Oil-free bearing liquid supply air-conditioning system and control method therefor

Abstract

Disclosed are an oil-free bearing liquid supply air-conditioning system and a control method therefor. The system includes a compressor, a condenser, an evaporator, a first refrigeration liquid supply path for bearing lubrication from the condenser to the compressor, a second refrigeration liquid supply path for bearing lubrication from the condenser to the compressor, and a communication pipeline arranged between the condenser and the evaporator, the communication pipeline including a first solenoid valve. At least two refrigeration liquid pumps are arranged in the second refrigeration liquid supply path for bearing lubrication, the at least two refrigeration liquid pumps are arranged in parallel, and the at least two refrigeration liquid pumps include a main refrigeration liquid pump and at least one standby refrigeration liquid pump.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation of international application of PCT application serial no. PCT / CN2023 / 112986 filed on Aug. 14, 2023, which claims the priority benefit of China application serial No. 202222917498.0 filed on Nov. 2, 2022 and China application No. 202211364763.5 filed on Nov. 2, 2022. The entirety of each of the above-mentioned patent applications is hereby incorporated by reference herein and made a part of this specification.BACKGROUNDTechnical Field

[0002] The present application relates to the field of air conditioning technologies, and in particular, to an oil-free bearing liquid supply air-conditioning system and a control method therefor.Description of Related Art

[0003] Currently, a compressor is a main component of an air conditioner, an oil lubrication mode of a bearing is dominant in centrifugal water chilling units, but due to existence of lubricating oil, an oil lubrication system and an oil separation system for supplying and returning the oil are required to be considered during designing of the water chilling unit, so that complexity of designing, manufacture, maintenance, and control is increased, a huge initial cost and running and maintenance cost are increased, and environmental pollution may be caused by leakage of the lubricating oil. In addition, the lubricating oil entering an evaporator and a condenser along with a refrigerant will affect the heat exchange effect and system energy efficiency and lead to a performance degradation of the unit after long-term running.SUMMARY

[0004] In a first aspect, an oil-free bearing liquid supply air-conditioning system is provided, including: a compressor, a condenser, an evaporator, a first refrigerant liquid supply path for bearing lubrication from the condenser to the compressor, a second refrigerant liquid supply path for bearing lubrication from the condenser to the compressor, and a communication pipeline arranged between the condenser and the evaporator, the communication pipeline including a first solenoid valve, the first solenoid valve being configured to control connecting and disconnecting of the communication pipeline. At least two refrigeration liquid pumps are arranged in the second refrigerant liquid supply path for bearing lubrication, the at least two refrigeration liquid pumps are arranged in parallel, and the at least two refrigeration liquid pumps include a main refrigeration liquid pump and at least one standby refrigeration liquid pump. The system further includes a controller configured to: before the refrigeration system is started, open the first solenoid valve; in a starting stage, turn on the main refrigeration liquid pump and close the first solenoid valve; in a stable running stage, in a case where a pressure difference of the refrigeration system is greater than a sum of a minimum allowable bearing liquid supply pressure difference and an upward offset value of a bearing liquid supply pressure difference, and a duration thereof is greater than a first set time, turn off the main refrigeration liquid pump; supply liquid to a bearing of the compressor with the first refrigerant liquid supply path for bearing lubrication; in the stable running stage, in a case where the pressure difference of the refrigeration system is less than or equal to a sum of the minimum allowable bearing liquid supply pressure difference and the upward offset value of the bearing liquid supply pressure difference, or the pressure difference of the refrigeration system is greater than the sum of the minimum allowable bearing liquid supply pressure difference and the upward offset value of the bearing liquid supply pressure difference, and a duration thereof is less than or equal to the first set time, maintain the main refrigeration liquid pump turned on; and supply liquid to the bearing of the compressor with the second refrigerant liquid supply path for bearing lubrication.

[0005] In a second aspect, a control method for an oil-free bearing liquid supply air-conditioning system applied in the air-conditioning system is provided. The air-conditioning system includes: a compressor, a condenser, an evaporator, a first refrigerant liquid supply path for bearing lubrication from the condenser to the compressor, a second refrigerant liquid supply path for bearing lubrication from the condenser to the compressor, and a communication pipeline arranged between the condenser and the evaporator, the communication pipeline including a first solenoid valve, the first solenoid valve being configured to control connecting and disconnecting of the communication pipeline. At least two refrigeration liquid pumps are arranged in the second refrigerant liquid supply path for bearing lubrication, the at least two refrigeration liquid pumps are arranged in parallel, and the at least two refrigeration liquid pumps include a main refrigeration liquid pump and at least one standby refrigeration liquid pump. The control method including: before the refrigeration system is started, opening the first solenoid valve; in a starting stage, turning on the main refrigeration liquid pump and closing the first solenoid valve; in a stable running stage, in a case where a pressure difference of the refrigeration system is greater than a sum of a minimum allowable bearing liquid supply pressure difference and an upstream offset value of a bearing liquid supply pressure difference, and a duration thereof is greater than a first set time, turning off the main refrigeration liquid pump; supplying liquid to a bearing of the compressor with the first refrigerant liquid supply path for bearing lubrication; in the stable running stage, in a case where the pressure difference of the refrigeration system is less than or equal to the sum of the minimum allowable bearing liquid supply pressure difference and the upward offset value of the bearing liquid supply pressure difference, or the pressure difference of the refrigeration system is greater than the sum of the minimum allowable bearing liquid supply pressure difference and the upstream offset value of the bearing liquid supply pressure difference, and a duration thereof is less than or equal to the first set time, maintaining the main refrigeration liquid pump turned on; and supplying liquid to the bearing of the compressor with the second refrigerant liquid supply path for bearing lubrication.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG. 1 is a system block diagram of an oil-free bearing liquid supply air-conditioning system according to some embodiments of the present application;

[0007] FIG. 2 is a block diagram of a compressor system according to some embodiments of the present application;

[0008] FIG. 3 is a structural diagram of a refrigeration system according to some embodiments of the present application;

[0009] FIG. 4 is a partial structural diagram of a liquid supply source according to some embodiments of the present application;

[0010] FIG. 5 is a partial structural diagram of another liquid supply source according to some embodiments of the present application;

[0011] FIG. 6 is a partial structural diagram of the refrigeration system according to some embodiments of the present application;

[0012] FIG. 7 is a partial path structural diagram of the refrigeration system according to some embodiments of the present application;

[0013] FIG. 8 is an overall structural diagram of the refrigeration system according to some embodiments of the present application;

[0014] FIG. 9 is a flow chart of steady starting of the refrigeration system according to some embodiments of the present application; and

[0015] FIG. 10 is a flow chart of a shutdown and power-off process of the refrigeration system according to some embodiments of the present application.DESCRIPTION OF THE EMBODIMENTS

[0016] Some embodiments of the present disclosure are clearly and completely described below with reference to the accompanying drawings, and apparently, the described embodiments are not all but only a part of the embodiments of the present disclosure. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present disclosure shall fall within the protection scope of the present disclosure.

[0017] Unless required otherwise in the context, throughout the specification and the claims, the term “comprise” and its other forms such as “comprises” and “comprising” are interpreted as open and inclusive meaning “including, but not limited to”. In the description of the specification, the terms “one embodiment”, “some embodiments”, “exemplary embodiments”, “example”, “specific example”, “some examples”, or the like, are intended to indicate that a particular feature, structure, material, or characteristic in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. The schematic representations of the above terms do not necessarily refer to the same embodiment or example. In addition, the particular feature, structure, material, or characteristic may be included in any suitable manner in any one or more embodiments or examples.

[0018] Hereinafter, the terms such as “first” and “second” are used herein for purposes of description and are not intended to indicate or imply relative importance or significance or to imply the number of indicated technical features. Thus, the feature defined with “first” and “second” may include one or more of this feature explicitly or implicitly. In the description of the embodiments of the present disclosure, “a plurality” means two or more unless otherwise specified.

[0019] In describing some embodiments, the expressions “coupled” and “connected” along with their derivatives may be used. The term “connected” is to be interpreted broadly, and for example, “connected” may be a fixed connection, a detachable connection, or an integral connection; it may be a direct connection or indirect connection via an intermediate medium. For example, the term “coupled” indicates that two or more components are in direct physical contact or electrical contact.

[0020] The terms “coupled” or “communicatively coupled” may also mean that two or more components are not in direct contact with each other, but yet still cooperate or interact with each other. The embodiments disclosed herein are not necessarily limited to the contents herein.

[0021] “A and / or B” includes the following three combinations: A alone, B alone, and a combination of A and B.

[0022] The use of “adapted to” or “configured for” herein means open and inclusive languages and does not exclude devices adapted to or configured for performing additional tasks or steps.

[0023] Additionally, since a process, step, calculation, or other action that is “based on” one or more stated conditions or values may, in practice, be based on additional conditions or exceed the stated values, the use of “based on” is open and inclusive.

[0024] Currently, an oil lubrication mode of a bearing is dominant in centrifugal water chilling units, but due to existence of lubricating oil, an oil lubrication system and an oil separation system for supplying and returning the oil are required to be considered during designing of the water chilling unit, so that complexity of designing, manufacture, maintenance, and control is increased, an initial cost and running and maintenance cost are increased, and environmental pollution may be caused by leakage of the lubricating oil. In addition, the lubricating oil entering an evaporator and a condenser with a refrigerant will affect the heat exchange effect and system energy efficiency and lead to a performance degradation of the unit after long-term running.

[0025] Oil lubricated bearing centrifuges account for about 82% in the current market of central air-conditioning centrifuge units, but since the lubricating oil is required to be used to lubricate the bearing in a system thereof, the oil lubrication system and the oil separation system for supplying and returning the oil are required to be considered during the designing of the water chilling unit, so that the complexity of designing, manufacture, maintenance, and control is increased, the huge initial cost and running and maintenance cost are increased, and the environmental pollution may be caused by the leakage of the lubricating oil. In addition, the lubricating oil entering the evaporator and the condenser along with the refrigerant will affect the heat exchange effect and the system energy efficiency and lead to a performance degradation of the unit after the long-term running.

[0026] In view of the above corresponding disadvantages of the oil-containing centrifuge, the centrifuge is gradually developed towards a lubricating oil-free system, and oil-lubricating system assemblies are eliminated in an oil-free centrifuge unit, thereby avoiding a performance reduction of a heat exchanger caused by oil pollution, and also simplifying the structure of the system, and the oil-free centrifuge unit receives more attention in the heating, ventilating and air conditioning industry.

[0027] Currently, there are three main development directions for the oil-free centrifuge, one of which is an oil-free centrifuge unit with a magnetic suspension bearing. Due to a large number of sensors and complex control system, the magnetic suspension bearing cannot completely solve the problem of reliability of the unit when power is suddenly cut off.

[0028] The second direction is an oil-free centrifuge unit with an air bearing. Since the air bearing is only suitable for a high-speed light-load working condition, a cooling capacity of the oil-free centrifuge unit with the air bearing is limited, and reliability is poor when a load is suddenly changed.

[0029] The third direction is an oil-free centrifuge unit with a ceramic bearing lubricated by refrigerant liquid, and a refrigerant is used as a lubricating medium to lubricate the ceramic bearing in the system, so that on the one hand, a control system is simple, a system design is simplified, and on the other hand, shock resistance of the ceramic bearing is strong, and development of a large-cooling capacity oil-free centrifuge can be realized. Based on the advantages of the last development direction of the oil-free centrifuge, the refrigerant-lubricated rolling ceramic bearing is increasingly researched and applied in the centrifuge unit.

[0030] In the ceramic bearing oil-free centrifuge unit, the refrigerant is used as the bearing lubrication medium, and different from lubricating oil with high viscosity as the bearing lubrication medium, the viscosity of the refrigerant is quite low, and taking refrigerant R134a as an example, a value thereof is 0.162 cst at 25° C. and is about 1 / 100 of viscosity of the lubricating oil. When refrigerant supply is interrupted, low-viscosity refrigerant liquid is difficult to keep on a bearing surface, and even if a part of the refrigerant remains on the bearing surface, the refrigerant is subjected to a phase change and evaporated due to a volatile property of the refrigerant. In addition, when the refrigerant liquid is conveyed and supplied to the bearing in the compressor, the refrigerant liquid is prone to flash evaporation due to throttling cause by on-way resistance and local resistance in the conveying process, so as to generate refrigerant gas, and when the refrigerant gas enters the bearing to lubricate the bearing, a rolling body in the bearing is prone to be seriously abraded, thereby seriously affecting a service life of the bearing and running stability of the compressor. In summary, when the refrigerant is used as the medium for lubricating the bearing, the unit is required to ensure continuity and stability of supply of the refrigerant liquid in a startup stage, a running stage, and a shutdown stage to ensure a lubrication state of the bearing in the compressor.

[0031] Based on this, some embodiments of the present application provide an oil-free bearing liquid supply air-conditioning system and a control method therefor. In the oil-free bearing liquid supply air-conditioning system, refrigerant liquid is used to replace lubricating oil to lubricate the bearing in the compressor, and different refrigerant liquid supply sources and paths are adopted according to different running states of a refrigeration system, including two modes of natural liquid supply by a condenser high pressure difference existing during running of the refrigeration system and forced liquid supply by additionally providing power by using a refrigeration liquid pump. Through the two different refrigerant liquid supply modes and the control method, it is ensured that the bearing can obtain sufficient refrigerant liquid supply at each stage of running of the oil-free refrigeration system, and the lubrication state thereof can be effectively ensured to further ensure normal running of the oil-free refrigeration system.

[0032] FIG. 1 is a system block diagram of an oil-free bearing liquid supply air-conditioning system according to some embodiments of the present application, FIG. 2 is a block diagram of a compressor system according to some embodiments of the present application, and FIG. 3 is a structural diagram of a refrigeration system according to some embodiments of the present application.

[0033] As shown in FIG. 1, some embodiments of the present application provide an oil-free bearing liquid supply air-conditioning system 1000, including: a box system 200, a refrigeration system 31, and a controller 100, the refrigeration system 31 being located in the box system 200.

[0034] The refrigeration system 31 includes the following components.

[0035] A compressor 42 is a core of the refrigeration system, and is configured to compress a gas-phase refrigerant in a low-temperature and low-pressure state and discharge a compressed gas-phase refrigerant in a high-temperature and high-pressure state. The compressor 42 sucks low-temperature and low-pressure refrigerant gas from a gas suction pipe, a motor runs to drive an impeller to rotate, so as to increase a gas speed, and a pressure of the gas is greatly increased after the gas is diffused by a diffuser, thereby providing power for a refrigeration cycle.

[0036] An economizer 23 is configured to expand a liquid-phase refrigerant in the high-pressure state into a gas-liquid two-phase refrigerant in a medium-pressure state. In some embodiments, the economizer 23 is a tank container arranged in the system, and has a corresponding structural design therein. After the refrigerant liquid enters the economizer, a flash vaporization phenomenon occurs. The flash vaporization can generate a refrigerant gas working medium, the gas working medium can enter the compressor 42 along a gas supplementing pipeline to supplement gas for the compressor 42, and the residual gas-liquid two-phase refrigerant after the flash vaporization flows out of the economizer 23.

[0037] An evaporator 29 is configured to absorb heat from an ambient environment and evaporate the gas-liquid two-phase refrigerant in the medium-pressure state into the low-temperature and low-pressure gas-phase refrigerant, and the gas-phase refrigerant in the low-temperature and low-pressure state is returned to the compressor 42. The evaporator includes a heating chamber and an evaporation chamber. The heating chamber is configured to provide the heat required for evaporation for the liquid, so as to boil and vaporize the liquid; and the evaporation chamber is configured to completely separate the gas-phase refrigerant from the liquid-phase refrigerant.

[0038] A condenser 19 is a heat exchanger, and is configured to condense the high-temperature and high-pressure gas-phase refrigerant into the liquid-phase refrigerant in the high-pressure state, and heat is released to the ambient environment with the condensation process.

[0039] A subcooler 35 is configured as a heat exchanger that further cools saturated liquid without a phase change.

[0040] A refrigeration liquid pump 20 is configured to provide sufficient delivery power for the refrigerant when a pressure difference naturally established during system running is insufficient to serve as liquid supply power, so as to cause the refrigerant liquid to be supplied from a low position in the system at a sufficient flow rate to a compressor bearing at a high position in the system.

[0041] A first refrigerant liquid supply path 125 for bearing lubrication is from the condenser 19 to the compressor 42, and a second refrigerant liquid supply path 126 for bearing lubrication is from the condenser 19 to the compressor 42 (as shown in FIG. 3). It can be understood that the first path 125 and the second path 126 may be implemented through pipelines. At least a part of the first refrigerant liquid supply path 125 for bearing lubrication and at least a part of the second refrigerant liquid supply path 126 for bearing lubrication are connected in parallel, and at least parts of the paths are shared. The second refrigerant liquid supply path for bearing lubrication for the compressor 42 further includes the refrigeration liquid pump 20. The subcooler 35 is arranged on the shared path of the first refrigerant liquid supply path 125 for bearing lubrication and the second refrigerant liquid supply path 126 for bearing lubrication. Both the first refrigerant liquid supply path 125 for bearing lubrication and the second refrigerant liquid supply path 126 for bearing lubrication are configured to transport the refrigerant liquid to the compressor 42 to lubricate the bearing of the compressor 42. The controller 100 is configured to be in communication connection with the refrigeration system 31, and the controller 100 is configured to control the refrigeration system 31.

[0042] In the embodiments of the present application, the controller 100 is an apparatus capable of generating an operation control signal according to an instruction operation code and a timing signal, and instructing the refrigeration system to execute a control instruction. Exemplarily, the controller may be a central processing unit (CPU), a general-purpose processor, a network processor (NP), a digital signal processor (DSP), a microprocessor, a microcontroller, a programmable logic device (PLD), or any combination thereof. The controller may alternatively be other apparatuses with processing functions such as a circuit, a device, or a software module, which is not limited in some embodiments of the present application. The instruction operation code is a preset control logic program, a corresponding action logic can be stored in the controller through programming and includes a series of judgment conditions and execution actions, and when the corresponding judgment conditions are met in a running process of the unit, relevant actions are executed to control relevant components in the refrigeration system to act.

[0043] In addition, the controller 100 is configured to control the components in the refrigeration system 31 to work, so as to cause the components of the refrigeration system 31 to run to achieve predetermined functions of the air-conditioning system.

[0044] A pump is a component for conveying fluid or pressurizing fluid, and transfers mechanical energy of a prime mover or other external energy to the liquid, so as to increase energy of the liquid. The above refrigeration liquid pump is configured to forcibly pump the refrigerant liquid and supply the liquid to the compressor 42 through the second refrigerant liquid supply path 126 for bearing lubrication.

[0045] It should be noted that, for example, 11˜12 shown in the drawings of the present application indicates that component 11 belongs to component 12. For example, 105˜126 indicates that path 105 belongs to the path 126, 110˜125 / 126 indicates that path 110 belongs to the path 125 or the path 126, and other similar reference numerals shown in the figures follow the above description.

[0046] As shown in FIG. 2, in some embodiments, the compressor 42 includes:

[0047] a motor 4 which is the prime mover of the compressor 42 and configured to provide power for working and running of the compressor 42, where a stator structure formed by winding coils, or the like, in the motor 4 can generate a magnetic field when power is supplied, and a rotor structure in the motor 4 can rotate under the action of the magnetic field to provide a driving force for a rotating component in the compressor 42;

[0048] a bearing 3, the bearing 3 being located on the motor 4 and configured to provide support for a rotor in the motor 4, reduce a friction coefficient in a rotation process of the rotor and ensure revolution precision of the rotor; and

[0049] impellers (e.g., a first-stage impeller 1 and a second-stage impeller 2), a “back-to-back” impeller arrangement form being adopted for double impellers. With such an impeller arrangement form, axial loads generated in the two stages or multiple stages of impellers are mutually counteracted and then balanced.

[0050] Both the first refrigerant liquid supply path for bearing lubrication and the second refrigerant liquid supply path for bearing lubrication are configured to transport the refrigerant liquid to the compressor 42 to lubricate the bearing 3 of the motor 4 in the compressor 42.

[0051] In some embodiments, the compressor is a two-stage centrifugal compressor which means that the compressor includes two stages of impellers. A centrifugal compressor, also known as a turbine compressor, is mainly configured to compress gas and includes a rotor and a stator. The rotor includes an impeller and a shaft, and the impeller is provided with blades, a balance disc, and a part of a shaft seal. A main body of the stator is a cylinder, and the stator further includes a diffuser, a curve, a reflux device, a gas inlet pipe, an exhaust pipe, or the like. When the impeller rotates at a high speed, the gas rotates with the impeller, the gas is thrown into the diffuser behind the impeller under the action of a centrifugal force, a vacuum zone is formed at the impeller, and in this case, external fresh gas enters the impeller. The impeller rotates continuously, and the gas is sucked and thrown out continuously, thereby maintaining continuous flowing of the gas.

[0052] In some embodiments, the motor is a permanent magnet motor, and the rotor of the permanent magnet motor can stop rotating in a short time after power failure and shutdown.

[0053] In some embodiments, the bearing is a ceramic bearing which is corrosion resistant and suitable for use in a highly corrosive working environment. The ceramic is slightly affected by temperature differences and can withstand a large temperature difference. An elastic modulus of the ceramic bearing is high, and the ceramic bearing is rarely deformed due to stress. A ceramic ball has a lower density and a lighter weight than a steel ball, and can reduce friction generated by a centrifugal force during rotation and prolong a service life of the bearing.

[0054] In some embodiments, the subcooler may be a plate heat exchanger. The plate heat exchanger has a high heat exchange efficiency, and can realize large heat exchange by using a small heat exchange temperature difference, thereby effectively improving a subcooling degree of the refrigerant liquid. In addition, the plate heat exchanger has a small volume, occupying less space in the arrangement of the unit system, and a design of an arrangement solution is easy to realize.

[0055] The above embodiments of the present disclosure provide the refrigeration system, and as shown in FIG. 3, the refrigeration system 31 lubricates the bearing of the motor in the compressor through the refrigerant liquid, and provides two refrigerant liquid supply paths. The two refrigerant liquid supply paths are the first refrigerant liquid supply path 125 for bearing lubrication from the condenser 19 to the compressor 42 and the second refrigerant liquid supply path 126 for bearing lubrication from the condenser 19 to the compressor 42 respectively. That is, both the refrigerant liquid supply paths for bearing lubrication transport the refrigerant liquid generated by the condenser 19 to the compressor 42, and in the two liquid supply paths, the first refrigerant liquid supply path 125 for bearing lubrication is a path without the need of the refrigeration liquid pump 20, and the second refrigerant liquid supply path 126 for bearing lubrication requires the refrigeration liquid pump 20 to provide power, so that in the whole running process of the refrigeration system, different liquid supply paths can be selected at different stages according to the running state of the refrigeration system, thereby ensuring that the bearing in the compressor can obtain sufficient refrigerant liquid for lubrication at each stage, and ensuring safety of system running. Meanwhile, the subcooler 35 is communicated to the shared path of the first refrigerant liquid supply path 125 for bearing lubrication and the second refrigerant liquid supply path 126 for bearing lubrication, and the subcooler 35 is configured to further condense the refrigerant liquid, so as to better lubricate the bearing of the compressor 42.

[0056] As shown in FIG. 1 and FIG. 3, each of the first refrigerant liquid supply path for bearing lubrication and the second refrigerant liquid supply path for bearing lubrication includes a first section path 120, a front section path 104 / 105, a rear section path 110, and a last section path 121 that are communicated with each other. The front section path 104 of the first refrigerant liquid supply path for bearing lubrication and the front section path 105 of the second refrigerant liquid supply path for bearing lubrication are arranged in parallel, the first section path 120 of the first refrigerant liquid supply path for bearing lubrication and the first section path 120 of the second refrigerant liquid supply path for bearing lubrication are the same path, the rear section path 110 of the first refrigerant liquid supply path for bearing lubrication and the rear section path 110 of the second refrigerant liquid supply path for bearing lubrication are the same path, and the last section path 121 of the first refrigerant liquid supply path for bearing lubrication and the last section path 121 of the second refrigerant liquid supply path for bearing lubrication are the same path.

[0057] That is to say, as shown in FIG. 1 and FIG. 3, the first refrigerant liquid supply path for bearing lubrication and the second refrigerant liquid supply path for bearing lubrication are connected in parallel at the front section parts, and combined into one at the first section part, the rear section part, and the lase section part, and both paths transport the refrigerant liquid to the bearing in the compressor through the last section path 121. On the one hand, such an arrangement form reduces pipeline arrangements in the unit system, and realizes combination simplification of the first refrigerant liquid supply path for bearing lubrication and the second refrigerant liquid supply path for bearing lubrication by using a common pipeline section. On the other hand, such an arrangement form makes it easier to maintain the pipelines of the unit system, and when the pipelines of the unit system fail, it is not necessary to overhaul multiple sections of the pipelines complicatedly.

[0058] The first section path 120 of the first refrigerant liquid supply path for bearing lubrication includes a first filter 34. The front section path 104 of the first refrigerant liquid supply path for bearing lubrication includes a first check valve 11. The front section path 105 of the second refrigerant liquid supply path for bearing lubrication includes the refrigeration liquid pump 20. The rear section path 110 of the first refrigerant liquid supply path for bearing lubrication includes a pressure regulating valve 10 and a second filter 9 which are arranged in sequence, and the subcooler 35 communicates the rear section path 110 of the first refrigerant liquid supply path for bearing lubrication with the last section path 121 of the first refrigerant liquid supply path for bearing lubrication.

[0059] It should be noted that the refrigeration system includes a plurality of circulation paths, such as liquid circulation paths and gas circulation paths. The circulation paths include a plurality of transport components and communication pipelines, and the transport components may include, for example, check valves, filters, pumps, etc. Liquid or gas can pass through the transport components, and the communication pipelines communicate adjacent transport components to allow the liquid or gas to circulate.

[0060] As shown in FIG. 3, the refrigerant liquid passes through the first filter 34, the first check valve 11, the pressure regulating valve 10, the second filter 9, and the subcooler 35 in sequence when circulating in the first refrigerant liquid supply path for bearing lubrication. The refrigerant liquid passes through the first filter 34, the refrigeration liquid pump 20, the pressure regulating valve 10, the second filter 9, and the subcooler 35 in sequence when circulating in the second refrigerant liquid supply path for bearing lubrication.

[0061] The transport components in the two liquid supply paths have the following functions: the first filter 34 is configured to filter impurities such as solid particulates from the refrigerant liquid in the first section path 120 of the first refrigerant liquid supply path for bearing lubrication, the first check valve 11 is configured to prevent reverse flowing of the refrigerant liquid in the front section path 104 of the first refrigerant liquid supply path for bearing lubrication, the second filter 9 is configured to filter minor impurities such as solid particulates from the refrigerant liquid in the rear section path 110 of the first refrigerant liquid supply path for bearing lubrication, and the pressure regulating valve 10 is configured to regulate pressure intensity in the rear section path 110 of the first refrigerant liquid supply path for bearing lubrication, thereby fixing the pressure intensity. The subcooler 35 is configured to subcool the refrigerant liquid in the rear section path 110 of the first refrigerant liquid supply path for bearing lubrication, and then supply the liquid to the bearing of the compressor 42 via the last section path 121 of the first refrigerant liquid supply path for bearing lubrication.

[0062] In some embodiments, the front section path of the second refrigerant liquid supply path for bearing lubrication includes at least two refrigeration liquid pumps, and the at least two refrigeration liquid pumps are arranged in parallel. For example, as shown in FIG. 3, the at least two refrigeration liquid pumps 20 include a main refrigeration liquid pump 201 and at least one standby refrigeration liquid pump 202.

[0063] The plurality of refrigeration liquid pumps which are connected in parallel are arranged on the second refrigerant liquid supply path for bearing lubrication, so that the condition that one or more refrigeration liquid pumps cannot supply liquid to the bearing during a failure or overloading in the running process of the system can be avoided, and when the condition occurs, the system can rapidly switch to the standby refrigeration liquid pump path which runs normally, so as to ensure normal realization of liquid supply of the bearing. In some embodiments, the controller 100 is respectively connected to the main refrigeration liquid pump 201 and the at least one backup refrigeration liquid pump 202. When the controller 100 determines that the condition for activating the main refrigeration liquid pump is met, the controller 100 sends a start signal to the main refrigeration liquid pump to activate the main refrigeration liquid pump. When the controller 100 determines that the condition for switching to the standby refrigerant liquid pump is met (e.g., when the controller 100 determines that the main refrigerant liquid pump is failed based on a detection result of a pressure difference between the bearing inlet and the bearing outlet), a stop signal is sent to the main refrigerant liquid pump, and a start signal is sent to the corresponding standby refrigerant liquid pump to activate the standby refrigerant liquid pump. The above switching conditions will be described below.

[0064] In some embodiments, the refrigeration liquid pump 20 is powered using an uninterruptible power supply (UPS).

[0065] The UPS includes an energy storage apparatus. The UPS is mainly used for providing uninterruptible power for some devices with higher requirements on power supply stability. Thus, even if the air-conditioning system is powered off, the refrigeration liquid pump can normally work under the action of the UPS to pump out the refrigeration liquid, and then, the bearing in the motor of the compressor is continuously lubricated.

[0066] In some embodiments, a tail end of the last section path 121 of the first refrigerant liquid supply path for bearing lubrication is divided into two branches: a bearing lubrication liquid supply branch path 111 and a bearing lubrication liquid supply branch path 112. The two branches are configured to lubricate two oppositely arranged bearings 3 in the motor 4.

[0067] FIG. 4 is a partial structural diagram of a liquid supply source in some embodiments of the present application, and FIG. 5 is a partial structural diagram of another liquid supply source in some embodiments of the present application.

[0068] The refrigeration system 31 further includes a same liquid supply source, and as shown in FIG. 4 and FIG. 5, the liquid supply source is a first liquid supply bag 13 arranged below the condenser 19. The first liquid supply bag 13 is connected to the condenser 19 and is configured to store the refrigerant liquid in the condenser 19. The first section path 120 of the first refrigerant liquid supply path for bearing lubrication is communicated with the first liquid supply bag 13, and the first section path 120 of the second refrigerant liquid supply path for bearing lubrication is communicated with the first liquid supply bag 13.

[0069] Since the condenser 19 has a subcooling pipe section, the refrigerant liquid in the first liquid supply bag 13 is a subcooling-state refrigerant liquid, and the subcooling-state refrigerant liquid is supplied to lubricate the bearing 3, so as to ensure that the supplied liquid contains little or no gas and has a good cooling effect.

[0070] FIG. 6 is a partial structural diagram of the refrigeration system in some embodiments of the present application, and FIG. 7 is a partial path structural diagram of the refrigeration system in some embodiments of the present application.

[0071] As shown in FIG. 6, the refrigeration system 31 further includes: a communication pipeline 103 provided between the condenser 19 and the evaporator 29, and the communication pipeline 103 includes a first solenoid valve 33.

[0072] After the refrigeration system 31 is shut down, the first solenoid valve 33 is opened to realize rapid balance between a high pressure of the condenser 19 and a low pressure of the evaporator 29 via the communication pipeline 103 between the condenser 19 and the evaporator 29, so as to ensure that there is sufficient refrigerant liquid in the evaporator 29 and the condenser 19. That is, in this stage, it can also be ensured that there is sufficient refrigerant liquid in the first liquid supply bag 13.

[0073] In some embodiments, as shown in FIG. 6 and FIG. 7, the refrigeration system 31 further includes: a bearing lubrication liquid return or gas return path 118 from the compressor 42 to the evaporator 29 and a first exhaust path 119 from the compressor 42 to the condenser 19. The bearing lubrication liquid return or gas return path 118 from the compressor 42 to the evaporator 29 includes a second solenoid valve 12, and the second solenoid valve 12 is configured to control connecting and disconnecting of the bearing lubrication liquid return or gas return path 118.

[0074] As shown in FIG. 6, the refrigeration system 31 further includes: a first pressure sensor 15, a second pressure sensor 26, a third pressure sensor 8, a fourth pressure sensor 30, and a fifth pressure sensor 5. The first pressure sensor 15 is connected to the condenser 19 and configured to collect a pressure value of the condenser 19. For example, the first pressure sensor 15 is configured to measure a pressure value at the outlet of the condenser 19. The second pressure sensor 26 is connected to the evaporator 29 and configured to collect a pressure value of the evaporator 29. For example, the second pressure sensor 26 is configured to measure a pressure value at the inlet of the evaporator 29. The third pressure sensor 8 is connected to the last section path of the first refrigerant liquid supply path for bearing lubrication and configured to collect a bearing liquid supply pressure value. The fourth pressure sensor 30 is connected to the bearing lubrication liquid return or gas return path 118 and configured to collect a bearing lubrication liquid return or gas return pressure value. For example, the fourth pressure sensor 30 is located at the end of the bearing lubrication liquid return or gas return path 118 that is connected to the bearing outlet. The fifth pressure sensor 5 is connected to an exhaust port of the compressor 42 and configured to collect a compressor exhaust pressure.

[0075] As shown in FIG. 6 and FIG. 7, the refrigeration system further includes: a first liquid level sensor 17, a second liquid level sensor 22, a first temperature sensor 7, and a second temperature sensor 6. The first liquid level sensor 17 is configured to monitor a liquid level of the condenser 19. The second liquid level sensor 22 is configured to monitor a liquid level of the economizer 23. The first temperature sensor 7 is configured to monitor a temperature of the last section path 121 of the first refrigerant liquid supply path for bearing lubrication. The second temperature sensor 6 is configured to monitor a temperature of the exhaust path 119 from the compressor 42 to the condenser 19.

[0076] As shown in FIG. 7, the refrigeration system 31 further includes: the first exhaust path 119 from the compressor 42 to the condenser 19, a second exhaust path 102 from the evaporator 29 to the compressor 42, a motor cooling liquid supply path 108 from the condenser 19 to the compressor 42, a refrigerant supply path 106 from the condenser 19 to the economizer 23, a first gas supplementing path 109 from the economizer 23 to the compressor 42, a liquid return path 107 from the economizer 23 to the evaporator 29, a motor cooling gas return path 117 from the compressor 42 to the evaporator 29, a heat exchange path 122 from the condenser 19 to the subcooler 35, and a second gas supplementing path 123 from the subcooler 35 to the first gas supplementing path 109, or a subcooling gas return path from the subcooler 35 to the bearing lubrication liquid return or gas return path 118.

[0077] In some embodiments, the motor cooling gas return path 117 from the compressor 42 to the evaporator 29 is divided into two motor cooling gas return paths: a motor cooling gas return branch path 115 and a motor cooling gas return branch path 116.

[0078] In some embodiments, as shown in FIG. 7, the refrigeration system 31 further includes: a second liquid supply bag 14 arranged below the condenser 19. The second liquid supply bag 14 is connected to the condenser 19 and configured to store refrigerant liquid in the condenser 19, and the motor cooling liquid supply path 108 and the refrigerant supply path 106 are both connected to the second liquid supply bag 14.

[0079] The condenser 19 is connected to the two liquid supply bags, the first liquid supply bag 13 is connected to the first refrigerant liquid supply path for bearing lubrication and configured to provide the refrigerant liquid to the bearing in the compressor as a lubricant, and the refrigerant (liquid or gas), after lubricating the bearing, is returned to the evaporator 29 along the bearing lubrication liquid return or gas return path 118.

[0080] The second liquid supply liquid bag 14 is connected to the motor cooling liquid supply path 108 and the refrigerant supply path 106, and configured to provide the refrigerant liquid for the economizer 23. The economizer 23 performs heat exchange on the refrigerant liquid to generate refrigerant gas, and the refrigerant gas enters the compressor 42 along the first gas supplementing path 109 for gas supplementing. Meanwhile, the second gas supplementing path 123 from the subcooler 35 to the first gas supplementing path 109 supplements gas to the compressor via the first gas supplementing path 109. The remaining refrigerant liquid in the economizer 23 enters the evaporator 29 along the liquid return path 107. Meanwhile, the second liquid supply bag 14 is also configured to provide the refrigerant liquid for the motor in the compressor 42 for motor cooling, and the refrigerant (liquid or gas), after cooling the motor, returns to the evaporator 29 through the motor cooling gas return path 117.

[0081] The first exhaust path 119 from the compressor 42 to the condenser 19 is from the compressor 42 to the condenser 19 via an exhaust check valve 16 on the condenser 19. The second exhaust path 102 from the evaporator 29 to the compressor 42 is from a stop valve 27 on the evaporator 29 to the compressor 42 via a suction stop valve 28. The motor cooling liquid supply path 108 from the condenser 19 to the compressor 42 is from the second liquid supply liquid bag 14 below the condenser 19 to the compressor 42 sequentially through a drying filter 18 and a second electric regulating valve 32, and the cooling liquid supply path 108 is branched into a cooling liquid supply branch path 113 and a cooling liquid supply branch path 114 at a tail end. The refrigerant supply path 106 from the condenser 19 to the economizer 23 is from the second liquid supply bag 14 below the condenser 19 to the economizer 23 sequentially through a first electric regulating valve 37 and a first throttling orifice plate 21. The liquid return path 107 from the economizer 23 to the evaporator 29 is from the economizer 23 to the evaporator 29 sequentially through a third electric regulating valve 24 and a second throttling orifice plate 25. The heat exchange path 122 from the condenser 19 to the subcooler 35 is from the first liquid supply bag 13 below the condenser 19 to the subcooler 35 via an electronic expansion valve 36.

[0082] FIG. 8 is an overall structural diagram of the refrigeration system according to some embodiments of the present application, FIG. 9 is a flow chart of steady starting of the refrigeration system according to some embodiments of the present application, and FIG. 10 is a flow chart of a shutdown and power-off process of the refrigeration system according to some embodiments of the present application.

[0083] The refrigeration system in some embodiments of the present application includes the two different refrigerant liquid supply paths for bearing lubrication, the two refrigerant liquid supply paths for bearing lubrication are applied in different running stages of the refrigeration system, the control method for an oil-free bearing liquid supply air-conditioning system is included in different running stages of the refrigeration system, and the whole running stages of the refrigeration system include (as shown in FIG. 8 to FIG. 10):

[0084] (1) refrigeration-system starting stage;

[0085] (2) refrigeration-system stable running stage;

[0086] (3) refrigeration-system normal power-off shutdown stage; and

[0087] (4) refrigeration-system abnormal power-off shutdown stage.

[0088] In the stage (1) and the stage (3), the mode of forced liquid supply by the refrigeration liquid pump is adopted. In the stage (2), a pressure difference of the refrigeration system and a bearing liquid supply pressure difference are required to be compared to determine parallel or independent running of the two liquid supply modes of forced liquid supply by the refrigeration liquid pump and natural liquid supply by the pressure difference of the refrigeration system. In the stage (4), the mode of natural liquid supply by the pressure difference of the refrigeration system is first adopted, and if the pressure difference is insufficient, an emergency standby power supply is started, and then, the mode of forced liquid supply by the refrigeration liquid pump is adopted. The running process of the entire stage is described in detail below with reference to FIG. 8.

[0089] No matter what stage the refrigeration system is in, each sensor apparatus in the refrigeration system is always in a working state throughout the entire process. For example, the first pressure sensor 15 collects a pressure value of the condenser 19 in real time, and the pressure value collected by the first pressure sensor 15 is referred to as P1. The second pressure sensor 26 collect a pressure of the evaporator 29 in real time, and the pressure value collected by the second pressure sensor 26 is referred to as P2. The third pressure sensor 8 collects the bearing liquid supply pressure value at the last section path of the first refrigerant liquid supply path for bearing lubrication in real time, and the bearing liquid supply pressure value collected by the third pressure sensor is referred to as P3. The fourth pressure sensor 30 collects the bearing liquid return or gas return pressure in real time, and the bearing liquid return or gas return pressure value collected by the fourth pressure sensor 30 is referred to as P4. The first temperature sensor 7 collects a temperature of the last section path 121 of the first refrigerant liquid supply path for bearing lubrication, the temperature collected by the first temperature sensor 7 is referred to as a bearing liquid supply temperature in real time T3. The first liquid level sensor 17 collects the liquid level of the condenser 19 in real time, and the collected value thereof is set to Lcon. The subcooling degree of the liquid supplied to bearing is set to Tsub, and is calculated by the bearing liquid supply pressure value P3 and the bearing liquid supply temperature T3. A minimum allowable subcooling degree of the liquid supplied to bearing is set to Tmin, and the value of which is set according to actual conditions and can be set to 1° C. for example. A pressure difference ΔP of the refrigeration system is a difference between a pressure value of the condenser and a pressure value of the evaporator, i.e., the pressure difference of the refrigeration system is calculated according to the following formula: ΔP=P1−P2. The bearing liquid supply pressure difference ΔPbrg is a difference between the bearing liquid supply pressure value P3 and the bearing liquid return or gas return pressure value P4, i.e., the bearing liquid supply pressure difference is calculated according to the following formula: ΔPbrg=P3−P4. The minimum allowable bearing liquid supply pressure difference is set to ΔPmin, which ranges from 0.05 MPa to 0.35 MPa, and an exemplary value is 0.2 MPa. A liquid supply mode switching pressure difference judgment time is set to Ts1 (also referred to as a first set time), and the value of which is set according to actual conditions. In some embodiments, the first set time ranges from 5 seconds to 60 seconds, for example, the first set time Ts1 can be set to 1 min. An upward offset value of the bearing liquid supply pressure difference is set to Pup, which ranges from 0 MPa to 0.35 MPa and can be set to 0.15 MPa for example. A downward offset value of the bearing liquid supply pressure difference is set to Pdown, which ranges from 0 MPa to 0.35 MPa and can be set to 0.05 MPa for example. A failure alarm pressure difference judgment time is set to a second set time Ts2, and the value of which is set according to actual conditions and may be set to 30 s for example. A compressor power-off judgment time is set to a third set time Ts3, and the value of which is set according to actual conditions and may be set to 3 min for example. A minimum allowable liquid level of the condenser 19 is set to Lcmin, and the value of which is set according to the actual conditions and may be set to 30% for example.

[0090] In the whole running stage of the unit, whether the starting stage or the normal running stage, or the shutdown stage of the unit, each sensor apparatus in the refrigeration system can uninterruptedly collect relevant state parameter data such as the pressure, the temperature, and a refrigerant flow rate during the operation of the unit at a certain collection frequency.

[0091] It should be noted that the above values are preset before the refrigeration system is started.

[0092] In each of the following stages, an executive subject of each step is the controller, and the controller can control starting, stopping, running, or the like, of each device in the refrigeration system.1) Refrigeration-System Starting Stage

[0093] As shown in FIG. 8 and FIG. 9, before the whole refrigeration system 31 is started, a large amount of refrigerant liquid is accumulated in the evaporator 29 and the condenser 19 of the refrigeration system, the first solenoid valve 33 is opened in this case, and a communication pipe path 103 at the bottoms of the condenser 19 and the evaporator 29 is connected, so that a refrigerant liquid level is uniformly distributed in the evaporator and the condenser. In addition, since the condenser is arranged to be lower than the evaporator in the structural arrangement of the unit, it is ensured that the first liquid supply bag 13 below the condenser 19 is full of refrigerant liquid before the system is started. Since the first liquid supply bag 13 is located below the condenser 19, under the gravity, the refrigerant liquid can be automatically replenished into the first liquid supply bag 13 as long as the refrigerant liquid is present in the condenser 19.

[0094] As shown at S1 and S2 in FIG. 9, when the refrigeration system 31 is started, the controller 100 turns on the main refrigeration liquid pump 201, detects and closes the first solenoid valve 33 on a bottom communication pipe between the condenser 19 and the evaporator 29, and detects and opens the second solenoid valve 12 on the bearing liquid return (gas return) path 118.

[0095] In the case where the bearing liquid supply pressure difference ΔPbrg is greater than the minimum allowable bearing liquid supply pressure difference ΔPmin and a duration thereof is greater than the first set time Ts1, that is, ΔPbrg>ΔPmin and the duration>Ts1 are satisfied, the controller 100 controls the compressor 42 to run, and the liquid is supplied to the bearing of the compressor 42 with the second refrigerant liquid supply path 126 for bearing lubrication.

[0096] The main refrigeration liquid pump 201 pumps the refrigerant liquid continuously from the first liquid supply bag 13 which contains more refrigerant liquid, the refrigerant liquid passes through the first filter 34, the main refrigeration liquid pump 201, the pressure regulating valve 10, the second filter 9, and the subcooler 35 along the first section path 120 of the second refrigerant liquid supply path for bearing lubrication to the last section path 121 of the second refrigerant liquid supply path for bearing lubrication, and then is divided into two streams of the bearing lubrication liquid supply branch path 111 and the bearing lubrication liquid supply branch path 112 to lubricate the left and right bearings 3 in the compressor. After the bearings 3 are lubricated, the rotor gradually and stably rotates, the refrigeration system 31 is started. The refrigerant, after lubricating the bearings 3, returns to the evaporator 29 through the fourth pressure sensor 30 and the second solenoid valve 12 along the bearing lubrication liquid return path 118.

[0097] As shown at S2 and S5 in FIG. 9, in the case where the bearing liquid supply pressure difference ΔPbrg is less than or equal to the minimum allowable bearing liquid supply pressure difference ΔPmin, or the bearing liquid supply pressure difference ΔPbrg is greater than the minimum allowable bearing liquid supply pressure difference ΔPmin and the duration thereof is less than or equal to the first set time Ts1, that is, ΔPbrg>ΔPmin and the duration>Ts1 are not satisfied, the controller 100 determines that the running state of the main refrigeration liquid pump 201 is poor, and in this case, it switches to use the standby refrigeration liquid pump 202, and the liquid is also supplied to the bearing of the compressor 42 with the second refrigerant liquid supply path 126 for bearing lubrication.

[0098] As shown at S3, S6, and S7 in FIG. 9, when the standby refrigeration liquid pump 202 is started to supply the liquid to the bearing of the compressor 42 with the second refrigerant liquid supply path 126 for bearing lubrication, if the bearing liquid supply pressure difference ΔPbrg is greater than the minimum allowable bearing liquid supply pressure difference ΔPmin and the duration thereof is greater than the first set time Ts1, that is, ΔPbrg>ΔPmin and the duration>Ts1 are satisfied, the controller 100 determines that the running state of the standby refrigeration liquid pump 202 is good, the liquid can be normally supplied to the bearing of the compressor 42 with the second refrigerant liquid supply path 126 for bearing lubrication, and the compressor 42 continues to run. If it is not satisfied that the bearing liquid supply pressure difference ΔPbrg is greater than the minimum allowable bearing liquid supply pressure difference ΔPmin and the duration thereof is greater than the first set time Ts1, that is, ΔPbrg>ΔPmin and the duration>Ts1 are not satisfied, the controller 100 determines that the running state of the standby refrigeration liquid pump 202 is poor, and gives an alarm to hint to check the refrigerant liquid supply path for bearing lubrication.2) The Refrigeration System Gradually Runs Stably

[0099] As shown at S4 and S15 in FIG. 8 and FIG. 9, following the starting of the refrigeration system 31, the compressor 42 starts to run, and in the case where the pressure difference ΔP of the refrigeration system is greater than a sum of the minimum allowable bearing liquid supply pressure difference ΔPmin and the upward offset value Pup of the bearing liquid supply pressure difference, and the duration thereof is greater than the first set time Ts1, that is, ΔP>ΔPmin+Pup and the duration>Ts1 are satisfied, the controller 100 determines that the refrigeration system 31 satisfies a pressure difference condition of natural liquid supply, and in this case, the refrigerant liquid in the bearing liquid supply bag 13 can be transported to the bearing 3 to lubricate the bearing only by the pressure difference ΔP of the refrigeration system, the main refrigeration liquid pump 201 is turned off, and the liquid is supplied to the bearing of the compressor 42 with the first refrigerant liquid supply path 125 for bearing lubrication.

[0100] As shown at S14, S16, S18, and S19 in FIG. 9, when the refrigeration liquid pump 20 is turned off and the refrigerant liquid is supplied to the bearing of the compressor 42 with the first refrigerant liquid supply path 125 for bearing lubrication, one running state of the controller 100 is as follows.

[0101] In the case where the bearing liquid supply pressure difference ΔPbrg is greater than or equal to the minimum allowable bearing liquid supply pressure difference ΔPmin, that is, ΔPbrg<ΔPmin is not satisfied, no action is performed.

[0102] In the case where the bearing liquid supply pressure difference ΔPbrg is less than the minimum allowable bearing liquid supply pressure difference ΔPmin and the bearing liquid supply pressure difference ΔPbrg is greater than or equal to a difference between the minimum allowable bearing liquid supply pressure difference ΔPmin and the downward offset value Pdown of the bearing liquid supply pressure difference, or the bearing liquid supply pressure difference ΔPbrg is less than the minimum allowable bearing liquid supply pressure difference ΔPmin, and the bearing liquid supply pressure difference ΔPbrg is less than the difference between the minimum allowable bearing liquid supply pressure difference ΔPmin and the downstream offset value Pdown of the bearing liquid supply pressure difference, and the duration thereof is less than or equal to Ts2, that is, ΔPbrg<ΔPmin is satisfied, and ΔPbrg<ΔPmin−Pdown and the duration>Ts2 are not satisfied, the controller 100 controls the refrigeration system 31 to give an alarm to hint to check the refrigerant liquid supply path for bearing lubrication.

[0103] As shown at S18 and S20 in FIG. 9, in the case where the bearing liquid supply pressure difference ΔPbrg is less than the difference between the minimum allowable bearing liquid supply pressure difference ΔPmin and the downward offset value Pdown of the bearing liquid supply pressure difference and the duration thereof is greater than the second set time Ts2, that is, ΔPbrg<ΔPmin−Pdown and the duration>Ts2 are satisfied, the controller 100 controls the refrigeration system 31 to give an alarm and perform shutdown.

[0104] According to a set bearing liquid supply pressure difference judgment interval with a lower limit of ΔPmin−Pdown, when the bearing liquid supply pressure difference ΔPbrg is below the lower limit, it indicates that there is a risk of insufficient bearing lubrication liquid supply power in the system, and in this case, whether to issue an alarm or shutdown is determined according to the duration of this condition. When the duration of this condition is greater than Ts2, the risk of insufficient power is indicated to be maximum in this case, an amount of the refrigerant liquid supplied for lubrication of the bearing in the motor is quite small, and therefore, in order to protect the bearing in the motor of the compressor from dry friction damage, the controller 100 directly controls the refrigeration system 31 to give an alarm and perform shutdown in a control logic, and the compressor is caused to be out of this condition in a shortest time to protect the bearing.

[0105] As shown at S17, S21, and S36 in FIG. 9, when the refrigeration liquid pump 20 is turned off and the liquid is supplied to the bearing of the compressor 42 with the first refrigerant liquid supply path 125 for bearing lubrication, another running state is as follows.

[0106] In the case where the pressure difference ΔP of the refrigeration system 31 is smaller than the difference between the minimum allowable bearing liquid supply pressure difference ΔPmin and the downward offset value Pdown of the bearing liquid supply pressure difference and the duration thereof is greater than the first set time Ts1, that is, ΔP<ΔPmin−Pdown and the duration>Ts1 are satisfied, the controller 100 considers that only the pressure difference ΔP of the refrigeration system is insufficient to supply liquid to the bearing for lubrication, and starts the main refrigeration liquid pump 201. The liquid is supplied to the bearing of the compressor 42 with the second refrigerant liquid supply path 126 for bearing lubrication, and the main refrigeration liquid pump 201 pumps the refrigerant liquid from the bearing liquid supply bag 13 to supply the liquid to lubricate the bearing 3. If ΔP<ΔPmin−Pdown and the duration>Ts1 are not satisfied, no action is performed.

[0107] As shown at S22, S27, and S24 in FIG. 9, when the main refrigeration liquid pump 201 is turned on and the liquid is supplied to the bearing of the compressor 42 with the second refrigerant liquid supply path 126 for bearing lubrication, one running state of the controller 100 is as follows.

[0108] In the case where the bearing liquid supply pressure difference ΔPbrg is less than or equal to the minimum allowable bearing liquid supply pressure difference ΔPmin, or the bearing liquid supply pressure difference ΔPbrg is greater than the minimum allowable bearing liquid supply pressure difference ΔPmin, and the duration thereof is less than or equal to the first set time Ts1, that is, ΔPbrg>ΔPmin and the duration>Ts1 are not satisfied, the controller 100 determines that the running state of the main refrigeration liquid pump 201 is poor, and in this case, it switches to use the standby refrigeration liquid pump 202. If ΔPbrg>ΔPmin and the duration>Ts1 are satisfied, no action is performed.

[0109] As shown at S24, S25, S26, and S27 in FIG. 9, when the standby refrigeration liquid pump 202 is turned on and the liquid is supplied to the bearing of the compressor 42 with the second refrigerant liquid supply path 126 for bearing lubrication, if the bearing liquid supply pressure difference ΔPbrg is greater than the minimum allowable bearing liquid supply pressure difference ΔPmin and the duration thereof is greater than the first set time Ts1, that is, ΔPbrg>ΔPmin and the duration>Ts1 are satisfied, the controller 100 determines that the running state of the standby refrigeration liquid pump 202 is good, the liquid can be normally supplied to the bearing of the compressor 42 with the second refrigerant liquid supply path 126 for bearing lubrication, and no action is performed. If it is not satisfied that the bearing liquid supply pressure difference ΔPbrg is greater than the minimum allowable bearing liquid supply pressure difference ΔPmin and the duration thereof is greater than the first set time Ts1, that is, ΔPbrg>ΔPmin and the duration>Ts1 are not satisfied, the controller 100 determines that the running state of the standby refrigeration liquid pump 202 is poor, and gives an alarm to hint to check the refrigerant liquid supply path for bearing lubrication.

[0110] As shown at S8, S9, S14, and S10 in FIG. 9, when the refrigeration liquid pump 201 is turned on and the liquid is supplied to the bearing of the compressor 42 with the second refrigerant liquid supply path 126 for bearing lubrication, another running state of the controller 100 is as follows.

[0111] In the case where the bearing liquid supply pressure difference ΔPbrg is less than or equal to the minimum allowable bearing liquid supply pressure difference ΔPmin, or the bearing liquid supply pressure difference ΔPbrg is greater than the minimum allowable bearing liquid supply pressure difference ΔPmin and the duration thereof is less than or equal to the first set time Ts1, that is, ΔPbrg>ΔPmin and the duration>Ts1 are not satisfied, the controller 100 determines that the running state of the main refrigeration liquid pump 201 is poor, and in this case, it switches to use the standby refrigeration liquid pump 202. If ΔPbrg>ΔPmin and the duration>Ts1 are satisfied, the controller 100 controls the refrigeration system 31 to perform no action.

[0112] It can be understood that the controller 100 controlling the refrigeration system 31 to perform no action means controlling the refrigeration system 31 to maintain the present operation state and not to perform additional actions such as switching the refrigeration liquid pumps, issuing an alarm, or the like.

[0113] As shown at S11, S12, and S13 in FIG. 9, when the standby refrigeration liquid pump 202 is used, if the bearing liquid supply pressure difference ΔPbrg is greater than the minimum allowable bearing liquid supply pressure difference ΔPmin and the duration thereof is greater than the first set time Ts1, that is, ΔPbrg>ΔPmin and the duration>Ts1 are satisfied, the controller 100 determines that the running state of the standby refrigeration liquid pump 202 is good, the liquid can be normally supplied to the bearing of the compressor 42 with the second refrigerant liquid supply path 126 for bearing lubrication, and no action is performed. If it is not satisfied that the bearing liquid supply pressure difference ΔPbrg is larger than the minimum allowable bearing liquid supply pressure difference ΔPmin and the duration thereof is larger than the first set time Ts1, that is, ΔPbrg>ΔPmin and the duration>Ts1 are not satisfied, the controller 100 determines that the running state of the standby refrigeration liquid pump 202 is poor, and gives an alarm to hint to check the refrigerant liquid supply path for bearing lubrication.

[0114] When the main refrigeration liquid pump 201 is turned on and the liquid is supplied to the bearing of the compressor 42 with the second refrigerant liquid supply path 126 for bearing lubrication, another running state of the controller 100 is as follows.

[0115] As shown at S23, S26, S28, and S36 in FIG. 9, when the main refrigeration liquid pump 201 is turned on and the liquid is supplied to the bearing of the compressor 42 with the second refrigerant liquid supply path 126 for bearing lubrication, one running state of the controller 100 is as follows.

[0116] In the case where the bearing liquid supply pressure difference ΔPbrg is greater than or equal to the minimum allowable bearing liquid supply pressure difference ΔPmin, that is, ΔPbrg<ΔPmin is not satisfied, the controller 100 controls the refrigeration system 31 to perform no action.

[0117] In the case where the bearing liquid supply pressure difference ΔPbrg is less than the minimum allowable bearing liquid supply pressure difference ΔPmin and the bearing liquid supply pressure difference ΔPbrg is greater than or equal to a difference between the minimum allowable bearing liquid supply pressure difference ΔPmin and the downstream offset value Pdown of the bearing liquid supply pressure difference, or the bearing liquid supply pressure difference ΔPbrg is less than the minimum allowable bearing liquid supply pressure difference ΔPmin, and the bearing liquid supply pressure difference ΔPbrg is less than the difference between the minimum allowable bearing liquid supply pressure difference ΔPmin and the downward offset value Pdown of the bearing liquid supply pressure difference, and the duration thereof is less than or equal to Ts2, that is, ΔPbrg<ΔPmin is satisfied, and ΔPbrg<ΔPmin−Pdown and the duration>Ts2 are not satisfied, the controller 100 controls the refrigeration system 31 to give an alarm to hint to check the refrigerant liquid supply path for bearing lubrication. In the case where ΔPbrg<ΔPmin is not satisfied, the controller 100 controls the refrigeration system 31 to perform no action.

[0118] As shown at S28 and S29 in FIG. 9, in the case where the bearing liquid supply pressure difference ΔPbrg is less than the difference between the minimum allowable bearing liquid supply pressure difference ΔPmin and the downward offset value Pdown of the bearing liquid supply pressure difference and the duration thereof is greater than the second set time Ts2, that is, ΔPbrg<ΔPmin−Pdown and the duration>Ts2 are satisfied, the controller 100 controls the refrigeration system 31 to give an alarm and perform shutdown.

[0119] Meanwhile, at the running stage of the oil-free bearing liquid supply air-conditioning system: as shown at S33, S34, and S35 in FIG. 9, when the value Lcon collected by the first liquid level sensor 17 is greater than the minimum allowable liquid level Lcmin of the condenser 19, that is, Lcon>Lcmin is satisfied, the controller 100 controls the refrigerant system 31 to perform no action, and in this case, the liquid level in the condenser 19 is sufficient, a sufficient amount of refrigerant liquid can be supplied to the first liquid supply liquid bag 13, and an opening degree of the first electric regulating valve 37 is kept constant.

[0120] When the value Lcon collected by the first liquid level sensor 17 is less than or equal to the minimum allowable liquid level Lcmin of the condenser 19, that is, Lcon>Lcmin is not satisfied, the liquid level of the condenser 19 is low in this case, and the refrigerant liquid in the first liquid supply bag 13 cannot be supplemented in time, then the controller 100 adjusts the opening degree of the first electric regulating valve 37, and reduces the opening degree of the first electric regulating valve 37, so that an amount of the liquid supplied from the condenser 19 to the economizer 23 is reduced, so as to restore the liquid level of the condenser 19 to a higher liquid level again.

[0121] As shown at S30, S31, and S32 in FIG. 9, when the refrigeration system monitors that the subcooling degree Tsub of the refrigerant liquid under P3 and T3 is greater than the minimum allowable subcooling degree Tmin of the liquid supplied to bearing, that is, Tsub>Tmin is satisfied, the controller 100 controls the refrigeration system 31 to perform no action, ensuring that the liquid supplied for bearing lubrication is in a subcooled state, which is a pure subcooled liquid and hardly contains gas. In this case, the refrigeration system is normal and performs no action.

[0122] When the system monitors that the subcooling degree Tsub of the refrigerant liquid under P3 and T3 is less than or equal to the minimum allowable subcooling degree Tmin of the liquid supplied to bearing, that is, Tsub>Tmin is not satisfied, the liquid supplied for bearing lubrication cannot be ensured to be in the subcooled state, and in this case, the controller 100 adjusts the electronic expansion valve 36 to increase an opening degree thereof, so that the subcooling degree of the liquid supplied to the bearing is adjusted to satisfy a bearing lubrication liquid supply requirement.

[0123] The running process of the compressor is as follows: the refrigerant liquid in the evaporator 29 undergoes an evaporative phase change, the refrigerant gas generated by the phase change is delivered along the second exhaust path 102 to a path 101, and at a gas suction port of the compressor 42, the refrigerant gas is continuously sucked and compressed by the first-stage impeller 1 in the compressor, and then compressed by the second-stage impeller 2. After the compression is completed, it is exhausted from the exhaust port of the second-stage impeller 2, and enters the condenser 19 along the first exhaust path 119 to undergo a condensation phase change. The refrigerant liquid generated by the condensation phase change enters the economizer 23 after passing through the first electric regulating valve 37 and the first throttling orifice plate 21 along the refrigerant supply path 106. The refrigerant gas formed by flash vaporization of the refrigerant liquid in the economizer 23 enters the compressor along the gas supplementing path 109 for gas supplementing, and the residual liquid in the economizer 23 enters the evaporator 29 after passing through the third electric regulating valve 24 and the second throttling orifice plate 25 along the liquid return path 107, so as to complete one circulation process. In this process, the first electric regulating valve 37 can be correspondingly adjusted according to the liquid level of the condenser monitored by the liquid level sensor 17, and when the liquid level in the condenser 19 is excessively low, the opening degree of the first electric regulating valve 37 can be reduced, so that the mount of the liquid supplied from the condenser 19 to the economizer 23 is reduced, and therefore, the liquid level in the condenser 19 is restored to an allowable value again.

[0124] In an initial stage of operation of the refrigeration system 31, a pressure difference between the condenser 19 and the evaporator 29 in the refrigeration system 31 is small, and in this case, the controller 100 controls the main refrigeration liquid pump 201 to be still in the turned on state. The main refrigeration liquid pump 201 pumps the refrigerant liquid continuously from the first liquid supply bag 13 with more refrigerant liquid, the refrigerant liquid passes through the main refrigeration liquid pump 201, the pressure regulating valve 10, the second filter 9, and the subcooler 35 along the first section path 120 of the second refrigerant liquid supply path for bearing lubrication to the last section path 121 of the second refrigerant liquid supply path for bearing lubrication, and then is divided into two streams of the bearing lubrication liquid supply branch path 111 and the bearing lubrication liquid supply branch path 112 to lubricate the left and right bearings 3 in the compressor. The refrigerant, after lubricating the bearings, returns to the evaporator 29 through the fourth pressure sensor 30 and the second solenoid valve 12 along the bearing lubrication liquid return path 118. The pressure regulating valve 10 is configured to regulate the pressure difference between the liquid pumped by the main refrigeration liquid pump 201 and the liquid supplied to the bearing to be not less than the set minimum bearing liquid supply pressure difference, thus ensuring that a pressure difference fluctuation caused by starting or stopping of the forced liquid supply by the main refrigeration liquid pump 201 is not too large, and reducing an impact influence on the running of the refrigeration system.3) The Refrigeration System is Normally Shut Down

[0125] As shown in FIG. 8 and FIG. 10, at a certain time before the refrigeration system 31 is stopped, the controller 100 starts the main refrigeration liquid pump 201, and the main refrigeration liquid pump 201 forcibly supplies liquid, and in this case, the pressure regulating valve 10 is regulated to regulate the pressure difference between the liquid pumped by the main refrigeration liquid pump 201 and the liquid supplied to the bearing to be not less than the set minimum bearing liquid supply pressure difference, thus ensuring that the pressure difference fluctuation caused by starting or stopping of the forced liquid supply by the main refrigeration liquid pump 201 is not too large, and reducing the impact influence on the running of the refrigeration system. This state can ensure that the bearing 3 in the compressor is continuously lubricated with sufficient refrigerant liquid.

[0126] As shown at M1, M2, M3, M7, M8, and M9 in FIG. 10, after the refrigeration system 31 is stopped, a gas suction amount of the compressor 42 is reduced, but a large pressure difference ΔP of the refrigeration system still exists in the whole refrigeration system 31. If the controller 100 detects that the main refrigeration liquid pump 201 is in the running state, the running state of the refrigeration liquid pump 20 is maintained, the main refrigeration liquid pump 201 forcibly supplies the liquid to the bearing 3 for lubrication from the first liquid supply bag 13, and the main refrigeration liquid pump 201 is turned off after the compressor is powered off for the third set time Ts3. The first solenoid valve 33 is opened while the main refrigeration liquid pump 201 is stopped, so as to cause the communication pipe path 103 at the bottoms of the condenser 19 and the evaporator 29 to be connected, so that it can be ensured that a refrigerant level in the condenser 19 and a refrigerant level in the evaporator are uniformly distributed after the refrigeration system is stopped, and the bearing liquid supply bag 13 below the condenser 19 is also full of the refrigerant liquid to accumulate sufficient refrigerant liquid for bearing lubrication in the next startup.

[0127] As shown at M9, M10, M11, and M12 in FIG. 10, when the controller 100 detects that the main refrigeration liquid pump 201 in the refrigeration system 31 is originally in a stopped state, it turns on the main refrigeration liquid pump 201. After the main refrigeration liquid pump 201 runs, in the case where the bearing liquid supply pressure difference ΔPbrg is less than or equal to the minimum allowable bearing liquid supply pressure difference ΔPmin, or the bearing liquid supply pressure difference ΔPbrg is greater than the minimum allowable bearing liquid supply pressure difference ΔPmin, and the duration thereof is less than or equal to the first set time Ts1, that is, ΔPbrg>ΔPmin and the duration>Ts1 are not satisfied, the controller 100 determines that the running state of the main refrigeration liquid pump 201 is poor, and in this case, it switches to use the standby refrigeration liquid pump 202. If ΔPbrg>ΔPmin and the duration>Ts1 are satisfied, no action is performed.

[0128] As shown at M11, M13, and M14 in FIG. 10, if the bearing liquid supply pressure difference ΔPbrg is greater than the minimum allowable bearing liquid supply pressure difference ΔPmin and the duration thereof is greater than the first set time Ts1, that is, ΔPbrg>ΔPmin and the duration>Ts1 are satisfied, the controller 100 determines that the running state of the standby refrigeration liquid pump 202 is good, and the liquid can be normally supplied to the bearing of the compressor 42 with the second refrigerant liquid supply path 126 for bearing lubrication, then no action is performed. If it is not satisfied that the bearing liquid supply pressure difference ΔPbrg is greater than the minimum allowable bearing liquid supply pressure difference ΔPmin and the duration thereof is greater than the first set time Ts1, that is, ΔPbrg>ΔPmin and the duration>Ts1 are not satisfied, the controller 100 determines that the running state of the standby refrigeration liquid pump 202 is poor, and gives an alarm to hint to check the refrigerant liquid supply path for bearing lubrication.

[0129] Eventually, the refrigeration system 31 is safely shut down.4) The Refrigeration System is Abnormally Shut Down (for Example, Abnormal Shutdown Due to Power-Off):

[0130] As shown in FIG. 8 and FIG. 10, when the refrigeration system 31 encounters sudden power-off and shutdown, the main refrigeration liquid pump 201 is unavailable at this time, the exhaust check valve 16 prevents the high-pressure gas in the condenser 19 from flowing back into the compressor, so the refrigeration system pressure difference ΔP between the condenser 19 and the evaporator 29 is still maintained at a relatively large value. In this case, emergency bearing liquid supply is carried out by the refrigeration system pressure difference still existing in the system, and the refrigerant liquid flows from the first liquid supply bag 13 below the condenser 19 to the last section path 121 of the first refrigerant liquid supply path for bearing lubrication along the first section path 120 of the first refrigerant liquid supply path for bearing lubrication through the first filter, the first check valve 11, the pressure regulating valve 10, the second filter 9, and the subcooler 35, and then is divided into two streams in the bearing lubrication liquid supply branch path 111 and the bearing lubrication liquid supply branch path 112 to lubricate the left and right bearings 3 in the compressor 42.

[0131] As shown at M4, M6, and M8 in FIG. 10, due to the power-off shutdown, a system cycle is stopped, the controller 100 closes the second solenoid valve 12 on the bearing liquid return or gas return path 118, and the high pressure of the condenser 19 and the low pressure of the evaporator 29 are gradually balanced through a pipeline connection. That is, the process of supplying the liquid to the bearing 3 only by the pressure difference ΔP of the refrigeration system can last for about 15-20 s, but the rotor of the motor in the permanent magnet motor can be completely stopped within 5-10 s, so that the mode of lubricating the bearing by using such emergency liquid supply is still reliable and effective in the case of using the permanent magnet motor.

[0132] As shown at M4, M5, and M8 in FIG. 10, if the refrigeration system pressure difference ΔP between the condenser 19 and the evaporator 29 is small in the original non-stop running state, that is, the refrigeration system pressure difference ΔP is less than the bearing liquid supply pressure difference ΔPbrg, power-off shutdown occurs suddenly, and the liquid cannot be supplied to the bearing only by the refrigeration system pressure difference ΔP. The controller 100 controls the refrigeration liquid pump in the refrigeration system 31 to be powered preferably by the UPS.

[0133] The main refrigeration liquid pump 201 can be started to run and therefore can continuously pump the liquid from the first liquid supply bag 13 to the bearing 3 in the compressor. Since in the process of the gradual balance of the high and low pressures, the refrigerant liquid gradually accumulated in the evaporator 29 can also continuously supplement the refrigerant liquid to the first liquid supply bag 13 through the communication pipeline 103, the main refrigeration liquid pump 201 can always pump enough liquid to lubricate the bearing 3, and this process continues until the rotor is completely stopped.

[0134] Eventually, the refrigeration system 31 stops running.

[0135] In the shutdown process, the second solenoid valve 12 switches from an original normally open state to a closed state, so that the bearing lubrication liquid return or gas return path 118 is closed and cut off, thereby ensuring that a certain amount of refrigerant liquid can still be stored in a bearing cavity of the bearing 3 in the compressor within a certain time, and improving safety and reliability of the running of the bearing after shutdown.

[0136] In some embodiments, as shown at S30, S31, S32, S33, S34, and S35 in FIG. 9 and FIG. 10, the controller 100 controls the refrigeration system 31 to detect state parameters of the refrigerant liquid for bearing liquid supply lubrication at all times during all running stages of the refrigeration system.

[0137] When the value Lcon collected by the first liquid level sensor 17 is greater than the minimum allowable liquid level Lcmin of the condenser 19, that is, Lcon>Lcmin is satisfied, the controller 100 controls the refrigerant system 31 to perform no action, and in this case, the liquid level in the condenser 19 is sufficient, a sufficient amount of refrigerant liquid can be supplied to the first liquid supply bag 13, and an opening degree of the first electric regulating valve 37 is kept constant.

[0138] When the value Lcon collected by the first liquid level sensor 17 is less than or equal to the minimum allowable liquid level Lcmin of the condenser 19, that is, Lcon>Lcmin is not satisfied, the liquid level of the condenser 19 is low in this case, and the refrigerant liquid in the first liquid supply bag 13 cannot be supplemented in time, the controller 100 adjusts the opening degree of the first electric regulating valve 37, and reduces the opening degree of the first electric regulating valve 37, so that an amount of the liquid supplied from the condenser 19 to the economizer 23 is reduced, so as to restore the liquid level of the condenser 19 to a higher liquid level again.

[0139] When the refrigeration system monitors that the subcooling degree Tsub of the refrigerant liquid under P3 and T3 is greater than the minimum allowable subcooling degree Tmin of the liquid supplied to bearing, that is, Tsub>Tmin is satisfied, the controller 100 controls the refrigeration system 31 to perform no action, ensuring that the liquid supplied for bearing lubrication is in a subcooled state, which is a pure subcooled liquid and hardly contains gas. In this case, the refrigeration system 31 is normal and performs no action.

[0140] When the system monitors that the subcooling degree Tsub of the refrigerant liquid under P3 and T3 is less than or equal to the minimum allowable subcooling degree Tmin of the liquid supplied to bearing, that is, Tsub>Tmin is not satisfied, the liquid supplied for bearing lubrication cannot be ensured to be in the subcooled state, and in this case, the controller 100 adjusts the electronic expansion valve 36, so that the subcooling degree of the liquid supplied to the bearing is adjusted to satisfy a bearing lubrication liquid supply requirement.

[0141] In the present application, two different refrigerant liquid supply paths for bearing lubrication are applied to realize stable and reliable full-stage bearing liquid supply, the corresponding pipeline connection and a power apparatus (pump) are provided in the system, different liquid taking sources are selected in the refrigeration system according to the judged running state of the refrigeration system, different refrigerant liquid supply paths are selected for supplying refrigeration liquid for bearing lubrication, and the adopted liquid supply path switching mode ensures that the bearing in the compressor can obtain sufficient refrigerant liquid for lubrication at each stage, thus guaranteeing system running safety.

[0142] The foregoing description, for ease of explanation, has been given with reference to specific embodiments. However, the foregoing discussion in some embodiments is not intended to be exhaustive or to limit the embodiments to the precise forms disclosed above. Many modifications and variations are possible in light of the above teaching. The above embodiments are chosen and described in order to better explain the principles and the practical application, thereby enabling those skilled in the art to better utilize the embodiments and various modified embodiments considered for particular use.

Claims

1. An oil-free bearing liquid supply air-conditioning system, comprising:a compressor comprising a bearing;a condenser;an evaporator;a first refrigerant liquid supply path for bearing lubrication extending from the condenser to the compressor;a second refrigerant liquid supply path for bearing lubrication extending from the condenser to the compressor, wherein at least two refrigeration liquid pumps are arranged in the second refrigerant liquid supply path for bearing lubrication, the at least two refrigeration liquid pumps are arranged in parallel, and the at least two refrigeration liquid pumps comprise a main refrigeration liquid pump and at least one standby refrigeration liquid pump;a communication pipeline connecting the condenser and the evaporator, the communication pipeline comprising a first solenoid valve, the first solenoid valve being configured to control connecting and disconnecting of the communication pipeline;a controller configured to:before the refrigeration system is started, open the first solenoid valve;in a starting stage, turn on the main refrigeration liquid pump and close the first solenoid valve;in a stable running stage, in a case where a pressure difference of the refrigeration system is greater than a sum of a minimum allowable bearing liquid supply pressure difference and an upward offset value of a bearing liquid supply pressure difference, and a duration thereof is greater than a first set time, turn off the main refrigeration liquid pump; supply liquid to a bearing of the compressor with the first refrigerant liquid supply path for bearing lubrication;in the stable running stage, in a case where the pressure difference of the refrigeration system is less than or equal to the sum of the minimum allowable bearing liquid supply pressure difference and the upward offset value of the bearing liquid supply pressure difference, or the pressure difference of the refrigeration system is greater than the sum of the minimum allowable bearing liquid supply pressure difference and the upward offset value of the bearing liquid supply pressure difference, and a duration thereof is less than or equal to the first set time, maintain the main refrigeration liquid pump turned on, and supply liquid to the bearing of the compressor with the second refrigerant liquid supply path for bearing lubrication.

2. The oil-free bearing liquid supply air-conditioning system according to claim 1,wherein the first refrigerant liquid supply path for bearing lubrication comprises a first section path, a front section path, a rear section path, and a last section path which are sequentially communicated;the second refrigerant liquid supply path for bearing lubrication comprises a first section path, a front section path, a rear section path, and a last section path which are sequentially communicated;the front section path of the first refrigerant liquid supply path for bearing lubrication and the front section path of the second refrigerant liquid supply path for bearing lubrication are arranged in parallel, the main refrigeration fluid pump and the at least one standby refrigeration fluid pump are arranged in parallel in the front section path of the second refrigerant liquid supply path for bearing lubrication, the rear section path of the first refrigerant liquid supply path for bearing lubrication and the rear section path of the second refrigerant liquid supply path for bearing lubrication are the same path, the first section path of the first refrigerant liquid supply path for bearing lubrication and the first section path of the second refrigerant liquid supply path for bearing lubrication are the same path and are communicated with the condenser, and the last section path of the first refrigerant liquid supply path for bearing lubrication and the last section path of the second refrigerant liquid supply path for bearing lubrication are the same path and are communicated with the compressor.

3. The oil-free bearing liquid supply air-conditioning system according to claim 2, wherein the controller is further configured to:in the stable running stage, when the main refrigeration liquid pump is stopped and the liquid is supplied to the bearing of the compressor with the first refrigerant liquid supply path for bearing lubrication, in a case where the bearing liquid supply pressure difference is smaller than the minimum allowable bearing liquid supply pressure difference, and the bearing liquid supply pressure difference is greater than or equal to a difference between the minimum allowable bearing liquid supply pressure difference and a downstream offset value of the bearing liquid supply pressure difference, or the bearing liquid supply pressure difference is less than the difference between the minimum allowable bearing liquid supply pressure difference and the downstream offset value of the bearing liquid supply pressure difference and a duration thereof is less than a second set time, control the refrigeration system to give an alarm to hint to check the refrigerant liquid supply path for bearing lubrication.

4. The oil-free bearing liquid supply air-conditioning system according to claim 2, wherein the controller is further configured to:in the stable running stage, when the main refrigeration liquid pump is stopped and the liquid is supplied to the bearing of the compressor with the first refrigerant liquid supply path for bearing lubrication, in a case where the bearing liquid supply pressure difference is less than the difference between the minimum allowable bearing liquid supply pressure difference and the downward offset value of the bearing liquid supply pressure difference and a duration thereof is greater than the second set time, control the refrigeration system to give an alarm and be shut down.

5. The oil-free bearing liquid supply air-conditioning system according to claim 1,wherein the pressure difference of the refrigeration system is a difference between a pressure value of the condenser and a pressure value of the evaporator, and the minimum bearing liquid supply pressure difference is a difference between a preset bearing liquid supply pressure value and a minimum allowable bearing lubrication liquid return or gas return pressure value.

6. The oil-free bearing liquid supply air-conditioning system according to claim 2, further comprising:a bearing lubrication liquid return or gas return path from the compressor to the evaporator;a first pressure sensor connected to the condenser and configured to collect a pressure value of the condenser;a second pressure sensor connected to the evaporator and configured to collect a pressure value of the evaporator;a third pressure sensor connected to the last section path of the first refrigerant liquid supply path for bearing lubrication and configured to collect a bearing liquid supply pressure value; anda fourth pressure sensor connected to the bearing lubrication liquid return or gas return path and configured to collect a bearing lubrication liquid return or gas return pressure value.

7. The oil-free bearing liquid supply air-conditioning system according to claim 1, wherein the controller is further configured to:in the stable running stage, in a case where the pressure difference of the refrigeration system is less than the difference of the minimum allowable bearing liquid supply pressure difference and the downward offset value of the bearing liquid supply pressure difference, and a duration thereof is greater than the first set time, turn on the main refrigeration liquid pump, and supply the liquid to the bearing of the compressor with the second refrigerant liquid supply path for bearing lubrication;when the main refrigeration liquid pump is turned on and the liquid is supplied to the bearing of the compressor with the second refrigerant liquid supply path for bearing lubrication, in a case where the bearing liquid supply pressure difference is less than the minimum allowable bearing liquid supply pressure difference, and the bearing liquid supply pressure difference is greater than or equal to the difference between the minimum allowable bearing liquid supply pressure difference and the downward offset value of the bearing liquid supply pressure difference, or the bearing liquid supply pressure difference is less than the difference between the minimum allowable bearing liquid supply pressure difference and the downward offset value of the bearing liquid supply pressure difference and a duration thereof is less than the second set time, control the refrigeration system to give an alarm to hint to check the refrigerant liquid supply path for bearing lubrication;in a case where the bearing liquid supply pressure difference is less than the difference between the minimum allowable bearing liquid supply pressure difference and the downward offset value of the bearing liquid supply pressure difference and a duration thereof is greater than the second set time, control the refrigeration system to give an alarm and be shut down,wherein the bearing liquid supply pressure difference is a difference between a bearing liquid supply pressure value and a bearing lubrication liquid return or gas return pressure value which are measured in real time.

8. The oil-free bearing liquid supply air-conditioning system according to claim 1, further comprising:a second solenoid valve arranged on a bearing lubrication liquid return or gas return path from the compressor to the evaporator;the controller is further configured to:when the refrigeration system is started, turn on the main refrigeration liquid pump, and close the first solenoid valve; in a case where the bearing liquid supply pressure difference is greater than the minimum allowable bearing liquid supply pressure difference and a duration thereof is greater than the first set time, run the compressor, and supply the liquid to the bearing of the compressor with the second refrigerant liquid supply path for bearing lubrication;a shutdown stage comprises a normal power-off shutdown stage and an abnormal power-off shutdown stage;the controller is further configured to:in the normal power-off shutdown stage:in a case where the main refrigeration liquid pump is in a turned on state, after the compressor is powered off for a third set time, stop the main refrigeration liquid pump, and open the first solenoid valve; andin a case where the main refrigeration liquid pump is in the stopped state, forcibly start the main refrigeration liquid pump; and after the compressor is powered off for the third set time, stop the main refrigeration liquid pump, and open the first solenoid valve; andin the abnormal power-off shutdown stage:close the second solenoid valve.

9. The oil-free bearing liquid supply air-conditioning system according to claim 1, wherein the controller is further configured to:when the main refrigeration liquid pump is turned on and the liquid is supplied to the bearing of the compressor with the second refrigerant liquid supply path for bearing lubrication, in a case where the bearing liquid supply pressure difference is less than or equal to the minimum allowable bearing liquid supply pressure difference, or the bearing liquid supply pressure difference is greater than the minimum allowable bearing liquid supply pressure difference, and a duration thereof is less than or equal to the first set time, turn on the standby refrigeration liquid pump; andwhen the standby refrigeration liquid pump is turned on and the liquid is supplied to the bearing of the compressor with the second refrigerant liquid supply path for bearing lubrication, in a case where the bearing liquid supply pressure difference is less than or equal to the minimum allowable bearing liquid supply pressure difference, or the bearing liquid supply pressure difference is greater than the minimum allowable bearing liquid supply pressure difference, and a duration thereof is less than or equal to the first set time, control the refrigeration system to give an alarm to hint to check the refrigerant liquid supply path for bearing lubrication.

10. The oil-free bearing liquid supply air-conditioning system according to claim 1, further comprising:an economizer;a refrigerant supply path extending from the condenser to the economizer, the refrigerant supply path comprising a first electric regulating valve; anda first liquid level sensor, the first liquid level sensor being configured to monitor a liquid level of the condenser;the controller is further configured to:when a value collected by the first liquid level sensor is greater than a minimum allowable liquid level of the condenser, keep an opening degree of the first electric regulating valve; andwhen the value collected by the first liquid level sensor is less than or equal to the minimum allowable liquid level of the condenser, adjust the opening degree of the first electric regulating valve to reduce the opening degree of the first electric regulating valve.

11. The oil-free bearing liquid supply air-conditioning system according to claim 1, further comprising:a subcooler, the subcooler being communicated with the rear section path of the first refrigerant liquid supply path for bearing lubrication and the last section path of the first refrigerant liquid supply path for bearing lubrication;a heat exchange path from the condenser to the subcooler; the heat exchange path comprising an electronic expansion valve; anda first temperature sensor, the first temperature sensor being configured to monitor a temperature of the last section path of the first refrigerant liquid supply path for bearing lubrication;the controller is further configured to:in a case where a subcooling degree of the refrigerant liquid is greater than a minimum allowable subcooling degree of the liquid supplied to bearing, control the refrigeration system to perform no action; andin a case where the subcooling degree of the refrigerant liquid is less than or equal to the minimum allowable subcooling degree of the liquid supplied to bearing, adjust the electronic expansion valve to increase an opening degree of the electronic expansion valve;wherein the subcooling degree of the refrigerant liquid is calculated according to a measured bearing liquid supply pressure value and a bearing liquid supply temperature, and the minimum allowable subcooling degree of the liquid supplied to bearing is a preset value.

12. The oil-free bearing liquid supply air-conditioning system according to claim 1, wherein the minimum allowable bearing liquid supply pressure difference ranges from 0.05 MPa to 0.35 MPa;the upward offset value of the bearing liquid supply pressure difference ranges from 0 MPa to 0.35 MPa;the first set time is 1 min.

13. The oil-free bearing liquid supply air-conditioning system according to claim 3, wherein the downward offset value of the bearing liquid supply pressure difference ranges from 0 MPa to 0.35 Mpa, and the second set time is 30 seconds.

14. The oil-free bearing liquid supply air-conditioning system according to claim 8, wherein the third set time is 3 minutes.

15. A control method for an oil-free bearing liquid supply air-conditioning system applied to an oil-free bearing liquid supply air-conditioning system, the oil-free bearing liquid supply air-conditioning system comprising:a compressor comprising a bearing;a condenser;an evaporator;a first refrigerant liquid supply path for bearing lubrication extending from the condenser to the compressor,a second refrigerant liquid supply path for bearing lubrication extending from the condenser to the compressor, wherein at least two refrigeration liquid pumps are arranged in the second refrigerant liquid supply path for bearing lubrication, the at least two refrigeration liquid pumps are arranged in parallel, and the at least two refrigeration liquid pumps comprise a main refrigeration liquid pump and at least one standby refrigeration liquid pump;a communication pipeline connecting between the condenser and the evaporator, the communication pipeline comprising a first solenoid valve, the first solenoid valve being configured to control connecting and disconnecting of the communication pipeline; wherein the control method comprises:before the refrigeration system is started, opening the first solenoid valve;in a starting stage, turning on the main refrigeration liquid pump and closing the first solenoid valve;in a stable running stage, in a case where a pressure difference of the refrigeration system is greater than a sum of a minimum allowable bearing liquid supply pressure difference and an upstream offset value of a bearing liquid supply pressure difference, and a duration thereof is greater than a first set time, turning off the main refrigeration liquid pump; supplying liquid to a bearing of the compressor with the first refrigerant liquid supply path for bearing lubrication;in the stable running stage, in a case where the pressure difference of the refrigeration system is less than or equal to the sum of the minimum allowable bearing liquid supply pressure difference and the upward offset value of the bearing liquid supply pressure difference, or the pressure difference of the refrigeration system is greater than the sum of the minimum allowable bearing liquid supply pressure difference and the upward offset value of the bearing liquid supply pressure difference, and a duration thereof is less than or equal to the first set time, maintaining the main refrigeration liquid pump turned on; and supplying liquid to the bearing of the compressor with the second refrigerant liquid supply path for bearing lubrication.

16. The control method for an oil-free bearing liquid supply air-conditioning system according to claim 15, further comprising:in the stable running stage, when the main refrigeration liquid pump is stopped and the liquid is supplied to the bearing of the compressor with the first refrigerant liquid supply path for bearing lubrication, in a case where the bearing liquid supply pressure difference is smaller than the minimum allowable bearing liquid supply pressure difference, and the bearing liquid supply pressure difference is greater than or equal to a difference between the minimum allowable bearing liquid supply pressure difference and a downward offset value of the bearing liquid supply pressure difference, or the bearing liquid supply pressure difference is smaller than the difference between the minimum allowable bearing liquid supply pressure difference and the downstream offset value of the bearing liquid supply pressure difference and a duration thereof is smaller than a second set time, controlling the refrigeration system to give an alarm to hint to check the refrigerant liquid supply path for bearing lubrication.

17. The control method for an oil-free bearing liquid supply air-conditioning system according to claim 15, further comprising:in the stable running stage, when the main refrigeration liquid pump is stopped and the liquid is supplied to the bearing of the compressor with the first refrigerant liquid supply path for bearing lubrication, in a case where the bearing liquid supply pressure difference is less than the difference between the minimum allowable bearing liquid supply pressure difference and the downward offset value of the bearing liquid supply pressure difference and a duration thereof is larger than the second set time, controlling the refrigeration system to give an alarm and be shut down.

18. The control method for an oil-free bearing liquid supply air-conditioning system according to claim 15,wherein the pressure difference of the refrigeration system is a difference between a pressure value of the condenser and a pressure value of the evaporator, and the minimum bearing liquid supply pressure difference is a difference between a preset bearing liquid supply pressure value and a minimum allowable bearing lubrication liquid return or gas return pressure value.

19. The control method for an oil-free bearing liquid supply air-conditioning system according to claim 15, wherein the oil-free bearing liquid supply air-conditioning system comprises a second solenoid valve arranged on a bearing lubrication liquid return or gas return path from the compressor to the evaporator,wherein the method further comprises:when the refrigeration system is started, turning on the main refrigeration liquid pump, and closing the first solenoid valve; in a case where the bearing liquid supply pressure difference is greater than the minimum allowable bearing liquid supply pressure difference and a duration thereof is greater than the first set time, running the compressor, and supplying the liquid to the bearing of the compressor with the second refrigerant liquid supply path for bearing lubrication;wherein a shutdown stage comprises a normal power-off shutdown stage and an abnormal power-off shutdown stage, and the control method further comprises:in the normal power-off shutdown stage:in a case where the main refrigeration liquid pump is in a turned on state, after the compressor is powered off for a third set time, stopping the main refrigeration liquid pump, and opening the first solenoid valve; andin a case where the main refrigeration liquid pump is in the stopped state, forcibly starting the main refrigeration liquid pump; and after the compressor is powered off for the third set time, stopping the main refrigeration liquid pump, and open the first solenoid valve; andin the abnormal power-off shutdown stage:closing the second solenoid valve.

20. The control method for an oil-free bearing liquid supply air-conditioning system according to claim 15, further comprising:when the main refrigeration liquid pump is turned on and the liquid is supplied to the bearing of the compressor with the second refrigeration liquid supply path for bearing lubrication, in a case where the bearing liquid supply pressure difference is less than or equal to the minimum allowable bearing liquid supply pressure difference, or the bearing liquid supply pressure difference is greater than the minimum allowable bearing liquid supply pressure difference, and a duration thereof is less than or equal to the first set time, turning on the standby refrigeration liquid pump; andwhen the standby refrigeration liquid pump is turned on and the liquid is supplied to the bearing of the compressor with the second refrigerant liquid supply path for bearing lubrication, in a case where the bearing liquid supply pressure difference is less than or equal to the minimum allowable bearing liquid supply pressure difference, or the bearing liquid supply pressure difference is greater than the minimum allowable bearing liquid supply pressure difference, and a duration thereof is less than or equal to the first set time, controlling the refrigeration system to give an alarm to hint to check the refrigerant liquid supply path for bearing lubrication.

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