15.7 Exhaust

Question 1

What is the main task of the exhaust system on a turboprop engine?

Answer 1

Safely guides exhaust gases overboard

Question 3

What is the main task of the exhaust system on a jet engine?

Answer 3

To accelerate the airflow from the turbine to generate thrust

Question 4

What is the main task of the exhaust system on an APU?

Answer 4

To guide exhaust gases overboard

Question 5

How does the APU exhaust system decrease noise? Located where?

Answer 5

Using mufflers in the exhaust duct

Question 6

What are the 3 exhaust section components?

Answer 6

Exhaust cone, tailpipe and exhaust nozzle

Question 7

What does the exhaust cone do?

Answer 7

Collects exhaust gases from the turbine section and converts them into a solid flow of gas

Question 8

What happens to velocity and pressure in an exhaust cone?

Answer 8

Velocity decreases and pressure increases

Question 9

Is a tailpipe flexible? Why?

Answer 9

Semi flexible to avoid stress and warping

Question 10

What are the 2 functions of radial struts?

Answer 10

Support the inner cone in the exhaust duct and straighten swirling exhaust gases

Question 11

What degree do exhaust gases leave the turbine at?

Answer 11

45 degrees

Question 12

What are the 2 most common methods of protecting the fuselage structure?

Answer 12

Insulation blankets and shrouds

Question 13

What do insulation blankets do?

Answer 13

Reduce heat loss from exhaust system

Question 14

What are the 2 types of exhaust nozzle designs?

Answer 14

Convergent design and convergent divergent design

Question 15

When is a convergent t exhaust nozzle used?

Answer 15

For subsonic gas velocities

Question 16

When is a convergent divergent exhaust nozzle used?

Answer 16

Supersonic gas velocities

Question 17

What % of thrust do turboprops produce?

Answer 17

10-15%

Question 18

What % thrust do turbofans produce?

Answer 18

15-20%

Question 19

What 2 types of engines can turbofans be? Which one has 2 nozzles (1 for core airflow and 1 for fan airflow)?

Answer 19

Ducted or unducted. Unducted

Question 20

How can noise level be reduced?

Answer 20

By operating at lower power settings

Question 21

What 2 noise suppressors are in current use?

Answer 21

Corrugated perimeter type and multi tube type

Question 22

How do both noise suppressors work?

Answer 22

Break up the main jet exhaust stream into smaller jet streams

Question 23

Where are acoustic linings installed?

Answer 23

Between the engine and cowl

Question 24

What do acoustic linings do?

Answer 24

Convert acoustic energy into heat

Question 25

When is a variable area exhaust nozzle used?

Answer 25

When an augmented or afterburner is used

Question 26

What do thrust reversers do?

Answer 26

Produce braking force by deflecting the exhaust gas stream in the opposite direction

Question 27

What do thrust reversers only reverse on modern high bypass turbofan engines? Why?

Answer 27

Only reverse fan airflow as it produces the most thrust

Question 28

Can thrust reversers be used in flight?

Answer 28

No

Question 29

What are the 4 types of thrust reversers?

Answer 29

Clamshell type, bucket type, fan reverser and pivoting door reverser

Question 30

What 2 thrust reversers are used on older jet engines with low bypass ratios?

Answer 30

Clamshell type and bucket type

Question 31

How does a clamshell type thrust reverser work?

Answer 31

Rotates to block off airflow path and uncover cascade vanes

Question 32

How does the fan reverser type thrust reverser work?

Answer 32

The translating sleeves move rearwards once deployed to uncover cascade vanes. Blocker doors close off fan discharge airflow so it exits through cascade vanes

Question 33

How does the pivoting door reverser type thrust reverser work?

Answer 33

Closes off fan discharge airflow when deployed which deflects fan airflow forward

Question 34

When are thrust reversers most efficient?

Answer 34

At high speeds

Question 35

What can happen if thrust reversers are deployed at very low speeds?

Answer 35

Engine can ingest its own reversed airflow causing compressor stall and high EGT

Question 36

What do military aircraft use to change direction in flight? How?

Answer 36

Thrust vectoring. By moving exhaust nozzle to direct thrust into desired path.