OSU Analysis with FDS - Home : FAA Fire Safety
Transcript of OSU Analysis with FDS - Home : FAA Fire Safety
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OSU Analysis with FDS
Haiqing Guo, Mike Burns, Richard E. Lyon
William J. Hughes Technical Center, FAA, Atlantic City, NJ
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Introduction
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• OSU test instrument is subject certain level of irreproducibility.
• There exists certain time delay on the OSU signal response.
• More accurate and more reliable HRR test method needs better understanding of the current OSU design.
• Perform detailed characterization and heat transfer analysis (analytical and numerical) on OSU.
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Representative OSU Tests
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-10
0
10
20
30
40
50
60
0 50 100 150 200 250 300
Hea
t R
ele
ase
Ra
te (
kW
/m2)
Time (s)
Split Ratio, 1:2.2
Split Ratio, 1:3.0
Split Ratio, 1:4.3
Blank, 1:3.0
-20
-10
0
10
20
30
40
50
60
0 50 100 150 200 250 300Hea
t R
elea
se R
ate
(kW
/m2)
Time (s)
A24
0
10
20
30
40
50
60
0 50 100 150 200 250 300
Hea
t R
elea
se R
ate
(kW
/m2)
Time (s)
B09
Schneller Panel Test
smeared HRR
unreal HRR
different blank run
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OSU Calibration
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air temp
cone temp
hot gas temp
TP temp
hot gas hot gas air
300
400
500
600
700
800
0 500 1000 1500 2000 2500
Tem
pera
ture
(K
)
Time (s)
Split Ratio, 1:2
300
400
500
600
700
800
0 500 1000 1500 2000 2500
Tem
pera
ture
(K
)
Time (s)
Split Ratio, 1:3
300
400
500
600
700
800
0 500 1000 1500 2000 2500
Tem
pera
ture
(K
)
Time (s)
Split Ratio, 1:4
hot gas
thermopile
inner cone
plenum air
hot gas
thermopile
inner cone
plenum air
hot gas
thermopile
inner cone
plenum air
standard calibration procedure + detailed characterization
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Thermal Analysis on Inner Cone
5
T1 T2
Tw
outer cone
inner cone
dt
dTcATTAhTTAh w
ww 2211
c
hht
ww ehh
ThThT
hh
ThThT
21
21
22110,
21
2211
Split Ratio (1:2) Split Ratio (1:3) Split Ratio (1:4)
h1 (W/m2-K) 5.5 6.0 6.5
h2 (W/m2-K) 27.2 41.2 49.1
τ (s) 60 42 35
energy equation:
1-D Model
square wave constant
time constant
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350
400
450
500
0 500 1000 1500
Th
erm
opile
Te
mp
era
ture
(K
)
Time (s)
Split Ratio 2:1
Split Ratio 3:1
Split Ratio 4:1
Cone Wall Effects on Thermopile
Based on inner cone wall temperature, plenum air and hot gas temperature, the thermopile temperature can be calculated using mixing theory.
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CFD Modeling (2D Model)
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hot gasair
400
420
440
460
480
350
400
450
500
550
600
2900 3000 3100 3200 3300
Th
erm
opile
Te
mp. (K
)
Co
ne
Wa
ll T
em
p. (K
)
Time (s)
Thermopile
T5
T3
T1
• 2-D FDS model. • Hot gas T is following a step change. • Air T is constant. • Both Ts are based on the characterization results.
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Model of Sample / Holder Insertion
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heater
air
air
plate
air
air
heater
(1) (2)
x0
10
20
30
40
0
1
1800 1900 2000 2100 2200 2300 2400 2500
Fire
HR
R (
kW/m
2)
Sam
ple
Sta
tus
(-)
Time (s)
sample insertion
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Sample Holder Effect
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-20
-10
0
10
20
30
40
450
500
550
600
1500 1700 1900 2100 2300 2500
Pre
scri
bed
HR
R (
kW/m
2)
Ther
mo
pile
Tem
per
atu
re (
°C)
Time (s)
Dummy sample
Dummy sample+Fire
Prescribed HRR
0
5
10
15
20
25
30
35
0
10
20
30
40
50
60
70
1500 1700 1900 2100 2300 2500
Pre
scri
be
d H
RR
(kW
/m2)
Tem
per
atu
re D
iffe
ren
ce (
°C)
Time (s)
Temp. Difference
Prescribed HRR
The modeled thermopile temperature is overlaid with prescribed HRR for comparison.
Thermopile temperature after baseline subtraction.
holder insertion
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Sample Holder Effect on Heat Flux
10
heater
air
air
plate
air
air
heater
(1) (2)
x
Sample holder increases surface area for heat convection and hence increase the thermopile temperature.
holder insertion holder insertion
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Summary
• Upper region, the double-cone system dominates the dynamics of the system.
• Lower region, the sample holder causes unreal heat release signal. Blank run with a dummy sample needs to be subtracted.
• etc.
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