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Gas Turbine Engines > Part 1 - Fundamentals > Flashcards

Part 1 - Fundamentals Flashcards

1
Q

what does the adiabatic process mean?

A
  • expansion or contraction is adiabatic when

- no loss or gain of heat by the working fluid

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2
Q

what does the isothermal process mean?

A
  • expansion or contraction is isothermal when
  • the condition of the gas is changed at constant temperature
  • heat is gained or lost
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3
Q

what is momentum thrust?

A

thrust due to the change of momentum of the gases through the engine

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4
Q

what is pressure thrust?

A

thrust produced by a choked nozzle condition causing a pressure difference across the nozzle

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5
Q

what is gross thrust?

A
  • thrust produced by the total work done on the gas stream
  • is a combination of momentum thrust and pressure thrust
  • i.e. momentum thrust + pressure thrust = gross thrust
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6
Q

what is momentum or intake drag?

A

drag due to the momentum of the air passing into the engine relative to aircraft speed

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7
Q

what is net thrust?

A

gross thrust minus momentum drag

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8
Q

what is ram ratio?

A

the ratio of engine intake pressure to static pressure at the aircraft intake

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9
Q

what is total head pressure?

A
  • pressure of the air when brought to rest ahead of the intake supersonic flow
  • compressor inlet pressure should be as near as possible to total pressure
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10
Q

what is effect of humidity?

A
  • humid air will give less thrust
  • water vapour less dense than air
  • therefore weight of air entering engine is less
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11
Q

what is compressor efficiency?

A
  • determined by temperature rise through the compressor

- large temperature increase could indicate an inefficient compressor

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12
Q

what is a plenum chamber?

A
  • chamber or enlargement of a duct in an air intake system
  • used to smooth or dampen out pulsations in a flow of air
  • so that the air is supplied at a constant value
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13
Q

what is a power turbine?

A
  • sometimes referred to as a free turbine

- a turbine assembly not mechanically connected to a compressor

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14
Q

definition of mass

A
  • basic property of matter
  • generally associated with force required to overcome inertia of a body
  • called weight when that inertia is associated with gravity
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15
Q

definition of acceleration

A

rate of change of velocity of a body

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16
Q

definition of momentum

A
  • measure of quantity of motion
  • product of mass and velocity on a body
  • determined by length of time a constant force must act on that body to bring it to rest
  • momentum is a vector quantity and is parallel to the velocity vector
  • loosely speaking, momentum is the force built up by a moving body
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17
Q

definition of power

A
  • rate of charging energy from one form to another or the rate of doing work
  • power = energy/time
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18
Q

SI units of power

A

watts (W) or Joules per second (J/s)

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19
Q

Boyle’s law

A
  • volume of a given mass of gas
  • whose temperature is maintained constant
  • is inversely proportional to the gas pressure
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20
Q

Charles’ law

A
  • if the pressure of a given mass of gas is maintained constant
  • the volume of gas increases as its temperature is increased
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21
Q

what is the ideal gas law?

A

P1V1/T1 = P2V2/T2

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22
Q

effect of adding heat energy at a constant volume

A
  • increase in pressure

- this condition exists in a piston engine

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23
Q

effect of adding heat energy at a constant pressure

A
  • increase in volume

- this condition exists in a gas turbine engine

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24
Q

energy cannot be…

A

created nor destroyed

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25
Q

what is entropy?

A

flow of energy to an even level

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26
Q

what are six forms of energy?

A
  • heat
  • fuel
  • kinetic
  • potential
  • electrical
  • pressure
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27
Q

heat energy is regarded as __________ energy

A

heat energy is regarded as DISORDERLY energy

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28
Q

heat energy travels through which three methods?

A
  • convection
  • conduction
  • radiation
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29
Q

fuel energy is also known as _________ energy

A

fuel energy is also known as CHEMICAL energy

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30
Q

fuel energy is regarded as _________ energy

A

fuel energy is regarded as ORDERLY energy

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31
Q

kinetic energy is the energy a body possesses by virtue of its _______

A

kinetic energy is the energy a body possesses by virtue of its MOTION

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32
Q

potential energy is energy caused by the _________ of a body

A

potential energy is energy caused by the POSITION of a body

33
Q

electrical energy is the flow of atoms from a ________ charge to a ________ charge

A

electrical energy is the flow of atoms from a NEGATIVE charge to a POSITIVE charge

34
Q

pressure energy; a fluid under compression will attempt to flow from a ____ pressure to a ___ pressure and, in doing so, will or can do _____

A

pressure energy; a fluid under compression will attempt to flow from a HIGH pressure to a LOW pressure and, in doing so, will or can do WORK

35
Q

a thermodynamic engine is a machine where ____ energy is changed into work

A

a thermodynamic engine is a machine where HEAT energy is changed into work

36
Q

a thermodynamic engine is NEVER ___% efficient

A

a thermodynamic engine is NEVER 100% efficient

37
Q

in temperature scales:

  • C = ?
  • F = ?
  • K = ?
  • R = ?
A

in temperature scales:

  • C = CELSIUS
  • F = FAHRENHEIT
  • K = KELVIN
  • R = RANKINE
38
Q

rankine = fahrenheit + ___

A

rankine = fahrenheit + 460

39
Q

kelvin = celsius + ___

A

kelvin = celsius + 273

40
Q

fahrenheit = (9/5 celsius) + __

A

fahrenheit = (9/5 celsius) + 32

41
Q

celsius = 5/9 (Fahrenheit - __)

A

celsius = 5/9 (Fahrenheit - 32)

42
Q

what is newtons first law?

A

a body at rest will remain at rest…

43
Q

what is newtons second law?

A

rate of change of momentum of a body is proportional to the size of force and acts in direction of applied force

44
Q

what is newtons third law?

A

every action has an equal and opposite reaction

45
Q

what does Bernoulli’s theorem state?

A

energy can’t be created or destroyed

46
Q

what happens to pressure, temperature and velocity in a convergent duct?

A
  • pressure decreases
  • temperature decreases
  • velocity increases
47
Q

what happens to pressure, temperature and velocity in a divergent duct?

A
  • pressure increases
  • temperature increases
  • velocity decreases
48
Q

with a piston engine, combustion (power) is __________, whereas in the gas turbine, each process is __________

A

with a piston engine, combustion (power) is INTERMITTENT, whereas in the gas turbine, each process is CONTINUOUS

49
Q

in a gas turbine system, combustion takes place at a constant ________

A

in a gas turbine system, combustion takes place at a constant PRESSURE

50
Q

gas turbine engine fuel is ________ and less _________ than piston engine fuel

A

gas turbine engine fuel is CHEAPER and less DANGEROUS than piston engine fuel

51
Q

the power to weight ratio of the average turbo propeller engine is ______ times better than its equivalent piston engine; there is ________ frontal area; the efficiency is ________

A

the power to weight ratio of the average turbo propeller engine is THREE times better than its equivalent piston engine; there is REDUCED frontal area; the efficiency is SUPERIOR

52
Q

thrust in a gas turbine engine is felt on…

A

all static and rotating components

53
Q

the compressor provides mass ____ and at the same time increases its ________

A

the compressor provides mass FLOW and at the same time increases its PRESSURE

54
Q

the combustion system is designed to burn the fuel as efficiently as possible over the whole range of engine _________ conditions. it must do so without any increase in _________

A

the combustion system is designed to burn the fuel as efficiently as possible over the whole range of engine OPERATING conditions. it must do so without any increase in PRESSURE

55
Q

what is a disadvantage of single spooled engines?

A

single, heavier spools taking too long to accelerate (spool up)

56
Q

the high bypass turbofan engine is essentially a fix-______, multi-_______, ducted _________

A

the high bypass turbofan engine is essentially a fix-PITCHED, multi-BLADED, ducted PROPELLER

57
Q

high bypass engine ratios range from 1:1 to .:1

A

high bypass engine ratios range from 1:1 to 6.5:1

58
Q

the weight reduction on a typical low by-pass engine over a pure jet of similar mass flow is around __%

A

the weight reduction on a typical low by-pass engine over a pure jet of similar mass flow is around 20%

59
Q

on most modern turboprop engines, the amount of energy available for jet thrust is approximately __% at sea level

A

on most modern turboprop engines, the amount of energy available for jet thrust is approximately 10% at sea level

60
Q

a turbo prop usually has ____ stages than a turbo-jet engine

A

a turbo prop usually has MORE stages than a turbo-jet engine

61
Q

what is meant by a “free turbine”?

A
  • drive with no mechanical linkage to the “core engine”

- separate turbine drives shaft, driven by hot gases

62
Q

the majority of turbo prop engines are now “____ turbines”

A

the majority of turbo prop engines are now “FREE TURBINES”

63
Q

with respect to engine notations, what temperatures, pressures and speeds are the following referring to:

  • P0, T0?
  • P1, T1?
  • P2, T2?
  • P3, T3?
  • P4, T4?
  • P5, T5?
  • P6, T6?
  • P7, T7?
  • N1, N2 AND N3?
A

with respect to engine notations, what temperatures, pressures and speeds are the following referring to:

  • P0, T0 = ambient pressure and temperature
  • P1, T1 = compressor inlet P&T
  • P2, T2 = LP compressor delivery P&T
  • P3, T3 = HP compressor P%T
  • P4, T4 = turbine entry P&T
  • P5, T5 = HP turbine outlet P&T
  • P6, T6 = LP turbine outlet P&T
  • P7, T7 = exhaust P&T
  • N1, N2 AND N3 = LP, IP and HP spool speeds
64
Q

installed turbine engines which are out of use for up to _____ days require no special protection aside from _________ off apertures to prevent moisture/FOD ingress

A

installed turbine engines which are out of use for up to SEVEN days require no special protection aside from BLANKING off apertures to prevent moisture/FOD ingress

65
Q

short term engine storage is regarded as periods up to ___ month

A

short term engine storage is regarded as periods up to ONE month

66
Q

with regards to fuel systems, oil systems and external treatment, what must be done to satisfactorily store an engine on a short term basis?

A
  • fuel system - inhibited to prevent corrosion depending on whether installed or not
  • oil system - WRT maintenance manual, remove and clean filters or fill system to normal level with clean system or storage oil
  • external treatment - clean, dry with compressed air and inspect for corrosion and treat corrosion if necessary. desiccant or vapour phase inhibitor should be placed in intake. blank off engine
67
Q

long term engine storage is regarded as periods up to ___ months. after a six month storage period, the engine should be re-________ for a further six months if necessary. alternatively, the engine can be removed from the aircraft and placed in a _______ _______ ______ (MVP) bag

A

long term engine storage is regarded as periods up to SIX months. after a six month storage period, the engine should be re-PRESERVED for a further six months if necessary. alternatively, the engine can be removed from the aircraft and placed in a MOISTURE VAPOUR PROOF (MVP) bag

68
Q

for long term storage, in addition to measures taken for short term storage, the following action should be taken:

  • _______ all control rods and fittings
  • ______ off all vents and apertures on the engine, and, after covering ______ parts with greaseproof paper, spray a thin coat of preservative over the whole engine _______ of the exhaust
A

for long term storage, in addition to measures taken for short term storage, the following action should be taken:

  • GREASE all control rods and fittings
  • BLANK off all vents and apertures on the engine, and, after covering RUBBER parts with greaseproof paper, spray a thin coat of preservative over the whole engine FORWARD of the exhaust
69
Q

why is fuel system inhibiting carried out in stored engines?

A

fuel contains water which can cause corrosion

70
Q

briefly explain motoring method of fuel system inhibiting

A
  • used on installed engines where engine can be turned through normal trying system
  • header tank supplies oil to engine, connected to LP fuel inlet, LP cock should be closed
  • after draining engine fuel filter, motoring run should be carried out, bleeding the HP pump and FCU and operating HP cock several times whilst engine turning
  • neat inhibiting oil will eventually be discharged through combustion chamber drains
  • seal off apertures after motoring run
71
Q

when should gravity fuel system inhibiting be carried out?

A
  • only when motor driven rig not available

- gravity fed results less effective

72
Q

what does a motor driven fuel system inhibiting rig consist of?

A
  • tank capacity of at least 5 imperial gallons
  • motor driven had pump capable of 2gpm at 300 psi
  • 500 psi pressure gauge
  • filter
73
Q

what does a gravity feed fuel system inhibiting rig consist of?

A
  • tank capacity of at least 5 imp gallons
  • mounted at least 3ft above highest point in fuel system
  • pipe of 1” bore fitted with shut off cock
  • filter
74
Q

briefly explain pressure rig method of fuel system inhibiting

A
  • installed or uninstalled engines
  • pressure rig circulates oil through system at high pressure
  • drain fuel filter and LP cock closed
  • inlet and outlet connected to HP fuel pump pressure tapping and system LP inlet
  • bleed components and operate HP cock several times whilst oil flowing
  • neat inhibiting oil will eventually be discharged through combustion chamber drains
  • seal off apertures
75
Q

briefly explain gravity method of fuel system inhibiting

A
  • used when engine cannot be turned
  • connected to HP pump pressure line, FCU pressure line, burner manifold and LP inlet pipe
  • neat oil should run from components
  • blank off
76
Q

when storing fuel system components, they should be ________ as soon as possible prevent internal corrosion

A

when storing fuel system components, they should be INHIBITED as soon as possible prevent internal corrosion

77
Q

indicator paper accompanying engines stored and wrapped in ___________ sealed bags should be _____ when not contaminated and ____ if contaminated

A

indicator paper accompanying engines stored and wrapped in HERMETICALLY sealed bags should be BLUE when not contaminated and PINK if contaminated

78
Q

engines stored on a long term basis should be mounted on __________ stands, with associated _________ and information. if the engine has been removed because of failure, ______ from filters, _______ blades, or other evidence should also be packed for examination during overhaul

A

engines stored on a long term basis should be mounted on TRANSPORTATION stands, with associated DOCUMENTS and information. if the engine has been removed because of failure, METAL from filters, BROKEN blades, or other evidence should also be packed for examination during overhaul

79
Q

components should be stored in conditions which are dry and free from _________ fumes

shafts of fuel ______ and _____ flow regulators should be turned and part checked for satisfactory ___________ state

when life-ex, components should be subjected to ________ or testing IAW manufacturers instructions

A

components should be stored in conditions which are dry and free from CORROSIVE fumes

shafts of fuel PUMPS and FUEL flow regulators should be turned and part checked for satisfactory MODIFICATION state

when life-ex, components should be subjected to OVERHAUL or testing IAW manufacturers instructions

Gas Turbine Engines (36 decks)

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