gnusmas5441 t1_irpczq6 wrote
Reply to comment by Stealth_NotABomber in TIL that passenger jet engines produce most of their thrust from fan at the front, not from the jet exhaust, and that this is called a high-bypass engine. by Rilot
If I understand correctly, another challenge is finding and shaping materials that can withstand the forces generated by the fan blades spinning very fast and having to withstand, among other things, the forces generated by their tips moving much faster than their base at the center if the engine.
evanc3 t1_irpejoo wrote
Plenty of materials that can do this, the trick is to get one that doesn't creep over time because the blade tips are remarkably close to the engine wall (tip clearance)
slater_just_slater t1_irq2fgg wrote
Creep is why most 1st stage turbine blades are single crystal. Fun fact, single crystal blades are "grown" not cast.
They are also the most boring thing ever to look at under a metallograph.
evanc3 t1_irq2u47 wrote
Still blows my mind!
But yeah I can imagine lol
slater_just_slater t1_irq4gst wrote
What is interesting is that it's the same principle to how single crystal silicone is grown for microchip substrates. However the blades are hollow.
Since they have no grain structure, nothing responds to an acid etc, on a metallograph it's just a white blob.
They do have a thermal barrier coating (TBC)
One of my jobs as a process engineer at Rolls Royce was the TBC coating. If you are bored here is a link about it.
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