15.04

Question 1

What are the two ways you can compress air in an engine?

Answer 1

. Decrease the volume in a cylinder
. Make use of Bernoulli’s principe

Question 2

What are the two main compressor components?

Answer 2

Rotor and stator

Question 3

What does the rotor do?

Answer 3

Increase airflow energy

Question 4

What does the stator do?

Answer 4

Guide the airflow

Question 5

What are the set of stators in front a compressor stage called?

Answer 5

Inlet guide vanes

Question 6

What are the stators called in the fan duct?

Answer 6

Outlet guide vanes

Question 7

Where are centrifugal flow compressors usually found?

Answer 7

Small gas turbine engines such as APU

Question 8

What is the pressure ratio of centrifugal flow compressors?

Answer 8

5:1

Question 9

What is it called when two impellers are mounted face to face?

Answer 9

Double face compressor

Question 10

What are some advantages of double face compressors?

Answer 10

Air can enter from front and back, higher airflow, saves weight

Question 11

In an axial flow compressor what do the rotors do?

Answer 11

Increase velocity of the air but also slow it down, and increase static pressure

Question 12

Why do we taper axial flow compressors?

Answer 12

Maintain velocity

Question 13

The airflow in the axial compressor is smooth as long as?

Answer 13

The angle of attack on the rotor and stator vanes is small

Question 14

What is airflow separation also called?

Answer 14

Compressor stall

Question 15

What does compressor stall cause the airflow to do?

Answer 15

Airflow stops and slows down and sometimes reverses

Question 16

What is a severe form of compressor stall?

Answer 16

Compressor surge

Question 17

Where can compressor surge happen?

Answer 17

Fwd or aft compressor stage

Question 18

What happens at compressor surge in the aft compressor?

Answer 18

Airflow decreases rapidly and reverses

Question 19

What are some reasons for stall and surge in the compressor?

Answer 19

Dents or ice, damaged rotor blades, dirty blades, damaged compressor, damaged turbine

Question 20

How can the compressor stall?

Answer 20

Engine is far below designed speed, incorrect acceleration or deceleration

Question 21

What are the methods to avoid compressor stall and surge?

Answer 21

Compressor bleed valves, use dual or triple spool instead of single, variable compressor stator vanes

Question 22

When are compressor bleed valves opened?

Answer 22

Low engine speeds

Question 23

Each compressor rotor is driven by a separate?

Answer 23

Turbine

Question 24

What is the most effective method to prevent stall?

Answer 24

Variable stator vanes

Question 25

What does the spinner comb create?

Answer 25

Smooth aerodynamic fairing at engine inlet

Question 26

What is the fan rotor disc made from?

Answer 26

Titanium alloy

Question 27

What type of fitting is used on most aircraft?

Answer 27

Dovetail fitting

Question 28

What is a loose fit necessary on engine parts?

Answer 28

Allow for sudden forces or torques

Question 29

What forces act on rotor blades?

Answer 29

Centrifugal force and air loads

Question 30

What does the shroud help the fan blade do?

Answer 30

Keeps deflection within safe limits

Question 31

What can a wide chord blade withstand?

Answer 31

Foreign object damage because of its flexibility

Question 32

On a turbofan engine the fan case has?

Answer 32

One or more ring elements

Question 33

What do linings provide in the fan case?

Answer 33

Smooth surface for airflow

Question 34

What do the holes on the fan case reduce?

Answer 34

Noise

Question 35

When does unbalance occur on the fan rotor?

Answer 35

Material is removed from the blade

Question 36

What is the best method when replacing a fan blade?

Answer 36

New blade with almost equal weight to the old one

Question 37

What are balance weights used for on blades?

Answer 37

Compensate for imbalances

Question 38

What seal do knife edges create?

Answer 38

Labyrinth seal

Question 39

Each HP compressor always has a ….. seal

Answer 39

CDP

Question 40

Why do inner ends of vane segments have an inner platform?

Answer 40

Reduce vibrations

Question 41

Compressors with high compression ratios have?

Answer 41

Variable stator vanes

Question 42

What does the HP compressor source?

Answer 42

Pressurised air for pneumatic system

Question 43

What is bleed air supplied through?

Answer 43

Hollow stator vanes