M15.12 Air Systems Flashcards
What is the purpose of engine air distribution in internal combustion engines?
To provide cooling for the intense heat generated during fuel and air combustion.
Cooling is essential to maintain operational temperatures and prevent damage.
What is the ideal air/fuel ratio for gas turbine engines?
15:1
This ratio is necessary for optimal combustion but does not account for cooling needs.
What is the acceptable temperature range for gas turbine engines due to cooling air?
800 to 1150 °C
This range helps protect engine components from overheating.
What role does secondary air play in a gas turbine engine?
It cools the combustion chamber liners.
Secondary air induces a fast-moving film over the liner surfaces.
What is the most critical lubricating point in a gas turbine engine?
Exhaust turbine bearing
High temperatures make this point particularly sensitive.
How is secondary airflow for cooling provided in gas turbine engines?
By bleeding air from the early stages of the compressor.
This air cools various engine components.
What are the primary zones in turbine engines for cooling?
- Fan case compartment
- Intermediate compressor case compartment
- Core engine compartment
These zones help keep temperatures at acceptable levels.
What is Zone 1 in turbine engines?
The area around the fan case containing the accessory case and Electronic Engine Control (EEC).
This zone is crucial for managing engine accessories.
What is the function of the anti-ice system in turbine engines?
To prevent ice formation in the engine inlet duct and inlet guide vanes.
Icing can disrupt airflow and damage compressor blades.
What is the typical operating temperature for the rear stages of the compressor?
350 °C to 400 °C
High temperatures necessitate cooling measures.
How does the combustion chamber cooling system work?
It uses perforated inner liners and divides airflow into primary and secondary paths.
This design helps mix and cool combustion gases.
What percentage of incoming air is typically directed inside the combustion liner?
20% - 30%
The remaining air forms a cooling blanket around the combustor.
What is the primary method of cooling turbine components?
Using engine bleed air.
This method allows components to operate above the limits of their metal alloys.
What is the purpose of accessory cooling in gas turbine engines?
To cool engine accessories and electrical generators that produce heat.
Specific cooling systems are necessary for these components.
What is the function of bearing chamber seals in gas turbine engines?
To prevent oil from escaping out of the bearing chamber.
LP compressor bleed air is used for this sealing effect.
What systems can engine bleed air be used for?
- Cabin pressurisation
- Heating and cooling
- De-icing and anti-icing equipment
- Pneumatic starting of engines
- Auxiliary Drive Units (ADU)
Engine bleed air is versatile and supports various aircraft systems.
What does the external cooling system do in gas turbine engines?
Cools and ventilates the external areas between the cowlings and engine cases.
It prevents the accumulation of flammable vapours.
What happens to the engine after shutdown due to thermal expansion?
The engine can bend, leading to a condition known as a bowed rotor.
This occurs because of different expansions between engine zones.
