15.7 Exhaust Flashcards
What is the purpose of the exhaust system on jet aircraft?
Creating airflow to generate thrust
What is the purpose of the exhaust on turboprop engines?
To safely guide gas overboard
What is one other function of an APU exhaust?
A muffler
What are the main components of an exhaust?
Exhaust cone
Tail pipe
Exhaust nozzle
What is the function of the exhaust cone?
Gradually converts gases from the turbine section into a solid flow
What is the purpose of the radial struts?
-support the inner cone
-straighten swirling exhaust gases
What is the purpose of the hole in the tip of the exhaust cone?
allows cooling air to be circulated to the interior of the cone and the turbine wheel
Why is the tailpipe constructed to be semi flexible/ bellows arrangement?
-for movement in insulation
-maintenance
-to allow for thermal expansion
What are the two exhaust nozzle designs?
Converging (subsonic gas velocities)
Convergent divergent (supersonic gas velocities)
What increase does a converging duct give in thrust for a subsonic aircraft?
-15-20%
What is the application/ function of a variable area nozzle?
When an aircraft has an augmenter or afterburner
When the aircraft is subsonic it converges at supersonic it diverges
What is the structure and design of the convergent nozzle?
At first the gas enters a divergent stage and then a convergent duct increasing velocity
What is the function and design of the convergent divergent exhaust nozzles ?
When gas velocity may exceed Mach 1
Convergent section accelerates gas divergent further increases velocity
What are the three sources of noise in the operation of a gas turbine engine?
-engine air intake
-housing vibration
-exhaust
What causes exhaust noise?
High amounts of turbulent high temp air mixing with the atmosphere
What does the porous skin/ noise absorbing lining convert acoustic energy into?
Heat
How do thrust reverse produce a braking force?
Deflecting gases in the opposing direction
How do modern turbofan engines differ in thrust reversing?
Only fan air is deflected
Where is the deflection mechanism stored when not operational?
Flush
Where is the clamshell deployed vs the bucket type thrust reverser?
Clam= before exhaust nozzle
Bucket = after exhaust nozzle
How is the clamshell reverser usually operated?
Pneumatically
How does a clamshell direct air?
Cascade vanes
What operates bucket type reversers?
Hydraulic actuators
What is a fan reverser used on?
Turbo fan engines with high bypass ratios
