15.7 Exhaust Flashcards
What is the function of the exhaust on jet engines?
To accelerate airflow efficiently to generate thrust.
What is the function of the exhausts on turboprop engines?
To safely guide exhaust gasses overboard.
What is the function of the exhaust on the APU?
To guide gasses overboard as gas energy will be absorbed by the turbines.
What does the APU have to reduce the noise of exhaust gasses?
Mufflers
What are the features of the exhaust?
Exhaust cone.
Tailpipe.
Exhaust nozzle.
What does the exhaust cone create?
A diverging passage between the outer duct and inner cone.
The exhaust cone is made of an inner shell, outer shell and 3 to 4 radial hollow struts. What does the radial hollow struts do?
Aid the struts in supporting inner cone from the outer duct.
What is another purpose of radial struts?
They also straighten swirling exhaust gasses.
Why is there a small hole located in the exit tip of the exhaust core?
Allows cooling air to be circulated.
What allows for movement in the installation, maintenance and thermal expansion of the tailpipe?
Bellow arrangement.
What are the 2 methods of insulation in the tailpipe?
Blankets and shrouds.
What are the 2 exhaust nozzle designs and when are they used?
Converging = subsonic.
Converging - diverging = supersonic.
What is the effect does a converging nozzle increasing velocity have ?
It increases thrust by 15-20%.
What amount of thrust does a turboprop exhaust nozzle provide?
Small amounts between 10-15%
When is a variable exhaust nozzle used?
When an augmented or afterburner is used at supersonic speeds.
How does a convergent nozzle reduce turbulence?
The exhaust nozzle and plug form a divergent duct before air flows through the convergent component.
Why is converging - diverging nozzle used at supersonic speeds?
Due to a resulting higher pressure across the engine exhaust nozzle.
What are common noise suppressors?
Integral or engine exhaust nozzle.
What are the 3 sources of noise in an engine?
Air intake.
Vibration of engine housing.
Engine exhaust (loudest).
What size engine is quieter?
A larger engine with greater mass flow of air.
What are the 2 types of noise suppressors?
Perimeter type.
Multi tube type.
What is in the engine nacelle for noise suppression?
A noise absorbing lining material which converts acoustic energy to heat.
What does the noise absorbing lining consist of?
Porous skin.
What is the purpose of thrust reversers?
To bring the aircraft to a rest.
