Lube Oil System
craft forward. When foilborne, the PHM can attain
speeds greater than 40 knots. A disadvantage, however,
The LM2500 GTE lube oil system provides two
is that there is no provision for reversing the craft when
main functions: (1) it supplies cool oil to the gas turbine
the PHM is in the foilborne mode.
The basic foilborne propulsion system consists of
and heat, and (2) it supplies heat through the oil-to-fuel
the GTE (power plant), a power train assembly, and a
heat exchanger to heat the fuel for the gas turbine. The
propulsor assembly. In the following sections, we will
lube oil is stored in a 7.2-gallon oil tank located over the
examine the main components of the foilborne system,
engine. The oil is gravity-fed from the storage tank to
starting with its power plant, the LM2500 GTE.
the lube and scavenge pump mounted on the gas turbine.
The single-supply element of the pump forces the lube
o i l through tubes to the specific areas requiring
LM2500 GTE ASSEMBLY
lubrication.
A duplex filter mounted beneath the engine on the
The power for the foilborne system is provided by
starboard side provides filtration for the supply oil. A
a General Electric LM2500 GTE located in the gas
duplex filter mounted beneath the engine on the port side
turbine machinery room. This GTE is the same type that
provides filtration for the scavenge oil. The scavenge oil
is used in the twin-shaft and single-shall ships. The gas
housing assembly contains a magnetic chip detector.
turbine assembly consists of a gas generator, a power
The scavenge oil is filtered, cooled, and returned to the
turbine, a high-speed coupling shaft, and an exhaust
storage tank.
duct. At 100 percent power, this GTE is capable of
delivering 16,767 hp to the gearbox assembly at about
Fuel Oil System
3,100 rpm.
The GTE fuel system on the PHM is essentially the
The LM2500 GTE draws combustion air through
same as the fuel systems on other gas turbine-powered
knit-mesh filters located on the weather deck. The
ships. The PHM fuel system regulates and distributes
combustion air flows through the demister panels and
fuel to the combustion section of the gas generator,
the air intake plenum, which interfaces with the forward
providing a control over gas generator speed. Although
end to the gas turbine machinery room. A barrier wall
the power turbine speed is not directly controlled by the
and seal prevent any air from the area surrounding the
GTE fuel system, it is established by the gas stream
engine from entering the combustion air intake. The
energy level produced by the gas generator.
exhaust gases flow from the GTE exhaust duct through
primary and secondary eductor nozzles, which create a
flow of secondary cooling air through the gas turbine
Operation
machinery room. Located in the aft end of the gas
turbine machinery room is the foilborne engine exhaust
The GTE is started by the operator in the engineer's
collector. When the GTE is running, the exhaust works
o p e r a t i n g station (EOS). Throttle control then is
like an eductor to draw cooling air into this compartment
transferred to the helm (pilothouse) for foilborne
from ventilation ducts through the auxiliary machinery
operation. During foilborne operation, the monitoring
room No. 1. When the GTE is secured, fans on either
of operating parameters continues to take place in the
side of the combination air inlet finish cooling air for
E O S . Before the GTE is shut down, control is
the engine and its compartment. The exhaust gases
transferred back to the EOS where the GTE is shut down
eventually exit through the foilborne engine exhaust
by automatically controlled logic. Auxiliary functions,
stack located just aft of the superstructure.
such as the GTE machinery room cooling, compressor
washing, and engine waste drain pumping, are
In addition to the LM2500 GTE, the gas turbine
controlled by the operator in the EOS.
machinery room contains other foilborne propulsion
There is no local control at the GTE. The EOS
system equipment, including the foilborne engine lube
operator normally starts and stops the GTE by using the
oil supply and return falters, engine lube oil-to-fuel heat
automatically controlled sequencer. In case of system
exchanger, engine fuel heater, propulsor gearbox lube
malfunction or damage to the GTE, however, manual
oil-to-engine fuel heat exchanger for operating in cold
starting and stopping of the engine can be accomplished
areas, and propulsor gear lube oil-to-engine lube oil heat
at the EOS control console.
exchanger for operating in hot areas.
7-22
