Saturday, January 14, 2012

A total loss (expendable) oil system,Total loss (expendable) system :

Total loss (expendable) system :
Fig. 8-3 A total loss (expendable) oil system.

10. For engines which run for periods of short duration, such as booster and vertical lift engines,the total loss oil system is generally used. The system is simple and incurs low weight penalties
because it requires no oil cooler, scavenge pump or filters. On some engines oil is delivered in a
continuous flow to the bearings by a plunger-type pump, indirectly driven from the compressor shaft; on
others it is delivered by a piston-type pump operated by fuel pressure (fig. 8-3).
In the latter, the oil supply
is automatically selected by the high pressure fuel shut-off valve (cock) during engine starting and is
delivered as a single shot to the front and rear bearings. On some engines provision is made for a
second shot to be delivered to the rear bearing only, after a predetermined period.

11. After lubricating the fuel unit and front bearings, the oil from the front bearing drains into a collector
tray and is then ejected into the main gas stream through an ejector nozzle. The oil that has passed
through the rear bearing, drains into a reservoir at the rear of the bearing where it is retained by
centrifugal force until the engine is shut down. This oil then drains overboard through a central tube in
the exhaust unit inner cone.

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