Hot air in Jet Engine

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When fuel is burnt in the jet engine, what is the major component of the hot gases thrown out of the back - the CO2 formed (I know CO2 is not the only component but it is the major one) from the fuel or the air entering the jet as a whole?

In other words, does the heat of the burning fuel spread very quickly to the surrounding air in the jet or does it take a lot of time?
 

FredGarvin

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sid_galt said:
When fuel is burnt in the jet engine, what is the major component of the hot gases thrown out of the back
Basic turbine emissions are Oxygen, some trace inert gases, water vapor and carbon dioxide. When we do emissions testing for our certification programs the basic areas we focus in on are:

- CO (carbon monoxide)
- NOx (oxides of nitrogen)
- smoke
- Unburned hydrocarbons

The basic fuel used in civil aviation is JET-A which is a kerosene based fuel.

sid_galt said:
In other words, does the heat of the burning fuel spread very quickly to the surrounding air in the jet or does it take a lot of time?
I'm not quite sure what you are asking here. The cycle is a continuous process, so once it starts, it is constantly going. Obviously, the rate at which the heat gets to the airflow in the engine will depend on quite a few things, but the effect happens quite quickly. Turbine inlet temps (ITT's) can spike up in less time than it takes your eyes to notice it has happened.
 

Q_Goest

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H20 makes up the majority of just about any fuel being burned.
 

brewnog

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sid_galt said:
When fuel is burnt in the jet engine, what is the major component of the hot gases thrown out of the back
I'd suggest atmospheric nitrogen...
 

Clausius2

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brewnog said:
I'd suggest atmospheric nitrogen...
In addition to what Fred has said, I would say the main damage of Jet turbines are NOx. Although all heat engines exhaust NOx, Jet turbines are the unique which do this at high altittude.

Usually NOx compounds need a lot of time (of order of years) to reach high atmospheric layers. On the other hand, jet engines exhaust NOx just at high heights saving up that time of delay and damaging the Ozone Layer.
 

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