Module 15.12 Air Systems Flashcards
What would the internal temperatures be if there was only an ideal air/fuel ratio of 15:1?
2200 °C
What temperature does the large volume of air cool the hot sections of the engine to?
800 to 1150 °C
What is the most critical lubricating point in a gas turbine engine?
The exhaust turbine bearing.
What two ways are exhaust turbine bearings cooled?
Air cooling and oil cooling.
Where are cooling air inlets located?
Around the exterior of the engine.
Why are cooling air inlets needed?
To cool the turbine case, bearings and nozzle.
How is the engine exterior and nacelle cooled?
By passing fan air around them.
How do the engine zones isolated from each other?
Fireproof bulkhead or seals
What is zone 1?
Fan case compartment.
What is zone 3?
Core engine compartment
What is zone 2?
Intermediate compressor case compartment
How is zone 2 cooled?
By fan air from the upper part of the fan duct.
How are anti-icing systems controlled in flight?
By a switch on the flight deck.
How does air exit after heating the lip?
A grill on the nose cowl.
What is the temperature at the rear stages of the compressor?
350 °C to 400 °C
How is the compressor rotor cavity cooled?
Air from the intermediate compressor stage
What percentage of the primary airflow is directed inside the combustion liner?
20% - 30%
What percentage of the secondary airflow is directed around the combustors periphery?
70% - 80%
How does the secondary airflow provide cooling for the combustion liner?
It forms a cooling air blanket on both sides of the liner and centres the combustion flames so they do not contact the line.
How is the turbine disc cooled?
Using engine bleed air.
How are turbine Nozzle Guide Vanes (NGV) and turbine blades cooled?
Compressor air
How are accessory’s cooled?
Air ducted from cowling intakes or from a specific stage of the compressor.
What is used to seal engine bearing chambers?
Low pressure compressor bleed air.
What is pressurised air used to do when it comes to bearing chambers?
It acts on the air seals and oil seals and has an additional sealing effect that prevents oil from escaping.
How is air that enters the bearing compartments vented overboard?
Through the hollow N1 rotor shaft.
What does the external air system do?
Cools and ventilates the external areas between the cowlings and the engine cases.
When is the core compartment ventilated?
Only when the engine operates.
What is a bowed rotor?
When the engine bends due to different expansions between the upper and lower engine zones.
How is zone 1 cooled?
RAM air is used.
Where is zone 2 fan air exhausted?
At the lower end, back into the air stream.
