CHAPTER 8
POWER TRAIN AND
CONTROLLABLE PITCH PROPELLER
When we use the term power train in our
for the propeller blades and contains the hydraulic
discussions, we are using it as an overall term. This
servomotor mechanism for blade pitch control.
term covers the equipment and various associated
components that transmit the power developed
In this chapter, we will describe the power
by the GTE to the propeller.
train, its component parts and their functions, and
system relationships on gas turbine powered ships.
The power train of today's gas turbine
powered ships will consist of one or more of the
Among the various classes of ships, many
following components:
variations exist in the types of power trains.
The overall function and principle of operation
is the same in all of them. Some of these varia-
Main reduction gear (MRG)--reduces the
tions are significant enough that they will be
high-power turbine speed to a lower usable shaft
covered separately as that class of ship is being
speed.
discussed.
Clutch and brake assembly--connects the
Upon completion of this chapter, you should
power turbine to the MRG.
have the knowledge supporting the ability to (1)
identify and describe the main components of the
Oil distribution box (OD box)--part of the
power trains of today's gas turbine ships; (2) align
controllable reversible pitch (CRP) propeller
and operate the GTE support systems; (3) operate
system. It provides a means of sending hydraulic
the pumps, the turning gears, the oil purification
oil and prairie air (PA) through the gear and shaft
systems, and the engineering control systems from
arrangement to the propeller.
their local operating stations; (4) check system
performance; and (5) perform preoperational
Propulsion shafting system-transmits
checks and preventive maintenance on the oil
system.
thrust to the thrust bearing, and accommodates
the hydraulics system for the CRP propeller. It
consists of the
MAIN REDUCTION GEAR (DD,
propulsion shafting,
DDG, AND CC CLASS SHIPS)
thrust bearing,
On these class ships, the MRGs transmit the
power developed by the propulsion GTEs to the
line shaft bearings,
propulsion shafts. An MRG and its associated
equipment are located in each engine room. The
bulkhead seals,
MRG performs two major functions:
stern tube seals and bearings, and
It provides the flexibility of driving each
propulsion shaft with either one or two
strut bearings.
GTEs.
Hub-blade assembly-transforms the
It reduces the high-speed rotation from the
propulsion shaft rotational torque into axial thrust
gas turbines to the low speed required for
for ship propulsion. It also provides the mounting
propeller efficiency.
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