Figure 10-19. Fuel Injection Nozzles
speeds also, but as speed increases, secondary parts
the engine with the proper air-fuel ratio over a broad
are opened, allowing additional fuel to enter the
band of operating conditions.
combustion chamber. This feature provides
Section V. LUBRICATION SYSTEM
be taken in selecting an oil that will not break down under
The lubrication system is
these severe conditions.
designed to clean, cool, and lubricate the internal
components of the engine. While each lubrication
10-18. Lubrication Oils. Lubricating oils used in gas
system is designed for a particular engine, certain
components are common on most systems. A wide
turbine engines must possess certain performance
variety of operating temperatures makes the design of
factors. Oils must resist foaming and provide a steady
the lubrication system even more difficult. Gas turbine
stream of oil to bearings. This ensures proper lubrication
engines operate in vehicles that can be exposed to
and cooling under all operating conditions. Mineral oil
temperatures as low as -60F (-51.1C), as well as
and synthetic oils commonly are used for lubricating
internal temperatures as high as 400F (204.4C). One
purposes in turbine engines, as discussed below.
a. Mineral Oils. Mineral oils generally are used in
severe problem experienced with gas turbine engines
occurs as the engine is stopped. A large amount of heat,
smaller, low-power engines and where temperatures do
stored in the turbine, then is transferred to the bearings.
not reach extremes. These oils generally are not used
This phenomenon raises the temperature of the bearing
because they are incapable of providing satisfactory
much higher than that encountered during operation.
performance at both very low and very high operating
The temperature of the lubricating oil, which is now
temperatures. They have been known to be extremely
stagnant around the bearing, also is greatly increased.
thick at low