2.14.
OIL TANKS
Most gas turbine engines are of the drysump type, meaning the
on is stored separately from the engine, or the tank may be attached
to a structural part of the engine. Usually constructed of welded
aluminum or steel, it can contain a venting system, a deaerator
(baffles) to separate air from the oil. Some systems use an oil
level transmitter to indicate quantity, where others have a dipstick
or visual sight gage.
2.15.
PRESSURE PUMPS
Oil pumps for turbine engines are usually of the positive
displacement gear type, with a relief valve to prevent excessive
pressure. A modified geartype pump is called the "gerotor pump."
The geartype pump consists of a driving and driven gear. The
pump is driven from the engine accessory section and causes the oil
to pass around the outside of the gears in pockets formed by the gear
teeth and the pump casing. The pressure developed is proportional to
engine rpm up to the point where the pressure relief valve opens and
limits the pressure output of the pump.
The gerotor pump has two
moving parts, an inner toothed
element meshing with an outer
toothed element. The inner
element has one less tooth than
the outer, and the missing tooth
provides a chamber to move the
fluid from the intake to the
discharge port. Both elements
are mounted eccentrically to each
other, the inner one mounted on
the shaft and the outer one
meshed with it. Figure 2.13 is a
picture of the gerotor pump,
showing both inner and outer
Figure 2.13.
Gerotor Booster
toothed elements.
Pump.
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