Air Systems Flashcards
What are the 3 types of air systems
Compressor
Clearance
Engine cooling
What does the compressor control system do
Protect compressor against stall and surge
How are air sub-systems controlled
By hydro-mechanical fuel control unit of FADEC system
What does variable bleed vanes do
Bleed air from LP compressor into fan discharge duct which protects the LP compressor against stall and surge
What components protect against stall and surge
Variable bleed vanes and variable stator vanes
Why does the HPC surge at low rotor speeds
The forward stages deliver too much air to the aft stages
What does the variable stator vanes optimise
Optimise efficiency of compressor at high power settings
What does the bleed valve improve at the HPC
improves engine start and acceleration
What are start bleed valves used for
Start sequence
What does the clearance control system do
Optimise tip clearing in turbines and compressors
What does clearance control systems match
Match expansion of stator case with expansion of engine rotor
What does passive clearance do
Continuous cooling airflow
What is active clearance
Use cooling air control valves to optimise tip clearance by controlling quantity of air going to turbine case
How are active clearance valves controllled
Hydro mechanical fuel control unit or FADEC
What air does a compressor clearance control system use
Warm air to hear rotor
