external manifold. From the manifold, the air is
Ignition Leads
piped forward and aft to ejector nozzles. Each
The ignition leads are low-loss connections
ejector contains a venturi through which the
between the ignition exciters and the spark
eighth-stage air passes; it draws enclosure air
igniters. They are coaxial leads with metallic
into the ejector. This air mixes with the eighth-
shielding that incorporates copper inner braid,
stage air, reduces the downstream pressure and
sealed flexible conduit, and nickel outer braid.
temperature, and increases the volume. Air from
the forward ejector is piped into the front frame
WATER WASH SYSTEM
hub; there it pressurizes and cools the A sump.
Some of the A-sump air passes through holes in
The purpose of the water wash system is to
the compressor rotor front shaft, through the
remove contaminants from the inlet and com-
rotor air duct, and through holes in the rotor aft
pressor sections. The system has a water
shaft; there it pressurizes and cools the B sump.
wash/rinse supply tank and piping attached to the
Air from the rear ejector is piped into the turbine
outside of the base enclosure. A flexible hose is
rear frame hub; it is used to pressurize and cool
attached from the inside base enclosure floor to
the D sump. Part of the air entering the D sump
the GG inlet duct at the 6 o'clock position. The
bleeds into the flexible-coupling shaft tunnel for
inlet duct is made with an internal passageway or
cooling and passes out the aft end of the exhaust
manifold which distributes water wash fluid to
duct. Some of the D-sump air passes through
outlet spray orifices. The outlet spray orifices eject
holes in the PT aft shaft, rotor air tube, and holes
the water wash fluid into the airstream flowing
in the rotor front shaft; there it pressurizes and
through the inlet duct.
cools the C sump.
BLEED AIR SYSTEM
Ninth-Stage Air
Air extracted from the compressor for cooling,
seal pressurization, pressure balance to reduce
Ninth-stage air is bled from the compressor
rotor thrust loads, and ship's service (secondary)
through holes in the ninth-stage vane bases and
air is called bleed air. For this application, air is
compressor casing into an external manifold.
bled from the 8th, 9th, 13th, and 16th stages. Only
There it is piped to the turbine mid frame and
16th-stage air (known as CDP) is used for the
turbine rear frame. Air enters the turbine mid
ship's bleed air system. Refer to figure 1-33
frame through all the struts. Some of the air
(At the end of chapter 1), which shows the
exits through holes in the frame hub to cool the
LM2500 GTE airflow, to help you understand the
frame inner liner. The rest of the air enters tubes
following discussion.
in the C-sump air seals; after it crosses these seals,
the air passes through and cools the PT rotor. It
Eighth-Stage Air
then exits into the PT exhaust gas. The air to the
turbine rear frame enters the frame through struts
Eighth-stage air is bled from the compressor
2 and 8. It passes into an area between the
through hollow eighth-stage stator vanes into an
Figure 2-52.--Balance piston principle.
2-46
