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Millwright Level 4 > Prime Movers > Flashcards

Prime Movers Flashcards

1
Q

Four stroke engines come in these two types

A

Naturally aspirated or supercharged

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2
Q

Compression ratios of diesel engines

A

16:1 - 23:1 (gas engines are 6:1 - 13:1)

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3
Q

Diesel engines use these to preheat the combustion chamber

A

Glow plugs (not needed to keep running)

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4
Q

How is fuel supplied in a Diesel engine

A

fuel injection (mechanical most common)

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5
Q

How is fuel supplied to a gas engine

A

Carburetor (atomized) or fuel injection

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6
Q

These gas burning engines are designed to burn different, or combinations of fuels

A

High-compression gas burning engines

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7
Q

What are the four strokes of a four-stroke engine

A

Intake (intake valve open), compression (valves closed), power (valves closed), exhaust (exhaust valve open) (done in two revolutions of the crankshaft)

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8
Q

When does ignition take place in a ICE?

A

BTDC

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9
Q

This provides a smooth transition between power strokes

A

Flywheel (clutch mounts to this)

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10
Q

At the end of the exhaust stroke where both intake and exhaust valves are open this is called

A

valve overlap

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11
Q

In a two-stroke engine these two things happen while the piston is at BDC

A

Intake and exhaust (not during a stroke)

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12
Q

two-strokes are completed in how many revolutions of the crankshaft

A

one

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13
Q

If a two-stroke does not use exhaust valves or blowers it used this instead

A

Scavenging valve (in the crankcase)

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14
Q

This supports the pistons and transfers energy of motion

A

Crankshaft (takes reciprocating motion and turns to rotary)

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15
Q

How is oil supplied to bearings of a 4 stroke

A

oil holes in crankshaft

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16
Q

This connects the piston to the crankshaft

A

Connecting rod (wrist pin to piston)

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17
Q

Do gas engines use cylinder liners?

A

No

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18
Q

This consists of valves, valve springs, rocker arms and rocker arm shaft

A

cylinder head assembly

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19
Q

The camshaft goes how fast compared to the crankshaft

A

One half the speed

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20
Q

The engine block is made of

A

cast iron, cast aluminum

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21
Q

These are powered by exhaust waste gases

A

turbochargers (speeds of 10k to 100k rpm)

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22
Q

These are mechanical blowers and found in lots of two-stroke engines

A

superchargers (rotary lobe)

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23
Q

Steam turbines use this and convert it to kinetic energy

A

superheated steam (400-560C 750-1050F) (200psi - 450psi)

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24
Q

The greater the temperature difference across the turbine, the more _____ it is

A

efficient

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25
Q

What is each stage of a turbine consist of

A

a stationary nozzle followed by a rotating blade (staging used to maximize energy of the steam as it flows through)

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26
Q

This controls the amount of steam admitted to the turbine for speed control

A

Governor (SAV)

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27
Q

in this turbine steam flow is perpendicular to the turbine shaft

A

Radial flow (no stationary nozzles other than first stage, every set of blades move in opposite direction)

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28
Q

The main use for back-pressure turbines

A

draft fans, water pumps (low pressure)

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29
Q

This turbine uses high pressure steam to drive the turbine and exhausts to a low pressure system

A

Back pressure/extraction (steam can be extracted at intermediate pressures)

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30
Q

What does closing an extraction valve do

A

extracts MORE steam (extraction valve has a check valve)

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31
Q

This is the most efficient steam turbine

A

Condensing (produces a vacuum at the exhaust, causes largest pressure drop)

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32
Q

What does a condensing turbine use to condense steam

A

tube and shell heat exchanger used to cool and condense steam

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33
Q

What energy do impulse blades produce

A

kinetic

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34
Q

What energy do reaction blades produce

A

potential

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35
Q

In an impulse/reaction turbine which blades are used first

A

impulse (on higher pressure side)

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36
Q

How are blades of steam turbines attached to the shaft

A

disc or drum

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37
Q

What does shrouding do

A

Keeps blades rigid, directs steam, less vibration (wires used on large blading)

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38
Q

Types of bearings used in steam turbines

A

Journal, thrust, and dummy pistons (balance)

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39
Q

Where are the first nozzles found in a steam turbine

A

In the steam chest (later stages are in diaphragms)

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40
Q

Nozzles in steam turbines are designed to _______ towards the outlet

A

converge (inlet larger than outlet)

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41
Q

What do the shaft seals in steam turbines do

A

keep high pressure steam from leaking into the surrounding area
stop air from being admitted into the turbines
(Carbon and labyrinth)

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42
Q

How are seals lined up in a steam turbine

A

Gland seal system. Labyrinth first, carbon behind it (low pressure steam supplied to seals at start up)

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43
Q

What removes the non condensible gases in a hot well

A

steam injectors or small vacuum pump

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44
Q

Order of valves in a steam turbine

A

Stop valve, throttle valve (emergency trip integrated), governor, extraction, non return on extraction valve, exhaust

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45
Q

What does the throttle valve do

A

bring turbine up to speed until governor takes over speed control, warms up turbine

46
Q

What must always be one of the trips for emergency trip valves

A

overspeed (throttle valve must be closed before trip can be reset)

47
Q

What supplies hydraulic governors with oil

A

main oil pump (integral), auxiliary oil pump (electric), emergency oil pump (battery)

48
Q

What controls the bearing temps in a steam turbine

A

in-line oil coolers

49
Q

What is the desired bearing oil outlet temp in a steam turbine

A

55 - 66 C

50
Q

The process of turning a turbine until it is cooled is called

A

barring

51
Q

What turns a turbine when it is shut down

A

turning gears (barring gears)

52
Q

Major difference between a steam and gas turbine

A

gas turbine has a compressor

53
Q

Three main sections of a gas turbine

A

compressor, combustor, turbine

54
Q

How are gas turbines categorized

A

Cycle: the path the medium (air) passes

Shaft arrangement: One shaft or two

55
Q

This gas turbine uses a recuperator and a precooler

A

Closed cycle

56
Q

Combustion in a gas turbine works on this principle

A

flame propagation

57
Q

This is the hottest part of the system in a gas turbine

A

flame tube (first to wear out) 900C

58
Q

Gas turbines have to withstand

A

the greatest stress from heating and loading

59
Q

How are the blades cooled in a gar turbine

A

Convection (compressed air, most common. reduces 300C)
Transpiration (steam)
This is an integral part of the design not auxiliary

60
Q

How are gas turbine blades shaped

A

Impulse at the root, reaction at the top

61
Q

Do gas turbines use mechanical governors

A

No

62
Q

How are oil pumps driven in gas turbines

A

separately from the turbine

63
Q

These support the field windings and act as a magnetic path between frame and armature

A

Field poles

64
Q

The brushes of a DC motor ride on this

A

Commutator (feeds the external electrical supply into the rotating coils)

65
Q

This DC motor has high starting torque but poor speed regulation

A

Series motor - can’t be operated under no load

66
Q

This DC motor has good speed regulation but low starting torque

A

Shunt (parallel) - if operating at no load speed will rise very quickly

67
Q

This DC motor has good starting torques and good speed regulation

A

Compound

68
Q

What are the three types of ways to quick stop a DC motor

A

Dynamic braking
Regenerative braking
Plugging (reversal)

69
Q

This AC motor is used for heavy loads that run for long periods of time

A

Synchronous

70
Q

Types of three phase AC motors

A

Squirrel cage (Induced, no connection between rotor and stator) Starting torque normal to high

Wound rotor (rotor has insulated windings)

Synchronous (need assistance in starting, can run heavy loads for long periods)

71
Q

Types of single phase AC motors

A

Split-phase: (auxiliary winding helps start motor)

Capacitor-start: High starting torque, switch disconnected 3/4 speed

Permanent-split capacitor: No centrifugal switch, low starting torque

Repulsion: Magnetic push, high torque, variable speed

72
Q

This reduces crankshaft torsional vibration

A

harmonic balancer

73
Q

This engine has a larger bore diameter than stroke length

A

oversquare engine

74
Q

This engine has a longer stroke than bore diameter

A

undersquare engine (usually diesel)

75
Q

The volume remaining above the piston at TDC

A

Clearance volume

76
Q

Most engines are this efficient

A

25-35%

77
Q

The leakage of burned and unburned gases past the compression rings into the crankcase

A

Blowby

78
Q

Low speed engines operate below this rpm

A

500
Medium 500-1000rpm
High over 1000rpm

79
Q

These engine types are built with a load as part of the engine

A

Integral

80
Q

Running mates apply to

A

4 stroke engines only (reach TDC at the same time)

81
Q

This is a warning device on small turbines

A

Sentinel valve

82
Q

The total energy available from the steam is due to its heat, weigh, pressure and velocity. This is called

A

Enthalpy of steam

83
Q

On a steam turbine where is the thrust bearing located

A

Steam inlet end

84
Q

Assemble carbon rings according to their

A

match marks

85
Q

These seals are used instead of labyrinth when axial movement is a factor

A

Annulus

86
Q

The weight of the blade multiplied by radial distance to the centre of gravity of each blade

A

Moment weight

87
Q

Overspeed trip setting set at

A

110-115% of operating speed

88
Q

part of the rotor with several stepped diameters that the steam pressure in the turbine push against to counteract thrust

A

Dummy (balance) piston

89
Q

How big should the foundation of a turbine be

A

2.5 times the mass of the turbine assembly

90
Q

The highest pressure in a gas turbine is in the

A

diffuser

91
Q

Drum rotors are for ___ speed, disk rotors are for ___ speed

A

Drum (low)

Disk (high)

92
Q

Constant speed gas turbines do not use these

A

variable pitch stator blades

93
Q

3 zones of the gas turbine combustion chamber

A

Primary (first part where fuel injection and combustion begins)
Intermediate (combustion mixes with secondary air)
Dilution (combustion complete, secondary air mixed with burnt gases)

94
Q

Francis and kaplan are considered ______ turbines

A

reaction

95
Q

The motor is momentarily converted to a generator, but cannot come to a full stop

A

Dynamic braking

96
Q

If a motor requires sudden or repeated stops, this reverses the armature circuit polarity

A

Plugging

97
Q

This hydro turbine uses water sources with high head

A

Pelton (impulse style buckets)

98
Q

Four main parts of a wind turbine

A

Foundation, tower, nacelle, rotor

99
Q

Francis and Kalpan turbines are used in these situations

A

low head, high flow (francis most common)

100
Q

Frame motor sizes are classified by this

A

Diameter

101
Q

Name the 4 DC motors

A

Series (high starting torque)
Shunt (speed control)
Compound (constant speed)
Permanent-Magnet (poor speed control)

102
Q

Motors known for the constant speed characteristics

A

Three phase AC

103
Q

These engines are used in pipelines

A

High-compression gas burning

104
Q

Order of rings on a piston

A

2 compression rings at the top, oil ring on bottom

105
Q

How is the camshaft driven

A

chain or gear from the crankshaft

106
Q

The main stop valve is this type of valve

A

globe or parallel sliding gate

107
Q

These governors are used on constant speed turbines

A

Mechanical

108
Q

This compressor produces shock waves

A

Radial-centrifugal flow

109
Q

Four styles of combustors

A

cannular, annular, can (most used), straight through

110
Q

two ways of injecting fuel into gas turbine

A

atomizer (most common)

vaporizing

Millwright Level 4 (5 decks)

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