Dynamic Compressors

Question 1

Dynamic balancing

Answer 1

• balancing the shaft when it’s rotating

Question 2

Three casing designs

Answer 2

-sectional (vacuum), horizontal split, vertically split (high pressure)

Question 3

Three different types of impellers

Answer 3

-open, semi-closed, closed (highest efficiencies because of the close tolerances, minimal leakage)

Question 4

Guide Elements/vanes

Answer 4

-control and direct gas flow into the compressor or from one stage to the next

Question 5

How do you control thrust in dynamic compressors

Answer 5

-balance Pistons, thrust bearings and impeller arrangements (opposing air flows)

Question 6

Balance piston

Answer 6

• located at the discharge end, immediately behind the last impeller.
• provides a surface area on which the full discharge pressure act.

Question 7

Thrust bearings

Answer 7

-

Question 8

Labyrinth Seal

Answer 8

• are installed in the diaphragm assembly to minimize internal leakage along the shaft from the progressively higher stage pressures.
• seals by allowing a small amount of high pressure gas to escape into the chamber formed by the following ring

Question 9

Drum rotors

Answer 9

• discs that are flanged to fit to each other and are held together with tie bolts and stub shafts that may bolt or press into place.
• may also be hollow cylinders machines with the blades bolted to them and end covers with welded stub shafts

Question 10

Diaphragm

Answer 10

• separates the impellers in the compressor casing

- they direct flow throw the compressor

Question 11

Axial Compressors

Answer 11

• each stage consist of a number of blades that attach to the rotor and work with corresponding blades on the stator.
• air flows down the shaft through stationary Stators

Question 12

Blade Fouling

Answer 12

-debris for the dirty gases, etc… That stick to the blades

Question 13

Surge

Answer 13

• when low flow causes flow reversal and compressed gas rushed back from the discharge to the inlet, which causes a pressure drop at the discharge
• controlled by a bypass (air) or recycle valve (gas) which sends air back the the suction drum so pressure is balanced

Question 14

Stators

Answer 14

-are a series of blades that attach to the casing wall. They can be fixed or adjustable and solid or hollow

Question 15

Three main parts of Axial flow compressors

Answer 15

Rotor, stator and casing

Question 16

Best way to control output

Answer 16

• varying the speed

- varying stator arrangement

Question 17

Surge Point

Answer 17

-

-high pressure at the outlet

Question 18

Stonewall

Answer 18

• where max flow and max velocity has been reached

- low pressure at the outlet

Question 19

Multi-flow compressors

Answer 19

-gives you the ability to dramatically increase the pressure ratio. For each impeller you add you can reduce 3-4 axial stages

Question 20

Single stage

Answer 20

-high volume low pressure

Question 21

Kinetic energy

Answer 21

-energy in motion

Question 21

Carbon Seals

Answer 21

• low pressure seals

- often used with labyrinth seals as the final sealing element

Question 22

Beam

Answer 22

-multi-stage the rotor being supported by bearings at both ends

Question 23

Impeller arrangements (thrust control)

Answer 23

-dual

Question 24

Absolute zero

Answer 24

• 0 rankin and kelvin
• -273 Celsius (kelvin) think CK Calvin Klein
• -460 Fahrenheit (rankin)

Question 25

What’s needed at inlet

Answer 25

• outside pressure needs to be slightly higher than 0 for pressure differential to occur. Pressure will always go from high to low.
• inlet has to be lowest pressure

Question 26

What creates the pressure in a compressor?

Answer 26

• the decrease of air flow throw the diffuser.

- the air being brought in and sped up with the impeller doesn’t create the pressure