2205Q2JE-HO-S6-N_2020.01.
Chapter 2 Compressor Specifications and Structure
SCV-series Screw Compressor 2.4 Compressor Structure and Mechanism
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2.4.3.2 Variable Vi Mechanism
The combination of the following two factors determines the Vi value:
[1] The size of the axial port in the bearing head (port extending in the rotor axis direction)
[2] The size of the radial port in the unloader slide valve (port extending in the direction perpendicular to
the rotor axis direction)
The conventional fixed-Vi
compressors have axial and radial ports both fixed to the sizes
corresponding to the L, M, or H port.
The SCV-series compressors also have a fixed axial port of the size corresponding to Vi = 5.1, but the
radial port in the unloader slide valve is made variable to constitute a variable Vi mechanism. This is
achieved by making the full-load end of the unloader slide valve, which is fixed with the conventional
models, variable as necessary.
Figure 2-10 compares the discharge ports or the fixed and variable Vi compressors.
Conventional compressors (fixed Vi) SCV Series compressors (variable Vi)
• Both axial and radial ports fixed • Axial port fixed, radial port variable
[1]: The size of the axial port in the bearing head
[2]: The size of the radial port in the unloader slide valve
Figure 2-10 Discharge Ports of Variable and Fixed Vi Compressors