Chapter 11: Air System Flashcards
functions of air system
1) internal engine & accessory unit cooling
2) bearing chamber sealing
3) control of bearing axial load
4) control turbine blade tip clearance
5) engine anti-icing
function of INTERNAL air system
1) cooling of turbine blades/discs
2) cooling of NGV
3) cooling of combustor thru combustion liner
4) sealing of main bearing compartments in labryinth seal
5) thrust bearing load relief
function of EXTERNAL air system
1) customer bleed
2) nacelle ventilation
3) accessory cooling
4) TCC
5) engine anti-icing (using hot air)
what is customer bleed?
pressurised air taken out for airframe usage
what is bleed air used for?
aircon, pressurisation of aircraft
why is nacelle ventilation needed?
avoid accumulation of fluid vapour which can self ignite
which air is used for nacelle ventilation?
fan air
accessories cooled by external air
1) IDG
2) EEC
3) igniter lead & box
how many volts does the high tension lead / igniter lead carry?
22 kV
how is TCC controlled by?
EEC, which uses fuel pressure regulated by actuator
how does engine anti-icing system work?
hot air from compressor is delivered to IGV and inlet strut to prevent ice
how does variable guide vane changes its angle?
EEC signals to HMU > HMU provides fuel to linear variable differential transformer to adjust angle
which portion of the engine is air being tapped to cool down the ingiter?
low pressure compressor stage
