federal aviation administration measuring ullage oxygen concentration november 17-18, 2009 0...
TRANSCRIPT
1Federal AviationAdministration
Measuring Ullage Oxygen ConcentrationNovember 17-18, 2009
MeasuringOxygen Concentration in a Fuel Tank Ullage
Federal AviationAdministration
ISFPWG Meeting
Atlantic City, NJ
November 17 - 18, 2009
William CavageAJP-6320 Fire Safety TeamWm. J. Hughes Technical CenterFederal Aviation Administration
2Federal AviationAdministration
Measuring Ullage Oxygen ConcentrationNovember 17-18, 2009
• Background
• FAA Method
• Light Absorption Gas Sample
• Optical Fluorescence In Situ
• Status
Outline
3Federal AviationAdministration
Measuring Ullage Oxygen ConcentrationNovember 17-18, 2009
• FAA has been seeking to improve fuel tank safety in the wake of TWA Flight 800 in July of 1996− Rule published requiring extensive flammability reduction on
both future built and existing aircraft on present types
• The measurement of ullage oxygen concentration is important to the fuel tank inerting community when researching methods, validating models, and certifying systems− FAA method for measuring ullage oxygen concentration at
reduced ullage pressures has been successful but can be cumbersome
− Emerging products have the potential to simplify and improve upon R&D / Certification work for fuel tank inerting
Background
4Federal AviationAdministration
Measuring Ullage Oxygen ConcentrationNovember 17-18, 2009
FAA Method• FAA method involves an extensive controlled gas sample
system using lab based galvanic cell oxygen sensors− Method used extensively in the lab and on several flight tests with
great success− Consistently duplicates calibrations gases up to 40K feet within
+/- 0.1% oxygen
• Improved FAA gas sampling method− Made design changes to OBOAS regulated sample train and
packaging based on lessons learned during FAA flight testing − New system is lighter, smaller, quieter, and takes less power to
start and operate− Gas sample lag time better but not proven to have equivalent
level of safety− Questions remains if it is more reliable and maintainable
5Federal AviationAdministration
Measuring Ullage Oxygen ConcentrationNovember 17-18, 2009
FAA Oxygen Concentration Measurement Method
c
XX.XO2
Analyzers
Cal Gas In
Sample Return
Sample Containment Box
c
c
cMotor
Motor
Motive In
Motive Out/Dump
Ventilation Air
XX.X XX.X XX.X XX.X
Ch4
Aux4
Ch3
Aux3
Ch2
Aux2
Ch1
Aux1
PressureController
Electronics Shroud
Power InterfaceSignal Interface
- Flash Arrestor
- Check Valve
- Pump
- Bulkhead Fitting
- Pressure Controller
- Filter
- Sensor
- Selector Valve
- Flow Meter
Key
- Needle Valve
c
- Pressure Regulator
- Air Inductor
- Flow Indicator
6Federal AviationAdministration
Measuring Ullage Oxygen ConcentrationNovember 17-18, 2009
FAA Method Flight Test Results Compared with Lab and Analytical Calculation
0
2
4
6
8
10
12
14
16
18
65 70 75 80 85 90 95 100 105 110 115
Time (mins)
Ox
yg
en
Co
nc
en
tra
tio
n (
% v
ol)
A320 Flight Test [O2]
Analytical Model [O2]
Scale Model [O2]
Comparison of Model Data - Average Ullage [O2]Airbus Test v1972 - Dual Flow System
7Federal AviationAdministration
Measuring Ullage Oxygen ConcentrationNovember 17-18, 2009
4-Bay Cascading Inerting Data Comparison of FAA Method Compared with Analytical Calculation
0
5
10
15
20
25
0 5 10 15 20 25 30 35 40
Time (mins)
Oxy
gen
Co
nce
ntr
atio
n (
% v
ol)
Bay 1 Bay 1 Bay 2 Bay 2 Bay 3 Bay 3 Bay 4 Bay 4
Comparison of Cascading Inerting Test with Model Data
Analytical Model Measured Data
Increasing Altitude
StableCruise
Decreasing Altitude
8Federal AviationAdministration
Measuring Ullage Oxygen ConcentrationNovember 17-18, 2009
Light Absorption Gas Sample• Oxigraf makes a light absorption sensor which has been
applied to an unregulated gas sample train− Unregulated sample train uses an integrated sensor board that
measures infrared light absorption using a tunable laser diode (TLD technology)
− Proprietary software used to interpret spectral data
• System has been packaged for flight test− System has very fast response time, given short enough gas
sample lines and has been shown to duplicate calibration gases as well as FAA method up to 35K feet sample altitude.
− System packaging has potential to be significantly smaller and lighter than the FAA method and system requires less power.
− System speed has yet to illustrate usefulness and there are significant limitations to gas sample, and return locations
9Federal AviationAdministration
Measuring Ullage Oxygen ConcentrationNovember 17-18, 2009
Light Absorption Method using TLD
Oxigraf O2N2 Flight TestOxygen Analyzer
10Federal AviationAdministration
Measuring Ullage Oxygen ConcentrationNovember 17-18, 2009
Results – Airplane Fuel Tank Simulation• Measured fuel tank test article ullage [O2] with both the FAA
method and the light absorption method (Oxigraf) − Results of
Oxigraf and FAA method very close
− The inerting of test tank erratic due to problems, but this illustrates the small advantage of rapid response
0
2
4
6
8
10
12
14
0 20 40 60 80 100 120 140 160 180 200
Time (mins)
Oxy
gen
Co
nce
ntr
atio
n (
%vo
l)
-20
0
20
40
60
80
100
120
Alt
itu
de
(kF
t) /
Tem
per
atu
re (
deg
F)
FAA Method OxigrafAltitude Ullage Temp
Commercial Transport AirplaneMission Simulation
11Federal AviationAdministration
Measuring Ullage Oxygen ConcentrationNovember 17-18, 2009
Optical Fluorescence• Optical fluorescence using in situ probe (ASF)
− Small fiber optic probe uses spectrometer to interpret coherent light signal which is highly dependent on temperature/pressure
− Used in situ (in place) which has many advantages (low power, small size/weight, rapid response) but also has limitations
• Applying an in situ probe has been be very problematic− Not practical to calibrate on a daily basis− Requires simultaneous/co-located accurate temperature and
pressure measurement to compensate signal− As applied today, does not have faster response than FAA
• Recent work performed has illustrated marked improvement of the probe to duplicate calibration gases− Still struggle with good results at high altitudes− Probe has passed rigorous DO-160 E testing
12Federal AviationAdministration
Measuring Ullage Oxygen ConcentrationNovember 17-18, 2009
Latest Optical Fluorescence (ASF) In Situ Probe
13Federal AviationAdministration
Measuring Ullage Oxygen ConcentrationNovember 17-18, 2009
ASF Oxygen Sensor Data with Varying Temperature
14Federal AviationAdministration
Measuring Ullage Oxygen ConcentrationNovember 17-18, 2009
• Both the FAA method and the light absorption (Oxigraf) method duplicate calibration gases well at a variety of conditions and both agree on oxygen concentration measurements made during a simulation of an inert commercial transport airplane fuel tank flight cycle− Oxigraf system has faster response time but appears to be of
little advantage− Oxigraf system already performed some flight testing and is
slated for more with several OEMs / Operators
• Optical fluorescence making progress but still working out problems− Slated for more chamber examinations in December
Status