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Power Engineering- 4th Class > Chapter 69- Steam Turbines > Flashcards

Chapter 69- Steam Turbines Flashcards

1
Q

A steam turbine is considered

A

A prime mover

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2
Q

Where does a steam turbine derive its power?

A

Extracts energy from steam in order to do work and produce useful energy

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3
Q

Define an impulse turbine

A

If the entire steam pressure drop takes place in stationary nozzle
Imparts a force on the moveable blades

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4
Q

Define a reaction turbine

A

If the steam pressure drops in passing through moving blades as well as stationary nozzles or blades.

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5
Q

On an impulse turbine are the blades in constant contact with steam?

A

No only a portion of the blades are in contact at any given time

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6
Q

Impulse turbines the nozzles preform what function on the steam

A

Pressure is reduced and velocity is increased in the steam

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7
Q

An impulse rotor with a single rotor is called

A

A single stage impulse rotor

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8
Q

Multi staged impulse turbines were developed to

A

Make full use of the steam energy

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9
Q

High rotational speed in an impulse turbine

A

Will cause damage to the blades due to excessive centrifugal force

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10
Q

There are two types of impulse turbine compounding

A

Velocity compounding and pressure compounding

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11
Q

In an impulse turbine the steam pressure

A

Drops quickly

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12
Q

In a reaction turbine steam pressure

A

The pressure drops gradually

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13
Q

Define bearings

A

The bearings have a split sleeve and oil ring, with a precision bored high grade Babbitt lubrication is done by oil rings that are rotated by the shaft

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14
Q

Define Glands

A

The gland consists of several adjacently mounted segmental carbon rings, each maintained in close contact with the shaft by a garter spring and each located in its own independent groove this prevents steam leakage in the wheel shaft

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15
Q

What are blades

A

All blades are durable, rolled and drawn stainless steel,securely held in machined slots in the wheel ring by drive screws

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16
Q

In multi stage turbines what happens to the rotors?

A

They get bigger

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17
Q

What are the different types of impulse turbines

A

Pressure compounding
Velocity compounding
Pressure and velocity compounding
Single stage

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18
Q

How do you balance pressure in a steam turbine?

A

With a dummy piston

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19
Q

Turbine speed is controlled by the

A

Governor

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20
Q

Main cause of excessive speeds in turbines

A

Sudden loss of load

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21
Q

Two types of over speed trips

A

Mechanical and electronic

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22
Q

Mechanical overspeed trip

A

The extended weight, by centrifugal force, moves a lever which releases a spring that opens the control valve reducing speed dramatically

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23
Q

An overspeed trip usually trips at about

A

10-15% over the rated speed

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24
Q

Hand speed control

A

Located on the governor with a normal range of 10% over and 50% below the rated speed

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25
Q

An advantage of the steam turbine regarding lubrication

A

Bearings are located the high temperature steam zone, so it can deliver oil free condensate or exhaust steam

26
Q

Large steam turbines can run at lower speeds because of

A

Compounding

27
Q

Rotors often have segmental carbon ring sealing glands which are held in place by

A

Garter springs

28
Q

A steam turbine should trip or shut down when normal operating speed is exceeded by

A

10-15%

29
Q

Condensing turbines

A

Will have a vacuum in the last row of rotating blades

30
Q

In a reaction turbine the velocity increase takes place in

A

Rotating blades, and stationary blades

31
Q

The stationary passage of reaction turbines are the

A

Fixed blades

32
Q

Blades or _________ form the rotor flow passages in impulse turbines

A

Buckets

33
Q

The shrouding which connects the tips of the steam turbine blading serves to

A

Confine steam to the blades

34
Q

Turbine overspeed trip

A

Will close the steam stop valve to the turbine

35
Q

Turbine lubrication oil during use has these characteristics dealing with maintenance

A

Can be contaminated with water
Must be cooled
Can be used for the turbine governor
Must be filtered

36
Q

Shaft sealing of steam turbines is done with

A

Water sealed glands
Carbon rings
Labyrinth seals when temperatures and pressure of the steam is high

37
Q

The purpose of turbine glands is to prevent

A

Steam escaping from the turbine

38
Q

Shaft sealing in high output turbines is done with

A

Labyrinth seals

39
Q

Steam turbine governors

A

Regulate the speed of the turbine automatically

40
Q

The great majority of turbine governors are of the ________ type

A

Mechanical centrifugal type

41
Q

The hand wheel used to adjust the turbine speed on the governor is known as the

A

Speeder

42
Q

When the steam pressure drop occurs in only the stationary members or components of a turbine, the turbine is known as an

A

Impulse unit

43
Q

A large reaction turbine will have

A

Steam pressure dropping through moving and stationary sections

44
Q

Turbine speed can be fine tuned with a device which will be limited to about 10% over the rated speed. This device is the

A

Hand speed control

45
Q

Turbine thrust bearings are fixed to the casing and prevent ________ movement of the shaft

A

Axial

46
Q

Shaft sealing carbon glands are

A

Self lubricating

47
Q

Impulse turbines have these distinct characteristics

A

Have velocity increase through the nozzles
Blades have a angle of inlet same as the outlet
Could have more than one set of blades
May not require a thrust bearing

48
Q

The principles of the impulse turbine is that the

A

Steam pressure is reduced through stationary nozzles
High velocity steam will impinge upon the blades
Steam pressure will drop across the blades

49
Q

The steam turbine that has a pressure drop across varying sets of blades is a

A

Reaction turbine

50
Q

In an impulse turbine, all of the steam pressure drop takes place in the

A

Stationary nozzle

51
Q

In a reaction turbine the steam pressure in passing through moving blades, as well as stationary nozzles or blades

A

Drops

52
Q

Journal bearings do (2)

A
  • prevent radial movement of the shaft

* support the shaft with in the turbine

53
Q

Sentinel valves do

A

Relieves high pressure on the exhaust side of the casing

54
Q

What is turbine blading?

A

A combination of impulse and reaction rotors

55
Q

Exhaust steam from a condensing steam turbine _____than the exhaust from a steam engine

A

Has more moisture

56
Q

Which turbine uses a condenser

A

A turbine exhausting to a vacuum

57
Q

A shrouding installed on the blading of a steam turbine serves to

A

Confine the steam to the blades

58
Q

Turbine over speed trip (3)

A
  • prevents exceeding max speed
  • will close the steam stop valve
  • should be tested before turbine is placed in services
59
Q

Turbine trust bearings are fixed to the casing and prevent axial movement of the spindle by contacting a component on the shaft known as

A

Collar

60
Q

Steam engines that has a pressure drop across every set of blades

A

Reaction

Power Engineering- 4th Class (27 decks)

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