H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton1
Course of explosions in Propene/O2/N2 and Methane/O2/N2mixtures in vessels of 20 l to 2500 l
and load on the walls
Dr. Hans-Peter SchildbergBASF-AG
GCT/S - L511D-67056 Ludwigshafen
Email: [email protected]: +49 621 60-56049
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 2
Outline of talk
Explosion characteristics
Introduction
Course of explosion in 20 l sphere
Comparison: detonative regimesin 20 l vessels ↔ 100, 500, 2500 l vessels
Predetonation distances of Propene/O2 in tubes
Pressure load Pdet on the wall of the vessel- quantification of Pdet for four scenarios occuring in a pipe (no precompression)- quantification of Pdet for four scenarios occuring in a pipe (with precompression)- quantification of Pdet for Propene/O2/N2 in vessel at Pinitial = 5 bar abs, Tinitial = 20 °C
Did ignition source directly trigger a spherical detonation?
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 3
Information available in literature on explosive gas mixtures of type combustible/O2/N2
Explosion characteristics(explosion limits, pex, (dp/dt)ex)
Course of explosion(deflagrative, detonative, heat explosion)
=> Much work needed to better understand combustible/air/O2 mixtures
- -- -pex, (dp/dt)ex
- -oexplosion limitscombustible / air /O2
-+pex, (dp/dt)ex
o+ +explosion limitscombustible / air /N2
pinitial > 1 barapinitial ≤ 1 bara
- -- -vessel (L/D ≅ 1)
- --pipe (L/D > 100)combustible / air /O2
- -+vessel (L/D ≅ 1)
++ +pipe (L/D > 100)combustible / air /N2
pinitial > 1 barapinitial ≤ 1 bara 0 10 20 30 40 50 60 70 80 90 100combustible [vol.-%]
0
10
20
30
40
50
60
70
80
90
100
O2
[vol.-%]
0
10
20
30
40
50
60
70
80
90
100
N 2[v
ol.-%
]
combustible/air mixtures
0 10 20 30 40 50 60 70 80 90 100combustible [vol.-%]
0
10
20
30
40
50
60
70
80
90
100
O2
[vol.-%]
0
10
20
30
40
50
60
70
80
90
100
N 2[v
ol.-%
]
combustible/air mixtures
explosive range ofcombustible/air/N2
explosive range ofcombustible/air/O2
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 4
Motivation for this work
Trend in partial oxidation reactions:
Advantages:- increase of yield in space and time
- lower operating pressures
Critical Issue when dealing with combustible/air/O2-mixtures: Process Safety
- course of explosion (deflagration, detonation)
- explosion characteristics- vessel-like geometry
- bubble column geometry (explosive gaseous bubbles dispersed in liquid)
- course of explosion (deflagration, detonation)
- mechanisms of flame propagation
- replacing air or diluted air as oxidant by oxygen enriched air or by pure oxygen
Focus of this work
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 5
Gaseous mixtures investigated
Propene / O2 / N2,
Methane / O2 / N2
Cyclohexane / NO2
Cyclohexane / NO
Cyclohexane / N2O
Hydrogen / O2
very detailed exp. investigations
only for one value of Pinitial and Tinitial
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 6
Explosion characteristics
Introduction
Course of explosion in 20 l sphere
Comparison: detonative regimesin 20 l vessels ↔ 100, 500, 2500 l vessels
Predetonation distances of Propene/O2 in tubes
Pressure load Pdet on the wall of the vessel- quantification of Pdet for four scenarios occuring in a pipe (no precompression)- quantification of Pdet for four scenarios occuring in a pipe (with precompression)- quantification of Pdet for Propene/O2/N2 in vessel at Pinitial = 5 bar abs, Tinitial = 20 °C
Did ignition source directly trigger a spherical detonation?
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 7
Experimental setup
20 l sphere, Pmax=600 bar, Tmax=500°CTest vessel:20 l sphere
Ignition source:exploding wire according to EN1839,Bomb method, section 4.2.3.3.3(arc discharge, ca. 200 A over ca. 3 ms)
Ignition energy:ca. 20 J
Mixture preparation:partial pressure method, ideal gas characteristics assumed
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 8
References for complete documentation of explosion characteristics
H.P. Schildberg in deliverables no. 8 and no. 13 of EU-Research Project SAFEKINEX, Contract No. EVG1-CT-2002-00072; download possible from www.safekinex.org
“Explosion characteristics of Propene/O2/N2 at 1, 5, 10 and 30 bar abs, 25 °C and 200 °C”,Hans-Peter Schildberg in „Process Safety and Industrial Explosion Protection“,editor: ESMG – European Safety Management Group e. V. , Hamm, Germany (2005), ISBN 3-9807567-4-2 (proceedings of the International ESMG Symposium 2005 in Nürnberg, Germany, 32 pages )
“Determination of the Explosion Behaviour of Methane and Propene in Air or Oxygen at Standard and Elevated Conditions”, A.A. Pekalski, H.-P. Schildberg, P.S.D. Smallegange, S.M. Lemkowitz, J.F. Zevenbergen, M. Braithwaite, H.J. Pasman, 11th International Symposium Loss Prevention and Safety Promotion in the Process Industries (2004), Praha Congress Centre 31st May-3rd June 2004;Thematic Section B, page 2118-2138 (ISBN 80-02-01574-6)
“Determination of the Explosion Behaviour of Methane and Propene in Air or Oxygen at Standard and Elevated Conditions”, A.A. Pekalski, H.-P. Schildberg, P.S.D. Smallegange, S.M. Lemkowitz, J.F. Zevenbergen, M. Braithwaite, H.J. Pasman, Process Safety and Environmental Protection, Volume 83, issue B5, 421-429 (2005)
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 9
Explosion characteristics
Introduction
Course of explosion in 20 l sphere
Comparison: detonative regimesin 20 l vessels ↔ 100, 500, 2500 l vessels
Predetonation distances of Propene/O2 in tubes
Pressure load Pdet on the wall of the vessel- quantification of Pdet for four scenarios occuring in a pipe (no precompression)- quantification of Pdet for four scenarios occuring in a pipe (with precompression)- quantification of Pdet for Propene/O2/N2 in vessel at Pinitial = 5 bar abs, Tinitial = 20 °C
Did ignition source directly trigger a spherical detonation?
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 10
Questions to be raised when considering explosions of combustible/air/O2 mixtures in vessel-like geometry
What compositions will undergo a transition from Deflagration to Detonation (DDT) after ignition with a thermal ignition source?
What is the largest conceivable pressure load on the vessel wall?
Will combustible/air mixtures remain deflagrative for higher values of Tinitial and Pinitial?
How about the „obscure“ effects reported mostly only in non-publiccommunication?
(Vessels believed to be explosion pressure proof did sometimesrupture, but when repeating the experiment at same initial pressurewith even the worst case mixture (i.e. what one believed to be worstcase), a mechanically identical vessel did withstand the load).
How does the volume of the vessel affect the detonative range?
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 11
Literature data on deflagrative and potentially detonativeexplosion regime of n-Butane/O2/N2 at 1 bar abs, 20 °C
0 10 20 30 40 50 60 70 80 90 100n-Butane [Vol.-%]
10
20
30
40
50
60
70
80
90
100
O2 [Vol.-%
]
0
10
20
30
40
50
60
70
80
90
100
N 2 [V
ol.-%
]
binary mixture n-Butane/air
stoich
iomet
ric ra
tio n-
Buta
ne : O
2 = 1
: 6.5
0
range of
deflagrative explosionrange
of m
ixture
s, whe
re
trans
ition f
rom de
flagra
tive t
o
deton
ative
explo
sion i
s pos
sible
Characteristic values of the explosive range [1]:
Lower explosion limit in air: 1.4 vol.-% Upper explosion limit in air: 9.4 vol.-%
Lower detonation limit in air: 1.98 vol.-%Upper detonation limit in air: 6.18 vol.-%
Lower detonation limit in O2: 2.05 vol.-%Upper detonation limit in O2: 38 vol.-%
Upper explosion limit in O2: 51 vol.-% Lower explosion limit in O2: 1.4 vol.-%
Characteristic values of the potentially detonative range [2,3]:
Limiting oxygen concentration: 9.4 vol.-%
[1] E. Brandes and W. Möller, Sicherheitstechnische Kenngrößen - Band 1: Brennbare Flüssigkeiten und Gase, Wirtschaftsverlag NW, Bremerhaven (2003), ISBN: 3-89701-745-8; UEL in O2 is an estimate, basis is measured value of 56 Vol-% at 200 °C, ZET-report no. 197.0390.3N
[3] M. A. Nettleton in Gaseous Detonations, p. 76, Chapman and Hall Ltd, New York (1987)
[2] M. A. Nettleton, Fire Prev. Sci. and Tech. No 23, p.29 (1980)
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 12
What does „potentially detonative regime“ mean?
If a mixture lies outside the potentially detonative regime, an explosionwill under all circumstances (e.g. type of ignition source, geometry) only bedeflagrative
If the mixture lies inside the potentially detonative regime and a thermal*ignition source triggers an explosion, the flame front will initially propagateas deflagration and the transition to detonation (DDT) will not necessarilyoccur!
There are further conditions that have to be fullfilled to enable the DDT (e. g. geometry of the containment must support flame acceleration). However, in practical applications it is mostly hard to assess to which degreethese conditions are satisfied. There are absolutely no simulation tools (e.g. reactive CFD codes) availablewhich could predict the DDT in vessels at least to some rudimentary extent.
*: in process plants almost all ignition sources are thermal. The initial stage of the explosion theycan trigger is always deflagrative
If the mixture lies inside the potentially detonative regime and a detonative ignition source triggers an explosion, the flame front will propagate as detonation right from the beginning
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 13
Literature data on deflagrative and potentially detonativeexplosion regime of Propen/O2/N2 at 1 bar abs, 20 °C
Characteristic values of the explosive range [1,2]:
Lower explosion limit in air: 2 vol.-% Upper explosion limit in air: 11 vol.-%
Lower detonation limit in air: 3.55 vol.-%Upper detonation limit in air: 10.4 vol.-%
Lower detonation limit in O2: 2.50 vol.-%Upper detonation limit in O2: 50 vol.-%
Upper explosion limit in O2: 58 vol.-% Lower explosion limit in O2: 2 vol.-%
Characteristic values of the potentially detonative range [3]:
Limiting oxygen concentration: 11.5 vol.-%
[1] E. Brandes and W. Möller, Sicherheitstechnische Kenngrößen - Band 1: Brennbare Flüssigkeiten und Gase, Wirtschaftsverlag NW, Bremerhaven (2003), ISBN: 3-89701-745-8;
[3] M. A. Nettleton in Gaseous Detonations, p. 76, Chapman and Hall Ltd, New York (1987)
[2] H.P. Schildberg in „Process Safety and Industrial Explosion Protection“, editor: ESMG European Safety Management Group e. V. , Hamm, Germany (2005), ISBN 3-9807567-4-2 (proceedings of the International ESMG Symposium 2005 in Nürnberg, Germany, 32 pages )
0 10 20 30 40 50 60 70 80 90 100Propene [Vol.-%]
10
20
30
40
50
60
70
80
90
100
O2 [Vol.-%
]
0
10
20
30
40
50
60
70
80
90
100
N 2 [V
ol.-%
]
binary mixture Propene/air
stoich
iometr
ic ra
tio P
rope
ne : O
2 = 1
: 4.5
0
range of
deflagrative explosion
range o
f mixt
ures,
where
transiti
on fro
m deflag
rative
to
detona
tive e
xplosio
n is po
ssible
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 14
Literature data on deflagrative and potentially detonativeexplosion regime of H2/O2/N2 at 1 bar abs, 20 °C
0 10 20 30 40 50 60 70 80 90 100H2 [Vol.-%]
10
20
30
40
50
60
70
80
90
100
O2 [Vol.-%
]
0
10
20
30
40
50
60
70
80
90
100
N 2 [V
ol.-%
]
binary mixture H2/air
stoichiometric ratio H2:O2 = 2:1
0
ra
nge
of
defla
grat
ive e
xplo
sion
range of mixtures, wheretransition from deflagrative to
detonative explosion is possible
Characteristic values of the explosive range [1,2]:
Lower explosion limit in air: 4 vol.-% Upper explosion limit in air: 77 vol.-%
Lower detonation limit in air: 18.3 vol.-%Upper detonation limit in air: 58.9 vol.-%
Lower detonation limit in O2: 15 vol.-%Upper detonation limit in O2: 90 vol.-%
Upper explosion limit in O2: 95.2 vol.-% Lower explosion limit in O2: 4 vol.-%
Characteristic values of the potentially detonative range [3]:
Limiting oxygen concentration: 4.3 vol.-%
[1] E. Brandes and W. Möller, Sicherheitstechnische Kenngrößen - Band 1: Brennbare Flüssigkeiten und Gase, Wirtschaftsverlag NW, Bremerhaven (2003), ISBN: 3-89701-745-8
[3] M. A. Nettleton in Gaseous Detonations, p. 76, Chapman and Hall Ltd, New York (1987)
[2] V. Schröder in „Process Safety and Industrial Explosion Protection“, editor: ESMG European Safety Management Group e. V. , Hamm, Germany (2005), ISBN 3-9807567-4-2 (proceedings of the International ESMG Symposium 2005 in Nürnberg, Germany)
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 15
Experimental setup to determine the potentiallydetonative range of explosive gas mixtures
location of thermal ignition source forbooster mixture
Signals of pressure and/or flame sensors give evidence whether a stable detonation could be
triggered in the mixture
„Booster-mixture“, Acetylene/O2, stoichiometric with respect to formation of CO and H2O. It transits to detonation after a few millimeters and acts upon the mixture to be tested with a stronger detonation front than the one that occurs in the mixture whenit undergoes a detontive explosion
mixture to be tested for potential detonability (i.e. ability to propagate a detonation which was onceinitiated either by an external source or by an initially deflagrative explosion in the mixture to be tested, which succeeded in running up to a detonation)
thin membrane or nothing(after injecting the mixtureto be tested the boostermixture is injected close to the ignition source and propagates almost as plugflow into the pipe)
Note:Pipe must be long enough for to allow that the initial state of the overdriven detonation canpass over to a stable final state, which can be either a stable detonation or a deflagration in the mixture to be tested.
ca. 15*pipe diameters
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 16
Different explosion regimes (deflagration, heat explosion, detonation) found for Propene/O2/N2 in a 20 l sphere at 5 bar abs, 25 °C
yellow range:possibly heat explosion
0 10 20 30 40 50 60 70 80 90 100Propene C3H6 [Vol.-%]
0
10
20
30
40
50
60
70
80
90
100
O2 [Vol.-%
]
0
10
20
30
40
50
60
70
80
90
100
N 2 [V
ol.-%
]
range of deflagrative explosion, 5 bar abs, 25 °C
range of detonative
explosion
stoich
iometric C 3H 6 +
1.5 O 2 -> 3 CO + 3 H 2
stoich
iometr
ic C 3H
6 + 3
O 2 -> 3
CO + 3 H 2O
stoich
iometr
ic C 3H
6 +
4.5 O
2 ->
3 CO 2 +
3 H 2O
soot is formed here
(43 vol.-% up to 69 vol.-%
)
propene/air-mixtures
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 17
Different explosion regimes (deflagration, heat explosion, detonation) of Propene/O2/N2 in a 20 l sphere at Pinitial = 1, 5 and 10 bar abs, 25 °C
0 10 20 30 40 50 60 70 80 90 100Propene C3H6 [Vol.-%]
0
10
20
30
40
50
60
70
80
90
100
O2 [Vol.-%
]
0
10
20
30
40
50
60
70
80
90
100
N 2 [V
ol.-%
]
propene/air-mixtures
range of deflagrative explosion, 1 bar abs, 25 °C
yellow range:possibly heat explosion
range of detonative
explosion
stoichiometric
C 3H 6 + 1.5 O 2 -
> 3 CO + 3 H 2sto
ichiom
etric
C 3H6 +
3 O 2 -
> 3 CO + 3
H 2O
stoich
iometr
ic C 3H
6 + 4.
5 O2 ->
3 CO 2 +
3 H 2O
yellow range:possibly heat explosion
0 10 20 30 40 50 60 70 80 90 100Propene C3H6 [Vol.-%]
0
10
20
30
40
50
60
70
80
90
100
O2 [Vol.-%
]
0
10
20
30
40
50
60
70
80
90
100
N 2 [V
ol.-%
]
range of deflagrative explosion, 5 bar abs, 25 °C
range of detonative
explosion
stoichiometric
C 3H 6 + 1.5 O 2 -
> 3 CO + 3 H 2
stoich
iometr
ic C 3H
6 + 3
O 2 -> 3
CO + 3 H 2O
stoich
iometr
ic C 3H
6 +
4.5 O 2
-> 3
CO 2 + 3
H 2O
soot is formed here
(43 vol.-% up to 69 vol.-%
)
propene/air-mixtures
propene/air-mixtures
0 10 20 30 40 50 60 70 80 90 1000
10
20
30
40
50
60
70
80
90
1000
10
20
30
40
50
60
70
80
90
100
Propene C3H6 [Vol.-%]
N 2 [V
ol.-%
]
O2 [Vol.-%
]stoich
iometr
ic ra
tio P
ropen
e : O 2
= 1 :
4.5
range of deflagrative explosion, 10 bar abs, 25 °C
yellow range:possibly heat explosion
range of detonative
explosion
(boundary at propene
conc. > 10 vol.-% only
estimated)
1 bar abs 5 bar abs
10 bar abs 30 bar abs
(Heat explosion range and detonative range were notdetermined. It might bethat the detonative rangeeven extends down to theair line)
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 18
Different explosion regimes (deflagration, heat explosion, detonation) of Propene/O2/N2 in a 20 l sphere at 1, 5 and 10 bar abs, 200 °C
0 10 20 30 40 50 60 70 80 90 1000
10
20
30
40
50
60
70
80
90
1000
10
20
60
70
90
100
Propene C3H6 [Vol.-%]
N 2 [V
ol.-%
] O2 [Vol.-%
]
yellow range:possibly heat explosion
80
50
30
40
stoichiometric C 3H 6 +
1.5 O 2 -> 3 CO + 3 H 2
stoich
iometr
ic C 3H
6 + 3
O 2 -> 3
CO + 3 H 2O
stoich
iometr
ic C 3
H 6 + 4.
5 O2 -
> 3 C
O 2 +
3 H 2
O
propene/air-mixtures
r
ange of
deflagrative explosion,
5 bar abs, 200 °C
range of detonative explosion
yellow range:possibly heat explosion
0 10 20 30 40 50 60 70 80 90 1000
10
20
30
40
50
60
70
80
90
1000
10
30
40
100
Propene C3H6 [Vol.-%]
N 2 [V
ol.-%
] O2 [Vol.-%
]stoich
iometric C 3H 6 +
1.5 O 2 -> 3 CO + 3 H 2
stoich
iometr
ic C 3H
6 + 3
O 2 -> 3
CO + 3 H 2O
stoich
iometr
ic C 3H
6 +
4.5 O 2
-> 3
CO 2 + 3
H 2O
range of deflagrative explosion, 5 bar abs, 200 °C
range of detonative
explosion
soot is formed here
(41 vol.-% up to 75 vol.-%
)
propene/air-mixtures
90
50
60
70
80
20
0 10 20 30 40 50 60 70 80 90 1000
10
20
30
40
50
60
70
80
90
1000
10
30
40
100
Propene C3H6 [Vol.-%]
N 2 [V
ol.-%
] O2 [Vol.-%
]
stoichiometric
C 3H 6 + 1.5 O2 -
> 3 CO + 3 H 2
stoich
iometr
ic C 3
H 6 + 3
O 2 -> 3
CO +
3 H2O
stoich
iometr
ic C 3
H 6 + 4.
5 O2 -
> 3 C
O 2 +
3 H2O
range of deflagrative explosion, 10 bar abs, 200 °C
propene/air-mixtures
90
50
60
70
80
20
range of detonative
explosion
yellow range:possibly heat explosion (Heat explosion range and
detonative range were notdetermined. It might bethat the detonative rangeeven extends down to theair line)
1 bar abs 5 bar abs
10 bar abs 30 bar abs
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 19
Different explosion regimes (deflagration, heat explosion, detonation) of Methane/O2/N2 in a 20 l sphere at 1 and 5 bar abs, 25 °C and 200 °C
0 10 20 30 40 50 60 70 80 90 1000
10
20
30
40
50
60
70
80
90
1000
10
20
60
70
90
100
Methane CH4 [Vol.-%]
N 2 [V
ol.-%
] O2 [Vol.-%
]
yellow range:possibly heat explosion
80
50
30
40
methane/air-mixtures
range of
deflagrative explosion,
1 bar abs, 25 °Csto
ichiom
etric CH 4
+ 2O2 -
> CO 2 + 2H
2O
stoich
iometric CH4 + 1.5O 2 -
> CO + 2H2O
stoichiometric CH4 + 0.5O2 -> CO + 2H2
soot formation starts
at 55 vol.-% CH
4
mixture reacts sometimesdetonative and sometimesas heat explosion
0 10 20 30 40 50 60 70 80 90 1000
10
20
30
40
50
60
70
80
90
1000
10
20
60
70
90
100
Methane CH4 [Vol.-%]
N 2 [V
ol.-%
] O2 [Vol.-%
]
yellow range:possibly heat explosion
80
50
30
40
methane/air-mixtures
stoich
iometric
CH4 + 2O
2 -> CO2 +
2H2O
stoich
iometric CH4 + 1.5O2 -
> CO + 2H2O
soot formation starts
at 55 vol.-% CH
4
range of detonative explosion
range of
deflagrative explosion,
5 bar abs, 200 °C
stoichiometric CH4 + 0.5O2 -> CO + 2H2
0 10 20 30 40 50 60 70 80 90 1000
10
20
30
40
50
60
70
80
90
1000
10
20
60
70
90
100
Methane CH4 [Vol.-%]
N 2 [V
ol.-%
] O2 [Vol.-%
]
yellow range:possibly heat explosion
80
50
30
40
methane/air-mixtures
stoich
iometric
CH 4 + 2O
2 -> CO2 +
2H2O
stoich
iometric CH4 + 1.5O2 ->
CO + 2H2O
soot formation starts
at 55 vol.-% CH
4
range of detonative explosion
range of
deflagrative explosion,
5 bar abs, 25 °C
stoichiometric CH4 + 0.5O2 -> CO + 2H2
1 bar abs, 25 °C 5 bar abs, 25 °C
5 bar abs, 200 °C
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 20
0 10 20 30 40 50 60 70 80 90 100Propene C3H6 [Vol.-%]
0
10
20
30
40
50
60
70
80
90
100
O2 [Vol.-%
]
0
10
20
30
40
50
60
70
80
90
100
N 2 [V
ol.-%
]
range of deflagrative explosion, 5 bar abs, 25 °C
range of detonative
explosion
stoich
iometric C3H6 +
1.5 O2 -> 3 CO + 3 H2
stoich
iometr
ic C 3H
6 + 3
O 2 -> 3
CO +
3 H2O
stoich
iometr
ic C 3H
6 + 4.
5 O2 -
> 3 C
O 2 + 3
H 2O
propene/air-mixtures
Pressure-time traces of Propene/O2 at 5 bar, 25 °C (1)
171 171.5 172 172.5 173 173.5 1740
100
200
300
Time [ms]0 100 200 300
0
25
50
75
100
Time [ms]
Pre
ssur
e [b
ar a
bs]
File: PROP08A;Propene=3, O2=97 Vol.%; 5bar abs; 25C.DAT
Propene = 3 vol.-%O2 = 97 vol.-%, 5 bar abs, 25 °C
0 20 40 600
25
50
75
100
Time [ms]
Pre
ssur
e [b
ar a
bs]
File: PROP142A-4%.DAT
26 26.5 27 27.5 28 28.5 290
25
50
75
100
125
150
Time [ms]
Propene = 4 vol.-%O2 = 96 vol.-%, 5 bar abs, 25 °C
0 500 1000 1500 2000 2500 30000
5
10
15
20
25
30
Time [ms]
Pre
ssur
e [b
ar a
bs]
File: PROP76-2.25%.DAT
Propene = 2.25 vol.-%O2 = 97.75 vol.-%, 5 bar abs, 25 °C
topcenterbottom
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 21
0 10 20 30 40 50 60 70 80 90 100Propene C3H6 [Vol.-%]
0
10
20
30
40
50
60
70
80
90
100
O2 [Vol.-%
]
0
10
20
30
40
50
60
70
80
90
100
N 2 [V
ol.-%
]
range of deflagrative explosion, 5 bar abs, 25 °C
range of detonative
explosion
stoich
iometric C3H6 +
1.5 O2 -> 3 CO + 3 H2
stoich
iometr
ic C 3H
6 + 3
O 2 -> 3
CO +
3 H2O
stoich
iometr
ic C 3H
6 + 4.
5 O2 -
> 3 C
O 2 + 3
H 2O
propene/air-mixtures
topcenterbottom
Pressure-time traces of Propene/O2 at 5 bar, 25 °C (2)
14 14.5 15 15.5 16 16.5 170
50
100
150
200
250
Time [ms]0 5 10 15 20 25 30
0
25
50
75
100
Time [ms]
Pre
ssur
e [b
ar a
bs]
File: PROP07A;Propene=5, O2=95 Vol.%; 5bar abs; 25C.DAT
Propene = 5 vol.-%O2 = 95 vol.-%, 5 bar abs, 25 °C
0 2.5 5 7.5 10 12.5 150
25
50
75
100
Time [ms]
Pre
ssur
e [b
ar a
bs]
File: PROP06A;Propene=6, O2=94 Vol.%; 5bar abs; 25C.DAT
6.5 7 7.5 8 8.5 9 9.50
100
200
300
400
Time [ms]
Propene = 6 vol.-%,O2 = 94 vol.-%, 5 bar abs, 25 °C
0 5 10 15 200
25
50
75
100
125
150
Time [ms]
Pre
ssur
e [b
ar a
bs]
File: PROP09A;Propene=7, O2=93 Vol.%; 5bar abs; 25C.DAT
5 5.5 6 6.5 7 7.5 80
100
200
300
400
500
Time [ms]
Propene = 7 vol.-%,O2 = 93 vol.-%, 5 bar abs, 25 °C
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 22
0 10 20 30 40 50 60 70 80 90 100Propene C3H6 [Vol.-%]
0
10
20
30
40
50
60
70
80
90
100
O2 [Vol.-%
]
0
10
20
30
40
50
60
70
80
90
100
N 2 [V
ol.-%
]
range of deflagrative explosion, 5 bar abs, 25 °C
range of detonative
explosion
stoich
iometric C3H6 +
1.5 O2 -> 3 CO + 3 H2
stoich
iometr
ic C 3H
6 + 3
O 2 -> 3
CO +
3 H2O
stoich
iometr
ic C 3H
6 + 4.
5 O2 -
> 3 C
O 2 + 3
H 2O
propene/air-mixtures
topcenterbottom
Pressure-time traces of Propene/O2 at 5 bar, 25 °C (3)
3 3.5 4 4.5 5 5.5 60
100
200
300
400
500
Time [ms]0 5 10 15 20
0
25
50
75
100
125
150
Time [ms]
Pre
ssur
e [b
ar a
bs]
File: PROP84A-8%.DAT
Propene = 8 vol.-%,O2 = 92 vol.-%, 5 bar abs, 25 °C
0 5 10 15 200
25
50
75
100
125
150
Time [ms]
Pre
ssur
e [b
ar a
bs]
File: PROP143A-13%.DAT
1 1.5 2 2.5 3 3.5 40
100
200
300
400
Time [ms]
Propene = 13 vol.-%,O2 = 87 vol.-%, 5 bar abs, 25 °C
0 5 10 15 200
25
50
75
100
125
150
Time [ms]
Pre
ssur
e [b
ar a
bs]
File:PROP130A-18.2%.DAT
0 0.5 1 1.5 2 2.5 30
100
200
300
400
500
Time [ms]
Propene = 18.18 vol.-%,O2 = 81.82 vol.-%, 5 bar abs, 25 °C
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 23
0 10 20 30 40 50 60 70 80 90 100Propene C3H6 [Vol.-%]
0
10
20
30
40
50
60
70
80
90
100
O2 [Vol.-%
]
0
10
20
30
40
50
60
70
80
90
100
N 2 [V
ol.-%
]
range of deflagrative explosion, 5 bar abs, 25 °C
range of detonative
explosion
stoich
iometric C3H6 +
1.5 O2 -> 3 CO + 3 H2
stoich
iometr
ic C 3H
6 + 3
O 2 -> 3
CO +
3 H2O
stoich
iometr
ic C 3H
6 + 4.
5 O2 -
> 3 C
O 2 + 3
H 2O
propene/air-mixtures
topcenterbottom
Pressure-time traces of Propene/O2 at 5 bar, 25 °C (4)
0 5 10 150
25
50
75
100
125
150
Time [ms]
Pre
ssur
e [b
ar a
bs]
File: PROP131A-23%.DAT
0 0.5 1 1.5 2 2.5 30
50
100
150
200
Time [ms]
Propene = 23 vol.-%,O2 = 77 vol.-%, 5 bar abs, 25 °C
0 5 10 150
25
50
75
100
125
150
Time [ms]
Pre
ssur
e [b
ar a
bs]
File: Prope132a.dat, 28 vol.-%
Propene = 28 vol.-%,O2 = 72 vol.-%, 5 bar abs, 25 °C
0 0.5 1 1.5 2 2.5 30
200
400
600
800
Time [ms]
0 5 10 15 200
50
100
150
Time [ms]
Pre
ssur
e [b
ar a
bs]
2 2.5 3 3.5 4 4.5 50
200
400
600
800
Time [ms]
File:PROP137A-33%.DAT
Propene = 33 vol.-%O2 = 67 vol.-%, 5 bar abs, 25 °C
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 24
0 10 20 30 40 50 60 70 80 90 100Propene C3H6 [Vol.-%]
0
10
20
30
40
50
60
70
80
90
100
O2 [Vol.-%
]
0
10
20
30
40
50
60
70
80
90
100
N 2 [V
ol.-%
]
range of deflagrative explosion, 5 bar abs, 25 °C
range of detonative
explosion
stoich
iometric C3H6 +
1.5 O2 -> 3 CO + 3 H2
stoich
iometr
ic C 3H
6 + 3
O 2 -> 3
CO +
3 H2O
stoich
iometr
ic C 3H
6 + 4.
5 O2 -
> 3 C
O 2 + 3
H 2O
propene/air-mixtures
topcenterbottom
Pressure-time traces of Propene/O2 at 5 bar, 25 °C (5)
5 10 15 200
50
100
150
Time [ms]
Pre
ssur
e [b
ar a
bs]
File:PROP10A;Propene=35.5, O2=64.5 Vol.%; 5bar abs; 25C.DAT
4 4.5 5 5.5 6 6.5 70
100
200
300
400
500
Time [ms]
Propene = 35.5 vol.-%O2 = 64.5 vol.-%, 5 bar abs, 25 °C
10 15 20 250
50
100
150
Time [ms]
Pre
ssur
e [b
ar a
bs]
File: PROP136A-38%.DAT
11 11.5 12 12.5 13 13.5 140
100
200
300
400
Time [ms]
Propene = 38 vol.-%O2 = 62 vol.-%, 5 bar abs, 25 °C
Propene = 39 vol.-%,O2 = 61 vol.-%, 5 bar abs, 25 °C
15 20 25 30 350
50
100
150
Time [ms]
Pre
ssur
e [b
ar a
bs]
17 17.5 18 18.5 19 19.5 200
100
200
300
400
500
Time [ms]
File: Prope11A;Propene=39, O2=61 vol.-%, 5 bar abs, 25C
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 25
0 10 20 30 40 50 60 70 80 90 100Propene C3H6 [Vol.-%]
0
10
20
30
40
50
60
70
80
90
100
O2 [Vol.-%
]
0
10
20
30
40
50
60
70
80
90
100
N 2 [V
ol.-%
]
range of deflagrative explosion, 5 bar abs, 25 °C
range of detonative
explosion
stoich
iometric C3H6 +
1.5 O2 -> 3 CO + 3 H2
stoich
iometr
ic C 3H
6 + 3
O 2 -> 3
CO +
3 H2O
stoich
iometr
ic C 3H
6 + 4.
5 O2 -
> 3 C
O 2 + 3
H 2O
propene/air-mixtures
topcenterbottom
Pressure-time traces of Propene/O2 at 5 bar, 25 °C (6)
15 20 25 30 350
50
100
150
Time [ms]
Pre
ssur
e [b
ar a
bs]
File: PROP12A;Propene=40, O2=60 Vol.%; 5bar abs; 25C.DAT
22 22.5 23 23.5 24 24.5 250
100
200
300
400
500
Time [ms]
Propene = 40 vol.-%,O2 = 60 vol.-%, 5 bar abs, 25 °C
20 25 30 35 400
50
100
150
Time [ms]
Pre
ssur
e [b
ar a
bs]
File: PROP13A;Propene=41, O2=59 Vol.%; 5bar abs; 25C.DAT
Propene = 41 vol.-%,O2 = 60 vol.-%, 5 bar abs, 25 °C
26 26.5 27 27.5 28 28.5 290
100
200
300
400
500
Time [ms]
30 35 40 45 500
50
100
150
Time [ms]
Pre
ssur
e [b
ar a
bs]
File: PROP14A;Propene=42, O2=58 Vol.%; 5bar abs; 25C.DAT
34 34.5 35 35.5 36 36.5 370
100
200
300
400
500
Time [ms]
Propene = 42 vol.-%,O2 = 58 vol.-%, 5 bar abs, 25 °C
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 26
0 10 20 30 40 50 60 70 80 90 100Propene C3H6 [Vol.-%]
0
10
20
30
40
50
60
70
80
90
100
O2 [Vol.-%
]0
10
20
30
40
50
60
70
80
90
100
N 2 [V
ol.-%
]
range of deflagrative explosion, 5 bar abs, 25 °C
range of detonative
explosion
stoich
iometric C3H6 +
1.5 O2 -> 3 CO + 3 H2
stoich
iometr
ic C 3H
6 + 3
O 2 -> 3
CO +
3 H2O
stoich
iometr
ic C 3H
6 + 4.
5 O2 -
> 3 C
O 2 + 3
H 2O
propene/air-mixtures
top
Pressure-time traces of Propene/O2 at 5 bar, 25 °C (7)
Propene = 43 vol.-%,O2 = 57 vol.-%, 5 bar abs, 25 °C
55 60 65 70 750
50
100
150
Time [ms]
Pre
ssur
e [b
ar a
bs]
File: PROP139A-43%.DAT
61 61.5 62 62.5 63 63.5 640
50
100
150
Time [ms]
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 27
Pressure-time traces of stoich. Propene/O2/N2 at 5 bar, 25 °C (1)
0 10 20 30 40 500
10
20
30
40
50
Time [ms]
Pre
ssur
e [b
ar a
bs]
File: PROP15A; Propen=5.5, O2=25, N2=69.5 Vol.%;5bar abs;25C.DAT
Propene = 5.5 vol.-%O2 = 24.75 vol.-%, N2= 69.755 bar abs, 25 °C
0 10 20 30 400
25
50
75
100
Time [ms]
Pres
sure
[bar
abs
]
File: PROP208A-27%O2(erster Test).DAT
18 18.5 19 19.5 20 20.5 210
50
100
150
200
Time [ms]
Propene = 6 vol.-%O2 = 27 vol.-%, N2 = 675 bar abs, 25 °C
(first test)
0 10 20 30 400
25
50
75
100
Time [ms]
Pre
ssur
e [b
ar a
bs]
File: PROP209A-27%O2(zweiter Test).DAT
Propene = 6 vol.-%O2 = 27 vol.-%, N2 = 675 bar abs, 25 °C
(second test)
20 20.5 21 21.5 22 22.5 230
25
50
75
100
Time [ms]
0 10 20 30 40 50 60Propene C3H6 [Vol.-
8
90
1000
10
20
30
40
50
60
70
80
90
100
N 2 [V
ol.-%
]
randeflagrati 5 bar a
range of detonativ
explosion
stoich
iometric C3H6 +
1.5 O2 -> 3 CO +
stoich
iometr
ic C 3H
6 + 3
O 2 -> 3
CO +
3 H2O
stoich
iometr
ic C 3H
6 + 4.
5 O2 -
> 3 C
O 2 + 3
H 2O
propene/air
topcenterbottom
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 28
Pressure-time traces of stoich. Propene/O2/N2 at 5 bar, 25 °C (2)
0 5 10 15 200
25
50
75
100
Time [ms]
Pre
ssur
e [b
ar a
bs]
File:PROP16A;Propen=6.9, O2=31, N2=62.1 Vol.%;5bar abs;25C.DAT
Propene = 6.9 vol.-%O2 = 31 vol.-%, N2 = 62.15 bar abs, 25 °C
12 12.5 13 13.5 14 14.5 150
50
100
150
200
250
Time [ms]
0 5 10 15 200
25
50
75
100
Time [ms]
Pre
ssur
e [b
ar a
bs]
File: PROP207A-35%O2.DAT
7 7.5 8 8.5 9 9.5 100
50
100
150
200
Time [ms]
0 5 10 15 200
25
50
75
100
Time [ms]
Pre
ssur
e [b
ar a
bs]
File: PROP17A;Propen=7.8, O2=35, N2=57.2 Vol.%;5bar abs;25C.DAT
7 7.5 8 8.5 9 9.5 100
100
200
300
400
Time [ms]
Propene = 7.7 vol.-%O2 = 35 vol.-%, N2 = 57.35 bar abs, 25 °C
(second test)
Propene = 7.7 vol.-%O2 = 35 vol.-%, N2 = 57.35 bar abs, 25 °C
(first test)
Propene = 7.7 vol.-%O2 = 35 vol.-%, N2 = 57.35 bar abs, 25 °C
0 10 20 30 40 50 60Propene C3H6 [Vol.-%
80
90
1000
10
20
30
40
50
60
70
80
90
100
N 2 [V
ol.-%
]
rangedeflagrative 5 bar abs
range of detonative
explosion
stoich
iometric C3H6 +
1.5 O2 -> 3 CO + 3
stoich
iometr
ic C 3H
6 + 3
O 2 -> 3
CO +
3 H2O
stoich
iometr
ic C 3H
6 + 4.
5 O2 -
> 3 C
O 2 + 3
H 2O
propene/air-m
topcenterbottom
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 29
Pressure-time traces of stoich. Propene/O2/N2 at 5 bar, 25 °C (3)
0 5 10 15 200
25
50
75
100
Time [ms]
Pre
ssur
e [b
ar a
bs]
File: PROP18A;Propen=8.9, O2=40, N2=51.1 Vol.%;5bar abs;25C.DAT
Propene = 8.8 vol.-%O2 = 40 vol.-%, N2 = 51.25 bar abs, 25 °C
4.5 5 5.5 6 6.5 7 7.50
100
200
300
400
Time [ms]
1 1.5 2 2.5 3 3.5 40
50
100
150
200
250
300
Time [ms]0 5 10 15 20
0
25
50
75
100
Time [ms]
Pre
ssur
e [b
ar a
bs]
File: PROP216A-60%O2.DAT
Propene = 13.3 vol.-%O2 = 60 vol.-%, N2 = 26.75 bar abs, 25 °C
0 5 10 15 200
25
50
75
100
125
150
Time [ms]
Pre
ssur
e [b
ar a
bs]
File:PROP130A-18.2%.DAT
0 0.5 1 1.5 2 2.5 30
100
200
300
400
500
Time [ms]
Propene = 18.18 vol.-%,O2 = 81.82 vol.-%, 5 bar abs, 25 °C
0 10 20 30 40 50 60Propene C3H6 [Vol.-%
80
90
1000
10
20
30
40
50
60
70
80
90
100
N 2 [V
ol.-%
]
rangedeflagrative 5 bar abs
range of detonative
explosion
stoich
iometric C3H6 +
1.5 O2 -> 3 CO + 3
stoich
iometr
ic C 3H
6 + 3
O 2 -> 3
CO +
3 H2O
stoich
iometr
ic C 3H
6 + 4.
5 O2 -
> 3 C
O 2 + 3
H 2O
propene/air-m
top
center
bottom
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 30
Different explosion regimes (deflagration, heat explosion, detonation) of Methane/O2/N2 in a 20 l sphere at 1 and 5 bar abs, 25 °C and 200 °C
0 10 20 30 40 50 60 70 80 90 1000
10
20
30
40
50
60
70
80
90
1000
10
20
60
70
90
100
Methane CH4 [Vol.-%]
N 2 [V
ol.-%
] O2 [Vol.-%
]
yellow range:possibly heat explosion
80
50
30
40
methane/air-mixtures
range of
deflagrative explosion,
1 bar abs, 25 °Csto
ichiom
etric CH 4
+ 2O2 -
> CO 2 + 2H
2O
stoich
iometric CH4 + 1.5O 2 -
> CO + 2H2O
stoichiometric CH4 + 0.5O2 -> CO + 2H2
soot formation starts
at 55 vol.-% CH
4
mixture reacts sometimesdetonative and sometimesas heat explosion
0 10 20 30 40 50 60 70 80 90 1000
10
20
30
40
50
60
70
80
90
1000
10
20
60
70
90
100
Methane CH4 [Vol.-%]
N 2 [V
ol.-%
] O2 [Vol.-%
]
yellow range:possibly heat explosion
80
50
30
40
methane/air-mixtures
stoich
iometric
CH4 + 2O
2 -> CO2 +
2H2O
stoich
iometric CH4 + 1.5O2 -
> CO + 2H2O
soot formation starts
at 55 vol.-% CH
4
range of detonative explosion
range of
deflagrative explosion,
5 bar abs, 200 °C
stoichiometric CH4 + 0.5O2 -> CO + 2H2
0 10 20 30 40 50 60 70 80 90 1000
10
20
30
40
50
60
70
80
90
1000
10
20
60
70
90
100
Methane CH4 [Vol.-%]
N 2 [V
ol.-%
] O2 [Vol.-%
]
yellow range:possibly heat explosion
80
50
30
40
methane/air-mixtures
stoich
iometric
CH 4 + 2O
2 -> CO2 +
2H2O
stoich
iometric CH4 + 1.5O2 ->
CO + 2H2O
soot formation starts
at 55 vol.-% CH
4
range of detonative explosion
range of
deflagrative explosion,
5 bar abs, 25 °C
stoichiometric CH4 + 0.5O2 -> CO + 2H2
1 bar abs, 25 °C 5 bar abs, 25 °C
5 bar abs, 200 °C
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 31
Pressure-time traces of Methane/O2 at 5 bar, 25 °C (1)
Methane CH [Vol.-%]4
N
[Vol
.-%]
2
O [Vol.-%
]
2
yellow range:possibly heat explosion
stoich
iometric C
H+ 2O
-> CO
+ 2H O
4
2
2
2
Met
hane
= 7
vol
.-%,
O =
93
vol.-
%,
5 ba
r abs
, 25
°C2
0 100 200 300 400 500 600 7000
10
20
30
Time [ms]
Pre
ssur
e [b
ar a
bs]
0 5 10 15 20 25 300
10
20
30
40
50
60
Time [ms]
Pre
ssur
e [b
ar a
bs]
23 23.5 24 24.5 25 25.5 260
25
50
75
100
125
Time [ms]
Met
hane
= 1
0 v
ol.-%
,O
= 9
0 vo
l.-%
, 5
bar a
bs, 2
5 °C
2
13 13.5 14 14.5 150
50
100
150
200
Time [ms]0 5 10 15 20
0
20
40
60
Time [ms]
Pres
sure
[bar
abs
]
Met
hane
= 1
2 v
ol.-%
,O
= 8
8 vo
l.-%
, 5
bar a
bs, 2
5 °C
2
topcenterbottom
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 32
Pressure-time traces of Methane/O2 at 5 bar, 25 °C (2)
topcenterbottom
Methane CH [Vol.-%]4
N
[Vol
.-%]
2
O [Vol.-%
]
2
yellow range:possibly heat explosion
stoich
iometric C
H+ 2O
-> CO
+ 2H O
4
2
2
2
8 8.5 9 9.5 10 10.5 110
100
200
300
400
500
Time [ms]0 5 10 15 20
0
20
40
60
Time [ms]
Pres
sure
[bar
abs
]
Met
hane
= 1
4 v
ol.-%
,O
= 8
6 vo
l.-%
, 5
bar a
bs, 2
5 °C
2
Met
hane
= 1
5 v
ol.-%
,O
= 8
5 vo
l.-%
, 5
bar a
bs, 2
5 °C
2
5 5.5 6 6.5 7 7.5 80
50
100
150
200
Time [ms]0 5 10 15 20
0
20
40
60
Time [ms]
Pre
ssur
e [b
ar a
bs]
6 6.5 7 7.5 8 8.5 90
200
400
600
800
Time [ms]0 5 10 15 20
0
10
20
30
40
50
60
70
Time [ms]
Pres
sure
[bar
abs
]
2nd
test
:M
etha
ne =
15
vol
.-%,
O =
85
vol.-
%,
5 ba
r abs
, 25
°C2
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 33
Pressure-time traces of Methane/O2 at 5 bar, 25 °C (3)
topcenterbottom
Methane CH [Vol.-%]4
N
[Vol
.-%]
2
O [Vol.-%
]
2
yellow range:possibly heat explosion
stoich
iometric C
H+ 2O
-> CO
+ 2H O
4
2
2
2
3 3.5 4 4.5 5 5.5 60
50
100
150
200
250
Time [ms]0 2.5 5 7.5 10
0
10
20
30
40
50
60
70
Time [ms]
Pres
sure
[bar
abs
]
Met
hane
= 1
7.5
vol
.-%,
O =
82.
5 vo
l.-%
, 5
bar a
bs, 2
5 °C
2
3 3.5 4 4.5 5 5.5 60
100
200
300
400
500
Time [ms]0 2.5 5 7.5 10
0
10
20
30
40
50
60
70
Time [ms]
Pre
ssur
e [b
ar a
bs]
Met
hane
= 2
0 v
ol.-%
,O
= 8
0 vo
l.-%
, 5
bar a
bs, 2
5 °C
2
3 3.5 4 4.5 5 5.5 60
100
200
300
400
500
Time [ms]0 2.5 5 7.5 10
0
25
50
75
100
125
Time [ms]
Pres
sure
[bar
abs
]
2nd
test
:M
etha
ne =
20
vol
.-%,
O =
80
vol.-
%,
5 ba
r abs
, 25
°C2
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 34
Pressure-time traces of Methane/O2 at 5 bar, 25 °C (4)
topcenterbottom
Methane CH [Vol.-%]4
N
[Vol
.-%]
2
O [Vol.-%
]
2
yellow range:possibly heat explosion
stoich
iometric C
H+ 2O
-> CO
+ 2H O
4
2
2
2
0 2.5 5 7.5 100
25
50
75
100
125
Time [ms]
Pre
ssur
e [b
ar a
bs]
1 1.5 2 2.5 3 3.5 40
100
200
300
400
Time [ms]
Met
hane
= 2
5 v
ol.-%
,O
= 7
5 vo
l.-%
, 5
bar a
bs, 2
5 °C
2
0 2.5 5 7.5 100
25
50
75
100
125
Time [ms]
Pre
ssur
e [b
ar a
bs]
1 1.5 2 2.5 3 3.5 40
50
100
150
200
250
300
Time [ms]
2nd
test
:M
etha
ne =
25
vol
.-%,
O =
75
vol.-
%,
5 ba
r abs
, 25
°C2
0 2.5 5 7.5 100
25
50
75
100
125
Time [ms]
Pre
ssur
e [b
ar a
bs]
1 1.5 2 2.5 3 3.5 40
200
400
600
800
Time [ms]
3rd
test
:M
etha
ne =
25
vol
.-%,
O =
75
vol.-
%,
5 ba
r abs
, 25
°C2
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 35
Pressure-time traces of Methane/O2 at 5 bar, 25 °C (5)
topcenterbottom
Methane CH [Vol.-%]4
N
[Vol
.-%]
2
O [Vol.-%
]
2
yellow range:possibly heat explosion
stoich
iometric C
H+ 2O
-> CO
+ 2H O
4
2
2
2
0 2.5 5 7.5 100
25
50
75
100
125
Time [ms]
Pres
sure
[bar
abs
]
0 0.5 1 1.5 2 2.5 30
50
100
150
200
250
300
Time [ms]
Methane = 35 vol.-%,O = 65 vol.-%, 5 bar abs, 25 °C
2
0 2.5 5 7.5 100
25
50
75
100
125
150
Time [ms]
Pre
ssur
e [b
ar a
bs]
2 2.5 3 3.5 4 4.5 50
100
200
300
400
500
Time [ms]
Met
hane
= 4
0 v
ol.-%
,O
= 6
0 vo
l.-%
, 5
bar a
bs, 2
5 °C
2
3 3.5 4 4.5 5 5.5 60
100200300400500600700800900
Time [ms]0 2.5 5 7.5 10
0
25
50
75
100
125
150
Time [ms]
Pre
ssur
e [b
ar a
bs]
Met
hane
= 4
5 v
ol.-%
,O
= 5
5 vo
l.-%
, 5
bar a
bs, 2
5 °C
2
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 36
Pressure-time traces of Methane/O2 at 5 bar, 25 °C (6)
topbottom
Methane CH [Vol.-%]4
N
[Vol
.-%]
2
O [Vol.-%
]
2 yellow range:possibly heat explosion
stoich
iometric C
H+ 2O
-> CO
+ 2H O
4
2
2
2
5 10 15 20 250
25
50
75
100
125
150
Time [ms]
Pres
sure
[bar
abs
]
14 14.5 15 15.5 16 16.5 170
100
200
300
400
500
Time [ms]
Met
hane
= 5
0 vo
l.-%
,O
= 5
0 vo
l.-%
, 5
bar a
bs, 2
5 °C
2
0 25 50 75 100 125 1500
20
40
60
80
Time [ms]
Pres
sure
[bar
abs
]
Met
hane
= 5
5 vo
l.-%
,O
= 4
5 vo
l.-%
, 5
bar a
bs, 2
5 °C
2
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 37
Pressure-time traces of stoich. Methane/O2/N2 at 5 bar, 25 °C (1)
top
bottom
Methane CH [Vol.-%]4
N
[Vol
.-%]
2
yellow range:possibly heat explosion
stoich
iometric C
H+ 2O
-> CO
+ 2H O
4
2
2
2
0 100 200 300 4000
10
20
30
40
Time [ms]
Pres
sure
[bar
abs
]
Met
hane
= 1
0 v
ol.-%
,O
= 2
0 vo
l.-%
, N
= 7
0 vo
l.-%
,5
bar a
bs, 2
5 °C
2 2
0 5 10 15 20 25 300
20
40
60
80
Time [ms]
Pres
sure
[bar
abs
]
16 16.5 17 17.5 18 18.5 190
20
40
60
80
Time [ms]
Met
hane
= 1
5 v
ol.-%
,O
= 3
0 vo
l.-%
, N
= 5
5 vo
l.-%
,5
bar a
bs, 2
5 °C
2 2
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 38
Pressure-time traces of stoich. Methane/O2/N2 at 5 bar, 25 °C (2)
topbottom
Methane CH [Vol.-%]4N
[V
ol.-%
]
2
yellow range:possibly heat explosion
stoich
iometric C
H+ 2O
-> CO
+ 2H O
4
2
2
2
0 5 10 15 200
20
40
60
Time [ms]
Pre
ssur
e [b
ar a
bs]
4 4.5 5 5.5 6 6.5 70
20
40
60
Time [ms]
0 5 10 15 200
50
100
150
Time [ms]
Pre
ssur
e [b
ar a
bs]
3 3.5 4 4.5 5 5.5 60
50
100
150
Time [ms]
Met
hane
= 2
0 v
ol.-%
,O
= 4
0 vo
l.-%
, N
= 4
0 vo
l.-%
,5
bar a
bs, 2
5 °C
2 2
Met
hane
= 2
5 v
ol.-%
,O
= 5
0 vo
l.-%
, N
= 2
5 vo
l.-%
,5
bar a
bs, 2
5 °C
2 2
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 39
Pressure-time traces of Methane/O2 at 5 bar, 200 °C (1)
Methane CH [Vol.-%]4
N
[Vol
.-%]
2
O [Vol.-%
]
2
yellow range:possibly heat explosion
stoich
iometric C
H+ 2O
-> CO
+ 2H O
4
2
2
2
Met
hane
= 1
0 v
ol.-%
,O
= 9
0 vo
l.-%
,,5
bar a
bs, 2
00 °
C2
0 10 20 30 400
5
10
15
20
25
30
Time [ms]
Pre
ssur
e [b
ar a
bs]
12 12.5 13 13.5 14 14.5 150
10
20
30
40
Time [ms]0 5 10 15 20
0
10
20
30
40
Time [ms]
Pre
ssur
e [b
ar a
bs]
Met
hane
= 1
2.5
vol.-
%,
O =
87.
5 vo
l.-%
,,5
bar a
bs, 2
00 °
C2
8 8.5 9 9.5 10 10.5 110
10
20
30
40
Time [ms]0 5 10 15 20
0
10
20
30
40
Time [ms]
Pre
ssur
e [b
ar a
bs]
Met
hane
= 1
4 vo
l.-%
,O
= 8
6 vo
l.-%
,,5
bar a
bs, 2
00 °
C2
topcenterbottom
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 40
Pressure-time traces of Methane/O2 at 5 bar, 200 °C (2)
Methane CH [Vol.-%]4
N
[Vol
.-%]
2
O [Vol.-%
]
2
yellow range:possibly heat explosion
stoich
iometric C
H+ 2O
-> CO
+ 2H O
4
2
2
2
topcenterbottom
6 6.5 7 7.5 8 8.5 90
100
200
300
400
Time [ms]0 2.5 5 7.5 10
0
10
20
30
40
Time [ms]
Pre
ssur
e [b
ar a
bs]
Met
hane
= 1
5 vo
l.-%
,O
= 8
5 vo
l.-%
,,5
bar a
bs, 2
00 °
C2
4 4.5 5 5.5 6 6.5 70
100
200
300
400
Time [ms]0 2.5 5 7.5 10
0
10
20
30
40
Time [ms]
Pre
ssur
e [b
ar a
bs]
Met
hane
= 1
7.5
vol.-
%,
O =
82.
5 vo
l.-%
,,5
bar a
bs, 2
00 °
C2
0 2.5 5 7.5 100
25
50
75
100
Time [ms]
Pre
ssur
e [b
ar a
bs]
3 3.5 4 4.5 5 5.5 60
100
200
300
400
Time [ms]
Met
hane
= 2
0 vo
l.-%
,O
= 8
0 vo
l.-%
,,5
bar a
bs, 2
00 °
C2
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 41
Pressure-time traces of Methane/O2 at 5 bar, 200 °C (3)
Methane CH [Vol.-%]4
N
[Vol
.-%]
2
O [Vol.-%
]
2
yellow range:possibly heat explosion
stoich
iometric C
H+ 2O
-> CO
+ 2H O
4
2
2
2
top
centerbottom
0 2.5 5 7.5 100
25
50
75
100
Time [ms]
Pre
ssur
e [b
ar a
bs]
2 2.5 3 3.5 4 4.5 50
100
200
300
400
Time [ms]
Met
hane
= 2
5 vo
l.-%
,O
= 7
5 vo
l.-%
,,5
bar a
bs, 2
00 °
C2
Met
hane
= 4
0 v
ol.-%
,O
= 6
0 vo
l.-%
,,5
bar a
bs, 2
00 °
C2
0 2.5 5 7.5 100
25
50
75
100
Time [ms]
Pre
ssur
e [b
ar a
bs]
2 2.5 3 3.5 4 4.5 50
100
200
300
400
500
Time [ms]
4 4.5 5 5.5 6 6.5 70
100
200
300
400
500
Time [ms]0 2.5 5 7.5 10
0
25
50
75
100
Time [ms]
Pre
ssur
e [b
ar a
bs]
Met
hane
= 4
5 v
ol.-%
,O
= 5
5 vo
l.-%
,,5
bar a
bs, 2
00 °
C2
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 42
Pressure-time traces of Methane/O2 at 5 bar, 200 °C (4)
Methane CH [Vol.-%]4
N
[Vol
.-%]
2
O [Vol.-%
]
2
yellow range:possibly heat explosion
stoich
iometric C
H+ 2O
-> CO
+ 2H O
4
2
2
2
top
centerbottom
0 5 10 15 200
25
50
75
100
Time [ms]
Pre
ssur
e [b
ar a
bs]
10 10.5 11 11.5 12 12.5 130
50
100
150
200
250
Time [ms]
0 100 200 300 4000
10
20
30
40
50
Time [ms]
Pre
ssur
e [b
ar a
bs]
Met
hane
= 5
0 v
ol.-%
,O
= 5
0 vo
l.-%
,,5
bar a
bs, 2
00 °
C2
Methane = 55 vol.-%,O = 45 vol.-%,,5 bar abs, 200 °C
2
0 200 400 600 8000
10
20
30
Time [ms]
Pre
ssur
e [b
ar a
bs]
Met
hane
= 6
2 vo
l.-%
,O
= 3
8 vo
l.-%
,,5
bar a
bs, 2
00 °
C2
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 43
Pressure-time traces of stoich. Methane/O2/N2 at 5 bar, 200 °C (1)
0 5 10 15 20 25 300
10
20
30
40
Time [ms]
Pre
ssur
e [b
ar a
bs]
Met
hane
= 1
5 v
ol.-%
,O
= 3
0 vo
l.-%
,,N
= 5
5 vo
l.-%
, 5
bar a
bs, 2
00 °
C
2 2
0 2.5 5 7.5 10 12.5 150
10
20
30
40
50
Time [ms]
Pre
ssur
e [b
ar a
bs]
6 6.5 7 7.5 8 8.5 90
10
20
30
40
50
Time [ms]
Met
hane
= 2
0 v
ol.-%
,O
= 4
0 vo
l.-%
,,N
= 4
0 vo
l.-%
, 5
bar a
bs, 2
00 °
C
2 2
0 2.5 5 7.5 10 12.5 150
10
20
30
40
50
Time [ms]
Pre
ssur
e [b
ar a
bs]
6 6.5 7 7.5 8 8.5 90
10
20
30
40
50
Time [ms]
2nd
test
:M
etha
ne =
20
vol
.-%,
O =
40
vol.-
%,,
N =
40
vol.-
%,
5 ba
r abs
, 200
°C
2 2 Methane CH [Vol.-%]4
N
[Vol
.-%]
2
O [
2
yellow range:possibly heat explosion
stoich
iometric C
H+ 2O
-> CO
+ 2H O
4
2
2
2
topcenterbottom
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 44
Pressure-time traces of stoich. Methane/O2/N2 at 5 bar, 200 °C (2)
0 2.5 5 7.5 100
25
50
75
100
Time [ms]
Pre
ssur
e [b
ar a
bs]
3 3.5 4 4.5 5 5.5 60
25
50
75
100
Time [ms]
0 2.5 5 7.5 100
25
50
75
100
Time [ms]
Pre
ssur
e [b
ar a
bs]
1 1.5 2 2.5 3 3.5 40
25
50
75
100
Time [ms]
Met
hane
= 2
5 v
ol.-%
,O
= 5
0 vo
l.-%
,,N
= 2
5 vo
l.-%
, 5
bar a
bs, 2
00 °
C
2 2
Met
hane
= 3
0 v
ol.-%
,O
= 6
0 vo
l.-%
,,N
= 1
0 vo
l.-%
, 5
bar a
bs, 2
00 °
C
2 2
0 2.5 5 7.5 10 12.5 150
25
50
75
100
Time [ms]
Pre
ssur
e [b
ar a
bs]
7.5 8 8.5 9 9.5 10 10.50
25
50
75
100
Time [ms]
Note:This is not on the stoichiometric line!!Methane = 15 vol.-%,O = 55 vol.-%,,N = 30 vol.-%, 5 bar abs, 200 °C
2
2
Methane CH [Vol.-%]4
N
[Vol
.-%]
2
O2
yellow range:possibly heat explosion
stoich
iometric C
H+ 2O
-> CO
+ 2H O
4
2
2
2
top
centerbottom
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 45
Summary of the differences in the pressure time diagrams betweenexplosions in vessels that were triggered by a thermal ignition andended up as deflagration, “heat explosion” or detonation
course of explosion deflagration heat explosion detonation
presence of pressure pulse
no yes yes
width of pressure pulse at half height [µs]
(not applicable)
100 - 200 < 50
height of pressure pulse divided by pressure in mixture just before its occurrence
(not applicable)
typically 4 to 7 (equals deflagration pressure ratio of the
precompressed unreacted mixture)
typically 15 to 50 (due to too small
sampling rate the true maximum was
presumably mostly missed)
precompression ratio at the moment when pressure pulse occurs
(not applicable)
5 – 10 (largest value equals
pex/pinitial of the corresponding gas
mixture)
1 – 20 (largest value equals
pex/pinitial of the corresponding gas
mixture) "oscillations" in reaction gases after occurrence of pressure pulse
no oscillations anyway
no oscillations massive oscillations (due to shock front bouncing backwards and for-wards in reaction
gases) acoustic sound heard outside the vessel
nothing “click” prolonged whistle
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 46
Heat explosion – tentative explanation of the course of events
024
1086
12
radial position r/R0 0 1
hot reaction gases
flam
e fro
ntpr
ecom
pres
sed
unre
acte
d m
ixtu
re
pres
sure
/pin
itial
Before heat explosion:Reaction rate sufficiently slow to allow for pressure equilibrium over entire sphere
Pressure as function of radial position in 20 l sphere (pinitial = 1 bar abs) justbefore heat explosion occurs in theprecompressed, unreacted mixture(R0 = 17 cm)
After heat explosion:reaction gases flow to the central part of the sphere and pressure equilibrium is attained
At heat explosion:Immediate temperature rise and hence also pressure rise in the shell so far unreacted, but heated by adiabatic compression. The induction time must be of the order of 0.1 ms or even less, otherwise the flame front of the initial deflagration would have run through the thin shell of unreacted mixture before the heat explosion could develop.
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 47
Temperatures obtainable by adiabatic compression
( )γ
γ 1−
⎟⎠⎞
⎜⎝⎛⋅=
initialfinal
initialfinal pp
TT
pfinal/pinitial Tfinal [°C] resulting for different values of γ in case that Tinitial = 35 °C = 308 K
Tfinal [°C] resulting for differrent values of γ in case that Tinitial = 200 °C = 473 K
γ = 1,4 γ = 1,3 γ = 1,2 γ = 1,1 γ = 1,4 γ = 1,3 γ = 1,2 γ = 1,11,5 72,8 65,2 56,5 46,6 258,1 246,4 233,1 217,82 102,5 88,4 72,7 55,0 303,6 282,0 257,9 230,83 148,6 123,9 96,9 67,3 374,4 336,5 295,0 249,74 184,7 151,1 115,1 76,4 429,9 378,3 322,9 263,55 214,8 173,5 129,8 83,5 476,1 412,7 345,5 274,56 240,9 192,7 142,2 89,5 516,2 442,2 364,6 283,77 264,0 209,6 153,0 94,6 551,7 468,1 381,2 291,58 284,9 224,7 162,6 99,1 583,8 491,3 395,9 298,49 304,0 238,4 171,2 103,1 613,1 512,4 409,2 304,610 321,7 251,0 179,1 106,7 640,2 531,7 421,3 310,112 353,5 273,5 193,0 113,1 689,1 566,3 442,7 319,914 381,7 293,3 205,2 118,5 732,4 596,7 461,3 328,216 407,1 311,0 215,9 123,3 771,5 623,9 477,8 335,618 430,4 327,1 225,6 127,6 807,2 648,6 492,7 342,120 451,9 341,9 234,4 131,4 840,2 671,3 506,3 348,1
Formula for temperature increase due to adiabatic compression:
Temperatures may well lie above the ignition temperatures themixtures presumably have in the precompressed state!
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 48
Autoignition temperatures of Propene/O2/N2Propene [Vol.-%]
O2 [Vol.-%]
N2 [Vol.-%]
Autoignition Temperature (AIT) [°C]
AIT [°C] at Pinitial = 5 bar abs for Propene/O2 mixtures 4.46 95.54 0 280 7 93 0 270 10 90 0 270 20 80 0 260 30 70 0 260 40 60 0 250 50 50 0 250 60 40 0 250 AIT [°C] at Pinitial = 5 bar abs for stoichiometric (with respect to CO2 and H2O-formation) Propene/O2 mixtures, i.e. Propene:O2 = 1 : 4.5 4.46 20.07 75.47 280 7 31.5 61.5 270 10 45 45.0 270 AIT [°C] at Pinitial = 1 bar abs for stoichiometric (with respect to CO2 and H2O-formation) Propene/O2 mixtures, i.e. Propene:O2 = 1 : 4.5 4.46 20.07 75.47 485 (CHEMSAFE, DIN-method in open Erlenmeyer
flask) 7.0 31.5 61.5 410 10.0 45.0 45.0 310 15.5 70.0 14.5 290
0 10 20 30 40 50 60 70 80 90 100Propene C3H6 [Vol.-%]
0
10
20
30
40
50
60
70
80
90
100
O2 [Vol.-%
]
0
10
20
30
40
50
60
70
80
90
100
N 2 [V
ol.-%
]
range of deflagrative explosion, 5 bar abs, 25 °C
range of detonative
explosion
stoich
iometric C3H6 +
1.5 O2 -> 3 CO + 3 H2
stoich
iometr
ic C 3H
6 + 3
O 2 -> 3
CO +
3 H2O
stoich
iometr
ic C 3H
6 + 4.
5 O2 -
> 3 C
O 2 + 3
H 2O
propene/air-mixtures
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 49
0
1
2
3
4
5
700 800 900 1000 1100 1200
Temperature, K
Indu
ctio
n tim
e, m
s
C3H6-O2-N2=20-40-40
C3H6-O2-N2=5-95-0
0 10 20 30 40 50 60 70 80 90 100Propene C3H6 [Vol.-%]
10
20
30
40
50
60
70
80
90
100
O2 [Vol.-%
]
0
10
20
30
40
50
60
70
80
90
100
N 2 [V
ol.-%
]
range of deflagrative explosion, 5 bar abs, 25 °C
range of detonative
explosion
stoich
iometric C3H6 +
1.5 O2 -> 3 CO + 3 H2
stoich
iometr
ic C 3H
6 + 3
O 2 -> 3
CO +
3 H2O
stoich
iometr
ic C 3H
6 + 4.
5 O2 -
> 3 C
O 2 + 3
H 2O
propene/air-mixtures
Induction times of two mixture compositions lying in the yellow range of the explosion diagram at 5 bar abs
Propene= 5 vol.-%, O2 = 95 Vol.-%
Propene= 20 vol.-%,O2 = 40 vol.-%,N2 = 40 vol.-%
Calculation by A.A. Konnov, Department of Mechanical EngineeringVrije Universiteit Brussel (VUB),based on the rate coefficients for all elementary reactions
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 50
Is “heat explosion” a realistic assumption for what happens in yellow range of the explosion triangle ?
- temperatures achieved by adiabatic compression lie well abovethe autoignition temperature, i. e. heat explosion is possible in principle
- but: induction times calculated on the basis of the rate coefficientsof the elementary reactions are still far too long(The induction time would have to be of the order of 0.1 ms or even less, otherwise the flame front of the initial deflagration would have run already through the thin shell of unreacted mixture before the heat explosion can develop).
- including the influence of thermal radiation from the cental part of the spheredoes not give a substancial reduction in induction times either (calculation of Hans Pasman)
⇒ Not really clear what happens in theyellow range of the explosion triangle
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 51
Summary on explosion regimes of combustible/air/O2 mixturesignited with a thermal ignition source in vessel-like geometry
There are three explosion regimes: deflagration, „heat explosion“, detonation
The „heat explosion“ regime becomes much smaller with increasing initialpressure
Mixtures of type combustible/air seem to remain deflagrative even at elevatedpressures and temperatures. However, the data collected so far do not allow to exclude that the detonativeregime will expand down to the air line when going to extremely high initialpressures and large vessel volumes.
What really happens in the „heat explosion“ regime is not yet really understood,maybe the pressure time curves are just due to failed DDT‘s
The detonative range in the 20 l sphere is discernibly smaller than thepotentially detonative range
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 52
Explosion characteristics
Introduction
Course of explosion in 20 l sphere
Comparison: detonative regimesin 20 l vessels ↔ 100, 500, 2500 l vessels
Predetonation distances of Propene/O2 in tubes
Pressure load Pdet on the wall of the vessel- quantification of Pdet for four scenarios occuring in a pipe (no precompression)- quantification of Pdet for four scenarios occuring in a pipe (with precompression)- quantification of Pdet for Propene/O2/N2 in vessel at Pinitial = 5 bar abs, Tinitial = 20 °C
Did ignition source directly trigger a spherical detonation?
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 53
Schematic pressure-time trace of a detonative pressure pulse
Pinitial
deflagration pressure ratioof gas mixture
von Neumann spike, about twice as high as PCJ
PCJ , about twice the deflagration pressure ratio of the gas mixture
width < 1 µs => much less than cycle time of anyeigenfrequency of the containment
=> not „noticed“ by the containment and notregistered by the fastest available pressure sensors
Pre
ssur
e/P
initi
al
5
10
15
20
25
30
35
45
40
50
0time
unburned gas mixturehot reaction products flamefront coupledwith shockfront, v >> vsoundl
pressure sensor, flushwith inner surface of wall
Leading edge of detonation peakhas almost infinite slope (rise time < 1µs)
width of „Taylor expansion fan“: ca. 20 µs – 50 µs in laboratoryscale containments, longer in structures of larger dimensions(less than one quarter of the time interval over which the peak has already propagated)
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 54
Pressure-time diagrams recorded during a detonation in a long pipe at different locations (1/2)
Example: Propane/O2, stoichiometric, Pinitial = 6 bar abs, Tinitial = 20 °C, pipe 25x2, L = 5 m, side-on pressure
location of ignition
P1 P2 P3 P4 1025 mm 1970 mm
2915 mm 3855 mm
5000 mm
pipe: 25 x 2
v = Δs/Δt= 0.945m/0.375ms = 2519 m/s
Pdet ≅ 35*Pinitial
(same value at all sensors)
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 55
Pressure-time diagrams recorded during a detonation in a long pipe at different locations (2/2)Experiment:Ethylene/air stoichiometric,14 bar abs, 20 °C, side-on pressure, pipe: φi = 44.3 mm, φo = 48.3 mm, L = 8 m, turbulence enhancer in front of ignitionsource to reduce run-up distance
P3 P2 P1
2 m 1.5 m 0.5 m location of ignition
22 23 24 25 260
50
100
150
200
250
300
Time [ms]
Pres
sure
[bar
abs
]
22 23 24 25 260
100
200
300
Time [ms]Pr
essu
re [b
ar a
bs]
22 23 24 25 260
100
200
300
400
500
Time [ms]
Pres
sure
[bar
abs
]
P2
P1
P3
Δt = 1.033 ms
Δs = 1.5 m
vdet=Δs/Δt=1936 m/s
vdet=Δs/Δt=1883 m/s
Δs = 2 m
Δt = 0.796 ms
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 56
Qualitative consideration: differences between the pressures produced in a long pipe by a deflagration and by a detonation (2/2)
Detonative Explosion (predetonation stage necglected)
unburnt gas mixturehot reaction products flamefront coupledwith shockfront, v >> vsoundl
Pex
/Pin
itial
25
151050
20P = 9.5*Pinitial
P = Pinitial
extension:in space ca. 10 – 20 cmIn time ca. 20 – 50 µs
Location of ignition
distance from left pipe end
Pdet = 2*9.5*Pinitial
Example: Propane/air, stoichiometric, Tinitial = 20 °C, explosion pressure ratio: 9.5 (simplification: no heat loss to wall)
P is different at different locations in the pipe:- behind shockfront: P = 9.5*Pinitial (9.5 is explosion pressure ratio of mixture)- at shockfront: P = 2*9.5*Pinitial (i.e. about twice as high as behind shockfront)- in front of shockfront: P = Pinitial
(reason: reaction gases would like to expand into region ahead of shockfront, but speed of sound in hot reaction gases only about 1000 m/s whereas shockfront propagates with about 1700 m/s)
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 57
Detonation pressures Pdet in long pipes (L >> Lpredet, no precompression)
detonationfront
pressure sensor,flush with inner surface of wall
Stable Detonation, side-on pressure (i. e. in plane perpendicular to shockfront)
Stable Detonation, reflected pressure (i. e. in plane parallel to shockfront, e. g. blind flange)
detonationfront
pressure sensor,flush with inner surface of flangel
2 ≤ Freflec ≤ 2.5
PCJ is the so-calledChapman-Jouguet-pressure ratioof the explosive gas mixture
Pdet = Pinitial * PCJ
Pdet = Pinitial * PCJ * Freflec
Important:The pipe directly ahead of the blind flangeexperiences the reflected pressure as well. Thelength of this section corresponds to the axial extension of the taylor expansion fan. (In lab-scale equipment of up to 5 m length a section of about 3 pipe diameters from the blind flange back into the pipe is affected, in longerpipes this section increases).
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 58
Detonation pressures Pdet in long pipes (L >> Lpredet, no precompression)
Reflected pressure, if DDT occurs directly in front of blind flange (a very rare case!)
2 ≤ Freflec ≤ 2.5
Side-on pressure at location where Deflagration-to-Detonation transition (DDT) occurs
flame front of initialdeflagration has accelerated
to a very high speed
first occurrence of ignitionby adiabatic compressionin precompressed mixture; generation of shock front coupled with flame front, propagating leftwards
location ofignition
Pdet = Pinitial * PCJ * FDDT * Freflec
1.5 ≤ FDDT ≤ 2Pdet = Pinitial * PCJ * FDDT
flame front of initialdeflagration has accelerated
to a very high speed first occurrence of ignitionby adiabatic compressionin precompressed mixture;generation of shock front coupled with flame front, propagating leftwards
1.5 ≤ FDDT ≤ 2
(continued)
Important:The pipe directly ahead of the blind flangeexperiences the reflected pressure as well. Thelength of this section corresponds to the axial extension of the taylor expansion fan. (In lab-scale equipment of up to 5 m length a section of about 3 pipe diameters from the blind flange back into the pipe is affected, in longerpipes this section increases).
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 59
Chapman-Jouguet pressure ratios PCJ calculated by STANJAN
Solid lines:Calculated Chapman-Jouguetpressure ratios for pinitial = 5 bar abs(by Prof. M. Braithwaite withsoftware package STANJAN)
0
10
20
30
40
0 2 4 6 8 10 12 14 16 18 20Propene conc. in stoich. Propene/O2/N2-mixture [vol.-%]
pcj/p
initi
al
(Cha
pman
-Jou
guet
pre
ssur
e di
vide
d by
pin
itial)
0
5
10
15
20
pex/
p ini
tial (
defla
grat
ion
pres
sure
ra
tio)
calculated Pcj/Pinitial at 5 bar abs, 25°Cmeasured defl. pr.-ratios Pex/Pinitial at 5 bar abs, 25 °C
0
10
20
30
40
50
0 10 20 30 40 50 60 70 80Propene concentration in Propene/O2-mixture [vol.-%]
p cj/p
initi
al
(Cha
pman
-Jou
guet
pre
ssur
e di
vide
d by
pin
itial
)
0
5
10
15
20
25
p ex/p
initi
al (d
efla
grat
ion
pres
sure
ra
tio)
Pcj/Pinitial at 5 bar abs, 25 °CPcj/Pinitial at 5 bar abs, 200°Cmeasured defl. pr.-ratios Pex/Pinitial at 5 bar abs, 25°Cmeasured defl. pr.-ratios Pex/Pinitial at 5 bar abs, 200°C
Symbols: Measured deflagration pressureratios (scale on right side of plots)
The values are just about half of theChapman-Jouguet pressure ratios!!
PC
J(C
hapm
an-J
ougu
etpr
essu
rera
tio)
PC
J(C
hapm
an-J
ougu
etpr
essu
rera
tio)
Example: Propene/O2/N2
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 60
0
5
10
15
20
0 5 10 15 20Methane concentration in Methane/air-mixture [vol.-%]
PCJ
Cha
pman
-Jou
guet
det
onat
ion
pres
sure
rat
io
5 bar abs, 25 °C5 bar abs, 200 °C
Chapman-Jouguet pressure ratios PCJ calculated by STANJAN
0
5
10
15
20
25
30
35
0 10 20 30 40 50 60 70 80Methane concentration in Methane/O2-mixture [vol.-%]
pcj/p
initi
al
(Cha
pman
-Jou
guet
pre
ssur
e di
vide
d by
Pin
itial
)
0
2,5
5
7,5
10
12,5
15
17,5
p ex/p
initi
al (d
efla
grat
ion
pres
sure
ra
tio)
calculated Pcj/Pinitial at 5 bar abs, 25 °Ccalculated Pcj/Pinitial at 5 bar abs, 200 °Cmeasured defl. Pr.-ratios Pex/Pinitial at 5 bar abs, 25°Cmeasured defl. Pr.-ratios Pex/Pinitial at 5 bar abs, 200°C
PC
J(C
hapm
an-J
ougu
etpr
essu
rera
tio)
PC
J(C
hapm
an-J
ougu
etpr
essu
rera
tio)
Example: Methane/O2/N2
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 61
Chapman-Jouguet pressure ratios PCJ calculated by STANJAN
0
5
10
15
20
0 10 20 30 40 50 60 70 80 90 100H2 concentration in H2/O2-mixture [vol.-%]
p cj/p
initi
al
(Cha
pman
-Jou
guet
pre
ssur
e di
vide
d by
pin
itial
)
0
2,5
5
7,5
10
p ex/p
initi
al d
efla
grat
ion
pres
sure
ra
tio)
calculated detonation pr.-ratios PCJ/P initial at 1 bar abs, 20°C
calculated detonation pr.-ratios PCJ/P initial at 5 bar abs, 20°C
calculated detonation pr.-ratios PCJ/P initial at 5 bar abs, 200°Cmeasured pex/pinitial at 1 bara bs, 20 °C
0
5
10
15
20
0 10 20 30 40 50 60 70 80H2 concentration in H2/Air-mixture [vol.-%]
pcj/p
initi
al
(Cha
pman
-Jou
guet
pre
ssur
e di
vide
d by
pin
itial
)
0
2,5
5
7,5
10
p ex/p
initi
al d
efla
grat
ion
pres
sure
ra
tio)
calculated detonation pr.-ratios PCJ/Pinitial at 1 bar abs, 20°Ccalculated detonation pr.-ratios PCJ/Pinitial at 5 bar abs, 20°Ccalculated detonation pr.-ratios PCJ/Pinitial at 5 bar abs, 200°Cmeasured pex/pinitial at 1 bar abs, 20 °Cmeasured pex/pinitial at 5 bar abs, 20 °Cmeasured pex/pinitial at 5 bar abs, 200°C
Example: H2/O2/N2
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 62
Chapman-Jouguet pressure ratios PCJ calculated on basis of detonation velocity
Remarks:For using STANJAN various thermodynamic parameters of the reaction componentsmust be known. If these are not available, the detonation velocity is experimentallyeasily aminable with high precision by recording the side-on pressure of thepropagating detonation at different axial locations in the pipe with piezoelectricpressure sensors. Since the absolute signal value, which is actually the quantity oneis looking for, is often prone to errors, one has to use the „bypass“ over the speed.
PCJ = pdet /pinitial = (γ *M2+1)/(γ+1)
≈ (γ * M2)/(γ+1)
= (D2 * MW)/(R*Tinitial*(γ+1))
= ρ/pinitial * D2/(γ+1)
M = D/c Mach numberD propagation speed of detonation [m/s]c = (γ * pinitial /ρ)0.5 speed of sound in the unreacted gas mixture [m/s]ρ density of unreacted gas mixture [kg/m3]MW mean molar mass of unreacted gas mixture [kg/mol]R=8.314 universal gas constant [J/(mol*K)]γ cp/cv, for diatomic gases γ = 1.4 Tinitial , pinitial initial temperature [K], initial pressure [Pa] of gas mixturepdet side on pressure of stable detonation
meaning of symbols:
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 63
General remarks on Chapman-Jouguet pressure ratios PCJ
Chapman-Jouguet pressure ratios can be calculated by e.g. STANJAN (freeware, STANJAN Chemical Equilibrium Solver v4.01, Stanford University 2003)
Chapman-Jouguet pressure ratios are with good precision twice as high as the explosion pressure ratio found for deflagrative explosion:
Chapman-Jouguet pressure ratio is inversely proportional to the absolute initialtemperature. (Propagation speed of detonation is almost independent of Tinitial !)
If thermodynamic quantities required by STANJAN are not available for all components of the considered explosive gas mixture, PCJ can be calculated on the basis of the experimentally determined detonation speed.
- stoichiometric combustible/air- mixtures at 20°C: 16 ≤ PCJ ≤ 20 - stoichiometric combustible/O2-mixtures at 20 °C: 30 ≤ PCJ ≤ 50
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 64
Example: bulging out of a pipe end due to reflected pressure
Experiment:Acetylene, 8 bar abs, 20 °C, pipe220.9 x 8.2, i.e. φi = 204.5 mm, material: St35.8, Rp0.2 = 230 N/mm2, PRp0.2=184 bar, L = 8 m, detonativeignition source to reduce run-up distance;side-on pressure ca. 400 bar,reflected pressure ca. 800 bar
Increase of tube diameter directly in front of blind flange to 117 % of original value
no increase in diameter in the section that has only been exposed to the side-on pressure
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 65
Example: Rupture of pipe end due to reflected pressure
Experiment:Ethylene/air stoichiometric, 17 bar abs, 20 °C, pipe 76.1 x 2.6, i.e. φi = 70.9, material: 1.4541, Rp0.2 = 210 N/mm2, PRp0.2=154 bar, L = 8 m;side-on pressure ca. 340 bar,reflected pressure ca. 765 bar
increase in diameter to 105 % of original value in the section that has only been exposed to the side-on pressure
end of tube, which was exposed to the reflected pressure, is fragmented
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 66
Example: bulging out of a pipe wall due to theextra pressure at the point where the DDT occurs
Localized bulging of tube is attributed to the location of the deflagration to detonation transition
Experiment:Acetylene, 24 bar abs, 20 °C, pipe 3.17 x 0.5, φi = 2.17 mm, material: 1.4541, Rp0.2 ≥ 250 N/mm2, PRp0.2 ≥ 1152 bar, kaltgezogen, L = 10 m
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 67
Explosion characteristics
Introduction
Course of explosion in 20 l sphere
Comparison: detonative regimesin 20 l vessels ↔ 100, 500, 2500 l vessels
Predetonation distances of Propene/O2 in tubes
Pressure load Pdet on the wall of the vessel- quantification of Pdet for four scenarios occuring in a pipe (no precompression)- quantification of Pdet for four scenarios occuring in a pipe (with precompression)- quantification of Pdet for Propene/O2/N2 in vessel at Pinitial = 5 bar abs, Tinitial = 20 °C
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 68
How does precompression („pressure piling“) come into existence?
During the initial deflagrative stage of the explosion each volume element thatreacts through expands by a factor equal to the explosion pressure ratio at theexpense of the volume available for the yet unreacted mixture.
If this volume is large compared to the volume occupied by the reaction gasesformed during initial deflagrative stage, the pressure in the yet unreactedmixture will almost stay the same as at the moment of ignition (P = Pinitial).
However, if this volume is small, the yet unreacted mixture will beprecompressed. When the deflagration to detonation transition then occurs, thedetonation will not propagate in a mixture at pressure P = Pinitial, but at P = Fprecomp * Pinitial
Fprecomp may attain any value between 1 and the explosion pressure ratio of thegas mixture (up to 10 for combustible/air-mixtures, up to 24 for combustible/O2-mixtures).
The temperature rise that comes along with the fast and hence adiabaticcompression will slightly alleviate the detonative pressure Pdet. This isaccounted for by the Factor Ftemp (details see next slide)
In the formulae given beforehand for Pdet, Fprecomp and Ftemp will appear as additional factors
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 69
Temperature factor Ftemp
The temperature factor Ftemp accounts for the reduction of the Chapman-Jouguetpressure ratio due to the rise in temperature of the unburned mixture broughtabout by the precompression during the initial deflagrative stage of the explosion.
I: Temperature Tfinal of unburned mixture attained by adiabatic compression:
( )
γγγ
γ)1(
1−
−
⋅=⎟⎠⎞
⎜⎝⎛⋅= precompinitial
initial
finalinitialfinal FTp
pTT
II: Chapman-Jouguet pressure ratio is inversely proportional to the temperature thegas mixture exhibits at the moment of detonation (here denoted by Tfinal).
with: γ = cp/cv (γ = 1.4 for ideal gases)
Ftemp results from the combined effect of I: and II:
γγ )1(
1−
⎟⎟⎠
⎞⎜⎜⎝
⎛==
precompfinal
initialtemp FT
TF
Tinitial = temperature at moment of ignition
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 70
Temperatures obtainable by adiabatic compression
152,3299,0462,0638,250
148,2289,0444,3611,245
143,7278,1425,1582,040
138,7266,0403,9550,035
133,0252,3380,3514,530
126,3236,6353,4474,525
118,3218,0321,9428,420
114,6209,4307,6407,618
110,4200,0292,1385,016
105,8189,6274,9360,414
100,5177,9255,8333,112
94,4164,4234,0302,310
87,0148,4208,5266,88
77,7128,7177,6224,26
65,0102,5137,3169,84
44,461,576,790,32
36,245,854,261,61,5
30,034,237,840,91,2
γ = 1,1γ = 1,2γ = 1,3γ = 1,4
Tfinal [°C] for different values of γ = cp/cvPfinal/Pinitial
Tinitial = 25 °C = 298 K
( )γ
γ 1−
⎟⎠⎞
⎜⎝⎛⋅=
initialfinal
initialfinal pp
TTFormula for temperature increase due to adiabatic compression:
402,0634,9893,61173,450
395,6619,1865,61130,545
388,5601,7835,11084,040
380,5582,5801,41033,235
371,4560,8763,9977,030
360,8535,8721,2913,525
348,1506,3671,3840,220
342,1492,7648,6807,218
335,6477,8623,9771,516
328,2461,3596,7732,414
319,9442,7566,3689,112
310,1421,3531,7640,210
298,4395,9491,3583,88
283,7364,6442,2516,26
263,5322,9378,3429,94
230,8257,9282,0303,62
217,8233,1246,4258,11,5
207,9214,6220,3225,31,2
γ = 1,1γ = 1,2γ = 1,3γ = 1,4
Tfinal [°C] for different values of γ = cp/cvPfinal/Pinitial
Tinitial = 200 °C = 473 K
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 71
Example 1: precompression in a pipe
P3 P1
P2
first occurrencedetonation front
flame front of initialdeflagration
hot reaction products
precompressedunburned gas mixture
If the pipe is only slightly longer than the predetonation distance, the unburnedgas which is remaining at the moment when the DDT occurs may have beenprecompressed by a factor Fprecomp by the initial deflagrative stage of thecombustion.
Fprecomp may attain any value between 1 and the explosion pressure ratio of thegas mixture (up to 10 for combustible/air-mixtures, up to 24 for combustible/O2-mixtures).
The temperature rise that comes along with the fast and hence adiabaticcompression will slightly alleviate the detonative pressure Pdet. This isaccounted for by the Factor Ftemp
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 72
hot, gaseousreaction products
deflagrativeflamefront
Location of ignition
pipe, slightly longer than Lpredet
vessel
Precompressed, unburned gas mixture
Example 2: precompression in the vessel-pipe configuration
If in the vessel the DDT does not happen because of the unfavourable L/D-ratioand if the volume of the pipe is small compared to the volume of the vessel, theprecompression factor may come close to the highest possible value, i. e. theexplosion pressure ratio.The highest possible value is usually not attained, because the available time istoo short to pressurize the pipe up to the same pressure as in the vessel.
This configuration occurs frequently in practical applications, because vesselsoften have nozzles onto which short pipe segments with a block valve arewelded.
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 73
Example 3: precompression in empty vessels(i.e. without packing inside)
hot reactionproducts
First occurrence of detonation front
Flamefront of initial deflagration
Precompressed, unburned mixture
Location of ignition
vessel (here spherical, L/D = 1)
If there is a transition from deflagration to detonation in the vessel, precompression will almost always occur, because the diameter is usually notmuch larger than the predetonation distance. The precompression factormay attain the highest possible value, i. e. the explosion pressure ratio.
Reference: GCT report 105.0428.3N, 106.0104.3I
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 74
Detonation pressures Pdet in pipes with precompression (1/2)
detonationfront
pressure sensor,flush with inner surface of wall
Side-on pressure (i. e. in plane perpendicular to shockfront)
Reflected pressure (i. e. in plane parallel to shockfront, e. g. blind flange)
detonationfront
pressure sensor,flush with inner surface of flangel
Important:about 3 pipe diameters from the blind flangeback into the pipe this higher pressure also acts on the wall of the pipe!
Pdet = Pinitial * PCJ* Fprecomp * Ftemp
Pdet = Pinitial * PCJ * Freflec* Fprecomp * Ftemp
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 75
Detonation pressures Pdet in pipes with precompression (2/2)
Reflected pressure, if DDT occurs directly in front of blind flange (a very rare case!)
Side-on pressure at location where Deflagration-to-Detonation transition (DDT) occurs
flame front of initialdeflagration has accelerated
to a very high speed
first occurrence of ignitionby adiabatic compressionin precompressed mixture; generation of shock front coupled with flame front, propagating leftwards
location ofignition
Pdet = Pinitial * PCJ * FDDT * Freflec * Fprecomp * Ftemp
Pdet = Pinitial * PCJ * FDDT * Fprecomp * Ftemp
flame front of initialdeflagration has accelerated
to a very high speed first occurrence of ignitionby adiabatic compressionin precompressed mixture;generation of shock front coupled with flame front, propagating leftwards
Important:about 3 pipe diameters from the blind flangeback into the pipe this higher pressure also acts on the wall of the pipe!
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 76
Detonation pressure Pdet acting on the wall of a vessel (almostalways with precompression)
x Chapman-Jouguet pressure ratio of the mixture at the temperaturethe mixture exhibits at the moment of ignition (PCJ)
x Precompression factor (FPrecomp)
Initial pressure in vessel at moment of ignition (Pinitial)
x Temperature factor (FTemp)
x Factor accounting for reflection of stable detonation at wall (Freflec )
Pdet =
x Factor accounting for extra pressure if DDT happens directlybefore wall (FDDT), otherwise factor is 1
Pdet = Pinitial * PCJ * Fprecomp * Ftemp * Freflec * (FDDT or 1, depending on where DDT happened)
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 77
Example: Rupture of the wall of a pipe installed in thevessel-pipe configuration due to precompression
Pinitial = 25 bar abs,Tinitial = 250 °C
99.5 vol.-% N2O0.5 vol.-% Tetradecane
Ignition in center of sphere
20 l sphere
closed Valve(to vacuum pump)
10x2 pipe (1.4541)rupture pressure in hydraulic test: 3480 bar
rupture at locationof DDT in precompressedmixture
detonation in thissection,outer diameteris 102 % to 110 % of original value
only deflagrationin this section,outer diameteris not increased
Rest of the bendhas been burnedoff by outflowinghot reaction gases
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 78
Explosion characteristics
Introduction
Course of explosion in 20 l sphere
Comparison: detonative regimesin 20 l vessels ↔ 100, 500, 2500 l vessels
Predetonation distances of Propene/O2 in tubes
Pressure load Pdet on the wall of the vessel- quantification of Pdet for four scenarios occuring in a pipe (no precompression)- quantification of Pdet for four scenarios occuring in a pipe (with precompression)- quantification of Pdet for Propene/O2/N2 in vessel at Pinitial = 5 bar abs, Tinitial = 20 °C
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 79
Precompression factors Fprecomp in the heat explosion and detonative range of explosion diagrams of Propene/O2/N2 at 5 bar abs, 25 °C and 200 °C
0
5
10
15
20
25
0 10 20 30 40 50
Propene concentration in Propene/O2-mixture [vol.-%]
phea
t_in
itial
/pin
itial
or p
det_
initi
al/p
initi
al 5 bar abs, 25 °C
5 bar abs, 200 °C
orange filled symbols: heat explosionblue and red symbols: detonation
0
5
10
15
0 5 10 15 20Propene conc. in (Propene:O2=1:4.5)/N2-mixture [vol.-%]
phea
t_in
itial
/pin
itial
or p
det_
initi
al/p
initi
al 5 bar abs, 25 °C
5 bar abs, 200 °C
Propene/O2-mixture stoichiometric Propene/O2/N2-mixture(Propene:O2=1:4.5)
Note: on stoichiometric line at 200 °C only deflagration for one test with 7.8 vol.-% Propene
F pre
com
p
F pre
com
p
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 80
Upper limit for precompression factors
The precompression factors attain at maximum the deflagration pressure ratio!
0
5
10
15
20
25
0 10 20 30 40 50 60 70 80 90Propene concentration in Propene/O2-mixture [vol.-%]
p ex/p
initia
l
1 bar abs, 25 °C5 bar abs, 25 °C10 bar abs, 25 °C1 bar abs, 200 °C5 bar abs, 200 °C10 bar abs, 200 °C
18.1
8 vo
l.-%
: sto
ichi
omet
ric c
ompo
sitio
n fo
r C
3H6 +
4.5
O2 -
> 3
CO
2 + 3
H2O
25 v
ol.-%
: sto
ichi
omet
ric c
ompo
sitio
n fo
r C
3H6 +
3 O
2 ->
3 C
O +
3 H
2O
40 v
ol.-%
: sto
ichi
omet
ric
com
posi
tion
for
C3H
6 + 1
.5 O
2 ->
3 C
O +
3 H
2
Example for Propene/O2-mixtures:
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 81
Example: Detonative pressure pulses Pdet acting on the wall of a 20 l sphere in case of Propene/O2/N2, Pinitial = 5 bar abs, Tinitial = 25°C
Pressure at border line ofdetonative range about factor6 to 17 larger than in centerbecause of precompression.
The highest value attainableby Pdet/Pinitial is about 1300 !!
barabsbarabsP 203975.125.210110205
4.1)14.1(
det =⋅⋅⎟⎠⎞
⎜⎝⎛⋅⋅⋅=
−
0 10 20 30 40 50 60 70 80 90 100Propene C H [Vol.-%]3 6
0
10
20
30
40
50
60
70
80
90
100
O [Vol.-%
]
2
0
10
20
30
40
50
60
70
80
90
100
N
[Vol
.-%]
2
range of deflagrative explosion, 5 bar abs, 25 °C
range of detonative
explosion
stoich
iometric
CH + 1.5
O -> 3 CO + 3
H
36
2
2
stoich
iometr
ic C
H +
3 O ->
3 CO +
3 HO
36
2
2
stoich
iometr
ic C
H +
4.5 O
-> 3
CO +
3 H
O
36
2
2
2
propene/air-mixtures
barabarabsP 669275.125.220120405
4.1)14.1(
det =⋅⋅⎟⎠⎞
⎜⎝⎛⋅⋅⋅=
−
barabsbarabsP 495125.2111445
4.1)14.1(
det =⋅⋅⎟⎠⎞
⎜⎝⎛⋅⋅⋅=
−
barabsbarabsP 332075.125.213113275
4.1)14.1(
det =⋅⋅⎟⎠⎞
⎜⎝⎛⋅⋅⋅=
−
barabsbarabsP 416125.2111375
4.1)14.1(
det =⋅⋅⎟⎠⎞
⎜⎝⎛⋅⋅⋅=
−
barabsbarabsP 1627125.2414475
4.1)14.1(
det =⋅⋅⎟⎠⎞
⎜⎝⎛⋅⋅⋅=
−
barabsbarabsP 385125.21.1
11.13254.1
)14.1(
det =⋅⋅⎟⎠⎞
⎜⎝⎛⋅⋅⋅=
−
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 82
Summary concerning pressure load
The „obscure“ effects talked about in non-public communication seem to beexplainable with precompression
Pressure at the border line of detonative range about factor 6 to 17 larger than in center because of precompression!(I.e. in the detonative regime the lowest pressure load on the wall isgenerated by mixtures in the vicinitiy of the stoichiometric combustible/O2-mixtures)
Since in the empty vessel the static equivalent pressure Pstat of thedetonative pressure pulse Pdet is at least 0.5*Pdet, the lower limit for therequired pressure resistance of a detonation pressure proof empty vessel isknown. Since this lower limit is extremely high,it is questionable whether the designof a detonation pressure proof empty vessel is economically justifiable.
Pressures acting on the wall may be a factor 1300 higher than the initialpressure in the mixture. The main reason is that in vessels the highesttheoretically possible precompression factors (=deflagration pressure ratios) actually do occur !!
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 83
Explosion characteristics
Introduction
Course of explosion in 20 l sphere
Comparison: detonative regimesin 20 l vessels ↔ 100, 500, 2500 l vessels
Predetonation distances of Propene/O2 in tubes
Pressure load Pdet on the wall of the vessel- quantification of Pdet for four scenarios occuring in a pipe (no precompression)- quantification of Pdet for four scenarios occuring in a pipe (with precompression)- quantification of Pdet for Propene/O2/N2 in vessel at Pinitial = 5 bar abs, Tinitial = 20 °C
Did ignition source directly trigger a spherical detonation?
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 84
Vessels used for the experiments
100 l vessel: L = 1309 mm; φi = 327.2 mm; L/ φi =4.0; distance P1-P3 = 1343 mm
500 l vessel: L = 2146 mm; φi = 570 mm; L/ φi =3.76; distance P1-P3 = 2309 mm
2500 l vessel: L = 3644 mm; φi = 956 mm; L/ φi =3.8; distance P1-P3 = 3866 mm
Characteristic parameters of all vessels:
Sketch of 2500 l vessel (the others are alike, only smaller):
s = 34 wal
l th
ickn
ess
s =
30
346
175
4021
3040 (cylindirical section)3718
s = 40
332128
3866
P2
1938
loca
tion
of ig
nitio
nw
eld
neck
flan
geN
W15
0, P
N16
0
wel
d ne
ck fl
ange
NW
300,
PN
160
torospheri-cal head
torospheri-cal head
oute
r dia
met
er φ
o = 1
016
inne
r dia
met
er φ
i = 9
56
1928
P1 P3L = 3644
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 85
Examples for pressure/time recordings by sensor P3 in 100 l and 500 l vessel
65 70 75 80 85 900
100
200
300
400
500
Time [ms]
Pres
sure
[bar
abs
]
File: EFOV108K.DAT
Experiment:Ethane=22.2 vol.-%, O2=77.8 vol-%, Pinitial = 5 bar abs,Tinitial = 25 °C,100 l vessel, L/D = 4
v = Δs/Δt = (2*1.343m)/2 ms = 1343 m/s
Δt = 2ms
65 70 75 80 85 900
250
500
750
1000
Time [ms]
Pres
sure
[bar
abs
]
File: EFOV150K.DAT
Experiment:Ethane=11.4 vol.-%, O2=40 vol.-%, N2=48.6 vol.-%,Pinitial = 8 bar abs,Tinitial = 25 °C,500 l vessel, L/D = 3.8Δt = 3.66ms
v = Δs/Δt = (2*2.309m)/3.66ms = 1261m/s
The peaks are due to the shockwave of the detonation which after having reached the one end of the vessel is reflected backwards into the hot reaction gas, travels until reaching the opposite torospherical head of the vessel, is again reflected and so on
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 86
Results of tests with stoichiometric Ethane/O2/N2-mixtures in vessels ranging from 20 l to 2500 l
heat explosion35
detonativedetonative40
deflagrativedeflagrative30
2500 l cylinder, L/D=3.8
20 l sphere
course of explosionO2-conc. in stoichiometricmixture [vol.-%]
detonative
deflagrative
500 l cylinder, L/D=3.76
detonative35
detonativedetonative40
deflagrativedeflagrative30
100 l cylinder, L/D=4
20 l sphere
course of explosionO2-conc. in stoichiometricmixture [vol.-%]
Tests with Pinitial = 8 bar abs
Tests with Pinitial = 4 bar abs
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 87
Summary of comparison of explosive regimes of combustible/O2/N2 mixtures in vessels of different volume
For stoichiometric mixtures there is - within experimental accuracy -no change in the critical composition (transition from deflagrative to detonative combustion) when varying the vessel volume over twoorders of magnitude !!!
For combustible/O2 mixtures the potential change of the criticalcompositions with vessel volume could not yet be studied.
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 88
Explosion characteristics
Introduction
Course of explosion in 20 l sphere
Comparison: detonative regimesin 20 l vessels ↔ 100, 500, 2500 l vessels
Predetonation distances of Propene/O2 in tubes
Pressure load Pdet on the wall of the vessel- quantification of Pdet for four scenarios occuring in a pipe (no precompression)- quantification of Pdet for four scenarios occuring in a pipe (with precompression)- quantification of Pdet for Propene/O2/N2 in vessel at Pinitial = 5 bar abs, Tinitial = 20 °C
Did ignition source directly trigger a spherical detonation?
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 89
Experimental setup to determine predetonation distancesof Propene/O2-mixtures in a φi = 76.3 mm pipe at pinitial = 5 bar abs, 25°C
location ofthermal ignitionsource
2000 2000 2000 1000
(the lengths of the tube segments are specified as from centre of gasket to centre of gasket,i. e. the actual tubes are slightly less than 1000 mm or 2000 mm, respectively)
7000 mm, PN160, DN80, = 88.9 mm, = 76.3 mm, s = 6.3 mmφ φo i
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 90
Position of pressure sensors in the φi = 76.3 mm pipe
P10 P11 P12 P13 P14 P15 P16250
500 750
1000 1250
1500 1750
2000
P17
1000
2000
P17
1000
2000
P1
100
P2 P3 P4 P5 P6 P7 P8 P9
200 300
400
100 100 100 100 100
1000
location ofthermal ignition source
P10 P11 P12 P13 P14 P15 P16250
500 750
1000 1250
1500 1750
2000
P1
100
P2 P3 P4 P5 P6 P7 P8 P9
200 300
400
100 100 100 100 100
1000
location ofthermal ignition source
Enlarged section of first two pipe segments:
Pressure sensors used (all piezoelectric, supplied by PCB):PCB M112A05, 0 - 345 bar, ca. 16 pC/barPCB M113A03, 0 - 1034 bar, ca. 5 pC/barPCB M119A11, 0 - 5520 bar, ca. 3.6 pC/bar
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 91
Predetonation distances of Propene/O2 in a φi = 76.3 mm pipe at 5 bar abs, 20 °C
Note: in 7 m long pipe with φi = 76.3 mm no DDT for Propene conc. ≤4 vol.-% (i.e. predet.distance > L/D=92)in 11 m long pipe with φi = 86 mm no DDT for Propene conc. ≥50 vol.-% (i.e. predet.distance > L/D=127)
Propene concentration in Propene/O2-mixture [vol.-%]0 10 15 20 25 3530 40 45 505
DDT deflagrationCourse of explosion in 20 l sphere, φi = 340 mm:
defl.heat expl. (?)
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20 25 30 35 40 45 50Propene concentration in Propene/O2- mixture [vol.-%]
Pred
eton
atio
n di
stan
ce
[leng
th/d
iam
eter
]
Predetonation distances of Propene/O2at 5 bar abs, 20°C; in 7 m long tube,76.3 mm internal diameter.
18.1
8 vo
l.-%
is s
toic
hiom
etric
for C
O2
and
H2O
form
atio
n
25 v
ol.-%
is s
toic
hiom
etric
for C
O a
nd H
2O fo
rmat
ion
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 92
Predetonation distances of stoichiometric Propene/O2/N2 in a φi = 76.3 mm pipe at 5 bar abs, 20 °C
0
10
20
30
40
50
60
70
80
90
100
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20Propene concentration in stoich. Propene/O2/N2- mixture [vol.-%]
Pred
eton
atio
n di
stan
ce [l
engt
h/di
amet
er]
Predetonation distances of stoich. Propene/O2/N2(for CO2- and H2O-formation) at 5 bar abs, 20°C;in 7 m long tube, 76.3 mm internal diameter.
Propene concentration in stoichiometric Propene/O2-mixture [vol.-%]
DDTdeflagrationCourse of explosion in 20 l sphere, φi = 340 mm:
heat expl. (?)
0 4 6 8 10 1412 16 18 202 3 5 7 9 1311 15 17 191
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 93
Example for how to determine the predetonation distance in pipes from pressure/time diagramsExample: Propene/O2, 5 bar abs, 20 °C, 41 vol.-% Propene, φi=76 mm, L = 7 m, ignition at t = 0 ms
11 11.5 12 12.5 13 13.5 140
50100150200
500 mm
11 11.5 12 12.5 13 13.5 140
50100150200
800 mm
11 11.5 12 12.5 13 13.5 140
50100150200250300
1250 mm
11 11.5 12 12.5 13 13.5 140
100200300 1500 mm
11 11.5 12 12.5 13 13.5 140
200400600800
1750 mm
11 11.5 12 12.5 13 13.5 140
200400600800
2000 mm
11 11.5 12 12.5 13 13.5 140
100200300400
Time [ms]
6000 mm
pressure sensor defect
v = s/ t=4.25m/1.64ms=2591m/sΔ Δ
v = s/ t=0.25m/0.1ms=2500m/sΔ Δ
reto
natio
n pe
ak p
ropa
gatin
g ba
ckw
ards
Pre
ssur
e[b
ar a
bs]
Predetonation distance is given byintersection of distance-time curve of retonation and detonation wave. (in this example: Lpredet = 1560±50 mm)
P3 P4 P5 P6 P7P1 P2
location ofthermal ignition source
1250 500 800 1500 1750 2000 6000 5000 4000 7000 1000
11,5
11,75
12
12,25
12,5
12,75
13
13,25
13,5
0 1000 2000 3000 4000 5000 6000 7000Distance of pressure sensor from ignition source (left blind flange) [mm]
Tim
e of
arr
ival
of r
eton
atio
n or
det
onat
ion
wav
e [m
s]
Detonation wave, v = 2591 m/s
Retonation wave, v = 1612 m/s
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 94
Clarification of an apparent contradiction with respectto predetonation distances
Lean mixtures that require up to 760 mm (L/D ≅ 10) predetonation distance in a pipe andrich mixtures that require up to 1500 mm (L/D ≅ 20) predetonation distance in a pipe
manage to run up to detonation in a sphere with radius 170 mm !!!
Possible reasons that mixture detonates in sphere although in pipe lpredet >> radius of sphere:- In the sphere there is massive precompression (up to factor of 12 on lean side and up to a factor of 20 on rich side of detonative range) which is absent in long pipes. Predetonation distances reduce with increasing pressure (see next slide).
- In sphere sonic pressure waves of initial deflagration are reflected backwards and interfere with combustion zone, which might accelerate the flame. In long pipes this effectshould almost be absent.
At first glance this is an unexpected result: In the pipe the unburnt gas is made stream turbulent between rigid walls by expansion of thereaction products. This should encourage flame acceleration.Hence, if for some mixture the predetonation distance in a pipe is larger than the radius of thesphere, one would not expect this mixture to run up to detonation in the sphere.
- Because precompression in the sphere is adiabatic, the temperature of the mixture risessubstantially (see next slide). Possibly this also contributes to reducing the predetonationdistance (????)
- Based on the precompression difference between lean and rich side it qualitatively makessense that on the rich side mixtures which exhibit about twice the predetonation distance in a pipe as mixtures on the lean side, still run up to detonation in the sphere
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 95
Predetonation distances as function of initial pressure
1 10
0.1
1
initial pressure P [bar abs]initial
pred
eton
atio
n di
stan
ce s
[m]
D5
2
3
0.5
0.2
0.3
0.05
0.03
m = 0.43
m = 0.50
m = 0.61
m = 0.76
502 30203 50.2 0.3 0.5
H + N O, 38 °C, = 79 mm
2
2
iφ
H + O , 37.7 °C, = 15 mm
2
2
iφ
m = 0.76
H + O , 200 °C, = 15 mm
2
2
iφ
C H + 4 O
, 37.7 °C, = 15 mm
22
2
iφ
CH + 5.67 O , 40 °C = 15 mm
4
2
iφ
2 CO + O , 40 °C, = 15 mm
2
iφ
m = 1
m = 0.057C H + air, 20 °C, stoichiom., = 50 mm
2 4iφ
s = D
const.(P )ini
m
Empirical law for thepressure dependence of the predetonation distance:
H + O , 200 °C, = 15 mm, L = 2.94 m 2 2 iφ
H + O , 37.7 °C, = 15 mm, L = 2.94 m 2 2 iφ
H + N O, 37.7 °C, = 79 mm , L = 2.94 m (L.E. Bollinger, J. A. Laughrey and R. Edse, American Rocket Society: ARS Journal (Easton, Pa) 32, p. 81 - 82 (1962)
2 2 iφ
CH + 5.67 O , 40 °C = 15 mm, L = 2.94 m 4 2 iφ
2 CO + O , 40 °C, = 15 mm, L = 2.94 m 2 iφ
C H + 4 O , 37.7 °C, = 15 mm, L = 2.94 m 2 2 2 iφ
L.E. Bollinger, M. C. Fong and R. Edse, American Rocket Society: ARS Journal (Easton, Pa) 31, p. 588 - 595 (1961) }
C H + air, 20 °C, stoichiom., = 50 mm, L = 22 m (I. Ginsburg and W. L. Bulkley, Chemical Engineering Progress, Vol. 59, no. 2, p. 82 - 86 (1963)
2 4 iφ
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 96
Temperatures obtainable by adiabatic compression
152,3299,0462,0638,250
148,2289,0444,3611,245
143,7278,1425,1582,040
138,7266,0403,9550,035
133,0252,3380,3514,530
126,3236,6353,4474,525
118,3218,0321,9428,420
114,6209,4307,6407,618
110,4200,0292,1385,016
105,8189,6274,9360,414
100,5177,9255,8333,112
94,4164,4234,0302,310
87,0148,4208,5266,88
77,7128,7177,6224,26
65,0102,5137,3169,84
44,461,576,790,32
36,245,854,261,61,5
30,034,237,840,91,2
γ = 1,1γ = 1,2γ = 1,3γ = 1,4
Tfinal [°C] for different values of γ = cp/cvPfinal/Pinitial
Tinitial = 25 °C = 298 K
( )γ
γ 1−
⎟⎠⎞
⎜⎝⎛⋅=
initialfinal
initialfinal pp
TTFormula for temperature increase due to adiabatic compression:
402,0634,9893,61173,450
395,6619,1865,61130,545
388,5601,7835,11084,040
380,5582,5801,41033,235
371,4560,8763,9977,030
360,8535,8721,2913,525
348,1506,3671,3840,220
342,1492,7648,6807,218
335,6477,8623,9771,516
328,2461,3596,7732,414
319,9442,7566,3689,112
310,1421,3531,7640,210
298,4395,9491,3583,88
283,7364,6442,2516,26
263,5322,9378,3429,94
230,8257,9282,0303,62
217,8233,1246,4258,11,5
207,9214,6220,3225,31,2
γ = 1,1γ = 1,2γ = 1,3γ = 1,4
Tfinal [°C] for different values of γ = cp/cvPfinal/Pinitial
Tinitial = 200 °C = 473 K
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 97
Summary on predetonation distances of Propene/O2
Predetonation distances change drastically (about 2 orders of magnitude) over a relatively narrow range of compositions
Above statements are compatible with the well establishedobservation that combustible/air mixtures do not run up to detonationin empty vessels ->>>> see next slide ->>>>>
Above result corroborates the so far preliminary conclusion drawnfrom the comparisons of the detonative regimes found in 20, 100, 500 and 2500 l vessels (detonative range in 20 l sphere about thesame as in 2500 l vessel)
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 98
Tentative generalisation of the results found for the course of theexplosion of Propene/O2/N2 in the 20 l sphere and in tubes (thermal ignition presumed!)
0 10 20 30 40 50 60 70 80 90 100Propene C H [Vol.-%]3 6
0
10
20
30
40
50
60
70
80
90
100
O [Vol.-%
]
2
0
10
20
30
40
50
60
70
80
90
100
N
[Vol
.-%]
2
range of deflagrative explosion, 5 bar abs, 25 °C
range of detonative
explosion
stoich
iometr
ic CH + 1.5
O ->
3 CO + 3 H
36
2
2
stoich
iometr
ic C
H +
3 O ->
3 CO +
3 HO
36
2
2
stoich
iometr
ic C
H +
4.5 O
-> 3
CO +
3 H
O
36
2
2
2
propene/air-mixtures
4.5 vol.-% Propenein Propene/O2
45 vol.-% Propenein Propene/O2
4.46 vol.-% Propenein Propene/air(stoichiometric)
L/D = 64
L/D = 70
L/D ca. 100(typical for
stoichiometrichydrocarbon/air)
Combustible/air-mixturesdo not detonate in vesselsof any practical size.
Propene/O2 mixtures withpredetonation distances L/D ≥ 100 do not detonate in 20 l vessel
Detonative range in larger vesselsseems to be about the same as in 20 l vessel
Predetonation distance of combustible/air-mixturesis about L/D ≥100
Propene/O2-mixtures withL/D ≥ 100 do not detonate in vessels of any practical size
Combustible air mixtures withL/D ≥ 100 do not detonate in vessels of any practical size
+
=
+
=
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 99
Explosion characteristics
Introduction
Course of explosion in 20 l sphere
Comparison: detonative regimesin 20 l vessels ↔ 100, 500, 2500 l vessels
Predetonation distances of Propene/O2 in tubes
Pressure load Pdet on the wall of the vessel- quantification of Pdet for four scenarios occuring in a pipe (no precompression)- quantification of Pdet for four scenarios occuring in a pipe (with precompression)- quantification of Pdet for Propene/O2/N2 in vessel at Pinitial = 5 bar abs, Tinitial = 20 °C
Did ignition source directly trigger a spherical detonation?
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 100
Did our the ignition source directly trigger a spherical detonation?
Ignition source used is fusing wire according to EN 1839, section 4.2.3.3.3 :
- wire of 0.2 mm diameter, ca. 5 mm long, clamped between two electrodes
- by a thyristor the wire is connected for a fraction of a half wave withthe secondary coil of an insulation transformer(thyristor typically opens between 0° and 150° and closes at 180°)
- wire melts in about first millisecond
- just when first contact breaks apart between the electrodes by the melting of the wirean arc discharge emerges and keeps on burning until the voltage between the pole tips falls back to 0.
This ignition source must be rated as purely thermal, since the shock waveassociated with the first occurrence of the arc discharge is negligible (seenext slides)
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 101
Current/time, Voltage/time and Pressure/time diagrams of ignitionsource „melting wire with subsequent arc discharge“ (1/5)
-3 -2 -1 0 1 2 3 4 5 6 70.850.9
0.951
1.051.1
1.15
Pres
sure
[bar
abs
]
File: v001_hwz-1_zw120°_1bar-n2.sbs
-3 -2 -1 0 1 2 3 4 5 6 70
100
200
300
-3 -2 -1 0 1 2 3 4 5 6 70
100
200
300
Time [ms]
Pressure at sensor in 1 cm distance of arc discharge
Current through wire and current of arc discharge
Voltage at output pin of Halbwellenzuendgeraet (about factor 7 larger than at electrode tips)
Cur
rent
[A]
Volta
ge [V
]
Example:ignited in 1 bar N2at 20°C, thyristor switched on from 120° to 180°of one half cycleof mains supply
Heating of wire untilmelting occurs
Arc dischargeis burning
Thyristor opens for 3.33 ms (120°-180° of one half wave of 50 Hz mains supply)
In about 50% of all ignitions conducted1 bar N2 at 20°C there was not at all any pressuredetected by thepiezoelectric sensor(irrespective of theduration the thyristorwas switched on)
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 102
Current/time, Voltage/time and Pressure/time diagrams of ignitionsource „melting wire with subsequent arc discharge“ (2/5)
-3 -2 -1 0 1 2 3 4 5 6 7 80.85
0.90.95
11.05
1.11.15
Pres
sure
[bar
abs
]
File: v003_hwz-1_zw5°_1bar-n2.sbs
-3 -2 -1 0 1 2 3 4 5 6 7 80
100
200
300
-3 -2 -1 0 1 2 3 4 5 6 7 80
100
200
300
Time [ms]
Cur
rent
[A]
Volta
ge [V
]Pressure at sensor in 1 cm distance of arc discharge
Current through wire and current of arc discharge
Voltage at output pin of Halbwellenzuendgeraet (about factor 7 larger than at electrode tips)
Example: ignited in 1 bar N2 at 20°C, thyristor switched on from 5° to 180° of one half cycle of mains supply
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 103
Current/time, Voltage/time and Pressure/time diagrams of ignitionsource „melting wire with subsequent arc discharge“ (3/5)
-3 -2 -1 0 1 2 3 4 5 6 719.5
19.75
20
20.25
20.5P
ress
ure
[bar
abs
]
File: v004_hwz-1_zw120°_20bar-n2.sbs
-3 -2 -1 0 1 2 3 4 5 6 70
100
200
300
-3 -2 -1 0 1 2 3 4 5 6 70
100
200
300
Time [ms]
Pressure at sensor in 1 cm distance of arc discharge
Current through wire and current of arc discharge
Voltage at output pin of Halbwellenzuendgeraet (about factor 7 larger than at electrode tips)
Cur
rent
[A]
Volta
ge [V
]
Example: ignited in 20 bar N2 at 20°C, thyristor switched on from 120° to 180° of one half cycle of mains supply
For all ignitionsconducted at 20 bar N2and at 20°C there was a pressure signaldetected by thepiezoelectric sensor of the order of Δp = ±0.4 to ±0.7 bar
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 104
Current/time, Voltage/time and Pressure/time diagrams of ignition source„melting wire with subsequent arc discharge“ (4/5)
-3 -2 -1 0 1 2 3 4 5 6 719.5
19.75
20
20.25
20.5Pr
essu
re [b
ar a
bs]
File: v006_hwz-1_zw5°_20bar-n2.sbs
-3 -2 -1 0 1 2 3 4 5 6 70
100
200
300
Cur
rent
[A]
-3 -2 -1 0 1 2 3 4 5 6 70
100
200
300
Time [ms]
Volta
ge [V
]
Pressure at sensor in 1 cm distance of arc discharge
Current through wire and current of arc discharge
Voltage at output pin of Halbwellenzuendgeraet (about factor 7 larger than at electrode tips)
Example: ignited in 20 bar N2 at 20°C, thyristor switched on from 5° to 180° of one half cycle of mains supply
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 105
Current/time, Voltage/time and Pressure/time diagrams of ignitionsource „melting wire with subsequent arc discharge“ (5/5)
-3 -2 -1 0 1 2 3 4 5 6 719.5
19.75
20
20.25
20.5
Pre
ssur
e [b
ar a
bs]
File: v004_hwz-1_zw120°_20bar-n2.sbs
-3 -2 -1 0 1 2 3 4 5 6 70
100
200
300
-3 -2 -1 0 1 2 3 4 5 6 70
100
200
300
Time [ms]
Pressure at sensor in 1 cm distance of arc discharge
Current through wire and current of arc discharge
Voltage at output pin of Halbwellenzuendgeraet (about factor 7 larger than at electrode tips)
Cur
rent
[A]
Volta
ge [V
]
-3 -2 -1 0 1 2 3 4 5 6 719.5
19.75
20
20.25
20.5
Pres
sure
[bar
abs
]
File: v006_hwz-1_zw5°_20bar-n2.sbs
-3 -2 -1 0 1 2 3 4 5 6 70
100
200
300
Cur
rent
[A]
-3 -2 -1 0 1 2 3 4 5 6 70
100
200
300
Time [ms]
Volta
ge [V
]
Pressure at sensor in 1 cm distance of arc discharge
Current through wire and current of arc discharge
Voltage at output pin of Halbwellenzuendgeraet (about factor 7 larger than at electrode tips)
-3 -2 -1 0 1 2 3 4 5 6 70.850.9
0.951
1.051.1
1.15
Pres
sure
[bar
abs
]
File: v001_hwz-1_zw120°_1bar-n2.sbs
-3 -2 -1 0 1 2 3 4 5 6 70
100
200
300
-3 -2 -1 0 1 2 3 4 5 6 70
100
200
300
Time [ms]
Pressure at sensor in 1 cm distance of arc discharge
Current through wire and current of arc discharge
Voltage at output pin of Halbwellenzuendgeraet (about factor 7 larger than at electrode tips)
Cur
rent
[A]
Volta
ge [V
]
-3 -2 -1 0 1 2 3 4 5 6 7 80.85
0.90.95
11.05
1.11.15
Pres
sure
[bar
abs
]
File: v003_hwz-1_zw5°_1bar-n2.sbs
-3 -2 -1 0 1 2 3 4 5 6 7 80
100
200
300
-3 -2 -1 0 1 2 3 4 5 6 7 80
100
200
300
Time [ms]
Cur
rent
[A]
Volta
ge [V
]
Pressure at sensor in 1 cm distance of arc discharge
Current through wire and current of arc discharge
Voltage at output pin of Halbwellenzuendgeraet (about factor 7 larger than at electrode tips)
1 ba
r N2,
120°
-180
°1
bar N
2, 5°
-180
°
20 b
ar N
2, 12
0°-1
80°
20 b
ar N
2, 5°
-180
°
H.-P. Schildberg, 41st UKELG meeting, 13 May 2008, Shell Technology Centre Thornton 106
Summary of talk
Detonative range in empty vessels is determined
Abundant set of explosion characteristics in the importantbut so far mostly unexplored combustible/air/O2 region of the explosive range
Pressure load on the wall is understood quantitatively
The link between detonation in pipes and in vessels isestablished