15.6 Turbines Flashcards

1
Q

What is the function of the turbine?

A

To absorb 60-70% of velocity energy and converts it to mechanical energy

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2
Q

What are the two types of turbine?

A

Radial flow
Axial flow

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3
Q

What are turbines used to drive?

A

Accessories
Compressors/ fans

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4
Q

What are the characteristics of radial flow turbines?

A

-always single stage
-only used on small engines such as the APU
-less efficient only able to accept small airflows

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5
Q

What are the characteristics of axial turbines?

A

-modern engines
-very high airflow

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6
Q

What does the gas pass through before hitting the turbines?

A

The nozzle guide vane

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7
Q

What is the meaning of an impulse turbine?

A

Rotation is achieved only by impact on the rotor blades

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8
Q

What are the three classifications of turbine blades?

A

Impulse configuration
Reaction configuration
Reaction impulse configuration

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9
Q

What is the meaning of reaction turbine?

A

-fixed nozzle guide vanes are designed to alter gas flow direction without altering pressure
-converging blade passage experience a reaction force resulting from expansion and acceleration of the gas

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10
Q

What is impulse reaction turbine?

A

-impulse and reaction occurring on the blade
-more common and higher efficiency
-impulse occurs at root remaining blade area is reaction
-AKA reaction

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11
Q

What are the two types of construction for aircraft blades?

A

Forged
Cast

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12
Q

What casting method provides superior qualities?

A

Single crystal

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13
Q

What is used to limit heat in turbine blades?

A

Airflow cooling
Ceramic coating

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14
Q

What does allowing exhaust gasses to be higher in heat allow for?

A

Increased efficiency in the engine

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15
Q

What is the disadvantage of shrouded turbine blades?

A

Limits turbine speeds

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16
Q

What is the function of the blade shroud?

A

Efficiency and vibration improvement

17
Q

How is the turbine wheel balanced?

A

Dynamically

18
Q

What is the turbine disc attached to?

A

The power transmission shaft

19
Q

When turbine blades are installed to the disc what does it become?

A

Turbine wheel

20
Q

How is the turbine disc protected from hot gasses?

A

Bleed air is directed onto it

21
Q

What must the turbine shaft be capable of carrying?

A

The highest torque loads

22
Q

What are the methods of attaching disc to shaft?

A

Welding
Bolting

23
Q

How is the turbine shaft typically attached to the compressor rotor hub?

A

Contoured slot
Welded
Riveted

24
Q

What must turbine blade fittings allow for?

A

Thermal expansion

25
Q

What is allowable in terms of turbine blade damage?

A

-No cracks
-dye penetrant inspection used
-slight damage can be allowed and blended

26
Q

What is blade creep?

A

Elongation through force and heat over long periods of time

27
Q

What are stress rupture cracks?

A

Minute hairline cracks on the leading and trailing edges