15.4 compressor

Question 1

what is the primary function of the compressor

Answer 1

to supply a sufficient quantity of air to satisfy the requirements of the combustion chamber

Question 2

what are the two main components of the compressor

Answer 2

compressor rotor
compressor stator

Question 3

what is mounted in each rotor

Answer 3

rotor blades

Question 4

what component of the compressor is stationary

Answer 4

the stator

Question 5

what component is always the first part of the compressor stage

Answer 5

the rotor

Question 6

what are inlet guide vanes

Answer 6

a set of stator vanes in front of a compressor stage

Question 7

what are the stator vanes in the fan duct usually called

Answer 7

outlet guide vanes

Question 8

what are the two types of compressors being currently used

Answer 8

centrifugal flow compressor
axial flow compressor

Question 9

what does the centrifugal-flow compressor consist of

Answer 9

an impeller, a diffuser, and a compressor manifold

Question 10

how many stage are there in a centrifugal-flow compressor

Answer 10

only 2 stages

Question 11

what is the function of the impeller

Answer 11

to pick up and accelerate the air outwardly to the diffuser

Question 12

where are axial flow compressors normally found

Answer 12

on turbofan engines

Question 13

where are centrifugal flow compressors usually found

Answer 13

on turboshaft and turboprop

Question 14

what does a single-spool axial flow compressor consist of

Answer 14

a single drum and multiple stators

Question 15

in an axial flow compressor how is the total number of stages determined

Answer 15

it is based on the desired pressure increase

Question 16

what are the three parameters that the centrifugal forces depend on

Answer 16

• rotor speed
• blade mass
• the distance of the centre of gravity of the blade from the rotational axis

Question 17

where can the blade moment weight usually be seen

Answer 17

on the blade root

Question 18

why is the moment weight sometimes crossed out and another number is shown

Answer 18

the moment weight has changed because of blending

Question 19

what are the two methods proposed to change a single fan blade

Answer 19

1. replacing the blade with a new that has a moment weight as close as possible to the old one
2. always change a pair of blades with similar moment weight

Question 20

what do axial floe and centrifugal flow have in common

Answer 20

they are very sensitive to change in the airflow which passes through the compressor

Question 21

what is need for smooth airflow into the rotor

Answer 21

the correct relationship between the inlet velocity and the rotor speed is required

Question 22

the airflow in the axial compressor is smooth as long as what

Answer 22

the angle on the rotor blades and stator vanes is small

Question 23

what is compressor surge

Answer 23

a very severe form of compressor stall

Question 24

what are compressor stall and surge caused by

Answer 24

problems in engine operations or damaged engine components

Question 25

aircraft engines have three different design methods to prevent compressor stall and surge what are they

Answer 25

1. compressor bleed valves 2. dual or triple spool rotors 3. variable compressor stator vanes

Question 26

when are bleed valves opened

Answer 26

at low engine speeds

Question 27

what is the most effect method of preventing compressor

Answer 27

variable stator vanes

Question 28

what is the advantage of variable stator vanes

Answer 28

an optimum angle of attack on the following rotor blades can be reached for every engine speed

Question 29

each stage of an axial flow compressor has a ratio of about ...

Answer 29

1.3:1

Question 30

what does the compression ratio varies with

Answer 30

RPM