Reciprocating compressor with vapor injection system

1. A compressor comprising:

a compression cylinder;

a compression piston disposed within said compression cylinder and operable to compress a vapor disposed within said compression cylinder from a suction pressure to a discharge pressure;

a crankshaft operable to cycle said compression piston within said compression cylinder;

an injection bore in fluid communication with said compression cylinder and operable to selectively communicate intermediate-pressure vapor at a pressure between said suction pressure and said discharge pressure to said compression cylinder;

a position sensor measuring a rotational position of said crankshaft; and

a valve assembly associated with said injection bore, said valve assembly operable to control passage of fluid from said injection bore into said compression cylinder in response to data provided by said position sensor.

2. The compressor of claim 1 , wherein said compression piston is movable within said compression cylinder between a top dead center (TDC) position and a bottom dead center (BDC) position, wherein said injection bore communicates with said compression cylinder through a bore having an outlet in a cylindrical wall of said compression cylinder, said outlet being axially aligned with a top surface of said compression piston when said compression piston is in said BDC position, such that when said compression piston is in said BDC position, said top surface of said compression piston and at least a portion of said outlet are equidistant from said TDC position along a longitudinal axis of said compression cylinder, and wherein said compression piston exposes said injection bore in said BDC position and blocks said injection bore in said TDC position.

3. The compressor of claim 2 , wherein said injection bore is partially blocked by said compression piston when said compression piston is in said BDC position.

4. The compressor of claim 2 , wherein said injection bore is fully exposed when said compression piston is in said BDC position.

5. The compressor of claim 1 , wherein said compression piston is movable within said compression cylinder between a top dead center (TDC) position and a bottom dead center (BDC) position, and wherein said injection bore communicates with said compression cylinder for the first half of piston travel from BDC to TDC.

6. The compressor of claim 1 , further comprising a controller in communication with said position sensor and said valve assembly and operable to control said valve assembly between an open state injecting said intermediate-pressure vapor into said compression cylinder and a closed state preventing injection of said intermediate-pressure vapor into said compression cylinder.

7. The compressor of claim 6 , further comprising a pressure sensor measuring a pressure within said compression cylinder and in communication with said controller, wherein said controller controls said valve assembly based on data from said pressure sensor and the data from said position sensor.

8. The compressor of claim 1 , wherein said injection bore communicates with said compression cylinder for 90 degrees of crankshaft rotation.

9. The compressor of claim 1 , further comprising a cylinder head disposed at an axial end of said compression cylinder, wherein said injection bore is disposed in said cylinder head.

10. The compressor of claim 1 , wherein said injection bore is disposed in a compressor housing in which said compression cylinder is formed.

11. The compressor of claim 1 , wherein said injection bore communicates said intermediate-pressure vapor to said compression cylinder when said compression piston exposes said injection bore, and wherein said injection bore is prevented from communicating said intermediate-pressure vapor to said compression cylinder when said compression piston blocks said injection bore.

12. A compressor comprising:

a compression cylinder;

a compression piston disposed within said compression cylinder and operable to compress a vapor disposed within said compression cylinder from a suction pressure to a discharge pressure;

a crankshaft operable to cycle said compression piston within said compression cylinder;

an injection bore in fluid communication with said compression cylinder and operable to selectively communicate intermediate-pressure vapor at a pressure between said suction pressure and said discharge pressure to said compression cylinder;

an injector disposed within said injection bore and operable to inject fluid into said compression cylinder;

a controller in communication with said injector and operable to control said injector between an open state injecting said intermediate-pressure vapor into said compression cylinder and a closed state preventing injection of said intermediate-pressure vapor into said compression cylinder; and

a position sensor in communication with said controller and measuring a rotational position of said crankshaft, said controller controlling said injector in response to data provided by said position sensor.

13. The compressor of claim 12 , wherein said compression piston is movable within said compression cylinder between a top dead center (TDC) position and a bottom dead center (BDC) position, wherein said injection bore communicates with said compression cylinder through a bore having an outlet in a cylindrical wall of said compression cylinder, said outlet being axially aligned with a top surface of said compression piston when said compression piston is in said BDC position, such that when said compression piston is in said BDC position, said top surface of said compression piston and at least a portion of said outlet are equidistant from said TDC position along a longitudinal axis of said compression cylinder, and wherein said compression piston exposes said injection bore in said BDC position and blocks said injection bore in said TDC position.

14. The compressor of claim 13 , wherein said injection bore is partially blocked by said compression piston when said compression piston is in said BDC position.

15. The compressor of claim 12 , wherein said injection bore communicates with said compression cylinder for 90 degrees of crankshaft rotation.

16. The compressor of claim 12 , further comprising a pressure sensor measuring a pressure within said compression cylinder and in communication with said controller, wherein said controller controls said injector based on data from said position sensor and said pressure sensor.

17. The compressor of claim 12 , further comprising a cylinder head disposed at an axial end of said compression cylinder, wherein said injector is disposed in said cylinder head.

18. The compressor of claim 12 , wherein said injector is disposed in a compressor housing in which said compression cylinder is formed.

19. The compressor of claim 12 , wherein said injector is in fluid communication with an economizer.

20. The compressor of claim 12 , wherein said injection bore communicates said intermediate-pressure vapor to said compression cylinder when said compression piston exposes said injection bore, and wherein said injection bore is prevented from communicating said intermediate-pressure vapor to said compression cylinder when said compression piston blocks said injection bore.

21. A compressor comprising:

a compression cylinder;

a compression piston disposed within said compression cylinder and operable to compress a vapor disposed within said compression cylinder from a suction pressure to a discharge pressure;

a crankshaft operable to cycle said compression piston within said compression cylinder;

an injection bore in fluid communication with said compression cylinder and operable to selectively communicate intermediate-pressure vapor at a pressure between said suction pressure and said discharge pressure to said compression cylinder;

an injector disposed within said injection bore and operable to inject fluid into said compression cylinder; and

a controller in communication with said injector and operable to control said injector between an open state injecting said intermediate-pressure vapor into said compression cylinder and a closed state preventing injection of said intermediate-pressure vapor into said compression cylinder,

wherein said compression piston is movable within said compression cylinder between a top dead center (TDC) position and a bottom dead center (BDC) position, and wherein said injection bore communicates with said compression cylinder for the first half of piston travel from BDC to TDC.

22. A compressor comprising:

a compression cylinder;

a compression piston disposed within said compression cylinder and operable to compress a vapor disposed within said compression cylinder from a suction pressure to a discharge pressure;

a crankshaft operable to cycle said compression piston within said compression cylinder;

an injection bore in fluid communication with said compression cylinder and operable to selectively communicate intermediate-pressure vapor at a pressure between said suction pressure and said discharge pressure to said compression cylinder;

an injector disposed within said injection bore and operable to inject fluid into said compression cylinder;

a controller in communication with said injector and operable to control said injector between an open state injecting said intermediate-pressure vapor into said compression cylinder and a closed state preventing injection of said intermediate-pressure vapor into said compression cylinder; and

a pressure sensor measuring a pressure within said compression cylinder and in communication with said controller, wherein said controller controls said injector based on data from said pressure sensor.