Thread: Turbine Blades

I remember talking to an RAF engineer years back about this up at RAF Leuchars. He told me the blades are made out single crystal titanium.

They're made out of titanium for the weight and the heat resistance (they cool down fast), and they become single crystal by a succession of heating and slow cooling to remove the microscopic fault lines in the metal.

Jet engines rotate at up to 100,000rpm, so the centrifugal force on even the small blades can be up to 40 tonnes. If they werent single crystal they would fly apart under the pressure.

The compressor blades are also hollow and have small needle sized holes on the leading and trailing edge and air is pumped through the blades to keep them cool.

The large front fan on turbofan engines doesnt have hollow blades, but they take a stupid amount of force when the engine is running at take off speeds. I cant remeber what it was exactly, but it was over 100 tonnes of centrifugal force IIRC.

The blades in these engines get replaced pretty often as you can imagine!

EDIT: Just seen Tazz's post with the pictures of the blades. You can see the holes clearly in those pics!

Interesting thread, made me think about a steam turbine I saw at a natural gas power plant in the laydown yard. From what I remember though, i believe it was some sort of alloy as well. Maker was GE though. One of the turbines was damaged in shipping and GE brought some Korean (where it was made/put together) engineer to look it over. The ended up installing it and it didn't even make it thru start-up trials. Something about balance issues. That thing had some huge blades though,,,