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Resource Group Mod 15 2024 > 15.1 Fundamentals > Flashcards

15.1 Fundamentals Flashcards

1
Q

What is the definition of energy?

A

Something that gives a body the capacity to do work.

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2
Q

What is the unit of measurement for both ‘Work Done’ and Energy?

A

Joules (J)

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3
Q

What is the definition of Potential Energy?

A

The stored energy of a body at rest.

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4
Q

What are the 3 ways in which Potential Energy is generated?

A
  • Due to a body’s position (height).
  • Due to a body’s distortion (springs/Elastic tension).
  • Due to a chemical action (batteries).
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5
Q

Potential Energy equation?

A

PE = mgh (mass x gravity x height)

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6
Q

What is the definiton of Kinetic Energy?

A

The energy of a body in motion, converting it’s PE into work done.

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7
Q

Kinetic Energy Equation?

A

KE = ½mV² (0.5 x mass x Velocity²)

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8
Q

What is Newton’s first law?

A

Law of Inertia. (A body in motion stays in motion….).

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9
Q

What is Newton’s second law?

A

Law of Motion. (Force = Mass x Acceleration).

Applies to GTE as Thrust is proportional to mass of airflow multiplied by acceleration of airflow.

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10
Q

What is Newton’s third law?

A

Law of Action and Reaction. (Every action has an equal and opposite reaction…)

(Turbojet Engines)

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11
Q

What’s the Brayton Cycle in 4 simple stages?

A

Suck, Squeeze, Bang, Blow.

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12
Q

How do the 4 stages of the Brayton Cycle correlate to the stages of a GTE?

A

Intake = Suck.

Compressor = Squeeze.

Expansion/Combustion Chamber = Bang.

Exhaust = Blow.

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13
Q

What happens to the pressure and volume of air, in the compressor?

A

Air pressure increases greatly.
Air volume decreases.

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14
Q

What happens to the pressure and volume of air, in the combustion chamber?

A

Air pressure remains constant.
Air volume increases as it expands.

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15
Q

What happens to the pressure and volume of air, in the exhaust section?

A

Air pressure continues to decrease.
Air volume continues to expand.

It reaches the point of ‘final high velocity’ = Thrust.

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16
Q

What are the 4 ideal changes of state?

A

Isobaric.
Isochoric.
Isothermal.
Isoentropic.

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17
Q

Isobaric definition?

A

p = Constant

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18
Q

Isochoric definition?

A

v = constant

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19
Q

Isothermal definition?

A

t = constant

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20
Q

Isoentropic definition?

A

Heat is neither added nor rejected. (Adiabatic System).

Q = O

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21
Q

What type of heating is used in the combustion chamber?

A

Isobaric heating. (Heat is added to the air, as fuel is burned at a constant pressure)

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22
Q

Unit of measurement for Thrust?

A

lbs

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23
Q

Formula for Work?

A

Work = Force x Distance (Joules or Nm)

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24
Q

Formula for Power?

A

Power (Nm/s) = (Force x Distance) / Time

(Work over time)

25
Q

Definition of Velocity?

A

Speed with a direction, a ‘vector quantity’.

26
Q

Definition of Acceleration?

A

Rate of change of Velocity.

27
Q

Formula for Acceleration?

A

Accel (m/s)² = Change in velocity / time

28
Q

What is the basic operation of a Turbojet engine?

A

A turbine driven compressor draws the air in and compresses it, which enters the combustion chamber and is mixed with injected fuel. Explosion expands air and is exhausted via exhaust nozzles/jet.

29
Q

What are the advantages of a Turbojet?

A
  • Simple design.
  • Very high speeds.
  • Takes up little space.
30
Q

What are the disadvantages of a Turbojet?

A
  • High fuel consumption.
  • Loud.
  • Poor slow speed performance.
  • Limited range and endurance.
31
Q

What’s the difference between a twin-spool and triple-spool Turbofan engine?

A

The triple-spool engine adds an additonal turbine and compressor pair, as the ‘Intermediate Pressure’ (IP) section.

Twin-spool has just two turbine and compressor pairs, as the Low Pressure and High Pressure sections.

32
Q

What % of Thurst does the fan generate in a Turbofan engine?

A

Approx. 80%

33
Q

Advantanges of a Turbofan engine?

A
  • Fuel efficient.
  • Less noisy.
  • Streamlined appearance.
34
Q

Disadvantages of a Turbofan engine?

A
  • Heavy.
  • Larger frontal area.
  • Inefficient at very high altitudes.
35
Q

How does a turboprop engine operate compared to other engine types?

A

Operates in the same principles as a turbojet engine, but produce shaft horsepower to drive a propeller.

36
Q

What key mechanical parts are additional to a turboprop engine?

A

They have additional turbines, a power shaft, and a reduction gearbox.

37
Q

Advantages of a Turboprop?

A
  • Very fuel efficient.
  • Most efficient at mid-range speeds (250-400knts).
  • Most efficient at mid-range altitudes (18000-30000ft).
38
Q

Disadvantages of a Turboprop?

A
  • Limited airspeed.
  • Gearing systems are heavy, and can fail.
39
Q

What is the definition of a Turboshaft engine?

A

A gas turbine engine that delivers power through a shaft to operate something OTHER than a propeller.

40
Q

Where are turboshaft engines used?

A

As helicopter engines, and APUs.

41
Q

How do Turboshaft engines operate compared to other engine-types?

A

The same principles as a turbojet, but with an additional power section.

42
Q

How is the power turbine within a turboshaft engine usually described?

A

As a ‘Free Power Turbine’.

It’s not mechanically linked, and is only linked by the stream of hot gasses.

43
Q

What is the purpose of having a Free Power Turbine?

A

Allows its speed to be optimised for the machinery that it will energise. It does this without the need for a reduction gearbox.

44
Q

Advantages of a Turboshaft engine, compared to piston?

A
  • Much higher power to weight ratio than piston engines.
  • Typically smaller than piston engines.
45
Q

What are the two disadvantages of a Turboshaft engine? (one of these is the same as turboprops).

A
  • Loud.
  • Complex gear systems, they can fail.
46
Q

Which area of a GTE forms the cold section?

A

From the inlet, to the compressors and diffusers.

47
Q

Which area of a GTE forms the hot section?

A

From the combustion chambers to the exhaust.

48
Q

What is the greatest influencing factor for design?

A

The type of compressor that will be used.

49
Q

What are the advantages of Modular Construction, for the engine manafacturer?

A
  • Rotating parts can be pre-balanced.
  • Fewer spare engines needed in stock.
  • More flexibility with changing engine parts.
  • Modules are easily stored and transported.
50
Q

What are the advantages of Modular Construction, for the engine operator?

A
  • Modules easily removed/replaced with minimal disturbance to other components.
  • No re-balancing required after module changes.
  • Modules can be replaced in-situ.
  • Less need for spares.
  • Easily transported.
51
Q

What can a module replacement be classed as?

A

A ‘Minor Repair’ and thus can be carried out in an MRO, instead of sending the engine away for Overhaul.

52
Q

Where is Aluminium Alloy used?

A
  • Gearbox housings.
  • Fan stator casings.
  • Low loaded module parts.
53
Q

Where are composites used?

A
  • Fan blades.
  • Fan case.
54
Q

Where are Ceramics used?

A
  • Combustion chamber coastings.
  • High pressure turbine.
55
Q

Where are Steel Alloys used?

A
  • N1 shaft.
  • Engine bearings.
  • Main structural frames.
56
Q

Where are Cobalt-base alloys used?

A
  • High heat resistance areas.
  • 1st stage High Pressure turbine stators.
57
Q

Where are Titanium alloys used?

A
  • Fan.
  • LP compressor.
  • Front stages of HP compressor.

(Titanium has the same strength as steel, for half the weight).

58
Q

Where are Nickel-based alloys used?

A
  • High centrifugal loads at high temps.
  • HP compressor.
  • Combustion section.
  • HP and LP turbines.

Resource Group Mod 15 2024 (13 decks)

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