15.12 Flashcards
3 sub systems of air systems?
Compressor control system
Clearance control system
Engine cooling system
3 subsystems of compressor control system?
Variable bleed valve system
Variable stator vane system
HP compressor bleed valve system
What’s are air systems controlled by?
Hydro mechanical fuel control units or FADEC
What is main task of compressor control system?
Protect engine compressors from stall or surge
Where are variable bleed valves usually installed?
Behind low pressure compressor
Two methods HP compressor is protected against stall and surge?
Variable stator vanes
Bleed valves
Where are bleed valves found in HP compressor?
Mid or aft stage
What are clearance control systems used for?
Used to optimise tip clearances in turbines and compressors
What is purpose of clearance control systems?
To match expansion of stator cases with expansion of engine rotor
How do compressor clearance control systems differ from original?
They do not use cooling air on compressor cage
Instead they use warm air to heat rotor instead
What is pressure balancing?
A method to release axial loads on thrust bearings in the engine
What happens when pressurised air works on air seals?
Prevents oil from escaping out of bearing compartments
Compressor discharge air from aft stages of HP compressor cools what?
The nozzle guide vanes and rotor blades of HP turbine
Bleed air from intermediate stages of HP compressor cools what?
First stage nozzles and rotor drum of LP turbine
