15.07 Exhaust. Flashcards
(13 cards)
How does the purpose of the exhaust vary between different types of engines.
Turboprop = gasses overboard.
Jet engine = accelerate airflow = more thrust.
APU = muffles sound.
Exhaust cone.
Has outer shell, inner cone, radial hollow struts.
- the radial struts support the inner cone and straighten the exhaust gasses.
Exhaust cone collects gasses and converts them into a solid flow, the velocity of the gasses decreases and pressure increases - diverging.
Convergent exhaust nozzle
Design for subsonic gas velocities.
First part is divergent to reduce turbulent air.
Converging-diverging exhaust nozzles.
Designed for supersonic gas velocities.
Turbo prop exhaust nozzle
Produces 10-15% of thrust.
Variable exhaust nozzles
For when an augmenter or afterburner is used.
Engine noise reduction
Noise is caused by violent, turbulent mixing of hot and cold air
Noise suppressors:
- perimeter type
- multi-tube type
Have acoustic liners , pourus skin turns noise to heat.
Clamshell type thrust reversers
Installed o older jet a/c with a low bypass ratio.
Pneumatically operated with bleed air from HP stage
Front of the exhaust nozzle.
Have cascade vanes.
Bucket type thrust reversers
Found on older jet engines with low bypass ratio.
Hydraulically operated.
Fan reversers
Turbofan w/ high bypass
Cascade-type thrust reversers.
Pneumatic or hydraulically operated.
Has cascade vanes, blocker doors and translating sleeves.
Pivoting door reversers
Used on modern turbofan engines
Hydraulically actuated
Flush with engine cowling
When deployed they close off the fan discharge airflow.
Effects of thrust reversers operation
Compressor can stall
Reverse flow whirls up lots of dirt and dust on the runway
Reversed airflow needs to be matched to the engine position.
Thrust vectoring
Used on military a/c for manouvering.
Re-directs the exhaust nozzle.
