A compressor including a compression mechanism configured and positioned to receive vapor from an intake passage and provide compressed vapor to a discharge passage. An opening is positioned in the compression mechanism in fluid communication with the discharge passage. A valve has an aperture formed therein, the aperture configured and positioned in fluid communication with a passageway to provide a path for a pressurized vapor flow to a first chamber and a first piston without mixing with vapor in the discharge passage. A second chamber is in fluid communication with a second piston and the discharge passage, the first piston and the second piston of the valve configured to move together. First piston and second piston movement are controllable in response to predetermined conditions to maintain the magnitude of pressure of the compression mechanism immediately upstream of the opening at substantially the same pressure magnitude at the discharge passage.
1. A compressor comprising:
a compression mechanism, the compression mechanism being configured and positioned to receive vapor from an intake passage and provide compressed vapor to a discharge passage;
an opening positioned in the compression mechanism in fluid communication with the discharge passage;
a valve having an aperture formed therein, the aperture configured and positioned in fluid communication with a passageway to provide a path for a pressurized vapor to flow into a first chamber and in contact with a first piston therein without mixing with vapor in the discharge passage;
a second chamber in fluid communication with a second piston and the discharge passage, the first piston and the second piston of the valve configured to move together; and
movement of the first piston and second piston being controllable in response to predetermined conditions to maintain the magnitude of pressure of the compression mechanism immediately upstream of the opening at substantially the same pressure magnitude as is in the discharge passage.
2. The compressor of claim 1 , wherein the compression mechanism comprises rotors that engage one another.
3. The compressor of claim 1 , wherein the valve comprises a valve body slideably movable in a bore.
4. The compressor of claim 3 , wherein the valve body is movable in the bore in response to a difference in forces applied to the first piston and the second piston of the valve body.
5. The compressor of claim 3 , wherein the bore is positioned in the compression mechanism substantially parallel to a flow of vapor in the compression mechanism.
6. The compressor of claim 3 , wherein the first piston has a first surface area and an opposed second surface area, and the second piston has a surface area facing the second chamber.
7. The compressor of claim 6 , wherein:
a reference pressure is provided through the aperture and passageway formed in the valve body in fluid communication with the first chamber facing the first surface area of the first piston, thereby generating a force urging the first piston toward the opening in the compression mechanism;
a discharge pressure faces the second surface area of the first piston, thereby generating a force urging the first piston away from the opening in the compression mechanism; and
the discharge pressure in the second chamber in fluid communication with the surface area of the second piston, thereby generating a force urging the second piston toward the opening in the compression mechanism.
8. The compressor of claim 7 , including an equalizing line in fluid communication between the discharge passage and the second chamber.
9. The compressor of claim 8 , wherein equalizing line is formed in the valve body.
10. The compressor of claim 7 , wherein the reference pressure is less than the discharge pressure.
11. The compressor of claim 10 , wherein the reference pressure corresponds to the aperture and passageway formed in the valve body, there being a spacing between the aperture and a discharge opening portion formed in the valve body.
12. The compressor of claim 11 , wherein the discharge opening portion defines a recess formed in the valve body.
13. The compressor of claim 1 , wherein the predetermined conditions correspond to operating parameters of the compressor.
14. The compressor of claim 13 , wherein the operating parameters of the compressor include time of day of operation of the compressor, ambient conditions surrounding the compressor and load.
15. A screw compressor comprising:
an intake passage to receive vapor and a discharge passage to supply vapor;
a pair of intermeshing rotors, each rotor of the pair of intermeshing rotors being positioned in a corresponding cylinder, the pair of intermeshing rollers being configured to receive vapor from the intake passage and provide compressed vapor to the discharge passage;
an opening positioned in at least one rotor cylinder in fluid communication with the discharge passage;
a valve having an aperture formed therein, the aperture configured and positioned in fluid communication with a passageway to provide a path for a pressurized vapor to flow into a first chamber and in contact with a first piston therein without mixing with vapor in the discharge passage;
a second chamber in fluid communication with a second piston and the discharge passage, the first piston and the second piston of the valve configured to move together; and
movement of the first piston and second piston being controllable in response to predetermined conditions to maintain the magnitude of pressure of the pair of intermeshing rotors immediately upstream of the opening at substantially the same pressure magnitude as is in the discharge passage.
16. The screw compressor of claim 15 , wherein the valve comprises a valve body slideably movable in a bore.
17. The screw compressor of claim 16 , wherein the valve body is movable in the bore in response to a difference in forces applied to the first piston and the second piston of the valve body.
18. The screw compressor of claim 16 , wherein:
the first piston has a first surface area and an opposed second surface area, and the second piston has a surface area facing the second chamber;
a reference pressure is provided through the aperture and passageway formed in the valve body in fluid communication with the first chamber facing the first surface area of the first piston, thereby generating a force urging the first piston toward the opening in the at least one rotor cylinder;
a discharge pressure faces the second surface area of the first piston, thereby generating a force urging the first piston away from the opening in the at least one rotor cylinder; and
the discharge pressure in the second chamber in fluid communication with the surface area of the second piston, thereby generating a force urging the second piston toward the opening in the at least one rotor cylinder.
19. The screw compressor of claim 18 , including an equalizing line in fluid communication between the discharge passage and the second chamber.
20. The screw compressor of claim 18 , wherein the reference pressure is less than the discharge pressure, the reference pressure corresponding to the aperture and passageway formed in the valve body, there being a spacing between the aperture and a discharge opening portion formed in the valve body.