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Limiting Oxygen Concentration (LOC) Work Update

Limiting Oxygen Concentration (LOC) Work Update. Steve Summer Project Engineer Federal Aviation Administration Fire Safety Branch, AAR-440. International Aircraft Systems Fire Protection Working Group Ottawa, Canada July 8 - 9, 2003. LOC Testing – Work Update.

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Limiting Oxygen Concentration (LOC) Work Update

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  1. Limiting Oxygen Concentration (LOC) Work Update Steve Summer Project Engineer Federal Aviation Administration Fire Safety Branch, AAR-440 International Aircraft Systems Fire Protection Working Group Ottawa, Canada July 8 - 9, 2003 IASFPWG – Ottawa, Canada

  2. 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 IASFPWG – Ottawa, Canada

  3. Facilities – Pressure Chamber IASFPWG – Ottawa, Canada

  4. Facilities – Pressure Chamber • 353 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. IASFPWG – Ottawa, Canada

  5. 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 IASFPWG – Ottawa, Canada

  6. Apparatus – LOC Testing IASFPWG – Ottawa, Canada

  7. Apparatus – LOC Testing IASFPWG – Ottawa, Canada

  8. Ullage Vapor Sampling IASFPWG – Ottawa, Canada

  9. 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 msecond) 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 IASFPWG – Ottawa, Canada

  10. Oil Burner Transformer Voltage & Current Traces IASFPWG – Ottawa, Canada

  11. 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 IASFPWG – Ottawa, Canada

  12. 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 ms) • Hot surface vapor ignition (HSVI) IASFPWG – Ottawa, Canada

  13. LONG DURATION OIL BURNER TRANSFORMER ARC TEST RESULTS IASFPWG – Ottawa, Canada

  14. Aluminum Plate Relief Mechanism IASFPWG – Ottawa, Canada

  15. Foil Diaphragm Relief Mechanism IASFPWG – Ottawa, Canada

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  22. J-57 ENGINE SPARK IGNITER TEST RESULTS IASFPWG – Ottawa, Canada

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  25. SHORT DURATION OIL BURNER TRANSFORMER ARC TEST RESULTS IASFPWG – Ottawa, Canada

  26. Short Duration Test Results IASFPWG – Ottawa, Canada

  27. HOT SURFACE VAPOR IGNITION TESTING (HSVI) IASFPWG – Ottawa, Canada

  28. 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. IASFPWG – Ottawa, Canada

  29. 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. IASFPWG – Ottawa, Canada

  30. 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: ?? IASFPWG – Ottawa, Canada

  31. 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 IASFPWG – Ottawa, Canada

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