Intermediate discharge port for a compressor

A heating, ventilation, and air conditioning (HVAC) system, comprising:

• a condenser, an expansion device, and an evaporator, and a screw compressor fluidly connected and forming a heat transfer circuit, wherein the screw compressor includes:
• a compressor housing defining a working chamber, the housing including two bores;
• a first rotor having helical threads, the first rotor being housed in a first of the two bores;
• a second rotor having helical threads intermeshing with the helical threads of the first rotor, the second rotor being housed in a second of the two bores;
• an inlet suction port that receives a fluid to be compressed;
• an outlet discharge port that receives a compressed fluid;
• a compression chamber formed by the intermeshing of the helical threads of the first rotor and the helical threads of the second rotor between the inlet suction port and the outlet discharge port;
• and
• an intermediate discharge port fluidly connectable to the compression chamber and disposed between the inlet suction port and the outlet discharge port and spaced from the outlet discharge port,
• the intermediate discharge port being disposed at a top portion of the compressor housing so that a piston included in the intermediate discharge port is fluid-forced vertically upward or downward to selectively transition the intermediate discharge port between a flow-blocked state and a flow-permitted state, based on an operating pressure ratio of the compressor, the operating pressure ratio between fluid in the compression chamber and the compressed fluid at the outlet discharge port,
• the intermediate discharge port including a sealing member having a sealing surface that follows a contour of the first bore and the second bore and forms a sealing engagement with a surface within the intermediate discharge port when biased by the piston to be in the flow-blocked state so that fluid flow is prevented between the compression chamber and the intermediate discharge port when in the flow-blocked state, and fluid flow being enabled from the compression chamber through the intermediate discharge port when biased by the piston to be in the flow-permitted state in which the sealing surface is disengaged from sealing engagement with the surface within the intermediate discharge port,
• the sealing surface being disposed at a first vertical distance from the compression chamber when in the flow-blocked state and a second vertical distance from the compression chamber when in the flow-enabled state, the first vertical distance being relatively smaller than the second vertical distance.

A method, comprising:

• providing an intermediate discharge port at a location in fluid communication with a compression chamber of a screw compressor, the intermediate discharge port being disposed between an inlet suction port and an outlet discharge port of the screw compressor and spaced from the outlet discharge port, the intermediate discharge port being disposed at a top portion of a compressor housing of the screw compressor so that a piston included in the intermediate discharge port is fluid-forced vertically upward or downward to selectively transition the intermediate discharge port between a flow-blocked state and a flow-permitted state, based on an operating pressure ratio of the compressor, the operating pressure ratio between fluid in the compression chamber and the compressed fluid at the outlet discharge port,
• wherein when operating the screw compressor at part-load,
• discharging a portion of a working fluid being compressed from the compression chamber toward a discharge of the screw compressor, the working fluid being at a pressure that is lower than a discharge pressure of the screw compressor, and
• when operating the screw compressor at full-load,
• discharging the working fluid being compressed from the outlet discharge port of the screw compressor.

A screw compressor, comprising:

• a compressor housing defining a working chamber, the housing including a plurality of bores;
• a first rotor having helical threads, the first rotor being housed in a first of the plurality of bores;
• a second rotor having helical threads intermeshing with the helical threads of the first rotor, the second rotor being housed in a second of the plurality of bores;
• an inlet suction port that receives a fluid to be compressed;
• an outlet discharge port that receives a compressed fluid;
• a compression chamber formed by the intermeshing of the helical threads of the first rotor and the helical threads of the second rotor between the inlet suction port and the outlet discharge port;
• and
• an intermediate discharge port fluidly connectable to the compression chamber and disposed between the inlet suction port and the outlet discharge port and spaced from the outlet discharge port,
• the intermediate discharge port being disposed at a top portion of the compressor housing so that a piston included in the intermediate discharge port is fluid-forced vertically upward or downward to selectively transition the intermediate discharge port between a flow-blocked state and a flow-permitted state, based on an operating pressure ratio of the compressor, the operating pressure ratio between fluid in the compression chamber and the compressed fluid at the outlet discharge port,
• the intermediate discharge port is passively controlled by the piston based on a pressure ratio between a fluid in the compression chamber and the compressed fluid at the output discharge port to place the intermediate discharge port in the flow-blocked state or the flow-permitted state,
• the intermediate discharge port including a sealing member having a sealing surface that follows a contour of the bores and forms a sealing engagement with a surface within the intermediate discharge port when biased by the piston to be in the flow-blocked state so that fluid flow is prevented between the compression chamber and the intermediate discharge port when in the flow-blocked state, and fluid flow being enabled from the compression chamber through the intermediate discharge port when biased by the piston to be in the flow-permitted state in which the sealing surface is disengaged from sealing engagement with the surface within the intermediate discharge port,
• the sealing surface being disposed at a first vertical distance from the compression chamber when in the flow-blocked state and a second vertical distance from the compression chamber when in the flow permitted state, the first vertical distance being relatively smaller than the second vertical distance.