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Nitrogen Inerting Requirements – A Lit. Review

Nitrogen Inerting Requirements – A Lit. Review. Steve Summer Project Engineer Federal Aviation Administration Fire Safety Branch, AAR-422. International Aircraft Systems Fire Protection Working Group Atlantic City, NJ October 30 - 31, 2002. Background.

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Nitrogen Inerting Requirements – A Lit. Review

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  1. Nitrogen Inerting Requirements – A Lit. Review Steve Summer Project Engineer Federal Aviation Administration Fire Safety Branch, AAR-422 International Aircraft Systems Fire Protection Working Group Atlantic City, NJ October 30 - 31, 2002 IASFPWG – Atlantic City, NJ

  2. Background • Recent tests at the Tech Center produced inerting requirement data as a function of altitude. • This data contradicts the typical requirement of 9% O2 used by the military, but a literature search shows that it does not contradict any previous data on the subject. IASFPWG – Atlantic City, NJ

  3. IASFPWG – Atlantic City, NJ

  4. Background • Values lower than 11 – 12% have arisen due to two things: • A difference in ignition criteria • Pressure rise should be used as criteria, as overpressurization is what will cause catastrophic failure. • Safety factors added on to experimental values • Data has been taken at stoichiometric levels with a large ignition source (worst-case scenario), so a certain amount of SF is built into the data. IASFPWG – Atlantic City, NJ

  5. Ref. Kuchta (1986) IASFPWG – Atlantic City, NJ

  6. Previous Jet Fuel Data • Sam Zinn (1971) – Examined data as far back as 1946 from Boeing, Bureau of Mines, U of Cal., WADC, Convair, and Wright Pat • All found levels of between 11 – 12% O2 were sufficient to suppress ignition except for one. IASFPWG – Atlantic City, NJ

  7. Previous Jet Fuel Data • Stewart & Starkman (1955) determined a level of 9.8% • Criteria for ignition was any visual flame front. • It is noted in their report that at times, flame occurred with little to no pressure rise. • Their data does however verify the trend of decreasing inerting requirements as altitude increases. IASFPWG – Atlantic City, NJ

  8. Previous Jet Fuel Data • Kuchta@Bureau of Mines (1970) suggested a SF of 20% be added on to the LOC value. • It appears that this is where the current military standard of 9% has come from. • This added SF might not be needed as the tests were performed under worst-case conditions (i.e. stoich. mixture, large ignition source) IASFPWG – Atlantic City, NJ

  9. Conclusions • A literature search of previous experimental data shows excellent agreement with the current dataset that was obtained. • All reported levels that were lower than 11 – 12% O2 were due either to a disparity in ignition criteria or excessive safety factors added onto the experimental data. IASFPWG – Atlantic City, NJ

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