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Turbines (Steam, Gas and Water) Flashcards

1
Q

How are gas turbines classified on combustion process ?

A

Constant Volume

Constant Pressure

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2
Q

How are gas turbines classified on action of expanding gases ?

A

Impulsive forces

Impulsive-Reactive force

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3
Q

How are gas turbines classified on working path of gases ?

A

Open cycle gas turbine

Closed cycles gas turbine

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4
Q

How are gas turbines classified on direction of flow ?

A

Axial

Radial

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5
Q

What is axial flow ?

A

Flow of working fluid is parallel to axis of shaft

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6
Q

What is radial flow ?

A

Flow of working fluid is in direction of radius

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7
Q

How are gas turbines classified on shaft configuration ?

A

Single shaft

Multiple Shaft

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8
Q

How are gas turbines classified on thermodynamic cycle ?

A

Simple cycle
Simple cycle with regenerator
Simple cycle with re-heat

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9
Q

How are gas turbines classified on basis of application ?

A

Aviation

Industrial

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10
Q

What are the three main components of open cycle gas turbines ?

A

Compressor
Combustion Chamber
Gas turbine

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11
Q

What is the function of the compressor ?

A

It draws air from the atmosphere and compresses it to high pressure adiabatically

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12
Q

What is an adiabatic process ?

A

A process that occurs without transfer of heat or matter between a system and it’s surroundings.

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13
Q

What happens in the combustion chamber ?

A

Fuel is injected into the high pressure air and combustion takes place. The temperature of the air increases at constant pressure

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14
Q

What happens in the gas turbine ?

A

The product of the combustion chamber is expanded on the turbine blade adiabatically.

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15
Q

What happens to the thermal energy of the gas ?

A

It is extracted by the turbine and converted to power

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16
Q

Why are the turbine and compressor mechanically coupled via a shaft ?

A

Some energy is used to turn a shaft to drive the compressor

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17
Q

Why are closed cycle gas turbines smaller than open cycle gas turbines ?

A

High density working fluid is used

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18
Q

Which gas turbine has a greater thermal efficiency ?

A

Closed cycle gas turbines have a greater thermal efficiency for the same range of temperatuer

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19
Q

Why is there less corrosion in closed cycle gas turbines ?

A

Working fluid is not contaminated because of indirect heating.

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20
Q

How is the working fluid contaminated in open cycle gas turbines ?

A

Fuel combustion

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21
Q

Which turbine offers a greater output ?

A

Closed cycle gas turbines have a greater output per unit weight of turbine

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22
Q

What is the reason expensive fuels are used in open cycle gas turbines ?

A

Fuel comes in contact with working medium and should not contaminate it.

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23
Q

Why are closed cycle gas turbines not suitable for avionics ?

A

They need cooling water or a coolant to remove heat

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24
Q

Why is heat transfer efficiency lower in closed cycle gas turbines ?

A

Heat is transfered indirectly and higher heat transfer area is required

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25
Q

What kind of heat exchangers required in closed cycle gas turbines ?

A

Complicated heat exchangers

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26
Q

Why does the closed cycle gas turbine need to be perfectly sealed ?

A

The working medium should not leak.

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27
Q

Do gas turbines have a greater thermal efficiency than IC Engines ?

A

Yes, because they do not have any reciprocating component.

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28
Q

What is the reason gas turbines can be operated at a much higher speed than IC engines ?

A

They are better balanced.

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29
Q

Why are they better balanced ?

A

There is no reciprocating component.

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30
Q

Why can cheaper fuels be used in gas turbines than in IC engines ?

A

External combustion

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31
Q

Why are gas turbines more suited to avionics application than IC engines ?

A

Lower specific weight and higher reliability.

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32
Q

Why are gas turbines less polluting than IC engines ?

A

External combustion means higher air to fuel ratio

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33
Q

Do gas turbines have a higher thermal efficiency than IC engines ?

A

No, IC engines have a (15-20%) higher thermal efficiency

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34
Q

Why do gas turbines require speed reduction gear box ?

A

It operates at higher speeds

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35
Q

Which is hard to start ?

A

Gas turbines

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36
Q

Which has simpler lubrication and ignition system ?

A

Gas turbines have a simpler lubrication system and ignition system

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37
Q

Why is blade fabrication for gas turbines harder ?

A

High strength Nickel chromium alloys

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38
Q

How much AMOUNT of exhaust gases do gas turbines produce ?

A

About five times as much as IC Engines for the same output power

39
Q

Why does gas turbine cooling need more elaborate arrangement, even though it need less cooling than IC Engines ?

A

The cooling has to be done to the blades

40
Q

How are gas turbines lighter than steam turbines ?

A

They do not need bulky and expensive boiler with their mountings and accessories

41
Q

Are gas turbines more expensive than steam turbines ?

A

No, they have less initial and operating cost

42
Q

Which has higher reliability ?

A

Gas turbines are more reliable than steam turbines

43
Q

Which turbines are easier to start and control ?

A

Gas Turbines

44
Q

How is the fuel more efficiently used in gas turbines ?

A

The fuel drives the turbine directly without producing an intermediate fluid like steam.

45
Q

Where are gas turbines widely used ?

A

Aerospace like turbo jet, turbo-propellor and rocket engines

46
Q

What kind of plants are they used in ?

A

Peak load supplementary plants, central power station and high power pumping station

47
Q

How are water turbines classified based on head and Quantity of water available ?

A

High
Medium
Low

48
Q

What is the maximum head available for high head turbines ?

49
Q

What is an example of high head turbine ?

50
Q

What is the range of head available for medium head turbine ?

51
Q

What is an example of medium head turbine ?

A

Francis turbine is a medium head turbine

52
Q

What is the range of low head turbines ?

53
Q

How are water turbines classified based on nature of water interaction ?

A

Impulse

Reaction

54
Q

What is an impulse turbine ?

A

Pressure of water does not change while flowing through the rotor

55
Q

What is a reaction turbine ?

A

Pressure of water changes while flowing through rotor

56
Q

What is an example of impulse turbine ?

A

Pelton wheel turbine

57
Q

What is an example of reaction turbine ?

A

Francis or Kaplan turbine

58
Q

What are water turbines classified based on nature of water flow ?

A

Radial
Tangential
Axial
Mixed

59
Q

What happens in radial flow turbines ?

A

Water flows from inlet to outlet of rotor along radius

60
Q

What is an example of radial flow turbine ?

A

Initial Francis turbine

61
Q

What happens in tangential flow turbines ?

A

Water flows tangential to runner

62
Q

What is an example of tangential flow turbine ?

A

Pelton wheel turbine

63
Q

What is a mixed flow turbine ?

A

Water enter rotor radially, but exits axially

64
Q

What is an example of mixed flow turbine ?

A

Modern Francis turbine

65
Q

What is an axial flow turbine ?

A

Water flows parallel to axis of turbine shaft

66
Q

What is an example of axial flow turbine ?

A

Kaplan turbine

67
Q

How are water turbines classified based on orientation of shaft ?

A

Horizontal

Vertical

68
Q

Which turbine, in modern day practice, has a horizontal shaft ?

69
Q

How is specific speed of a water turbine defined ?

A

It is the speed of geometrically similar turbine which will develop one brake power using 1 meter head of water

70
Q

What is the speed of Pelton turbine ?

71
Q

What is the speed of Francis turbine ?

72
Q

What is the speed of Kaplan turbine ?

A

300 to 1000

73
Q

How are water turbines classified based on originator ?

A

Pelton
Francis
Kaplan

74
Q

What kind of a turbine is Pelton turbine ? (Basic characteristics)

A

Impulse, high head - low discharge

75
Q

What kind of a turbine is Francis turbine ?

A

Reaction, medium to low head

76
Q

What kind of turbine is Kaplan turbine ?

A

Reaction, low head, high quantity of water flow

77
Q

What kind of vanes do Francis turbines use ?

A

Moving, non adjustable vanes

78
Q

What kind of vanes do Kaplan turbines use ?

A

Adjustable with governing mechanism

79
Q

What kind of a governor does a Francis turbine use ?

A

Simple governor

80
Q

What kind of a governor does a Kaplan turbine use ?

A

Heavy duty governor

81
Q

Why do Kaplan turbines use heavy duty governor ?

A

It governs both the flow of water and movement of vanes

82
Q

How many vanes do Francis turbines have ?

83
Q

How many blades to Kaplan turbines have ?

A

3 to 8 blades

84
Q

What kind of flow rate does Francis turbine deal with ?

85
Q

What kind of flow rate does Kaplan turbine deal with ?

A

High flow rate

86
Q

What is the maximum head of Kaplan turbine ?

87
Q

What are the five main parts of a Pelton wheel turbine ?

A 
Wheel
Bucket
Nozzle with controller
Auxiliary jet
Casing
88
Q

What is wheel ?

A

The rotating disc mounted of the shaft

89
Q

How are the buckets and wheel casted in large power plants ?

A

They are casted together

90
Q

Why ?

A

This provides high power and efficiency

91
Q

How are they casted in medium power plants ?

A

Seperately

92
Q

How are buckets and the wheel casted in medium to small power plants ?

A

By nuts and bolts

93
Q

Where are the buckets uniformly fixed ?

A

On the periphery of the disc

94
Q

What are the buckets made up of ?

A

Stainless steel

Mechanical Engineering (8 decks)

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