Book 2 - Centrifugal Compressors

Question 1

centrifugal compressor vanes form _________ passages

Answer 1

centrifugal compressor vanes form DIVERGENT passages

Question 2

the rotational energy of the compressor imparts ________ into the air, but because the disc vanes have divergent passages, some of the energy is converted into ________ and __________

Answer 2

the rotational energy of the compressor imparts VELOCITY into the air, but because the disc vanes have divergent passages, some of the energy is converted into TEMPERATURE and PRESSURE

Question 3

from the compressor, the air enters the ________ ring

Answer 3

from the compressor, the air enters the DIFFUSER ring

Question 4

the diffuser ring has _________ passages that cause most of the remaining velocity energy to be converted to ________ and __________

Answer 4

the diffuser ring has DIVERGENT passages that cause most of the remaining velocity energy to be converted to PRESSURE and TEMPERATURE

Question 5

centrifugal compressor efficiency tends to be ___. this is because the high _________ speed and drastic change in air flow _________ greatly increases air temperature

Answer 5

centrifugal compressor efficiency tends to be LOW. this is because the high ROTATION speed and drastic change in air flow DIRECTION greatly increases air temperature

Question 6

what are the two types of centrifugal impeller?

Answer 6

• single sided

- double sided

Question 7

the double-sided impeller will give a greater ____ air flow for an equivalent _______ area

Answer 7

the double-sided impeller will give a greater MASS air flow for an equivalent FRONTAL area

Question 8

what are the main disadvantages of the centrifugal compressor? (4)

Answer 8

• high speed of rotation required
• large frontal area
• limited pressure ratio
• high temperature increase

Question 9

the impeller of a centrifugal compressor is forged from __________ alloy. the rotating guide vanes are often made out of _____ to resist impact damage and are splined on to the aluminium impeller. some rotating guide vanes are forged out of the same _____ as the impeller disc. other, more modern impellers are completely made from _________

Answer 9

the impeller of a centrifugal compressor is forged from ALUMINIUM alloy. the rotating guide vanes are often made out of STEEL to resist impact damage and are splined on to the aluminium impeller. some rotating guide vanes are forged out of the same BLOCK as the impeller disc. other, more modern impellers are completely made from TITANIUM

Question 10

the impeller tips will often reach speeds of ____ft/sec

Answer 10

the impeller tips will often reach speeds of 1600ft/sec

Question 11

when impeller tip speeds reach sonic values, no more pressure increase is possible, which limits the pressure ratio of a centrifugal compressor to about ./1

Answer 11

when impeller tip speeds reach sonic values, no more pressure increase is possible, which limits the pressure ratio of a centrifugal compressor to about 4.5/1