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Aircraft Propulsion > Chapter 3 Farokhi > Flashcards

Chapter 3 Farokhi Flashcards

1
Q

For a high bypass ratio turbofan.

What’s between station 0 and 2?

A

Inlet

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2
Q

For a high bypass ratio turbofan.

What’s between station 2.5 and 3 ?

A

HPC high pressure compressor

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3
Q

For a high bypass ratio turbofan.

What’s between station 3 and 4?

A

Combuster or burner

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4
Q

For a high bypass ratio turbofan.

What’s between station 4 and 4.5 ?

A

HPT high pressure turbine

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5
Q

For a high bypass ratio turbofan.

What’s between station 4.5 and 5 ?

A

LPT low pressure turbine

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6
Q

For a high bypass ratio turbofan.

What’s between station 2 and 2.5 ?

A

LPC low pressure compressor

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7
Q

For a turbojet with afterburner. What’s between station 0 and 2?

A

Inlet

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8
Q

For a turbojet with afterburner. What’s between station 2 and 2.5 ?

A

LPC low pressure compressor

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9
Q

For a turbojet with afterburner. What’s between station 2.5 and 3 ?

A

HPC high pressure compressor

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10
Q

For a turbojet with afterburner. What’s between station 3 and 4 ?

A

Combustor or burner

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11
Q

For a turbojet with afterburner. What’s between station 4 and 4.5 ?

A

HPT high pressure turbine

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12
Q

For a turbojet with afterburner. What’s between station 4.5 and 5 ?

A

LPT low pressure turbine

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13
Q

For a turbojet with afterburner. What’s between station 5 and 6 ?

A

Afterburner

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14
Q

For a turbojet with afterburner. What’s between station 7 and 9 ?

A

Nozzle

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15
Q

For a turbojet with afterburner. What’s on station 8 ?

A

Throat of the nozzle

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16
Q

A gas generator includes the following three for a jet engine.

A

Compressor 2->3
Combustion/burner 3->4
Turbine 4->5

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17
Q

Propulsive efficiency is defined as ?

A

n_p = F*V_o/DKEdot

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18
Q

At takeoff, the ______ is often ignored leading to a zero ram drag. F at take off is equal to F gross = (mA + mf)V9 + (p9-p0)A9

A

Airspeed Vo

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19
Q

When p9=p0 the nozzle is said to be ______ . Leading to the following equation for trust at takeoff:

A

Perfectly expanded nozzle

F=(ma+mf)V9

20
Q

In a turbofan engine, the captured airflow is typically divided into a _____ flow where the combustion takes place and a _____ flow, where the so called bypass steam of air is compressed through a fan and later expelled through a fan exhaust nozzle. This type of arrangement (bypass) configuration leads to a ______ overall efficiency of the engine and a lower fuel consumption.

A

Core flow
Bypass flow
Higher efficiency

21
Q

An example of an engine with more than a single stream is _____
With a more than one stream the Fnet uninstalled is the difference between____

A

Turbofan

Fnet = sum FgNozzles - sum DramInlets

22
Q

The engine uninstalled trust is the difference between which two contributions ?

A

Nozzle contribution and inlet contribution

23
Q

The nozzle contribution is called _______ . And is given by the formula Fg=(m+m)V9+ (P9-P0)A9

A

Gross trust

24
Q

The inlet contribution is negative and its called _____ D = mV0

A

Ram drag

25
Q

In turboprops and turboshaft engines thermal efficiency ignores and neglects the _______

A

Kinetic energy

26
Q

The ability to convert the thermal energy inherent to a net kinetic energy gain is known as ____

A

Thermal efficiency
Ratio of net mechanical output over thermal input

DKEdot/Pthermal

27
Q

All propulsiors, rockets, and air-breathers could be compared by using a unifying figure of merit, namely their specific impulses in seconds. Define specific impulse for both an air breather engine and rocket

A

Is = F/mf*g. Air breather

Is = F/mp*g. Rocket

28
Q

Name a few figures of merit when designing an engine.

A

Engine thrust
Mass flow rate
Mechanical power/shaft output

Dry weight

29
Q

In case of an air breathing engine, specific thrust is defined as ______

A

F/m ratio of thrust to air mass flow rate

Remember, we want to produce thrust with the least quantity of air mass flow rate

30
Q

Define specific thrust in nondimesional form

A

F/m*a

a = ambient speed of sound

31
Q

In the commercial world, perhaps the most important parameter of the engine is the _____

Where as for the military world are ______

A

Specific fuel consumption

Stealth, agility, maneuvered, survival

32
Q

For an air breathing engine TSFC is defined as:

A

mf/F

Ratio of fuel flow rate per unit thrust produce

33
Q

The reason why we can’t achieve 100% efficiency is because we can’t violate which law ?

A

2nd law thermodynamics

34
Q

F installed = ? - ?

A

F uninstalled- D nacelle

35
Q

The fraction of the net mechanical output(DKEdot) of the engine which is converted into thrust power(F*V) is called ______

A

Propulsive efficiency

n_p = F*V/DKEdot

36
Q

The engine internal thrust is:

Mv9-mv1+p9A9-p1A1

True or false

A

True

37
Q 
The axial components of force felt by the inner walls of an air breathing engine are : 
Fxcompressor = 
Fx burner = 
Fx turbine = 
Fx nozzle =
A

I2-I3
I3-I4
I4-I5
I5-I9

38
Q

Consider a rocket. In comparison to an air breathing engine the rocket system is missing the _____ .
Therefore, the inlet _____ contribution to thrust is also missing in the rocket thrust equation which is independent of the Vo flight speed.

A

Air intake

Inlet ram drag

39
Q

Installation losses to the thrust include the following 3

Accurate measurements of these drags require ____ analysis and _____ testing.

A

Nacelle skin friction
Pressure drags caused by engine installation

Pylon drag

CFD and WTT

40
Q

Additive drag minus the cowl lip force (suction force) is know as;

A

Spillage drag

41
Q

In the study of propulsion we often concentrate on the engine internal performance I.e. _______ rather than the _______ performance

A

Uninstalled

Installed

42
Q

If P9 < Po the nozzle is _____ which can happen in _____ jets only. These jets use large nozzles. These needs a ___ area ratio.

A

Over expanded
Supersonic
Large

43
Q

If P9=Po the nozzle is _____ which is the case for all _____ jets and sometimes in sonic or supersonic jets. This configuration needs the ____ nozzle area ratio.

A

Perfectly expanded
Subsonic
Right

44
Q

Is P9>Po the nozzle is _____ which can happen in _____ or _____ jets only.

A

Under expanded
Sonic
Supersonic

45
Q

In deriving the axial force thrust of an engine we have to use the ____ principals.

A

Momentum

Aircraft Propulsion (1 decks)

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