Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

M15 > M15.07 Exhuast > Flashcards

M15.07 Exhuast Flashcards

1
Q

What is the main function of the exhaust system?

A

Accelerate the airflow coming from the turbine to make thrust

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

On a jet engine the exhaust system releases gas too?

A

The atmosphere

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How does the APU reduce the noise of the exhaust?

A

By using mufflers in the exhaust duct

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

On jet engines the exhaust system has a tube, what it’s is called?

A

Exhaust duct or tail pipe

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the purpose of the exhaust nozzle at the aft end of exhaust duct??

A

Accelerates the exhaust gases which leave the engine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What does the exhaust cone prevent?

A

. Prevent reverse flow
. Excessive turbulence
. Guides the discharge flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Modern turbofan engines have two exhaust steams, why?

A

. Hot gas flows via primary nozzle
. Cold fan air via secondary nozzle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

The most common exhaust nozzle on long range aircraft is??

A

. Combined exhaust nozzle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How does the combined exhaust nozzle work??

A

. Mixes hot and cold gas flow to reduce velocity of exhaust gases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What’s the advantage of combined exhaust nozzle??

A

. Gives higher propulsion efficiency

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What’s a disadvantage of the combined exhaust nozzles??

A

. Increases weight if the engine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

To achieve optimum thrust what must happen?

A

The exhaust gases must expand completely in an exhaust nozzle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

By having the gases completely expand in the exhaust nozzle, what does this ensure?

A

. Creates a laminar vortex free and axially oriented exhaust gas flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

The exhaust airflow can happen due too?

A

The pressure ratio between the turbine discharge and ambient pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the maximum airflow pressure ratio on a convergent exhaust nozzle?

A

2:1
(At high pressure ratios, do not get a higher airflow as it will get chocked)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what nozzle is used for pressure ratios more than 2:1??

A

Convergent - divergent nozzles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What type of aircraft are convergent - divergent nozzles used on?

A

Aircraft that fly faster than speed of sound

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What type of exhaust nozzle do modern turbofan engines have??

A

Convergent exhaust nozzles with wide exhaust nozzles that don’t choke

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What unit is used to express noise??

A

. Effective perceived noise deCiBel (EPNdB)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How can internal noise be minimised in the exhaust nozzle?

A

By reducing airflow distribution which causes turbulence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What provides very powerful noise suppression?

A

Acoustic linings which turns sound energy into heat energy by the sound waves being reflected

22
Q

What is a disadvantage if acoustic linings?

A

Increases engine weight

23
Q

What is the main external noise source?

A

exhaust jet

24
Q

What are the two methods an external jet noise be reduced?

A

. Mixing it with the atmosphere in a short mixing region
. Additional mixing of ambient air to exhaust gas before going to nozzle

25
Q

What is the main function of thrust reversers??

A

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

26
Q

What angle deflection would be ideal?

A

180 degrees

27
Q

What is the actual angle deflection??

A

. 45-60 degrees deflection

28
Q

On modern turbofan engines with a high bypass ratio, what air is used for thrust reversers?

A

. Only fan airflow because it creates the most amount of thrust

29
Q

Can thrust reversers be used on the ground or during flight?

A

On the ground only

30
Q

How is the clamshell door ( on old aircraft) operated?

A

Pneumatically by bleed air from HP compressor

31
Q

How is the bucket door ( in older aircraft) reverser operated?

A

. Hydraulically operated

32
Q

On turbo fan engines with a high bypass ratio, what air is used for thrust reversers??

A

Only the cold fan air is deflected give reverse thrust

33
Q

What is the most common type of fan reversers??

A

Cascade type reversers with translating sleeves

34
Q

What is another type of thrust reversers?

A

. Pivoting door - hydraulically activated

35
Q

What are the main disadvantages of thrust reversers and their operation?

A

. Has problems operating at low speeds ( can ingest their own reverse thrust)
. Can cause stall due to disturbed airflow
. Whirls up a lot of dust and dirt from runway causing FOD

36
Q

How can you minimise the disadvantages of reverse operation??

A

. Airflow need to be matched to engine position angle.

37
Q

On four engine aircraft’s, reversers stream is important as it may get ingested by the outer engines, how to prevent?

A

. Each airflow directs the airflow to the safest possible direction

38
Q

If there is a faulty reverse thruster, what can still happen?

A

. The aircraft can be released for service, but all of the have to be deactivated as only an extra breaking

39
Q

What are the 3 main subsystems on a thrust reverser?

A

. The control system
. The reverser actuation system
. The airflow deflection system

40
Q

What does the control system do?

A

Activates thrust reversers and increases power fit reverse thrust

41
Q

What does the reverser actuation system do?

A

Either pnumatically or hydraulically component
Moves the airflow deflection mechanism by signals from the reverser control system

42
Q

What does the airflow deflection system do?

A

Directs airflow in the optimum direction for safe reverse thrust

43
Q

What is the purpose of the thrust reverser interlock system??

A

. Ensures engine power can only be increased after the reverser is fully deployed

44
Q

What type of hydraulic causation systems used on?

A

. On reversers with large blocker doors

45
Q

What make’s hydraulics reverser systems more complicated?

A

Because they need to be synchronised

46
Q

Pneumatic reverser actuation systems are only used in??

A

Cascade toe thrust reversers with translating sleeves
(Usually have air motors from bleed air)

47
Q

All thrust reversers actuation systems must have what to ensure safety??

A

. A locking system to ensure the reverser is kept safe in towed position and cannot move unintentionally

48
Q

Cascade segments all look different, yet they all deflect airflow fwd but??

A

. Some deflect airflow 45 degrees upward
. Some deflect airflow 45 degrees downwards
. Some deflect airflow 90 degrees straight out of fan air duct
. Some segments are totally blocked

49
Q

What does the reverse unlock message mean??

A

Indicates the reverser is not in a safe stowed position or is in movement

50
Q

What colour is the reverse unlock message in??

A

Amber

51
Q

What does a green reverse light indicate??

A

. Reverser is fully deployed
. Throttle interlock is realised so engine power can be increased for reverse thrust

M15 (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions