Why doesn't a Jet Engine melt??

Here's the answer to your question:



Apparently the complex geometry of the engine such as high-bypass ones which usually have up to 1000 different blades and tens of thoudsands of parts, helps in preventing the engine form melting.
It's quite astonishing when you think that we are talking about temperatures of up to 1800K, equivalent to 1527°C/2780.6°F
You also have to take into consideration that inside the engine the air flows at much higher speeds than the aircraft since it is highly compressed.

[edit on 27-5-2009 by Estess]

Originally posted by Kaytagg
Not that I'm saying this indicates conspiracy or whatever on the governments part, it's simply a fact that burning jet fuel will not be hot enough to melt steel.

It doesn't have to melt it.


It just has to reduce its mechanical stiffness enough, and the engine will destroy itself quite quickly.

reply to post by kilcoo316


Thank god there are others out there who realize that metal will fail even without melting.

Originally posted by Aim64C
reply to post by anonamousantichrist

 

I'd have to check the flash-point of JP-5, again... but most are designed with a very high flash-point (when the fuel ignites) to keep unintentional fires to a minimum.

Flash point ah yes but most people are very confused about flash point. Flash point is the temperature at which something gives off enough vapors to support combustion. Auto ignition is the temperature at which no outside ignition source is need to start combustion.

So what is the flash point of kero? quite low actually around 150 deg F. you could put out a match with kerosene. its auto ignition temperature is around 420 deg F

what does that mean to melting of jet engines? nothing. the engine doesn't melt because you are constantly putting air through it. you would damage an engine if you simply shut it down, you idle the engine to bring its temperature down.

flash point of gasoline incase you are wondering, -45 deg F but an auto ignition of 475 deg F.

Hi, I'm an aviation technician with jet certification and more than a decade of teaching, so please let me shed some light on this subject.

Turbine blades can work without melting because they are exposed to very high temperatures, but NOT FLAMES.

Ambient air is sucked in and compressed up to 9 times the outside pressure by the compressor. This is air that's not only compressed, but it's also in movement; like the air you blow on the candles in a birthday's cake.

Less than 20% of the intake air is used to keep the combustion process; the rest is used just to keep the flame centered. Using the birthday candle example again, it's like having two persons blowing the same one: the flame will position itself away from the wind.

Just as the candle, the flame in the jet engine could be extinguished if there's too much air entering the combustion chamber. There are air purge valves to avoid that. But what happens if there's not enough air?

Remember how the 80% of the air is required to keep the flame alligned? Well, if there's not enough air entering the engine, the flame will still be ignited, but there won't be enough air to keep it centered. When this happens, the flame makes contact with the metal and destroys it instantly. And since these engines work within very close tolerances, a minimal alteration makes the engine to start malfunctioning within seconds.

Why the turbine blades don't melt during a fire? Because they are made to withstand 1100º C WITHOUT DEFORMING. Fire has different temperatures within the flame, and the lower section of the flames has the lower value, as can be seen in this graphic:

/lfnnea

If the entire plane catches fire, flames can have temperatures between 600º to 1200º C. The blades, made out of nickel superalloys, can survive the fire without melting (1453º C melting point). The melting point of steel is around 1370º C. But the aluminum melts at 950º C. So, the fuselage can be lost but the engines will still be there. Damaged, but solid.

In summary:
1.- Jet engines work with air at very high temperatures.
2.- The flame doesn't touch the engine. If the flame makes contact with any part of the engine, it will fail instantly.
3.- Engines can survive fires because the materials they are built with have higher melting temperatures than the surrounding flames.

Originally posted by curbowbassplayer
Hi, I'm an aviation technician with jet certification and more than a decade of teaching, so please let me shed some light on this subject.

Turbine blades can work without melting because they are exposed to very high temperatures, but NOT FLAMES.

Run along kid and quit filling people's heads with bull#.

Its not appreciated.


NOTE: No-one pay any heed to the quoted post.

It may have some relevance to afterburners, but absolutely none to turbine blades.

[edit on 18/6/09 by kilcoo316]

news flash if you can make model rocket engines out of paper and black powder i think metal won't melt as easy as you think

If aircraft engines were to run at ISA [international standard atmosphere] which gives a temperature of +15c and a pressure of 1013mb they would not have a very long shelf life.

for the majority of the time the incoming air is on average -45c and the pressure quite low, also the faster the compressor fans turn the faster the turbine rotates so the air flow and temperature stay within limits.

The engine is mostly likely to fail on take off, high thrust, low speed, high temp, and high pressure, but the computer can reduce this in most cases, the weight of the aircraft, outside temp take off distance available and pressure are all keyed in, and although the crew push the throttles all the way forward the computer will only give you enough power to reach V1-V2, this can be overidden, in an emergency but it extends engine life and possible surge, or stall, this is when the air entering the engine cannot exit because of pressure, it is followed by loud bangs and flames exiting the engine that is sometimes wrongly associated with a bird strike.

Next time you fly in a 777 after about 20 seconds or so on your take off run, if you have an engine fail you can still take off and climb, on one power plant, imagine that, all those people, luggage, fuel, and metal, on one engine, incredible.

HAHA, I should not be suprised that a truther would be posting this on a site like ATS, but it tickled me a bit to see a post about jet engines turn into a discussion like this.