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Power Engineering > 4b power engineering > Flashcards

4b power engineering Flashcards

1
Q

example of a prime mover

A

steam turbine

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2
Q

advantages of a steam turbine over a diesel engine

A 
smaller foundation, lighter, less expensive
greater thermal efficiency
easily coupled with electrical generator
no lubrication- oil free exhaust
more reliable, reduced vibrations
lower maintenance costs
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3
Q

5 steps in starting up a typical steam engine

A

Ensure no tools are left in the way of moving parts
open drain cocks on steam chest and cylinders
open separator drain and empty of water
once water stops flowing, open stop valve slightly until steam flows freely through the drains
Slowly open steam valve. to prevent water hammer

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4
Q

Steam flow is regulated to control engine speed by

A

throttle valve

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5
Q

A steam turbine’s exhaust can supply a process with steam because

A

it is free of oil

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6
Q

2 types of steam turbines

A

Reaction and Impulse

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7
Q

The stationary passage of reaction turbines is the

A

fixed blade

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8
Q

Larger high output machines use a shaft seal known as

A

labyrinth glands

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9
Q

6 steps in shutting down a large condensing turbine

A

regulate steam supply as load is reduced
start auxiliary oil pump
when stop order is received, the stop valve may be closed gradually
watch that bearings are getting proper oil supply
shut off steam supply and water to the glands
when machine has stopped, shut off water supply to the oil coolers and stop the aux oil pump

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10
Q

In order to move the throttling valve in a large steam turbine, a governing system uses a

A

pilot valve

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11
Q

Dirty air filters on a gas turbine could lead to what

A

high differential air intake

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12
Q

cooling tower design in which the fan is least likely to ice up is

A

dry cooling tower

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13
Q

What is a diesel engines camshaft driven by

A

gears from the crankshaft

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14
Q

in a venture type cooling tower, how is airflow created

A

by spray nozzles

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15
Q

A gas turbine

A

heats compressed air

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16
Q

crossflow mechanical draft cooling tower

A

has a low pressure drop

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17
Q

Rate of heat transfer in a cooling tower depends on

A

Exposure area of water surface in contact with the air
Residence time
Relative velocity of air and water during contact
temp differential of inlet water temp and relative humidity of the air

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18
Q

Advantages of steam engine include

A

It is possible to change direction without gears

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19
Q

How high might compression ration in a diesel engine be

A

25:1

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20
Q

A very accurate method of checking flanges for offset and axial misalignment which can be used on any flanges is the

A

dial indicator

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21
Q

A stuffing box

A

stops air leaking into the casing, and is filled with packing

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22
Q

Valves on a reciprocating compressor are opened by

A

Pressure differential

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23
Q

What is the purpose of bleeding hot air from the compressor of a gas turbine and reintroducing it to the compressor inlet

A

anti icing

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24
Q

large internal combustion engines achieve cooling by use of

A

water jackets

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25
Q

The reciprocating motion of a steam engine is converted to rotory motion

A

via the valve gear

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26
Q

How are microbiological organisms most effectively killed in cooling tower

A

by temporarily raising the concentration of the chemical to a high level

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27
Q

Packing rings

A

are pressed into packing glands to provide a seal

28
Q

packing glands

A

provide a seal around piston rod and valve rod

29
Q

Governor

A

controls engine speed by regulating steam flow to the engine as load on the engine changes

30
Q

If the steam pressure drops in the stationary blades of a turbine, it is classified as an

A

impulse turbine

31
Q

Rotor passages of a steam turbine consists of blades or buckets which are attached to

A

the turbine rotors

32
Q

With some governors, the oil pump is driven from the

A

turbine shaft

33
Q

The purpose of the hand speed changer is to

A

allow the operating speed to be varied

34
Q

To avoid excessive speeds in turbines, when load is suddenly reduced, they are fitted with

A

overspeed trips

35
Q

Cooling towers are divided into 2 classes.

A

Mechanical and Natural draft

36
Q

sub classes of natural draft cooling towers are

A

atmospheric towers and chimney towers

37
Q

3 tasks to be performed monthly in an atmospheric tower

A

clean scale, dirt, algae from louvers, piping and nozzles
clean water basin and check for leaks
clean the suction screen and check the float control valve

38
Q

water distributors purpose and construction

A

fiberglass, wooden or stainless steel piping and spray nozzles spray water into the top section of the tower.

39
Q

side louvers

A

wooden or fiberglass panels direct air flow into the towers

40
Q

side sheeting

A

cement board or fiberglass panels enclosing the cooling tower

41
Q

fill or packing

A

wood or plastic slats which fill the tower below the water inlet sprays and ensure that the water surface area is large providing good contact with air

42
Q

Mist eliminators

A

wood or plastic slats located above the inlet water sprays to remove water carried along with the air flow

43
Q

water basin

A

concrete containment located at the bottom of the cooling tower to collect the cooled water falling from the fill

44
Q

fans

A

stainless steel or plastic fans located at the top of the cooling tower to draw air through the tower opposite to the water flow.

45
Q

The cause of corrosion in a cooling tower

A

low pH (below7.5) and dissolved oxygen which is high because water is constantly circulated through the tower

46
Q

wood delignification is caused by

A

attack of chlorine and alkaline solutions and biological attack of wood cellulose

47
Q

hot air from the gas turbine combustor is expanded through

A

the turbine blading

48
Q

In a simple gas turbine, air is first drawn into the compressor and compressed air is discharged into

A

the combustor

49
Q

Prior to fuel being admitted, an auxiliary starting motor is used to bring a gas turbine up to a speed of

A

20-30% of operating speed

50
Q

Typically it takes how long to start up a steam turbine

A

8-12 hours

51
Q

The 4 strokes referred to in a four stroke cycle engine are

A

intake, compression, power, exhaust

52
Q

what keeps the oil in the crankcase out of the cylinder walls

A

piston rings

53
Q

How is the crankshaft and bearings of a 2 stroke cycle engine are lubricated

A

oil and gas are mixed together and drawn through the crankcase

54
Q

what is the pressure and temperature of a typical compression ignition engine

A

2800-4200kPa and 540-650 C

55
Q

removal of exhaust gases from the engine cylinder before the compression stroke is called

A

scavenging

56
Q

What is the ideal cooling water temperature in a large industrial diesel engine

A

50-65 C

57
Q

when a pump is located above the source of supply, the vertical distance from the surface of the supply to the pump center line is called

A

Static suction lift

58
Q

static suction head is

A

when a pump is below the source of supply the vertical distance from the surface of the supply to the pump center line

59
Q

the distance measured from the pump center line to the surface of the liquid in the discharge tank or to the free end of the discharge line

A

discharge head

60
Q

vertical distance, measured in meters or feet of water, between the level in the suction tank of a pump to the level in the discharge line.

A

Total static head

61
Q

the sum of friction, velocity and pressure head expressed in meters or feet of water head

A

Dynamic head

62
Q

The force required to put the water in motion

A

Velocity head

63
Q

the sum of static and dynamic head

A

Total head

64
Q

The additional pressure required to overcome the pressure inside a closed discharge tank such as a boiler

A

Pressure or equivalent head

65
Q

Describe how the power requirement of a centrifugal pump is affected by throttling in on the pump discharge valve

A

the power requirements of the pump are reduced because the pump is transferring less water and therefore doing less work

66
Q

Directing the flow from one centrifugal pump impeller to the inlet of another is referred to as

A

staging

67
Q

a positive displacement pump should always be equipped with a relief valve that is located

A

on the discharge of the pump before the isolation valve

Power Engineering (7 decks)

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