influence of flame characteristics on gas- phase fire
Post on 31-Dec-2021
9 Views
Preview:
TRANSCRIPT
Influence of Flame Characteristics on Gas-Phase Fire Retardant Effectiveness
Gregory Linteris, Nicolas Bouvet*, Valeri BabushokFire Science Division, Engineering Laboratory, NIST
Fumiaki TakahashiCase Western Reserve University / NASA Glenn
Viswanath KattaWright-Patterson Air Force Base / ISSI
Stanislav Stoliarov, Peter SunderlandDept. of Fire Protection Engineering, University of Maryland
* Financial support for NB from BASF
Acknowledgements:
BASF (support of Dr. Bouvet)
Past Support:NASANISTBoeingHonweywellDupontArmy, Navy, Air ForceNRCvon Humboldt Foundation)
Other People: Harsha Chelliah, UVa; Valeri Babushok, Wing Tsang, Kevin McGrattan, Don Burgess, Mike Zachariah, Marc Rumminger, Dirk Reinelt, Greg Fallon, Ivan, Tony, Cindy, Arnold, Newton, Tania, Ian, Lloyd, NIST;
Outline:
Part I: Super-effective agents in co-flow diffusion flames
Background- flame types- iron inhibition- particles
Phosphorus- status
Part II: Flame Properties Affecting Inhibition EffectivenessFlame Base CharacteristicsRandom ThoughtsClosing Thoughts
0.4
0.6
0.8
1
0 2000 4000 6000 8000 10000
Inhibitor Volume Fraction (L/L)
CF3Br
Fe(CO)5
= 1.0
Tin = 353 K(except Sn)
CO2
X = 0.21O2,ox
Nor
mal
ized
Bur
ning
Vel
ocity
Gas-phase chemical inhibitor effectiveness varies dramatically.
* From Linteris, G.T., Rumminger, M.D., Babushok, V.I. “Catalytic Inhibition of Laminar Flames by Metal Compounds,” Progress in Energy and Combustion Science, 34:288 – 329, 2008.
0.4
0.6
0.8
1
0 2000 4000 6000 8000 10000
Inhibitor (ppm)
Norm
aliz
ed B
urni
ng V
eloc
ity
CF3BrSn(CH3)4
Fe(CO)5
MMT
= 1.0
SnCl4
Tin = 353 K(except Sn)
CO2
X = 0.21O2,ox
SbCl3
Gas-phase chemical inhibitor effectiveness varies dramatically.
* From Linteris, G.T., Rumminger, M.D., Babushok, V.I. “Catalytic Inhibition of Laminar Flames by Metal Compounds,” Progress in Energy and Combustion Science, 34:288 – 329, 2008.
Premixed flameDiffusion flame
(Couterflow)
Diffusion flame (Coflow)
Fe(CO)5 : 540 100 0DMMP : 141 17 2CF3Br : 8 5 7
Effectiveness relative to CO2 :
Why?
Gas-phase chemical inhibitor effectiveness varies dramatically.
Pool Fire (from: http://www.me.uwaterloo.ca/~eweckman/fire/firehome.htm
How do we study flame inhibitors?
Too difficult to extract fundamental information:=> can’t include detailed chemistry=> grid resolution is coarse=> turbulence too complex
Premixed Flames Diffusion Flames
flame
oxidizer
Counter-flow
fuelChimney
Air + Inhibitor
Fuel
Co-flow
1-DSteadyEasy to model, well developed theoryTypically used by researchersProvide fundamental reaction rate data
2-DUnsteadyHarder to model, active area of researchWidely used in codes and stds.Has many features like real fires
Two basic types of flames :
Fuel + air+ inhibitor
Nozzle Burner
1. Experiments: - all three fundamental flames, - over wide range of controlling parameters.
2. Detailed numerical simulation- with detailed kinetic mechanisms.
3. At NIST, we - build gas-phase kinetic models,- use other people’s flame codes
Goals: 1. Understand interaction of inhibitors with flame structure.
2. Eventually model:- standard tests, - full-scale fires.
Approach
Iron is super-effective relative to CF3Br in some flames,
0.4
0.6
0.8
1
0 2000 4000 6000 8000
Inhibitor %
Flam
e St
reng
th
CF3Br
Fe(CO)5
CO2
0.80.40.20.0 0.6
Premixed flame
0.05
0.10
0.15
0 0.2 0.4 0.6 0.8
Inhibitor (%)
Flam
e St
reng
th
CF3Br
Fe(CO)5
CO2
Cup-burner flame
Use detailed modeling of the cup-burner flame to find out why.
but in others, it’s relatively ineffective. Why?
* From Linteris, G.T., Rumminger, M.D., Babushok, V.I. “Catalytic Inhibition of Laminar Flames by Metal Compounds,” Progress in Energy and Combustion Science, 34:288 – 329, 2008.
Direct Numerical Simulations for Cup-Burner Flames
• Time-dependent 2D governing equations mass, momentum, species, energy conservation, & state equations,
including a body-force term optically thin-media radiative heat losses from CO2, H2O, CH4,and CO
• Variable thermochemical/transport properties hi from polynomial curve-fits , , and D from molecular dynamics and mixture rules
• Detailed reaction mechanism (GRI-Mech v1.2) 31 species/346 reactions for CH4-O2 combustion + inert (He, Ar) 82 species/1520 reactions for CH4-O2 – F system
Adding slightly more agent causes flame to liftoff
a.) b.)
CH4-air flame, Xi < Xi|critical Xi > Xi|critical
Can predict critical volume fraction of agent for blow-off well.
OS
F
OS
Fuel 0
0.1
0.2
0.3
0.4
Br2 CF3Br CF3H Ar He N2 CO2 CO2(mg)
Volu
me
Frac
tion
for E
xtin
ctio
n
experiment
prediction
Air + inhibitor
Agent
Review: Radical reactions dominate combustion
- radical attack dominates fuel decomposition
- radical chain branching creates the radicals
- CO consumption:
H H H
H – C – C – C – H
H H H
H H H
H – C – C – C – H
H H• H + H – H
•
H + O2 OH + O• • •
CO + OH CO2 + H• •
- because of chain branching, often have super-equilibrium of radicals
How does iron inhibit flames?
FeO + H2O = Fe(OH)2Fe(OH)2 + H = FeOHFeOH + H = FeO------------------------------------------------Net: H + H = H2
Fe(OH)2
FeO
FeOH
+H
+H
+H2O
Fe(CO)5
Fe
FeO2
+O
+O2+M
Catalytic cycle
=> Gas-phase iron species recombine radicals.
0.00
0.05
0.10
0.15
0 500Fe(CO)5 Volume Fraction in Air (ppm)
Flam
e St
reng
th
0
1
2
3
4
Max
ium
u Q
vv x
105 1
/(cm
-sr)
Calc
Expt.
Predicted and measured inhibition don’t agree. => This was a surprise. It was expected to work.
From: Linteris, G.T., Katta, V.R., and Takahashi, F., “Experimental and Numerical Evaluation of Metallic Compounds for Suppressing Cup-Burner Flames,” Combustion and Flame, 138:78-96, 2004.
Iron species vapor pressures are strong f(T).
1.E-10
1.E-09
1.E-08
1.E-07
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
1.E-01
1.E+00
500 1000 1500 2000
Temperature K
Gas
-Pha
se V
olum
e Fr
actio
n
FeO
Fe
Fe(OH)2
=> potential for condensation.
From: Linteris, G.T., Katta, V.R., and Takahashi, F., “Experimental and Numerical Evaluation of Metallic Compounds for Suppressing Cup-Burner Flames,” Combustion and Flame, 138:78-96, 2004.
Use model to determine flame structure. Check for super-saturation of Fe compounds:
=> Particles: sink for active Fespecies
=> [FeO]/[FeO]sat = 103 to 105 => condensation is likely
=> Temperature at reaction kernel is low.
1.00E-10
1.00E-09
1.00E-08
1.00E-07
1.00E-06
1.00E-05
1.00E-04
1.00E-03
1.00E-02
1.00E-01
1.00E+00
2 4 6 8 10 12Radial Distance (mm)
Mol
e Fr
actio
n
400
600
800
1000
1200
1400
1600
Tem
pera
ture
(K)
XFeO
XFeO,sat
CH4O2T
10-10
10-8
100
10-6
10-4
10-2
Fe(OH)2
FeO
FeOH
+H
+H
+H2O
Catalytic cycle
Check for particles with laser scattering system
Lock-in Amp
Computer
Pre-amp L
Laser
C
M
PMT
Pre-amp
Po
G
Burner
PMT
M
F P L
S
Po
PMT
F
Lock-in Amp
IS
Lock-in Amp
Fiber
Pre-amp
LL
Bellows
Chimney
F
-20
-18
-15
-13
-11 -8 -6 -3 -1 1 4 6 9 11 13 16 18
0
3
6
9
12
15
18
-20 -15 -10 -5 0 5 10 15Radial Position (cm)
0
5
10
15
20
Ht. A
bove
Bur
ner
(cm
)
0 L/L
1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49
S1
S4
S7
S10
S13
S16
S19
S22
-20 -15 -10 -5 0 5 10 15Radial Position (cm )
0
5
10
15
20
Ht.
Abo
ve B
urne
r (c
m)
100 L/L
-20
-18
-15
-13
-11 -8 -6 -3 -1 1 4 6 9 11 13 16 18
0
3
6
9
12
15
18
-20 -15 -10 -5 0 5 10 15
Radial Position (cm)
0
5
10
15
20
Ht.
Abo
ve B
urne
r (c
m)
200 L/L
1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49
S1
S4
S7
S10
S13
S16
S19
S22
-20 -15 -10 -5 0 5 10 15Radial Position (cm )
0
5
10
15
20
Ht.
Abo
ve B
urne
r (c
m)
1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49
S1
S4
S7
S10
S13
S16
S19
S22
-20 -15 -10 -5 0 5 10 15Radial Position (cm )
0
5
10
15
20
Ht.
Abo
ve B
urne
r (c
m)
450 L/L
325 L/L
Particle scattering increases with XFe(CO)5 in air stream.
0.00
0.05
0.10
0.15
0 500Fe(CO)5 Volume Fraction in Air (ppm)
Flam
e St
rneg
th
0
1
2
3
4
Part
icle
Sca
tterin
g C
ross
-sec
tion
Calc
Expt.Fl
ame
Stre
ngth
From: Linteris, G.T., Katta, V.R., and Takahashi, F., “Experimental and Numerical Evaluation of Metallic Compounds for Suppressing Cup-Burner Flames,” Combustion and Flame, 138:78-96, 2004.
Scattering from particles is correlated with low effectiveness
Iron as a fire suppressant?
1. Much less effective than expected.
2. Gas-phase catalytic reactions => lower the radical concentrations. But…
3. Particles are a sink for the active species.
4. Lower temperature in the stabilization region leads to more particle formation.
What about DMMP?
Conclusions (for iron in cup-burner flames):
Cup Burner Extinction with DMMP and CO2 , (methane-air, 70°C)
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0 2000 4000 6000 8000 10000
CO2Vo
lume Fractio
n in Oxidizer
DMMP Volume Fraction In Oxidizer (uL/L)
Exctinction of CH4‐Air Cup Burner flame, T=70 oC
No Flame
Flame
From: G.T. Linteris, N. Bouvet, V.I. Babushok, F. Takahashi, V.R. Katta,Experimental and numerical simulations of the gas-phase effectiveness of phosphorus compounds, in Fire and Materials 2015, 14th international conference, Interscience Communications, London, UK, 2 - 4 February, 2015.
0
2
4
6
8
10
12
14
16
18
0 0.5 1 1.5
CO2Vo
lume Fractio
n in Oxidizer
DMMP Volume Fraction In Oxidizer (uL/L)
Exctinction of CH4‐Air Cup Burner Flame, T=70 oC
Br2
DMMP
Phosphorus vs. Bromine in Cup Burner
DMMP about 4 x better than Br at low conc.
But loses effectiveness at higher conc.
%
Scattering measurements here
With DMMP – 11 mm above burner
Rel
ativ
eR
ayle
igh
Scat
.Sig
nal
Rayleigh scattering in flame with added DMMP in air ( 1000 ppm)
Uncertainties discussed in: G.T. Linteris, N. Bouvet, V.I. Babushok, F. Takahashi, V.R. Katta,Experimental and numerical simulations of the gas-phase effectiveness of phosphorus compounds, in Fire and Materials 2015, 14th international conference, InterscienceCommunications, London, UK, 2 - 4 February, 2015.
Rel
ativ
eR
ayle
igh
Scat
.Sig
nal
Ht. above burner
Rayleigh scattering in flame with added DMMP in air ( 1000 ppm)
Uncertainties discussed in: G.T. Linteris, N. Bouvet, V.I. Babushok, F. Takahashi, V.R. Katta,Experimental and numerical simulations of the gas-phase effectiveness of phosphorus compounds, in Fire and Materials 2015, 14th international conference, InterscienceCommunications, London, UK, 2 - 4 February, 2015.
1. DMMP added to cup-burner flames does lose its effectiveness dramatically.
2. Particles do form – but loss of effectivenesscould also be due to the HC component.
3. Further experiments and modeling should determine why.
Current Status
Flame is stabilized at the base, where:
- Temperature is lower.
- Mixing is good, so reactants tend to be premixed (due to flame lifting at edge, and entrainment).
- Flame oscillates, making the flame easier to extinguish.
UCH4= 0.92 cm/s, Uox= 10.7 cm/s, XCO2 = 0.14t = 0 s
Flame flicker: 1. Makes flame easier to
extinguish.2. Without flicker, need 30%
more agent for extinguishment.
3. Some agents enhance flicker, some retard it.
4. Changes with agent loading.
Flame Structure (Showing Flicker) t=0.00 s
Flame Structure (Showing Flicker) t=0.08 s
UCH4= 0.92 cm/s, Uox= 10.7 cm/s, XCO2 = 0.14t = 0.08 s
Flame flicker: 1. Makes flame easier to
extinguish.2. Without flicker, need 30%
more agent for extinguishment.
3. Some agents enhance flicker, some retard it.
4. Changes with agent loading.
Flame lift-off
CH4 - Air + 1.66 % Br2Ch4 – Air + 2.46% CF3Br
Base is:- lower temperature (1400 K) as compared to higher up in the flame (1850 K).- Lifted, more premixed, with
+ more radical super equilibrium,+ better inhibition at base, so blows off there first + different chemsitry, due to different reactants: e.g., better regeneration of HBr
-6E-05
-5E-05
-4E-05
-3E-05
-2E-05
-1E-05
0
1E-05
6 7 8 9 10 110
500
1000
1500
2000
CH4+Br= CH3+HBr
CH2O+Br=HCO+HBr
Br+Br+M=Br2+M
1
-4
0
F+
F-
Fnet
T
Trailing flame, 2.46 % CF3Br
-5
HBr+OH=Br+H2O
HBr+H=Br + H2
Br2+H=Br+HBr
-3
-2
-1
-6Sum
of R
eact
ion
Rat
es m
ole
cm s
(x
10
)-3
-14
-6.00E-05
-5.00E-05
-4.00E-05
-3.00E-05
-2.00E-05
-1.00E-05
0.00E+00
1.00E-05
6 7 8 9 10 110
500
1000
1500
2000
CH4+Br= CH3+HBr
CH2O+Br=HCO+HBr
Br+Br+M=Br2+M
F+
F-
Fnet
T
Trailing flame, 1.66 % Br2
HBr+OH=Br+H2O
HBr+H=Br + H2
Br2+H=Br+HBr
T (K
) or B
r Rea
ctio
n Fl
ux m
ole
cm s
(x
10
)-3
-14
-5E-04
-4E-04
-3E-04
-2E-04
-1E-04
0
1E-04
2E-04
6 7 8 9 10 110
500
1000
1500
2000
F+
F-
Fnet
T
Reaction Kernel, 2.46 % CF3Br
HBr+OH=Br+H2O
HBr+H=Br + H2
Br2+H => Br + HBr
10
-40
0
-50
-30
-20
-10
20
C2H6+Br=C2H5+HBr
CH4+Br=CH3+HBr
CH2O+Br=HCO+HBr
r (mm)
Sum
of R
eact
ion
Rat
es m
ole
cm s
(x
10
)-3
-14
-5E-04
-4E-04
-3E-04
-2E-04
-1E-04
0
1E-04
2E-04
6 7 8 9 10 110
500
1000
1500
2000
F+
F-
Fnet
T
Reaction Kernel, 1.66 % Br2
HBr+OH=Br+H2O
HBr+H=Br + H2
Br2+H => Br + HBr
C2H6+Br=C2H5+HBr
CH4+Br=CH3+HBr
CH2O+Br=HCO+HBr
r (mm)
T (K
) or B
r Rea
ctio
n Fl
ux m
ole
cm s
(x
10
)-3
-14
Influence of Flame Base on Inhibition Chemistry
10
500
1000
1500
2000
T (K
) or B
r Rea
ctio
n Fl
ux m
ole
cm s
(x
10
)-3
-14
10
500
1000
1500
2000
T (K
) or B
r Rea
ctio
n Fl
ux m
ole
cm s
(x
10
)-3
-14
Burner
Inhibiting reactions 10x higher in base
Because HBr regeneration steps are higher in base
0.0
0.2
0.4
0.6
0.8
1.0
0 100 200 300 400 500Fe(CO)5 Mole Fraction (ppm)
Nor
mal
ized
Bur
ning
Vel
ocity
= 1.0
Different flame metrics influence effectiveness:=> Xa for 30% reduction in flame speed would imply high effectiveness,
X = 0.212 ,oxO
0.0
0.2
0.4
0.6
0.8
1.0
0 100 200 300 400 500Fe(CO)5 Mole Fraction (ppm)
Nor
mal
ized
Bur
ning
Vel
ocity
X = 0.21O2 ,ox
= 1.0
=> but, Xa for 5 cm/s flame speed would imply low effectiveness,
5 cm/s
Different behavior sometimes shows up at higher concentrations.
1
10
100
1000
CO2 CF3H CF3Br TMT MMT Fe(CO)5
Perf
orm
ance
Rel
ativ
e to
CO
2
Agent
a=430
a=490
a=550
30
45
Cup, pure
Cup, 10% less CO2(like LOI)
Flame Metric
10Premixed:
Counterflow:
Agent Effectiveness:
=>can vary with flame type.DMMP
0
0.2
0.4
0.6
0.8
1
0 0.01 0.02 0.03 0.04 0.05
Normilized Bu
rning Ve
locity
DMMP Volume Fraction
CH4
C2H4
CH2O
0
0.2
0.4
0.6
0.8
1
0 0.01 0.02 0.03 0.04 0.05
Normalized
Burning
Velocity
Br2 Volume Fraction
CH4
CH2O
C2H4
Fuel Type Can Influence Inhibitor Effectiveness In premixed flame,
Br2 affected more than DMMP by fuel type (for CH4, C2H4, CH2O)
This image cannot currently be displayed.
Flame Temperature Affects Inhibition Efficiency
=> Cooler flames are inhibited more (for either Fe or DMMP).
0.0
0.2
0.4
0.6
0.8
1.0
0 100 200 300 400 500Fe(CO) 5 Mole Fraction (ppm)
Nor
mal
ized
Bur
ning
Vel
ocity
0.20
= 1.0X = 0.24O2,ox
0.21
0
0.2
0.4
0.6
0.8
1
0 0.003 0.006 0.009 0.012 0.015
Normalized
Burning
Velocity
OP(OH)3 Volume Fraction
1 0.53
1.33
=1.14
0
0.2
0.4
0.6
0.8
1
0 0.005 0.01 0.015 0.02 0.025 0.03
Normalized
Burning
Velocity
Br2 Volume Fraction
0.53
1.33
1.141
Stoichiometry Affects Inhibitor Efficiency
=>lean flame inhibited much more for Br2 than for H3PO4.
HOPO2 HOPO
PO2PO3
OP(OH)2
+O
+OH,O+OH+H
+O2
+H+H+H +H
+O
Lean Stoic.
P catalytic inhibition cycle
Stoichiometry Affects Inhibitor Efficiency
=>can be explained by thermodynamics
1. Characteristics of flame system affect efficiency of chemical inhibition (via flicker, heat losses/stand-off, stabilization mechanisms, mixing conditions, etc.), BUT
2. Inhibitors can influence the physical properties of the flame itself (where and how the flame stabilizes, temperature, flow field, etc.) and hence the inhibition.
3. Most of the physical properties of the flames over polymers which can affect chemical inhibition have not been studied (even more so if a condensed-phase FR is also working).
Bottom Line:
1. Have excellent tools for understanding gas-phase action of fire retardants.
2. Use detailed modeling to understand:a. Why DMMP did not work well in cup burner.b. Why antimony / bromine systems does work well
- Sb? Br? Why no condensation?
3. Study flames with polymers with FRs.
4. Use numerical code to model burning cylinder (simulating UL-94)
4. Systems of interest?
Future Work:
Numerical simulations to understand UL-94
Porous cylinder flames Resemble solid burning (e.g., UL 94) Perform time-dependent axisymmetric
computation with full chemistry/transport for:
DMMP added to fuel Br2 added to fuel
CH4 in air 15% CO2
PMMA in air 18% CO2
top related