flammability characteristics of jp-8 fuel vapors existing within a typical aircraft fuel tank
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Flammability Characteristics of JP-8 Fuel Vapors Existing Within a Typical Aircraft Fuel Tank. Steven M. Summer Department of Mechanical & Aerospace Engg. Masters Thesis Defense December 21, 2000 Faculty Advisor: Prof. C. E. Polymeropoulos. Overview of Problem. - PowerPoint PPT PresentationTRANSCRIPT
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Flammability Characteristics Flammability Characteristics of JP-8 Fuel Vapors Existing of JP-8 Fuel Vapors Existing
Within a Typical Aircraft Fuel Within a Typical Aircraft Fuel TankTank
Steven M. SummerDepartment of Mechanical & Aerospace Engg.
Masters Thesis DefenseDecember 21, 2000
Faculty Advisor: Prof. C. E. Polymeropoulos
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Overview of ProblemOverview of Problem
Threat of ignition of fuel vapors within aircraft fuel tanks• Has long been noted, but until recently, not
much data• Several protection systems have been
researched and proposed, but none implemented in commercial aircraft
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Overview of ProblemOverview of Problem
July 1996, TWA 800 crashes over East Moriches, NY• NTSB cites an in-flight fuel tank explosion as
cause• Numerous research projects undertaken by
CIT, UNR, ASU, SWRI and others• Overall goal: generate enough data on aviation
fuel vapor generation/flammability to be able to develop a means of protecting against ignition
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Overview of Problem: Overview of Problem: Aircraft Fuel TanksAircraft Fuel Tanks
Fuel is typically is stored in two wing tanksLarger aircraft also use a Center Wing
Tank (CWT) located within fuselage
Definition: Fuel Mass Loading - (Mass of Liquid Fuel)/(Total Internal Tank Volume)
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Overview of Problem: Overview of Problem: Aircraft Fuel TanksAircraft Fuel Tanks
In some cases, located directly underneath CWT is the Environmental Conditioning System (ECS)
Hot bleed air from the ECS heats CWT fuel, resulting in an increase of the FAR
ARAC’s FTHWG determined that these tanks are at risk 30% of the total flight time compared to 5% for CWT’s without ECS
Aviation Rulemaking
Advisory Committee
Fuel Tank Harmonization
Working Group
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Overview of Problem:Overview of Problem:Aviation FuelAviation Fuel
Specifications for commercial grade fuel (Jet A/Jet A-1 & Jet B) set forth by ASTM D1655• Sets min/max values for things such as flash
point, boiling point, freezing point, etc.• Very vague criteria for actual composition of
the fuel
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Overview of Problem:Overview of Problem:Aviation FuelAviation Fuel
“These fuels shall consist of refined hydrocarbons derived from
conventional sources including crude oil, natural gas liquids, heavy oil, and
tar sands”
-ASTM D1655
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Summary of ProblemSummary of Problem
CWTs with adjacent heat sources (ECS)• Increases rate of fuel vapor generation
Typically small amount of fuel in CWT• Reduced impact on flammability because of
increased evaporation of light ends
Lack of a definitive composition of aviation fuels• Leads to fuels consisting of hundreds of
hydrocarbons, with varying properties
Result: Fuel Tank Flammability Potential is Increased Throughout
Flight Profile
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Heated Fuel Vapor Testing• Determine the effects of
fuel mass loading,liquid fuel evaporative surface area andresidual fuel on tank walls and
on ullage vapor generation within an aircraft fuel tank environment
ObjectivesObjectives
Definition: Ullage - the unused internal portion of the fuel tank
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ObjectivesObjectives
Heated Fuel Vapor Testing With Tank Wall Cooling:
• Determine the effects of cold tank wall temperatures on ullage vapor generation within an aircraft fuel tank environment
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ObjectivesObjectives
Lower Oxygen Limit of Flammability Testing:• Determine the lowest oxygen level
within the tank that will support ignition of the ullage fuel vapors (i.e. LOLF)
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Heated Fuel VaporHeated Fuel VaporTesting: ObjectivesTesting: Objectives
Determine the effects of• fuel mass loading,• liquid fuel evaporative surface area and• residual fuel on tank walls and
on ullage vapor generation within an aircraft fuel tank environment
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Heated Fuel VaporHeated Fuel VaporTesting: ApparatusTesting: Apparatus
88.21 ft3 vented, aluminum fuel tank• 14 K-type thermocouples
1 Fuel5 Surface (3 wall, 2 ceiling)5 Ullage
• 2 hydrocarbon sample ports150,000-Btu kerosene air heaterSeveral sized fuel pans
• 1 x 1 , 2 x 2 and one covering tank bottom
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DoorT/C 5
T/C 2
Analyzer Port 2
T/C 1
T/C 0T/C 3
Analyzer Port 1
T/C 4
Heat InletHeat Outlet
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Heated Fuel VaporHeated Fuel VaporTesting: ProceduresTesting: Procedures
Fuel measured and poured into fuel panFuel pan placed into tankTank door sealedKerosene air heater turned onFuel heated to 10° above flash point (125 °F)Hydrocarbon concentration monitored until
equilibrium is reached
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Mass Loading ResultsMass Loading Results
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Mass Loading ResultsMass Loading Results
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Mass Loading ResultsMass Loading Results
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Evaporative Surface Area ResultsEvaporative Surface Area Results
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Evaporative Surface Area ResultsEvaporative Surface Area Results
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Residual Fuel ResultsResidual Fuel Results
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Residual Fuel ResultsResidual Fuel Results
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Tank Wall Cooling:Tank Wall Cooling:ObjectivesObjectives
Determine the effects of cold tank wall temperatures on ullage vapor generation within an aircraft fuel tank environment
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Tank Wall Cooling:Tank Wall Cooling:ApparatusApparatus
Same tank as Heated Fuel Vapor Testing with some modifications:• 3-in. shell surrounded the two side and rear
walls for CO2 cooling
• Kerosene air heater replaced with a thermostatically controlled hot plate
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Tank Wall Cooling:Tank Wall Cooling:ProceduresProcedures
Fuel measured (1.5 gallons) and poured into fuel pan
Fuel pan placed into tank & tank door sealed Hot plate turned on Fuel heated to 10° above flash point (125 °F) and
maintained for 2 hours Walls were cooled to desired temperatures and
maintained until significant decrease in HC concentration was observed
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Tank Wall Cooling ResultsTank Wall Cooling Results
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LOLF Testing:LOLF Testing:ObjectivesObjectives
Determine the lowest oxygen level within the tank that would support ignition (i.e. the lower oxygen limit of flammability)
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LOLF Testing: ApparatusLOLF Testing: Apparatus
9 ft3 vented, aluminum fuel tank placed inside of 10 m3 pressure vessel equipped with:• 12 K-type thermocouples
1 Fuel 7 Surface (3 floor, 1 on each side wall) 4 Ullage
• 9.5" x 9.5" fuel pan located in center of tank• Thermostatically controlled hot plate• 6" diameter mixing fan• 2 hydrocarbon sample ports• 1 oxygen sample port• Spring loaded blow-out plate• Two tungsten electrodes powered by a 20,000 VAc, 20 mA
transformer
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V i d e o C a m e r a
T o H C A n a l y z e r
R i g h t T e s t T r a c k
L e f t T e s t T r a c k
1 0 m P r e s s u r e V e s s e l3
A n a l y z e r B y p a s sS a m p l e L i n e O A n a l y z e r2H e a t e rH e a t e r
S p a r k S o u r c e F a n
= T h e r m o c o u p l e F e e d t h r o u g h
N L i n e s2
Video C am era
To H C A n a ly z e r
R igh t Test Track
Left Test Track
O A n a ly z e r
2H eater
Spark Source
Fan
= T h e rm o c o u p le F e e d th ro u g h
N L in e s2
R ig h t T /C T re eL e ft T /C T re e
L iq u id J P -8 F u e lF u e l P a n
= T h e rm o c o u p le B e a d6.
0"6.
0"
LOLF Testing: LOLF Testing: ApparatusApparatus
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LOLF Testing: ProceduresLOLF Testing: Procedures
Fuel measured (3/8-gallon) & placed in pan Fuel pan placed in center of tank Nitrogen injected until desired O2 concentration
reached Hot plates turned on Fuel heated to and maintained at ~150°F until HC
concentration leveled off at ~25000 ppm C3H8
Spark initiated for 1, 2 & 3 second durations
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LOLF Testing Results LOLF Testing Results (Preliminary Methane Tests)(Preliminary Methane Tests)
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LOLF Testing ResultsLOLF Testing Results
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ConclusionsConclusions
Heated Fuel Testing• At mass loading of 0.08 – 0.15 kg/m3
significant reduction in HC concentration• Evaporative surface area has no effect on HC
concentration• As evaporative surface area decreases, longer
time necessary to obtain maximum HC concentration
• Residual fuel has no effects
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ConclusionsConclusions
Tank Wall Cooling Testing• As tank wall temperatures decrease, the rate of
decrease in HC concentration increases
LOLF Testing• Methane LFL of 5.3 – 5.35% determined
• LOLF determined to be 12% O2
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RecommendationsRecommendations
Tank wall & ullage temperatures need to be treated carefully
Further LOLF experiments should include dynamic pressure instrumentation
LOLF at altitude