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

Abstract

An oilless bearing liquid supply air conditioning system (1000) and a control method thereof, the system (1000) comprising: a box system (200), the box system (200) comprising: a compressor (42), a condenser (19), an evaporator (29), an economizer (23) and a refrigeration liquid pump (20); a refrigeration system (31), the refrigeration system (31) comprising: a first bearing lubrication liquid supply path (125) from the condenser (19) to the compressor (42); a second bearing lubrication liquid supply path (126) from the condenser (19) to the compressor (42); the second bearing lubrication liquid supply path (126) is provided with at least two refrigeration liquid pumps (20), and the at least two refrigeration liquid pumps (20) are arranged in parallel; the at least two refrigeration liquid pumps (20) comprise a main refrigeration liquid pump (201) and at least one standby refrigeration liquid pump (202).

Description

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

[0001] This application claims priority to Chinese patent application No. 202222917498.0 filed on November 2, 2022, and priority to Chinese patent application No. 202211364763.5 filed on November 2, 2022, the entire contents of which are incorporated by reference into this application. Technical Field

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

[0003] At present, compressors are the main type of air conditioners, and oil lubrication of bearings is the dominant method in centrifugal chillers. However, due to the presence of lubricating oil, the oil lubrication system and oil separation system for oil supply and return must be considered during the design of chillers, which increases the complexity of design, manufacturing, maintenance and control, and greatly increases the initial cost and operation and maintenance costs. Lubricating oil leakage will also cause environmental pollution. At the same time, the lubricating oil enters the evaporator and condenser with the refrigerant, affecting the heat exchange effect and system energy efficiency, and will cause unit performance degradation after long-term operation.

[0004] Summary of the Invention

[0005] In a first aspect, an oil bearing liquid supply air conditioning system is provided, comprising: a box system, the box system comprising: a compressor, a condenser, an evaporator, an economizer and a refrigeration liquid pump; a refrigeration system, the refrigeration system comprising: a first bearing lubrication liquid supply path from the condenser to the compressor; a second bearing lubrication liquid supply path from the condenser to the compressor; the second bearing lubrication liquid supply path is provided with at least two refrigeration liquid pumps, the at least two refrigeration liquid pumps are arranged in parallel; the at least two refrigeration liquid pumps include a main refrigeration liquid pump and at least one standby refrigeration liquid pump; a controller is configured to: in the startup phase, turn on the main refrigeration liquid pump; in the stable operation phase, if When the pressure difference of the refrigeration system is greater than the sum of the minimum allowable pressure difference of the bearing supply and the upward bias value of the bearing supply pressure difference, and the duration is greater than the first set time, the main refrigeration liquid pump is turned off; the bearings of the compressor are supplied with liquid through the first bearing lubrication supply path; in the stable operation stage, if the pressure difference of the refrigeration system is less than or equal to the sum of the minimum pressure difference of the bearing supply and the upward bias value of the bearing supply pressure difference, or the pressure difference of the refrigeration system is greater than the sum of the minimum allowable pressure difference of the bearing supply and the upward bias value of the bearing supply pressure difference, and the duration is less than or equal to the first set time, the main refrigeration liquid pump is maintained on; the bearings of the compressor are supplied with liquid through the second bearing lubrication supply path.

[0006] In the second aspect, a control method for an oil bearing liquid supply air-conditioning system is provided, which is applied to an air-conditioning system, wherein the air-conditioning system includes: a box system, wherein the box system includes: a compressor, a condenser, an evaporator, an economizer and a refrigeration liquid pump; a refrigeration system, wherein the refrigeration system includes: a first bearing lubrication liquid supply path from the condenser to the compressor; a second bearing lubrication liquid supply path from the condenser to the compressor; the second bearing lubrication liquid supply path is provided with at least two refrigeration liquid pumps, and the at least two refrigeration liquid pumps are arranged in parallel; the at least two refrigeration liquid pumps include a main refrigeration liquid pump and at least one standby refrigeration liquid pump; the control method includes: in the startup phase, turning on the main refrigeration liquid pump; in the stabilization phase, In the fixed operation stage, if the pressure difference of the refrigeration system is greater than the sum of the minimum allowable pressure difference of the bearing supply and the upward bias value of the bearing supply pressure difference, and the duration is greater than the first set time, the main refrigeration liquid pump is turned off; the bearings of the compressor are supplied with liquid through the first bearing lubrication supply path; in the stable operation stage, if the pressure difference of the refrigeration system is less than or equal to the sum of the minimum pressure difference of the bearing supply and the upward bias value of the bearing supply pressure difference, or the pressure difference of the refrigeration system is greater than the sum of the minimum allowable pressure difference of the bearing supply and the upward bias value of the bearing supply pressure difference, and the duration is less than or equal to the first set time, the main refrigeration liquid pump is maintained on; the bearings of the compressor are supplied with liquid through the second bearing lubrication supply path. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG1 is a system block diagram of an oil-free bearing liquid supply air conditioning system provided by some embodiments of the present application;

[0008] FIG2 is a block diagram of a compressor system provided by some embodiments of the present application;

[0009] FIG3 is a structural diagram of a refrigeration system provided in some embodiments of the present application;

[0010] FIG4 is a partial structural diagram of a liquid supply source provided in some embodiments of the present application;

[0011] FIG5 is a partial structural diagram of another liquid supply source provided in some embodiments of the present application;

[0012] FIG6 is a partial structural diagram of a refrigeration system provided in some embodiments of the present application;

[0013] FIG7 is a partial path structure diagram of a refrigeration system provided by some embodiments of the present application;

[0014] FIG8 is an overall structural diagram of a refrigeration system provided in some embodiments of the present application;

[0015] FIG9 is a flowchart of a stable startup of a refrigeration system provided by some embodiments of the present application;

[0016] FIG10 is a flowchart of a refrigeration system shutdown and power-off process provided by some embodiments of the present application. DETAILED DESCRIPTION

[0017] The following will be combined with the accompanying drawings to clearly and completely describe some embodiments of the present disclosure. Obviously, the embodiments described are only some embodiments of the present disclosure, rather than all embodiments. Based on the embodiments provided by the present disclosure, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of the present disclosure.

[0018] Unless the context requires otherwise, throughout the specification and claims, the term "comprise" and its other forms, such as the third person singular form "comprises" and the present participle form "comprising", are to be interpreted as open and inclusive, that is, "including, but not limited to". In the description of the specification, the terms "one embodiment", "some embodiments", "exemplary embodiments", "example", "specific example" or "some examples" are intended to indicate that the particular features, structures, materials or characteristics associated with the embodiment or example are included in at least one embodiment or example of the present disclosure. The schematic representation of the above terms does not necessarily refer to the same embodiment or example. In addition, the particular features, structures, materials or characteristics may be included in any one or more embodiments or examples in any appropriate manner.

[0019] In the following, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present disclosure, unless otherwise specified, "plurality" means two or more.

[0020] When describing some embodiments, the expressions "coupled" and "connected" and their derivatives may be used. The term "connected" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. The term "coupled" indicates, for example, that two or more components are in direct physical or electrical contact. The term "coupled" or "communicatively coupled" may also refer to two or more components that are not in direct contact with each other, but still cooperate or interact with each other. The embodiments disclosed herein are not necessarily limited to the contents of this document.

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

[0022] The use of "adapted to" or "configured to" herein is intended to be open and inclusive language that does not exclude devices adapted or configured to perform additional tasks or steps.

[0023] Additionally, the use of “based on” is meant to be open and inclusive, as a process, step, calculation, or other action “based on” one or more stated conditions or values ​​may, in practice, be based on additional conditions or values ​​beyond those stated.

[0024] At present, oil lubrication of bearings is the dominant method in centrifugal chillers. However, due to the presence of lubricating oil, the oil lubrication system and oil separation system for oil supply and return must be considered during the design of the chiller, which increases the complexity of design, manufacturing, maintenance and control, and increases the initial cost and operation and maintenance costs. Lubricating oil leakage will also cause environmental pollution. At the same time, the lubricating oil enters the evaporator and condenser with the refrigerant, which will affect the heat exchange effect and system energy efficiency, and will cause unit performance degradation after long-term operation.

[0025] Oil-lubricated bearing centrifuges currently account for approximately 82% of the central air-conditioning centrifugal unit market. However, since lubricating oil is required to lubricate the bearings in their systems, the oil lubrication system and oil separation system for oil supply and return must be considered during the design of chillers. This increases the complexity of design, manufacturing, maintenance, and control, and significantly increases initial and operating maintenance costs. Lubricating oil leakage can also cause environmental pollution. At the same time, lubricating oil enters the evaporator and condenser along with the refrigerant, affecting the heat exchange effect and system energy efficiency, and can cause unit performance deterioration after long-term operation.

[0026] In view of the corresponding shortcomings of the above-mentioned oil-containing centrifuges, centrifuges are gradually developing towards lubricating oil-free systems. Oil-free centrifugal units eliminate oil lubrication system components, avoid the degradation of heat exchanger performance due to oil contamination, and also simplify the system structure, which has received more attention in the HVAC industry.

[0027] There are currently three main development directions for oil-free centrifuges. One is the oil-free centrifugal unit using magnetic bearings. However, magnetic bearings cannot completely solve the reliability problem of the unit in the event of a sudden power outage due to the large number of sensors and complex control systems.

[0028] The second is the oil-free centrifugal unit using air bearings. Since air bearings are only suitable for high-speed and light-load conditions, the cooling capacity of the oil-free centrifugal unit using air bearings is limited and its reliability is poor when the load suddenly changes.

[0029] The third approach is to use refrigerant-lubricated ceramic bearings in oil-free centrifugal units. Using refrigerant as the lubricant for the ceramic bearings within the system simplifies the control system design. Furthermore, the ceramic bearings' strong impact resistance enables the development of high-capacity oil-free centrifuges. Based on the advantages of the last oil-free centrifuge development direction, refrigerant-lubricated rolling ceramic bearings are increasingly being researched and applied in centrifugal units.

[0030] Oil-free centrifugal units with ceramic bearings use refrigerant as the bearing lubricant. Unlike high-viscosity lubricants, refrigerant has an extremely low viscosity. For example, R134a has a viscosity of 0.162 cSt at 25°C, which is approximately 1 / 100 of the viscosity of lubricant oil. When the refrigerant supply is interrupted, the low-viscosity refrigerant liquid is unlikely to remain on the bearing surface. Even if some refrigerant does remain, it will evaporate due to its volatility. Furthermore, when the refrigerant liquid is supplied to the compressor bearings, it is prone to throttling flash due to the flow resistance and local resistance along the way. This can lead to the generation of refrigerant gas. When this refrigerant gas enters the bearings to lubricate them, it can cause severe wear on the rolling elements, severely impacting bearing life and compressor operational stability. In summary, when refrigerant is used as the bearing lubricant, a continuous and stable refrigerant supply is essential during startup, operation, and shutdown to ensure proper bearing lubrication.

[0031] Based on this, some embodiments of the present application provide an oil-free bearing liquid supply air-conditioning system and a control method thereof, in which refrigerant liquid is used instead of lubricating oil to lubricate the bearings in the compressor in the oil-free bearing liquid supply air-conditioning system, and different refrigerant liquid supply sources and paths are adopted according to the different operating states of the refrigeration system, including natural liquid supply due to the high pressure pressure difference of the condenser existing when the refrigeration system is running and forced liquid supply using additional power provided by a refrigerant liquid pump. Through two different refrigerant liquid supply methods and a control method, it is ensured that in all stages of the operation of the oil-free refrigeration system, the bearings can obtain sufficient refrigerant liquid supply, and their lubrication state can be effectively guaranteed, thereby ensuring the normal operation of the oil-free refrigeration system.

[0032] Figure 1 is a system block diagram of an oil-free bearing liquid supply air conditioning system provided in some embodiments of the present application, Figure 2 is a compressor system block diagram provided in some embodiments of the present application; Figure 3 is a refrigeration system structure diagram provided in some embodiments of the present application.

[0033] As shown in FIG1 , 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 , wherein the refrigeration system 31 is located in the box system 200 .

[0034] The refrigeration system 31 includes:

[0035] The compressor 42 is the core of the refrigeration system. It is configured to compress the gaseous refrigerant in a low-temperature and low-pressure state and discharge the compressed gaseous refrigerant in a high-temperature and high-pressure state. The compressor 42 inhales the low-temperature and low-pressure refrigerant gas from the intake pipe, and drives the impeller to rotate through the operation of the motor, thereby increasing the gas speed, and then greatly increases its pressure after being expanded by the diffuser, thereby providing power for the refrigeration cycle.

[0036] Economizer 23 is configured to expand high-pressure liquid refrigerant into a medium-pressure gas-liquid two-phase refrigerant. In some embodiments, economizer 23 is a tank container within the system with a corresponding internal structural design. When the refrigerant liquid enters the economizer, flashover occurs, generating a portion of refrigerant gas. This portion of refrigerant gas flows through the air supply line into compressor 42 to provide air for compressor 42. The remaining refrigerant gas-liquid two-phase refrigerant after flashover flows out of economizer 23.

[0037] Evaporator 29 is configured to absorb heat from the surrounding environment and evaporate the medium-pressure gas-liquid two-phase refrigerant to form a low-temperature, low-pressure gas-phase refrigerant. The low-temperature, low-pressure gas-phase refrigerant is then returned to compressor 42. The evaporator consists of a heating chamber and an evaporation chamber. The heating chamber is configured to provide the heat required for evaporation of the liquid, causing it to boil and vaporize; the evaporation chamber is configured to completely separate the gas and liquid phases.

[0038] The condenser 19 is a type of heat exchanger, and is configured to condense a high-temperature and high-pressure gas-phase refrigerant into a high-pressure liquid-phase refrigerant, and release heat to the surrounding environment during the condensation process.

[0039] The subcooler 35 is a heat exchanger configured to further cool the saturated liquid without a phase change.

[0040] The refrigeration liquid pump 20 is configured to provide sufficient conveying power for the refrigerant when the pressure difference naturally established during the operation of the system is insufficient to serve as the liquid supply power, so that the refrigerant liquid can still be supplied to the compressor bearings located at a higher position in the system at a sufficient flow rate from a lower position in the system.

[0041] A first bearing lubricating liquid supply path 125 from the condenser 19 to the compressor 42 and a second bearing lubricating liquid supply path 126 from the condenser 19 to the compressor 42 (as shown in FIG3 ). The first bearing lubricating liquid supply path 125 and the second bearing lubricating liquid supply path 126 have at least a portion of their paths connected in parallel, and at least a portion of their paths shared. The second bearing lubricating liquid supply path of the compressor 42 further includes a refrigerant liquid pump 20; a subcooler 35 is disposed on the shared path of the first bearing lubricating liquid supply path 125 and the second bearing lubricating liquid supply path 126; the first bearing lubricating liquid supply path 125 and the second bearing lubricating liquid supply path 126 are both configured to transfer refrigerant liquid to the compressor 42 to lubricate the bearings of the compressor 42; the controller 100 is configured to be in communication with the refrigeration system 31, and the controller 100 is configured to control the refrigeration system 31.

[0042] In the embodiment shown in the present application, the controller 100 refers to a device that can generate an operation control signal based on an instruction operation code and a timing signal to instruct the refrigeration system to execute the control instruction. For example, the controller can be a central processing unit (CPU), a general-purpose processor network processor (NP), a digital signal processor (DSP), a microprocessor, a microcontroller, a programmable logic device (PLD), or any combination thereof. The controller can also be other devices with processing functions, such as circuits, devices, or software modules, and some embodiments of the present application do not impose any restrictions on this. Among them, the instruction operation code refers to a pre-set control logic program. The corresponding action logic can be stored in the controller through programming, including a series of judgment conditions and execution actions. When the corresponding judgment conditions are met during the operation of the unit, the relevant actions are executed to control the relevant components in the refrigeration system to operate.

[0043] In addition, the controller 100 is configured to control the operation of various components in the refrigeration system 31 so that the various components of the refrigeration system 31 operate to achieve various predetermined functions of the air-conditioning system.

[0044] The pump is a component that transports or pressurizes a fluid. It transfers the mechanical energy of the prime mover or other external energy to the liquid, thereby increasing the liquid's energy. The refrigeration liquid pump is used to forcibly extract refrigerant liquid through the second bearing lubrication supply path 126 to supply the compressor 42.

[0045] It should be noted that, for example, 11 to 12 appearing in the drawings of this application indicate that component 11 belongs to component 12, for example, 105 to 126 indicate that path 105 belongs to path 126, and 110 to 125 / 126 indicate that path 110 belongs to path 125 or path 126. Other similar numbers appearing in the drawings also follow the above description.

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

[0047] The motor 4 is the prime mover of the compressor 42 and is configured to provide power for the operation of the compressor 42. Through the supply of electricity, the stator structure of the motor 4, which is wound by coils, can generate a magnetic field. Under the action of the magnetic field, the rotor structure of the motor 4 will rotate, thereby providing driving force for the rotating parts of the compressor 42.

[0048] Bearing 3, which is located on motor 4 and is configured to provide support for the rotor in motor 4, reduce the friction coefficient during the rotation of the rotor, and ensure the rotation accuracy of the rotor;

[0049] The impellers (e.g., the first-stage impeller 1 and the second-stage impeller 2) are arranged in a "back-to-back" arrangement. This arrangement allows the axial loads generated in the two or more impeller stages to cancel each other out, thereby balancing the axial loads.

[0050] The first bearing lubrication supply path and the second bearing lubrication supply path are both configured to deliver refrigerant liquid to the compressor 42 to lubricate the bearings 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 used to compress gas and includes a rotor and a stator. The rotor includes an impeller and a shaft. The impeller has blades, a balance disk and a portion of a shaft seal; the main body of the stator is a cylinder and also includes a diffuser, a bend, a return flow device, an intake pipe, an exhaust pipe and other devices. When the impeller rotates at high speed, the gas rotates with it, and under the action of centrifugal force, the gas is thrown into the diffuser at the back, and a vacuum zone is formed at the impeller. At this time, fresh gas from the outside enters the impeller. The impeller rotates continuously, and the gas is continuously sucked in and thrown out, thereby maintaining the continuous flow of gas.

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

[0053] In some embodiments, the bearings are ceramic bearings, which are corrosion-resistant and suitable for use in highly corrosive working environments; temperature changes have little effect on ceramic bearings and can withstand larger temperature changes; ceramic bearings have a higher elastic modulus and rarely deform due to force; ceramic balls have a lower density than steel and are lighter in weight, which can reduce the friction caused by centrifugal force during rotation and extend the life of the bearing.

[0054] In some embodiments, the subcooler can be a plate heat exchanger. Plate heat exchangers have high heat exchange efficiency and can achieve a large amount of heat exchange with a small heat exchange temperature difference, thereby effectively improving the subcooling degree of the refrigerant liquid. In addition, plate heat exchangers occupy a small volume, occupying less space in the unit system, and are easy to design and implement.

[0055] The above-described embodiment of the present disclosure provides a refrigeration system, as shown in FIG3 . The refrigeration system 31 lubricates the bearings of the motor in the compressor with refrigerant liquid and provides two refrigerant liquid supply paths. The two refrigerant liquid supply paths are a first bearing lubrication supply path 125 from the condenser 19 to the compressor 42, and a second bearing lubrication supply path 126 from the condenser 19 to the compressor 42. That is, both bearing lubrication liquid supply paths transmit the refrigerant liquid generated by the condenser 19 to the compressor 42, and, of the two liquid supply paths, the first bearing lubrication liquid supply path 125 is a path that does not require a refrigeration liquid pump 20, and the second bearing lubrication liquid supply path 126 requires the refrigeration liquid pump 20 to provide power. In this way, during the entire operation of the refrigeration system, different liquid supply paths can be selected at different stages according to the operating status of the refrigeration system, ensuring that the bearings in the compressor can obtain sufficient refrigerant liquid for lubrication at each stage, thereby ensuring the safety of the system operation; at the same time, the subcooler 35 is connected to the common path of the first bearing lubrication liquid supply path 125 and the second bearing lubrication liquid supply path 126, and the subcooler 35 is configured to further condense the refrigerant liquid, thereby better lubricating the bearings of the compressor 42.

[0056] As shown in Figures 1 and 3, the above-mentioned first bearing lubrication liquid supply path and the second bearing lubrication liquid supply path respectively include an initial path 120, a front path 104, a rear path 110 and a final path 121 that are connected to each other; the front path 104 of the first bearing lubrication liquid supply path and the front path 105 of the second bearing lubrication liquid supply path are arranged in parallel; the initial path 120 of the above-mentioned first bearing lubrication liquid supply path and the initial path 120 of the above-mentioned second bearing lubrication liquid supply path are the same path; the rear path 110 of the above-mentioned first bearing lubrication liquid supply path and the rear path 110 of the above-mentioned second bearing lubrication liquid supply path are the same path; the final path 121 of the first bearing lubrication liquid supply path and the final path 121 of the second bearing lubrication liquid supply path are the same path.

[0057] That is, as shown in Figures 1 and 3, the first bearing lubrication supply path and the second bearing lubrication supply path are connected in parallel in the front section and merged into one in the initial section, the rear section, and the terminal section. Both paths transmit refrigerant liquid to the bearings in the compressor via the terminal path 121. This arrangement not only reduces the number of piping in the unit system, but also simplifies the merger of the first bearing lubrication supply path and the second bearing lubrication supply path by using a common piping section. It also improves the maintainability of the unit system piping, eliminating the need for tedious inspection of multiple piping sections in the event of a piping failure.

[0058] Among them, the initial section path 120 of the first bearing lubrication supply path includes a first filter 34; the front section path 104 of the first bearing lubrication supply path includes a first one-way valve 11; the front section path 105 of the second bearing lubrication supply path includes a refrigeration liquid pump 20; the rear section path 110 of the first bearing lubrication supply path includes a pressure regulating valve 10 and a second filter 9 arranged in sequence; the subcooler 35 connects the rear section path 110 of the first bearing lubrication supply path and the final section path 121 of the first bearing lubrication supply path.

[0059] It should be noted that the refrigeration system includes multiple flow paths, such as liquid flow paths and gas flow paths. The flow paths include multiple transmission components and connecting pipes. The transmission components are, for example, one-way valves, filters, pumps, etc. Liquid or gas can pass through the transmission components. The connecting pipes connect adjacent transmission components to allow liquid or gas to circulate.

[0060] As shown in Figure 3, as the refrigerant liquid flows through the first bearing lubrication supply path, it sequentially passes through the first filter 34, the first check valve 11, the pressure regulating valve 10, the second filter 9, and the subcooler 35. As the refrigerant liquid flows through the second bearing lubrication supply path, it sequentially passes through the first filter 34, the refrigerant liquid pump 20, the pressure regulating valve 10, the second filter 9, and the subcooler 35.

[0061] The functions of the transmission components in the two fluid supply paths are as follows: the first filter 34 is configured to filter impurities, such as solid particles, from the refrigerant liquid in the initial path 120 of the first bearing lubricating fluid supply path; the first one-way valve 11 is configured to prevent reverse flow of the refrigerant liquid in the initial path 104 of the first bearing lubricating fluid supply path; the second filter 9 is configured to filter small amounts of impurities, such as solid particles, from the refrigerant liquid in the final path 110 of the first bearing lubricating fluid supply path; and the pressure regulating valve 10 is configured to regulate the pressure in the final path 110 of the first bearing lubricating fluid supply path to maintain a constant pressure. The subcooler 35 is configured to further cool the refrigerant liquid in the final path 110 of the first bearing lubricating fluid supply path before supplying the refrigerant to the bearings of the compressor 42 via the final path 121 of the first bearing lubricating fluid supply path.

[0062] In some embodiments, the front section of the second bearing lubrication supply path includes at least two refrigeration liquid pumps, and the at least two refrigeration liquid pumps are arranged in parallel. For example, as shown in FIG3 , the at least two refrigeration liquid pumps 20 include a main refrigeration liquid pump 201 and at least one backup refrigeration liquid pump 202.

[0063] Multiple refrigeration liquid pumps are arranged in parallel on the second bearing lubrication supply path. This can avoid the situation where one or more refrigeration liquid pumps fail or are overloaded during system operation and cannot supply liquid to the bearing. When such a situation occurs, it can quickly switch to the normally operating backup refrigeration liquid pump path to ensure normal bearing supply.

[0064] In some embodiments, the refrigerant liquid pump 20 is powered by an uninterruptible power supply.

[0065] An uninterruptible power supply (UPS) is an uninterruptible power supply that includes an energy storage device. It's primarily used to provide uninterrupted power to devices that require high power stability. This allows the refrigerant pump to continue operating even in the event of an air conditioning system power outage, pumping out the refrigerant and maintaining lubrication for the compressor motor bearings.

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

[0067] FIG4 is a partial structural diagram of a liquid supply source provided in some embodiments of the present application; FIG5 is a partial structural diagram of another liquid supply source provided in some embodiments of the present application.

[0068] The above-mentioned refrigeration system 31 also includes an identical liquid supply source, as shown in Figures 4 and 5. The liquid supply source is a first liquid supply sac 13 arranged below the condenser 19. The first liquid supply sac 13 is connected to the condenser 19 and is configured to store the refrigerant liquid in the condenser 19; and the initial section path 120 of the first bearing lubrication liquid supply path is connected to the first liquid supply sac 13, and the initial section path 120 of the second bearing lubrication liquid supply path is connected to the first liquid supply sac 13.

[0069] Among them, since there is a subcooling pipe section in the condenser 19, the refrigerant liquid in the first liquid supply bag 13 is all subcooled refrigerant liquid. The subcooled refrigerant liquid is used to supply lubrication for the bearing 3 to ensure that there is little or no gas in the liquid supply liquid and has a good cooling effect.

[0070] FIG6 is a partial structural diagram of a refrigeration system provided in some embodiments of the present application, and FIG7 is a partial path structural diagram of a refrigeration system provided in some embodiments of the present application.

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

[0072] Among them, after the refrigeration system 31 is shut down, the first solenoid valve 33 is opened, and the high pressure of the condenser 19 and the low pressure of the evaporator 29 can be quickly balanced through the connecting pipe 103 between the condenser 19 and the evaporator 29, thereby ensuring that there is sufficient refrigerant liquid in the evaporator 29 and the condenser 19, that is, at 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 Figures 6 and 7, the refrigeration system 31 further includes a bearing lubrication return liquid 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 return liquid or gas return path 118 from the compressor 42 to the evaporator 29 includes a second solenoid valve 12, which is configured to control the opening and closing of the bearing lubrication return liquid or gas return path 118.

[0074] As shown in Figure 6, the above-mentioned refrigeration system 31 also 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 is configured to collect the pressure value of the condenser 19; the second pressure sensor 26 is connected to the evaporator 29 and is configured to collect the pressure value of the evaporator 29; the third pressure sensor 8 is connected to the end section of the first bearing lubrication supply path and is configured to collect the pressure value of the bearing supply liquid; the fourth pressure sensor 30 is connected to the bearing lubrication return liquid or return air path 118 and is configured to collect the pressure value of the bearing lubrication return liquid or return air; the fifth pressure sensor 5 is connected to the exhaust port of the compressor 42 and is configured to collect the compressor exhaust pressure.

[0075] As shown in Figures 6 and 7, the above-mentioned refrigeration system also 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 the liquid level of the condenser 19; the second liquid level sensor 22 is configured to monitor the liquid level of the economizer 23; the first temperature sensor 7 is configured to monitor the temperature of the last section 121 of the first bearing lubrication supply path; the second temperature sensor 6 is configured to monitor the temperature of the exhaust path 119 from the compressor 42 to the condenser 19.

[0076] As shown in Figure 7, the above-mentioned refrigeration system 31 also includes: a 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 4 cooling liquid supply path 108 from the condenser 19 to the compressor 42; a refrigerant liquid supply path 106 from the condenser 19 to the economizer 23; a first air supply path 109 from the economizer 23 to the compressor 42; a return liquid path 107 from the economizer 23 to the evaporator 29; a motor cooling return air path 117 from the compressor 42 to the evaporator 29; a heat exchange path 122 from the condenser 19 to the subcooler 35; a second air supply path 123 from the subcooler 35 to the first air supply path 109, or a subcooling return air path from the subcooler 35 to the bearing lubrication return liquid or return air path 118.

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

[0078] In some embodiments, as shown in Figure 7, the above-mentioned refrigeration system 31 also 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 is configured to store the refrigerant liquid in the condenser 19; the above-mentioned motor cooling liquid supply path 108 and the refrigerant liquid supply path 106 are both connected to the second liquid supply bag 14.

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

[0080] The second liquid supply bladder 14 is connected to the motor cooling liquid supply path 108 and the refrigerant liquid supply path 106 and is configured to provide refrigerant liquid to the economizer 23. The economizer 23 then exchanges heat with the refrigerant liquid to generate refrigerant gas. This refrigerant gas flows along the first gas supply path 109 to enter the compressor 42 for gas replenishment. Simultaneously, the second gas supply path 123 from the subcooler 35 to the first gas supply path 109 also flows through the first gas supply path 109 to enter the compressor 42 for gas replenishment. The remaining refrigerant liquid in the economizer 23 flows along the liquid return path 107 to enter the evaporator 29. Simultaneously, the second liquid supply bladder 14 is configured to provide refrigerant liquid to the motor in the compressor 42 for motor cooling. The cooled refrigerant (liquid or gas) returns to the evaporator 29 via the motor cooling return path 117.

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

[0082] Figure 8 is an overall structural diagram of a refrigeration system provided in some embodiments of the present application; Figure 9 is a stable startup flow chart of a refrigeration system provided in some embodiments of the present application; Figure 10 is a shutdown and power-off flow chart of a refrigeration system provided in some embodiments of the present application.

[0083] Some embodiments of the present application provide a refrigeration system including two different bearing lubrication supply paths. The two bearing lubrication supply paths are applied to different stages of the refrigeration system operation. The control method of the oil-free bearing lubrication supply air-conditioning system is included in different stages of the refrigeration system operation. The full stage of the refrigeration system operation includes (as shown in Figures 8 to 10):

[0084] (1) Refrigeration system startup phase;

[0085] (2) Stable operation stage of the refrigeration system;

[0086] (3) Normal power-off and shutdown stage of the refrigeration system;

[0087] (4) The refrigeration system shuts down due to abnormal power outage.

[0088] Among them, stages (1) and (3) adopt the forced liquid supply method of the refrigeration liquid pump, while stage (2) needs to determine the size of the refrigeration system pressure difference and the bearing pressure difference to determine whether the forced liquid supply method of the refrigeration liquid pump and the natural liquid supply method of the refrigeration system pressure difference are operated in parallel or separately. Stage (4) first adopts the natural liquid supply method of the refrigeration system pressure difference. If the pressure difference is insufficient, the emergency backup power supply is turned on and the forced liquid supply method of the refrigeration liquid pump is adopted. The following is a detailed description of the operation process of the entire stage with reference to Figure 8.

[0089] Regardless of the stage of the refrigeration system, all sensor devices in the refrigeration system are in full-process working state. For example, the first pressure sensor 15 and the second pressure sensor 26 collect the pressure of the condenser 19 and the pressure in the evaporator 29 in real time, and set their collected values ​​to P1 and P2; the third pressure sensor 8 and the fourth pressure sensor 30 collect the pressure of the bearing supply liquid and the pressure of the bearing return liquid or return air in real time, and the first temperature sensor 7 collects the temperature of the bearing supply liquid in real time, and sets its collected values ​​to P3, P4, and T3; the first liquid level sensor 17 collects the liquid level of the condenser 19 in real time, and sets its collected value to L con ; Set the subcooling degree of the bearing supply liquid to T sub , calculated from the bearing supply fluid pressure value P3 and the bearing supply fluid temperature T3; set the minimum allowable subcooling degree of the bearing supply fluid T min , this value is set according to the actual situation, for example it can be set to 1 ° C; set the refrigeration system operating pressure difference to ΔP = P1-P2; set the bearing supply pressure difference to ΔP brg =P3-P4; Set the minimum allowable pressure difference of the bearing fluid supply to ΔP min , the value range is 0.05MPa to 0.35MPa, and the exemplary value is 0.2MPa; set the pressure difference judgment time for switching the liquid supply mode to T s1 , the value is set according to the actual situation, for example, it can be set to 1min; set the upward bias value of the bearing hydraulic pressure difference to P up , the value range is 0MPa to 0.35MPa, and can be set to 0.15MPa for example; set the downward bias value of the bearing pressure difference to P down , the value range is 0MPa to 0.35MPa, and can be set to 0.05MPa for example; set the fault alarm pressure difference judgment time to the second set time T s2 , this value is set according to the actual situation, and can be set to 30s for example; the compressor power-off determination time is set to the third set time T s3 , this value is set according to the actual situation, and can be set to 3min for example; set the minimum allowable liquid level of the condenser 19 to L cmin , this value is set according to the actual situation, and can be set to 30% for example.

[0090] During all stages of the unit's operation, whether it is the startup stage, normal operation stage, or the unit's shutdown stage, the various sensor devices in the refrigeration system will continuously collect relevant status parameter data of the unit's operation, such as pressure, temperature, refrigerant flow, etc., at a certain collection frequency.

[0091] It should be noted that the above values ​​are pre-set before the refrigeration system is started.

[0092] In the following stages, the execution body of each step is the controller, which can control the opening, closing, operation, etc. of each device in the refrigeration system.

[0093] 1) Refrigeration system startup phase:

[0094] As shown in Figures 8 and 9, before the entire refrigeration system 31 is started, a large amount of refrigerant liquid will accumulate in the evaporator 29 and condenser 19 of the refrigeration system. At this time, the first solenoid valve 33 is opened, connecting the connecting pipe path 103 at the bottom of the condenser 19 to the evaporator 29, so that the refrigerant liquid level is evenly distributed in both vessels. In addition, because the condenser is arranged lower than the evaporator in the unit's structural layout, the first liquid supply sac 13 at the bottom of the condenser 19 is ensured to be full of refrigerant liquid before the system is started. Because the first liquid supply sac 13 is located below the condenser 19, under the influence of gravity, as long as there is refrigerant liquid in the condenser 19, the refrigerant liquid will be automatically replenished to the first liquid supply sac 13.

[0095] As shown in S1 and S2 in Figure 9, when the refrigeration system 31 starts running, the controller 100 turns on the main refrigeration liquid pump 201, detects and closes the first solenoid valve 33 on the bottom connecting pipe between the condenser 19 and the evaporator 29; and detects and opens the second solenoid valve 12 on the bearing return liquid (return air) path 118.

[0096] The hydraulic pressure difference ΔP in the bearing brg Greater than the minimum allowable pressure difference ΔP of the bearing fluid supply min , and the duration is greater than the first set time T s1 When ΔP is satisfied brg >ΔP min , and duration>T s1 , the controller 100 controls the operation of the compressor 42 ; and supplies fluid to the bearings of the compressor 42 through the second bearing lubrication fluid supply path 126 .

[0097] The main refrigerant liquid pump 201 will continuously pump refrigerant liquid from the first liquid supply bag 13 which contains a large amount of refrigerant liquid. The refrigerant liquid will pass through the first filter 34, the main refrigerant liquid pump 201, the pressure regulating valve 10, the second filter 9 and the subcooler 35 along the initial section 120 of the second bearing lubrication supply path to the final section 121 of the second bearing lubrication supply path, and then be divided into a bearing lubrication supply branch path 111 and a bearing lubrication supply branch path 112 to lubricate the left and right bearings 3 in the compressor. After the bearings 3 are lubricated, the rotor gradually rotates stably, and the refrigeration system 31 is started. The lubricated refrigerant returns to the evaporator 29 along the bearing lubrication return path 118 through the fourth pressure sensor 30 and the second solenoid valve 12 respectively.

[0098] As shown in Figure 9, S2 and S5, the bearing pressure difference ΔP brg Less than or equal to the minimum allowable pressure difference ΔP of the bearing fluid supply min , or the bearing supply pressure difference ΔP brg Greater than the minimum allowable pressure difference ΔP of the bearing fluid supply min , and the duration is less than or equal to the first set time T s1 In the case of ΔP brg >ΔP min , and duration>T s1 The controller 100 determines that the operating state of the main refrigerant liquid pump 201 is poor, and switches to using the backup refrigerant liquid pump 202, and also supplies liquid to the bearings of the compressor 42 through the second bearing lubrication liquid supply path 126.

[0099] As shown in S3, S6 and S7 in FIG9 , during the period when the standby refrigerant liquid pump 202 is turned on and the second bearing lubrication liquid supply path 126 is used to supply liquid to the bearing of the compressor 42 , if the bearing supply pressure difference ΔP is satisfied, brg Greater than the minimum allowable pressure difference ΔP of the bearing fluid supply min , and the duration is greater than the first set time T s1 When ΔP is satisfied brg >ΔP min , and duration>T s1 , the controller 100 determines that the operating state of the standby refrigerant liquid pump 202 is good and can normally supply liquid to the bearings of the compressor 42 through the second bearing lubrication liquid supply path 126, and the compressor 42 continues to operate; if the bearing supply liquid pressure difference ΔP is not satisfied brg Greater than the minimum allowable pressure difference ΔP of the bearing fluid supply min , and the duration is greater than the first set time T s1 In the case of ΔP brg >ΔP min , and duration>T s1, the controller 100 determines that the operating state of the standby refrigeration liquid pump 202 is poor, and an alarm prompts to check the bearing lubrication liquid supply path.

[0100] 2) The refrigeration system gradually stabilizes:

[0101] As shown in S4 and S15 in FIG8 and FIG9, after the refrigeration system 31 is started, the compressor 42 starts to run, and the pressure difference ΔP in the refrigeration system is greater than the minimum allowable pressure difference ΔP of the bearing supply liquid. min and the upward offset value P of the bearing supply pressure difference up The sum of the time and duration is greater than the first set time T s1 In the case of ΔP>ΔP min +P up , and the duration is greater than T s1 The controller 100 determines that the refrigeration system 31 meets the pressure difference condition for natural liquid supply. At this time, the refrigerant liquid in the bearing liquid supply liquid bag 13 can be transported to the bearing 3 for lubrication by only the refrigeration system pressure difference ΔP, and then the main refrigeration liquid pump 201 is turned off; the first bearing lubrication liquid supply path 125 is used to supply liquid to the bearing of the compressor 42.

[0102] In S14, S16, S18 and S19 in FIG9 , when the controller 100 turns off the refrigerant liquid pump 20 and supplies liquid to the bearings of the compressor 42 via the first bearing lubrication liquid supply path 125, one of the operating states is as follows:

[0103] The hydraulic pressure difference ΔP in the bearing brg Greater than or equal to the minimum allowable pressure difference ΔP of the bearing fluid supply min In the case of ΔP brg <ΔP min , no action is performed.

[0104] The hydraulic pressure difference ΔP in the bearing brg Less than the minimum allowable pressure difference ΔP of the bearing fluid supply min , and the bearing supply pressure difference ΔP brg Greater than or equal to the minimum allowable pressure difference ΔP of the bearing fluid supply min and the downward offset value P of the bearing supply pressure difference down The difference between the bearing pressure and the bearing oil pressure difference ΔP brg Less than the minimum allowable pressure difference ΔP of the bearing fluid supply min , and the bearing supply pressure difference ΔP brg Less than the minimum allowable pressure difference ΔP of the bearing fluid supply min and the downward offset value P of the bearing supply pressure difference down The difference between the two, and its duration is less than or equal to T s2 When ΔP is satisfied brg <ΔP min, and does not satisfy ΔP brg <ΔP min -P down , and duration>T s2 The controller 100 controls the refrigeration system 31 to sound an alarm to prompt the user to check the bearing lubrication supply path.

[0105] As shown in S18 and S20 in Figure 9, the bearing supply pressure difference ΔP brg Less than the minimum allowable pressure difference ΔP of the bearing fluid supply min and the downward offset value P of the bearing supply pressure difference down The difference between the two, and the duration is greater than the second set time T s2 When ΔP is satisfied brg <ΔP min -P down , and duration>T s2 , the controller 100 controls the refrigeration system 31 to alarm and shut down.

[0106] According to the set bearing pressure difference determination interval, its lower limit is ΔP min -P down , when the bearing supply pressure difference ΔP brg When the limit is reached, it indicates that there is a risk of insufficient bearing lubrication power in the system. At this time, the duration of the problem will determine whether to alarm or shut down. When the duration is greater than T s2 This indicates that the risk of insufficient power is at its greatest and the amount of refrigerant liquid supplied to the motor bearings for lubrication is very small. Therefore, in order to protect the compressor motor bearings from damage due to dry friction, the control logic directly causes the controller 100 to control the refrigeration system 31 to alarm and shut down, so that the compressor can exit this state in the shortest possible time to protect the bearings.

[0107] In S17, S21 and S36 in FIG9 , during the period when the refrigerant liquid pump 20 is turned off and the first bearing lubricating liquid supply path 125 is used to supply liquid to the bearing of the compressor 42, another operating state is as follows:

[0108] The pressure difference ΔP in the refrigeration system 31 is less than the minimum allowable pressure difference ΔP of the bearing supply fluid min and the downward offset value P of the bearing supply pressure difference down The difference between the two, and the duration is greater than the first set time T s1 In the case of ΔP<ΔP min -P down , and duration>T s1At this time, the controller 100 considers that the pressure difference ΔP of the refrigeration system alone is insufficient to supply liquid lubrication for the bearing, and turns on the main refrigeration liquid pump 201; the second bearing lubrication liquid supply path 126 supplies liquid to the bearing of the compressor 42, and the main refrigeration liquid pump 201 pumps refrigerant liquid from the bearing liquid supply sac 13 to supply liquid lubrication for the bearing 3. If ΔP < ΔP is not satisfied min -P down , and duration>T s1 , no action is performed.

[0109] In S22, S27 and S24 in FIG9 , when the controller 100 starts the main refrigerant liquid pump 201 and supplies liquid to the bearings of the compressor 42 via the second bearing lubrication liquid supply path 126, one of the operating states is as follows:

[0110] The hydraulic pressure difference ΔP in the bearing brg Less than or equal to the minimum allowable pressure difference ΔP of the bearing fluid supply min , or the bearing supply pressure difference ΔP brg Greater than the minimum allowable pressure difference ΔP of the bearing fluid supply min , and the duration is less than or equal to the first set time T s1 In the case of ΔP brg >ΔP min , and duration>T s1 , the controller 100 determines that the operating state of the main refrigerant liquid pump 201 is poor, and switches to use the backup refrigerant liquid pump 202. brg >ΔP min , and duration>T s1 , no action is performed.

[0111] 9 S24, S25, S26 and S27, when the standby refrigerant liquid pump 202 is turned on, the second bearing lubrication liquid supply path 126 is used to supply liquid to the bearing of the compressor 42: if the bearing supply pressure difference ΔP is satisfied, brg Greater than the minimum allowable pressure difference ΔP of the bearing fluid supply min , and the duration is greater than the first set time T s1 When ΔP is satisfied brg >ΔP min , and duration>T s1 , the controller 100 determines that the operating state of the standby refrigerant liquid pump 202 is good and that the bearings of the compressor 42 can be normally supplied with liquid through the second bearing lubrication liquid supply path 126, and no action is performed; if the bearing supply pressure difference ΔP is not satisfied brg Greater than the minimum allowable pressure difference ΔP of the bearing fluid supply min , and the duration is greater than the first set time T s1 In the case of ΔPbrg >ΔP min , and duration>T s1 If the controller 100 determines that the operating status of the standby refrigeration liquid pump 202 is poor, an alarm is issued to prompt the user to check the bearing lubrication supply path.

[0112] In S8, S9, S14 and S10 in FIG9 , the controller 100 starts the main refrigerant liquid pump 201 to supply liquid to the bearings of the compressor 42 via the second bearing lubrication liquid supply path 126 , wherein another operating state is as follows:

[0113] The hydraulic pressure difference ΔP in the bearing brg Less than or equal to the minimum allowable pressure difference ΔP of the bearing fluid supply min , or the bearing supply pressure difference ΔP brg Greater than the minimum allowable pressure difference ΔP of the bearing fluid supply min , and the duration is less than or equal to the first set time T s1 In the case of ΔP brg >ΔP min , and duration>T s1 , the controller 100 determines that the operating state of the main refrigerant liquid pump 201 is poor, and switches to use the backup refrigerant liquid pump 202. brg >ΔP min , and duration>T s1 , the controller 100 controls the refrigeration system 31 to perform no action.

[0114] As shown in S11, S12 and S13 in Figure 9, during the use of the standby refrigerant liquid pump, if the bearing supply pressure difference ΔP is satisfied brg Greater than the minimum allowable pressure difference ΔP of the bearing fluid supply min , and the duration is greater than the first set time T s1 When ΔP is satisfied brg >ΔP min , and duration>T s1 , the controller 100 determines that the operating state of the standby refrigerant liquid pump 202 is good and that the bearings of the compressor 42 can be normally supplied with liquid through the second bearing lubrication liquid supply path 126, and no action is performed; if the bearing supply pressure difference ΔP is not satisfied brg Greater than the minimum allowable pressure difference ΔP of the bearing fluid supply min , and the duration is greater than the first set time T s1 In the case of ΔP brg >ΔP min , and duration>T s1 , the controller 100 determines that the operating state of the standby refrigeration liquid pump 202 is poor, and an alarm prompts to check the bearing lubrication liquid supply path.

[0115] During the period when the controller 100 starts the main refrigerant liquid pump 201 and supplies liquid to the bearings of the compressor 42 via the second bearing lubrication liquid supply path 126, another operating state is as follows:

[0116] In S23, S26, S28 and S36 in FIG9 , when the controller 100 starts the main refrigerant liquid pump 201 and supplies liquid to the bearings of the compressor 42 via the second bearing lubrication liquid supply path 126, one of the operating states is as follows:

[0117] The hydraulic pressure difference ΔP in the bearing brg Greater than or equal to the minimum allowable pressure difference ΔP of the bearing fluid supply min In the case of ΔP brg <ΔP min , the controller 100 controls the refrigeration system 31 to perform no action.

[0118] The hydraulic pressure difference ΔP in the bearing brg Less than the minimum allowable pressure difference ΔP of the bearing fluid supply min , and the bearing supply pressure difference ΔP brg Greater than or equal to the minimum allowable pressure difference ΔP of the bearing fluid supply min and the downward offset value P of the bearing supply pressure difference down The difference between the bearing pressure and the bearing oil pressure difference ΔP brg Less than the minimum allowable pressure difference ΔP of the bearing fluid supply min , and the bearing supply pressure difference ΔP brg Less than the minimum allowable pressure difference ΔP of the bearing fluid supply min and the downward offset value P of the bearing supply pressure difference down The difference between the two, and its duration is less than or equal to T s2 When ΔP is satisfied brg <ΔP min , and does not satisfy ΔP brg <ΔP min -P down , and duration>T s2 , the controller 100 controls the refrigeration system 31 to alarm and prompt to check the bearing lubrication supply path. brg <ΔP min In this case, the controller 100 controls the refrigeration system 31 to perform no action.

[0119] As shown in S28 and S29 in Figure 9, the bearing supply pressure difference ΔP brg Less than the minimum allowable pressure difference ΔP of the bearing fluid supply min and the downward offset value P of the bearing supply pressure difference down The difference between the two, and the duration is greater than the second set time T s2 When ΔP is satisfiedbrg <ΔP min -P down , and duration>T s2 , the controller 100 controls the refrigeration system 31 to alarm and shut down.

[0120] At the same time, in the stage of operation of the oil-free bearing liquid supply air conditioning system: S33, S34 and S35 in Figure 9, when the first liquid level sensor 17 collects the value L con Greater than the minimum allowable liquid level L of the condenser 19 cmin , that is, satisfying L con >L cmin , the controller 100 controls the refrigeration system 31 to perform no action. At this time, the liquid level of the condenser 19 is sufficient, and can continue to provide sufficient refrigerant liquid to the first liquid supply bag 13, keeping the opening of the first electric regulating valve 37 unchanged.

[0121] When the first liquid level sensor 17 collects the value L con Less than or equal to the minimum allowable liquid level L of the condenser 19 cmin , that is, it does not satisfy L con >L cmin At this time, the liquid level in the condenser 19 is low, and the refrigerant liquid in the first liquid supply bag 13 cannot be replenished in time. The controller 100 adjusts the opening of the first electric regulating valve 37, and reduces the opening of the first electric regulating valve 37, so that the amount of liquid supplied from the condenser 19 to the economizer 23 becomes less, thereby restoring the liquid level in the condenser 19 to a higher level.

[0122] As shown in S30, S31 and S32 in Figure 9, when the refrigeration system monitors the refrigerant liquid subcooling T under P3 and T3, sub Greater than the minimum allowable subcooling T of the bearing supply liquid min When T sub >T min , the controller 100 controls the refrigeration system 31 to not perform any action, which can ensure that the bearing lubricating liquid is in a supercooled state. It is a pure supercooled pure liquid with almost no gas. At this time, the refrigeration system is normal and does not take any action.

[0123] When the system monitors the refrigerant liquid subcooling T under P3 and T3 sub Less than or equal to the minimum allowable subcooling degree T of the bearing supply liquid min When T sub >T min , it cannot be guaranteed that the bearing lubricating liquid is in a supercooled state. At this time, the controller 100 adjusts the electronic expansion valve 36 to increase its opening, so that the supercooling degree of the bearing lubricating liquid is adjusted to meet the bearing lubricating liquid supply requirements.

[0124] The operation process of the above-mentioned compressor is as follows: the refrigerant liquid in the evaporator 29 undergoes an evaporation phase change, and the refrigerant gas generated by the phase change will be transported to the path 101 along the second exhaust path 102. At the suction port of the compressor 42, the refrigerant gas is continuously sucked in 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 will be discharged from the exhaust port of the second-stage impeller 2 and enter the condenser 19 along the first exhaust path 119 to undergo a condensation phase change. The refrigerant liquid generated by the condensation phase change will enter the economizer 23 after passing through the first electric regulating valve 37 and the first throttle orifice plate 21 along the refrigerant supply path 106. The refrigerant gas formed by the flash of the refrigerant liquid in the economizer 23 will enter the compressor along the air supply path 109 for air replenishment, and the remaining liquid in the economizer 23 will enter the evaporator 29 along the return liquid path 107 through the third electric regulating valve 24 and the second throttle orifice plate 25 to complete a cycle process. During this process, the first electric regulating valve 37 can be adjusted accordingly according to the condenser liquid level monitored by the liquid level sensor 17. When the liquid level in the condenser 19 is too low, the opening of the first electric regulating valve 37 can be reduced to reduce the amount of liquid supplied from the condenser 19 to the economizer 23, thereby restoring the liquid level in the condenser 19 to the allowable value.

[0125] In the initial stage of operation of the refrigeration system 31, the pressure difference between the condenser 19 and the evaporator 29 in the refrigeration system 31 is small. At this time, the controller 100 controls the main refrigerant liquid pump 201 to remain in the on state, and the main refrigerant liquid pump 201 continuously pumps refrigerant liquid from the first liquid supply bag 13 containing a large amount of refrigerant liquid. The refrigerant liquid will pass through the main refrigerant liquid pump 201, the pressure regulating valve 10, the second filter 9 and the subcooler 35 along the initial section 120 of the second bearing lubrication supply path to the final section 121 of the second bearing lubrication supply path, and then be divided into a bearing lubrication supply branch path 111 and a bearing lubrication supply branch path 112 to lubricate the left and right bearings 3 in the compressor. The lubricated refrigerant will return to the evaporator 29 along the bearing lubrication return path 118 through the fourth pressure sensor 30 and the second solenoid valve 12 respectively. The function of the pressure regulating valve 10 is to adjust the pressure difference between the liquid pumped by the main refrigeration liquid pump 201 and the bearing liquid supply so that it is not less than the set minimum pressure difference of the bearing liquid supply, ensuring that the pressure difference fluctuation caused by the forced liquid supply opening or closing of the main refrigeration liquid pump 201 will not be too large, thereby reducing the impact on the operation of the refrigeration system.

[0126] 3) Normal shutdown of the refrigeration system:

[0127] As shown in Figures 8 and 10, a certain time before the refrigeration system 31 shuts down, the controller 100 turns on the main refrigerant liquid pump 201, which forces the liquid to be supplied. At this time, the pressure regulating valve 10 is adjusted to adjust the pressure difference between the liquid pumped by the main refrigerant liquid pump 201 and the bearing supply liquid pressure to be no less than the set minimum bearing supply pressure difference. This ensures that the pressure difference fluctuation caused by the forced liquid supply of the main refrigerant liquid pump 201 when it is turned on or off is not too large, reducing the impact on the operation of the refrigeration system. This state ensures that the bearings 3 in the compressor continue to receive sufficient refrigerant liquid lubrication.

[0128] As shown in M1, M2, M3, M7, M8 and M9 in FIG10 , after the refrigeration system 31 is shut down, due to the reduction in the suction volume of the compressor 42, there is still a large refrigeration system pressure difference ΔP in the entire 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, and the main refrigeration liquid pump 201 is forced to supply liquid lubrication to the bearing 3 from the first liquid supply bag 13 until the compressor is powered off for the third set time T. s3 Then, the main refrigerant liquid pump 201 is turned off. Simultaneously with this, the first solenoid valve 33 is opened, allowing the connecting pipe path 103 at the bottom of the condenser 19 to be connected to the evaporator 29. This ensures that after the refrigeration system is shut down, the refrigerant liquid level in the two devices is evenly distributed, and the bearing liquid supply sac 13 at the bottom of the condenser 19 is also filled with refrigerant liquid, accumulating sufficient refrigerant liquid for bearing lubrication when the system is started up next time.

[0129] As shown in M9, M10, M11 and M12 in FIG10 , when the controller 100 detects that the main refrigerant liquid pump 201 in the refrigeration system 31 is originally in the off state, the main refrigerant liquid pump 201 is turned on. After the main refrigerant liquid pump 201 is running, the bearing supply pressure difference ΔP brg Less than or equal to the minimum allowable pressure difference ΔP of the bearing fluid supply min , or the bearing supply pressure difference ΔP brg Greater than the minimum allowable pressure difference ΔP of the bearing fluid supply min , and the duration is less than or equal to the first set time T s1 In the case of ΔP brg >ΔP min , and duration>T s1 , the controller 100 determines that the operating state of the main refrigerant liquid pump 201 is poor, and switches to use the backup refrigerant liquid pump 202. brg >ΔP min , and duration>T s1 , no action is performed.

[0130] As shown in Figure 10, M11, M13 and M14, if the bearing pressure difference ΔP is satisfied brg Greater than the minimum allowable pressure difference ΔP of the bearing fluid supply min , and the duration is greater than the first set time T s1 When ΔP is satisfied brg >ΔP min , and duration>T s1 , the controller 100 determines that the operating state of the standby refrigerant liquid pump 202 is good and that the bearings of the compressor 42 can be normally supplied with liquid through the second bearing lubrication liquid supply path 126, and no action is performed; if the bearing supply pressure difference ΔP is not satisfied brg Greater than the minimum allowable pressure difference ΔP of the bearing fluid supply min , and the duration is greater than the first set time T s1 In the case of ΔP brg >ΔP min , and duration>T s1 If the controller 100 determines that the operating status of the standby refrigeration liquid pump 202 is poor, an alarm is issued to prompt the user to check the bearing lubrication supply path.

[0131] Finally, the refrigeration system 31 is shut down safely.

[0132] 4) Abnormal shutdown of the refrigeration system (such as abnormal power outage):

[0133] As shown in Figures 8 and 10, when the refrigeration system 31 encounters a sudden power outage and stops, the main refrigeration liquid pump 201 cannot be used at this time, but the exhaust check valve 16 prevents the high-pressure gas in the condenser 19 from flowing back into the compressor. Therefore, the refrigeration system pressure difference ΔP between the condenser 19 and the evaporator 29 is still maintained at a relatively large value. At this time, the refrigeration system pressure difference still existing in the system is used for emergency bearing liquid supply. The refrigerant liquid will flow from the first liquid supply liquid bag 13 below the condenser 19 along the initial path 120 of the first bearing lubrication liquid supply path through the first filter, the first one-way valve 11, the pressure regulating valve 10, the second filter 9 and the subcooler 35 to the final path 121 of the first bearing lubrication liquid supply path, and then be divided into two paths, namely 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.

[0134] As shown in M4, M6, and M8 in Figure 10, due to power outage and system circulation cessation, the controller 100 closes the second solenoid valve 12 on the bearing return liquid or return air path 118. The high pressure of the condenser 19 and the low pressure of the evaporator 29 will gradually balance through the pipeline connection. That is, the process of supplying liquid to the bearing 3 based solely on the refrigeration system pressure difference ΔP can last for about 15-20 seconds. However, the motor rotor in the permanent magnet motor can generally stop completely within 5-10 seconds. Therefore, in the case of using permanent magnet motors, this method of emergency liquid supply and bearing lubrication is still reliable and effective.

[0135] As shown in M4, M5 and M8 in Figure 10, if the refrigeration system pressure difference ΔP between the condenser 19 and the evaporator 29 is very small in the original non-stop operation state, that is, the refrigeration system pressure difference ΔP is less than the bearing pressure difference ΔP brg At this time, there is a sudden power outage and the bearing cannot be supplied with liquid by relying solely on the refrigeration system pressure difference ΔP. At this time, the controller 100 controls the refrigeration liquid pump in the refrigeration system 31, preferably using a UPS power supply, and the main refrigeration liquid pump 201 can start running, so that it can continuously pump liquid from the first liquid supply bag 13 to the bearing 3 in the compressor. As the high and low pressures gradually balance, the refrigerant liquid gradually accumulated in the evaporator 29 can also continuously replenish the first liquid supply bag 13 with refrigerant liquid through the connecting pipe 103, so that the main refrigeration liquid pump 201 can always pump sufficient liquid for the bearing 3 to lubricate it. This process continues until the rotor completely stops.

[0136] Finally, the refrigeration system 31 stops operating.

[0137] During the shutdown process, the second solenoid valve 12 will switch from the original normally open state to the closed state, so that the bearing lubrication return liquid or return air path 118 will be closed and cut off, thereby ensuring that a certain amount of refrigerant liquid can still be present in the bearing cavity of the bearing 3 in the compressor within a certain period of time, thereby improving the safety and reliability of the bearing operation after shutdown.

[0138] In some embodiments, as shown in S30, S31, S32, S33, S34, and S35 in FIG9 and FIG10 , during all stages of the refrigeration system operation, the controller 100 controls the refrigeration system 31 to constantly detect the state parameters of the refrigerant liquid for lubricating the bearings:

[0139] When the first liquid level sensor 17 collects the value L con Greater than the minimum allowable liquid level L of the condenser 19 cmin , that is, satisfying L con >L cmin, the controller 100 controls the refrigeration system 31 to perform no action. At this time, the liquid level of the condenser 19 is sufficient, and can continue to provide sufficient refrigerant liquid to the first liquid supply bag 13, keeping the opening of the first electric regulating valve 37 unchanged.

[0140] When the first liquid level sensor 17 collects the value L con Less than or equal to the minimum allowable liquid level L of the condenser 19 cmin , that is, it does not satisfy L con >L cmin At this time, the liquid level in the condenser 19 is low, and the refrigerant liquid in the first liquid supply bag 13 cannot be replenished in time. The controller 100 adjusts the opening of the first electric regulating valve 37, and reduces the opening of the first electric regulating valve 37, so that the amount of liquid supplied from the condenser 19 to the economizer 23 becomes less, thereby restoring the liquid level in the condenser 19 to a higher level.

[0141] When the refrigeration system monitors the refrigerant liquid subcooling T under P3 and T3 sub Greater than the minimum allowable subcooling T of the bearing supply liquid min When T sub >T min , the controller 100 controls the refrigeration system 31 to not perform any action, which can ensure that the bearing lubricating liquid is in a supercooled state, which is a pure supercooled pure liquid with almost no gas. At this time, the refrigeration system 31 is normal and does not take any action.

[0142] When the system monitors the refrigerant liquid subcooling T under P3 and T3 sub Less than or equal to the minimum allowable subcooling degree T of the bearing supply liquid min When T sub >T min , it cannot be guaranteed that the bearing lubricating liquid is in a supercooled state. At this time, the controller 100 adjusts the electronic expansion valve 36 so that the supercooling degree of the bearing lubricating liquid is adjusted to meet the bearing lubricating liquid supply requirements.

[0143] This application uses two different bearing lubrication liquid supply paths to achieve stable and reliable bearing liquid supply at all stages. Corresponding pipeline connections and power devices (pumps) are set in the system. According to the operating status of the refrigeration system obtained by judgment, different liquid sources are selected in the refrigeration system, and different refrigerant liquid supply paths are selected for bearing lubrication liquid supply; and the liquid supply path switching method adopted ensures that the bearings in the compressor can obtain sufficient refrigerant liquid for lubrication at each stage, thereby ensuring the safety of system operation.

[0144] For ease of explanation, the above description has been made in conjunction with specific embodiments. However, the above discussion of some embodiments is not intended to be exhaustive or to limit the embodiments to the specific forms disclosed above. Based on the above teachings, various modifications and variations can be obtained. The selection and description of the above embodiments are intended to better explain the principles and practical applications, so that those skilled in the art can better use the embodiments and various different variations of the embodiments suitable for specific use considerations.

Claims

1. An oil-free bearing liquid supply air conditioning system, comprising: A box system, comprising a compressor, a condenser, an evaporator, an economizer and a refrigeration liquid pump; A refrigeration system, the refrigeration system comprising: a first bearing lubricating liquid supply path from the condenser to the compressor; a second bearing lubricating liquid supply path from the condenser to the compressor; the second bearing lubricating liquid supply path being provided with at least two refrigeration liquid pumps, the at least two refrigeration liquid pumps being arranged in parallel; the at least two refrigeration liquid pumps comprising a main refrigeration liquid pump and at least one backup refrigeration liquid pump; The controller is configured as: During the startup phase, the main refrigeration liquid pump is turned on; During a stable operation phase, if the pressure difference of the refrigeration system is greater than the sum of the minimum allowable bearing supply pressure difference and the upward offset value of the bearing supply pressure difference, and the duration is greater than a first set time, the main refrigerant liquid pump is turned off; and the bearing of the compressor is supplied with liquid through the first bearing lubrication liquid supply path; In the stable operation stage, if the pressure difference of the refrigeration system is less than or equal to the sum of the minimum pressure difference of the bearing supply fluid and the upward bias value of the bearing supply fluid differential, or the pressure difference of the refrigeration system is greater than the sum of the minimum allowable pressure difference of the bearing supply fluid and the upward bias value of the bearing supply fluid differential, and the duration is less than or equal to the first set time, the main refrigeration liquid pump is maintained on; and the second bearing lubrication supply fluid path is used to supply fluid to the bearings of the compressor.

2. The oil-free bearing liquid supply air conditioning system according to claim 1, wherein: The first bearing lubrication fluid supply path includes an initial path, a front path, a rear path and a terminal path which are connected in sequence; The second bearing lubrication fluid supply path includes an initial path, a front path, a rear path and a terminal path that are sequentially connected; The front section path of the first bearing lubrication liquid supply path and the front section path of the second bearing lubrication liquid supply path are arranged in parallel, and the rear section path of the first bearing lubrication liquid supply path and the rear section path of the second bearing lubrication liquid supply path are the same path; the initial section path of the first bearing lubrication liquid supply path and the initial section path of the second bearing lubrication liquid supply path are the same path, and both are connected to the condenser; the final section path of the first bearing lubrication liquid supply path and the final section path of the second bearing lubrication liquid supply path are the same path, and both are connected to the compressor.

3. The oil-free bearing liquid supply air conditioning system according to claim 2, wherein: The controller is further configured to: During the stable operation stage, and when the main refrigeration liquid pump is turned off and the first bearing lubrication liquid supply path is used to supply liquid to the bearings of the compressor, if the bearing supply pressure differential is less than the minimum allowable pressure differential of the bearing supply, and the bearing supply pressure differential is greater than or equal to the difference between the minimum allowable pressure differential of the bearing supply and the downward offset value of the bearing supply pressure differential, or if the bearing supply pressure differential is less than the difference between the minimum allowable pressure differential of the bearing supply and the downward offset value of the bearing supply pressure differential and the duration is less than a second set time, the refrigeration system is controlled to alarm and prompt a check of the bearing lubrication liquid supply path.

4. The oil-free bearing liquid supply air conditioning system according to claim 2, wherein: The controller is further configured to: During the stable operation stage, and when the main refrigerant liquid pump is turned off and the bearings of the compressor are supplied with liquid through the first bearing lubrication supply path, if the bearing supply pressure differential is less than the difference between the minimum allowable bearing supply pressure differential and the downward offset value of the bearing supply pressure differential, and the duration is greater than the second set time, the refrigeration system is controlled to alarm and 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 the difference between the pressure value of the condenser and the pressure value of the evaporator, and the minimum pressure difference of the bearing fluid supply is the difference between the preset pressure value of the bearing fluid supply and the minimum allowable pressure value of the bearing lubrication return liquid or return air.

6. The oil-free bearing liquid supply air conditioning system according to claim 2, further comprising: a bearing lubrication return liquid 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 of the first bearing lubricating fluid supply path and configured to collect a pressure value of the bearing lubricating fluid supply; The fourth pressure sensor is connected to the bearing lubricating liquid return or air return path and is configured to collect the pressure value of the bearing lubricating liquid return or air return.

7. The oil-free bearing liquid supply air conditioning system according to claim 1, wherein: The controller is further configured to: In the stable operation stage, if the pressure difference of the refrigeration system is less than the difference between the minimum allowable pressure difference of the bearing supply liquid and the downward offset value of the bearing supply liquid difference, and the duration is greater than the first set time, the main refrigerant liquid pump is turned on; and the bearing of the compressor is supplied with liquid through the second bearing lubrication liquid supply path; During the period when the main refrigerant liquid pump is turned on and the bearings of the compressor are supplied with liquid through the second bearing lubrication liquid supply path, if the bearing supply pressure differential is less than the minimum allowable pressure differential of the bearing supply liquid, and the bearing supply pressure differential is greater than or equal to the difference between the minimum allowable pressure differential of the bearing supply liquid and the downward offset value of the bearing supply pressure differential, or if the bearing supply pressure differential is less than the difference between the minimum allowable pressure differential of the bearing supply liquid and the downward offset value of the bearing supply pressure differential and the duration is less than a second set time, the refrigeration system is controlled to alarm and prompt a prompt to check the bearing lubrication liquid supply path; When the bearing fluid supply differential pressure is less than the difference between the minimum allowable bearing fluid supply differential pressure and the downward offset value of the bearing fluid supply differential pressure, and the duration is greater than the second set time, controlling the refrigeration system to alarm and shut down; The bearing supply fluid pressure difference is the difference between the bearing supply fluid pressure value and the bearing lubrication return fluid or return air pressure value measured in real time.

8. The oil-free bearing liquid supply air conditioning system according to claim 1, further comprising: A communication line is provided between the condenser and the evaporator, the communication line comprising a first solenoid valve configured to control the opening and closing of the communication line; a second solenoid valve provided on the bearing lubrication return liquid or air return path; During the startup phase: Before the refrigeration system is started, the first solenoid valve is in an open state; The controller is further configured to: During startup of the refrigeration system, the main refrigeration liquid pump is turned on and the first solenoid valve is closed; when the bearing supply pressure differential is greater than the minimum allowable bearing supply pressure differential and the duration is greater than the first set time, the compressor is operated; and the bearings of the compressor are supplied with liquid through the second bearing lubrication supply path; The shutdown phase includes the normal power-off shutdown phase and the abnormal power-off shutdown phase; The controller is further configured to: During the normal power outage shutdown phase: When the main refrigerant liquid pump is in an on state, after the compressor is powered off for a third set time, the main refrigerant liquid pump is turned off and the first solenoid valve is opened; When the main refrigerant liquid pump is in an off state, forcibly opening the main refrigerant liquid pump; after the compressor is powered off for a third preset time, closing the main refrigerant liquid pump and opening the first solenoid valve; During the abnormal power outage and 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: During the period when the main refrigerant liquid pump is turned on and the second bearing lubrication liquid supply path is used to supply liquid to the bearings of the compressor, if the bearing supply pressure differential is less than or equal to the minimum allowable bearing supply pressure differential, or if the bearing supply pressure differential is greater than the minimum allowable bearing supply pressure differential and the duration is less than or equal to the first set time, the backup refrigerant liquid pump is turned on; During the period when the standby refrigerant liquid pump is turned on and the bearings of the compressor are supplied with liquid through the second bearing lubrication supply path; if the bearing supply pressure differential is less than or equal to the minimum allowable bearing supply pressure differential, or the bearing supply pressure differential is greater than the minimum allowable bearing supply pressure differential, and the duration is less than or equal to the first set time, the refrigeration system is controlled to alarm and prompt to check the bearing lubrication supply path.

10. The oil-free bearing liquid supply air conditioning system according to claim 1, further comprising: a refrigerant liquid supply path from the condenser to the economizer, the refrigerant liquid supply path comprising a first electric regulating valve; a first liquid level sensor configured to monitor a liquid level in the condenser; The controller is further configured to: When the value collected by the first liquid level sensor is greater than the minimum allowable liquid level of the condenser, maintaining the opening of the first electric regulating valve; When the value collected by the first liquid level sensor is less than or equal to the minimum allowable liquid level of the condenser, the opening of the first electric regulating valve is adjusted to reduce the opening of the first electric regulating valve.

11. The oil-free bearing liquid supply air conditioning system according to claim 1, further comprising: a supercooler, the supercooler being connected to the rear section of the first bearing lubricating fluid supply path and the end section of the first bearing lubricating fluid supply path; A heat exchange path from the condenser to the subcooler; the heat exchange path includes an electronic expansion valve; a first temperature sensor configured to monitor a temperature of a final section of the first bearing lubrication supply path; The controller is further configured to: When the subcooling degree of the refrigerant liquid is greater than the minimum allowable subcooling degree of the bearing supply liquid, controlling the refrigeration system to not perform any action; When the subcooling degree of the refrigerant liquid is less than or equal to the minimum allowable subcooling degree of the bearing supply liquid, adjusting the electronic expansion valve to increase the opening degree of the electronic expansion valve; The refrigerant liquid subcooling degree is calculated based on the measured pressure value and temperature of the bearing supply liquid, and the minimum allowable subcooling degree of the bearing supply liquid is a preset value.

12. The oil-free bearing liquid supply air conditioning system according to claim 1, wherein: The minimum allowable pressure difference of the bearing fluid supply is in the range of 0.05 MPa to 0.35 MPa; The upward offset value range of the bearing hydraulic pressure difference is 0 MPa to 0.35 MPa; The downward bias value range of the bearing hydraulic pressure difference is 0 MPa to 0.35 MPa; The minimum permissible liquid level of the condenser is 30% of the volume of the condenser; The first set time is 1 minute; The second setting time is 30s; The third setting time is 3 minutes.

13. A control method for an oil-free bearing liquid supply air conditioning system, applied to the oil-free bearing liquid supply air conditioning system, the oil-free bearing liquid supply air conditioning system comprising: A box system, comprising: a compressor, a condenser, an evaporator, an economizer and a refrigeration liquid pump; A refrigeration system, comprising: a first bearing lubricating liquid supply path from the condenser to the compressor; a second bearing lubricating liquid supply path from the condenser to the compressor; the second bearing lubricating liquid supply path is provided with at least two refrigeration liquid pumps, the at least two refrigeration liquid pumps are arranged in parallel; the at least The two refrigeration liquid pumps include a main refrigeration liquid pump and at least one backup refrigeration liquid pump; The control method includes: During the startup phase, the main refrigeration liquid pump is turned on; During a stable operation phase, if the pressure difference of the refrigeration system is greater than the sum of the minimum allowable bearing supply pressure difference and the upward offset value of the bearing supply pressure difference, and the duration is greater than a first set time, the main refrigerant liquid pump is turned off; and the bearing of the compressor is supplied with liquid through the first bearing lubrication liquid supply path; In the stable operation stage, if the pressure difference of the refrigeration system is less than or equal to the sum of the minimum pressure difference of the bearing supply fluid and the upward bias value of the bearing supply fluid differential, or the pressure difference of the refrigeration system is greater than the sum of the minimum allowable pressure difference of the bearing supply fluid and the upward bias value of the bearing supply fluid differential, and the duration is less than or equal to the first set time, the main refrigeration liquid pump is maintained on; and the second bearing lubrication supply fluid path is used to supply fluid to the bearings of the compressor.

14. The control method of the oil-free bearing liquid supply air conditioning system according to claim 13, further comprising: The first bearing lubrication fluid supply path includes an initial path, a front path, a rear path and a terminal path which are connected in sequence; The second bearing lubrication fluid supply path includes an initial path, a front path, a rear path and a terminal path that are sequentially connected; The front section path of the first bearing lubrication liquid supply path and the front section path of the second bearing lubrication liquid supply path are arranged in parallel, and the rear section path of the first bearing lubrication liquid supply path and the rear section path of the second bearing lubrication liquid supply path are the same path; the initial section path of the first bearing lubrication liquid supply path and the initial section path of the second bearing lubrication liquid supply path are the same path, and both are connected to the condenser; the final section path of the first bearing lubrication liquid supply path and the final section path of the second bearing lubrication liquid supply path are the same path, and both are connected to the compressor.

15. The control method of the oil-free bearing liquid supply air conditioning system according to claim 14, further comprising: During the stable operation stage, and when the main refrigeration liquid pump is turned off and the first bearing lubrication liquid supply path is used to supply liquid to the bearings of the compressor, if the bearing supply pressure differential is less than the minimum allowable pressure differential of the bearing supply, and the bearing supply pressure differential is greater than or equal to the difference between the minimum allowable pressure differential of the bearing supply and the downward offset value of the bearing supply pressure differential, or if the bearing supply pressure differential is less than the difference between the minimum allowable pressure differential of the bearing supply and the downward offset value of the bearing supply pressure differential and the duration is less than a second set time, the refrigeration system is controlled to alarm and prompt a check of the bearing lubrication liquid supply path.

16. The control method of the oil-free bearing liquid supply air conditioning system according to claim 14, further comprising: During the stable operation stage, and when the main refrigerant liquid pump is turned off and the bearings of the compressor are supplied with liquid through the first bearing lubrication supply path, if the bearing supply pressure differential is less than the difference between the minimum allowable bearing supply pressure differential and the downward offset value of the bearing supply pressure differential, and the duration is greater than the second set time, the refrigeration system is controlled to alarm and shut down.

17. The control method of the oil-free bearing liquid supply air conditioning system according to claim 13, further comprising: The pressure difference of the refrigeration system is the difference between the pressure value of the condenser and the pressure value of the evaporator, and the minimum pressure difference of the bearing fluid supply is the difference between the preset pressure value of the bearing fluid supply and the minimum allowable pressure value of the bearing lubrication return liquid or return air.

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