s
Figure 6-21.—Power turbine.
The power turbine (fig. 6-21) is a multistage
is that the gas turbine engine has only one
unit located behind the gas-generator turbine.
There is no mechanical connection between the
two turbines. The power turbine is connected to
a reduction gear through a clutch mechanism. A
controllable reversible-pitch (CRP) propeller is
used to change direction of the vessel.
Accessories
Because the turbine and the compressor are on
the same rotating shaft, a popular misconception
moving part. This is not so. A gas turbine engine
requires a starting device, some kind of control
mechanism, and power takeoffs for lube oil and
fuel pumps. The accessory drive section (fig. 6-15)
of the gas turbine engine takes care of these
various accessory functions. The primary purpose
of the accessory drive section is to provide
space for the mounting of the accessories required
for the operation and control of the engine. The
accessory drive section also serves as an oil
6-14
