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AAR-422 Fire Safety R&D
________________________________________________________Inerting System Testing
December 11th-12th, 2000International Aircraft Systems Fire
Protection Working Group
NEA Ullage Washing TestingWith a Vented Fuel Tank
AAR-422 Fire Safety R&D
________________________________________________________Inerting System Testing
Outline
• Background• Ullage Washing Data• Model Validation• Hydrocarbon Effects Data• Temperature Effects Data
AAR-422 Fire Safety R&D
________________________________________________________Inerting System Testing
Background• Obtained Nitrogen Supply System from Air Liquide to
Examine Fuel Tank Ullage Washing
• Utilized Existing Test Article
• Primary Task is to Characterize the Ability of Nitrogen to Inert an Empty Fuel Tank– Effective of Nitrogen Purity, Flow Rate
– Effective Ullage Temperature / Hydrocarbon Concentration
– Develop Empirical Relationships and Varify Existing Models
AAR-422 Fire Safety R&D
________________________________________________________Inerting System Testing
AAR-422 Fire Safety R&D
________________________________________________________Inerting System Testing
NEA Purity Comparison Ullage Washing Data
0
5
10
15
20
25
0 500 1000 1500 2000 2500 3000
Time (seconds)
Ta
nk
Ox
yge
n C
on
ce
ntr
ati
on
(%
)
88% Pure Nitrogen90% Pure Nitrogen92% Pure Nitrogen94% Pure Nitrogen96% Pure Nitrogen98% Pure Nitrogen
6 CFM Flow Rate
AAR-422 Fire Safety R&D
________________________________________________________Inerting System Testing
Nondimensional Time• Want to Express Time in Terms of Volume
Delivered
• Volumetric Tank Exchange = Time * Volume Flow Rate / Total Tank Volume
• Should Allow for Comparison of Data with Different Parameters, Regardless of Volume Flow Rate
AAR-422 Fire Safety R&D
________________________________________________________Inerting System Testing
Volume Flow Rate Comparison Ullage Washing Data
0
5
10
15
20
25
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
Volumetric Tank Exchange
Ta
nk
Ox
yge
n C
on
ce
ntr
ati
on
(%
)
5.5 CFM
4 CFM
3 CFM
2 CFM
96% Pure
AAR-422 Fire Safety R&D
________________________________________________________Inerting System Testing
NEA Purity Comparison Ullage Washing Data
0
5
10
15
20
25
0 0.5 1 1.5 2 2.5 3
Volumetric Tank Exchage
Tan
k O
xyg
en C
on
cen
trat
ion
(%
)
88% Pure Nitrogen
90% Pure Nitrogen
92% Pure Nitrogen
94% Pure Nitrogen
96% Pure Nitrogen
98% Pure Nitrogen
6 CFM Flow Rate
AAR-422 Fire Safety R&D
________________________________________________________Inerting System Testing
Nondimensional Oxygen Concentration
• Want to Express [O2] in Terms of Purity Delivered. Consider that Gas is Slowly Changing the Ullage to Gas Purity
• Tank Inertion Ratio = Air[O2] - Tank[O2] / Air[O2] - NEA[O2]
• Should Allow for Comparison of Data with Different Parameters, Regardless of Purity
AAR-422 Fire Safety R&D
________________________________________________________Inerting System Testing
NEA Purity Comparison Ullage Washing Data
0
0.2
0.4
0.6
0.8
1
1.2
0 0.5 1 1.5 2 2.5 3
Volumetric Tank Exchange
Tan
k In
erti
on
Rat
io
88% Pure Nitrogen
90% Pure Nitrogen
92% Pure Nitrogen
94% Pure Nitrogen
96% Pure Nitrogen
98% Pure Nitrogen
6 CFM Flow Rate
AAR-422 Fire Safety R&D
________________________________________________________Inerting System Testing
Comparison of Data with Solutions• Empirical Equation (fourth order
polynomial) Based on Previous Graph
• ANM-100 Model (Ivor Thomas)
– Based on O2 Volume Exchange
– Gives One Nondimensional Solution
• Exact Solution Based on Perfect Mixing Model (y = 1 - e-λt )
• Results Compare Well
AAR-422 Fire Safety R&D
________________________________________________________Inerting System Testing
Ivor Thomas Model Comparison
0
5
10
15
20
25
0 500 1000 1500 2000 2500
Time (seconds)
Ox
yge
n C
on
ce
ntr
ati
on
(%
)
94% NEA Data
96% NEA Data
94% NEA Model
96% NEA Model
AAR-422 Fire Safety R&D
________________________________________________________Inerting System Testing
Empirical Data Comparison with Analytical/Numerical Results
y = -0.0145x4 + 0.1345x3 - 0.5275x2 + 1.0873x - 0.0121
0
0.2
0.4
0.6
0.8
1
1.2
0 0.5 1 1.5 2 2.5 3 3.5
Volumetric Tank Exchange
Ta
nk
Ine
rtin
g R
ati
o
Empirical Curve
Model Data
Exact Solution
Empirical Curve Fit Equation
xey 1
Exact Solution
AAR-422 Fire Safety R&D
________________________________________________________Inerting System Testing
Effects of Ullage Temperature / [THC]
• Performed Several Tests Varying Tank Ullage Temperature and Total Hydrocarbon Concentration
• Used Hot Plate Element, Kerosene Heater, and Liquid CO2
• Final Results Show Little Effect on Time to Inert
AAR-422 Fire Safety R&D
________________________________________________________Inerting System Testing
Ullage [THC] Comparison
0
5
10
15
20
25
0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600
Time (sec)
Ta
nk
Ox
yge
n C
on
ce
ntr
ati
on
(%
)
No Fuel
5.6K PPM Propane Ullage [THC]
15.6K PPM Propane Ullage [THC]
AAR-422 Fire Safety R&D
________________________________________________________Inerting System Testing
Ullage Temperature Comparison
0
5
10
15
20
25
0 500 1000 1500 2000 2500 3000
Time (sec)
Ox
yge
n C
on
ce
ntr
ati
on
(%
)
Baseline (88 Degrees FAverage)
Cold Ullage (40 Degrees FAverage)
Hot Ullage (125 Degrees FAverage)
AAR-422 Fire Safety R&D
________________________________________________________Inerting System Testing
Future Work
• Continue with Re-circulate and Replace Work and Quantify Benefit
• Extrapolate Requirements for an On-Aircraft System and Determine Preliminary Cost/Ben
• Work with Manufacturers to Develop Innovative Designs to Cut Cost/Weight/Size
