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OSU Analysis with FDS
Haiqing Guo, Mike Burns, Richard E. Lyon
William J. Hughes Technical Center, FAA, Atlantic City, NJ
Introduction
2
• 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.
Representative OSU Tests
3
-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
OSU Calibration
4
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
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
6
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.
CFD Modeling (2D Model)
7
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.
Model of Sample / Holder Insertion
8
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
Sample Holder Effect
9
-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
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
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.
11