In case this helps.
The Rolls Royce publication of January 2000 – the Modern Gas Turbine, how it works and how it’s built – is a simplified description of the Trent 800 modular construction with line drawings of the various modules.
http://aircraftengineering.webs.com/gasturbines%5B1%5D.pdf
Module 01, LP compressor, “At the rear end of the shaft is a helical spline which transmits the drive from the LP turbine shaft.”
Module 02, IP compressor, “A stub-shaft at the front of the drum locates in the IP roller bearing, and a curvic coupling extends from the stage 6 disc to connect to the IP shaft.”
Module 05, IP turbine, “Bolted to the turbine disc is the turbine shaft which has helical splines at its forward end. These connect to the IP compressor stub-shaft via the thrust bearings in the intermediate case.
Module 07, LP compressor (fan) case, “At their inner ends, the fan OGVs are secured to the torsion ring which locates the IP compressor module,whilst the outer ends are bolted to the front mounting ring.This assembly is welded to the titanium rear casing and bolted to the front casing.”
Module 08, LP turbine, “The turbine shaft is bolted to the rotor via a curvic coupling and connects to the LP compressor shaft through helical splines at its forward end. The shaft extends rearwards into the roller bearing.”
What is still unclear is the method by which the spline joint is kept tight (my money still on torque). I have to say that I do not agree with Old Engineer about his geared coupling description.
Last edited by firstfloor; 7th Dec 2010 at 10:10.