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Aircraft Powerplants > Chapter 1 > Flashcards

Chapter 1 Flashcards

1
Q

The working theory of a gas turbine engine is according to

A

Newton’s 3rd law

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2
Q

The thrust force generated is according to

A

Newton’s 2nd law

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3
Q

The compressor in a running gas turbine engine is turned by the

A

Compressor turbine

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4
Q

What is thrust?

What is generated by?

How is it generated?

A

the force that propels an object in one direction

the force generated by the engine to propel the aircraft forward

thrust is generated through the reaction of the accelerating mass of air

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5
Q

What are the main modules of a gas turbine engine?

A

Inlet

Compressor

Combustion Chamber

Turbine

Exhaust

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6
Q

What are the main functions of a compressor in a gas turbine engine?

A

add energy to the gas

increase the pressure of the gas

increase the temperature of the gas

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7
Q

What are the main functions of the combustion chamber?

A

add energy to the gas

increase the velocity of the gas

increase the temperature of the gas

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8
Q

What turns the turbine in a gas turbine engine?

A

the hot air from the combustion chamber

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9
Q

What can be said about the pressure of the gas in the combustion chamber?

A

pressure is constant in the combustion chamber

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10
Q

What are the main functions of the turbine in a gas turbine engine?

A

The turbine extracts energy from the hot gases exiting the combustion chamber.

The turbine will then turn the compressor

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11
Q

What can be said about the gas’s velocity, temperature, and pressure at the turbine stage of the gas turbine engine?

A

velocity increases

temperature and pressure decreases

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12
Q

What happens at the exhaust of a gas turbine engine?

A

the remaining air that exits the exhaust will produce thrust

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13
Q

What equation can be to explain the effects of a convergent/divergent passage at subsonic flow?

A

mass flow rate equation

mass flow rate = density x area x velocity

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14
Q

In a convergent passage at supersonic airflow, what can be said about the changes in velocity and pressure?

A

velocity decrease

pressure increase

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15
Q

In a divergent passage at supersonic airflow, what can be said about the changes in velocity and pressure?

A

velocity increase

pressure decrease

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16
Q

Which part of the engine is where the pressure is the highest?

A

combustion chamber/compressor outlet

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17
Q

which part of the engine holds the highest temperature?

A

the turbine inlet temperature

18
Q

which part of the engine is the highest stress region in terms of temperature and pressure?

A

turbine inlet temperature

19
Q

what are the two types of thrust producing gas turbine engines?

A

turbojet engine

turbofan engine

20
Q

what are the two types of torque producing gas turbine engines?

A

turbo-shaft engine

turboprop engine

21
Q

how do turbojet engines produce thrust?

A

by accelerating a small mass of air to a very high velocity to product thrust

22
Q

how do turboprop engines produce thrust?

A

by giving a small acceleration to a big mass of air to produce thrust

23
Q

Why is a reduction gearbox needed in a turboprop engine?

A

the propeller in a turboprop engine needs to rotate at a lower RPM than the turbine, thus a reduction gearbox is used. This is to ensure the velocity does not exceed M1.0 to prevent the blade from stalling.

24
Q

a free turbine is a turbine that is?

A

A free turbine is not mechanically connected with the compressor

25
Q

what is meant by a 3 stage axial flow compressor?

A

the compressor has 3 stages.

Axial means the air goes in and comes out linearly, in the same direction

26
Q

what is meant by a centrifugal compressor?

A

it is a compressor whereby :

air goes in linearly

air goes out diagonally usually at a 90 degree angle

27
Q

What is the airworthiness standard chapter for aircraft engine in FAR

A

FAR Part 33

28
Q

describe an air-breathing gas turbine engine

A

an engine that uses atmospheric air as a working fluid

29
Q

What is inlet momentum drag (ram drag)?

A

inlet momentum drag (ram drag) is the difference between gross thrust and net thrust

30
Q

What causes inlet momentum drag(ram drag)?

A
  • inlet momentum drag(ram drag) is caused by the momentum of the mass of air entering the engine inlet
  • inlet momentum drag(ram drag) is caused by the increasing speed of air that enters the engine inlet
31
Q

inlet momentum drag(ram drag) causes ?

A

reduced thrust

32
Q

For aviation applications, turboshaft engines are only used on?

A

APU & helicopters

33
Q

What is the main purpose of the turbofan engine?

A

to turn the fan.

34
Q

Compare the propulsive efficiency of turbojet turboprop and turbofan engines

A
  1. turbojet engines have low propulsive efficiency at low altitudes and low airspeed. its propulsive efficiency will increase with an increase in altitude and airspeed because it is best used at high altitude and high airspeed
  2. turboprop engines have high propulsive efficiency at low altitudes and low airspeed. Its propulsive efficiency will decrease rapidly with an increase in altitude and airspeed
  3. turbofan engines have low propulsive efficiency at low altitudes and low airspeed. Its propulsive efficiency will increase with an increase in altitude and airspeed up to sonic speed
35
Q

compare the thrust-specific fuel consumption (TSFC) of turbojet, turboprop, and turbofan engines.

A
  1. turbojet engines have relatively high TSFC at low altitudes and low airspeed however its TSFC will decrease with an increase in altitude and airspeed.
  2. turboprop engines have low TSFC at low altitudes and low airspeed however its TSFC will increase with an increase in altitude and airspeed.
  3. the TSFC of a turbofan engine falls in between a turbojet engine and a turboprop engine.
36
Q

compare the takeoff roll between turbojet engine and turboprop engine

A

turbojet engine requires a longer takeoff roll

turboprop engine requires a shorter takeoff roll

37
Q

compare the frontal area between turbojet and turboprop engines

A

turbojet - smaller frontal area, reduced ground clearance issues

turboprop - large frontal area, requires longer landing gear

38
Q

describe propulsive efficiency

A

it refers to the fuel consumption vs thrust produced by the engine

39
Q

what is (TSFC)?

A

It refers to thrust-specific fuel consumption. it measures the fuel efficiency of an engine design with respect to its thrust output.

LOW TSFC = high efficiency

HIGH TSFC = low efficiency

40
Q

What are the advantages of a gas turbine engine over a reciprocating engine?

V.F.F.L.A.S.H.

A

Very High power to weight ratio

far less vibration

fewer moving parts

low lubricating oil cost and consumption

ability to generate higher thrust

smaller in size

high operation speeds

41
Q

what are the disadvantages of gas turbine engines compared to a reciprocating engine?

C.U.M.D.

A

Cost is much greater - stronger and more heat resistant materials required

usually less fuel-efficient, especially at idle

machining operations are more complex

delayed response to changes in power settings

Aircraft Powerplants (1 decks)

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