Dunham-Bush WCFX-E Series, Руководство пользователя

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UNIT FEATURES
Compressor Operation
Note: For clarity reasons, the following account of the
compressor operation will be limited to one lobe on the
male rotor and one interlobe space of the female rotor. In
actual operation, as the rotors revolve, all of the male
lobes and female interlobe spaces interact similarly with
resulting uniform, non-pulsating gas flow.
Suction Phase
As a lobe of the male rotor begins to unmesh from an
interlobe space in the female rotor, a void is created and
gas is drawn in tangentially through the inlet port -- Fig. A.
-- As the rotors continue to turn the interlobe space
increases in size -- Fig. B -- and gas flows continuously
into the compressor. Just prior to the point at which the
interlobe space leaves the inlet port, the entire length of
the interlobe space is completely filled with drawn in gas -
- Fig C.
Compression Phase
As rotation continues, the gas in the interlobe space is
carried circumferentially around the compressor housing.
Further rotation meshes a male lobe with the interlobe
space on the suction end and squeezes (compresses)
the gas in the direction of the discharge port. Thus the
occupied volume of the trapped gas within the interlobe
space is decreased and the gas pressure consequently
increased
Discharge Phase
At a point determined by the designed "built-in"
compression ratio, the discharge port is covered and the
compressed gas is discharged by further meshing of the
lobe and interlobe space - Fig. D. While the meshing
point of a pair of lobes is moving axially, the next charge
is being drawn into the unmeshed portion and the
working phases of the compressor cycle are repeated.
Compressor Fully Unloaded Compressor Fully Loaded
Slide Valve Control
Movement of the slide valve is programmed by an
exclusive Dunham-Bush electronically initiated (by
variations in leaving chilled water temperature)
hydraulically actuated control arrangement. When the
compressor is fully loaded, the slide valve is in the closed
position. Unloading starts when the slide valve is moved
back away from the valve stop. Movement of the valve
creates an opening in the side of the rotor housing.
Suction gas can then pass back from the rotor housing to
the inlet port area before it has been compressed. Since
no significant work has been done on this return gas, no
appreciable power losses are incurred. Reduced
compressor capacity is obtained from the gas remaining
in the rotors which is compressed in the ordinary manner.
Enlarging the opening in the rotor housing effectively
reduces compressor displacement.
FIG. A
FIG. B
FIG. C
FIG. D