15.12 Air Systems Flashcards
(22 cards)
What is the ideal air/fuel ratio?
15:1
What is the acceptable range of engine temperature?
800-1150 degrees
What is the function of secondary air?
Cools combustion chamber liners
What does zone 1 consist of?
Area around fan case containing accessory case and EEC
How is zone 2 cooled?
By fan air
What does zone 3 consist of?
Area around the HP compressor to turbine cases
What are the 3 zones in an engine divided by fireproof bulkheads?
Fan case compartment, intermediate compressor case, core engine compartment
How is the engine exterior and engine nacelle cooled?
Fan air
Where is anti ice used?
Engine inlet cowls
How is anti ice controlled?
Automatically by switch in flight deck
What % of air is used as primary airflow?
20-30%
What % of air is used as secondary airflow?
70-80%
How is the life expectancy of NGVs and turbine blades increased?
Cooled by compressor air
How do cooling systems benefit turbine NGVs and blades?
Allow them to operate 300-400 degrees above their limits
How is accessory cooling air provided?
From intakes in the fans cowling or from specific compressor stage
How is the compressor rotor cavity cooled?
From IP compressor air
What is the temperature of the rear compressor stages?
350-400 degrees
How does pressurised air affect engine bearing chambers?
Provides additional sealing
What is used for the sealing of engine bearing components?
LP compressor bleed air
Where does the air entering bearing compartments vent?
Through N1 rotor shaft
Why is air often bled from the highest pressure stage?
Because pressure and temperature are at their max
What is a bowed rotor?
Where the engine can bend due to different expansions of upper and lower zones after engine shutdown
