PT6 General question.
 

Hi all, I have a question regarding the PT6 Engine, I just want to know why the shafts rotate in oposite directions (the compresor and the power turbine), I have read that this is a more efficient way to transfer rotational force, but i haven't found yet a good explanation of it.

Tanks for your help!

Andres

Hi,

I'm not sure of the exact reason on the PT6 but it has been used on larger gas turbines to improve the turbine efficiency. By counter rotating the shafts, the turbine nozzle guide vanes between the gas generator and the power turbine have to turn the air through a smaller angle thereby improving efficiency. Most new generation engines utilise this e.g. Trent 900, GEnx and maybe the GP7000. I believe it was first introduced on the BAe Harrier Pegasus engine though.

On smaller engines it may be used to reduce the induced gyroscopic forces?

Cheers,

P2C