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Diesel > MIDTERM REVIEW > Flashcards

MIDTERM REVIEW Flashcards

1
Q

What is velocity?

A

The distance traveled by a moving point in a unit of time.

Velocity = distance/time

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2
Q

What is acceleration?

A

Change in the velocity of a moving body within a unit of time

Acceleration = change in velocity/time taken

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3
Q

What is pressure?

A

Force acting on a unit of area

Pressure = force/area

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4
Q

What is specific gravity?

A

The ratio of:

the weight of a certain volume of a liquid

to the weight of an equal volume of water

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5
Q

What is work?

A

Work is done when a force is moving a body through a certain distance

Work = force X distance

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6
Q

What is power?

A

The rate at which work is performed

Power = work/time

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7
Q

What is horsepower?

A

The rate at which work is done

1 hp equals 33,000 foot – pounds of work per minute

Hp = (force x velocity) / 33,000

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8
Q

What is brake horsepower?

A

The maximum power generated by an engine at a given RPM, as determined by the engine manufacturer

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9
Q

What is shaft horsepower?

A

The power delivered along the shaft to the propeller at a given rpm

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10
Q

What is effective horsepower?

A

The power required to overcome a vessels total resistance at a given speed, not including the power required to turn the propeller or operate any machinery

(This is close to the power required to tow a vessel)

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11
Q

What is indicated horsepower?

A

Horse power of reciprocating engines, particularly in the larger sizes

It is determined from the pressure in the cylinders and is the power required to drive a ship at a given speed, including the power required to turn the propeller and to overcome any additional friction inherent in the system

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12
Q

What is gauge pressure?

PSIG

A

Pressures that are measured in respect to the pressure of atmospheric air

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13
Q

What is absolute pressure?

PSIA

A

The actual pressure exerted on the gas, obtained by adding of the barometric pressure to the gauge pressure

Absolute pressure = gauge pressure + barometric pressure

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14
Q

Is barometric pressure constant? What is standard barometric pressure at sea level?

A

Barometric pressure is not constant because it changes with altitude and weather

Standard barometric pressure at sea level is 29.92 inches of mercury, or 14.7 psia

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15
Q

What is kinetic energy?

A

The energy of movement

Some examples include: thermal energy, mechanical energy, electrical energy, and magnetic energy

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16
Q

What is potential energy?

A

Stored energy

Some examples include: chemical energy, elastic energy, nuclear energy, and gravitational energy

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17
Q

What is internal energy?

A

Energy stored within a body

It can be a gas, liquid, or solid

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18
Q

What is chemical energy?

A

Energy that is released when bonds formed in a chemical reaction, often producing heat as a byproduct

Examples include: batteries petroleum natural gas and coal are stored chemical energy

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19
Q

What is a British thermal unit (BTU)?

A

A measure of the heat content of fuels or other energy sources

The quantity of heat required to raise the temperature of 1 pound of liquid water by 1°F

1 pound of water = 1.0 BTU
1 gallon of water = 8.33 BTU
1 gallon of diesel = 137,452 BTU

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20
Q

What is conduction?

A

The transfer of energy by actual contact from one body to another

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21
Q

What is radiation?

A

Energy that is transferred through space

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22
Q

What is convection?

A

A process in which a body and the energy in it are moved from one position to another without change of state

Think of a tea kettle

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23
Q

What is specific heat?

A

The amount of heat it takes to raise 1 g of a substance by 1°C

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24
Q

What is a Diesel engine?

A

Reciprocating, compression ignition engines in which the fuel is ignited upon injection by the hot compressed charged air in the cylinder

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25
Q

What is the Otto cycle?

A

Spark ignition

Gasoline engines use spark plugs to ignite the fuel/air mixture

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26
Q

What kind of ignition will you find in a diesel cycle?

A

Compression ignition

Diesel engines use the heat of compressed air to ignite the fuel

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27
Q

What is an in-line diesel engine?

A

The in-line diesel engine is the simplest arrangement with all cylinders parallel and in line

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28
Q

What is a V type diesel engine?

A

The V-type engine, with two connecting rods attached to each crank pin, permits the entire length to be reduced by 1/2, thereby making it much more rigid

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29
Q

What do you call the rows of cylinders in a V type of engine?

A

Each row of cylinders is called a bank

A bank, B bank, etc.

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30
Q

What is an opposed piston engine?

A

two pistons and one combustion space in each cylinder.

The Pistons are arranged in opposed positions, crown to crown with the combustion space in between

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31
Q

What constitutes a slow speed engine?

A

100 to 150 RPM

propeller can be directly connected without need for reduction gear

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32
Q

What constitutes a medium speed engine?

A

300 to 1000 RPM

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33
Q

What constitutes a high-speed engine?

A

Greater than 1000 RPM

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34
Q

What is a four stroke engine?

A

Internal combustion engine that utilizes four distinct piston strokes to complete one operating cycle

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35
Q

What are the four strokes of a four stroke engine?

A

Intake

Compression

Power

Exhaust

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36
Q

The operating cycle of a four stroke engine requires how many revolutions of the crankshaft?

A

Two revolutions, or 720°

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37
Q

When does fuel injection start in a four stroke diesel engine?

A

Fuel injection starts just before the piston reaches top dead center

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38
Q

What is a two-stroke engine?

A

And internal combustion engine that utilizes two distinct piston strokes to complete one operating cycle

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39
Q

What are the two strokes of a two-stroke engine?

A

Compression and power

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40
Q

How many revolutions of the crankshaft are needed to complete one operating cycle of a two-stroke engine?

A

One revolution, or 360°

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41
Q

In a two-stroke engine, what events occur during the first stroke?

A

Compression and injection

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42
Q

In a two-stroke engine, what events occur during the second stroke?

A

Ignition and expansion/exhaust

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43
Q

What is a cetane number?

A

The rating of a diesel fuel’s quality of ignition

Actually a measure of the fuels ignition delay, or the time period between the start of injection and the start of combustion (ignition)

In general, I hire cetane fuel will have a shorter ignition delay than a lower cetane fuel

44
Q

Why is a higher cetane number better?

A

Shorter ignition delay

More complete combustion of fuel

Quicker starting

Quieter operation, less chatter

Improved fuel efficiency

A reduction of harmful emissions

45
Q

Why is a higher compression ratio better?

A

Higher thermal efficiency

Better fuel economy

46
Q

What is thermal efficiency?

A

The measure of an engine’s efficiency in converting heat energy contained within the liquid fuel into mechanical energy

Efficiency of: heat into mechanical energy

47
Q

What is the cylinder block?

A

The part of the engine frame which supports the engine cylinder liners and heads

48
Q

What is a crank case?

A

The part of the engine frame which houses the crankshaft

49
Q

What is a bedplate?

A

The bedplate supports the engine and ensures alignment of the shaft

The crank case provides housing for the crankshaft. In large engines, the crankcase and bedplate come in one piece

50
Q

What is the entablature?

A

A cylinder block which incorporates the scavenge airspace and the cooling water spaces

51
Q

What are tie rods?

A

Long, strong rods that hold the three major engine components in compression and transmit the firing load to the bed plate

The three major components being the cylinder block or entablature, the A-frame, and the crank case

52
Q

What are access covers?

A

They permit access to internal parts and spaces within the engine for inspection and maintenance

53
Q

What is an explosion cover, or safety cover, on a crank case?

A

Explosion covers relieve excessive pressure

54
Q

What is an anti-friction bearing?

A

Any bearing having the capability to reduce friction effectively

55
Q

What are cylinder liners?

A

Bores in which pistons move back-and-forth

Forms part of the combustion space

Replaceable

Wet and dry types

56
Q

What are dry type liners?

A

Coolant circulates within passages in the engine block and does NOT come in contact with the liner

Used on small engines

57
Q

What are wet type liners?

A

A water jacket is formed by the liner and a separate jacket fitted with an engine block or frame

Used on medium and low speed engines

58
Q

What is a cylinder head?

A

The space at the combustion chamber top is formed and sealed by a cylinder head

The cylinder head houses the intake and exhaust valves, the fuel injection valve, etc.

59
Q

What is a camshaft?

A

The camshaft is a shaft with eccentric projections, called cams

Designed to control the operation of valves

Provide proper firing order of the cylinders

60
Q

What are the functions of the cams on a camshaft?

A

The shape determines the point of opening and closing, the speed of opening and closing, and the amount of valve lift

61
Q

The camshaft is driven by _______.

A

The crankshaft

It is connected to the crankshaft most commonly by gears or a chain and sprocket

62
Q

How quickly must the camshaft rotate in a four stroke engine? In a two stroke?

A

Four stroke: 1/2 the crankshaft speed

Two-stroke: same speed as the crankshaft

63
Q

What kind of valves are used on the intake and exhaust ports?

A

Poppet valves

64
Q

What is characteristic of a poppet valve?

A

They have a beveled edges and seats, giving them a self centering action

65
Q

Intake valves are made of what kind of metal?

A

Low alloy steel, as intake valves are not subjected to hot exhaust gases

66
Q

Exhaust valves are usually made of what kind of metal?

A

Steel alloy to resist corrosion caused by high temperature gases

67
Q

What is the function of a rocker arm?

A

Rocker arms are part of the valve actuating mechanism

They put it on a pivot pin or shaft secured to a bracket mounted on the cylinder head

One end of a rocker arm contacts the top of the valve stem on the other end is actuated by the camshaft

68
Q

What is the function of a pushrod?

A

In installations wear the camshaft is located below the cylinder head, the rocker arms are actuated by pushrods

One rocker arm and a bridge maybe used to open two valves simultaneously

69
Q

What is the function of a cam follower?

A

Cam followers change the rotary motion of the camshaft to reciprocating motion this action opens the valves

Cam followers a ride to the flat of the cam

They rise and lower as the cam rotates

70
Q

What is the function of the lash adjuster?

A

Hydraulic valve lifters

Used on some engines to avoid the necessity of a clearance otherwise needed in the valve gear to allow for expansion resulting from temperature changes

71
Q

What is a piston?

A

A piston is one of the principal parts in the power transmitting assembly

Piston serve as the unit which transmits the force of combustion to the connecting rod

Pistons conduct the heat of combustion to the cylinder wall

72
Q

What are the three functions of piston rings?

A

Seal the cylinder

Distribute lubricating oil on the cylinder wall

Transfer heat from the piston to the cylinder wall

73
Q

What are the two general types of piston rings? What do they do?

A

Compression rings seal the cylinder and combustion space, preventing gases from escaping

Oil rings distribute lubricating oil on the cylinder wall to prevent metal to metal contact

74
Q

What is the function of the connecting rods?

A

The connecting rods transmit the firing force from the piston

Together with the crankshaft, connecting rods convert the reciprocating motion of the piston to a rotary motion on the crankshaft

75
Q

What is the function of the crankshaft?

A

The crankshaft converts the movement of the piston in and connecting rod into rotary motion

The rotary motion of the crankshaft drives reduction gears, the propeller shaft, generators and pumps

The crankshaft consists of a series of cranks or throws formed as offsets along a shaft

76
Q

What is the function of a flywheel?

A

A flywheel stores of energy during the power events and releases it during the remaining events of the operating cycle

When the speed of the shaft tends to increase the flywheel absorbs energy

When the speed it tends to decrease the flywheel gives up energy to the shaft in an effort to keep shaft rotation uniform

It limits the increase or decrease in speed during sudden changes of load

It aids in forcing the piston through the compression event when an engine is running at low or idling speed

It also helps to bring the engine up to speed when it is been cranked

77
Q

What is characteristic of a naturally aspirated engine?

A

The fuel/air mixture is forced into the cylinder by a vacuum

78
Q

What is the Venturi effect?

A

Air being drawn through a narrow valve opening is accelerated.

As the passage begins to widen again vacuum occurs.

79
Q

When comparing a naturally aspirated engine with a turbo charged or supercharged engine of the same displacement…

A

The naturally aspirated engine will generally give less power

80
Q

How does a turbocharger work?

A

Air is forced into the combustion chamber under a greater pressure

Exhaust gases from the engine drive the supercharger, hence no power is taken from the engine’s output

Sometimes referred to as centrifugal blowers

81
Q

How do superchargers work?

A

Air is forced into the combustion chamber under a greater pressure

Powered by the engine’s output

82
Q

What are three types of superchargers?

A

Roots type blower

Screw type

Centripetal

83
Q

What is a roots type blower?

A

A positive displacement air pump

The compression process is external to the blower

As the volume of air present in the intake manifold increases, the air pressure increases accordingly

84
Q

What is a screw type supercharger?

A

Relies on internal compression

Operates by pulling air through a pair of meshing lobes that resemble a set of worm gears

Air is trapped in pockets created by the lobes. As air pockets decrease in size, air moves from the fill side to the discharge side. Air pockets shrink and the air is squeezed into a smaller space

85
Q

What is a centrifugal type supercharger?

A

Similar in nature to a turbo charger, however, the centrifugal type supercharger is mechanically driven by the engine crankshaft rather than exhaust gases

86
Q

What are three types of air intake systems?

A

Dry type

Viscous type

Oil bath type

87
Q

What about silencers?

A

Silencers are generally constructed as part of the air cleaning components, preventing a high-pitched whistle

88
Q

What are the characteristics of a dry type cleaner and silencer?

A

Intake air is drawn through a fine mesh or screen which filters the air

89
Q

What are the characteristics of a viscous type cleaner and silencer?

A

Intake air is drawn through a fine mesh or screen which filters the air

The mesh is wet, usually with a medium weight oil

90
Q

What are the characteristics of oil bath type air filters?

A

Incoming air is forced or vertically down toward oil reservoir

Once the air reaches the oil it changes direction rapidly and is then forced back up to the engines intake system

The sluggish dirt particles cannot change direction as quickly and end up being trapped in the oil reservoir

91
Q

What is an intake manifold?

A

A passage through which air travels to reach the valves and combustion space of an engine

92
Q

In two-stroke engines, the passages that conducts intake air to the cylinders are generally referred to as an _______.

A

Air box.

93
Q

An airbox does what?

A

Surrounds the cylinders, is usually built into the block.

The passage that contacts intake air to the cylinders in two stroke engines

94
Q

The scavenging air passages in a Fairbanks Morse opposed piston engine are referred to as the _____.

A

Air receiver

95
Q

What is the single most common problem accelerating air system wear and failure?

A

Dust ingestion!

96
Q

What are some of the results of dust ingestion in an air system?

A

Accelerated abrasive where of piston rings and liners

Often caused by inlet leaks around flexible joints

May also be caused by defective or damaged air filters

Poor maintenance practices

97
Q

What are some other causes of air system wear and failure?

A

Plugged air filters

Turbo charger failures

Coolant to air leaks in the aftercooler

Hydraulic lock

98
Q

How does temperature affect air density?

A

Excessive temperatures lead to reduce air density and higher combustion temperatures

This can negatively affect torque, power and emissions

99
Q

What is the function of the heat exchanger?

A

To reduce the temperature of the charge air, cooling the air as it leaves the compressor

100
Q

What are three names for a heat exchanger?

A

Charge air cooler

Intercooler

After cooler

101
Q

What is the function of the exhaust system?

A

To carry away gases from the cylinders of an engine

muffle exhaustion noise

quench sparks

Remove solid material from exhaust gases

Furnish energy to a turbine driven supercharger

102
Q

What is the function of an exhaust manifold?

A

When the gases of combustion air force from the cylinders, they enter the exhaust manifold

103
Q

What is an open cooling system?

A

In an open system, the engine is cooled directly by seawater

Not used on most Marine Diesel engines

104
Q

What is a closed cooling system?

A

A closed cooling system is a freshwater circuit system that is self-contained and used continuously for the cooling of the engine

The cooling of a diesel engine is accomplished by the use of either a heat exchanger, Keel cooler, or radiator and fan

105
Q

What component is responsible for the cooling of an internal combustion engine? What are the four types?

A

Heat exchanger:

Keel coolers

Radiators and fans

Tube and shell type

Plate type

Diesel (2 decks)

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