System and method for ocr control in parallel compressors

Abstract

A heating, ventilation, air conditioning, and refrigeration (HVACR) system includes fluidly connected first and second compressors, a condenser, an expansion device, and an evaporator, the first compressor having a first displacement, the second compressor having a second displacement, the first and second compressors arranged in parallel. The first compressor includes a first lubricant reservoir. The second compressor includes a second lubricant reservoir. The first lubricant reservoir is fluidly connected to the second lubricant reservoir by a lubricant transfer conduit. A flow restrictor is disposed in the lubricant transfer conduit. The flow restrictor is configured to reduce refrigerant flow between the first and second compressors.

Description

Technical Field

[0001] This disclosure relates to heating, ventilation, air conditioning, and refrigeration (HVACR) systems. More specifically, this disclosure relates to systems and methods for controlling the lubricant circulation ratio (oil discharge rate) in an HVACR system having compressors arranged in parallel. Background Technology

[0002] The heat transfer loop for an HVACR system typically includes a compressor, condenser, expander, and evaporator in fluid connection. The compressor typically includes a rotating component driven by an electric motor. The HVACR system may include a rooftop unit to supply conditioned air to an air distribution system that includes a duct system. The heat transfer loop may include multiple compressors. In one application, one or more of the multiple compressors may be turned on or off during operation. Summary of the Invention

[0003] This disclosure relates to HVACR systems. More specifically, this disclosure relates to systems and methods for controlling the lubricant circulation ratio (oil discharge rate) in an HVACR system having compressors arranged in parallel.

[0004] The embodiments disclosed in this application relate to lubricant (e.g., oil) circulation ratio control for multiple compressors connected in parallel. The multiple compressors include compressors having lubricant reservoirs (oil sumps). The compressors are driven by electric motors. The electric motor includes a stator and a rotor. In some embodiments, the compressor is a hermetic compressor having an electric motor and compression components disposed within a compressor housing. In some embodiments, the lubricant reservoir is disposed in the relatively vertical lower part of the compressor such that lubricant can be collected in the lubricant reservoir by gravity. In some embodiments, the lubricant is entrained in the heat transfer fluid of the heat transfer circuit of the HVACR system.

[0005] In some embodiments, the plurality of compressors may include a first compressor and a second compressor. In some embodiments, the first compressor may be a variable speed compressor, and the second compressor may be a fixed speed compressor. In some embodiments, both the first compressor and the second compressor may be a fixed speed compressor or a variable speed compressor. In some embodiments, the first compressor and / or the second compressor may be a scroll compressor.

[0006] In some embodiments, the plurality of compressors may include two or more compressors. In some embodiments, the plurality of compressors may include three compressors. In some embodiments, the plurality of compressors may include four compressors. In some embodiments, the plurality of compressors may include at least one variable speed compressor.

[0007] In some embodiments, a flow restrictor may be disposed in the lubricant delivery conduit between the lubricant reservoirs of the parallel compressors to reduce airflow (heat transfer fluid) through the lubricant delivery conduit. In one embodiment, the flow restrictor may be disposed at or near the midpoint of the length of the lubricant delivery conduit. It should be understood that the location of the flow restrictor can be anywhere in the lubricant delivery conduit, as long as the lubricant circulation ratio can be maintained within a desired range. In some embodiments, the desired range of the lubricant circulation ratio is a predetermined range. In some embodiments, a flow restrictor may be present in each / any one of the lubricant delivery conduits (connecting a pair of compressors).

[0008] In some embodiments, the suction duct design can be configured to allow lubricant to return more easily to the compressor with the lower capacity compared to the compressor with the higher capacity in a parallel compressor unit (e.g., to make it easier to obtain lubricant in the return / suction heat transfer fluid).

[0009] An HVACR system is disclosed. The system includes a first compressor having a first displacement, a second compressor having a second displacement, a condenser, an expander, and an evaporator, all fluidly connected. The first and second compressors are arranged in parallel. The first compressor includes a first lubricant reservoir. The second compressor includes a second lubricant reservoir. The first lubricant reservoir is fluidly connected to the second lubricant reservoir via a lubricant delivery conduit. A flow restrictor is configured in the lubricant delivery conduit to reduce refrigerant flow between the first and second compressors. Attached Figure Description

[0010] Reference is made to the accompanying drawings, which form part of this disclosure, illustrating embodiments in which the systems and methods described herein may be practiced.

[0011] Figure 1A This is a schematic diagram of a heat transfer circuit according to one embodiment.

[0012] Figure 1B This is a schematic diagram of a heat transfer circuit according to another embodiment.

[0013] Figure 2A This is a schematic diagram of two compressors arranged in parallel with a flow limiter according to one embodiment. Figure 2B It shows Figure 2A The current limiter.

[0014] Figure 3A-1 , 3A-2 And 3A-3 shows various embodiments of a current limiter according to some embodiments.

[0015] Figure 3BThis is a schematic diagram of a flow limiter installed at the lubricant balance pipe port of a compressor according to one embodiment.

[0016] Throughout the text, the same reference numerals are used to denote the same parts. Detailed Implementation

[0017] This disclosure relates to HVACR systems. More specifically, this disclosure relates to systems and methods for controlling the lubricant circulation ratio (oil discharge rate) in HVACR systems having compressors arranged in parallel.

[0018] In some embodiments, the heat transfer circuit may include multiple compressors. The multiple compressors may be connected in parallel in the heat transfer circuit. Suction conduits may be fluidly connected to the suction ports of the multiple compressors. A mixture of heat transfer fluid and lubricant may flow into the suction ports of the multiple compressors via one or more of the suction conduits. Each of the multiple compressors may include a lubricant reservoir. Each compressor may be driven by an electric motor, which is housed within the same enclosure / container as the compressor. In some embodiments, the lubricant reservoir may be located at the relatively vertical lower part of the compressor so that the lubricant can be collected in the lubricant reservoir by gravity. In some embodiments, the lubricant may be entrained in the heat transfer fluid of the heat transfer circuit of the HVACR system. It should be understood that the heat transfer fluid (e.g., refrigerant) may include a mixture of a portion of the heat transfer fluid (e.g., refrigerant) and a lubricant (e.g., oil).

[0019] The lubricant can be supplied to one or more compressors via one or more suction lines through corresponding suction ports, the suction lines supplying gaseous heat transfer fluid from the evaporator of the heat transfer circuit to the compressors. The lubricant can flow through gaps between the compressor housing and the stator of the motor and / or between the stator and the rotor of the motor to return to the compressor reservoir. These gaps allow lubricant to return from the compressor's suction chamber to the compressor reservoir. In some embodiments, when one (or more) compressors are off, the heat transfer circuit cannot reliably return lubricant to the reservoirs of the one or more open compressors. This is because the gaseous heat transfer fluid can flow through the one or more closed compressors and through lubricant delivery lines (e.g., lubricant balance lines / oil balance lines), and upwards through the gaps of the one or more open compressors. This causes the lubricant to remain in the compressor's suction chamber instead of being emptied through the gaps (downwards to the reservoir). Therefore, the lubricant content / oil level in the compressor reservoir may be low. In some embodiments, the gaps can be increased to allow lubricant to be discharged through the gaps (downwards to the reservoir). In some embodiments, increasing the size of the clearance may not be feasible due to the limitations of the compressor's internal geometry (e.g., finite dimensions).

[0020] The embodiments disclosed in this application can help retain as much lubricant as possible in the compressor(s) (lubricant reservoir) and can improve the reliability of the compressor(s). For example, a flow restrictor (described later) can help reduce the lubricant / oil circulation ratio (OCR, oil discharge rate) of a parallel compressor system, thereby improving the system's heat exchange efficiency, such as improving energy efficiency and saving energy under partial load conditions.

[0021] Figure 1A This is a schematic diagram of a heat transfer loop 10A according to one embodiment. The heat transfer loop 10A typically includes multiple compressors 12A, 12B, a condenser 14, an expansion device 16, and an evaporator 18. The expansion device 16 allows the working fluid to expand. This expansion results in a significant decrease in the temperature of the working fluid. The term "expansion device" as used herein may also be referred to as an expander. In one embodiment, the expander may be an expansion valve, expansion plate, expansion container, orifice, or other expansion mechanism of this type. It should be understood that the expander can be any suitable type of expander used in the field to expand the working fluid to generate gas pressure and cause a temperature reduction. The heat transfer loop 10A is exemplary and can be modified to include additional components. For example, in some embodiments, the heat transfer loop 10A may include other components, such as, but not limited to, an economizer heat exchanger, one or more flow restrictors, a receiver box, a dryer, a liquid wicking heat exchanger, etc.

[0022] The heat transfer loop 10A can typically be applied to various systems that control environmental conditions (e.g., temperature, humidity, air quality, etc.) in a space (often referred to as an air-conditioned space). Examples of such systems include, but are not limited to, HVACR systems and transport refrigeration systems.

[0023] The components of the heat transfer circuit 10A are fluidly connected. The heat transfer circuit 10A may be specifically configured as a cooling system (e.g., an air conditioning system) capable of operating in a cooling mode. Alternatively, the heat transfer circuit 10A may be specifically configured as a heat pump system capable of operating in both a cooling mode and a heating / defrosting mode.

[0024] The heat transfer circuit 10A can operate according to known principles. The heat transfer circuit 10A can be configured to heat or cool a heat transfer fluid or medium (e.g., a liquid such as, but not limited to, water), in which case the heat transfer circuit 10A can generally represent a liquid cooler system. Alternatively, the heat transfer circuit 10A can be configured to heat or cool a heat transfer fluid or medium (e.g., a gas such as, but not limited to, air), in which case the heat transfer circuit 10A can generally represent an air conditioner or a heat pump.

[0025] In operation, compressors 12A and 12B compress a heat transfer fluid (e.g., refrigerant, etc.) from a lower-pressure gas to a higher-pressure gas. The relatively higher-pressure and higher-temperature gas exits from compressors 12A and 12B and flows through condenser 14. According to generally known principles, the heat transfer fluid flows through condenser 14 and dissipates heat to the heat transfer fluid or medium (e.g., water, air, etc.), thereby cooling the heat transfer fluid. The cooled heat transfer fluid is now in a liquid state and flows to expansion device 16. The expansion device 16 reduces the pressure of the heat transfer fluid. Therefore, a portion of the heat transfer fluid is converted into a gaseous state. The heat transfer fluid now flows to evaporator 18 in a mixture of liquid and gaseous forms. The heat transfer fluid flows through evaporator 18 and absorbs heat from a heat transfer fluid or medium (e.g., water, air, etc.), heating the heat transfer fluid and converting it into a gaseous state. The gaseous heat transfer fluid then returns to compressors 12A and 12B. For example, when the heat transfer circuit 10A is operating in cooling mode, the above process continues (e.g., when compressors 12A and 12B are started).

[0026] Compressors 12A and 12B may be, for example, scroll compressors, but are not limited to scroll compressors. In some embodiments, compressors 12A and 12B may be other types of compressors. Examples of other types of compressors include, but are not limited to, reciprocating compressors, positive displacement (positive displacement) compressors, or other types of compressors suitable for heat transfer circuit 10A and having a lubricant reservoir. Compressor 12A may typically be a variable speed compressor, and compressor 12B may typically be a fixed speed compressor. In some embodiments, both compressors 12A and 12B may be fixed speed compressors or variable speed compressors. In some embodiments, compressors 12A and 12B may alternatively be step-controlled compressors (e.g., having two or more stages / phases within a single compressor). In some embodiments, compressors 12A and 12B may be compressors with different displacements. For example, according to some embodiments, compressor 12A may have a larger displacement than compressor 12B. It should be understood that compressor 12B may alternatively have a relatively larger displacement than compressor 12A. In some embodiments, the displacement of compressors 12A and / or compressor 12B may range from approximately 10 tons to approximately 25 tons.

[0027] Compressors 12A and 12B are connected in parallel in heat transfer circuit 10A. In this parallel compressor system configuration, the suction lines (e.g., lines, pipes) of multiple compressors are connected to each other, and these suction lines are connected to a common suction line (main suction line). The common suction line is connected to an evaporator to receive gaseous heat transfer fluid from the evaporator. The discharge lines of multiple compressors are connected to each other, and these discharge lines are connected to a common discharge line (main discharge line). The common discharge line is connected to a condenser so that higher pressure and higher temperature gases can flow through the condenser and be discharged from the compressors. The lubricant tanks of the compressors are fluidly connected to each other via lubricant delivery lines. The lubricant delivery lines may be referred to as oil balance lines. In this configuration, multiple compressors are connected in parallel. One advantage of this configuration is that each of the multiple compressors can be turned on or off according to the load demand / changes of the heat transfer circuit (thus changing the total displacement of the compressors), and the compressor displacement (or the overall cooling and / or heating of the heat transfer circuit) can be adjusted to suit load changes. In some embodiments, the parallel compressor system may be referred to as a manifold.

[0028] Therefore, the gaseous heat transfer fluid exiting the evaporator 18 is supplied to each compressor 12A, 12B via a main suction line 22 (e.g., a suction line / pipe) and a branch suction line 25. In one embodiment, the main suction line 22 is directly connected to one of the compressors 12A, 12B, while the branch suction line is directly connected to the other of the compressors 12A, 12B. The branch suction line 25 branches off from the main suction line 22. A connector (e.g., a T-connector) can connect the branch suction line 25 to the main suction line 22. Figure 1A In the illustrated embodiment, the main suction pipe 22 is fluidly connected to the suction port 27A of the compressor 12A, while the branch suction pipe 25 is fluidly connected to the suction port 27B of the compressor 12B. The main suction pipe 22 and the branch suction pipe 25 share a common pipe that extends from the outlet of the evaporator 18 to the connector. The main suction pipe 22 (including the common pipe portion) further extends from the connector to the suction port 27A. The branch suction pipe 25 (including the common pipe portion) branches off from the main suction pipe 22 at the connector and is fluidly connected to the suction port 27B. In this embodiment, the pressure drop in the branch suction pipe 25 is greater than the pressure drop in the main suction pipe 22.

[0029] After compression, the gas with relatively high pressure and higher temperature is discharged from compressor 12A via exhaust pipe 32A and from compressor 12B via exhaust pipe 32B. In some embodiments, the exhaust pipes 32A and 32B of compressors 12A and 12B are connected to each other at exhaust pipe 34 to provide the condenser 14 with the combined gas with relatively high pressure and higher temperature.

[0030] The heat transfer fluid in heat transfer circuit 10A typically includes a heat transfer fluid carrying lubricant. This lubricant is supplied to compressors 12A and 12B, for example, to lubricate the bearings and seals of compressors 12A and 12B to prevent leaks. When the relatively high-pressure and high-temperature heat transfer fluid is discharged from compressors 12A and 12B, the heat transfer fluid typically carries a portion of the lubricant, a portion of which is initially delivered to compressors 12A and 12B via the main suction pipe 22. A portion of the lubricant is retained in the lubricant reservoirs 13A and 13B of compressors 12A and 12B.

[0031] The lubricant reservoirs 13A and 13B of compressors 12A and 12B are fluidly connected via a lubricant delivery pipe 36. The lubricant delivery pipe 36 is positioned at the lubricant level of the lubricant reservoirs 13A and 13B, allowing lubricant to flow between compressors 12A and 12B. The fluid flow of lubricant is controlled by the pressure difference between the lubricant reservoir 13A of compressor 12A and the lubricant reservoir 13B of compressor 12B.

[0032] In some embodiments, the lubricant delivery conduit 36 ​​may be a lubricant balancing line configured to equalize the pressure in lubricant reservoir 13A and lubricant reservoir 13B. The lubricant delivery conduit 36 ​​is fluidly connected to lubricant reservoir 13A via reservoir inlet 29A of compressor 12A, and is fluidly connected to lubricant reservoir 13B via reservoir inlet 29B of compressor 12B. It should be understood that in some embodiments, 29A and / or 29B may be inlets for receiving lubricant from a compressor having a higher pressure in the compressor reservoir, and may also be outlets for delivering lubricant to a compressor having a lower pressure in the lubricant reservoir.

[0033] Figure 1B This is a schematic diagram of a heat transfer circuit 10B according to another embodiment. The heat transfer circuit 10B is similar to... Figure 1A The heat transfer circuit 10A is shown below. The differences between heat transfer circuit 10B and heat transfer circuit 10A are explained below.

[0034] The heat transfer circuit 10B includes a third compressor 12C. Compressors 12A, 12B, and 12C are connected in parallel in the heat transfer circuit 10B. Therefore, the gaseous heat transfer fluid leaving the evaporator 18 is supplied to compressor 12A via the main suction pipe 22, to compressor 12B via the main suction pipe 22 and branch suction pipe 25, and to compressor 12C via the main suction pipe 22 and another branch suction pipe 26.

[0035] After compression, the relatively high-pressure and high-temperature gas is discharged from compressor 12A via exhaust pipe 32A, from compressor 12B via exhaust pipe 32B, and from compressor 12C via exhaust pipe 32C. In some embodiments, the respective exhaust pipes 32A, 32B, and 32C of compressors 12A, 12B, and 12C are connected to each other at exhaust pipe 34 to supply the combined relatively high-pressure and high-temperature gas to condenser 14. For example, exhaust pipes 32A and 32B can be joined together (e.g., using a T-connector), and then the joined exhaust pipes (of 32A and 32B) can be joined to exhaust pipe 32C (e.g., using a T-connector). In another embodiment, exhaust pipes 32A and 32C can be joined, and then the joined pipe can be joined to 32B. In yet another embodiment, exhaust pipes 32C and 32B can be joined, and then the joined pipe can be joined to 32A.

[0036] The branch intake pipe 25 is fluidly connected to the main intake pipe 22. A connector (e.g., a T-connector) can connect the branch intake pipe 25 to the main intake pipe 22. The branch intake pipe 26 is fluidly connected to the main intake pipe 22. A connector (e.g., a T-connector) can connect the branch intake pipe 26 to the main intake pipe 22. The main intake pipe 22, branch intake pipe 25, and branch intake pipe 26 are fluidly connected to the intake port 27A of compressor 12A, the intake port 27B of compressor 12B, and the intake port 27C of compressor 12C, respectively.

[0037] The lubricant reservoirs 13A and 13B of compressors 12A and 12B are fluidly connected to each other via a lubricant delivery pipe 36A. The lubricant reservoirs 13A and 13C of compressors 12A and 12C are fluidly connected to each other via a lubricant delivery pipe 36B. The lubricant delivery pipe 36A is positioned at the lubricant level of the lubricant reservoirs 13A and 13B, allowing lubricant to flow between compressors 12A and 12B. The lubricant delivery pipe 36B is positioned at the lubricant height / level of the lubricant reservoirs 13A and 13C, allowing lubricant to flow between compressors 12A and 12C.

[0038] The lubricant delivery conduit 36A is fluidly connected to the lubricant reservoir inlet 29A of compressor 12A and the lubricant reservoir inlet 29B of compressor 12B. The lubricant delivery conduit 36B is fluidly connected to the lubricant reservoir inlet 29C of compressor 12A and the lubricant reservoir inlet 29D of compressor 12C. In some embodiments, reservoir inlets 29A and 29C may be the same inlet / outlet. It should be understood that in some embodiments, 29A and / or 29B and / or 29C and / or 29D may be inlets for receiving lubricant (e.g., receiving lubricant from a compressor with higher pressure in the lubricant reservoir). In some embodiments, 29A and / or 29B and / or 29C and / or 29D may be outlets for delivering lubricant (to a compressor with lower pressure in the lubricant reservoir).

[0039] It should be understood that as long as each lubricant delivery line (e.g., 36A, 36B, etc.) connects only two compressors, repeating this process can add additional compressors (a fourth compressor, a fifth compressor, etc. connected in parallel in the heat transfer circuit). In some embodiments, the lubricant delivery lines (36A, 36B) can be lubricant balancing lines configured to equalize the pressure in lubricant reservoir 13A with the pressure in lubricant reservoir 13B (and / or the pressure in lubricant reservoir 13A with the pressure in lubricant reservoir 13C).

[0040] Figure 2A A schematic diagram 200 shows two compressors 210, 220 arranged in parallel with a flow limiter 260 according to one embodiment. Figure 2B It shows Figure 2A The current limiter 260. It should be understood that each compressor 210, 220 can be as follows: Figure 1A and Figure 1B Any one of the compressors 12A, 12B, or 12C shown. It should also be understood that compressors 210 and 220 have similar structures; therefore, unless otherwise stated, components of one compressor described in this application can be applied to another compressor. In one embodiment, compressors 210 and 220 can be scroll compressors. A scroll compressor can be a compressor having two scrolls (e.g., staggered scrolls) to pump, compress, or pressurize fluids such as liquids and gases. Typically, one scroll of a scroll compressor is stationary while the other scroll operates eccentrically and does not rotate, thereby trapping and pumping or compressing the fluid chamber between the scrolls.

[0041] The compressor 210 includes an intake port 212, an outlet port 211, a compression component 213, a shaft 214, an electric motor having a stator 215 and a rotor 216, a lubricant reservoir 217, and a lubricant port 218. The compressor 220 includes an intake port 222, an outlet port 221, a compression component 223, a shaft 224, an electric motor having a stator 225 and a rotor 226, a lubricant reservoir 227, and a lubricant port 228. In one embodiment, the compressor 210 and / or the compressor 220 may be a hermetic compressor.

[0042] The compressor 210 may be a scroll compressor. The compression component 223 may include a non-moving scroll member (or a stationary scroll member, or a fixed scroll member) and a moving scroll member that meshes with the non-moving scroll member (e.g., via an Oldham coupling) to form a compression chamber within the housing of the compressor 210.

[0043] In the compressor 210, the intake port 212 is located between the compression component 213 and the electric motor (215, 216). The discharge port 211 is located at the top of the compressor 210 above the compression component 213. The electric motor (215, 216) is configured to drive the compression component 213 via the shaft 214 to compress a heat transfer fluid (e.g., refrigerant) from a lower-pressure gas to a higher-pressure gas. The relatively higher-pressure gas can be discharged from the compressor 210 through the discharge port 211. A lubricant reservoir 217 is located at the bottom of the compressor 210.

[0044] It should be understood that in some embodiments, a predetermined amount (level, height, etc.) of lubricant (e.g., oil) is required in the lubricant reservoir 217 so that an oil pump (not shown, typically located at the bottom of shaft 214) can pump the lubricant upward to lubricate moving parts that require lubrication, such as bearings, compression components, etc.

[0045] The lubricant is entrained in a heat transfer fluid (e.g., refrigerant). During operation of compressor 210, the lubricant can return to lubricant reservoir 217 via two paths, allowing the lubricant level in reservoir 217 to be at a predetermined desired level (flow rate, height, etc.). One path involves the lubricant (entrained in a gaseous heat transfer fluid) returning from outside compressor 210 (e.g., from the evaporator) to lubricant reservoir 217 via suction line 230. Another path involves lubricant pumped from reservoir 217 to lubrication surfaces of moving parts of compressor 210 (such as bearings, compression components, etc.) by a lubricant pump returning to reservoir 217. After lubrication, the lubricant flows downwards to reservoir 217.

[0046] In both paths, the lubricant passes through the (vertical) gaps in the middle of the compressor. These gaps include the gap between the compressor housing 210 and the stator 215, and / or the gap between the stator 215 and the rotor 216. It should be understood that the size of one or more gaps is relatively small (limited by, for example, the size and / or design constraints of the compressor), and airflow from the bottom of the compressor 210 prevents lubricant backflow into the lubricant reservoir 217. In some embodiments, one or more gaps may be widened to allow lubricant to drain downwards into the lubricant reservoir 217.

[0047] When compressors 210 and 220 are arranged in parallel in the heat transfer circuit, lubricant loss (e.g., oil loss / oil runoff) may occur. A typical lubricant loss phenomenon occurs when the two compressors 210 and 220 are unbalanced (e.g., one compressor is on while the other is off, or one compressor has a larger displacement than the other). An airflow (e.g., a gaseous heat transfer fluid flowing from one compressor's lubricant reservoir to the other's lubricant reservoir) may flow into the lubricant delivery line (e.g., an oil balance line) 250 between the two compressors 210 and 220. This airflow can flow into the compressor with the larger displacement (and / or the one that is on), then upward through a gap (between the housing and stator and / or between the stator and rotor of one compressor), then into the compressor's suction chamber, and then out of the compressor through its outlet. When this upward airflow is large / strong enough, it can affect the lubricant circulation inside the compressor and prevent lubricant from flowing back into the lubricant reservoir. Therefore, a high lubricant circulation ratio (oil circulation ratio / oil discharge rate, "OCR") may occur. A relatively high OCR may lead to lubricant loss in the compressor, thus affecting the compressor's lubrication function. For example, when sampling the heat transfer fluid in the compressor's suction chamber, the percentage / quantity of lubricant in the heat transfer fluid will be relatively high (due to the greater upward airflow, it will be more concentrated), and therefore, the OCR may be high.

[0048] like Figure 2AAs shown, when compressor 210 is turned on and compressor 220 is turned off (or when the displacement of compressor 210 is greater than that of compressor 220), the airflow entering the compressor (indicated by the arrow) includes airflow from suction duct 230 and airflow from compressor 220 via lubricant delivery duct 250 (referred to as "upflow"). When the upflow is large / strong enough, it can prevent lubricant from flowing back into lubricant reservoir 217. The upflow and the airflow from suction duct 230 can enter the suction chamber and then be discharged to the outside of compressor 210 through its outlet 211. Therefore, a high OCR may occur, resulting in a lower lubricant level (lower than desired) in lubricant reservoir 217 of compressor 210 and affecting the reliability of compressor 210.

[0049] Inhalation duct design can help reduce OCR. For example... Figure 2A As shown, suction pipe 230 is the main suction pipe (which is directly connected to the evaporator, see [reference]). Figure 1A and 1B The intake pipe 240 is a branch intake pipe that branches off from the main intake pipe 230. Typically, the pressure drop (of the gaseous heat transfer fluid) in the branch intake pipe can be higher than that in the main intake pipe. The pressure drop difference can be determined by, for example, the gravity of the lubricant and / or the shape and / or radius of (one or more) intake pipes and / or the presence or absence of branches.

[0050] It should be understood that by connecting compressor 220 (which has a lower displacement than compressor 210, or is shut off when compressor 210 is turned on) to a branch intake pipe and compressor 210 to a main intake pipe, the pressure drop in compressor 220 is higher than that in compressor 210. Therefore, the airflow from compressor 220 to compressor 210 via lubricant delivery pipe 250 can be reduced / lowered, resulting in a reduction / lower flow of upward gas in compressor 210, and consequently, a reduction / lower OCR (higher reliability / increased reliability).

[0051] It should be understood that differences in intake duct design (e.g., the compressor is connected to the main intake duct, and there are different resistances of the heat transfer fluid in different intake ducts), differences in compressor displacement, and / or differences in the size / shape of clearances in the compressor (between the housing and the stator and / or between the stator and the rotor) can alter the upward airflow (flow rate, velocity, etc.), which in turn can alter lubricant loss and / or OCR.

[0052] For example, such as Figure 2AThe suction duct design shown (i.e., compressor 210 is connected to the main suction duct 230, while compressor 220 is connected to the branch suction duct 240) will cause a greater pressure drop in compressor 220 (for the heat transfer fluid) than the pressure drop in compressor 210. Thus, the airflow (flow rate, velocity, etc.) through lubricant delivery duct 250 (when compressor 210 is on and compressor 220 is off) is greater than the airflow (flow rate, velocity, etc.) through lubricant delivery duct 250 (when compressor 210 is on and compressor 220 is off). That is to say, as... Figure 2A The intake duct design shown can reduce / decrease / lower the OCR when compressor 210 is on and compressor 220 is off, but may have adverse effects when compressor 220 is on and compressor 210 is off.

[0053] It should also be understood that when the displacements of parallel compressors 210 and 220 are uneven / unbalanced / different and compressors 210 and 220 operate simultaneously (i.e., both are on), the pressure at the bottom of the compressor with the larger displacement will be lower (compared to the compressor with the smaller displacement). Therefore, one or more suction lines need to be designed to allow lubricant to enter the compressor with a smaller displacement more easily than it would enter the compressor with a larger displacement. For example, as... Figure 2A As shown, because the main suction pipe is connected to compressor 210, compressor 210 has a greater chance of receiving lubricant back into the heat transfer fluid than compressor 220. Simultaneously, the pressure drop in the suction pipe 240 connected to compressor 220 is also greater. If the displacement of compressor 210 is less than or equal to the displacement of compressor 220, the lubricant can flow from compressor 210 to compressor 220 via lubricant delivery pipe 250 because the pressure at the bottom of compressor 220 (which has a larger displacement) is lower than the pressure in compressor 210. This suction pipe design is likely more ideal for maintaining and balancing the lubricant in compressors 210 and 220 compared to a configuration where compressor 210 has a larger displacement than compressor 220 (in which case the suction pipe design needs to be changed to allow easier lubricant return to compressor 220). It should be understood that even when the displacements of compressors 210 and 220 are the same, this intake pipe design is preferred, so that lubricant flow can be generated between compressors 210 and 220 due to the pressure difference (the pressure of one compressor that can easily obtain return lubricant is higher than the pressure of the other compressor that cannot easily obtain return oil), and the lubricant can flow from one compressor to the other due to the pressure difference, so as to ensure that there is no shortage of lubricant in the reservoir(s) of both compressors.

[0054] It should be understood that controlling the application of OCR through different inhalation tube designs may be limited. Figure 2AIn embodiments, this configuration can be used when compressor 220 is turned on and compressor 210 is turned off, and in such a configuration, as Figure 2A The illustrated intake duct design may not achieve the desired OCR. This is because the limited pressure drop caused by the intake duct design also limits the degree of OCR adjustment.

[0055] Under conditions where different compressors (210, 220) have different / uneven displacements (or are on / off), airflow between the compressors (210, 220) (through lubricant delivery conduit 250) can disrupt the lubricant circulation path within the compressors (210, 220) and result in a higher OCR. A flow restrictor 260 can be disposed in the lubricant delivery conduit 250. The flow restrictor 260 is configured to reduce the airflow through the lubricant delivery conduit 250 and thus reduce the OCR, while maintaining the lubricant equalization capability of the lubricant delivery conduit 250. The flow restrictor 260 can be configured to maintain a constant OCR for the parallel compressors (e.g., when one compressor is on and the other is off, or when the displacement of one compressor is greater than that of another, etc., keeping the OCR at a stand-alone level) and retaining most of the lubricant within the parallel compressor unit to ensure compressor reliability.

[0056] The flow restrictor 260 can be configured to increase the gas flow resistance in the lubricant delivery conduit 250 to reduce the airflow rate and / or velocity, while ensuring that the lubricant delivery conduit 250 can still provide lubricant equalization. This allows the upward airflow rate and / or upward airflow velocity (through the gap between the housing and the stator 215, and / or the gap between the stator 215 and the rotor 216) to be reduced, which can easily allow more lubricant to return to the lubricant reservoir 217 through the gap. This can reduce the flow rate and / or percentage of lubricant discharged from the compressor, keep more lubricant in the lubricant reservoir 217, reduce the OCR of the parallel compressor unit, and improve the reliability of the parallel compressor unit.

[0057] In some embodiments, the flow restrictor 260 may be a perforated baffle, a mesh plate, or the like. In some embodiments, the flow restrictor 260 is disposed at or near the middle of the length of the lubricant delivery conduit 250. It should be understood that at or near the middle of the lubricant delivery conduit 250, the airflow state may be stable, and the effect of reducing airflow (flow rate, velocity, etc.) may be directly determined by the characteristics of the flow restrictor 260 (e.g., porosity, resistance, blockage area, etc.).

[0058] In some embodiments, the flow restrictor 260 may have different porosities. The porosity of the flow restrictor can be defined as a fraction between 0 and 1, or a percentage between 0% and 100%, of the ratio of the airflow area (the open area allowing airflow) of the flow restrictor (e.g., in cross-section) to the total area (including the open area and the obstruction area). It should be understood that the lubricant delivery conduit 250 (lubricant balance conduit) can also be configured to balance the airflow flowing through the lubricant delivery conduit 250 (to reduce the pressure difference between compressors 210 and 220). When the porosity of the flow restrictor 260 decreases, the airflow through the lubricant delivery conduit 250 may decrease, but the pressure difference between compressors 210 and 220 may increase. A smaller porosity of the flow restrictor 260 may adversely affect the lubricant balance between compressors 210 and 220. Thus, the porosity of the flow restrictor 260 is selected within a predetermined range such that when the parallel compressors reach a predetermined OCR range, the porosity of the flow restrictor 260 no longer decreases.

[0059] It should be understood that, assuming the airflow through the cross-section of flow restrictor 260 is uniform, the ability of flow restrictor 260 to impede airflow can be directly determined by the porosity of flow restrictor 260. The porosity of flow restrictor 260 is configured to reduce the airflow (flowing through flow restrictor 260) to a predetermined level flow rate. The porosity of flow restrictor 260 is configured such that the OCR is less than 2.5% or equal to or approximately 2.5% over the entire displacement / operating range of the parallel compressor (e.g., an air conditioning cooling setpoint of approximately 65°F). The porosity of flow restrictor 260 is also configured such that the OCR is less than 1% or equal to or approximately 1% over the rated displacement / operating range of the parallel compressor. It should be understood that the oil discharge rate OCR generally refers to the lubricant mass ratio (mass / weight percentage of lubricant in the refrigerant) in the refrigerant circuit of an HVACR system, which is generally equal to or close to the lubricant mass ratio in the discharge of (one or more) compressors. OCR is typically measured by obtaining the amount of liquid refrigerant at the liquid line and measuring the weight of the lubricant to calculate the lubricant ratio / weight percentage in the refrigerant. In one embodiment, the OCR of the compressor or manifold may be referred to as the lubricant mass ratio in the exhaust gas.

[0060] It should also be understood that a lower OCR can improve system performance because more lubricant in the system affects / enhances the heat exchanger's heat exchange capacity. In one embodiment, a flow limiter may be useful in cases of high OCR (e.g., exceeding 2.5%). OCR can be determined directly by the compressor's displacement variation or can be influenced by the compressor's internal structure (e.g., clearances), flow paths, or lubricant charge.

[0061] It should be understood that the flow limiter 260 can also be used in parallel compressor systems with three or more compressors. In such an embodiment, the flow limiter is disposed in the lubricant delivery line connecting each pair of compressors.

[0062] Figure 2B It shows Figure 2A A flow restrictor 260 is provided. The flow restrictor 260 includes a top having at least one opening 261, a middle portion 262, and a bottom having at least one opening 263. The flow restrictor 260 includes openings 261 near the top / top and / or 263 near the bottom / bottom of the flow restrictor 260 to allow unobstructed flow of gas through the lubricant delivery conduit 250. The opening 263 near the bottom / bottom is configured to ensure timely flow of lubricant from one compressor to another when the lubricant reaches a predetermined height / level in the reservoirs (217, 218). The opening 261 near the top / top is configured to maintain unobstructed airflow in the lubricant delivery conduit 250 when the lubricant in the lubricant reservoirs (217, 218) is at a level above the desired level. It should be understood that the current limiter 260 may include one or more openings (e.g., 264) of various sizes / shapes in other portions (e.g., 262) of the current limiter 260. It should also be understood that the current limiter 260 and / or its openings may have various sizes / shapes.

[0063] Figure 3A-1 , 3A-2Figure 3A-3 illustrates various embodiments 300, 310, and 320 of flow restrictors according to some embodiments. Flow restrictor 300 includes a top having at least one opening 301, a middle portion 302, and a bottom having at least one opening 303. Flow restrictor 310 includes a top having at least one opening 311, a middle portion 312, and a bottom having at least one opening 313. Flow restrictor 320 includes a top having at least one opening 321, a middle portion 322, and a bottom having at least one opening 323. The flow restrictors (300, 310, 320) include one or more openings (301, 311, 321) near the top / top of the flow restrictor and / or one or more openings (303, 313, 323) near the bottom / bottom of the flow restrictor (300, 310, 320) to allow unobstructed flow of gas through the flow restrictor (300, 310, 320) in the lubricant delivery conduit. The openings (303, 313, 323) near the bottom are configured to ensure that lubricant can flow promptly from one compressor to another when the lubricant in the lubricant reservoir reaches a predetermined height. The openings (301, 311, 321) near the top are configured to maintain unobstructed airflow in the lubricant delivery line when the lubricant in the lubricant reservoir is at a level higher than the desired level. It should be understood that the flow restrictor (300, 310, 320) may include openings (e.g., 304, 314, 324) of various sizes / shapes in other portions (e.g., 302, 312, 322) of the flow restrictor (300, 310, 320). It should also be understood that the flow restrictor (300, 310, 320) and / or its openings may have various sizes / shapes.

[0064] It should be understood that the flow restrictor is configured to generate sufficient resistance to control / reduce airflow in the lubricant delivery conduit under conditions of extreme imbalance (e.g., high suction pressure and / or high load operation, with one compressor on and one compressor off), such that the resulting upward airflow does not obstruct the flow of lubricant (from the top of the motor / compressor through the gap between the housing and the stator and / or the stator and rotor) to the lubricant reservoir as the upward airflow passes through the gap of the on-off compressor. It should also be understood that this control can be determined by the porosity of the flow restrictor (the ratio of the area through which air can flow to the total area including the openings and the obstruction areas).

[0065] It should be understood that although the shape / size of the flow restrictor may vary, it can achieve the same or similar effect in controlling / reducing airflow as long as the following conditions are met: the flow restrictor has the same / similar porosity / resistance and / or the flow restrictor includes one or more openings at the top / near the top and / or at the bottom / near the bottom. Openings at the bottom / near the bottom ensure that the compressors begin sharing lubricant when the lubricant level in the lubricant reservoir is above a predetermined level. Openings at the top / near the top ensure that airflow balance between compressors is maintained when there is more lubricant than desired.

[0066] Figure 3B This is a schematic diagram of a flow restrictor 330 disposed at a lubricant balance pipe port 340 of a compressor 350 according to one embodiment. The lubricant balance pipe port 340 of the compressor 350 is disposed on the compressor 350 and connected to a lubricant delivery conduit (not shown). The flow restrictor 330 includes a top having at least one opening 331, a middle portion 332, and a bottom having at least one opening 333. The flow restrictor 330 includes one or more openings 331 near the top / top of the flow restrictor 330 and / or one or more openings 333 near the bottom / bottom of the flow restrictor 330 to allow unobstructed gas flow through the flow restrictor 330 in the lubricant delivery conduit. The one or more openings 333 near the bottom / bottom are configured to ensure that lubricant can flow from one compressor to another in a timely manner when the lubricant reaches a predetermined height in the lubricant reservoir. The openings 331 near the top / top are configured to maintain unobstructed airflow in the lubricant delivery conduit when the lubricant in the lubricant reservoir is at a level higher than a desired level. It should be understood that the current limiter 330 may include one or more openings (e.g., 334) of various sizes / shapes in other portions (e.g., 332) of the current limiter 330. It should also be understood that the current limiter 330 and / or its openings may have various sizes / shapes.

[0067] This application discloses a heating, ventilation, air conditioning and refrigeration (HVACR) system, which includes:

[0068] A first compressor, a second compressor, a condenser, an expander, and an evaporator are fluidly connected, wherein the first compressor has a first displacement and the second compressor has a second displacement;

[0069] The first compressor and the second compressor are arranged in parallel.

[0070] The first compressor includes a first lubricant reservoir;

[0071] The second compressor includes a second lubricant reservoir;

[0072] The first lubricant storage tank is fluidly connected to the second lubricant storage tank via a lubricant delivery pipeline, and a flow limiter is installed in the lubricant delivery pipeline;

[0073] The flow restrictor is configured to reduce refrigerant flow between the first compressor and the second compressor.

[0074] In a preferred embodiment, according to the system of aspect 1, the current limiter includes a top having a first opening, a middle portion, and a bottom having a second opening.

[0075] In a preferred embodiment, according to the system of aspect 1 or aspect 2, the flow restrictor is configured to have a predetermined porosity to reduce the refrigerant flow rate between the first compressor and the second compressor to a predetermined level.

[0076] In a preferred embodiment, the system according to any one of aspects 1-3, wherein the current limiter is a porous baffle.

[0077] In a preferred embodiment, in the system according to any one of aspects 1-4, the flow restrictor is disposed in the middle of the lubricant delivery conduit.

[0078] In a preferred embodiment, the system according to any one of aspects 1-5, wherein the current limiter is configured to maintain the system's oil discharge rate at a level equal to or less than 2.5%.

[0079] In a preferred embodiment, the system according to any one of aspects 1-5, wherein the current limiter is configured to maintain the oil discharge rate of the system at a level equal to or less than 1%.

[0080] In a preferred embodiment, in the system according to any one of aspects 1-7, the first compressor includes a first suction port; the second compressor includes a second suction port; the first suction port is fluidly connected to a first suction conduit; and the second suction port is fluidly connected to the second suction conduit.

[0081] When the first displacement is less than the second displacement, the first intake pipe is configured to connect to the main pipe of the evaporator; the second intake pipe is configured to branch from the main pipe.

[0082] In a preferred embodiment, the system according to any one of aspects 1 to 8 further includes a third compressor having a third lubricant reservoir;

[0083] The first compressor, the second compressor, and the third compressor are arranged in parallel.

[0084] The second lubricant reservoir is fluidly connected to the third lubricant reservoir via a second lubricant delivery pipe; and

[0085] The second flow limiter is installed in the second lubricant delivery pipeline.

[0086] In a preferred embodiment, in the system according to any one of aspects 1-9, the first compressor is a variable speed compressor and the second compressor is a constant speed compressor.

[0087] In a preferred embodiment, in the system according to any one of aspects 1 to 9, both the first compressor and the second compressor are constant-speed compressors.

[0088] In a preferred embodiment, the system according to any one of aspects 1-9, wherein both the first compressor and the second compressor are scroll compressors.

[0089] In a preferred embodiment, in the system according to any one of aspects 1-12, the first compressor includes a first motor and a first housing; the first motor includes a first rotor and a first stator, a first gap is located between the first housing and the first stator, and a second gap is located between the first stator and the first rotor.

[0090] In a preferred embodiment, according to the system of aspect 13, the second compressor includes a second motor and a second housing, the second motor includes a second rotor and a second stator, a third gap is located between the second housing and the second stator, and a fourth gap is located between the second stator and the second rotor.

[0091] In a preferred embodiment, the system according to any one of aspects 1 to 14, wherein the first displacement and the second displacement are in the range of from or about 10 tons to or about 25 tons.

[0092] The terminology used in this specification is intended to describe particular embodiments and is not intended to be limiting. Unless otherwise expressly stated, the terms "a," "an," and "the" also include the plural forms. The terms "comprising" and / or "including" as used in this specification specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, and / or components.

[0093] Regarding the foregoing description, it should be understood that changes may be made in details, particularly in terms of the structural materials used and the shape, size, and arrangement of components, without departing from the scope of this disclosure. This specification and the described embodiments are merely exemplary, and the true scope and spirit of this disclosure are indicated by the appended claims.

Claims

1. A heating, ventilation, air conditioning and refrigeration (HVACR) system, characterized in that, The system includes: A first compressor, a second compressor, a condenser, an expander, and an evaporator are fluidly connected, wherein the first compressor has a first displacement and the second compressor has a second displacement; The first compressor and the second compressor are arranged in parallel. The first compressor includes a first lubricant reservoir; The second compressor includes a second lubricant reservoir; The first lubricant storage tank is fluidly connected to the second lubricant storage tank via a lubricant delivery pipeline, and a flow limiter is installed in the lubricant delivery pipeline; The flow restrictor includes a blocking region configured to reduce refrigerant flow between the first compressor and the second compressor; The flow limiter is located near the middle of the lubricant delivery pipeline; The current limiter includes a top portion having a first opening, a middle portion having a second opening, and a bottom portion having a second opening.

2. The system according to claim 1, characterized in that, The flow restrictor is configured to have a predetermined porosity to reduce the refrigerant flow rate between the first compressor and the second compressor to a predetermined level.

3. The system according to claim 1, characterized in that, The current limiter is a perforated baffle.

4. The system according to claim 1, characterized in that, The porosity of the flow limiter is configured to maintain the oil discharge rate of the system at a level equal to or less than 2.5%.

5. The system according to claim 1, characterized in that, The porosity of the flow limiter is configured to maintain the oil discharge rate of the system at a level equal to or less than 1%.

6. The system according to claim 1, characterized in that, The first compressor includes a first suction port; the second compressor includes a second suction port; the first suction port is fluidly connected to a first suction pipe; the second suction port is fluidly connected to a second suction pipe; When the first displacement is less than the second displacement, the first intake pipe is configured to be connected to the main pipe of the evaporator; The second intake pipe is configured to branch off from the main pipe.

7. The system according to claim 1, characterized in that, It also includes a third compressor with a third lubricant reservoir; The first compressor, the second compressor, and the third compressor are arranged in parallel. The second lubricant reservoir is fluidly connected to the third lubricant reservoir via a second lubricant delivery pipe; and The second flow limiter is installed in the second lubricant delivery pipe.

8. The system according to claim 1, characterized in that, The first compressor is a variable speed compressor, and the second compressor is a constant speed compressor.

9. The system according to claim 1, characterized in that, Both the first compressor and the second compressor are constant speed compressors.

10. The system according to claim 1, characterized in that, Both the first compressor and the second compressor are scroll compressors.

11. The system according to claim 1, characterized in that, The first compressor includes a first motor and a first housing; the first motor includes a first rotor and a first stator, a first gap is located between the first housing and the first stator, and a second gap is located between the first stator and the first rotor.

12. The system according to claim 11, characterized in that, The second compressor includes a second motor and a second housing. The second motor includes a second rotor and a second stator. A third gap is located between the second housing and the second stator, and a fourth gap is located between the second stator and the second rotor.

13. The system according to claim 1, characterized in that, The first displacement and the second displacement are in the range of 10 tons or about 25 tons.

14. The system according to claim 1, characterized in that, The flow restrictor includes an opening, the ratio of which to the area of ​​the total area including the blocking region and the opening is configured to generate resistance to control the flow of refrigerant in the lubricant delivery conduit, such that the upward flow of refrigerant does not prevent the lubricant from flowing downward into the first lubricant tank or the second lubricant tank.

15. The system according to claim 14, characterized in that, It also includes a suction pipe connected to the first compressor and the second compressor. Wherein, the first displacement is greater than the second displacement, and the intake pipe is configured to allow the lubricant to return to the second compressor more easily than to the first compressor.

16. The system according to claim 1, characterized in that, The porosity of the flow limiter is configured to maintain the lubricant circulation rate of the system at or below a predetermined level.

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