OIL DISTRIBUTION SYSTEM FOR MULTIPLE-COMPRESSOR SYSTEMS

Abstract

A compressor system includes a suction manifold, an oil manifold, a first compressor fluidly connected to the suction manifold, selectively connectable to the oil manifold, and including a first oil separator, a second compressor fluidly connected to the suction manifold, selectively connectable to the oil manifold, and a second oil separator, and a controller connected in communication with each of the first compressor and the second compressor. The controller determines an oil level within each of the first and second compressors, determines that an oil level within one of the first and second compressors is below a predetermined threshold value, and transfers oil from the other of the first and second compressors having an oil level that is below the predetermined threshold value to the compressor of the first and second compressors having an oil level that is below the predetermined threshold value.

Description

FIELD

The field of the disclosure relates generally to climate-control systems, and more particularly, to oil distribution systems for multiple compressors used in climate-control systems.

BACKGROUND

A climate-control system such as, for example, a heat-pump system, a refrigeration system, or an air conditioning system, may include a fluid circuit having an outdoor heat exchanger, an indoor heat exchanger, an expansion device disposed between the indoor and outdoor heat exchangers, and one or more compressors circulating a working fluid (e.g., refrigerant or carbon dioxide) between the indoor and outdoor heat exchangers. Compressors may be lubricated by oil, which is circulated to various compressor components. When a compressor operates, small amounts of oil may be pumped out of the compressor along with the compressed refrigerant. Some compressors, such as for example, those circulating carbon dioxide as the working fluid, may operate at a pressure that is higher than compressors circulating other working fluids, needing a higher concentration of oil flowing through the components of the compressor to provide proper lubrication.

As can be appreciated, too much oil flow through the refrigeration system (e.g., the condenser, etc.) may cause inefficient operation of the refrigeration system. Thus, compressors may include oil separators to remove oil from the working fluid. The oil separator may include an oil sump storing the oil separated from the working fluid to lubricate the compressor while allowing the working fluid to flow through the refrigeration system. However, during operation of a multiple-compressor system, an oil level in one or more of the compressors may decrease while an oil level in another one of the compressors may increase. Therefore, there is a need for systems and methods for equalizing and maintaining adequate oil levels in each compressor within a multiple-compressor system to improve efficiency and reliability of the compressors to effectively and efficiently provide a cooling and/or heating effect on demand.

This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

SUMMARY

In one aspect, a compressor system includes a suction manifold, an oil manifold, a first compressor fluidly connected to the suction manifold, selectively connectable to the oil manifold, and including a first oil separator receiving fluid from the suction manifold, a second compressor fluidly connected to the suction manifold, selectively connectable to the oil manifold, and including a second oil separator receiving fluid from the suction manifold, and a controller connected in communication with each of the first compressor and the second compressor. The controller includes a processor and a memory. The memory stores instructions that program the processor to determine an oil level within each of the first compressor and the second compressor, determine that an oil level within one of the first compressor and the second compressor is below a predetermined threshold value, and transfer oil from the other of the first compressor and the second compressor having an oil level that is below the predetermined threshold value to the compressor of the first compressor or the second compressor having an oil level that is below the predetermined threshold value.

In another aspect, an oil distribution system is for use with a plurality of compressors. Each compressor of the plurality of compressors including an oil separator, an oil sump, an oil level sensor operably connected to the oil sump, a suction port, and an oil outlet port fluidly connected to the oil sump. The oil distribution system includes an oil manifold fluidly connected to each oil outlet port of the plurality of compressors, a plurality of oil outlet valves, a plurality of oil inlet valves, and a controller connected in communication with each oil level sensor, each oil outlet valve, and each oil inlet valve. Each oil outlet valve fluidly connects a respective oil outlet port of the plurality of compressors to the oil manifold and is positionable between a closed position and an open position. Each oil inlet valve fluidly connects the oil manifold to a respective suction port of the plurality of compressors and is positionable between a closed position and an open position. The controller includes a processor and a memory. The memory stores instructions that program the processor to determine that an oil level of a compressor of the plurality of compressors is below a predetermined threshold value based on signals received from each oil level sensor of the plurality of compressors, identify a compressor of the plurality of compressors with the highest oil level based on signals received from each oil level sensor of the plurality of compressors, open the oil inlet valve associated with the compressor having an oil level that is below the predetermined threshold value, and open the oil outlet valve associated with the compressor having the highest oil level to transfer oil from the compressor having the highest oil level to the compressor having an oil level that is below the predetermined threshold value.

In yet another aspect, a method of distributing oil in a multiple compressor system, the multiple compressor system including a plurality of compressors, each compressor of the plurality of compressors including an oil separator separating oil from fluid flowing through the compressor, includes determining that an oil level of a compressor of the plurality of compressors is below a predetermined threshold value based on signals received from an oil level sensor of each compressor of the plurality of compressors, identifying a compressor of the plurality of compressors with a highest oil level based on signals received from each oil level sensor of the plurality of compressors, open an oil inlet valve associated with the compressor having an oil level that is below the predetermined threshold value, and open an oil outlet valve associated with the compressor having the highest oil level to transfer oil from the compressor having the highest oil level to the compressor having an oil level that is below the predetermined threshold value.

Various refinements exist of the features noted in relation to the above-mentioned aspects of the present disclosure. Further features may also be incorporated in the above-mentioned aspects of the present disclosure as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to any of the illustrated embodiments of the present disclosure may be incorporated into any of the above-described aspects of the present disclosure, alone or in any combination.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an example multiple compressor system;

FIG. 2 is a schematic diagram of an example rack of compressors of the multiple compressor system, showing an oil level of each compressor of the rack of compressors above a predetermined threshold;

FIG. 3 is a schematic diagram of another embodiment of a compressor of the multiple compressor system of FIG. 1;

FIG. 4 is a block diagram of a control system for the multiple compressor system of FIG. 1;

FIG. 5 is a schematic diagram of the rack of compressors of FIG. 2, showing a compressor of the rack of compressors with an oil level below the predetermined threshold;

FIG. 6A is a flow diagram of an example method of operating a multiple compressor system;

FIG. 6B is a continuation of the flow diagram of FIG. 6A; and

FIG. 6C is a continuation of the flow diagram of FIG. 6B.

Corresponding reference characters indicate corresponding parts throughout the drawings.

DETAILED DESCRIPTION

For conciseness, examples will be described with respect to a multiple compressor system including an oil distribution system operable to distribute oil between a plurality of compressors. The oil distribution system eliminates the need for a single, centralized oil separator by replacing the single, centralized oil separator with internal oil separators in each compressor of the multiple compressor system. By using internal oil separators in each compressor, the oil distribution system controls the oil level within each compressor using valves and sensors controllable by a controller, in addition to, or in lieu of systems and methods utilizing pressure to balance oil levels within each compressor, by transferring oil between each compressor to reduce or increase an amount of oil in each compressor individually. The oil distribution system enables multiple compressor systems utilizing carbon dioxide as a working fluid to balance the relatively higher amount of oil needed as compared to multiple compressor systems utilizing other types of working fluids. For example, compressor systems utilizing carbon dioxide as a working fluid may require about 5% oil by weight to create and/or maintain a seal in the compressors due to the relatively higher pressures utilized in carbon dioxide refrigeration systems as compared to refrigeration systems utilizing other types of refrigerants or working fluid.

Referring to FIG. 1, a multiple-compressor system is illustrated and generally identified by reference numeral 10. It is envisioned that the multiple compressor system 10 may be, or may be integrated with, a heating, ventilation, and air conditioning (HVAC) system, a refrigeration system (which may include transportation refrigeration systems), and/or a heat pump without departing from the scope of the disclosure.

In the example embodiment, the multiple compressor system 10 includes a single, closed refrigerant loop 12 that includes a first heat exchanger 14 (e.g., a condenser or a gas cooler), an expansion device 16 (e.g., an expansion valve, a capillary tube, etc.), a second heat exchanger 18 (e.g., an evaporator), and a rack of compressors 100. In the example embodiment, the rack of compressors 100 includes a first compressor 102, a second compressor 202, and a third compressor 302, although the rack of compressors 100 may include any number of compressors without departing from the scope of the disclosure.

With additional reference to FIG. 2, each of the first compressor 102, the second compressor 202, and third compressor 302 may be a high-side compressor (e.g., a compressor in which the motor assembly is disposed within a discharge-pressure chamber within the shell), for example, and may be any suitable type of compressor, such as, for example, a scroll compressor, a rotary compressor, and a reciprocating or screw compressor. Each of the first compressor 102, the second compressor 202, and the third compressor 302 defines a shell 104, 204, and 304, each defining a discharge-pressure chamber 106, 206, and 306 in which a motor 108, 208, 308 is disposed and an oil sump 112, 212, and 312 in which lubricant or oil 114, 214, and 314 is retained. In the example embodiment, each of the first compressor 102, the second compressor 202, and the third compressor 302 includes an oil separator 110, 210, and 310. Although illustrated as having an integrated or internal oil separator 110, 210, and 310, and an internal oil sump 112, 212, and 312, any one of the first compressor 102, the second compressor 202, and the third compressor 302 may include an external oil separator (not shown) and/or an external oil sump (not shown). In the example embodiment, the oil separators 110, 210, and 310 are a baffle separator, causing oil within the working fluid passing through the oil separators 110, 210, and 310 to be entrapped and flow into a respective oil sump 112, 212, and 312. Although generally described as being a baffle separator, it is envisioned that any one of the oil separators 110, 210, and 310 may be any suitable type of oil separator without departing from the scope of the disclosure.

The first compressor 102, the second compressor 202, and the third compressor 302 each define a suction port 116, 216, and 316 and a discharge port 118, 218, 318. The suction ports 116, 216, and 316 may provide fluid to a compression mechanism 120, 220, and 320 operably connected to a respective motor 108, 208, and 308. Each suction port 116, 216, and 316 is fluidly connected to a suction line 122, 222, and 322 of each respective compressor 102, 202, and 302. Each suction line 122, 222, and 322 is fluidly connected to a suction manifold 20. The suction manifold 20 is fluidly connected to the second heat exchanger 18 and delivers working fluid from the second heat exchanger 18 to each suction line 122, 222, and 322. In this manner, the working fluid exiting the second heat exchanger 18 may flow into each of the first compressor 102, the second compressor 202, and the third compressor 302 via a respective suction line 122, 222, and 322 and suction port 116, 216, and 316 to be compressed by the compression mechanisms 120, 220, and 320. After the working fluid is compressed by the compression mechanisms 120, 220, and 320 the working fluid is discharged from each of the first compressor 102, the second compressor 202, and the third compressor 302 via a respective discharge port 118, 218, and 318 and to a discharge line 124, 224, and 324 fluidly coupling each respective discharge port 118, 218, and 318 to a discharge manifold 22. The discharge manifold 22 is fluidly connected to the first heat exchanger 14 to transfer the compressed working fluid from each compressor 102, 202, and 302 to the first heat exchanger 14.

With continued reference to FIGS. 1 and 2, the rack of compressors 100 includes an oil distribution system for balancing and oil level within each compressor of the rack of compressors and/or inhibiting overfilling or oil starvation within each compressor of the rack of compressors 100.

Each of the first compressor 102, the second compressor 202, and the third compressor 302 includes an oil outlet port 126, 226, and 326 fluidly connected to a respective oil sump 112, 212, and 312. Each oil outlet port 126, 226, and 326 is fluidly connected to a respective oil outlet valve 128, 228, and 328, and each oil outlet valve 128, 228, and 328 is fluidly connected to an oil manifold 160. Each oil outlet valve 128, 228, and 328 is operable between a first, closed position, where oil 114, 214, and/or 314 is inhibited from flowing from a respective oil sump 112, 212, and 312 to the oil manifold 160, and a second, open position, where oil 114, 214, and/or 314 is permitted to flow from a respective oil sump 112, 212, and 312 to the oil manifold 160. In the example embodiment, each oil outlet valve 128, 228, and 328 is fluidly connected to the oil manifold 160 by a respective oil outlet line 130, 230, and 330. The oil outlet valves 128, 228, and 328 may be any suitable type of valve, such as a ball valve, a butterfly valve, a slide valve, etc. and may be electrically (e.g., a solenoid, a stepper motor, a servo, etc.) or mechanically controlled (e.g., pressure actuated, lever actuated, etc.). Each of the oil outlet valves 128, 228, and 328 may be the same type of valve or may be different than one another without departing from the scope of the disclosure.

Each of the first compressor 102, the second compressor 202, and the third compressor 302 includes an oil inlet valve 132, 232, and 332. Each oil inlet valve 132, 232, and 332 fluidly connects a respective suction port 116, 216, and 316 to the oil manifold 160. Each oil inlet valve 132, 232, and 332 is operable between a first, closed position, where oil is inhibited from flowing from the oil manifold to a respective suction port 116, 216, and 316, and a second, open position, where oil is permitted to flow from the oil manifold 160 to a respective suction port 116, 216, and 316. In the example embodiment, each oil inlet valve 132, 232, and 332 is fluidly connected to an oil inlet line 134, 234, and 334. The oil inlet valves 132, 232, and 332 may be any suitable type of valve, such as a ball valve, a butterfly valve, a slide valve, etc. and may be electrically (e.g., a solenoid, a stepper motor, a servo, etc.) or mechanically controlled (e.g., pressure actuated, lever actuated, etc.). Each of the oil inlet valves 132, 232, and 332 may be the same type of valve or may be different than one another without departing from the scope of the disclosure.

Each of the first compressor 102, the second compressor 202, and the third compressor 302 includes an oil level sensor 136, 236, and 336 operably connected to a respective shell 104, 204, and 304. Although generally described as being operably connected to the shell 104, 204, and 304, one or more of the oil level sensors 136, 236, and 336 may be disposed at any location, which may be remote from the shell 104, 204, and/or 304, and may be operably connected to any portion of the first compressor 102, the second compressor 202, and the third compressor 302. Each oil level sensor 136, 236, and 336 measures and/or identifies an oil level within each oil sump 112, 212, and 312.

In some embodiments, at least one of or each of the first compressor 102, the second compressor 202, and the third compressor 302 may be a low-side compressor (e.g., a compressor in which the motor assembly is disposed within a suction-pressure chamber (not shown) within the shell) or an intermediate pressure compressor (e.g., a two stage and/or series-rotary compressor). In embodiments, at least one of or each of the first compressor 102, the second compressor 202, and the third compressor 302 may have different capacities than one another and may include a fixed-speed or a variable-speed motor 108, 208, and 308.

With reference to FIG. 3, an embodiment of the rack of compressors 100 utilizing intermediate pressure compressors is illustrated. In the example embodiment, the intermediate pressure compressor 102-A is substantially similar to the first compressor 102, and therefore, will not be described in detail herein in the interest of brevity. The intermediate pressure compressor 102-A defines a shell 104-A in which a motor 108-A is disposed and an oil separator 110-A. The intermediate pressure compressor 102-A defines an oil sump 112-A in which a lubricant or oil 114-A is retained. The intermediate pressure compressor 102-A defines a suction port 116-A and a discharge port 118-A. The suction port 116-A is fluidly connected to a suction line 122-A. The suction line 122-A is fluidly connected to the suction manifold 20 to deliver working fluid to the intermediate pressure compressor 102-A. After the working fluid is compressed, the working fluid is discharged through a discharge port 118-A and to the discharge manifold 22.

The intermediate pressure compressor 102-A includes an oil outlet port 126-A fluidly connected to the oil sump 112-A. The oil outlet port 126-A is fluidly connected to an oil outlet valve 128-A and the oil outlet valve 128-A is fluidly connected to an oil manifold 160-A. The intermediate pressure compressor 102-A includes an oil inlet valve 132-A. The oil inlet valve 132-A fluidly connects the suction port 116-A to the oil manifold 160-A. The intermediate pressure compressor 102-A includes an oil level sensor 136-A operably connected to the shell 104-A.

Turning to FIG. 4, a block diagram of a control system of the multiple compressor system 10 is illustrated. The rack of compressors 100 is operatively connected to a controller or control module 170 to control operation of the rack of compressors 100 based in part on the measured parameters described above. The controller 170 includes at least one processor 172 and at least one memory 174. The memory 174 stores instructions or an algorithm 176 that program the processor 172 to determine whether one or more compressors of the rack of compressors 100 requires more oil by performing one or more calculations, determinations, and functions, which will be described in greater detail further below. The memory 174 stores an application 178, which includes a user interface 180 configured to output (e.g., display) and/or receive information (e.g., from a user) associated with the multiple compressor system 10. In some embodiments, the user interface 180 is configured to receive an activation and/or deactivation input from a user to activate and deactivate (e.g., turn on and off) or otherwise enable operation of the multiple compressor system 10. In some embodiments, the user interface 180 is configured to output information associated with one or more operational characteristics of the multiple compressor system 10, including, without limitation, warning indicators such as severity alerts, occurrence alerts, fault alerts, motor speed alerts, low oil level alerts, and any other suitable information.

The user interface 180 may interface with any suitable input devices and output devices that enable the user interface 180 to function as desired herein. For example, controller 170 may include an input module 190 operatively connected to one or more input devices including, but not limited to, a keyboard, a mouse, a touchscreen, joystick(s), throttle(s), buttons, and/or switches. The controller 170 may include an output module 192 operatively connected to one or more output devices including, but not limited to, a display (e.g., a liquid crystal display (LCD) or an organic light emitting diode (OLED) display), speakers, indicator lights, and instruments. In one non-limiting embodiment, the user interface 180 may be part of a different component, such as a system controller (not shown). Other embodiments do not include a user interface 180. The controller 170 is generally configured to control operation of the multiple compressor system 10. In some embodiments, the controller 170 receives user input from the user interface 180, and controls one or more components of the multiple compressor system 10 in response to such user inputs. For example, the controller 170 may control one or more of the motors 108, 208, and 308 based on user input received from the user interface 180. Additionally, the controller 170 may control operation of one or more of the oil outlet valves 128, 228, and 328 and oil inlet valves 132, 232, and 332 based on user input received from the user interface 180.

In some embodiments, the multiple compressor system 10 may be controlled by a remote-control interface. For example, the controller 170 may include a network interface 182 configured to communicatively connect the controller 170 to the rack of compressors 100, one or more other components or modules of the multiple compressor system 10, and/or other controllers, modules, or computers. In some embodiments, the network interface 182 enables the controller 170 to communicate to a variety of other devices and systems via the Internet via a wired or wireless connection. Additionally, or alternatively, the communication may be via an ad-hoc Bluetooth® or wireless network enabling communication with a wide-area network (WAN) and/or a local area network (LAN). The network interface 182 may connect to the Internet via one or more gateways, routers, and network address translation (NAT) devices. The network interface 182 may communicate with a cloud storage system 184, in which further applications and/or data may be stored. The cloud storage system 184 may be remote from or on the premises of the multiple compressor system 10 such as in a control room or an information technology room. In some embodiments, the network interface 182 may be embodied on a portable computing device, such as a tablet or a smartphone.

The controller 170 may generally include any suitable computer and/or other processing unit, including any suitable combination of computers, processing units, and/or the like that may be operated independently or in connection with one another (e.g., the controller 170 may form all or part of a controller network). The controller 170 may include one or more modules or devices, one or more of which is enclosed within the multiple compressor system 10 and/or the rack of compressors 100 or may be located remote from the multiple compressor system 10. The controller 170 may be part of one of the compressors of the rack of compressors 100 or separate and may be part of a system controller in an HVAC system. The controller 170 and/or components of the controller 170 may be integrated or incorporated within other components of the multiple compressor system 10.

As used herein, the term “processor” refers not only to integrated circuits, but also to a controller, a microcontroller, a microcomputer, a programable logic computer (PLC), an application-specific integrated circuit, and other programmable circuits. Additionally, the at least one memory 174 of the controller 170 may generally be or include memory element(s) including, but not limited to, computer readable medium (e.g., random access memory (RAM)), computer readable non-volatile medium (e.g., a flash memory), a floppy disk, a compact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), a digital versatile disc (DVD), and/or other suitable memory elements. Such memory devices 174 may generally be configured to store suitable computer-readable instructions that, when implemented by the processor(s) 172, configure or cause the controller to perform various functions described herein, including, but not limited to, controlling the multiple compressor system 10, controlling operation of the motors 108, 208, and 308, receiving inputs from the user interface 180, providing output to an operator via the user interface 180, controlling the oil outlet valves 128, 228, and 328 and oil inlet valves 132, 232, and 332, and/or various other suitable computer-implemented functions.

Referring back to FIG. 2 and with additional reference to FIGS. 4 and 5, the controller 170 distributes oil between each oil sump 112, 212, and 312 of the first compressor 102, the second compressor 202, and the third compressor 302. This transfer of oil enables the controller 170 to inhibit oil starvation and/or overfilling of the oil sumps 112, 212, and/or 312.

The controller 170 receives a signal from each oil level sensor 136, 236, and 336. The algorithm 176 stored on the memory 174 identifies an oil level within each oil sump 112, 212, and 312. The algorithm 176 identifies a compressor of the first compressor 102, the second compressor 202, and the third compressor 302 that has the highest oil level and compares the identified oil levels to a minimum predetermined threshold value (e.g., a minimum oil level within the oil sump 112, 212, and 312). If one or more of the identified oil levels is below the minimum predetermined threshold value, the algorithm 176 causes the processor 172 to instruct the oil outlet valve 128, 228, and/or 328 corresponding to the compressor 102, 202, and/or 302 having the highest oil level to transition from the first, closed position, to the second open position to permit oil 114, 214, and/or 314 within the oil sump 112, 212, and/or 312 to flow into the oil manifold 160 (FIG. 5). The algorithm 176 causes the processor 172 to instruct the oil inlet valve 132, 232, and/or 332 corresponding to the one or more compressors 102, 202, and/or 302 having an oil level that is below the minimum predetermined threshold value to transition from the first, closed position, to the second, open position to permit oil within the oil manifold 160 to flow into the corresponding suction port 116, 216, and/or 316 (FIG. 5).

In some embodiments, the controller 170 monitors or otherwise determines the oil level within each of the oil sumps 112, 212, and 312 and compares the determined oil levels to the minimum predetermined threshold value. When the oil level within one or more of the oil sumps 112, 212, and/or 312 is above the minimum predetermined threshold value, the algorithm 176 causes the processor 172 to instruct the open oil inlet valve 132, 232, and/or 332 corresponding to the compressor 102, 202, and/or 302 having an oil level that is above the minimum predetermined threshold value to transition from the second, open position to the first, closed position to inhibit oil from flowing into the corresponding suction port 116, 216, and/or 316 (FIG. 2). Further, the algorithm 176 causes the processor 172 to instruct the corresponding oil outlet valve 128, 228, and/or 328 to transition from the second, open position to the first, closed position to inhibit oil 114, 214, and/or 314 from flowing into the oil manifold 160 (FIG. 2).

In some embodiments, more than one oil inlet valve 132, 232, and/or 332 and/or more than one oil outlet valve 128, 228, and/or 328 may be in the open position. In the example embodiment, the algorithm 176 may cause the processor 172 to instruct one or more oil inlet valves 132, 232, and/or 332 and one or more oil outlet valves 128, 228, and/or 328 to transition from the second, open position to the first, closed position corresponding to the point in time the controller determines that the oil level within the corresponding oil sump 112, 212, and/or 312 is above the minimum predetermined threshold value. The algorithm 176 may cause the processor 172 to instruct any number of oil outlet valves 128, 228, and 328 and any number of oil inlet valves 132, 232, and 332 to open or close without departing from the scope of the disclosure. Once all of the oil levels are determined to be above the minimum predetermined threshold value, the algorithm 176 causes the processor 172 to instruct open oil outlet valves 128, 228, and/or 328 to transition to the first, closed position.

In embodiments, the algorithm 176 ranks or otherwise identifies an order of compressors corresponding to the identified oil level within the oil sumps 112, 212, and 312 from a lowest oil level to a highest oil level. The algorithm 176 compares the identified oil levels to a maximum predetermined threshold value (e.g., a maximum oil level within the oil sump 112, 212, and 312). If one or more of the identified oil levels is above the maximum predetermined threshold value, the algorithm 176 causes the processor 172 to instruct the oil outlet valve 128, 228, and/or 328 corresponding to the compressor 102, 202 and/or 302 having and oil level that is above the maximum predetermined threshold value to transition from the first, closed position to the second, open position to permit oil 114, 214, and/or 314 within the corresponding oil sump 112, 212, and/or 312 to flow into the oil manifold 160. The algorithm 176 causes the processor 172 to instruct the oil inlet valve 132, 232, and/or 332 corresponding to the compressor 102, 202, or 302 having the lowest oil level to transition from the first, closed position to the second, open position to permit oil to flow into the corresponding suction port 116, 216, and/or 316 to transfer oil from the compressor 102, 202, and/or 302 having an oil level above the maximum predetermined threshold value to the compressor 102, 202, and/or 302 having the lowest oil level.

With reference to FIGS. 6A-6C, a method of operating a multiple compressor system is illustrated and generally identified by reference numeral 600. The controller receives 602 signals from each oil level sensor of the plurality of compressors of the rack of compressors. The controller identifies 604 a compressor of the plurality of compressors with the highest oil level based on the signals received from each oil level sensor. The identified oil levels are compared 606 to a minimum predetermined threshold value and it is determined 608 if an oil level of one or more compressors of the plurality of compressors is below the minimum predetermined threshold value. If it is determined that no compressors have an oil level that is below the minimum predetermined threshold value, the method returns to receiving 602 signals from each oil level sensor. If it is determined that one or more compressors have an oil level that is below the minimum predetermined threshold value, it is determined 610 if the one or more compressors having an oil level that is below the minimum predetermined threshold value are operating. If it is determined that one or more of the compressors having an oil level that is below the minimum predetermined threshold value is not operating, the controller inhibits 612 the oil inlet valve of the one or more compressors in a non-operating condition having an oil level that is below the minimum predetermined threshold value and inhibits the oil outlet valve of the compressor having the highest oil level from opening. If it is determined that one or more of the compressors having an oil level that is below the minimum predetermined threshold value is operating, the controller opens 614 the oil outlet valve of the compressor having the highest oil level and opens the oil inlet valve of each compressor having an oil level that is below the minimum predetermined threshold value and is in an operating condition to transfer 616 oil from the compressor having the highest oil level to each compressor having an oil level that is below the minimum predetermined threshold value and in an operating condition. The controller compares 618 the identified oil levels of compressors receiving oil to the minimum predetermined threshold value based on the signals received from the oil level sensors. The controller determines 620 if one or more compressors has an oil level that is above the minimum predetermined threshold value. If it is determined that no compressors having an oil level that is above the minimum predetermined threshold value, the transfer 616 of oil from the compressor having the highest oil level to each compressor having an oil level that is below the minimum predetermined threshold value continues. If it is determined that at least one compressor has an oil level that is above the minimum predetermined threshold value, it is then determined 622 if more than one compressor has an oil level that is below the minimum predetermined threshold value. If more than one compressor has an oil level that is below the minimum predetermined threshold value, the controller closes 624 the oil inlet valve for each compressor having an oil level that is above the minimum predetermined threshold value and returns to transferring 616 oil from the compressor having the highest oil level to the remaining compressors having an oil level that is below the minimum predetermined threshold value. If there is only one compressor that has an oil level that is below the minimum predetermined threshold value, the controller closes 626 the oil inlet valve for each compressor with an oil level above the minimum predetermined threshold value and closes 628 the oil outlet valve for the compressor having the highest oil level. In some embodiments, the controller may inhibit 630 opening of each oil inlet valve and each oil outlet valve of the plurality of compressors for a predetermined period of time to allow the working fluid to flow through the multiple compressor system and allow the oil level within each oil sump to stabilize. The controller determines 632 if the predetermined period of time has expired. If it is determined that the predetermined period of time has expired, the controller returns to receiving 602 signals from each oil level sensor. If it is determined that the predetermined period of time has not expired, the controller returns to inhibiting 630 each oil inlet valve and each oil outlet valve from opening.

In some embodiments, the controller may follow the same or similar method when it is determined that an oil level of one or more compressors is above a maximum predetermined threshold value. The above described method may be performed in any order and any number of times without departing from the scope of the disclosure.

It is envisioned that the working fluid may include at least one refrigerant that is suitable for use in refrigeration cycle. Non-limiting examples of suitable refrigerants include natural refrigerants (e.g., carbon dioxide, water, ammonia, hydrocarbons, etc.), fluorocarbon-based refrigerants, and refrigerants that have a low global warming potential, such as ASHRAE classified A1 and A2L refrigerants. Non-limiting examples of A1 refrigerants include carbon dioxide (R-744), chlorodifluoromethane (R-22), 1,1-difluoroethane (R152a), 1,1,1,2-tetrafluoroethane (R134A), and R410A (a near-azeotropic mixture of difluoromethane (R-32) and pentafluoroethane (R-125)), and trifluoro monochloropropenes (R-1233 including cis-and trans-1-chloro- 3,3,3-trifluoropropene (HFO-1233zd) isomers (HFO-1233zd(Z) and HFO-1233zd(E)), and hexafluorobutenes (HFO-1336, including HFO-1336mzz(Z), 1336mzz(E)). Non-limiting examples of A2L refrigerants include difluoromethane (R-32) and hydrofluorolefins (HFOs). Suitable HFO refrigerants are described, for example, in U.S. Pat. No. 4,788,352 to Smutny and U.S. Pat. No. 8,444,874 to Singh et al., the relevant portions of which are incorporated by reference. HFOs may include 2,3,3,3-tetrafluoroprop-1-ene (HFO-1234yf) and trans-1,3,3,3-tetrafluoroprop-1-ene (HFO-1234ze). Non-limiting suitable examples of specific HFO refrigerants include 3,3,3-trifluoropropene (HFO- 1234zf), HFO-1234 refrigerants like 2,3,3,3-tetrafluoropropene (HFO-1234yf), 1,2,3,3-tetrafluoropropene (HFO-1234ze), cis- and trans-1,3,3,3-tetrafluoropropene (HFO-1234ye), pentafluoropropenes (HFO-1225) such as 1,1,3,3,3,pentafluoropropene (HFO-1225zc), hexafluorobutenes (HFO-1336), such as cis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-Z) and trans-1,1,1,4,4,4-hexafluoro-2-butene (R1336mzz(E)), or those having a hydrogen on the terminal unsaturated carbon such as 1,2,3,3,3, pentafluoropropene (HFO-1225yez), fluorochloropropenes such as trifluoro, monochloropropenes (HFO-1233) like CF3CCl═CH2 (HFO-1233xf) and CF3CH═CHCl (HFO-1233zd) (including trans (E) and cis (Z) isomers (HFO-1233zd(E) and HFO-1233zd(Z)), (E)-1,2-difluoroethene (R-1132(E)), and any combinations thereof. In certain aspects, the HFO refrigerant may be selected from the group consisting of: R-1234yf, R-1234ze, R1233zd(E), R1233zd(Z), R1336mzz(Z), R1336mzz(E), R-1132(E), and combinations thereof. In some examples, these refrigerants are used in combination with other A1 or A2L refrigerants or yet other refrigerants, such or A3 or B1 or B2 refrigerants, including natural or flammable refrigerants (e.g., dimethyl ether (R-E170) or propane (C3H8 or R-290)).

The multiple compressor system 10 in some examples operates using a working fluid that includes a refrigerant blend of at least two refrigerants. Suitable refrigerant blends and suitable climate control systems for use with such refrigerant blends are described, for example, in U.S. patent application Ser. No. 17/507,403 by Welch, et al., filed on October 2021, and published as U.S. Patent Application Publication No. 2023/0130167 on Apr. 27, 2023, the entire disclosure of which is hereby incorporated by reference herein. It is envisioned that features of multiple compressor system 10 can be used in any combination with the systems described in U.S. Patent Application Publication No. 2023/0130167, previously incorporated by reference herein. In certain examples, the refrigerant blend includes an A1 refrigerant, such as carbon dioxide (R-744), mixed with at least one other refrigerant. As can be appreciated, the carbon dioxide refrigerant is suitable for use in a sub-critical system design. One example of a suitable, non-limiting refrigerant blend includes CO₂ (R-744) as the more volatile, high-pressure refrigerant mixed with an HFO refrigerant (e.g., R-1233zd(E)) as the less volatile, low-pressure fluid. The refrigerant blend may be a “high glide” refrigerant blend that has a first refrigerant (e.g., CO₂) with a relatively lower normal boiling point (at 1 atmosphere (atm) of pressure)) and a second refrigerant with a relatively higher normal boiling point. A difference between normal boiling points of the first and second refrigerants is greater than or equal to 25° C. As a non-limiting example, where the refrigerant blend includes CO₂ having a normal boiling point of approximately 78° C. at 1 atm and R-1233zd(e) having a normal boiling point of approximately 18° C. at 1 atm, a different in boiling points is about 96° C.

Suitable working fluid refrigerant blends include a refrigerant selected from the group consisting of: R-744, R-22, R134A, R410A, R-1234yf, R-1234ze, R1233zd(E), R1233zd(Z), R1336mzz(Z), R1336mzz(E), and combinations thereof. Alternatively, a first refrigerant and a second refrigerant included in the refrigerant blend are independently selected from the group consisting of: R-744, R-22, R152a, R134A, R410A, R-E170, R-32, HFOs, R-290, R-601 (pentane), hexane, and combinations thereof. In some examples, the first refrigerant is selected from the group consisting of: R-744, R-22, R134A, R410A, R-E170, R-32, HFOs, and combinations thereof, and the second refrigerant is selected from the group consisting of: 2,3,3,3-tetrafluoroprop-1-ene (R1234yf), 1,3,3,3-tetrafluoroprop-1-ene (R-1234ze), 1-chloro-3,3,3-trifluoropropene (HFO-1233zd(E)), 1-chrloro-3,3,3-trifluoropropene (HFO-1233zd(Z)), 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz), and combinations thereof.

The working fluid may include one or more refrigerants, such as those described hereinabove, in combination with a refrigeration lubricant oil. For example, the working fluid may include a synthetic oil. The lubricant oil may in some examples include a polyvinyl ether (PVE) oil, a polyalphaolefin (PAO), a polylkylene glycol (PAG), alkylbenzene, mineral oil, or an ester-based oil, such as polyol ester (POE) oil. POE oils may suitably be used where carbon dioxide (R-744) is present in the working fluid (e.g., in a refrigerant blend). Suitable POE oils may include a compound formed from a carboxylic acid and a polyol. Such POE compounds may be formed from a carboxylic acid selected from the group consisting of: n-pentanoic acid, 2-methylbutanoic acid, n-hexanoic acid, n-heptanoic acid, 3,3,5-trimethylhexanoic acid, 2-ethylhexanoic acid, n-octanoic acid, n-nonanoic acid, and isononanoic acid, and combinations thereof and a polyol selected from a group consisting of: pentaerythritol, dipentaerythritol, neopentyl glycol, trimethylpropanol, and combinations thereof.

Technical benefits of the methods and systems described herein include reducing the number of components operatively connected to the multiple compressor system by eliminating a central oil separator. The central oil separator is replaced by internal oil separators within each compressor of the multiple compressor system. Additionally, the methods and systems described herein control the oil level within each compressor using valves and sensors controllable by a controller of an oil distribution system, in addition to, or in lieu of systems and methods utilizing pressure to balance oil levels within each compressor. Further, the methods and systems described herein enable multiple compressor systems utilizing carbon dioxide as a working fluid to balance the relatively higher amount of oil needed as compared to multiple compressor systems utilizing other types of working fluids.

As used herein, the terms “about,” “substantially,” “essentially” and “approximately” when used in conjunction with ranges of dimensions, concentrations, temperatures or other physical or chemical properties or characteristics is meant to cover variations that may exist in the upper and/or lower limits of the ranges of the properties or characteristics, including, for example, variations resulting from rounding, measurement methodology or other statistical variation.

When introducing elements of the present disclosure or the embodiment(s) thereof, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” “containing,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. The use of terms indicating a particular orientation (e.g., “top,” “bottom,” “side,” etc.) is for convenience of description and does not require any particular orientation of the item described.

As various changes could be made in the above constructions and methods without departing from the scope of the disclosure, it is intended that all matter contained in the above description and shown in the accompanying drawing[s] shall be interpreted as illustrative and not in a limiting sense.

Claims

1. A compressor system comprising:

a suction manifold;

an oil manifold;

a first compressor fluidly connected to the suction manifold and selectively connectable to the oil manifold, the first compressor comprising a first oil separator receiving fluid from the suction manifold;

a second compressor fluidly connected to the suction manifold and selectively connectable to the oil manifold, the second compressor comprising a second oil separator receiving fluid from the suction manifold; and

a controller connected in communication with each of the first compressor and the second compressor, the controller including a processor and a memory, wherein the memory stores instructions that program the processor to: determine an oil level within each of the first compressor and the second compressor; determine that an oil level within one of the first compressor and the second compressor is below a predetermined threshold value; and transfer oil from the other of the first compressor and the second compressor having an oil level that is below the predetermined threshold value to the compressor of the first compressor or the second compressor having an oil level that is below the predetermined threshold value.

2. The compressor system according to claim 1, wherein the first compressor further comprises:

a first oil outlet valve operable to selectively connect the first compressor to the oil manifold; and

a first oil inlet valve operable to selectively connect the oil manifold to the first compressor.

3. The compressor system according to claim 2, wherein the memory stores further instructions that program the processor to:

determine that a compressor determined to have an oil level that is below the predetermined threshold value is operating; and

inhibit the oil inlet valve corresponding to the compressor that is not operating from opening.

4. The compressor system according to claim 3, wherein the second compressor further comprises:

a second oil outlet valve operable to selectively connect the second compressor to the oil manifold; and

a second oil inlet valve operable to selectively connect the oil manifold to the second compressor.

5. The compressor system according to claim 4, wherein the memory stores further instructions that program the processor to:

open one of the first oil inlet valve and the second oil inlet valve corresponding to the one of the first compressor and the second compressor determined to have an oil level below the predetermined threshold value; and

open one of the first oil outlet valve and the second oil outlet valve corresponding to the other of the first compressor and the second compressor to transfer oil from the first compressor or the second compressor associated with the opened oil outlet valve to the first compressor or the second compressor associated with the opened oil inlet valve.

6. The compressor system according to claim 1, further comprising:

a third compressor fluidly connected to the suction manifold and selectively connectable to the oil manifold, the third compressor comprising a third oil separator receiving fluid from the suction manifold, wherein the memory stores further instructions that program the processor to: identify a compressor of the first compressor, the second compressor, and the third compressor having a highest oil level; and transfer oil from the compressor identified as having the highest oil level to at least one of the first compressor, the second compressor, and the third compressor having an oil level that is below the predetermined threshold value.

7. The compressor system according to claim 1, wherein the oil manifold is fluidly connected to one or more oil outlet ports of the first compressor and the second compressor, wherein at least one of the first compressor and the second compressor is a high-side compressor having a motor disposed within a discharge pressure chamber of the compressor.

8. The compressor system according to claim 1, wherein the oil manifold is fluidly connected to one or more oil outlet ports of the first compressor and the second compressor, wherein at least one compressor of the first compressor and the second compressor is an intermediate pressure compressor.

9. The compressor system according to claim 1, wherein the oil manifold is fluidly connected to an internal oil sump of each of the first compressor and the second compressor.

10. The compressor system according to claim 1, wherein the oil transferred from the other of the first compressor and the second compressor having an oil level that is below the predetermined threshold to the compressor of the first compressor or the second compressor having an oil level that is below the predetermined threshold value is separated from carbon dioxide flowing through the first compressor and the second compressor.

11. An oil distribution system for use with a plurality of compressors, each compressor of the plurality of compressors comprising an oil separator, and oil sump, an oil level sensor operably connected to the oil sump, a suction port, and an oil outlet port fluidly connected to the oil sump, the oil distribution system comprising:

an oil manifold fluidly connected to each oil outlet port of the plurality of compressors;

a plurality of oil outlet valves, each oil outlet valve fluidly connecting a respective oil outlet port of the plurality of compressors to the oil manifold, each oil outlet valve of the plurality of oil outlet valves positionable between a closed position and an open position;

a plurality of oil inlet valves, each oil inlet valve fluidly connecting the oil manifold to a respective suction port of the plurality of compressors, each oil inlet valve positionable between a closed position and an open position; and

a controller connected in communication with each oil level sensor, each oil outlet valve, and each oil inlet valve, the controller including a processor and a memory, the memory storing instructions that program the processor to: determine that an oil level of a compressor of the plurality of compressors is below a predetermined threshold value based on signals received from each oil level sensor of the plurality of compressors; identify a compressor of the plurality of compressors with a highest oil level based on signals received from each oil level sensor of the plurality of compressors; open the oil inlet valve associated with the compressor having an oil level that is below the predetermined threshold value; and open the oil outlet valve associated with the compressor having the highest oil level to transfer oil from the compressor having the highest oil level to the compressor having an oil level that is below the predetermined threshold value.

12. The oil distribution system according to claim 11, wherein the memory stores further instructions that program the processor to determine that a compressor determined to have an oil level that is below the predetermined threshold value is operating.

13. The oil distribution system according to claim 12, wherein the memory stores further instructions that program the processor to inhibit the oil inlet valve associated with a compressor that is not operating from opening.

14. The oil distribution system according to claim 11, wherein the memory stores further instructions that program the processor to inhibit opening of the plurality of oil inlet valves and the plurality of oil outlet valves for a predetermined period of time subsequent to transferring oil from the compressor having the highest oil level to the compressor having an oil level that is below the predetermined threshold value.

15. The oil distribution system according to claim 11, wherein the memory stores further instructions that program the processor to:

determine that an oil level of two or more compressors of the plurality of compressors is below the predetermined threshold value based on the signals received from each oil level sensor of the plurality of compressors;

open each oil inlet valve associated with the two or more compressors having an oil level that is below the predetermined threshold value; and

open the oil outlet valve associated with the compressor having the highest oil level to transfer oil from the compressor having the highest oil level to each compressor having an oil level that is below the predetermined threshold value.

16. A method of distributing oil in a multiple compressor system, the multiple compressor system including a plurality of compressors, each compressor of the plurality of compressors comprising an oil separator separating oil from fluid flowing through the compressor, the method comprising:

determining that an oil level of a compressor of the plurality of compressors is below a predetermined threshold value based on signals received from an oil level sensor of each compressor of the plurality of compressors;

identifying a compressor of the plurality of compressors with a highest oil level based on signals received from each oil level sensor of the plurality of compressors;

open an oil inlet valve associated with the compressor having an oil level that is below the predetermined threshold value; and open an oil outlet valve associated with the compressor having the highest oil level to transfer oil from the compressor having the highest oil level to the compressor having an oil level that is below the predetermined threshold value.

17. The method according to claim 16, further comprising determining that a compressor determined to have an oil level that is below the predetermined threshold value is operating.

18. The method according to claim 17, further comprising inhibiting the oil inlet valve associated with a compressor that is not operating from opening.

19. The method according to claim 16, further comprising inhibiting opening of each inlet valve of the plurality of compressors and each outlet valve of the plurality of compressors for a predetermined period of time subsequent to transferring oil from the compressor having the highest oil level to the compressor having an oil level that is below the predetermined threshold value.

20. The method according to claim 16, further comprising:

determining that an oil level of two or more compressors of the plurality of compressors is below the predetermined threshold value based on the signals received from each oil level sensor of the plurality of compressors;

opening each oil inlet valve corresponding to the two or more compressors having an oil level that is below the predetermined threshold value; and

opening the oil outlet valve corresponding to the compressor identified as having the highest oil level to transfer oil from the compressor identified as having the highest oil level to at least one of the compressors having an oil level that is below the predetermined threshold value.