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TURBINE 360 > MOD 3-4 > Flashcards

MOD 3-4 Flashcards

1
Q

what is modular designed

A

The ability to replace parts of the engine.

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2
Q

where we convert the ram pressure to static pressure without loss of total pressure

A

Divergent duct

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3
Q

ram recovery point is?

A

when the pressure rise due to ram effect is going to increase the pressure at the face of the compressor is equal to the ambient pressure

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4
Q

what is duct pressure efficiency ratio?

A

ability of the duct to convert kinetic energy to potential energy (velocity to static pressure) whit out loss in total pressure.

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5
Q

which is considered the cold section of the engine ?

A

inlet and compressor

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6
Q

which is considered the hot section of the engine

A

when gases leave the diffuser combustion

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7
Q

purpose of the combustion section ?

A

place for mixing fuel and air for combustion, as well as mixing and expansion gases, full energy is converted to heat and velocity. Pressure held constant

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8
Q

performance requirements

A

-high combustion efficiency -stable -uniform temp distribution -easy starting -small -low smoke -low carbon

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9
Q

why the air velocity most be slow at the combustion section?

A

So that the flame is not moved toward the turbine (high ITT) or blown out completely (flame out)

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10
Q

what is flame out ?

A

is when the air is moving so fast that it blows out the flame

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11
Q

why the pressure must be constant on the combustion section ?

A

high pressure flows to low pressure so if there was a pressure rise it would cause a surge which would cause a stall

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12
Q

combustion section components

A

-case -perforated inner liner -fuel metering orifice -ignition source -drain

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13
Q

3 .types of combustion sections

A
  1. Can 2.Annular 3. Can-annular
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14
Q

what means reverse flow ?

A

air flow changes direction 2 times on the combustion section

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15
Q

can type advantages ?

A

-Each can, may be removed without separating the engine cases - Each can has it’s own fuel/air pattern control.

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16
Q

what is primary air

A

-25%-33% of air trough the engine -swirls upstream -low velocity (stabilization zone) -turbulence(just at the head of the combustion liner )

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17
Q

what is secondary air

A

67% to 75% of the air going through the engine • Dilution air – big holes • Cooling air – small holes • Film cooling • Cools the flame – is heated (energy transfer) • Presents a uniform flame front (temp. and press.) to the first stage turbine nozzle

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18
Q

What is an advantage of the modular design on a gas turbine engine?

A

Modules can be replaced individually. The engine is not required to be removed and sent to an overhaul shop for repair

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19
Q

What is the cross-sectional shape of an inlet duct?

A

Divergent

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20
Q

The inlet duct converts energy in the gas, causing the _____to decrease and the _____to increase

A

velocity, static pressure

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21
Q

One function of an inlet duct is to deliver and even ______ and _____ to the face of the compressor

A

pressure, velocity

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22
Q

The air pressure in the inlet duct at ram recovery point is the same as _____

A

Ambient pressure

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23
Q

If the duct pressure efficiency ratio is1:1 or 100%, the _____ will be the same at the inlet as it is at the outlet.

A

total pressure

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24
Q

The manufacturing and repair instructions for an inlet duct will is the responsibility of the _____ manufacturer

A

airframe

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25
Q

The bell mouth inlet duct is used primarily for _____

A

testing engines in a test cell

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26
Q

The air coming into the bell mouth inlet duct sees _____ % of the orifice/inlet size

A

100

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27
Q

In addition to having the same function as a sub-sonic inlet duct, the supersonic inlet duct has the additional function of _____.

A

Slowing the velocity of the air to sub-sonic speeds

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28
Q

The compressor is considered part of the _____ section

A

cold

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29
Q

On the Brayton Cycle graph, the compressor is described by line from point _____ to _____

A

A-B

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30
Q

If the engine has a low pressure compressor (N1) and a high pressure compressor (N2), which one is shown on the Brayton Cycle graph?

A

Line A to B represents all the compressors if there is more than one rotating group (N1 and N2)

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31
Q

List the 3 types of compressors

A

axial centrifugal axial-centrifugal

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32
Q

mayor parts of the compressor

A

impeller ,diffuser, manifold (The impeller is what puts energy (velocity) into the gas)

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33
Q

What are the 3 major parts of a centrifugal compressor?

A

Impeller•Diffuser•Manifold

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34
Q

List 2 advantages of a centrifugal compressor

A

Simplicity –easy to manufacture•Rugged (compared to axial compressor)•Low cost (relative)•Less FO

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35
Q

List 1 disadvantage of a centrifugal compressor

A

About 80% efficient•Limited stages (2)•Large frontal area

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36
Q

Why is there a limit of 2 stages of compression when using a centrifugal compressor?

A

Limited to 2 stages by the law of diminishing returns with more than 2 stages the loses will equal the gain

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37
Q

Why does the static pressure rise as the gasses travel through the centrifugal compressor impeller?

A

add velocity at the same time that is converting the velocity in static pressure

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38
Q

Indications of Stall

A

Vibration•Slow power lever response•Mild stall –no loud noises, maybe a rumbling sound•Explosive stall (loud bang) –can cause extensive damage

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39
Q

What are the 2 major parts of an axial compressor?

A

rotor(add energy and converts it) and stators (converts energy)

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40
Q

AoA is affected by ?

A

engine RPM air flow velocity FCU acceleration rate

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41
Q

The axial compressor is limited to a_____ compression ratio per stage. This happens when the compressor is running at the most efficient RPM it was designed to run. This is close to 100% RPM.

A

1.2:1

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42
Q

preventing stalls

A

lower angle of attack (derating the engine) use a bleed valve employ a two spool rotor variable IGV and variable vanes vary the exhaust nozzle size

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43
Q

what is flat rate ?

A

engine performance limit by thrust, the manufacture will determine that , because we don’t want to exceed ITT or RPM

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44
Q

what kind of performance limitations an engine has and must never exceed

A

-wheels speeds -Turbine temperature -torque or thrust for which the AC was certified (flat rate, airframe limitations)

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45
Q

What is Standard Day Barometric Pressure: _____ OAT: _____ Altitude: _____

A

29.92 inches of mercury 15 degrees Celsius at sea level

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46
Q

As temperature increases, density __________

A

decreases

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47
Q

As pressure decreases, density

A

decreases

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48
Q

In the stratosphere the temperature stabilizes at____ so even as altitude_____, the temperature does not change (assuming Standard Day)

A

-69.7˚F - increases

49
Q

The profile of the exhaust nozzle is a convergent duct so static pressure_____________________________

A

decreases and velocity increases

50
Q

As the subsonic gases exit the nozzle (convergent duct), the static pressure will___________________________ until sonic velocity is reached in the throat of the nozzle.

A

decrease and the velocity will increase

51
Q

As the subsonic gases exit the nozzle (convergent duct), the static pressure will___________________________ until sonic velocity is reached in the throat of the nozzle.

A

decrease and the velocity will increase

52
Q

on the thrust formula is the aircraft is not moving, nozzle not ___________

A

choked

53
Q

on the thrust formula is the aircraft is moving, nozzle is ___________

A

choked

54
Q

When is a nozzle considered a choked nozzle

A

As the subsonic gases exit the nozzle (convergent duct), the static pressure will decrease and the velocity will increase until sonic velocity is reached in the throat of the nozzle.

55
Q

How does atmospheric temperature affect thrust?

A

Higher density = higher mass airflow Lower density = lower mass airflow

56
Q

How does atmospheric pressure affect thrust?

A

As the pressure increases, the temperature increases reducing the density of air entering into the engine  thrust decreases

57
Q

Ram pressure_______ thrust, ram temperature _______ thrust

A

increases, decreases

58
Q

If the result of ram pressure rise is added to the ram temperature rise, the resultant is called the

A

ram effect

59
Q

Increase in altitude results in a decrease in ______________

A

temperature and pressure

60
Q

Why does the thrust decrease at a faster rate as aircraft altitude increases above 36, 089 ft?

A

because less density less drag

61
Q

Fg = Fr = Fn =

A

-gross thrust -ram drag - net thrust

62
Q

what is a RPM speed indication

A

eddy current, probe produces a magnetic field using aircraft electrical power, passing blade gear tooth disrupts the field magnetic lines of flux (phonetic wheel)

63
Q

how a monopole indicator works?

A

similar to eddy current has a permanent magnet instead to used the power of the aircraft

64
Q

what is a phonic wheel

A

is a gear that does not drive anything but gives us the pulse to a speed indication

65
Q

tachometer generator parts ?

A

-generator -driven from accessory drive -indicator -synchronous motor and flux coupling

66
Q

What is EPR ?

A

engine pressure ratio or tail pipe ratio is the ratio between Pt2 ( face of the compressor ) and Pt7 (pressure total tail pipe)

67
Q

what is IEPR

A

Integrated EPR average of fan exhaust pressure and gas generator gas pressure , divide by the Pt2

68
Q

exhaust section purpose

A

• Imparts a high exit velocity to the exhaust gases as they exit the engine • TF and TJ engines – Choked nozzle at high RPMs

69
Q

A convergent-divergent exhaust nozzle causes an increase in ______by increased acceleration of the exhaust gases.

A

Thrust

70
Q

Forces acting 90° to the walls of the duct resulting in the increase __________-

A

Thrust

71
Q

purpose of the nozzles of the Vectored Thrust

A

the four controlable nozzles allow the thrust produce by the turbo fan engine to vectored downward to takeoff and aft for forward flight

72
Q

name the parts of the exhaust

A

A.Exhaust cone

B. exhaust collector

C.strut

The exhaust collector bolts to the engine housing just aft of the turbine. The tail pipe bolts to the ring around the collector

73
Q

A convergent-divergent exhaust nozzle causes an increase in thrust by increased acceleration of the exhaust gases.

what is A, B and C

A

A. Subsonic convergent section

B.Supersonic Divergent Section

C. gas attains sonic velocity

74
Q

Characteristics of thrust reverses

A
  • For use on turbo jet and turbo fan engines
  • Deployed on the ground
  • Slow aircraft
  • Reduces wear on the brakes
  • Not always made by the engine manufacturer. Can be a 3rd party manufacturer but fitted to specific engines
75
Q

Thrust reversers types?

A

Pre-Exist

Post-Exist

76
Q

what kind of thrust reverser is this one ?

A

Pre- Exist

77
Q

what kind of trust reverse is this ?

A

Post-Exist

Target type

78
Q

what kind of thrust reverse is this?

A

A clamshell-type thrust reverser.

79
Q

what Reverser deploiment conditions have to be met in order to deploy thrust reversers?

A
  • Weight on landing gear (squat switch)
  • Power lever – idle
80
Q

Thrust Augmentation types

A
  • Afterburner – re-heat, Take-off or increased thrust requirement
  • Water or Water/methanol injection • Take-off only
81
Q

Characteristics Thrust augmentation afterburner

A

Add fuel after the last turbine • 300% increase in fuel burn – 50% increase in thrust • Works like a ram jet • Usually has a variable geometry exhaust nozzle • Open when accelerating to full power, then restricts to choke the nozzle after A/B initiated

82
Q

Thrust augmentation Water or Water/Methanol Injection characteristics

A

-Used for take-off only

  • Injected in the inlet, compressor, or diffuser
  • Methanol keeps water from freezing (if stored during flight)
  • Water only (consumed on take-off then remainder is jettisoned)
83
Q

On the Brayton Cycle graph, the exhaust section of a turbofan or turbojet engine is represented by a line that goes from point _____ to point _____

A

D TO E

84
Q

when we use Thrust augmentation ?

A

when we need a lot of performance and performance recovery (like hot day, not enough, density air is really low orwhen need to get to sonic velocity )

85
Q

Noise comes from the _____ and the ____

noise suppresion is done by ?

A

Inlet , exhaust

Fan Noise • Fan design can reduce noise • Inlet can be lined with sound absorbing material

• Exhaust noise • Reduce shear zone differential

86
Q

The cone that follows the last turbine, makes a _____ duct inside the exhaust duct.

A

divergent

87
Q

When is water or water/methanol used?

A

take off

88
Q

An afterburner thrust augmentation systems injects extra fuel. Where in the engine is the fuel added?

A

Add fuel after the last turbine

89
Q

How does a turbofan engine reduce the noise produced by the exhaust of the engine?

A
  • Fan design can reduce noise
  • Inlet can be lined with sound absorbing material
  • Reduce shear zone differential (exhaust)
90
Q

The turbine section of the engine is represented by a line from point _____ to point _____ of the Brayton Cycle graph.

A

C to D

91
Q

The profile shape of the turbine vane is a _____ duct.

A

convergent

92
Q

The purpose of the turbine vane is to increase _____ and decrease _____

A

velocity ,pressure

93
Q

The purpose of the turbine is to _____

A

extract energy to drive the compresor or in turbo prop/shaft to run the gearbox

94
Q

The combination type turbine blade has the _____ section at the tip and the _____ section at the root

A

reaction,impulse

reactio= extract velocity and pressure

Impulse = extracts velocity only

95
Q

If a turbine disk has 50 blades, and extracts 750 Hp out of the gasses, how much does each blade extract?

A

15 hp= (750/50)

96
Q

If there are 3 turbine disks, and they extract a total of 750 Hp out of the gasses, how much does each disk extract?

A

same amount each disk

97
Q

The _____ type of turbine shroud has the least amount of losses due to clearances

A

rotating (more mass, less losses)

98
Q

.Refer to the vector diagram that describes the velocity of the gasses at the root and the tip of the turbine blade, why is U for the root of the blade, less than U for the tip of the blade?

A

vane assembly converts more pressure to velocity at the root of the blade than at the tip.

99
Q

Turbine Engine Pneumatic Systems • Provide a source of air for:

A

– Cabin pressurization – Cabin heating and cooling – Engine and airframe anti-ice systems – Labyrinth seals – Internal cooling – Fuel control (FCU)

100
Q

Pneumatic System Operation

A

Shut-off valves control the extraction of bleed air from the compressor (this is a different valve from the compressor bleed valve that is used to prevent compressor stall.

101
Q

Oil Systems Purpose:

A

Supply oil under pressure to - clean - cool - lubricate

102
Q

Typical Oil System

A

Tank/sump/reservoir • Pump • Relief valve • Filter • Oil pressure indication • Nozzles and jets • Scavenge pump • Chip detector • Oil cooler • Tank/sump/reservoir

103
Q

purpouse Chip Detectors

A

Indicate when ferrous metal is present in the oil • Impending failure indicators - ΔP indicators – Button (usually red) pops out when a differential pressure across a filter exceeds a threshold pressure

104
Q

Starting Systems Purpose:

A

To accelerate the engine to the point where the turbine is producing enough power to continue the engine’s acceleration up to idle speed

105
Q

whats the Length of Start Cycle

A

Starter continues to accelerate the engine even after light off, until the engine has selfsustaining acceleration to idle • A “hot start” or a “hung start” could result if the starter is disengaged too soon or if the battery voltage is low (electric starter)

106
Q

Types of Starters

A

Electric motor • Electric motor/generator – Starter/generator • Pneumatic or air turbine • Gas turbine starter (small turboshaft that is used to start the bigger engine) • Hydraulic motor starter

107
Q

What is the purpose of a gearboxon a gas turbine engine?

A

Provide a place for mounting accessories for operation and control of the engine and airframe systems

108
Q

List 4 things that the pneumatic system provides air for.

A

Cabin pressurization – Cabin heating and cooling – Engine and airframe anti-ice systems – Labyrinth seals – Internal cooling – Fuel control (FCU)

109
Q

List the 2 types of spark igniters used in turbine engines

A

spark type

glow plug type

110
Q

What is the purpose of the engine oil system?

A

lubricate

cool down

clean

111
Q

In a typical engine oil system, what is the component that follows next in line to the scavenge pump(s)?

A
112
Q

What component protects the engine from oil starvation, if the oil filter completely plugs?

A

bypass valve

113
Q

A labyrinth seal has oil pressure on one side and air pressure on the other. Which pressure is higher? Why?

A

air pressure is higher and hight pressure follows low pressure keeping the oil on the other side

114
Q

What is the purpose of a chip detector in an engine oil system?

A

detect any ferrous material

115
Q

.What could cause a “hung” start?

A

if we turn off the starter too soon before gets to the sustaineble acceleration we can get a hung start, fire addinf fuel but the engine is not acceleration

116
Q

.What does self-sustaining acceleration mean?

A

when the engine is capable to mantain idle accelation

117
Q

.What is the difference in the drive mechanism for a starter motor, and a starter/generator?

A
118
Q

3.How many amps of power would a pneumatic starter draw when it is initially engaged?

A

1500 amps

TURBINE 360 (3 decks)

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