15.7 Exhaust

Question 1

What is the purpose of the exhaust system on jet aircraft?

Answer 1

Creating airflow to generate thrust

Question 2

What is the purpose of the exhaust on turboprop engines?

Answer 2

To safely guide gas overboard

Question 3

What is one other function of an APU exhaust?

Answer 3

A muffler

Question 4

What are the main components of an exhaust?

Answer 4

Exhaust cone
Tail pipe
Exhaust nozzle

Question 5

What is the function of the exhaust cone?

Answer 5

Gradually converts gases from the turbine section into a solid flow

Question 6

What is the purpose of the radial struts?

Answer 6

-support the inner cone
-straighten swirling exhaust gases

Question 7

What is the purpose of the hole in the tip of the exhaust cone?

Answer 7

allows cooling air to be circulated to the interior of the cone and the turbine wheel

Question 8

Why is the tailpipe constructed to be semi flexible/ bellows arrangement?

Answer 8

-for movement in insulation
-maintenance
-to allow for thermal expansion

Question 9

What are the two exhaust nozzle designs?

Answer 9

Converging (subsonic gas velocities)
Convergent divergent (supersonic gas velocities)

Question 10

What increase does a converging duct give in thrust for a subsonic aircraft?

Answer 10

-15-20%

Question 11

What is the application/ function of a variable area nozzle?

Answer 11

When an aircraft has an augmenter or afterburner
When the aircraft is subsonic it converges at supersonic it diverges

Question 12

What is the structure and design of the convergent nozzle?

Answer 12

At first the gas enters a divergent stage and then a convergent duct increasing velocity

Question 13

What is the function and design of the convergent divergent exhaust nozzles ?

Answer 13

When gas velocity may exceed Mach 1
Convergent section accelerates gas divergent further increases velocity

Question 14

What are the three sources of noise in the operation of a gas turbine engine?

Answer 14

-engine air intake
-housing vibration
-exhaust

Question 15

What causes exhaust noise?

Answer 15

High amounts of turbulent high temp air mixing with the atmosphere

Question 16

What does the porous skin/ noise absorbing lining convert acoustic energy into?

Answer 16

Heat

Question 17

How do thrust reverse produce a braking force?

Answer 17

Deflecting gases in the opposing direction

Question 18

How do modern turbofan engines differ in thrust reversing?

Answer 18

Only fan air is deflected

Question 19

Where is the deflection mechanism stored when not operational?

Answer 19

Flush

Question 20

Where is the clamshell deployed vs the bucket type thrust reverser?

Answer 20

Clam= before exhaust nozzle
Bucket = after exhaust nozzle

Question 21

How is the clamshell reverser usually operated?

Answer 21

Pneumatically

Question 22

How does a clamshell direct air?

Answer 22

Cascade vanes

Question 23

What operates bucket type reversers?

Answer 23

Hydraulic actuators

Question 24

What is a fan reverser used on?

Answer 24

Turbo fan engines with high bypass ratios

Question 25

What type is a fan reverser?

Answer 25

Cascade type thrust reverser with a translating sleeve

Question 26

How is a pivoting thrust reverser door actuated?

Answer 26

Hydraulically

Question 27

What engine would a pivot door be used on?

Answer 27

Turbo fan engines

Question 28

What are the disadvantages of the thrust reverser?

Answer 28

-can cause a compressor stall
-high temperature air can be re-ingested by the engine
-dirty can be swirled into the engine inlet

Question 29

How is dirt ingestion limited into the engine when thrust reversers are activated?

Answer 29

The reversers are matched to engine position

Question 30

How are 4 engine aircraft thrust reversers altered so that ingestion is accounted for?

Answer 30

The are directed to ensure reversal is not directed in a way that causes dirt ingestion by the adjacent engines

Question 31

What aircraft is it used on and what principle does thrust vectoring operate on?

Answer 31

Military aircraft
The thrust is directed to aid manoeuvres by altering the nozzle at the exhaust