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An Intercomparison Exercise on the Capabilities of CFD Models
to Predict Deflagration of a Large-Scale H2-Air Mixture
in Open Atmosphere J. García, E. Gallego, E. Migoya, A. Crespo (UPM)
A. Kotchourko, J. Yañez (FZK), A. Beccantini (CEA),
O.R. Hansen (GexCon), D. Baraldi (JRC), S. Høiset (N-H),
M.M. Voort (TNO), V. Molkov (UU)
• Standard Benchmark Exercise Problems SBEPs
• Objectives: – establishing a framework for validation of
codes and models for simulation of problems relevant to hydrogen safety,
– identifying the main priority areas for the further development of the codes/models.
SBEPs in HySafe
• The experiment was performed by the Fraunhofer Institut Chemische Technologie (Fh-ICT), Germany in 1983.
• 20 m diameter polyethylene hemispheric balloon (total volume 2094 m3).• Homogeneous stoichoimetric hydrogen-air mixture.
Experiment description
• Initial conditions:– Pressure: 98.9 kPa
– Temperature: 283 K.
• Pressure dynamics was recorded using 11 transducers, installed on the ground level in a radial direction at different distances from the centre.
• The deflagration front propagation was filmed using high-speed cameras.
Experiment description
Organisations and codes participating
Participant Organisations CodesCEA, Commissariat à l’Energie Atomique, France CAST3M
FZK, Forschungszentrum Karlsruhe, Germany COM3D
GexCon, GexCon AS, Norway FLACSv8.1
JRC, Joint Research Centre, European Commission Reacflow
NH, Norsk Hydro ASA, Norway FLACSv8.0
TNO, The Netherlands AutoReaGas v3.0
UU, University of Ulster, UK FLUENTv6.1.18
Participant & Code
Turbulence model
Chemical model
CEA CAST3M
- CREBCOM combustion model
GexCon FLACS v8.1
k- standard Beta flame modelReaction rate based on one step model with burning velocity from flame-library
FZKCOM3D
k- standard CREBCOM combustion model. Adjustable parameter Cf, governing the rate of chemical
interaction and therefore a visible flame speed.
JRC Reacflow
k- standard Modified Eddy Dissipation combustion model
NH FLACS v8
k- standard Beta flame model
TNO AutoReaGas
v3.0
k- standard Combustion rate depends on the mean composition of the mixing region. Flame speed correlates via empirical relations with the calculated turbulence parameters
UU FLUENT
v6.1.18
LES (RNG) Gradient method
Models
ModelsParticipant & Code
Resolution method & discretisation scheme
GridComputer &CPU time
CEACAST3M
Operator splitting technique. First order
1D spherical domainCell size 0.1 m
Not available
GexCon FLACS v8.1
SIMPLESecond order
3D-Cartesian Cell size: 0.5 m
1 CPU PCs 0.5-4 Gb RAM Linux4h CPU
FZKCOM3D
Solver coupled with turbulence & chemical models.
3D cartesian gridCell size: 0.3 m combustion 0.59 m pressure
Cluster of 7 Athlon PC - 2 CPU each.
Linux 2.4.20.≈ 14 days /with 14 processors
JRC Reacflow
Explicit scheme Second order
3D unstructured adaptive grid 0.15 m
Linux cluster26.5 to142 h CPU
NH FLACS v8
SIMPLESecond order
3D-CartesianCell size: 0.67 m
6 days CPU (1 s experiment)
TNO AutoReaGas
SIMPLEFirst order
3D Cartesian 27000 cells
UU FLUENT
Explicit method 2nd order
3D unstructured tetrahedral grid(a): 0.4 m (b): 0.2 m
2/6 CPU 4/12 Gb RAM142/197h CPU (0.32/0.63 s
experiment)
• All experimental results were known before the calculations.
Comments about results
• The influence of the polyethylene film and wire net was supposed negligible.
• Sensors at 2, 8 and 18 m have to be influenced by combustion because they do not recover ambient pressure.
Dynamics of the averaged flame front radius with time
0
5
10
15
20
25
0.00E+00 1.00E+02 2.00E+02 3.00E+02 4.00E+02 5.00E+02 6.00E+02 7.00E+02
Time (ms)
Fla
me
fro
nt
rad
ius
(m)
CEA
FzK
Gexcon(x)
Gexcon(z)
JRC
NH
TNO
TNO-1
UU(a)
UU(b)
Experimental
Dynamics of the flame front radius with time
Pressure dynamics at R = 2m
-1.00E+04
-8.00E+03
-6.00E+03
-4.00E+03
-2.00E+03
0.00E+00
2.00E+03
4.00E+03
6.00E+03
8.00E+03
1.00E+04
0.00E+00 2.00E-01 4.00E-01 6.00E-01 8.00E-01 1.00E+00 1.20E+00
Time (s)
Rel
ativ
e P
ress
ure
(P
a)
CEA
FzK
Gexcon
JRC
NH
TNO
TNO-1
UU(a)
UU(b)
Experimental
Pressure dynamics at R= 2 m
Flame front reaches the sensor
Pressure dynamics at R = 5m
-1.20E+04
-1.00E+04
-8.00E+03
-6.00E+03
-4.00E+03
-2.00E+03
0.00E+00
2.00E+03
4.00E+03
6.00E+03
8.00E+03
1.00E+04
1.20E+04
0.00E+00 2.00E-01 4.00E-01 6.00E-01 8.00E-01 1.00E+00 1.20E+00
Time (s)
Re
lati
ve
Pre
ss
ure
(P
a)
CEA
FzK
Gexcon
JRC
NH
TNO-1
UU(a)
UU(b)
Experimental
Pressure dynamics at R= 5 m
Flame front reaches the sensor
Pressure dynamics at R = 8m
-1.00E+04
-5.00E+03
0.00E+00
5.00E+03
1.00E+04
1.50E+04
0.00E+00 2.00E-01 4.00E-01 6.00E-01 8.00E-01 1.00E+00 1.20E+00
Time (s)
Re
lati
ve
Pre
ss
ure
(P
a)
CEA
FzK
Gexcon
JRC
NH
TNO-1
UU(a)
UU(b)
Experimental
Pressure dynamics at R= 8 m
Flame front reaches the sensor
Pressure dynamics at R = 18m
-1.00E+04
-8.00E+03
-6.00E+03
-4.00E+03
-2.00E+03
0.00E+00
2.00E+03
4.00E+03
6.00E+03
8.00E+03
1.00E+04
0.00E+00 2.00E-01 4.00E-01 6.00E-01 8.00E-01 1.00E+00 1.20E+00
Time (s)
Re
lati
ve
Pre
ss
ure
(P
a)
CEA
FzK
Gexcon
JRC
NH
TNO-1
UU(a)
UU(b)
Experimental
Pressure dynamics at R= 18 m
Flame front reaches the sensor
Pressure dynamics at R = 35m
-6.00E+03
-4.00E+03
-2.00E+03
0.00E+00
2.00E+03
4.00E+03
6.00E+03
0.00E+00 2.00E-01 4.00E-01 6.00E-01 8.00E-01 1.00E+00 1.20E+00
Time (s)
Rel
ativ
e P
ress
ure
(P
a)
CEA
FzK
Gexcon
JRC
NH
TNO-1
UU(a)
UU(b)
Experimental
Pressure dynamics at R= 35 m
Pressure dynamics at R = 80m
-4.00E+03
-3.00E+03
-2.00E+03
-1.00E+03
0.00E+00
1.00E+03
2.00E+03
3.00E+03
0.00E+00 2.00E-01 4.00E-01 6.00E-01 8.00E-01 1.00E+00 1.20E+00
Time (s)
Rel
ativ
e P
ress
ure
(P
a)
FzK
Gexcon
JRC
NH
TNO-1
UU(a)
UU(b)
Experimental
Pressure dynamics at R= 80 m
• The flame velocity is reproduced quite well in most of the calculations.
• The pressure dynamics obtained numerically are in good agreement with the experiments for the positive values.
• Negative pressures are more sensitive to far field boundary condition, this can be avoided using larger domains and finer grids.
• More benchmarks will be necessary to calibrate and improve the codes.
Conclusions