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Powerplants > Test 3 > Flashcards

Test 3 Flashcards

1
Q

Inlet Airduct

A
  • Is considered to be a part of the airframe
  • It is responsible for supplying a constant, undisturbed flow of subsonic air to the compressor

Two types:
- Subsonic inlet duct
- Usually is a divergent duct
- Supersonic inlet duct
- Usually is a convergent duct

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2
Q

Turboprop

A
  • Propeller reduction gearbox interferes w/ airflow

Ways to deliver air:
- Ducted spinner inlet
- Conical spinner inlet
- Under scoop inlet

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3
Q

Foreign Object Damage (FOD)

A

when something foreign enters the engine

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4
Q

Supersonic Inlet Duct

A
  • Airflow must be SOS entering the compressor so a convergent-divergent duct is used
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5
Q

Bernoulli’s equation at SOS

A

Bernoulli’s equation switches when going from subsonic to supersonic

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6
Q

Compressors

A

Two types:
- Axial flow
- Centrifugal

Compressors speed up air, not increase pressure

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7
Q

Axial Flow Compressors

A
  • Air passes straight through the compressor

Disadvantages
- Heavier than centrifugal
- Costly to manufacture

Advantages
- Higher overall compression ratio
- Easier to streamline

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8
Q

Centrifugal compressor

A

Advantages
- Rugged
- Lightweight
- Easier to manufacture
- High-pressure ratio for each stage of compression

Disadvantage
- Large diameter disk in back
- Tip speed increases and efficiency goes down
- Difficult to streamline

  • You can stack centrifugal compressors

Components:
- Impeller (part w/ all the fins)
- Diffusor (stator)
- Manifold

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9
Q

Rotor vs Stator blades

A

Rotor blades - blades that rotate in the compressor

Stator blades - blades that stay still

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10
Q

Types of Centrifugal Compressors

A

Double Entry
- Difficult to design inlet ducts for front and rear air supply

Multi-stage
- High pressure rise per stage

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11
Q

Types of Axial flow compressors

A
  • Single spool axial flow
  • Dual spool axial flow
  • Three spool axial flow
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12
Q

Single Spool Axial Flow

A
  • Limited in # of stages (# of disks)
    • Rearmost becomes inefficient
    • Front becomes overloaded
    • Airflow becomes restricted
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13
Q

Dual Spool Axial Flow

A
  • Rearmost compressor = High pressure Compressor (N2)
  • Driven by forward stage turbine (High-pressure turbine)
  • N2 compressor is governed by the fuel control and used by the starter to start the engine due to its lighter weight
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14
Q

Three Spool Axial Flow

A
  • Fan = Low pressure (LP) compressor (N1)
  • Intermediate pressure (IP) compressor (N2)
  • High pressure (HP) compressor (N3)
  • All are driven by separate turbines (3 shafts)
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15
Q

Stages of the Three spool axial flow

A

N1 (fan blade) => N2 compressor => N3 compressor => Diffuser => Combustor => Turbine inlet => High pressure turbine (N3) => Intermediate pressure turbine (N2) => Low pressure turbine (N1) => Exhaust

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16
Q

Blade attachment

A
  • blades are commonly held in place by dovetail or fir tree
  • Centrifugal forces will hold blades in place
17
Q

Compressor Blade Design

A

Blade twist helps maintain pressure throughout compressor

18
Q

Diffuser section

A
  • Rear of compressor
  • Divergent duct so Velocity decreases and pressure increases

HIGHEST PRESSURE POINT

19
Q

What is the highest pressure point?

A

The diffuser section

20
Q

Surges and Stalls of the compressor

A

Causes:
- Excessive rotor blade AOA
- Obstruction to inlet
- Excessive pressure in the burner section
- High crosswind on takeoff and low airspeed
- Abrupt flight maneuver

21
Q

Combustion Section Requirements

A
  • Minimum pressure loss in gas
  • High combustion efficiency
  • Combustion occurring entirely within the combustor
  • Uniform temp distribution throughout gases
  • Low risk of flame blowout
22
Q

Most common types of combustors

A
  • Multi-can
  • Can annular
  • Annular
23
Q

Multi-can combustor

A
  • Usually 8-10 cans
  • Igniters in only 2 cans
  • Crossover tubes connect cans

Advantages
- Individual cans can be removed

Disadvantages
- Uneven temps
- Uneven temps can cause turbine failure

24
Q

Can-annular

A
  • Consists of individual cans mounted on an annular duct
  • Hot gases are collected then directed into the turbine

Advantages
- Individual cans can be removed
- Shorter cans (lower pressure drop)
- Uniform temperatures even with a clogged fuel nozzle

25
Q

Annular

A
  • Makes the most efficient use of space
  • Efficient mixing of fuel with air
  • Requires minimum amount of cooling
  • Provided even temperature air
  • Cannot be replaced without removing the engine from the aircraft
26
Q

Turbine Section

A

Two Types:
- Radial inflow turbine
- Axial turbine

27
Q

There are stators (inlet guide vanes) between the combustion section and the turbine section

A
28
Q

Turbine inlet guide vanes

A

PLACE WITH THE HOTTEST TEMPERATURE

29
Q

Where is the hottest temperature?

A

turbine inlet guide vanes

30
Q

Turbine Blade Design

A

Reaction blade
- Produce turning force by aerodynamic action (airfoil)
Impulse Blade
- Produce turning force by the energy required to change the direction
of the airfoil
Reaction-Impulse
- A combination of the other two

31
Q

Turbine Cooling

A

Flowing compressor bleed air through hollow guide vanes

32
Q

Turbine Failures

A

Creep
- Deformation of metal that is continually under high centrifugal loads and temperatures

Metal fatigue
- Weakening of metal subjected to repeated cycles

Corrosion
- Electrolytic action that occurs when alloying agents combine w/ elements in the air to form salts
- Accelerated by exposure to extremely high temps

33
Q

Exhaust gases

A
  • The exhaust system can be used to accelerate air using Bernoulli’s principle to increase thrust
  • Uses a chocked bore nozzle
34
Q

Variable Area nozzle

A
  • opens/closes based on fuel flow
35
Q

Noise suppressors

A
  • Amount of noise relates to the velocity of the exhaust gases
  • Reduces efficiency
36
Q

Noise suppressors

A
  • Amount of noise relates to the velocity of the exhaust gases
  • Reduces efficiency
37
Q

Thrust Reverser

A
  • Used to assist brakes when landing
  • Diverts 40-50% of engines forward thrust rearward
38
Q

Vector thrust

A

Changing direction of exhaust nozzle or turbine engine entirely

38
Q

Vector thrust

A

Changing direction of exhaust nozzle or turbine engine entirely

Powerplants (3 decks)

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