15.4

Question 1

Compressors are made up of what?

Answer 1

Stators and rotors

Question 2

What pressure do rotors increase?

Answer 2

Dynamic pressure

Question 3

Stator vanes do what?

Answer 3

Slow airflow and increase pressure

Question 4

Which is first in compressor stage out of rotors and stators?

Answer 4

Rotors

Question 5

What are stator vanes also known as?

Answer 5

Inlet guide vanes (IGV)

Question 6

Two types of compressors?

Answer 6

Axial flow
Centrifugal flow

Question 7

What are the main components of a centrifugal compressor?

Answer 7

The impeller
The diffuser
The compressor manifold

Question 8

Centrifugal flow compressors give what pressure ratio?

Answer 8

5:1

Question 9

How many compressor stages are efficient?

Answer 9

2

Question 10

Two impellers mounted back to back are known as what?

Answer 10

Double face compressor

Question 11

What are the benefits of double face compressors?

Answer 11

Increase airflow due to two sides
Saves weight

Question 12

Airflow in axial flow compressor is on what axis?

Answer 12

Horizontal axis

Question 13

As pressure increases, density….

Answer 13

Increases

Question 14

You taper axial flow compressors why?

Answer 14

Maintain air velocity

Question 15

Why are compressors sensitive to airflow change?

Answer 15

Because compressors only have one operating condition for a given pressure ratio, rotational speed and airflow

Question 16

What is the direction of airflow better called?

Answer 16

The resultant rotor inlet velocity

Question 17

The resultant rotor inlet velocity is a result of what?

Answer 17

Air inlet velocity and rotor speed

Question 18

The angle of attack changes when?

Answer 18

If rotor speed or inlet velocity changes

Question 19

Compressor stall causes what for airflow in the compressor?

Answer 19

Causes airflow to slowdown, stop or reverse direction

Question 20

A compressor surge is a very severe what?

Answer 20

Compressor stall

Question 21

How is a compressor surge generated?

Answer 21

Rapid decrease of airflow onto blades
Then stall causes a blockage
That then causes low pressure zones

Question 22

Surge is forward phase affects what?

Answer 22

Compressor blades

Question 23

A surge in the aft stages could cause what to happen?

Answer 23

A reverse flow
Could occur from combustion chamber back to engine inlet

Question 24

What are reasons for stalls and surges?

Answer 24

Dents or ice that cause disrupted airflow
Damaged rotor blades could cause disrupted airflow
Dirty compressor blades

Question 25

How does a fast deceleration cause similar problems on dual to triple spool engines?

Answer 25

The rotor speed of high pressure compressor decreases faster than that of low pressure compressor

Question 26

What is a method to avoid stalls or surges?

Answer 26

Use of dual or triple spools

Question 27

Where are bleed valves found in compressors?

Answer 27

Found in mid and sometimes aft section of compressor

Question 28

Why would you open the bleed valves at slow speeds?

Answer 28

So excessive airflow from forward stages can escape overboard

Question 29

What are the low speed and high speed compressors driven by?

Answer 29

Their respective turbines in latter stages of engine

Question 30

Variable stator vanes in compressor are used to prevent what?

Answer 30

Stall- Along vertical axis

Question 31

The spinner cone is also known as what?

Answer 31

Compressor inlet or nose cone

Question 32

Why do engines have a spinner cone?

Answer 32

-creates smooth aerodynamic fairing at engine inlet -soft tip causes small imbalance to prevent ice build up -heated on some engines

Question 33

What type of attachment is the fan blade attachment?

Answer 33

Dovetailed fitting

Question 34

Two loads on rotor blades?

Answer 34

Air loads Centrifugal loads

Question 35

What is the function of shrouds?

Answer 35

Keeps fan blade from deflection, within safe limits when heavy loads are on them Converts energy of fluttering to friction

Question 36

Why are wide chord fan blades more efficient than conventional blades?

Answer 36

They run with lower speed which reduces noise Flexible Can withstand FOD better than conventional

Question 37

Low pressure compressor is also known as what?

Answer 37

Booster modules

Question 38

Rotor drum of low pressure compressor is attached to what?

Answer 38

Fan disc

Question 39

Between dovetail slots there are rings with sharp edges to create what?

Answer 39

A labyrinth seal

Question 40

What are two methods of making shroud assembly?

Answer 40

Made from plain metal surfaces Or individual segments

Question 41

Shroud assembly segments are made up of what?

Answer 41

Filled with soft, abradable material where knife edges can cut in

Question 42

On modern turbofan engine the fan cause has one or more ring elements, how are they bolted?

Answer 42

They’re bolted together to flanges -Flanges help stiffen the case and prevent deformation

Question 43

Acoustic panels provide what?

Answer 43

Smooth airflow Reduce noise

Question 44

The fan blade containment prevents what?

Answer 44

A fan blade from penetrating the fan case if it breaks during high speed operation

Question 45

What are some things that would affect centrifugal force?

Answer 45

Rotor speed Blade mass Distance of the COG of fan blade from rotational axis

Question 46

Moment weight can be given in what values?

Answer 46

Gram inches CMG ounce inches

Question 47

What is the moment of weight?

Answer 47

The product of blade mass and distance of COG from rotational axis

Question 48

How is moment of weight worked out?

Answer 48

Worked out by special blade scale

Question 49

How is fan number one identified?

Answer 49

Index mark on fan disc or by an offset hole

Question 50

Where are balance weights installed?

Answer 50

On fan disc or in spinner cone

Question 51

A typical high pressure compressor consists of what?

Answer 51

Rotor drum Forward hub Rear hub Rotor blades mounted on a drum

Question 52

What is CDP?

Answer 52

Compressor discharge pressure

Question 53

The compressor discharge pressure (CDP) prevents what?

Answer 53

Prevents the compressor discharge airflow from escaping into the bearing area below the combustion chamber

Question 54

Blades held in by blade retainers prevents what?

Answer 54

Prevents axial movement

Question 55

How are rotor blades secured?

Answer 55

Locking lug

Question 56

The high pressure compressor case is split into what?

Answer 56

Front compressor case Rear compressor case

Question 57

The front compressor case supports what loads?

Answer 57

Structural loads Torsion Bending

Question 58

Variable stator vanes have what at each end?

Answer 58

Trunnion

Question 59

The HP compressor is a source of pressurised air for what?

Answer 59

Pneumatic systems Engine related purposes

Question 60

Bleed air is supplied through what?

Answer 60

Hollow stator vanes

Question 61

Bleed manifolds collect bleed air and do what?

Answer 61

Supply it to consumers

Question 62

What are the fixed axial flow compressor aerofoils in an aircraft gas turbine engine called?

Answer 62

Stators

Question 63

What is the function of the stator vane assembly at the discharge end of a typical axial flow compressor?

Answer 63

To straighten airflow to eliminate turbulence

Question 64

Where does the pressure increase in an axial compressor stage?

Answer 64

In both the rotor and the stator

Question 65

Why do the compressor stators in a gas turbine engine act as diffusers?

Answer 65

To decrease velocity in the gas flow

Question 66

What is known as the design point of a gas turbine engine?

Answer 66

Optimum RPM the engine can operate at

Question 67

Which installed components can prevent compressor stalls?

Answer 67

Bleed valves, multiple spools and variable stator vanes