M15.7 Exhaust Flashcards
What is the main task of the exhaust system in a jet engine?
To accelerate the airflow coming from the turbine to efficiently generate thrust.
What is the main task of the exhaust system in a turboprop engine?
To safely guide the exhaust gases overboard.
What does the exhaust system of an Auxiliary Power Unit (APU) do?
Guides exhaust gases overboard and reduces noise using mufflers.
What are the main components of the exhaust section in a gas turbine engine?
- Exhaust cone
- Tailpipe
- Exhaust nozzle
What is the function of the exhaust cone?
Collects exhaust gases and converts them into a solid flow, slightly decreasing velocity and increasing pressure.
What materials are typically used in the construction of the exhaust cone assembly?
Stainless steel for the outer shell or duct.
What is the purpose of the radial struts in the exhaust cone assembly?
Support the inner cone and straighten the swirling exhaust gases.
What is the function of the tailpipe?
Discharges exhaust gases and is usually semi-flexible to accommodate movement.
What is the construction of an insulation blanket in the exhaust section?
Several layers of aluminium foil separated by fibreglass.
What are the two types of exhaust nozzle designs?
- Converging design for subsonic gas velocities
- Converging-diverging design for supersonic gas velocities
What is the primary role of the converging nozzle in turbine engines?
Increase the velocity of exhaust gases before discharge.
What percentage of thrust do turboprop exhaust nozzles provide?
10-15%.
What is the difference between fixed and variable exhaust nozzles?
Fixed nozzles have no moving parts, while variable nozzles adjust their open area based on engine conditions.
What is the purpose of a convergent-divergent nozzle?
To gain more thrust at high Mach numbers by handling gases that exceed sonic velocity.
What causes the high-frequency noise in gas turbine engine exhaust?
High-velocity jet stream turbulence mixing with the atmosphere.
What are common types of noise suppressors used in gas turbine engines?
- Corrugated perimeter type
- Multi-tube type
What is the effect of thrust reversers on aircraft braking?
They deflect the exhaust gas stream in the opposite direction, providing additional braking force.
Why can thrust reversers only be used on the ground?
Their operation in flight can cause dangerous aerodynamic changes.
What type of thrust reverser is typically found on older jet engines with a low bypass ratio?
Clamshell door-type thrust reverser.
What is the function of the bucket door type thrust reverser?
To block normal flow and uncover exit ducts for reverse thrust.
What is unique about fan reversers in high bypass turbofan engines?
Only the cold fan air is deflected to provide reverse thrust.
What are the disadvantages of thrust reverser operation?
- Engine compressor stall
- Ingestion of reversed airflow causing stalls
- Whirling up dirt and dust
How can reversed airflow be matched to minimize disadvantages in thrust reversers?
By directing airflow at optimal angles to prevent ingestion by the engines.
What is the importance of the angle of the reverse stream on a four-engine aircraft?
The angle is crucial to prevent reversed airflow from being ingested by the outer engines.
How do thrust reversers on twin-engine aircraft differ from those on four-engine aircraft?
On four-engine aircraft, reversed airflow can affect neighboring engines, making airflow direction more critical.
What can be arranged to match the reversed airflow in thrust reversers?
The correct arrangement of the cascade vanes in the thrust reverser cowlings.
What happens if the distance between engines on a four-engine aircraft is large enough?
The reversed airflow does not affect the neighboring engine.
What is one advantage of having all engines on an aircraft with the same cowlings?
Fewer spare parts are needed.
What is the role of the thrust reverser in an aircraft?
It serves as an additional braking support.
Can an aircraft be released for service with a defective thrust reverser system?
Yes, it can be released for service if the system is correctly deactivated.
What is thrust vectoring used for in military aircraft?
It is used for maneuvering in flight to change direction.
How is thrust vectoring generally accomplished?
By relocating the direction of the exhaust nozzle to direct thrust.
Fill in the blank: Thrust vectoring allows military aircraft to change _______.
[direction]
True or False: A defective thrust reverser system can deploy unintentionally if not deactivated correctly.
True
