Multi-compressor system with normally-open valves in oil balancing connections

Abstract

The multi-compressor system (7) has a plurality of parallelly coupled compressors (8); inlet connection lines (15) each connected to a refrigerant suction fitting of a respective compressor (8); outlet connection lines (17) each connected to a refrigerant discharge fitting of a respective compressor (8); a common oil balancing line (18) and balancing connection lines (19) each connecting the common oil balancing line (18) to an oil balancing connection (21) of a respective compressor (8); and spring-loaded normally-open valves (25) each being arranged within a respective balancing connection line (19) or within an oil balancing connection (21) of a respective compressor (8) and each being configured to close when a pressure difference between a pressure prevailing in the low pressure volume of the respective compressor (8) and a pressure prevailing in the common oil balancing line (18) reaches a predetermined value.

Claims

1. A multi-compressor system comprising: a plurality of compressors which are parallelly coupled, the plurality of compressors comprising at least two compressors, each compressor including a compressor shell provided with a refrigerant suction fitting, a refrigerant discharge fitting and an oil balancing connection, each oil balancing connection being fluidly connected to a low pressure volume of the respective compressor, a common suction line and inlet connection lines each connecting the common suction line to the refrigerant suction fitting of a respective compressor, a common discharge line and outlet connection lines each connecting the common discharge line to the refrigerant discharge fitting of a respective compressor, a common oil balancing line and balancing connection lines each connecting the common oil balancing line to the oil balancing connection of a respective compressor, and a plurality of spring-loaded normally-open valves each associated with a respective compressor, each spring-loaded normally-open valve being configured to occupy an open configuration in which said spring-loaded normally-open valve fluidly connects the low pressure volume of the respective compressor with the common oil balancing line and a closed configuration in which said spring-loaded normally-open valve at least partially fluidly isolates the low pressure volume of the respective compressor from the common oil balancing line, each spring-loaded normally-open valve being configured to be displaced in the closed configuration when a pressure difference between a pressure prevailing in the low pressure volume of the respective compressor and a pressure prevailing in the common oil balancing line reaches a predetermined value.

2. The multi-compressor system according to claim 1, wherein the predetermined value is between 5 and 15 mbar.

3. The multi-compressor system according to claim 1, wherein each spring-loaded normally-open valve is arranged within a respective balancing connection line or within an oil balancing connection of a respective compressor.

4. The multi-compressor system according to claim 1, wherein each oil balancing connection includes an oil sump port provided on the compressor shell of the respective compressor and an oil balancing fitting connected to the respective oil sump port, each balancing connection line being connected to a respective oil balancing fitting.

5. The multi-compressor system according to claim 4, wherein at least one of the spring-loaded normally-open valve is arranged within the oil sump port of the respective compressor.

6. The multi-compressor system according to claim 4, wherein at least one of the spring-loaded normally-open valve is arranged within the oil balancing fitting of the respective compressor.

7. The multi-compressor system according to claim 1, wherein at least one of the balancing connection line includes a first tubular connecting part connected to the common oil balancing line, and a second tubular connecting part connected to the oil balancing connection of a respective compressor, the respective spring-loaded normally-open valve being interposed between said first and second tubular connecting parts.

8. The multi-compressor system according to claim 1, wherein each spring-loaded normally-open valve includes: a fluid flow passage, a valve seat surrounding the respective fluid flow passage, and a valve member movable between a closed position in which the valve member bears against the respective valve seat and at least partially closes the respective fluid flow passage and an open position in which the valve member is remote from the respective valve seat and clears the respective fluid flow passage.

9. The multi-compressor system according to claim 8, wherein each valve member includes an oil passage hole configured to avoid an excessive oil accumulation within an oil sump of the respective compressor when said compressor is off.

10. The multi-compressor system according to claim 9, wherein each oil passage hole is arranged in a lower portion of the respective valve member.

11. The multi-compressor system according to claim 8, wherein each spring-loaded normally-open valve further includes a mounting part provided with the respective valve seat and attached to the respective balancing connection line or to the respective oil balancing connection.

12. The multi-compressor system according to claim 8, wherein each valve member is pivotally mounted around a pivot axis.

13. The multi-compressor system according to claim 1, wherein each compressor of the plurality of compressors is a scroll compressor.

14. A refrigeration system comprising a refrigerant circulation circuit successively including a condenser, an expansion device, an evaporator and a multi-compressor system according to claim 1 connected in series.

15. The multi-compressor system according to claim 2, wherein each spring-loaded normally-open valve is arranged within a respective balancing connection line or within an oil balancing connection of a respective compressor.

16. The multi-compressor system according to claim 2, wherein each oil balancing connection includes an oil sump port provided on the compressor shell of the respective compressor and an oil balancing fitting connected to the respective oil sump port, each balancing connection line being connected to a respective oil balancing fitting.

17. The multi-compressor system according to claim 3, wherein each oil balancing connection includes an oil sump port provided on the compressor shell of the respective compressor and an oil balancing fitting connected to the respective oil sump port, each balancing connection line being connected to a respective oil balancing fitting.

18. The multi-compressor system according to claim 5, wherein at least one of the spring-loaded normally-open valve is arranged within the oil balancing fitting of the respective compressor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0081] The following detailed description of three embodiments of the invention is better understood when read in conjunction with the appended drawings being understood, however, that the invention is not limited to the specific embodiments disclosed.

[0082] FIG. 1 is a diagrammatic view of a refrigeration system including a multi-compressor system according to a first embodiment of the invention.

[0083] FIG. 2 is a perspective view of the multi-compressor system of FIG. 1.

[0084] FIG. 3 is perspective view of the multi-compressor system of FIG. 1 in which one compressor is sectioned along a section plan extending through a respective oil sump port.

[0085] FIG. 4 is an enlarged view of a detail of FIG. 3.

[0086] FIG. 5 is a front perspective view of a spring-loaded normally-open valve of the multi-compressor system of FIG. 1.

[0087] FIG. 6 is a rear perspective view of the spring-loaded normally-open valve of FIG. 5.

[0088] FIG. 7 is a cross section view of the spring-loaded normally-open valve of FIG. 5.

[0089] FIG. 8 is a partial cross section view of a multi-compressor system according to a second embodiment of the invention.

[0090] FIG. 9 is a partial cross section view of a multi-compressor system according to a third embodiment of the invention.

DETAILED DESCRIPTION

[0091] FIG. 1 describes a refrigeration system 2 comprising a refrigerant circulation circuit 3 successively including a condenser 4, an expansion device 5, an evaporator 6 and a multi-compressor system 7 connected in series.

[0092] The multi-compressor system 7 includes a plurality of compressors 8 which are parallelly coupled. The plurality of compressors comprises at least three compressors 8, and for example four compressors 8.

[0093] Each compressor 8 includes a compressor shell 9 provided with a refrigerant suction fitting 11 configured to supply the respective compressor 8 with refrigerant gas to be compressed and a refrigerant discharge fitting 12 configured to discharge compressed refrigerant gas.

[0094] Advantageously, each compressor 8 is a scroll compressor, and includes a compression unit (not shown on the figures) disposed inside the respective compressor shell 9 and configured to compress the refrigerant gas supplied by the respective refrigerant suction fitting 11. Each compression unit includes a fixed scroll, which is fixed in relation to the respective compressor shell 9, and an orbiting scroll configured to perform an orbiting movement relative to the respective fixed scroll during operation of the respective compressor 8.

[0095] Furthermore, each compressor 8 includes a drive shaft (not shown on the figures) which is vertically orientated and which is configured to drive the respective orbiting scroll in an orbital movement, and an electric motor (not shown on the figures) arranged within the respective compressor shell 9 and coupled to the respective drive shaft so as to drive in rotation the respective drive shaft about a rotation axis. Each compressor 8 of the plurality of compressors may have a variable capacity, and may for example include an electric motor having a variable speed. However, each compressor 8 of the plurality of compressors may have a fixed capacity, and for example may include an electric motor having a fixed speed.

[0096] Each compressor 8 also includes an oil sump 13 located at a lower portion of the respective compressor shell 9.

[0097] The multi-compressor system 7 further includes a common suction line 14 and inlet connection lines 15 each connecting the common suction line 14 to the refrigerant suction fitting 11 of a respective compressor 8. As shown on FIG. 2, the inlet connection lines 15 have identical dimensions and may have identical flow restrictions. Advantageously, the inlet connection lines 15 are substantially identical and extend horizontally.

[0098] The multi-compressor system 7 also includes a common discharge line 16 and outlet connection lines 17 each connecting the common discharge line 16 to the refrigerant discharge fitting 12 of a respective compressor 8. As shown on FIG. 2, the outlet connection lines 17 have identical dimensions. Advantageously, the outlet connection lines 17 are substantially identical and extend horizontally.

[0099] Furthermore, the multi-compressor system 7 includes a common oil balancing line 18 and balancing connection lines 19, also named balancing branch lines, each connecting the common oil balancing line 18 to an oil balancing connection 21 provided on the compressor shell 9 of a respective compressor 8. The common oil balancing line 18 and the balancing connection lines 19 are particularly configured to fluidly connect low pressure volumes of the compressors 8, and particularly the oil sumps 13 of said compressors 8, and thus to allow oil to flow between the compressors 8 and to balance the oil levels within the compressors 8. Advantageously, the common oil balancing line 18 and the balancing connection lines 19 extend horizontally, and all of the oil balancing connections 21 are approximately at the same vertical elevation with respect to a bottom of the respective compressor shell 9.

[0100] As better shown on FIG. 4, each oil balancing connection 21 includes an oil sump port 22 provided on the compressor shell 9 of the respective compressor 8, and an oil balancing fitting 23 connected to the respective oil sump port 22 and to which is connected the respective balancing connection line 19. Each oil balancing fitting 23 is tubular and includes a first fitting end portion 23.1 connected to the respective oil sump port 22 and a second fitting end portion 23.2 located away from the respective oil sump port 22.

[0101] According to the embodiment shown on FIGS. 1 to 7, each balancing connection line 19 includes a tubular connecting part 24 including a first end portion 24.1 connected to the common oil balancing line 18 and a second end portion 24.2 connected to the respective oil balancing fitting 23.

[0102] The multi-compressor system 7 also includes spring-loaded normally-open valves 25 which are each arranged within an oil balancing connection 21 of a respective compressor 8. Each spring-loaded normally-open valve 25 is configured to open when the respective compressor 8 is running, such that the low pressure volume of the respective compressor 8 is fluidly connected to the common oil balancing line 18. Each spring-loaded normally-open valve 25 is configured to close when the respective compressor 8 is off while at least one of the other compressor 8 is running, such that the low pressure volume of the respective compressor 8 is at least partially fluidly isolated from the common oil balancing line 18 (in other words, the communication between the low pressure volume of the respective compressor 8 and the common oil balancing line 18 is cut off).

[0103] As better shown on FIGS. 4 to 7, each spring-loaded normally-open valve 25 includes a mounting part 26 attached to the respective oil balancing connection 21, and provided with a fluid flow passage 27 and a valve seat 28 surrounding the respective fluid flow passage 27. Advantageously, each mounting part 26 is annular.

[0104] According to the embodiment shown on FIGS. 1 to 7, the mounting part 26 of each spring-loaded normally-open valve 25 is inserted in the oil sump port 22 of the respective compressor 8, and is configured to bear against an axial end surface of the respective oil balancing fitting 23. The mounting part 26 of each spring-loaded normally-open valve 25 may be for example firmly fitted in the oil sump port 22 of the respective compressor 8.

[0105] Each spring-loaded normally-open valve 25 further includes a valve member 29 movable between a closed position in which the valve member 29 bears against the respective valve seat 28 and closes the respective fluid flow passage 27 and an open position in which the valve member 29 is remote from the respective valve seat 28 and clears the respective fluid flow passage 27. Each valve member 29 particularly includes a first face configured to be oriented towards the respective valve seat 28 and a second face opposite to the respective first face.

[0106] According to the embodiment shown on FIGS. 1 to 7, each valve member 29 has a disc shape, and is pivotally mounted around a pivot axis A which advantageously extends substantially horizontally.

[0107] Each spring-loaded normally-open valve 25 further includes a support shaft 31 configured to support the respective valve member 29 and to which is non-rotatably secured an upper portion of the respective valve member 29, said support shaft 31 being pivotally mounted to the respective mounting part 26 around the respective pivot axis A.

[0108] Each spring-loaded normally-open valve 25 also includes a spring member 32, such as a torsion spring, configured to bias the respective valve member 29 towards its open position.

[0109] According to the embodiment shown on FIGS. 1 to 7, each spring member 32 includes: [0110] a first end part 32.1, such as a first end branch, configured to cooperate with the respective mounting part 26, [0111] a second end part 32.2, such as a second end branch, configured to cooperate with the respective valve member 29, and particularly with the first face of the respective valve member 29 which is oriented towards the respective valve seat 28, and [0112] an intermediate portion 32.3 surrounding the respective support shaft 31.

[0113] According to the embodiment shown on FIGS. 1 to 7, each mounting part 26 advantageously includes a fixing notch 33 in which is received the first end part 32.1 of the respective spring member 32.

[0114] The valve member 29 of each spring-loaded normally-open valve 25 is particularly configured to be moved into its closed position when a pressure difference between a pressure prevailing in the low pressure volume of the respective compressor 8 and a pressure prevailing in the common oil balancing line 18 reaches a predetermined value which is between 5 and 15 mbar, and for example 10 mbar.

[0115] During part-load operation of the multi-compressor system 7, at least one compressor 8 is stopped (while the other compressors 8 are running) and the pressure within the low pressure volume of said compressor 8 will rise. When a pressure difference between a pressure prevailing in the low pressure volume of said non-operating compressor 8 and a pressure prevailing in the common oil balancing line 19 reaches the predetermined value, the pressure prevailing in the low pressure volume of said non-operating compressor 8 overcomes the opening force of the spring member 32 of the respective spring-loaded normally-open valve 25 such that the valve member 29 of said spring-loaded normally-open valve 25 is moved in its closed position and fluidly isolates the non-operating compressor from the common oil balancing line 18.

[0116] Hereby, a creation of bypass flows of suction gas through the balancing connection line 19 connected to said non-operating compressor 8 is prevented, and good equalization of oil level within the oil sumps 13 of operating compressors 8 is assured. Therefore, the multi-compressor system 7 according to the present invention ensures good oil balancing properties at reduced costs.

[0117] According to the embodiment shown on FIGS. 1 to 7, each valve member 29 includes an oil passage hole 34 arranged in a lower portion of the respective valve member 29. Such an oil passage hole 34 ensures an oil flow from the respective compressor 8 when said compressor 8 is off, and. Thus, the oil passage hole 34 provided on each valve member 29 is configured to avoid an excessive oil accumulation within the oil sump 13 of the respective compressor 8 when said compressor 8 is off.

[0118] The multi-compressor system 7 also includes a controller 35 configured to control operation of the multi-compressor system 7, i.e. to control operation (starting or stopping) of the plurality of compressors and particularly to control which compressor(s) 8 of the plurality of compressors is(are) in operation. The controller 35 may for example includes a microprocessor and a memory.

[0119] Particularly, the controller 35 is configured to operate the multi-compressor system 7 according to a plurality of predetermined operating configurations. The predetermined operation configurations comprise specific on/off configurations of said compressors 8 depending on the required load, i.e. the required output capacity. Advantageously, each predetermined operating configuration is configured to result in a predetermined output capacity for the multi-compressor system 7, and the controller 35 is configured to control the plurality of compressors in response to a required output capacity for the multi-compressor system 7. Particularly, the controller 35 is configured to select a predetermined operating configuration, among the plurality of predetermined operating configurations, that corresponds to the required output capacity for the multi-compressor system 7.

[0120] The plurality of predetermined operating configurations notably includes: [0121] part-load operation configurations where at least one of the compressors 8 is stopped while all the other compressors 8 of the plurality of compressors are running; [0122] part-load operation configurations where at least two compressors 8 are stopped while all the other compressors 8 of the plurality of compressors are running; and [0123] a full-load operation configuration where all the compressors 8 of the plurality of compressors are running.

[0124] FIG. 8 represents a multi-compressor system 7 according to a second embodiment of the invention which differs from the embodiment shown on FIGS. 1 to 7 essentially in that the mounting part 26 of each spring-loaded normally-open valve 25 is arranged at the second fitting end portion 23.2 of the oil balancing fitting 23 of the respective compressor 8. Advantageously, the mounting part 26 of each spring-loaded normally-open valve 25 is configured to bear against an axial end surface of the second end portion 24.2 of the respective tubular connecting part 24.

[0125] FIG. 9 represents a multi-compressor system 7 according to a third embodiment of the invention which differs from the embodiment shown on FIGS. 1 to 7 essentially in that each spring-loaded normally-open valve 25 is arranged outside the compressor shell 9 of the respective compressor 8, and particularly within a respective balancing connection line 19.

[0126] According to said third embodiment of the invention, each balancing connection line 19 includes a first tubular connecting part 36 connected to the common oil balancing line 18, and a second tubular connecting part 37 connected to the oil balancing connection 21 of a respective compressor 8, the mounting part 26 of the respective spring-loaded normally-open valve 25 being interposed between said first and second tubular connecting parts 36, 37.

[0127] According to another embodiment of the invention not shown on the figures, each valve member 29 may be slidably mounted along a displacement direction (for example substantially parallel to a central axis of the respective oil balancing connection 21) and between its open and closed positions. According to such an embodiment of the invention, each spring-loaded normally-open valve 25 may include at least one guiding member, for example a guiding rod, configured to guide the respective valve member 29 between its open and closed positions.

[0128] Of course, the invention is not restricted to the embodiments described above by way of non-limiting examples, but on the contrary it encompasses all embodiments thereof.