M15.4 Compressors

Question 1

Two components of compressor

Answer 1

Rotors
Stators

Question 2

Is a rotor or stator first in the compressor stage?

Answer 2

Rotor always first part

Question 3

What are the blades attached to stators called?

Answer 3

Stator vanes

Question 4

What do stator vanes do?

Answer 4

They guide and slow the airflow to cause an increase in pressure

Question 5

If there is a set of stator vanes in front of the compressor stage what are they called?

Answer 5

Inlet guide vanes (IGV)

Question 6

The stator vanes in the fan duct are known as what?

Answer 6

Outlet guide vanes (OGV)

Question 7

What are outlet guide vanes used for?

Answer 7

Improving airflow into the fan nozzle

Question 8

Two types of compressors in gas turbine engines?

Answer 8

Centrifugal flow compressor
Axial flow compressor

Question 9

Centrifugal flow compressors consist of what components?

Answer 9

Impeller (Rotors)
A diffuser (Stator)
A compressor manifold

Question 10

Function of an impeller?

Answer 10

Pick up and accelerate the air outwardly to diffuser

Question 11

Axial flow compressors are used on what engines?

Answer 11

Turbofan engines

Question 12

Centrifugal flow compressors are used on what type of engines?

Answer 12

Turboprop and Turboshaft engines

Question 13

What is a ‘stage’ of an axial flow compressor?

Answer 13

Rotor-Stator pair

Question 14

How many stages are centrifugal compressors limited to?

Answer 14

2 stages

Question 15

How are fan blades numbered?

Answer 15

Generally numbered in direction of rotation

Question 16

Where can compressor surges occur in the compressor?

Answer 16

Forward or aft stages

Question 17

Reasons for stall or surges in compressor?

Answer 17

Dents or ice reduce inlet velocity
Damaged rotor blades or stator vanes disturb airflow
Dirty compressor blades

Question 18

Two operational reasons for stall and surge?

Answer 18

Compressor can stall if the speed of engine is too far below design speed
Can stall at incorrect acceleration or deceleration

Question 19

What are bleed valves and where are they found?

Answer 19

Found in mid-section and sometimes aft of compressor
Open at low speeds so excessive airflow from fwd stages escape overboard.

Question 20

3 methods to avoid stall or surge?

Answer 20

Bleed valves
Dual or triple spools
Variable stator vanes

Question 21

Advantage of variable stator vanes?

Answer 21

An optimum angle of attack can be reached for every engine speed

Question 22

Disadvantage of variable stator vanes?

Answer 22

Needs a complicated control mechanism

Question 23

What is a compression ratio?

Answer 23

The ratio of the volume of its combustion chamber from its largest to its smallest capacity