Spiral valve for screw capacity control

A screw compressor comprising:

• a compressor housing defining a compression chamber;
• a female compression screw disposed within the compression chamber;
• a male compression screw disposed within the compression chamber and interfacing with the female compression screw;
• a plurality of bypass ports formed in the compressor housing and providing fluid communication through the compressor housing;
• a compressor inlet transfer duct formed in the compressor housing to allow fluid communication with a compressor inlet;
• and
• a spiral valve comprising:
• an actuator module disposed adjacent an exterior of the compressor housing, the actuator module comprising:
• an electric motor;
• a gearbox mechanically coupled to the electric motor to transmit a torque from the electric motor;
• a spiral valve body coupled to the gearbox to rotate in response to the torque transmitted from the electric motor, wherein spiral valve body comprises:
• a first shell area defining a first shutter positioned to open and close the plurality of bypass ports formed in the compressor housing based on a rotational position of the first shutter;
• a second shell area defining a second shutter positioned to progressively open and close the compressor inlet transfer duct formed in the compressor housing based on a rotation position of second shutter;
• and
• a gap formed between the first shell area and the second shell area,
• wherein a compression length of the screw compressor is configured to be controlled by controlling opening and closing of the plurality of bypass ports, and
• wherein the first shell area is rotatable relative to the second shell area.