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Aircraft System > fuels midterm > Flashcards

fuels midterm Flashcards

1
Q

The primary purpose of a ______ is to reduce friction between moving parts.

A

lubricant

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2
Q

In theory, ______ is based on the actual separation of the surfaces so that no metal-to-metal contact occurs.

A

fluid lubrication

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3
Q

As long as the ________remains unbroken, metallic friction is replaced by the internal fluid friction of the lubricant.

A

oil film

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4
Q

Under ideal conditions, friction and wear are held to a ________.

A

minimum

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5
Q

___ is generally pumped throughout the engine to all areas that require lubrication.

A

Oil

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6
Q

is created when a roller or sphere
rolls over another surface, such as with ball or roller bearings,

A

Rolling friction

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7
Q

also referred to as antifriction
bearings

A

Rolling friction

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8
Q

TYPES OF FRICTION

A

wiping friction, rolling friction

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9
Q

occurs between gear teeth

A

wiping friction

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10
Q

pressure can vary widely and loads applied to the gears can be extreme, so the lubricant must be able to withstand the loads.

A

wiping friction

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11
Q

acts as a cushion between metal parts.

A

oil film

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12
Q

In reciprocating engines, these components are
especially dependent on the oil for _______.

A

cooling

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13
Q

also aids in forming a seal between the piston and the cylinder wall to prevent leakage of the gases from the combustion chamber.

A

oil

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14
Q

can account for up to 50 percent of
the total engine cooling

A

oil cooling

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15
Q

clean the engine by reducing abrasive wear

A

oils

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16
Q

an additive that holds the
particles in suspension and allows the filter to trap them as the oil passes through the filter.

A

dispersant, an additive,

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17
Q

prevents corrosion on the interior of the engine by leaving a coating of oil on the parts
when the engine is shut down.

A

oil

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18
Q

Classifications lubricants according to physical state

A

LUBRICATING OILS
MINERAL OILS
SYNTHETIC OILS
ANIMAL AND VEGETABLE OIL
MINERAL OR PETROLEUM OIL
BLENDED OILS

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19
Q

sometimes simply called lubricant/lube, is a class of oils used to reduce the friction, heat, and wear between mechanical
components that are in contact with each other.

A

Lubricating oil,

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20
Q

used in motorized vehicles,
where it is known specifically as motor oil and
transmission fluid.

A

Lubricating oil

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21
Q

are lubricating oils refined from
naturally occurring crude oil

A

Mineral oils

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22
Q

currently the most
commonly used type because of the low cost of
extracting the oils from crude oil.

A

MINERAL OILS

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23
Q

can be manufactured
to have a varying viscosity, therefore making
them useful in a wide range of applications.

A

MINERAL OILS

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24
Q

are lubricating oils that are
manufactured.

A

SYNTHETIC OILS

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25
Q

used as a substitute for
petroleum-refined oils when operating in extreme
temperature.

A

SYNTHETIC OILS

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26
Q

Aircraft jet engines, for example, require the use
of ________, whereas aircraft piston engines
do not.

A

synthetic oils

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27
Q

GOOD LUBRICATING OIL MUST
POSSES

A

A low pressure ( high boiling point)

 Adequate viscosity for particular service condition

 Low freezing point

 High oxidation resistant

 Heat stability

 Non – corrosive properties

 Stability to decomposition at the operating temperature

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28
Q

were the most commonly used lubricants

They possess good
oiliness.

A

oil of vegetable and animal origins

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29
Q

can be used as an alternative fuel in
diesel engines and heating oil burners.

A

vegetable oil

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30
Q

When vegetable oil is used directly as a fuel, in
either modified or unmodified equipment, it is referred to as

A

straight vegetable oil (svo) or pure
plant oil (ppo)

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31
Q

can also be blended with
conventional diesel or processed into biodiesel or bioliquids for use under a wider range of conditions

A

Straight vegetable oil

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32
Q

they are used as a blending agent with other lubricating oil like mineral oils to produce desired effect in

A

animal and vegetable oil

33
Q

familiarize

ANIMAL AND VEGETABLE OIL
a) Costly
b) Undergo oxidation easy forming
gummy and acidic products and get
thickened on coming in contact with air.
c) Have some tendency to hydrolyze,
when allowed to remain contact with
moist air or aqueous medium.

A

ANIMAL AND VEGETABLE OIL
a) Costly
b) Undergo oxidation easy forming
gummy and acidic products and get
thickened on coming in contact with air.
c) Have some tendency to hydrolyze,
when allowed to remain contact with
moist air or aqueous medium.

34
Q

a liquid by-product of refining crude oil to make gasoline and other petroleum
products.

A

mineral oil

35
Q

a transparent,
colorless oil, composed mainly of
alkanes and cycloalkanes, related to
petroleum jelly.

A

MINERAL OR PETROLEUM OIL

36
Q

mineral or petroleum oil the most widely used lubricant, because they are:

A

Cheap

Available in
abundance

Quite stable under
service conditions.

37
Q

give desired lubricating properties,
required for particular machinery.

A

blended oils

38
Q

a) OILINESS-CARRIERS:

b) EXTREME-PRESSURE
ADDITIVES:

c) POUR-POINT:

d) ANTIOXIDANTS OR
INHIBITORS

e) CORROSION PREVENTERS

f) DEPOSIT INHIBITORS:

A

BLENDED OILS

39
Q

BLENDED OILS

A

a) OILINESS-CARRIERS:

b) EXTREME-PRESSURE
ADDITIVES:

c) POUR-POINT:

d) ANTIOXIDANTS OR
INHIBITORS

e) CORROSION PREVENTERS

f) DEPOSIT INHIBITORS:

40
Q

have higher shear or frictional resistance than oils and, therefore, can support much heavier loads at lower speeds. They also do not require as much attention unlike the lubricating liquids. But have a tendency to separate into oils and soaps.

A

greases or semi solid

41
Q

Grease are used:

A

In situations where oil cannot remain in place, due to high load, low speed,
intermittent operation etc.

In bearing and gears that work at high temperatures

In situations where bearing needs to be sealed against entry of dust, dirt, grit or
moisture, because greases are less liable to contamination.

Dripping or spurting of oil is undesirable,

42
Q

are materials that,
despite being in the solid phase, are
able to reduce friction between two
surfaces sliding against each other
without the need for a liquid oil
medium.

A

SOLID LUBRICANTS

43
Q

The four most commonly used solid lubricants are:

A

Graphite

Molybdenum disulfide

Hexagonal boron
nitride

Tungsten disulfide

44
Q

The two main dry lubricants are _______ and _______. They
offer lubrication at temperatures higher than liquid and oil-based lubricants operate. Dry lubricants are often used in applications such as locks or dry lubricated bearings.

A

graphite and molybdenum disulfide

45
Q

Solid lubricants are useful for conditions when conventional lubricants are inadequate, such as:

A

Reciprocating motion:
Ceramics:
High temperature:
Extreme contact pressures:

46
Q

a lubricant consisting of
chemical compounds that are
artificially made.

A

synthetic oil

47
Q

Modern synthetic lubricants possess, in general, the following distinguishing characteristics:

A

 non-inflammable

 high flash points

 high thermal stability at high operating temperatures

 high viscosity-index

 chemical stability

48
Q

FUNCTIONS OF LUBRICANT

A

Lubricant vs. anti-tack coating

Keep moving parts apart

Reduce friction

Transfer heat

Carry away contaminants and debris

Transmit power

Protect against wear

Prevent corrosion

49
Q

Lubricant vs. anti-tack coating

Keep moving parts apart

Reduce friction

Transfer heat

Carry away contaminants and debris

Transmit power

Protect against wear

Prevent corrosion

A

FUNCTIONS OF LUBRICANT

50
Q

are compounds that prevent crystallization
of waxes.

A

Pour point depressants

51
Q

ADDITIVES

A

Pour point depressants
Anti-foaming agents
Viscosity index improvers (VIIs)
Antioxidants
Detergents
Corrosion inhibitors (rust inhibitors)
Anti-wear additives
Extreme pressure (anti-scuffing)
additives
Friction modifiers

52
Q

are typically silicone compounds which
increase surface tension in order to
discourage foam formation.

A

Anti-foaming agents

53
Q

are compounds that allow lubricants to
remain viscous at higher temperatures.

A

Viscosity index improvers (VIIs)

54
Q

suppress the rate of oxidative degradation
of the hydrocarbon molecules within the
lubricant.

A

Antioxidants

55
Q

ensure the cleanliness of engine components by preventing the formation of deposits on
contact surfaces at high temperatures.

A

Detergents

56
Q

are usually alkaline materials, such as alkyl sulfonate salts, that absorb acids that would corrode metal parts.

A

Corrosion inhibitors (rust inhibitors)

57
Q

form protective ‘tribofilms’ on metal
parts, suppressing wear.

A

Anti-wear additives

58
Q

form protective films on
sliding metal parts.

A

Extreme pressure (anti-scuffing)
additives

59
Q

reduce friction and wear, particularly in the
boundary lubrication regime where
surfaces come into direct contact.

A

Friction modifiers

60
Q

Lubricants must have the following main characteristics:

A

 Keep surfaces separate under all loads, temperatures and speeds, thus minimizing
friction and wear.

 Act as a cooling fluid removing the heat produced by friction or from external
sources

 Remain adequately stable in order to guarantee constant behavior over the forecasted
useful life.

 Protect surfaces from the attack of aggressive products formed during operation.

 Show cleaning capability and dirt holding capacity in order to remove residue and
debris that may be form during operation.

61
Q

 Keep surfaces separate under all loads, temperatures and speeds, thus minimizing
friction and wear.

 Act as a cooling fluid removing the heat produced by friction or from external
sources

 Remain adequately stable in order to guarantee constant behavior over the forecasted
useful life.

 Protect surfaces from the attack of aggressive products formed during operation.

 Show cleaning capability and dirt holding capacity in order to remove residue and
debris that may be form during operation.

A

Lubricants must have the following main characteristics:

62
Q

The main properties of lubricants, which are usually indicated in the technical
characteristics of the product, are:

A

 Viscosity

 Viscosity index

 Pour point

 Flash point

63
Q

describes the flow behavior of a fluid.

A

viscosity

64
Q

measurement of viscosity

A

centistokes (cSt)

65
Q

viscosity of lubricating oils diminishes as temperature ____ and consequently is measured at a given temperature

A

rises

66
Q

when oil is heated its viscosity is _____ , this _____ its load carrying capacity.

A

reduced, reduces

67
Q

When temperature______, the lubricant
becomes thinner and the viscosity becomes
lower.

Inversely as the temperature ______, the
lubricant thickens and ______ increases,
making it more difficult to pour or pump.

A

increases, decreases, viscosity

68
Q

is a measurement of oil’s
viscosity change due to temperature.

A

Viscosity Index (VI)

69
Q

The higher the VI the less it will thicken when
cold, and the less it will thin out when heated.

A

viscosity

70
Q

familiarize

What causes viscosity to increase or
decrease increases may be caused but not
limited to oxidation, polymerization,
carbon build-up (Soot), contaminants,
anti-freeze, water ingress and/ or the
addition of a wrong oil type.

Decreases in viscosity could indicate fuel
dilution, sheer down of the VI, thermal
cracking, over extended oil drain periods
and again the addition of a wrong oil type.

A

familiarize

What causes viscosity to increase or
decrease increases may be caused but not
limited to oxidation, polymerization,
carbon build-up (Soot), contaminants,
anti-freeze, water ingress and/ or the
addition of a wrong oil type.

Decreases in viscosity could indicate fuel
dilution, sheer down of the VI, thermal
cracking, over extended oil drain periods
and again the addition of a wrong oil type.

71
Q

The_______ of a crude oil, or a petroleum fraction, is the lowest temperature at which the oil will
pour or flow when it is cooled, without stirring, under standard cooling conditions.

represents the lowest temperature at which oil is capable of flowing under gravity

A

pour point

72
Q

familiarize

The pour point of crude oils relates to their
paraffin content: the higher the paraffin content,
the higher the pour point.

To improve (reduce) the pour point of these oils,
pour point depressants (PPDs) are added.

A

familiarize

The pour point of crude oils relates to their
paraffin content: the higher the paraffin content,
the higher the pour point.

To improve (reduce) the pour point of these oils,
pour point depressants (PPDs) are added.

73
Q

is the minimum temperature at
which an oil-vapor-air-mixture becomes
inflammable.

It is determined by progressively heating the
oil-vapor-air-mixture in a standard laboratory
receptacle until the mixture ignites.

A

flash point

74
Q

is sometimes confused with the
autoignition temperature, the temperature that
causes spontaneous ignition.

A

flash point

75
Q

is the lowest temperature at which
the vapors keep burning after the ignition source
is removed.

A

fire point

76
Q

is a comparison of the weight of
the substance to the weight of an equal volume of
distilled water at a specified temperature.

A

specific gravity

77
Q

is often considered to be the life
blood of an engine.

Without it, the friction and wear produced
between moving parts would cause an engine to
wear at a very rapid rate.

A

lubricating oil

78
Q

FUNCTIONS OF LUBRICATING OIL

A

REDUCE FRICTION
ABSORBS HEAT
SEALS
CUSHIONS
CLEANS
PROTECTS AGAINST CORROSION

79
Q

CHEMICAL PROPERTIES OF
LUBRICATING OILS

A

Ease of starting rapidity of warming up

Low Carbon Forming Tendency

Carbon residue test methods

High Oxidation Stability

Wear Reduction

Abrasive wear

Corrosive wear

Adhesive wear

Detergency and Dispersancy

Seal compatibility

Aircraft System (11 decks)

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