Chapter 71- Gas Turbines Flashcards

1
Q

The three things a gas turbine is considered

A

*constant flow rotors engine * heat engine * prime mover

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2
Q

List two facts about early gas turbines

A

* handicapped by lack of metal that withstand high temps * air compressor and turbine had very love efficiency

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3
Q

____ of the power is used for the air compression on a gas turbine

A

2/3

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4
Q

Output power or ____ depends in _____

A

Power rating Mass of hot gas

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5
Q

Output increases in a gas turbine when using

A

Air of maximum density

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6
Q

An example of aero turbine

A

Jet engine

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7
Q

An open system gas turbine

A

Air drawn from atmosphere and returned

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8
Q

Air and hot gas are _____ from compressor to turbine

A

Ducted

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9
Q

Turbine has to be brought up to ___% speed before the fuel is turned on

A

20-30

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10
Q

The two types of gas turbine

A

Aero derivative Land based

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11
Q

A simple turbine system has no (3)

A

*heat exchanger *regenerator *intercooler

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12
Q

A single shaft gas turbine

A

Has only one shaft. Compressor and turbine are coupled together

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13
Q

What is the majority of gas turbines in industry

A

Simple Open single shaft

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14
Q

Five advantages of the gas turbine

A

*higher power to weight ratio *low installed coat *low maintenance and operating cost *minimum cooling water *rapid start up and loading

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15
Q

List four disadvantages of gas turbines

A

*low mechanical and thermal efficiency *high noise level *limited types of fuel *NOx emissions

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16
Q

Compared to a steam plant and gas turbine is

A

Smaller and lighter

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17
Q

Absence of reciprocating motion and min wear of moving parts results in

A

Low maintenance and operating cost

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18
Q

Gas turbines require Minimal cooling water and is ideal for

A

Areas where water is scarce

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19
Q

What type of fuel does a turbine use

A

Clean liquid or gaseous fuels

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20
Q

What’s the purpose of regenerators

A

Improve efficiency by recovering heat

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21
Q

Regenerators are more efficient with

A

Cold air

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22
Q

Heat recovered from exhaust gas

A

Reduces fuel quality

23
Q

What are two main benefits from combining a gas turbine with a steam plant

A

*plant economy improves * reduction in boiler size

24
Q

Gas turbines combined with steam plants are referred to as

A

Combine cycles

25
Q

What are the two things that are important for an operator to understand about gas turbines

A

How the ambient temp and atmospheric pressure effects it

26
Q

Atmospheric pressure affects _______ in a gas turbine

A

Internal combustion engine and boiler performance

27
Q

Air temperature changes

A

Air density

28
Q

Define manual start up

A

Operator starts all auxiliary systems and takes gas turbine to minimum governor setting

29
Q

Define semi automatic start ups

A

Only auxiliary system and automatic control takes gas turbine to minimum governor setting

30
Q

Define automatic starting methods

A

Operator pushes button

31
Q

What should you do if the engine of a turbine doesn’t start up within 90 seconds

A

Abort start up

32
Q

If 50% rpm is not reached in 60 seconds what should you do

A

Abort cranking

33
Q

Large turbines are fitted with

A

Serval governors

34
Q

The over speed trip device will

A

Cut off fuel immediately

35
Q

Gas turbine load control depends upon

A

The load shaft speed

36
Q

List the five gas turbine alarm singals

A

High vibration Generator stator high temp Ignition tripped High differential pressure air intake Low lub oil pressure

37
Q

What do you do with high vibrations

A

Close fuel supply

38
Q

No ignition will result in

A

Fire or explosion

39
Q

High differential air pressure indicates

A

Dirty air inlet filters

40
Q

Why is lubrication essential

A

Lube bearings Cooling of bearings

41
Q

Define a major overhaul turbine maintenance

A

A total strip down and checking or replacing

42
Q

Define short shutdown turbine maintenance

A

Clean and replace air inlet filters, wash compressor blading and replace bearings and coupling

43
Q

Aging factor results in

A

.5% in power and efficiency loss for 1000 hours of services

44
Q

Why do we cool the turbine blades?

A

So they don’t melt

45
Q

HRSG

A

Heat recovery steam generator

46
Q

Sag in a turbine shaft is called

A

Bowing

47
Q

What is a regenerator

A

Takes heat from the exhaust to heat compressed air in the turbine

48
Q

Define cogeneration

A

Takes hot exhaust gasses to boil water to produce steam Highest efficiency available

49
Q

A major drawback of the gas turbine

A

Nox emissions are high Low mechanical efficiency

50
Q

The compressor chamber of a gas turbine

A

Can be driven by the load turbine

51
Q

Many typical steam plant auxiliaries are eliminated with a gas turbine due to its

A

SIMPLICITY

52
Q

The temperature to which the air can be raised at the turbine inlet is

A

A indication of the units efficiency

53
Q

DP

A

Differential Pressure