Limiting Oxygen Concentration (LOC) Work Update：极限氧浓度（LOC）工作的更新

1、Limiting Oxygen Concentration (LOC) Work UpdateInternational Aircraft Systems Fire Protection Working GroupAtlantic City, NJNovember 5 - 6, 2003Steve SummerProject EngineerFederal Aviation AdministrationFire Safety Branch, AAR-44011-05-03LOC Testing Work UpdateTechnical Note consisting of all data e

2、xcept 400 cycle short tests published and placed on website (AR-02/79)400 cycle short spark energy has been measured and testing has been completedFinal report currently being put together11-05-03Facilities Pressure Chamber11-05-03Facilities Pressure Chamber353 ft3 pressure vesselWorking pressure of

3、 650 psi.Attached vacuum pump used to evacuate chamber to reduced pressures seen at altitude.Not capable of simulating temperatures seen at altitude.11-05-03Facilities - LOC Test Article 9 ft3 simulated fuel tank placed inside of vessel equipped with:Bottom surface heaters.12 thermocouples.2 piezore

4、sistive pressure transducers mounted behind sintered porous metal discs.Interchangeable pressure relief mechanism.-in. aluminum plate.Foil diaphragm.Spark gap.2 tungsten electrodes with controllable gap alignment and spacing11-05-03Apparatus LOC Testing11-05-03Apparatus LOC Testing11-05-03Ullage Vap

5、or Sampling11-05-03LOC Testing ApparatusIgnition Sources10 kV Oil burner transformer operating at 30 mA provided both long (1 second) and short (0.1 second) arcsJ-57 Engine spark igniter provided a very short (175 msecond) spark3 x 6 x 1 metal block heated by two cartridge heaters to temperature in

6、excess of 1400F400 cycle, 120 V hard short to ground provided high energy/current, short duration sparkEnergy MeasurementsVoltage and current traces were taken using a HV and current probe at the spark gap connected to oscilloscope11-05-03Test ProgramJP-8 LOC TestsMass Loading 4.5 kg/m3Ambient press

7、ure corresponding to altitudes of 0, 10, 20, 30 and 38 kftUllage oxygen concentrations ranging from 21% to below the determined LOCTests conducted with two different pressure relief mechanisms-in. aluminum plate Ignition = movement of plateFoil diaphragm Ignition = rupture of foil11-05-03Test Progra

8、m (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 sourceShort duration oil burner transformer arc (0.08 J, 0.1 s

9、)J-57 Engine igniter spark (0.5 J, 175 ms)Hot surface vapor ignition (HSVI)400 cycle, 120 V hard short to ground11-05-0311-05-03400 Cycle Hard Short Tests11-05-03Spark Energy MeasurementsEnergy 2.2 JDuration .006 sEnergy 2.8 JDuration .01 sEnergy 1.75 JDuration .01 s11-05-03400 Cycle Short Test Results11-05-03Summary2 J spark from 400 cycle short did not cause a change in the LOC at sea levelOf all ignition sources used (oil burner arc, engine ignitor spark, hot surface, 400 cycle sh