Annex14
Here are the cutaway views of the two engines. Although one cannot see the details clearly, the general engine layout and differences can be seen. To see the actual details, one has to view the engine and see all the parts laid out on tables.
http://www.pw.utc.com/StaticFiles/Pr...taway_high.jpg
http://www.rolls-royce.com/Images/br...cm92-11346.pdf
Several things strike me: If there is any scale at all between the artistic renditions, the thrust ball bearings in the GP7200 look larger than those in the Trent 900. In the turbine area of the GP7200, the emphasis on slowing a speeding turbine rotor can be seen on both rotors where there would be blade on vane contact, there is no spacing concerns. The stage two turbine rotor (similar to the IPT rotor of the Trent 900) sits close to the structural frame behind it and the blade would contact the struts if this turbine disc were to move back.
Both engines deliver the same thrust, both have the same fan diameter, both have 14 compressor stages, the GP7200 has 6 LPT stages verses 5 for the Trent 900. The GP7200 is slightly longer and weighs 956 lbs. more. It has been reported the GP7200 has a 1% better SFC than the Trent 900, but RR disputes this. Both engines appear to be capable of being mounted on a common designed pylon. The maximum HP spool speed of the GP7200 is slightly higher than the Trent 900, but the maximum fan speed is lower on the GP7200.
For those wondering why the Trent 800 couldn't be used, you can't just clip 5" off the fan without rebalancing the rest of the engine, especially if you are being pressed on SFC to meet aircraft range goals. So two things happened on both engines, incorporation of 3-D highly aerodynamic efficient swept fans, higher HP spool speeds, higher pressures and temperatures, all to generate thrust requirements and deliver good SFC.
I do wonder if the counter-rotational feature (new to a commercial high by-pass engine) had any effects on bearings, frequencies or vibration in the Trent 900.