Gas Turbine - Stall Flashcards
Stall
Partial blockage of air
Surge
Complete blockage
Deep Surge
Complete reversal of airflow usually marked by flames moving out the fan
Variable inlet guide vanes
Adjust angle to ensure air is directed onto first stage at correct AOA across operating conditions
Variable Stator Vanes
Adjust stator angle inside the engine to direct air at precise angle
Inter stage bleed valves
Vent pressure during start to improve axial flow across compressor
Advantage of multiple spools in high bypass engine
Allow each compressor to run at it optimal speed.
Improve overall engine efficiency and greater stall margin
What can trigger a stall in compressor
Reduced air mass flow/reduced thrust
High EGT with reduction in air mass flow
Damage/ice/extended incidence angles
Symptoms of a compressor stall
High EGT
Reduced thrust
Rumbling and banging from compressor
Fluctuating RPM/fuel flow
Avoiding Compressor Stall
Check for ice/damage
Avoid starting in crosswinds
Rolling T/O in crosswinds
Avoid extreme AOA
Axial Compressor is susceptible to
Stalls and surges
Centrifugal compressors are susceptible to
Surging
But not stalling
Engine Bleed Air is taken from
Taken from compressor stages
Reduces mass flow/increase EGT
Reduce in thrust/ Increase in fuel consumption
HP air is used to
Cool the turbine nozzle guide vanes/turbine blades and discs
Anti icing
LP bleed air is used
Cool accessories
