How does a jet engine work with no oxygen?

Question

When its flying at 40,000 feet. How does it get combustion without oxygen?

I honestly don't know how I'm going to choose best from these answers, their all good.

Answer 1

Who says there isn't any oxygen at 40k feet?

Answer 2

That's a good question Jim, and Valcyrilestrada's got the right idea about the compressor. The Compressor Section of a jet engine does exactly what it says; it takes a volume of air and through compression, effectively "increases" the oxygen molecules present in the "reduced" compressed volume of air before entering the burner section, so that AFTER COMPRESSION, there's plenty of oxygen molecules available for combustion. P.P.S. I just re-read some of these answers and I can see why you can't make make up your mind...There is simply a lot of misinformation here and I'm going to try one last time and then quit!! An example: The percentage of Oxygen in a parcel of air is approx. 20%..ALWAYS!!!...meaning: if there were 100 molecules of oxygen at sea level, and 500 molecules of "other gases" the 20% is satisfied......if, however, we are at 70,000 feet and the pressure is very reduced the air "expands" due to that reduced pressure in order to fill a given volume....as the air expands, the molecules are "diluted" and now there are maybe 2 oxygen molecules in the same volume, of air, along with only 10 molecules of "other" gases...(DON'T FORGET!!..YOU ARE APPROACHING THE VACUUM OF OUTER SPACE.....SOON THERE WILL BE NO AIR AND NO OXYGEN!!!) .........but the RATIO is the same,eh? 20%!!.........but do you think your body or the combustion section of that engine could operate on 2 molecules of oxygen? And the air that you are breathing is NOT the same air that's outside the airplane at 40,000.....THERE ARE NOT ENOUGH MOLECULES OF OXYGEN IN THAT AIR!!......IT HAS TO BE COMPRESSED TO CONCENTRATE THE OXYGEN MOLECULES!!.......perhaps 50 volumes of air are compressed by the engine to get enough oxygen molecules now into that SINGLE volume of air such that there is sufficient oxygen. And now, I give up!!

Answer 3

There's plenty of oxygen at 40,000 feet. Remember that cabin pressurization uses compressed air from the engine compressors ("bleed air"); so you are actually breathing air from 35,000 or 40,000 feet while you ride along in the cabin.

It's just been compressed by the engine intake compressors, so as to be dense enough to provide for human breathing needs. So the air is less dense than it is a sea level, but the percentage of oxygen is about the same.

In fact the bleed air is so hot as a result of having been compressed, that it has to be cooled through a heat exchanger (called an "intercooler") before being fed into the cabin air conditioning.

Answer 4

There is oxygen at 40,000 feet. It's just not concentrated enough for a human to breathe properly.

Answer 5

The huge compression in a high-bypass turbine engine allows the RELATIVELY low amount of oxygen to support combustion.

Also the engine moves more air than just the air that is combusted. That is what makes is a high-bypass turbine.

As much as 50% of the air going into the front of the engine is never "burnt."

Answer 6

There is oxygen at 40,000 ft....the atmosphere is about 1/4 as 'thin' as it is at sea level.
Depending on design..some jet engines can operate in very rarified atmospheres up to 70-90 thousand ft or even higher (scram / ram jet)
Oh yes.....if there wasn't any O2....a jet engine would not work. Period

Answer 7

the wonderful world of suck ,squeeze, bang and blow. the turbine engine is a big compactor. It gathers the minute oxygen at altittude, squeezes it together and presto! there is enough oxygen to sustain combustion. Which directly correlates into why they travel so high. Your fuel/air mix is directly related to each other. The less air, the less fuel you will need to maintain a proper mix. The FADEC, along with the sensors in the engine, determine how much fuel is needed to maintain combustion.
The SR-71, while its over fourty years old, can and still does exceed alt of 110,000 ft. During Desert Storm, I mid air refueled an SR that during comms was decending through 115,000ft at mach 3.0. Thats efficiency.

Answer 8

Aircraft travels at the altitude of 40000 ft above sea level, While the percentage of oxygen in the atmosphere remains fairly constant up to 70,000 feet

Answer 9

without O2 it doesn't work.

Fortunately they have compressor sections and since the O2 has the same percent volume at 40K as at SL they operate just fine.

Partial pressures of atmosphere are no big deal when you have 9 stages of compressor working for you.

Wikipedia jet engines so you can see how they work.

Ret. USAF SNCO- Acft Tech

Answer 10

there's obviously enough oxygen up there to keep it flying.

A rocket, on the other hand, burns its own gases that it brings along with it, unlike a jet which needs to take in air from the outside to make combustion.

Thats why a rocket like the space shuttle can make fire even when its in outer space.

Answer 11

liquid oxygen for the shuttle and at 40k theres oxygen