07-08-03IASFPWG – Ottawa, Canada Limiting Oxygen Concentration (LOC) Work Update International Aircraft Systems Fire Protection Working Group Ottawa, Canada.

07-08-03IASFPWG – Ottawa, Canada

Limiting Oxygen Concentration (LOC) Work Update

International Aircraft Systems Fire Protection Working GroupOttawa, CanadaJuly 8 - 9, 2003

Steve SummerProject EngineerFederal Aviation AdministrationFire Safety Branch, AAR-440


LOC Testing – Work Update

Conducted sea level (SL) testing with a J-57 engine igniter

Conducted SL testing with a short duration arc from oil burner transformer

Measured voltage/current at spark gap and calculated energy for both spark/arc generator

Composed report of all data generated to date with the various ignition sources (AR-02/79)—due out shortly


Facilities – Pressure Chamber


Facilities – Pressure Chamber353 ft3 pressure vessel

• Working pressure of 650 psi.• Attached vacuum pump used to

evacuate chamber to reduced pressures seen at altitude.

• Not capable of simulating temperatures seen at altitude.


Facilities - LOC Test Article 9 ft3 simulated fuel tank placed inside of

vessel equipped with:• Bottom surface heaters.• 12 thermocouples.• 2 piezoresistive pressure transducers mounted

behind sintered porous metal discs.• Interchangeable pressure relief mechanism.

¼-in. aluminum plate. Foil diaphragm.

• Spark gap. 2 tungsten electrodes with controllable gap alignment

and spacing


Apparatus – LOC Testing

TH C A nalyzer

R igh t Test Track

Left Test Track

1 0 m P ressu re Vesse l

3 Ana lyze r Byp a ss

Sa m p le Line O A nalyzer

2

H eaterH eater

Spark Source

Fan

= Therm ocouple Feed through

N L ines2

H ouse A ir L ine


Apparatus – LOC Testing

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 d

6.0"

6.0"


Ullage Vapor Sampling


LOC Testing Apparatus

Ignition Sources• 10 kV Oil burner transformer operating at ~30 mA

provided both long (~1 second) and short (~0.1 second) arcs

• J-57 Engine spark igniter provided a very short (~175 second) spark

• 3" x 6" x 1" metal block heated by two cartridge heaters to temperature in excess of 1400°F

Energy Measurements• Voltage and current traces were taken using a HV and

current probe at the spark gap connected to oscilloscope


Oil Burner Transformer Voltage & Current Traces


Test Program JP-8 LOC Tests

• Mass Loading ~ 4.5 kg/m3

• Ambient pressure corresponding to altitudes of 0, 10, 20, 30 and 38 kft

• Ullage oxygen concentrations ranging from 21% to below the determined LOC

• Tests conducted with two different pressure relief mechanisms

¼-in. aluminum plate– Ignition = movement of plate

Foil diaphragm – Ignition = rupture of foil


Test Program (cont.)

Tests conducted initially at all altitudes with long duration oil burner transformer arc (~0.5 J, 1 s)

Subsequent tests conducted with various ignition sources at sea level in effort to determine any variation of LOC with ignition source• Short duration oil burner transformer arc (~0.08 J, 0.1 s)

• J-57 Engine igniter spark (~0.5 J, 175 s)

• Hot surface vapor ignition (HSVI)


LONG DURATION OIL BURNER TRANSFORMER

ARC TEST RESULTS


Aluminum Plate Relief Mechanism


Foil Diaphragm Relief Mechanism








J-57 ENGINE SPARK IGNITER TEST RESULTS




SHORT DURATION OIL BURNER TRANSFORMER

ARC TEST RESULTS


Short Duration Test Results


HOT SURFACE VAPOR IGNITION TESTING (HSVI)


HSVI Testing

Test Setup• Setup was identical to the spark/arc ignition

testing.• In place of spark, a 3" x 6" x 1" metal block was

heated by two cartridge heaters for use as the ignition source.

• Conducted only at sea level conditions.


HSVI Test Results

At 21% O2, ignition was achieved at a hot surface temperature (HST) of approximately 1350ºF.

A half-dozen other tests were conducted at O2 concentrations ranging from ~11.5 – 14%.• Though some “puffs” of smoke could be seen as the

HST approached ~1200º F, no ignitions occurred.

Therefore, HSI within the fuel tank provides no more of a threat than spark ignition.


Conclusions

LOC at SL through 10 kft is ~12%, increasing linearly through 40 kft to ~14.5%

Little effect seen on SL LOC due to ignition source• Long duration arc: 12%• High powered spark: 12.3%• Short duration arc: 12.9%• HSVI: ??


Future LOC Work

Currently working with a very high energy spark (>20 J)• 120 Vac, 400 cycle hard short to ground• Will be placing in the tank within the next

week.• To commence testing shortly thereafter.

Technote AR-02/79 due out shortly

07-08-03IASFPWG – Ottawa, Canada Limiting Oxygen Concentration (LOC) Work Update International Aircraft Systems Fire Protection Working Group Ottawa, Canada.

Documents

iasfpwg ottawa

group ottawa

canada loc testing work

canada future loc work

spacing slide

pressure vessel

spark gap

sea level sl testing