Internal Gas Recirculation
(IGR)
 Some fundamental studies are still
required to understand and predict
the flame propagation in these
conditions
V. Moureau, CORIA
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The stratified combustion experiment at CORIA
 Injection of a rich stream in a lean mixture (S. Balusamy, B.
Lecordier, A. Cessou)
Initial equivalence
ratio
ΦCh =0,6
Equivalence ratio
of the injection
Φinj =10,0
Injected quantity
6,5 cm3
Injection time
52 ms
Ignition time
5 ms
 Flame propagation study
•  Local equivalence ratio measurements
•  Local flame speed measurements
•  Mean and instantaneous flame positions
Saravanan BALUSAMY, 2010, PhD Thesis
V. Moureau, CORIA
CNRS – UNIVERSITE et INSA de Rouen
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Large-Eddy Simulation parameters
 Calculations performed on Babel, Blue Gene P at IDRIS, with the
YALES2 code
Element
Resolution
count (tets)
Points in the
flame front
Number of
cores
Injection
= 52 ms
Combustion
= 5 ms
38 millions
106 µm
4
256
22h
8h45
304 millions
50 µm
8
2048-4096
45h30
22h30
•  The fine mesh provides a good resolution of the flow
•  Refined in the visualization window
LES
V. Moureau, CORIA
CNRS – UNIVERSITE et INSA de Rouen
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Tabulated chemistry parameters
 PCM-FPI approach (Gicquel 2000, Domingo 2008)
 Jerzembeck 2009 mechanism
 Progress variable: YC = YCO + YCO2 +YH2O
 Fitting of the Schmidt number of the progress variable (Sc=0.72)
 Mixture fraction
•  Z = 1 in the injected stream
•  Z = 0 in the z_0.07748
chamber
3000
2500
Yc=Yco+Yco2
Yc=Yco+Yco2+Yh2o
T (K)
2000
1500
1000
500
0V.
0
Moureau, CORIA
0.1
0.2
Yc
0.3
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Unsteady injection simulation
 Inlet velocity profile
 Calculation of the injected equivalence ratio
•  Equivalence ratio in the injection system before injection: Φ=0.6
•  Injected equivalence ratio: Φ=10
•  Effective injected equivalence ratio: Φeq = 7.6
 Turbulence: Localized Dynamic Smagorinsky
•  Turbulence injection: u’ = 1 m/s
•  Integral length scale was fitted to get the correct jet penetration
Exp.
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LES-300M
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Fields before ignition
 Good reproduction of the jet angle and stratification
LES-38M
Exp.
LES-300M
Exp.
LES-300M
Exp.
LES-38M
Exp.
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Ignition sequence
 Velocity field and flame front position
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Flame propagation
 Instantaneous flame front position at 5 ms
Exp.
LES-300M
 Mean flame front positions
Exp.
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LES-300M (6 sim., 12 planes)
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Flame speed measurement with a level set method
 The level set method is used to track a progress variable contour
 First step:
•  Computation of the normals to the iso-C level
•  Calculation of the distance to the iso-C level
•  Storing of the density in the domain ρ1
 Second step:
•  Calculation of the absolute flame speed
•  Calculation of the local velocity
•  Calculation of the displacement speed in the fresh gases taking into account
the local density change (Poinsot, Veynante)
V. Moureau, CORIA
CNRS – UNIVERSITE et INSA de Rouen
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Flame speed measurement in the LES
 Comparison of the displacement speed in the fresh gases with the
laminar flame speed given by the premixed flamelets
 Sl overshoots occur at some flame crests
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CNRS – UNIVERSITE et INSA de Rouen
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Probability Density Functions
 PDF of the flame speed in a plane as a function of Z
•  Almost a symmetric profile around the peak
•  Flame speed is more important at ignition because ignition occurs in the rich
zone
Exp.
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LES
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Partial conclusions
 Tabulated chemistry seems to reproduce some of the features of
flame propagation in a stratified mixture
 Many questions remain
•  Flame curvature effects in tabulated chemistry (Markstein length)
•  History effects (Balusamy et al)
•  How to take into account the EGR and IGR effects ?
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CNRS – UNIVERSITE et INSA de Rouen
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Modeling of the SANDIA D flame with tabulated
chemistry
F. Pecquery, V. Moureau, L. Vervisch, A. Roux
V. Moureau, CORIA
CNRS – UNIVERSITE et INSA de Rouen
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Motivation
 Our main objective in this study is to validate NOx models before
using them for aeronautical burners
 The SANDIA D Flame (Masri 1996, Barlow et al 1998) is a wellvalidated and well-known academic flame
 Several studies with tabulated chemistry have been performed with
RANS (Fiorina 2008, Vervisch 2004, …) and LES
 For LES, non-premixed and premixed flamelets have been used
•  Vreman 2008, Godel 2009, Pitsch, Zoller et al 2011, …
V. Moureau, CORIA
CNRS – UNIVERSITE et INSA de Rouen
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The issue of Lewis number in tabulated chemistry
0.4
 To derive
a unique mixture fraction from species mass fractions,
which is able to describe the mixing of species
and enthalpy
Complex model
Unity Lewis numbers
Sl (m.s-1)
0.3
 The 0.2
Lewis number of all species must be unity
0.1
 However, to get the correct flame speed for a premixed flame, the
Lewis number of the species must be different
0
0
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0.2
0.4
0.6
Z (from the SANDIA D flame)
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0.8
1
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Large-Eddy Simulation parameters
 Code: in-house YALES2 code
 8192 cores of Curie (mesh M2)
 Computational cases
•  PCM-FPI model with GRI Mech 3.0
•  Transported variances (Domingo et al 2008)
•  Localized dynamic Smagorinsky model
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CNRS – UNIVERSITE et INSA de Rouen
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Flame topology
 Instantaneous fields of case 3 (M2 mesh with 350M tets, Le_k=1)
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CNRS – UNIVERSITE et INSA de Rouen
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Statistics
 Mixture fraction on the axis
Black: Le_k=1
Red: Le_k≠1
Continuous line: mesh M2
Dashed line: mesh M1
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CNRS – UNIVERSITE et INSA de Rouen
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Statistics
 Radial profiles of the mixture fraction (M2 mesh)
Black: Le_k=1
Red: Le_k≠1
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CNRS – UNIVERSITE et INSA de Rouen
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Statistics
 Temperature on the axis
Black: Le_k=1
Red: Le_k≠1
Continuous line: mesh M2
Dashed line: mesh M1
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CNRS – UNIVERSITE et INSA de Rouen
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Statistics
 Radial profiles of temperature (M2 mesh)
Black: Le_k=1
Red: Le_k≠1
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CNRS – UNIVERSITE et INSA de Rouen
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Statistics
 NO mass fraction on the axis
Black: Le_k=1
Red: Le_k≠1
Continuous line: mesh M2
Dashed line: mesh M1
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CNRS – UNIVERSITE et INSA de Rouen
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Statistics
 Radial profiles of NO mass fraction (M2 mesh)
Black: Le_k=1
Red: Le_k≠1
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Combustion regimes
 Instantaneous source term from the 350M mesh with Lek=1
 Both rich premixed and non-premixed flame fronts are visible
c=0.8, Takeno = -1
c=0.8, Takeno = 1
z=z_st
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CNRS – UNIVERSITE et INSA de Rouen
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Combustion regimes
 The 0.4
Lewis number changes slightly the flame structure but rich
premixed and non-premixed flames are visible
in both cases
Complex model
Unity Lewis numbers
Sl (m.s-1)
Lek=1
0.3
0.2
Black: Z=Zst
Lek≠1
0.1
0
0
V. Moureau, CORIA
0.2
0.4
0.6
Z (from the SANDIA D flame)
CNRS – UNIVERSITE et INSA de Rouen
0.8
1
31
Conclusions
V. Moureau, CORIA
CNRS – UNIVERSITE et INSA de Rouen
32
Conclusions & Perspectives
 Tabulated chemistry is a valuable tool for turbulent flame modeling
 Many questions remain: curvature effects, history effects, accuracy
of the flame speed for rich mixtures, …
 The non-orthogonality of C and Z gradients is clearly visible in many
configurations, which is the basic assumption of many models
C=0.7
V. Moureau, CORIA
PRECCINSTA burner
Partially-premixed regime
CNRS – UNIVERSITE et INSA de Rouen12 billion cells, 16384 cores
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References & Acknowledgements
 References
•  Gruselle, C., Moureau, V., D’Angelo, Y., « Numerical simulation of turbulent
stratified flame propagation in a closed vessel », THMT conference, 2012,
Palermo, Italy.
•  Pecquery, F., Moureau, V., Lartigue, G., Vervisch, L., Roux, A., « Development
of a numerical model to predict emissions of nitric oxides in turbulent
flames », ETMM9 conference, 2012, Thessaloniki, Greece.
•  Moureau, V., Domingo, P., and Vervisch, L., "From Large-Eddy Simulation to
Direct Numerical Simulation of a lean premixed swirl flame: Filtered Laminar
Flame-PDF modelling", Comb. and Flame, 2011, 158, 1340–1357.
•  Moureau, V., Domingo, P., and Vervisch, L., "Design of a massively parallel
CFD code for complex geometries", Comptes Rendus Mécanique, 2011, 339
(2-3), 141-148.
 Acknowledgements
•  D. Taieb, G. Lartigue, P. Domingo, L. Vervisch, Y. D’Angelo
•  PhD students: C. Gruselle, F. Pecquery, …
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CNRS – UNIVERSITE et INSA de Rouen
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