# Presentation: 423820

## Limiting Oxygen Concentration (LOC) Work Update

- International Aircraft Systems Fire Protection Working Group
- Ottawa, Canada
- July 8 - 9, 2003

- Steve Summer
- Project Engineer
- Federal Aviation Administration
- Fire 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 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.

## 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.
- 1⁄4-in. aluminum plate.
- Foil diaphragm.
- Spark gap.
- 2 tungsten electrodes with controllable gap alignment and spacing

## Apparatus – LOC Testing

## Apparatus – LOC Testing

## 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

**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
- 1⁄4-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

**Aluminum Plate Relief Mechanism**

## Foil Diaphragm Relief Mechanism

**Foil Diaphragm Relief Mechanism**

## Slide 16

## Slide 17

## Slide 18

## Slide 19

## Slide 20

## Slide 21

## J-57 ENGINE SPARK IGNITER TEST RESULTS

## Slide 23

## Slide 24

## 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