2.11.
SUMMARY
The fuel system must supply clean, accurately metered fuel to
the combustion chamber. Most turbine engine fuel systems have the
same components: fuel control, pressure pumps, fuel flow divider,
manifold, and atomizers. There are two types of fuel controls:
hydromechanical and electronic. Enginedriven fuel pumps are high
pressure, positivedisplacement, gear type pumps, and the fuel
nozzles are either simplex or duplex. However, some engines use
vaporizer tubes in place of fuel nozzles. Some gas turbine engines
use a fuel oilcooler to cool the oil.
Section II. Lubrication Systems
2.12.
GENERAL
During the first few years of gas turbine experience,
lightweight, petroleumbase oil was suitable for gas turbines as well
as other types of engines. Most of the early engines used
lubricating oil conforming to MILO6081A, Grade 1010. Engines
requiring an extremely light oil were operated on MILO3519, Grade
1005. These were conventional petroleum oils of high quality and
light weight which met the requirements of all the older engines.
Because of the continuous demand for greater power, gas
turbine engines have been designed to operate at higher temperatures
and pressure ratios. Some gas turbine engine oil temperatures
encountered are considerably above the flash point of the petroleum
oils. Because of this, a high temperature lubricant had to be
developed. The oil used in all Army gas turbine engines is MILL
23699, or MILL7808. These are synthetic lubricants which have wide
operating ranges and load carrying capabilities. The MILL7808 is
used in engines operating below 25 F. OAT, and MILL23699 is used
when temperatures are above 25 F. This section discusses the
various components that make up a typical lubricating system.
2.13.
Lubricating systems for modern gasturbine engines are
relatively simple in design and operation, but their function is of
vital importance. The principal purposes of the lubricating system
are to clean, reduce friction, and to cool the bearing surfaces. The
main units of the typical system are the reservoir or oil tank, the
pressure pump, scavenger pumps, filters, oil cooler, and spray oil
jets. A schematic illustration of a gas turbine engine oil system is
shown in figure 2.12.
58
Previous Page
