Modelling Fire Scenarios in Residential Buildings with Respect to the Benefit of Smoke Detectors and...
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Transcript of Modelling Fire Scenarios in Residential Buildings with Respect to the Benefit of Smoke Detectors and...
Modelling Fire Scenarios in Residential Buildings with Respect to the Benefit ofSmoke Detectors and Flame Retardants
Reporting of a study made by Dr. Anja Hofmann
BAMDepartment VII Safety in StructuresDivision Fire Engineering
By Rudi Bormsmember of the exec. comm.of EFRA
Project sponsored by EFRA
Budapest June 14th-15th 2007
2
• Hazardous home fires: 80 % of all fire fatalities in homes
• Fire spread is very fast: only 2 to 4 minutes escape time after fire detection, earlier tests in 1970s described longer escape times.
• Different concepts in Europe to minimise fire losses: Smoke detectors and flame retardants
European Home Fires
3
Smoke Detectors / Flame Retardants
• Valuable to wake and warn sleeping persons
• Escape time (2 to 4 minutes) is very short , especially for very young, older or disabled persons
• Batteries have to be changed regularly
• Flame retardants lead in general to later (or no) ignition and lower the heat release rate of the burning item
• Only several items of furniture are equipped with flame retardants (e.g. upholstery or television sets)
4
High Risk Items
• Upholstery: a single item could cause flashover in a room
• TV: 2 to 3 min to peak of HRR, lot of smoke (faster development than refrigerator/washing machine, lower peak)
• Toys: easy ignition with lighter after 1 to 3 sec, burning for up to 25 min
5
Experimental Data
• NIST study about smoke detector performance (2004)
• Experimental studies, e.g. Babrauskas (1988), CBUF, Hirschler, Troitzsch (1998), LCA (2000 - 2003)
• Fire test of the Berlin fire service (2005)
• Fire test of BAM / Berlin fire service (2006)
Validation
Time to Flashover:
2 - 17 min. (Non-FR)
20 min - ∞ (FR)
HRR for single items, e.g. upholstery, TV sets
10:30 min (Non-FR)
4:00 min (Non-FR)
6
CFD (Computional Fluid Dynamics)
• Field model: room is divided into cells (FVM)• Balances of mass, momentum, energy• Submodels: chemical reaction, radiation, soot, turbulence; and
material parameters
• Furniture with and without flame retardants• Different home geometries, closed and open windows• Smoke detectors
Results: temperatures, velocities, gas concentrations in the room, smoke production and smoke movement
7
Validation: Manufactured House
8
Validation A1: Given HRRHeat release rate of flaming chair:
(not completely consumed by fire)
Chair heat release rate
0
40
80
120
160
0 50 100 150 200 250
time [s]
Hea
t re
leas
e ra
te [
kW]
Submodels / input data:
• Chemical reaction
• Smoke production
• Radiation
• Turbulence
• Material properties for upholstery
9
Validation A1: Given HRR
•Submodels / input data:
• Chemical reaction
• Smoke production
• Radiation
• Turbulence
• Material properties for upholstery
10
A1:Predicted(FDS) and measured (TCE)temperatures
Predicted and measured temperatures in living room
20
45
70
95
120
145
170
0 50 100 150 200 250 300 350 400
Time [s]
Tem
per
atu
re [
°C]
FDS E_liv 2.38
FDS E_liv 1.50
FDS E_liv 1.18
FDS E_liv 0.58
'TCE_1 '
TCE_4
'TCE_5 '
'TCE_7 '
FDS: lines
Data: markers
11
Validation A2: Full chemical model
• Ignition: spark for 20 s
• Material: upholstery (NIST data)
• Reaction: polyurethane (FDS: NFPA Handbook, Babrauskas)
Submodels / input data:
• Chemical reaction
• Smoke production
• Radiation
• Turbulence
• Material properties for upholstery
12
Validation A2: Full chemical model
Submodels / input data:
• Chemical reaction
• Smoke production
• Radiation
• Turbulence
• Material properties for upholstery
13
A2: Predicted and measured temperatures
20
45
70
95
120
145
170
0 50 100 150 200 250 300 350 400
time [s]
tem
per
atu
re [
°C]
E_liv 2.38
'TCE_1 '
20
45
70
95
120
145
170
0 50 100 150 200 250 300 350 400
time [s]
tem
per
atu
re [
°C]
E_liv 2.10
'TCE_2 '
20
45
70
95
120
145
170
0 50 100 150 200 250 300 350 400
time [s]
tem
per
atu
re [
°C]
E_liv 1.79
'TCE_3 '
20
45
70
95
120
145
170
0 50 100 150 200 250 300 350 400
time [s]
tem
per
atu
re [
°C]
E_liv 1.50
'TCE_4 '
FDS: lines
Data: markers
Ignition time predicted too early
14
Subsidised home
Living room
15
Subsidised home
Living room
Smoke detectors
16
Subsidised home : Furniture
Living room
Smoke detectors
17
Input data: HRR sofas
0
500
1000
1500
2000
2500
3000
0 500 1000 1500 2000 2500 3000 3500 4000
time in s
HR
R i
n k
W
Non-FR, SFPE Handbook
P-FR, LCA data
18
Fire Spread
First burning item = sofa
19
Predicted temperatures
0
100
200
300
400
500
600
700
800
0 100 200 300 400 500 600 700 800 900
time in s
tem
pe
ratu
re in
°C
P-FR-LCA, living room 2.2 m
P-FR-LCA, living room 1.5 m
0
100
200
300
400
500
600
700
800
0 100 200 300 400 500 600 700 800 900
time in s
tem
pe
ratu
re in
°C
sofa-SFPE, living room 2.2 m
sofa-SFPE, living room 1.5 m
120°C
600°C
130 s 730 s
FR sofaNon-FR US sofa
20
Smoke: Visibility
0
5
10
15
20
25
30
35
0 50 100 150 200
time in s
visi
bilty
in m
0
5
10
15
20
25
30
35
0 50 100 150 200
time in s
visi
bili
ty in
m
30 s 60 s
4 m
21
Burning TV sets: HRR
0
50
100
150
200
250
0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000
time [s]
He
at
rele
as
e r
ate
[k
W]
Non-flame retardant LCA (TV)Sweden small ignition source
FlameRerardant LCA (TV) US.
22
Burning TV sets
23
Berlin Fire Service: Fire Test
24
Comparison
Observations in Fire Test Numerical model
Only TV burns 6:20 min 6:10 min
Shelf burns 8:30 min 7:00 min
Flashover 10:30 min 7:52 min
Flames out of window 11:00 min 9:00 min
Smoke detector 4:47 min 1:30 min
25
Children's room
• Accumulation of high risk items
– Mattresses
– Upholstery
– Electrical devices (TV sets, computer)
– Toys (plastic)
• Wrong behaviour:
– Playing with fire
– Hiding
26
Fire test in children‘s room
Extract from RTL coverage
27
Model Geometry
Observations Fire test Numerical model
Only lower mattress burns
1:30 min 2:10 min
Lower and upper mattress burn
3:00 min 3:00 min
Flashover 4:00 min 3:45 min
Flames out of window
4:30 min 4:00 min
Smoke alarms
2:00 / 2:23 min
0:37 / 1:05 min
28
Predicted and Measured Temperatures
0
200
400
600
800
1000
1200
100 150 200 250 300
Time in s
Te
mp
era
ture
in
°C
FDS 0,5
FDS 1,5
FDS 1,85
FDS 2,15
Data 0,5
Data 1,5
Data 1,85
Data 2,15
0
200
400
600
800
1000
1200
150 170 190 210 230 250 270 290
Time in s
Te
mp
era
ture
in °
C
FDS 0,5
FDS 1,5
FDS 1,85
FDS 2,15
Data 0,5
Data 1,5
Data 1,85
Data 2,15
Room centre Right front corner
29
Predicted Temperatures in Children‘s Room - Using a FR Mattress
0
200
400
600
800
1000
1200
0 1 2 3 4 5 6 7
time [min]
tem
pera
ture
[°C]
non FR 2.15 m
non FR 1.50 m
FR 2.15 m
FR 1.50 m
non FR
FR
30
Flame retardants have impact on fire safety
Numerical results:
• Lower temperatures in the room
• Benefit of additional escape time
• Additional time to flashover
Conclusions
31
Combination of both safety technologies
Smoke detectors warn inhabitants of fire and smoke; no impact on fire development
Use of flame retardants / appropriate materials is advisable for high risk items: Reduction of flammability and heat release
32
Thank you for your attention !