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I'm designing an aircraft, and I notice that in high bypass turbofan engines, the fuel is used at relatively low temperatures. So I'm wondering, what happens if the fuel is burned at high temperatures? Does something happen to the metal?

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The biggest limiter of hot section temperatures in aviation gas turbines is moving hot section parts subject high stress loads under high temperatures and do so for very long periods of time. Even the best nickel cobalt superalloys cannot maintain acceptable yield strengths past about 2000°F. Some additional solutions have utilized to achieve even higher TIT levels such as novel single crystal casting techniques for the rotor buckets as well as using bleed compressor air to envelop the surface of the buckets to protect them against the high temperature exhaust gases. Some military engines can operate with TITs as high as 2600-2700°F. Another proposed option has been to manufacture the buckets, stators and hot section casings out of carbon composites, which hold the promise of increasing TITs as high as 4000°F. However carbon composite blades are susceptible to oxidation before reaching these temps, making it difficult to realize this. General Electric Aircraft Engines may be on the cusp of solving thes problems; if they do, a composite gas core would offer a quantum leap in power and efficiency.

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If you burn it too high, the metal may melt. If you have the air too hot, the air molecules will become less dense and burn less, therefore, creating less of an explosion and making less thrust. I hope this helps.

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  • $\begingroup$ Ok. I'll keep that in mind. $\endgroup$ – Nicholas Oct 28 '16 at 5:09
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    $\begingroup$ First part, yes. Second part, no. Hotter combustion will lead to higher trust (it also means more tightly compressed air to arrive at that temperature). If your combustion chamber didn't melt and nitrogen wouldn't form all those pesky NOx toxins, we would have much more efficient engines. $\endgroup$ – Sanchises Oct 28 '16 at 6:17
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    $\begingroup$ The fuel-air mixture in gas turbine engines does not explode; it burns with a continuous flame. $\endgroup$ – J Walters Oct 28 '16 at 13:18
  • $\begingroup$ If there were an ignition source after the low-pressure system, is there much left in the turbine that would be affected? Would that even allow increased combustion? Also, do NOx compounds occur in combustion, and is it in such a trace amount that it doesn't really have an effect? $\endgroup$ – Nicholas Oct 31 '16 at 18:01

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