At higher altitudes, what is used to cool down aircraft engines?

Question

Water is used as a coolant for cars. Which fluid is used for jet engines? Someone told me it was water. Someone else told me it cannot be water because water freezes at higher altitudes. So which fluid is it?

Thanks!

P.S: I know air is partially used to cool down the engine, but i'm sure bypass air is not the only fluid cooling down the engine.

Answer 1

When talking about modern jet engines their are two air flows. The first is core air that is compressed through as much as 15 stages of compression and primarily used for combustion to drive the turbine which drives the fan section. The second is the fan air flow which provides most of the thrust. Secondarily, the fan air is used to cool the engine. It provides tubine case cooling air and primary heat exchanger airflow,. The short of it is that the shear volume of airflow through a jet engine is what provides most of the cooling. Older reciprocating high horsepower output engines such as radial engines used water injection for cooling at higher altitude.

Answer 2

Small aircraft have air cooled engines because they are lighter and less complex then water cooled engines. There is however a diesel engine that is on the market that does have water cooling. Not sure why it is water cooled other then its makes for better engine temperature control. The most engine cooling required is at low altitudes and high power setting when taking off and climbing to altitude so the cold of high altitudes is not available for cooling.

Answer 3

Air is used for cooling the engine. It is not the bypass air however. Also one must consider operations on the ground, where the air temp can be 110 degrees and the engine is producing maximum power.

Only about 10% of the air is used for combustion, the rest is for cooling and as a medium for thrust. The compressor air comes out at about the temperature of an oven but is still highly effective in large volumes for cooling the combustion chamber lining and the nozzles and turbine blades. The airflow ensures that none of the flames form combustion touch the sides of the engine and the turbine blades and nozzles are made hollow with many tiny holes to allow the cooling air through.

Additionally, fuel will cool it a bit due to vaporization (like how an air conditioner works) and the engine oil is cooled by air or fuel in heat exchangers (like radiators).

Answer 4

If you look at the diagram of a turbofan, (http://adg.stanford.edu/aa241/propulsion/images/pw4000.gif you can see that only about 25% of the air that passes through the turbofan makes it to the compression and combustion chambers. This means that the rest of the air travels over the shaft and cools down the whole engine.

This is why there are no fluids involved in cooling a turbofan. At higher altitudes, the air is also very cold. It is actually so cold that the engine needs anti-ice heating on the front of the air intake, so ice doesn't form and slow down performance or get sucked into the fan and cause trouble.

Answer 5

As stated many times above, air is the primary cooling of turbine engines, although the engine oil does help keep things cool. For small aircraft with reciprocating engines, besides air, the engine's oil is run thru a heat exchanger to help cool the engine.

Answer 6

Air is The only thing which cools the jet engine. Excluding any heat that lubricants carry off

Answer 7

there is no fluid to cool jet engines it is all air coold if you think about it. it can be 90 degrees at ground level and at 35,000 feet it is negative 60 degrees farenheit. and that is very cold. cold enough to keep anything cool.

Answer 8

it's all air.

Answer 9

Antifreeze