FAA approach to fuel inerting

[PickyPerkins]

Here ia an article (http://www.msnbc.com/news/847080.asp?0na=x22022G1-), but it doesn't say how the oxygen content in the tank is reduced.

[Flash2001]

I think that this system is old hat. It was proposed for the Marine V22 in the form of OBOGGS and OBIGGS. These were respectively:

On Board Oxygen Gas Generating Systen and:

On Board Inert Gas Generating Systen and:

It fractioned source air to the Marines and the Fuel tanks.

[PickyPerkins]

Flash2001 ".... It fractioned source air ......."
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What does "fractioned" mean?

Does this involve the separation of oxygen from nitrogen by evaporation of liquid air?

If so, is there an air liquifier on board, or do you have to fill a storage tank on the a/c with liquid air before take off?

Supertanker ships use engine exhaust gases for inerting. Many supertankers were lost to explosions before exhaust gas inerting was introduced.

Why can't this method be applied to aircraft (maybe with some special attention to eliminating corrosive products of combustion)?

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[jettison valve]

To my understanding, Boeing and Airbus will go for rather simple devices; you will litterally press bleed air through ceramic filters with catalytic properties, which will strip a fair amount of oxygen off the bleed air. Sorry if some of the words aren`t proper english - but I`ve missed all "english for chemical engineers" courses so far...
In the presentations I have seen, there were almost no moving parts (except for valves of course!). The key issue however seems to be to stay in a tight temperature/pressure/flow area...
Unfortunately (or: Fortunately ;-) ) I have the papers at work, not here.

Keep in mind that at least the retrofit solutions (if the FAA really pushes us into that!) must be ... well... retrofitable (in terms of space, consumption, cost etc.).

Cheers,
JV;)

[PickyPerkins]

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jettison valve ....... litterally press bleed air through ceramic filters with catalytic properties, which will strip a fair amount of oxygen off the bleed air. ........ almost no moving parts ....... stay in a tight temperature/pressure/flow area...
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This sounds different from the "fractionating" system, and more like a car catalytic converter.

While in a car the objective is to reduce the hydocarbon content, in the aircraft its to reduce the oxygen content. The chemistry and the catalyst may be the same.

So in this case maybe hot bleed air under pressure with some fuel vapor is passed (pressed) through a hot ceramic catalytic converter consuming most of the oxygen, and thus producing air with a reduced oxygen content?

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[Flash2001]

I guessed that it was a fractional distillation system but I don't know. The filter option strikes me as large and vulnerable, undesired in a military aircraft. The fractional distillation system would be small and complicated. I'd be interested to hear from anyone who actually knows.

After an excellent landing, you can use the airplane again.

[jettison valve]

hmmm... It seems like I brought you on a wrong track with the word "catalytic"...
If I remember correctly, they basically will make use of the different sizes of nitrogen and oxygen molecules. If you push bleed air towards a filter with holes of a size between N2 and O2 molecules, only the N2 molecules will be able to pass the filter. On top of that, some fancy surface treatment will help this filter function... Not to many similarities to the device in our cars, I am afraid...

PickyPerkins: Don`t tell the FAA about your idea with the fuel vapours in the bleed air - they will immediately ground you... ;)

[Flash2001]

I didn't think it was catalytic. Only that given the small size/mass difference between oxygen and nitrogen molecules, it would involve a fairly large cascade to achieve a substantial amount of separation.

After an excellent landing you can use the airplane again.

[jettison valve]

a brief search in the net got me to:

http://www.fire.tc.faa.gov/systems/fueltank/hfm.stm

this is pretty much what I had in mind... membranes, molecule sizes, temperature, pressure, flow - but see for yourself!

cheers,
JV

[PickyPerkins]

jettison valve ….a brief search in the net got me to: ……
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Thanks - Full marks and bonus points for a complete answer to my original question. :)

Looks like the system will take out some of the moisture as well as oxygen.

I think I have heard of a similar system being used for removing salt from sea water.

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