2.16.
SCAVENGE PUMPS
Although much larger in total capacity, scavenge pumps are
usually constructed in the same manner as pressure pumps. Engines
are generally provided with several scavenge pumps to drain oil from
various parts of the engine. Often such a pump shares the same
housing as the pressure pump. These pumps are used to draw the oil
from the sumps at the bearings, accessory gearbox housings, and other
drainage points and return the oil back to the tank.
2.17.
FILTERS
Three basic oil filters or strainers are made: cartridge,
screendisk, and screen. These filters are the same design as the
filters used in the fuel system, as covered in paragraph 2.8. The
main objective of a filter is to remove all foreign particles from
the lubricant without creating excessive back pressure against the
pumps. Filters are usually provided with bypass valves to permit the
flow of oil in case the filter becomes clogged.
2.18. OIL COOLER
Oil coolers for aviation
gasturbine engines are either
simple oil radiators with air
cooling or the kind that uses
fuel as the cooling medium. The
latter type of unit is used on
the Lycoming T55 engine. The
fuel oilcooling unit is a heat
exchanger which transfers the
heat in the oil to the fuel
flowing to the fuel nozzles.
Since the fuel flow through the
cooler is much greater than the
oil flow, the fuel is able to
absorb a considerable amount of
heat from the oil, thereby
reducing the size and weight of
the cooler. The fuel oilcooler
is shown in figure 2.11 on page
57. An air cooler is shown in
Figure 2.14. Air Oil Cooler.
figure 2.14.
2.19.
SPRAY OIL JETS
The lubrication method most generally used is known as a
calibrated system, where oil is specifically controlled by a
calibrated
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