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M15 > 15.7 Exhaust > Flashcards

15.7 Exhaust Flashcards

1
Q

What is the function of the exhaust on jet engines?

A

To accelerate airflow efficiently to generate thrust.

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2
Q

What is the function of the exhausts on turboprop engines?

A

To safely guide exhaust gasses overboard.

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3
Q

What is the function of the exhaust on the APU?

A

To guide gasses overboard as gas energy will be absorbed by the turbines.

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4
Q

What does the APU have to reduce the noise of exhaust gasses?

A

Mufflers

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5
Q

What are the features of the exhaust?

A

Exhaust cone.
Tailpipe.
Exhaust nozzle.

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6
Q

What does the exhaust cone create?

A

A diverging passage between the outer duct and inner cone.

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7
Q

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?

A

Aid the struts in supporting inner cone from the outer duct.

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8
Q

What is another purpose of radial struts?

A

They also straighten swirling exhaust gasses.

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9
Q

Why is there a small hole located in the exit tip of the exhaust core?

A

Allows cooling air to be circulated.

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10
Q

What allows for movement in the installation, maintenance and thermal expansion of the tailpipe?

A

Bellow arrangement.

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11
Q

What are the 2 methods of insulation in the tailpipe?

A

Blankets and shrouds.

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12
Q

What are the 2 exhaust nozzle designs and when are they used?

A

Converging = subsonic.
Converging - diverging = supersonic.

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13
Q

What is the effect does a converging nozzle increasing velocity have ?

A

It increases thrust by 15-20%.

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14
Q

What amount of thrust does a turboprop exhaust nozzle provide?

A

Small amounts between 10-15%

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15
Q

When is a variable exhaust nozzle used?

A

When an augmented or afterburner is used at supersonic speeds.

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16
Q

How does a convergent nozzle reduce turbulence?

A

The exhaust nozzle and plug form a divergent duct before air flows through the convergent component.

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17
Q

Why is converging - diverging nozzle used at supersonic speeds?

A

Due to a resulting higher pressure across the engine exhaust nozzle.

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18
Q

What are common noise suppressors?

A

Integral or engine exhaust nozzle.

19
Q

What are the 3 sources of noise in an engine?

A

Air intake.
Vibration of engine housing.
Engine exhaust (loudest).

20
Q

What size engine is quieter?

A

A larger engine with greater mass flow of air.

21
Q

What are the 2 types of noise suppressors?

A

Perimeter type.
Multi tube type.

22
Q

What is in the engine nacelle for noise suppression?

A

A noise absorbing lining material which converts acoustic energy to heat.

23
Q

What does the noise absorbing lining consist of?

A

Porous skin.

24
Q

What is the purpose of thrust reversers?

A

To bring the aircraft to a rest.

25
Q

What effect do thrust reversers have on icy or snow covered runways?

A

They reduce the braking distance.

26
Q

What air do modern turbofan engines reverse?

A

Only fan airflow.

27
Q

Where can thrust reversers be used?

A

Only on the ground.

28
Q

What engines have a common exhaust nozzle for hot and cold air?

A

Turbofan engines with a low bypass ratio.

29
Q

Where is clamshell door thrust reverser found?

A

In front of exhaust nozzles.

30
Q

Where is the bucket door type thrust reverser found?

A

At the exhaust nozzle.

31
Q

The clamshell door and bucket door thrust reversers are used on what engines?

A

Older jet engines with a low bypass ratio.

32
Q

How are clamshell door thrust reversers operated?

A

Pneumatically by bleed air from the compressor.

33
Q

What is only found on the clamshell door thrust reverser to deflect air forwards?

A

Cascade vanes.

34
Q

How is the bucket door thrust reverser operated?

A

Hydraulically.

35
Q

On what engines are fan thrust reversers used?

A

On engines with a high bypass ratio.

36
Q

What is the most common fan thrust reversers?

A

A cascade type with translating sleeves.

37
Q

How are fan thrust reversers operated?

A

Pneumatically by drive motors or hydraulically by actuators.

38
Q

What is another type of fan thrust reverser?

A

Pivoting door thrust reverser.

39
Q

How is a pivoting door thrust reverser activated?

A

Hydraulically.

40
Q

What negative effects can thrust reverser operation have ?

A

Engine compressor can stall.
At low speeds they can inject its own reversed air.
FOD

41
Q

How are the negatives of thrust reverser operation minimised?

A

The reverser airflow is matched to engine position.

42
Q

What must be considered when operating thrust reversers on 4 engine aircraft?

A

Reversed airflow from the inner engine can be injected by the outer engine, if the distance between the engines is too small.

43
Q

When is thrust vectoring used?

A

On military aircraft for manoeuvring.

M15 (18 decks)

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