15.12 Air Systems Flashcards
(45 cards)
A large vloume of air cools the hot sections of the engine, to what acceptable temperature range?
800 - 1150 degrees C
What ‘type’ of air is used to cool the combustion chamber liners?
Secondary air.
What are considered the primary zones of the engine? (3)
- Fan case compartment.
- Intermediate compressor case compartment.
- Core engine compartment.
What is included in the Zone 1 area?
The area around the fan case, containing the accessory case and EEC.
How is the zone 1 area vented and cooled?
Ram air enters through and inlet tube in the nose cowl. It exits through a vented panel in the RHS engine fan cowling.
What does the Zone 1 area have to protect against overpressure?
Pressure relief door.
What is included in the Zone 2 area?
Fuel and oil lines.
How is the zone 2 area cooled?
Cooled by fan air from upper fan duct, and exhausted out at the lower end to rejoin the fan-air stream.
What does the zone 3 area cover?
The area around the HP compressor to turbine cases. Also contains fuel/oil lines and other accessories.
How is the Zone 3 area cooled?
Air enters the from the outlet of the pre-cooler, and exits through the aft edge of the thrust reverser inner wall and turbine exhaust sleeve.
At what temperature can ice form on the inlet?
Any temperature up to 5 degrees C.
Is the anti-icing system normally controlled automatically or manually?
Normally controlled automatically.
How does the anti-ice system operate automatically?
The system activates when icing condtions are detected.
The system opens a bleed valve, that bleeds hot air from the compressor.
What areas of the engine are fed with hot bleed air for anti-icing? (3)
- The inlet leading edge.
- Nose dome.
- Inlet guide vanes.
Where does the bleed air that’s used to heat the inlet, exit the aircraft?
Via grills in the nose cowling.
What is the approximate temperature of the aft section of the compressor?
350-450 degrees C.
How is the aft stage of the compressor cooled?
Rotor cavity is provided with air from the intermediate compressor stage, which is a bit cooler.
What type of airflow cools the combustion chamber inner liner?
The secondary airflow.
What 2 things does the secondary airflow do to help keep the inner liner cool?
- Forms a cooling air blanket on both sides of the liner, acting as a thermal barrier.
- Removes heat directly.
What feature of the combustion chamber’s outer-casing inner liner, also assists with cooling?
The inner liner is perforated.
How does the secondary airflow assist with flame propagation?
It keeps the flame straight, preventing it from contacting the inner liner
What is the main benefit of using cooling systems on turbines?
It allows the turbine to operate at 300-400 degrees C above the limits of their metal alloys.
What’s the most common method used to cool the turbine section?
Bleed air.
What is usually at a higher temperature on the turbine disc, the rim of the disk or the centre of the disk?
The rim of the disc.
