Rolls-Royce 1004227 - Manual (Page 33)

EPR Proprietary I Licensed Material
Rolls-Royce Aero-Derivative Combustion Turbine Background
2-7
stop the bearing cavity can see temperatures in excess of 400 degrees
in the ninety minutes following a crash stop. Whereas, on a cool stop
that cavity temperature only got up to just over 275 degrees. No oil in
the world can stand the former temperature, without laying down some
coke.
Secondly, to allow for the emergency stops – fire, gas in the building
etc. modifications were incorporated to get cool air into the 05 Bearing
Cavity after such an event. A Davis valve (Mod 1136) has shop air
connected to one inlet. When the engine suffers a crash shutdown, the
valve opens allowing shop air to pass, via the vent lines, into the
bearing cavity thus keeping it cool. Mod 1135 was also introduced to
allow a double vent of this cavity, and Mod 1123 fits a new connection
on the 05 module that a pressure gauge can be installed to set the shop
air pressure to the bearing cavity.
Service experience has shown that the combination of these
modifications has greatly reduced the amount of oil ‘coking’ seen in
this bearing cavity.
H.P. Compressor – Stage 5 Vanes:
There have been incidents of High Cycle Fatigue cracking on Stage 5
H.P. Compressor Vanes. It has been associated with Operators who
experience extremely cold ambient conditions. It has also occurred
when the bleed valves have been way out of their schedule, or the
bleed valve controller has seized.
Mod 1275 introduces the ‘spade foot’ stator to overcome this problem.
DLE Combustor Noise: Mod 1313 has gone a long way toward reducing the ‘noise’ in the
DLE combustor. This modification introduces Asymmetric Fuel
Injectors in the Primary combustion area.
However, 30% of the engines still had unacceptable levels of noise.
Asymmetric or split Secondary Fuel Injectors are now being
introduced
Trent Background Information
The industrial Trent design uses much of the aero Trent 800 engine core with the addition of a
new two-stage low-pressure compressor (LPC) in lieu of the high-bypass wide-chord fan on the
aero Trent. The main difference is the radical change to the DLE combustion system with eight
can-type combustors that are reverse-flow combustion design, radially mounted, perpendicular to
the axis of rotation. The DLE concept has been designed in the industrial Trent upfront.
Initially, the unit had difficulty meeting 25 ppm NO
x
emissions. A Wet Low Emission (WLE)
version has been developed and has been running in the UK. On-line emissions monitoring