Please enable JavaScript.

Coggle requires JavaScript to display documents.

CHAPTER 5: COMPRESSORS, Principles of compression, Basic Operation:,…

- - - - Basic Operation:
        
        Gas enters a centrifugal compressor at the suction inlet & is accelerated by moving impellers.
        
        As high-velocity gas moves through the diffuser into volute, kinetic energy converted into pressure as gas speed slows in the volute before exiting the discharge port.
      - More sensitive to density & fluid characteristics
      - Designed to operate at speeds in excess of 3000 rpm
      - It can be:
        
        Single stage
        
        Designed for high gas flow rates & low discharge pressure. Compress the gas once.
        
        Multistage
        
        Designed for high gas flow & high discharge pressure. Deliver the discharge of one stage to the suction of another stage.
    - - Basic Operation:
        
        Rotating blades attached to shaft push gasses over stators (stationary blades)
        
        As the rotating blades increase the gas velocity, the stator blades slow it down
        
        Airflow is moved axially along the shaft
        
        Gas velocity increases as it moves stages by stages until it reaches the discharge line.
        
        As the gas slows, kinetic energy is released in the form of pressure.
      - Applications:
        
        Used for jobs where highest flow & pressure required.
        
        Involves transfer to clean gas such as air
      - Features:
        
        Require twice as many stages as centrifugal compressor to perform the same position.
        
        More lighter & smaller than centrifugal pumps
        
        Internal component are sensitive or corrosion, pitting & deposits
  - - - Rotary Screw Compressors
      - Sliding Vane Compressors
        
        Basic Operation:
        
        As gas enters the sliding vane compressors, it is captured in vanes and swept around the casing
        
        As the vane rotate toward the discharge, the vane length shortens because of the rotor's eccentric position with the shaft, and volume is decreased
        
        As volume decreases, pressure increases
        
        Then, gas is discharged out of the compressor
      - Lobe
        
        Designed to have constant volume discharge pressure & constant speed drives.
        
        Can be used in wet & dry gas services
        
        Characterized by the two kidney-bean-shaped impellers used to trap and transfer gases.
        
        Also can be used as vacuum pumps
        
        Basic Operation:
        
        2 impellers move on opposite direction during operation.
        
        They forcing gas to become trapped & discharge it at higher pressure.
      - Liquid Ring Compressors
        
        Unusual compressor design
        
        Combine centrifugal action
        
        With positive displacement
        
        Rotary action
        
        Found in application;
        
        Hazardous gases
        
        Toxic gases
        
        Hot gases & vapor
    - - Piston Compressors
        
        Basic Operation:
        
        Work by tapping & compressing specific amount of gas between a piston & cylinder well.
        
        The back & forth motion incorporated by a reciprocating compressor pull gas on the suction & discharge on the other.
        
        Spring loaded suction n& discharge valves work automatically as piston moves up & dow
        
        Perform best with clean gasses
        
        Entrained water, dirt, & impurities will cause excessive wear on the piston & cylinder.
        
        Advantages:
        
        Flexible pressure range & overall capacity, low power cost & high efficiency
        
        Density & gas composition changes, small volumes & deliver high pressure
      - Diaphragm