15.12 Air systems Flashcards
(32 cards)
What temperature are the hot sections of the engine?
800 to 1150 c when a larger volume of air enters than whats necessary for the 15-1 ratio
Wheres the hottest section of the engine?
around the turbines
What cools the combustion chamber liners?
Secondary air passing through the engine
What is the most critical lubricating point in a GTE:
The exhaust turbine bearing bc of the high temps present
may be cooled by both air and oil
How is the engine exterior and the engine nacelle cooled?
By passing fan air around them
How are turbines engines different primary zones isolated?
by a fireproof bulkhead or seals.
What is Zone 1 and how is it cooled?
Around the fan case, accessory case and EEC
Cooled by RAM air via nose cowl inlet
Exits through a panel in the right fan cowling
What is zone 2?
Intermediate area around th engine
Cooled by fan duct air, exhausted into fan stream
What is zone 3?
Around HP compressor to turbine cases
Contains fuel, oil lines and accessories
Cooled by compressor bleed air
Why is zoning used?
Keeps airflow controlled and maintains safe compartment temps
Why is anti-icing needed?
Ice can form on engine inlets and guide vanes in cold, moist conditions.
This ice:
Disrupts airflow → reduces compressor efficiency.
Breaks off → (FOD) to compressor blades.
How does anticing work?
Hot bleed air directed to the leading edge of the inlet cowl and guide vanes
Prevents ice formation
After heating the lip the air exits through a grill on the nose cowl
How is anticing controlled?
Mnaually selected
Or automatically controlled via a cockpit switch
Why is internal cooling needed?
Cooling improves:
Component life
Combustion efficiency
Overall engine performance
How is the compressor cooled?
Cooling air from intermediate compressor stages is routed into rotor cavities to reduce material stress
What temperatures do the rear compressor stages reach?
350–400°C
How is the airflow split in the combustion chamber for cooling?
20–30% primary airflow enters the liner for combustion; 70–80% secondary airflow cools the liner and centres the flame.
What is the function of film cooling in the combustion liner?
To create a thermal barrier between hot gases and liner surfaces.
How are turbine blades and vanes cooled?
Compressor discharge air flows through internal cooling holes in blades and over guide vanes
What is a rotor cavity?
An enclosed space around rotating components used for cooling, sealing, and pressure balancing.
How are accessories like generators cooled?
Using fan air or compressor bleed air, and air-cooled oil coolers for lubrication systems.
What are the main parts of the engine that require internal cooling?
Compressor, combustion chamber, turbine discs, turbine blades/vanes, accessories.
What is the purpose of sealing in a gas turbine engine?
To prevent oil from leaking out of bearing chambers and keep air/oil separation.
What type of air is used for bearing chamber sealing?
LP compressor bleed air.
