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Millwright 4th Year > Gas Turbines > Flashcards

Gas Turbines Flashcards

1
Q

What does the efficiency of a gas turbine depend on?

A

The temperature to which the air can be raised

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2
Q

What type of engine is a gas turbine?

A

Internal combustion, constant flow

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3
Q

What are the different shafts in a gas turbine?

A

Single shaft

Split shaft

Twin spool shaft

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4
Q

What are the 2 main sections of a gas turbine?

A

Gas generation section

And

Power section

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5
Q

What are the 3 main components of a gas turbine?

A

Compressor

Combustion chamber

Turbine

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6
Q

What are the cons of an open cycle turbine?

A

It has no heat exchanger or regenerator, therefore it has no way to capture the heat from the exhaust gases

This makes the turbine much less efficient

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7
Q

What is a semi-closed cycle turbine?

A

A turbine that either has a heat exchanger or regenerator attached to it in order to use the waste exhaust heat to assist in heating the expansion of gases before the turbine combustion area.

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8
Q

What is convergence?

A

Gases coming together in a smaller area

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9
Q

What is divergence?

A

Gases moving apart into a larger area

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10
Q

How happens to the pressure and velocity inside the turbine compressor?

A

The pressure will increase and the velocity will decrease

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11
Q

Where is the highest pressure in a gas turbine?

A

The diffuser

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12
Q

What happens at the first set of nozzles of the gas turbine section?

A

Pressure is reduced and the velocity is increased

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13
Q

What are the steps/events of a gas turbine?

A

Intake

Compression

Ignition (also can be in the power section)

Power

Exhaust

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14
Q

Approximately how much of the power developed by a gas turbine is used by the compressor and other accessories?

A

75%

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15
Q

What happens if the pressure in the combustion chamber becomes higher then the pressure in the diffuser?

A

The gases can back up and move into the compressor which can cause surging and serious damage to the turbine.

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16
Q

Do you need to filter the air before it enters a gas turbine?

A

Yes it must have high flow with low restrictions, any restriction to flow can cause surging and catastrophic failure.

17
Q

What are the 2 types of compressors in a gas turbine?

A

Radial flow (centrifugal)

Axial flow

These are both dynamic compressors

18
Q

What are the 3 main parts of a radial flow compressor?

A

Impeller

Diffuser

Compression manifold

19
Q

What are the 2 main parts of an axial flow compressor?

A

Rotor with blades

Stator with blades (stationary)

20
Q

What accessories controls the variability pitch stator blade system?

A

The fuel control system

21
Q

What are variable pitch stator blades?

A

They are blades that can adjust there pitch by a linkage attached to each stator blade.

They help the turbine engine maintain maximum compressor efficiency over the operating speed of the engine

22
Q

What are the main parts of a combustion chamber in a gas turbine?

A

The combustion chamber housing (combustion) is the outside housing.

The combustion chamber liner (flame tubes) is the inside of the housing.

The fuel nozzle (fuel injector, atomizer, vaporizer) injects the fuel.

The igniter ignites the fuel air mixture.

23
Q

What are the 3 zones of a combustion chamber?

A

The primary zone
- First part of the combustion chamber liner where fuel injection and ignition begins

The intermediate zone
- Combustion continues and begins to mix with secondary air

The dilution zone
- combustion should be complete, but secondary air is mixed with the burnt gases

24
Q

Where is the hottest place in a gas turbine?

A

The combustor

25
Q

What are the different styles of combustion chambers?

A

Can type chambers

Annular type chambers

Can-annular chamber

26
Q

What type of compressor is normally used with a can type combustion chamber?

A

Most often used with centrifugal compressors

27
Q

What type of compressor is normally used with an annular type combustion chamber?

A

Axial flow compressors

28
Q

What type of compressor is normally used with a can-annular combustion chamber?

A

Axial flow compressors

29
Q

When is the turbine igniter used?

A

Only during start up

After start up the continuous flame ignites the fuel.

30
Q

What are the 2 categories of fuel used?

A

Liquid fuels

Gaseous fuels

31
Q

How are the stationary nozzle vanes cooled on a gas turbine?

A

They have small holes through out allowing for secondary air to be forced through them for cooling

32
Q

What kind of seals are used on on gas turbines?

A

Labyrinth seals

33
Q

Do gas turbines need large foundations?

A

No they do not require massive foundations as other prime movers do

34
Q

What is the purpose of a gas turbine wash system?

A

Used to remove the buildup on the compressor blades

Millwright 4th Year (15 decks)

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