Chapter 69- Steam Turbines

Question 1

A steam turbine is considered

Answer 1

A prime mover

Question 2

Where does a steam turbine derive its power?

Answer 2

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

Question 3

Define an impulse turbine

Answer 3

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

Question 4

Define a reaction turbine

Answer 4

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

Question 5

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

Answer 5

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

Question 6

Impulse turbines the nozzles preform what function on the steam

Answer 6

Pressure is reduced and velocity is increased in the steam

Question 7

An impulse rotor with a single rotor is called

Answer 7

A single stage impulse rotor

Question 8

Multi staged impulse turbines were developed to

Answer 8

Make full use of the steam energy

Question 9

High rotational speed in an impulse turbine

Answer 9

Will cause damage to the blades due to excessive centrifugal force

Question 10

There are two types of impulse turbine compounding

Answer 10

Velocity compounding and pressure compounding

Question 11

In an impulse turbine the steam pressure

Answer 11

Drops quickly

Question 12

In a reaction turbine steam pressure

Answer 12

The pressure drops gradually

Question 13

Define bearings

Answer 13

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

Question 14

Define Glands

Answer 14

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

Question 15

What are blades

Answer 15

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

Question 16

In multi stage turbines what happens to the rotors?

Answer 16

They get bigger

Question 17

What are the different types of impulse turbines

Answer 17

Pressure compounding
Velocity compounding
Pressure and velocity compounding
Single stage

Question 18

How do you balance pressure in a steam turbine?

Answer 18

With a dummy piston

Question 19

Turbine speed is controlled by the

Answer 19

Governor

Question 20

Main cause of excessive speeds in turbines

Answer 20

Sudden loss of load

Question 21

Two types of over speed trips

Answer 21

Mechanical and electronic

Question 22

Mechanical overspeed trip

Answer 22

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

Question 23

An overspeed trip usually trips at about

Answer 23

10-15% over the rated speed

Question 24

Hand speed control

Answer 24

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

Question 25

An advantage of the steam turbine regarding lubrication

Answer 25

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

Question 26

Large steam turbines can run at lower speeds because of

Answer 26

Compounding

Question 27

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

Answer 27

Garter springs

Question 28

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

Answer 28

10-15%

Question 29

Condensing turbines

Answer 29

Will have a vacuum in the last row of rotating blades

Question 30

In a reaction turbine the velocity increase takes place in

Answer 30

Rotating blades, and stationary blades

Question 31

The stationary passage of reaction turbines are the

Answer 31

Fixed blades

Question 32

Blades or _________ form the rotor flow passages in impulse turbines

Answer 32

Buckets

Question 33

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

Answer 33

Confine steam to the blades

Question 34

Turbine overspeed trip

Answer 34

Will close the steam stop valve to the turbine

Question 35

Turbine lubrication oil during use has these characteristics dealing with maintenance

Answer 35

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

Question 36

Shaft sealing of steam turbines is done with

Answer 36

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

Question 37

The purpose of turbine glands is to prevent

Answer 37

Steam escaping from the turbine

Question 38

Shaft sealing in high output turbines is done with

Answer 38

Labyrinth seals

Question 39

Steam turbine governors

Answer 39

Regulate the speed of the turbine automatically

Question 40

The great majority of turbine governors are of the ________ type

Answer 40

Mechanical centrifugal type

Question 41

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

Answer 41

Speeder

Question 42

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

Answer 42

Impulse unit

Question 43

A large reaction turbine will have

Answer 43

Steam pressure dropping through moving and stationary sections

Question 44

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

Answer 44

Hand speed control

Question 45

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

Answer 45

Axial

Question 46

Shaft sealing carbon glands are

Answer 46

Self lubricating

Question 47

Impulse turbines have these distinct characteristics

Answer 47

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

Question 48

The principles of the impulse turbine is that the

Answer 48

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

Question 49

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

Answer 49

Reaction turbine

Question 50

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

Answer 50

Stationary nozzle

Question 51

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

Answer 51

Drops

Question 52

Journal bearings do (2)

Answer 52

* prevent radial movement of the shaft | * support the shaft with in the turbine

Question 53

Sentinel valves do

Answer 53

Relieves high pressure on the exhaust side of the casing

Question 54

What is turbine blading?

Answer 54

A combination of impulse and reaction rotors

Question 55

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

Answer 55

Has more moisture

Question 56

Which turbine uses a condenser

Answer 56

A turbine exhausting to a vacuum

Question 57

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

Answer 57

Confine the steam to the blades

Question 58

Turbine over speed trip (3)

Answer 58

* prevents exceeding max speed * will close the steam stop valve * should be tested before turbine is placed in services

Question 59

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

Answer 59

Collar

Question 60

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

Answer 60

Reaction