15.7 Flashcards
(44 cards)
What does exhaust do in a jet engine
Accelerate airflow from the turbine to efficiently generate thrust
How does APU reduce noise
Mufflers
What does the exhaust do in a turboprop engine
Guide gases overboard
Why does APU exhaust gases go overboard
All gas energy is absorbed by the turbine
Components of exhaust
Cone
Tailpipe
Exhaust nozzle
What does exhaust cone do
Collects exhaust gases from turbine section and gradually confers them into solid flow of gases
Exhaust cone assembly
Outer shell/ duct
Under cone
3/4 radial hollow struts/fins
What do radial struts do
Support inner cone
Straighten swirling exhaust gases that would of came out at a 45 degree angle
What’s the purpose for the hole at the tip of the cone
Allows cooling air to be circulated from the aft end of the cone
How is the tail pipe constructed
So it’s semi flexible in a bellows arrangement
What’s the need for a bellows arrangement
Allows movement in instillation , maintenance and thermal expansion
Two most common methods of protecting the fuselage structure
Blankets and shrouds
What’s the two types of exhaust nozzle designs
Converging for Subsonic gas velocities
Converging-diverging for supersonic gas velocities
What increases exhaust gases velocity
Converging nozzle
What % does thrust increase by increasing velocity
15-20%
How much thrust does a turboprop exhaust nozzle give you
10-15%
Why is the fixed type nozzle simplest
No moving parts
2 types of exhaust nozzle
Fixed or variable
When is a variable nozzle used
Augmenter or after burner is used
After the turbine what duct is there
Divergent to reduce turbulence in the airflow
When exhaust gases exceed Mach 1 what nozzle is would you use
Convergent - divergent
Advantage of convergent divergent nozzle
At high Mach numbers because of the resulting higher pressure ratio across the engine exhaust nozzle
Where does engine noise come from
Fan
Compressor
Air discharge from core of engine
Sources of noise
Air intake
Vibration
Engine exhaust
