15.10 Flashcards
(14 cards)
Full flow oil system
No way of regulating the oil pressure
Oil pressure changes with changes in the rotor speed (n2), oil temp and flow areas downstream.
Supply pump is driven by N2 rotor system
Higher temp = lower viscosity = lower pressure.
A leakage = increase in total flow areas = less pressure.
A pressure relief valve is fitted.
Constant pressure oil system.
Regulated pressure system
Uses a pressure regulator valve.
Holds oil pressure at a given value from idle to maximum.
Holds pressure difference between oil pressure and vent pressure constant.
Comparison of full flow and constant pressure oil systems.
Both are suitable systems
Full flow is simpler with no adjustments needed
Full floe needs high oil pressure at idle.
Significant rise in oil temp. after a power reduction (full flow)
Exhaust turbine bearing
Lubricating oil for bearing
Cooling requires an oil cooler.
What are oil tanks made of
Aluminium coated with silicone for fire resistance.
Gerotor type oil pump
Less common
Single element for oil pressure
Several elements for scavenging oil.
Capacity of elements can. Be controlled by varying size of elements.
Gear type oil pump
Only two elements - one for pressure, one for scavenge.
Most common type.
Where are oil pressure relief valves especially important
On oil coolers and filters.
Where is a last chance filter found
Upstream of oil nozzles
If the oil cooler is in the supply line is it a hot tank or a cold tank
Hot tank.
Oil system venting
A breather removes air from the scavenge oil. The air vents overboard.
A de-aerator separates the air from the incoming scavenge oil.
Capacitance type transmitter
The principle is based on the capacitance change of the capacitor.
Reed-type transmitter
Metal tube with a float. Uses a chain of reed switches.
Oil contamination debris monitoring.
Magnetic chip detector.
Manually checked at periodic intervals.
Can be electronically monitored.
