2nd International Conference on Hydrogen Safety, San Sebastian, 11-13 September 2007 A.Teodorczyk, WUT
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Fast Turbulent Deflagration and DDT of Hydrogen-Air Mixtures in Small Obstructed Channels
A.Teodorczyk, P.Drobniak, A.DabkowskiWarsaw University of Technology, Poland
2nd International Conference on Hydrogen Safety, San Sebastian, 11-13 September 2007 A.Teodorczyk, WUT
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DDT simulations
V.Gamezo et al., 31st Symposium International on Combustion, Heidelberg 2006
• stoichiometric hydrogen-air mixture at 0.1 MPa
• Reactive Navier-Stokes equations with one-step Arrhenius kinetics
• 2D channel with obstacles: length = 2m; height H = 1, 2, 4, 8 cm
• Grid: 2 m (min)
2nd International Conference on Hydrogen Safety, San Sebastian, 11-13 September 2007 A.Teodorczyk, WUT
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DDT simulations
V.Gamezo et al., 31st Symposium International on Combustion, Heidelberg 2006
H2HH/2
2nd International Conference on Hydrogen Safety, San Sebastian, 11-13 September 2007 A.Teodorczyk, WUT
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DDT simulations
Source:Gamezo et al.. 21st ICDERS, July 23-27, 2007, Poitiers
2nd International Conference on Hydrogen Safety, San Sebastian, 11-13 September 2007 A.Teodorczyk, WUT
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Objectives
• Generate experimental data for the validation of CFD simulations
• Determine flame propagation regimes and velocities as a function of:
• blockage ratio
• Obstacle spacing
• Hydrogen-air mixture stoichiometry
2nd International Conference on Hydrogen Safety, San Sebastian, 11-13 September 2007 A.Teodorczyk, WUT
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Channel:Channel:
- length 2 m,
- width 0.11 m
- heigth: H = 0.08 m
Experimental study
Obstacle heigth: h = 0.0, 0.02, 0.04, 0.06 m
Blockage ratio: BR = 0.0, 0.25, 0.5, 0.75
Obstacle spacing: L = 0.08, 0.16, 0.32 m
Stoichiometry: = 0.6, 0.8, 1.0
Initial conditions: 0.1 MPa, 293 K
L Hh
2nd International Conference on Hydrogen Safety, San Sebastian, 11-13 September 2007 A.Teodorczyk, WUT
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Experimental
DiagnosticsDiagnostics (pairs)):
- 4 piezoquartz pressure transducers
- 4 ion probes
Ignition:Ignition: - weak spark plug
Data acquisition:Data acquisition:- amplifier- 8 cards (10MHz each)- computer
H = 80 mmH = 80 mm
2nd International Conference on Hydrogen Safety, San Sebastian, 11-13 September 2007 A.Teodorczyk, WUT
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Parameters of CJ Detonation
VCJ [m/s] aCP
[m/s] [mm]
0.6 1709 974 40
0.8 1866 1045 13
1.0 1971 1092 8
VCJ – detonation velocity
aCP – sound speed in combustion products
- detonation cell size
2nd International Conference on Hydrogen Safety, San Sebastian, 11-13 September 2007 A.Teodorczyk, WUT
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Results – BR = 0.25
L = 0.08 m L = 0.16 m L = 0.32 m
0.6 FD 500 m/s
FD 600 m/s
0.8 DDT FD 1000 m/s
1.0 DET 1900 m/s
DDT
FD – Fast Deflagration
DDT – Deflagration to Detonation Transition
DET - Detonation
2nd International Conference on Hydrogen Safety, San Sebastian, 11-13 September 2007 A.Teodorczyk, WUT
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Results – BR = 0.5
FD – Fast Deflagration
DDT – Deflagration to Detonation Transition
DET - Detonation
L = 0.08 m L = 0.16 m L = 0.32 m
0.6 FD650 m/s
FD600 m/s
0.8 FD900 m/s
DDT
1.0 DDT DET2000 m/s
2nd International Conference on Hydrogen Safety, San Sebastian, 11-13 September 2007 A.Teodorczyk, WUT
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Results – BR = 0.75
FD – Fast Deflagration
DDT – Deflagration to Detonation Transition
DET - Detonation
L = 0.08 m L = 0.16 m L = 0.32 m
0.6 FD550 m/s
FD500 m/s
FD500 m/s
0.8 FD600 m/s
FD650 m/s
FD900 m/s
1.0 FD700 m/s
FD700 m/s
FD950 m/s
2nd International Conference on Hydrogen Safety, San Sebastian, 11-13 September 2007 A.Teodorczyk, WUT
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Average velocity of flame (open) and pressure wave (solid) for L = 160 mm
Results – L = 0.16 m
0
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
2400
2600
2800
Ve
loci
ty (
m/s
)
1000 1200 1400 1600 1800D istance from the ignition point (m m )
P ressure transducer h=00m m
P ressure transducer h=20m m
Ion probe h=20m m
P ressure transducer h=40m m
Ion probe h=40m m
P ressure transducer h=60m m
Ion probe h=60m m
L-160m m_fi=1.0
2nd International Conference on Hydrogen Safety, San Sebastian, 11-13 September 2007 A.Teodorczyk, WUT
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Average velocity of flame (open) and pressure wave (solid) for L = 320 mm
Results – L = 0.32 m
0
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
2400
2600
2800
Ve
loci
ty
(m/s
)
1000 1200 1400 1600 1800D istance from the ignition point (m m )
P ressure transducer h=00m m
P ressure transducer h=20m m
Ion P robe h=20m m
P ressure transducer h=40m m
Ion P robe h=40m m
P ressure transducer h=60m m
Ion P robe h=60m m
L-320m m_fi=1.0
2nd International Conference on Hydrogen Safety, San Sebastian, 11-13 September 2007 A.Teodorczyk, WUT
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Results – L = 0.32 m, BR = 0.25, = 1
0
1000
2000
3000
4000
5000
Vo
lta
ge
(m
V)
0
2
4
6
8
Pre
ssu
re
(MP
a)0 0.4 0.8 1.2 1.6 2 2.4 2.8
Time (m s)
Pressure transducer
Ion probe
L320mm_h20mm_fi-1.0_exp5-01
0
1000
2000
3000
4000
5000
Vo
lta
ge
(m
V)
0
2
4
6
8
Pre
ssu
re (
MP
a)
0 0.4 0.8 1.2 1.6 2 2.4 2.8
Time (m s)
Pressure transducer
Ion probe
L320mm_h20mm_fi-1.0_exp5-02
0
1000
2000
3000
4000
5000V
olt
ag
e (
mV
)
0
2
4
6
8
Pre
ssu
re
(MP
a)
0 0.4 0.8 1.2 1.6 2 2.4 2.8
Time (m s)
Pressure transducer
Ion probe
L320mm_h20mm_fi-1.0_exp5-03
0
1000
2000
3000
4000
5000
Vo
lta
ge
(m
V)
0
2
4
6
8
Pre
ssu
re (
MP
a)
0 0.4 0.8 1.2 1.6 2 2.4 2.8Time (m s)
Pressure transducer
Ion probe
L320mm_h20mm_fi-1.0_exp5-04
P1 P2
P3 P4
2nd International Conference on Hydrogen Safety, San Sebastian, 11-13 September 2007 A.Teodorczyk, WUT
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Results – P3, L = 0.16 m, BR = 0.5
=0.8 =1.0
0
1000
2000
3000
4000
5000
Vo
lta
ge
(m
V)
0
2
4
6
8
Pre
ssu
re (
MP
a)
0 0.4 0.8 1.2 1.6 2 2.4 2.8
Time (m s)
Pressure transducer
Ion probe
L160mm_h40mm_fi-0.8_exp3-03
0
1000
2000
3000
4000
5000
Vo
lta
ge
(m
V)
0
2
4
6
8
Pre
ssu
re (
MP
a)
0 0.4 0.8 1.2 1.6 2 2.4 2.8
Time (ms)
Pressure transducer
Ion probe
L160mm_h40mm_fi-1.0_exp4-03
2nd International Conference on Hydrogen Safety, San Sebastian, 11-13 September 2007 A.Teodorczyk, WUT
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Results – P4, L = 0.16 m, BR = 0.25
=0.6 =0.8
0
1000
2000
3000
4000
5000
Vo
lta
ge
(m
V)
0
2
4
6
8
Pre
ssu
re (
MP
a)
0 0.4 0.8 1.2 1.6 2 2.4 2.8
Time (m s)
Pressure transducer
Ion probe
L160mm_h20mm_fi-0.6_exp4-04
0
1000
2000
3000
4000
5000
Vo
lta
ge
(m
V)
0
2
4
6
8
Pre
ssu
re (
MP
a)
0 0.4 0.8 1.2 1.6 2 2.4 2.8
Time (ms)
Pressure transducer
Ion probe
L160mm_h20mm_fi-0.8_exp3-04
2nd International Conference on Hydrogen Safety, San Sebastian, 11-13 September 2007 A.Teodorczyk, WUT
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Run-up distance for DDT
S.Dorofeev
In tubes at 0.1 MPa, H2-air
600
800
1000
1200
1400
1600
1800
2000
2200
odle
głoś
ć od
pun
ktu
zapł
onu
[m
m]
0.2 0.4 0.6 0.8
BR
L=320m m _fi=1.0
L=320m m _fi=0.8
L=160m m _fi=1.0
L=160m m _fi=0.8
L=160m m _fi=0.6
In our channel
2nd International Conference on Hydrogen Safety, San Sebastian, 11-13 September 2007 A.Teodorczyk, WUT
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DDT limits
BR L = 0.08 m L = 0.16 m L = 0.32 m
0.25 0.48 m 0.8 m
0.5 0.24 m 0.4 m
0.75 0.107 m 0.16 m 0.2 m
7chL
Characteristic dimension:
1
1LLch
21
HLL
H
hH
Lch for the present study
Dorofeev criterion for DDT:
7
0.6 0.28 m
0.8 0.091 m
1.0 0.056 m
2nd International Conference on Hydrogen Safety, San Sebastian, 11-13 September 2007 A.Teodorczyk, WUT
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DDT limits in obstructed channels (H2-air)
S.Dorofeev
w – our studies
L320mm
w4 - h40mm, Ø-1.0
w5 - h40mm, Ø-0.8
w7 - h20mm, Ø-1.0
L160mm
w13 - h40mm, Ø-1.0
w16 - h20mm, Ø-1.0
w17 - h20mm, Ø-0.8
2nd International Conference on Hydrogen Safety, San Sebastian, 11-13 September 2007 A.Teodorczyk, WUT
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• Obstacles giving high channel blockage ratio are destructive for the flame propagation (large momentum losses) and regardless turbulizing effect they decrease hazard of DDT
• The importance of blockage ratio changes with the obstacle density. The higher blockage ratio the larger is optimum obstacle separation distance resulting in highest hazard for DDT.
• The obstacle density is less important for the lean mixtures ( = 0.6) for which no detonation was observed in the experiments.
• The predictions were found to be in general agreement with the correlation developed by Dorofeev et al.
• Advanced simulations show DDT very well qualitatively but still are not able to predict it quantitatively (transition distance ?, transition probability?)
Conclusions
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