WO2024093435A1

WO2024093435A1 - Oil-free bearing liquid supply air-conditioning system and control method therefor

Info

Publication number: WO2024093435A1
Application number: PCT/CN2023/112986
Authority: WO
Inventors: 曹成林; 冯旭; 丛辉; 陈见兴; 赵鹏飞; 马振; 程振军
Original assignee: 青岛海信日立空调系统有限公司
Priority date: 2022-11-02
Filing date: 2023-08-14
Publication date: 2024-05-10

Abstract

An oil-free bearing liquid supply air-conditioning system (1000) and a control method therefor. The system (1000) comprises: a box system (200), which comprises a compressor (42), a condenser (19), an evaporator (29), an economizer (23), and refrigeration liquid pumps (20); and a refrigeration system (31), which comprises a first bearing lubrication liquid supply path (125) from the condenser (19) to the compressor (42), and a second bearing lubrication liquid supply path (126) from the condenser (19) to the compressor (42), wherein at least two refrigeration liquid pumps (20) are arranged in the second bearing lubrication liquid supply path (126), the at least two refrigeration liquid pumps (20) are arranged in parallel, and the at least two refrigeration liquid pumps (20) include 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

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

The present application relates to the technical field of air conditioning, and in particular to an oil-free bearing liquid supply air conditioning system and a control method thereof.

Background technique

At present, compressors are the main type of air conditioners, and oil lubrication of bearings is dominant in centrifugal chillers. However, due to the presence of lubricating oil, the oil lubrication system and oil separation system of oil supply and return must be considered during the design of the chiller, which increases the complexity of design, manufacturing, maintenance and control, and greatly increases the initial cost and operation and maintenance cost. 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.

Summary of the invention

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 in the 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 offset value of the bearing fluid supply differential, 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 fluid through the first bearing lubrication fluid 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 offset value of the bearing fluid supply differential, 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 offset value of the bearing fluid supply differential, 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 fluid through the second bearing lubrication fluid supply path.

In a 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 comprises: a box system, wherein the box system comprises: a compressor, a condenser, an evaporator, an economizer and a refrigeration liquid pump; a refrigeration system, wherein the refrigeration system comprises: 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 comprise a main refrigeration liquid pump and at least one standby refrigeration liquid pump; the control method comprises: in a startup phase, turning on the main refrigeration liquid pump; in the stabilization phase, In the fixed operation stage, if the pressure difference in the refrigeration system is greater than the sum of the minimum allowable pressure difference for bearing fluid supply and the upward bias value of the bearing fluid supply differential, 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 fluid through the first bearing lubrication fluid supply path; in the stable operation stage, if the pressure difference in the refrigeration system is less than or equal to the sum of the minimum pressure difference for bearing fluid supply and the upward bias value of the bearing fluid supply differential, or the pressure difference in the refrigeration system is greater than the sum of the minimum allowable pressure difference for bearing fluid supply and the upward bias value of the bearing fluid supply differential, 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 fluid through the second bearing lubrication fluid supply path.

BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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;

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

FIG7 is a partial path structure diagram of a refrigeration system provided in some embodiments of the present application;

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

FIG9 is a flow chart of a stable startup of a refrigeration system provided by some embodiments of the present application;

FIG. 10 is a flowchart of a refrigeration system shutdown and power-off process provided in some embodiments of the present application.

Detailed ways

Some embodiments of the present disclosure will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments provided by the present disclosure are within the scope of protection of the present disclosure.

Unless the context requires otherwise, throughout the specification and claims, the term "comprise" and other forms thereof, such as the third person singular form "comprises" and the present participle form "comprising", are to be interpreted as open, 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" and the like are intended to indicate that specific 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 specific features, structures, materials or characteristics described may be included in any one or more embodiments or examples in any appropriate manner.

In the following, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, 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.

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.

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

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

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.

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 cost. 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.

Oil-lubricated bearing centrifuges account for about 82% of the current central air-conditioning centrifugal unit market. However, since lubricating oil is needed to lubricate the bearings in the system, the oil lubrication system and oil separation system of the oil supply and return must be considered during the design of the chiller, which increases the complexity of design, manufacturing, maintenance and control, and greatly increases the initial cost and operating 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 the unit performance to deteriorate after long-term operation.

In view of the corresponding disadvantages 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 structure of the system, which has received more attention in the HVAC industry.

There are currently three main development directions for oil-free centrifuges. One is the oil-free centrifuge unit using magnetic bearings. Magnetic bearings have many sensors and complex control systems, and cannot completely solve the reliability problem of the unit in the event of a sudden power outage.

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 the reliability is poor when the load changes suddenly.

The third is the use of refrigerant liquid lubricated ceramic bearing oil-free centrifugal units, which use refrigerant as a lubricating medium to lubricate the ceramic bearings in the system. On the one hand, its control system is simple, which simplifies the system design. On the other hand, the ceramic bearings have strong impact resistance, which can realize the development of large-capacity oil-free centrifuges. Based on the advantages of the last development direction of oil-free centrifuges, refrigerant-lubricated rolling ceramic bearings are increasingly being studied and applied in centrifugal units.

Ceramic bearing oil-free centrifugal units use refrigerant as bearing lubricating medium. Unlike high-viscosity lubricating oil as bearing lubricating medium, refrigerant viscosity is extremely low. Taking R134a refrigerant as an example, its value at 25°C is 0.162cst, which is about 1/100 of the viscosity of lubricating oil. When the refrigerant supply is interrupted, the low-viscosity refrigerant liquid is difficult to remain on the bearing surface. Even if a part of the refrigerant remains on the bearing surface, it will evaporate due to the volatile nature of the refrigerant. In addition, when the refrigerant liquid is transported to the bearing in the compressor, due to the resistance along the way and local resistance during the transportation process, the refrigerant liquid is prone to throttling flash phenomenon, and then produces refrigerant gas. When the refrigerant gas enters the bearing for bearing lubrication, it is easy to cause serious wear of the rolling elements in the bearing, which seriously affects the life of the bearing and the stability of the compressor operation. In summary, when the refrigerant is used as the medium for bearing lubrication, the unit needs to ensure the continuity and stability of the refrigerant liquid supply during the startup stage, operation stage, and shutdown stage to ensure the lubrication state of the bearing in the compressor.

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 at 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.

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.

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

The refrigeration system 31 comprises:

The compressor 42 is the core of the refrigeration system and 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 increasing its pressure after being expanded by the diffuser, thereby providing power for the refrigeration cycle.

The economizer 23 is configured to expand the liquid refrigerant in a high-pressure state into a gas-liquid two-phase refrigerant in a medium-pressure state. In some embodiments, the economizer 23 is a tank container arranged in the system, and has a corresponding structural design inside. After the refrigerant liquid enters the economizer, flash occurs, and the flash produces a part of the refrigerant gas working medium. This part of the gas working medium will enter the compressor 42 along the air supply pipeline to replenish the compressor 42, and the remaining refrigerant gas-liquid two-phase refrigerant will flow out of the economizer 23.

The 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 and low-pressure gas-phase refrigerant, and the low-temperature and low-pressure gas-phase refrigerant is returned to the compressor 42. The evaporator includes a heating chamber and an evaporation chamber. The heating chamber is configured to provide the liquid with the heat required for evaporation, so as to promote the boiling and vaporization of the liquid; the evaporation chamber is configured to completely separate the gas-liquid two-phase.

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 the heat is released to the surrounding environment during the condensation process.

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

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 of the system at a sufficient flow rate from a lower position of the system.

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 paths connected in parallel, and at least a portion of paths shared. The second bearing lubricating liquid supply path of the compressor 42 further includes a refrigeration liquid pump 20; the 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 connection with the refrigeration system 31, and the controller 100 is configured to control the refrigeration system 31.

In the embodiment shown in the present application, the controller 100 refers to a device that can generate an operation control signal according to the instruction operation code and the timing signal to instruct the refrigeration system to execute the control instruction. Exemplarily, 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 act.

In addition, the controller 100 is configured to control the operation of various components inside 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.

The pump is a component that conveys fluid or pressurizes fluid, and it transfers the mechanical energy of the prime mover or other external energy to the liquid to increase the liquid energy. The refrigeration liquid pump is used to forcibly extract the refrigerant liquid to supply the compressor 42 via the second bearing lubrication liquid supply path 126 .

It should be noted that, for example, 11 to 12 appearing in the drawings of the present 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.

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

The motor 4 is a prime mover of the compressor 42 and is configured to provide power for the operation of the compressor 42. Through the power supply, the stator structure wound by the coil etc. in the motor 4 can generate a magnetic field, and under the action of the magnetic field, the rotor structure in the motor 4 will rotate and provide driving force for the rotating parts in the compressor 42;

The bearing 3 is located on the motor 4 and is configured to provide support for the rotor in the motor 4, reduce the friction coefficient during the rotation of the rotor, and ensure the rotation accuracy of the rotor;

The impellers (such as the first-stage impeller 1 and the second-stage impeller 2), the double impellers adopt a "back-to-back" impeller arrangement. Through such an impeller arrangement, the axial loads generated in the two or more stages of impellers offset each other, thereby balancing the axial loads.

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 .

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 which 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 the gas.

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

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 balls and are lighter in weight, which can reduce the friction caused by centrifugal force during rotation and extend the life of the bearing.

In some embodiments, the subcooler may be a plate heat exchanger. The plate heat exchanger has high heat exchange efficiency and can achieve a large heat exchange with a small heat exchange temperature difference, thereby effectively improving the subcooling degree of the refrigerant liquid; in addition, the plate heat exchanger occupies a small volume, occupies less space in the unit system, and the layout design is easy to implement.

The above 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 by 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 supercooler 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 supercooler 35 is configured to further condense the refrigerant liquid, so as to better lubricate the bearings of the compressor 42.

As shown in Figures 1 and 3, the first bearing lubrication supply path and the second bearing lubrication 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 supply path and the front path 105 of the second bearing lubrication supply path are arranged in parallel; the initial path 120 of the first bearing lubrication supply path and the initial path 120 of the second bearing lubrication supply path are the same path; the rear path 110 of the first bearing lubrication supply path and the rear path 110 of the second bearing lubrication supply path are the same path; the final path 121 of the first bearing lubrication supply path and the final path 121 of the second bearing lubrication supply path are the same path.

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 are combined into one in the initial section, the rear section and the terminal section, and both transmit the refrigerant liquid to the bearing in the compressor through the terminal section 121. This arrangement reduces the piping arrangement in the unit system on the one hand, and realizes the merging and simplification of the first bearing lubrication supply path and the second bearing lubrication supply path by using a common piping section; on the other hand, it improves the maintainability of the unit system piping, and when the unit system piping fails, there is no need to tediously inspect multiple sections of piping.

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.

It should be noted that the refrigeration system includes multiple flow paths, such as a liquid flow path and a gas flow path. The flow path includes 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 flow.

As shown in Fig. 3, during the circulation of the refrigerant liquid in the first bearing lubrication supply path, the refrigerant liquid sequentially passes through the first filter 34, the first check valve 11, the pressure regulating valve 10, the second filter 9 and the supercooler 35. During the circulation of the refrigerant liquid in the second bearing lubrication supply path, the refrigerant liquid sequentially passes through the first filter 34, the refrigerant liquid pump 20, the pressure regulating valve 10, the second filter 9 and the supercooler 35.

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, in the refrigerant liquid in the initial path 120 of the first bearing lubrication fluid supply path; the first one-way valve 11 The second filter 9 is configured to prevent the refrigerant liquid in the front section path 104 of the first bearing lubricating liquid supply path from flowing backwards; the second filter 9 is configured to filter a small amount of impurities, such as solid particles, in the refrigerant liquid in the rear section path 110 of the first bearing lubricating liquid supply path; the pressure regulating valve 10 is configured to adjust the pressure in the rear section path 110 of the first bearing lubricating liquid supply path, thereby fixing the pressure. The subcooler 35 is configured to recool the refrigerant liquid in the rear section path 110 of the first bearing lubricating liquid supply path, and then supply the liquid to the bearing of the compressor 42 via the last section path 121 of the first bearing lubricating liquid supply path.

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 standby refrigeration liquid pump 202.

A plurality of 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 are unable to supply liquid to the bearing. When such a situation occurs, the system can quickly switch to the normally operating standby refrigeration liquid pump path to ensure the normal bearing supply.

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

Uninterruptible Power Supply (UPS) is an uninterruptible power supply with an energy storage device. It is mainly used to provide uninterruptible power supply to some equipment that requires high power stability. In this way, even if the air-conditioning system is powered off, the refrigerant liquid pump can work normally under the action of the uninterruptible power supply, pump out the refrigerant liquid, and then keep the bearings in the compressor motor lubricated continuously.

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 disposed bearings 3 in the motor 4 .

FIG. 4 is a partial structural diagram of a liquid supply source provided in some embodiments of the present application; FIG. 5 is a partial structural diagram of another liquid supply source provided in some embodiments of the present application.

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

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 for liquid lubrication of the bearing 3 to ensure that there is little or no gas in the liquid supply liquid and has a good cooling effect.

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.

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 .

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.

In some embodiments, as shown in Figures 6 and 7, the refrigeration system 31 further includes: a bearing lubrication return liquid or return gas 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 return gas path 118 from the compressor 42 to the evaporator 29 includes a second solenoid valve 12, and the second solenoid valve 12 is configured to control the opening and closing of the bearing lubrication return liquid or return gas path 118.

As shown in FIG6 , the refrigeration system 31 further includes: a first pressure sensor 15, a second pressure sensor 26, a third pressure sensor 8, a fourth pressure sensor 30 and a fifth pressure sensor 5; the first pressure sensor 15 is connected to the condenser 19 and 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 last section of the first bearing lubrication supply path and is configured to collect the pressure value of the bearing supply; 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 compressor The exhaust port of 42 is connected and configured to collect the exhaust pressure of the compressor.

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 path 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.

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 replenishment 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 replenishment path 123 from the subcooler 35 to the first air replenishment path 109, or a subcooling return air path from the subcooler 35 to the bearing lubrication return liquid or return air path 118.

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

In some embodiments, as shown in Figure 7, the 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 motor cooling liquid supply path 108 and the refrigerant liquid supply path 106 are both connected to the second liquid supply bag 14.

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.

The second liquid supply capsule 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, and the refrigerant gas enters the compressor 42 along the first gas replenishment path 109 for gas replenishment. At the same time, the second gas replenishment path 123 from the subcooler 35 to the first gas replenishment path 109 enters the compressor 42 via the first gas replenishment path 109 for gas replenishment; and the remaining refrigerant liquid in the economizer 23 enters the evaporator 29 along the liquid return path 107. At the same time, the second liquid supply capsule 14 is also configured to provide refrigerant liquid to the motor in the compressor 42 for motor cooling, and the cooled refrigerant (liquid or gas) returns to the evaporator 29 through the motor cooling return gas path 117.

The first exhaust path 119 from the compressor 42 to the condenser 19 is connected to the condenser 19 from the compressor 42 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 from the stop valve 27 on the evaporator 29 via the suction 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 via the drying filter 18 and the second electric regulating valve 32 in sequence, and the cooling liquid supply path 108 branches at the end into a cooling liquid supply A branch path 113 and a 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 via the first electric regulating valve 37 and the first throttling orifice 21 in sequence; the return liquid path 107 from the economizer 23 to the evaporator 29 is connected to the evaporator 29 from the economizer 23 via the third electric regulating valve 24 and the second throttling orifice 25 in sequence; 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.

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.

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

(1) Refrigeration system startup phase;

(2) Stable operation stage of refrigeration system;

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

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

Among them, the forced liquid supply method of the refrigeration liquid pump is adopted in the stage (1) and the stage (3), while the 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 of the refrigeration liquid pump and the natural liquid supply of the refrigeration system pressure difference are operated in parallel or separately. The 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 then the forced liquid supply method of the refrigeration liquid pump is adopted. The operation process of the whole stage is described in detail below with reference to Figure 8.

Regardless of the stage of the refrigeration system, each sensor device in the refrigeration system is in a 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 _Lcon ; the subcooling degree of the bearing supply liquid is set to _Tsub , which is calculated by the pressure value _P3 of the bearing supply liquid and the temperature _T3 of the bearing supply liquid; the minimum allowable subcooling degree _Tmin of the bearing supply liquid is set, and the value is set according to the actual situation, and can be set to 1°C for example; the operating pressure difference of the refrigeration system is set to ΔP= _P1 - _P2 ; the bearing supply liquid differential is set to _ΔPbrg = _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 fluid supply mode to T _s1 , the value is set according to the actual situation, and can be set to 1min for example; set the upward bias value of the bearing fluid supply differential 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 fluid supply differential 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 , the value is set according to the actual situation, and can be set to 30s for example; set the compressor power-off judgment time to the third set time T _s3 , the 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 , the value is set according to the actual situation, and can be set to 30% for example.

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

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

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

1) Refrigeration system startup phase:

As shown in FIG8 and FIG9, before the entire refrigeration system 31 is started, a large amount of refrigerant liquid will accumulate in the evaporator 29 and the condenser 19 in the refrigeration system. At this time, the first solenoid valve 33 is opened, and the connecting pipe path 103 at the bottom of the condenser 19 and the evaporator 29 is connected, so that the refrigerant liquid level is evenly distributed in the two devices. In addition, since the condenser is arranged lower than the evaporator in the structural arrangement of the unit, it is ensured that the first liquid supply capsule 13 at the bottom of the condenser 19 is filled with refrigerant liquid before the system is started. Since the first liquid supply capsule 13 is located below the condenser 19, under the action of gravity, as long as there is refrigerant liquid in the condenser 19, the refrigerant liquid can be automatically added to the first liquid supply capsule 13.

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.

When the bearing supply fluid differential pressure ΔP _brg is greater than the minimum allowable bearing supply fluid differential pressure ΔP _min and the duration is greater than the first set time T _s1 , that is, ΔP _brg >ΔP _min and the duration >T _s1 is satisfied, the controller 100 controls the compressor 42 to operate; and supplies fluid to the bearings of the compressor 42 via the second bearing lubrication fluid supply path 126 .

The main refrigerant liquid pump 201 will continuously pump refrigerant liquid from the first liquid supply bag 13 containing more refrigerant liquid, and it 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 path 120 of the second bearing lubrication liquid supply path to the final path 121 of the second bearing lubrication liquid supply path, and then be divided into a bearing lubrication liquid supply branch path 111 and a bearing lubrication liquid supply branch path 112 for lubricating the left and right side bearings 3 in the compressor. After the bearings 3 are lubricated, the rotor gradually rotates stably, and the refrigeration system 31 is started, and 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.

As shown in S2 and S5 in Figure 9, when the bearing fluid supply differential pressure ΔP _brg is less than or equal to the minimum allowable bearing fluid supply differential pressure ΔP _min , or when the bearing fluid supply differential pressure ΔP _brg is greater than the minimum allowable bearing fluid supply differential pressure ΔP _min , and the duration is less than or equal to the first set time T _s1 , that is, ΔP _brg >ΔP _min , and the duration >T _s1 is not satisfied, the controller 100 determines that the operating state of the main refrigerant liquid pump 201 is poor, and at this time, the standby refrigerant liquid pump 202 is switched to be used, and the bearings of the compressor 42 are also supplied with fluid through the second bearing lubrication fluid supply path 126.

As shown in S3, S6 and S7 in Figure 9, during the period when the standby refrigerant liquid pump 202 is turned on and the bearings of the compressor 42 are supplied with liquid through the second bearing lubrication liquid supply path 126, if the bearing supply pressure differential ΔP _brg is greater than the minimum allowable pressure differential ΔP _min of the bearing supply and the duration is greater than the first set time T _s1 , that is, ΔP _brg >ΔP _min and the duration >T _s1 are satisfied, the controller 100 determines that the operating state of the standby refrigerant liquid pump 202 is good, and the bearings of the compressor 42 can be normally supplied with liquid through the second bearing lubrication liquid supply path 126, and the compressor 42 continues to operate; if the bearing supply pressure differential ΔP _brg is not greater than the minimum allowable pressure differential ΔP _min of the bearing supply and the duration is greater than the first set time T _s1 , that is, ΔP _brg >ΔP _min and the duration >T _s1 are not satisfied, the controller 100 determines that the operating state of the standby refrigerant liquid pump 202 is poor, and an alarm is issued to prompt the inspection of the bearing lubrication liquid supply path.

2) The refrigeration system gradually stabilizes:

As shown in S4 and S15 in Figures 8 and 9, after the refrigeration system 31 is started, the compressor 42 starts to run. When the pressure difference ΔP of the refrigeration system is greater than the sum of the minimum allowable pressure difference ΔP _min of the bearing supply liquid and the upward offset value P _up of the bearing supply liquid difference, and the duration is greater than the first set time T _s1 , that is, ΔP>ΔP _min +P _up is satisfied, and the duration is greater than T _s1 , the controller 100 determines that the refrigeration system 31 meets the pressure difference condition of natural supply liquid. At this time, the refrigerant liquid in the bearing supply liquid bag 13 can be transported to the bearing 3 for lubrication by only the refrigeration system pressure difference ΔP, and the main refrigeration liquid pump 201 is turned off; the bearing of the compressor 42 is supplied with liquid through the first bearing lubrication supply path 125.

In S14, S16, S18 and S19 in FIG. 9 , when the controller 100 turns off the refrigerant liquid pump 20 and supplies liquid to the bearing of the compressor 42 through the first bearing lubrication liquid supply path 125, one of the operating states is as follows:

In the case where the bearing fluid supply differential pressure ΔP _brg is greater than or equal to the minimum allowable bearing fluid supply differential pressure ΔP _min , that is, ΔP _brg <ΔP _min is not satisfied, no action is performed.

When the bearing fluid supply differential ΔP _brg is less than the minimum allowable pressure differential ΔP _min of the bearing fluid supply, and the bearing fluid supply differential ΔP _brg is greater than or equal to the difference between the minimum allowable pressure differential ΔP _min of the bearing fluid supply and the downward offset value P _down of the bearing fluid supply differential, or when the bearing fluid supply differential ΔP _brg is less than the minimum allowable pressure differential ΔP _min of the bearing fluid supply, and the bearing fluid supply differential ΔP _brg is less than the difference between the minimum allowable pressure differential ΔP _min of the bearing fluid supply and the downward offset value P _down of the bearing fluid supply differential, and its duration is less than or equal to T _s2 , that is, ΔP _brg <ΔP _min is satisfied, and ΔP _brg <ΔP _min -P _down is not satisfied, and the duration >T _s2 , the controller 100 controls the refrigeration system 31 to alarm and prompt to check the bearing lubrication fluid supply path.

As shown in S18 and S20 in Figure 9, when the bearing fluid supply pressure differential ΔP _brg is less than the difference between the minimum allowable bearing fluid supply pressure differential ΔP _min and the downward offset value P _down of the bearing fluid supply pressure differential, and the duration is greater than the second set time T _s2 , that is, ΔP _brg <ΔP _min -P _down , and the duration >T _s2 is satisfied, the controller 100 controls the refrigeration system 31 to alarm and shut down.

According to the set bearing fluid pressure difference judgment interval, its lower limit is ΔP _min -P _down . When the bearing fluid pressure difference ΔP _brg reaches below this lower limit, it indicates that there is a risk of insufficient bearing lubrication fluid power in the system. The duration of the delay determines whether to give an alarm or shut down the system. When the delay is greater than _Ts2 , it indicates that the risk of insufficient power is at its highest 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 being damaged by dry friction, the control logic directly controls the refrigeration system 31 to give an alarm and shut down the system, so that the compressor can leave this state in the shortest time and protect the bearings.

As shown in S17, S21 and S36 of FIG. 9, during the period when the refrigerant liquid pump 20 is turned off and the first bearing lubrication liquid supply path 125 is used to supply liquid to the bearing of the compressor 42, another operating state is as follows:

When the pressure difference ΔP of the refrigeration system 31 is less than the difference between the minimum allowable pressure difference ΔP _min of the bearing supply and the downward bias value P _down of the bearing supply pressure difference, and the duration is greater than the first set time T _s1 , that is, ΔP<ΔP _min -P _down and the duration>T _s1 are satisfied, at this time, the controller 100 regards that the pressure difference ΔP of the refrigeration system alone is insufficient to supply liquid for bearing lubrication, and starts the main refrigeration liquid pump 201; the bearing of the compressor 42 is supplied with liquid through the second bearing lubrication liquid supply path 126, and the main refrigeration liquid pump 201 pumps refrigerant liquid from the bearing supply liquid bag 13 to supply liquid for bearing 3. If ΔP<ΔP _min -P _down is not satisfied, and the duration>T _s1 , no action is performed.

As shown in S22, S27 and S24 of FIG9 , during the period when the controller 100 starts the main refrigerant liquid pump 201 and supplies liquid to the bearing of the compressor 42 through the second bearing lubrication liquid supply path 126, one of the operating states is as follows:

When the bearing supply pressure differential ΔP _brg is less than or equal to the minimum allowable pressure differential ΔP _min of the bearing supply, or when the bearing supply pressure differential ΔP _brg is greater than the minimum allowable pressure differential ΔP _min of the bearing supply, and the duration is less than or equal to the first set time T _s1 , that is, ΔP _brg > ΔP _min and the duration > T _s1 are not satisfied, the controller 100 determines that the operation state of the main refrigerant liquid pump 201 is poor, and at this time, the standby refrigerant liquid pump 202 is switched. If ΔP _brg > ΔP _min and the duration > T _s1 are satisfied, no action is performed.

As shown in S24, S25, S26 and S27 in Figure 9, when the standby refrigerant liquid pump 202 is turned on and the bearings of the compressor 42 are supplied with liquid through the second bearing lubrication liquid supply path 126: if the bearing supply pressure differential ΔP _brg is greater than the minimum allowable pressure differential ΔP _min of the bearing supply and the duration is greater than the first set time T _s1 , that is, ΔP _brg > ΔP _min and the duration is greater than T _s1 , the controller 100 determines that the operating state of the standby refrigerant liquid pump 202 is good and the bearings of the compressor 42 can be supplied with liquid normally through the second bearing lubrication liquid supply path 126, and no action is performed; if the bearing supply pressure differential ΔP _brg is not greater than the minimum allowable pressure differential ΔP _min of the bearing supply and the duration is greater than the first set time T _s1 , that is, ΔP _brg > ΔP _min and the duration is greater than T _s1 , the controller 100 determines that the operating state of the standby refrigerant liquid pump 202 is poor, and an alarm is issued to prompt the inspection of the bearing lubrication liquid supply path.

As shown in S8, S9, S14 and S10 of FIG9 , during the period when the controller 100 starts the main refrigerant liquid pump 201 and supplies liquid to the bearing of the compressor 42 via the second bearing lubrication liquid supply path 126, another operating state is as follows:

When the bearing supply pressure differential ΔP _brg is less than or equal to the minimum allowable pressure differential ΔP _min of the bearing supply, or when the bearing supply pressure differential ΔP _brg is greater than the minimum allowable pressure differential ΔP _min of the bearing supply, and the duration is less than or equal to the first set time T _s1 , that is, ΔP _brg > ΔP _min and the duration > T _s1 are not satisfied, the controller 100 determines that the operation state of the main refrigerant liquid pump 201 is poor, and switches to use the standby refrigerant liquid pump 202. If ΔP _brg > ΔP _min and the duration > T _s1 are satisfied, the controller 100 controls the refrigeration system 31 to not perform any action.

As shown in S11, S12 and S13 in Figure 9, during the use of the standby refrigerant liquid pump, if the bearing supply pressure differential ΔP _brg is greater than the minimum allowable pressure differential ΔP _min of the bearing supply and the duration is greater than the first set time T _s1 , that is, ΔP _brg > ΔP _min and the duration is > T _s1 , the controller 100 determines that the operating state of the standby refrigerant liquid pump 202 is good, and the bearings of the compressor 42 can be normally supplied with liquid through the second bearing lubrication supply path 126, and no action is performed; if the bearing supply pressure differential ΔP _brg is not greater than the minimum allowable pressure differential ΔP _min of the bearing supply and the duration is greater than the first set time T _s1 , that is, ΔP _brg > ΔP _min and the duration is > T _s1 , the controller 100 determines that the operating state of the standby refrigerant liquid pump 202 is poor, and an alarm is issued to prompt the inspection of the bearing lubrication supply path.

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

As shown in S23, S26, S28 and S36 in FIG9 , during the period when the controller 100 starts the main refrigerant liquid pump 201 and supplies liquid to the bearing of the compressor 42 through the second bearing lubrication liquid supply path 126, one of the operating states is as follows:

When the bearing supply fluid differential pressure ΔP _brg is greater than or equal to the minimum allowable bearing supply fluid differential pressure ΔP _min , that is, ΔP _brg <ΔP _min is not satisfied, the controller 100 controls the refrigeration system 31 to perform no action.

When the bearing fluid supply differential pressure ΔP _brg is less than the minimum allowable pressure differential pressure ΔP _min of the bearing fluid supply, and the bearing fluid supply differential pressure ΔP _brg is greater than or equal to the difference between the minimum allowable pressure differential pressure ΔP _min of the bearing fluid supply and the downward offset value P _down of the bearing fluid supply differential pressure, or when the bearing fluid supply differential pressure ΔP _brg is less than the minimum allowable pressure differential pressure ΔP _min of the bearing fluid supply, and the bearing fluid supply differential pressure ΔP _brg is less than the difference between the minimum allowable pressure differential pressure ΔP _min of the bearing fluid supply and the downward offset value P _down of the bearing fluid supply differential pressure, and its duration is less than or equal to T _s2 , that is, ΔP _brg <ΔP _min is satisfied, and ΔP _brg <ΔP _min -P _down is not satisfied, and the duration>T _s2 , the controller 100 controls the refrigeration system 31 to alarm and prompt to check the bearing lubrication fluid supply path. When ΔP _brg <ΔP _min is not satisfied, the controller 100 controls the refrigeration system 31 to not perform any action.

As shown in S28 and S29 in Figure 9, when the bearing fluid supply pressure differential ΔP _brg is less than the difference between the minimum allowable bearing fluid supply pressure differential ΔP _min and the downward offset value P _down of the bearing fluid supply pressure differential, and the duration is greater than the second set time T _s2 , that is, ΔP _brg <ΔP _min -P _down , and the duration >T _s2 is satisfied, the controller 100 controls the refrigeration system 31 to alarm and shut down.

At the same time, in the stage where the oil-free bearing liquid supply air conditioning system is in operation: as shown in S33, S34 and S35 in Figure 9, when the value L _con collected by the first liquid level sensor 17 is greater than the minimum allowable liquid level L _cmin of the condenser 19, that is, L _con > L _cmin , the controller 100 controls the refrigeration system 31 without executing any action. At this time, the liquid level of the condenser 19 is sufficient, and sufficient refrigerant liquid can be continuously provided to the first liquid supply bag 13, keeping the opening of the first electric regulating valve 37 unchanged.

When the value L _con collected by the first liquid level sensor 17 is less than or equal to the minimum allowable liquid level L _cmin of the condenser 19, that is, L _con > L _cmin is not satisfied, the liquid level of 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 to reduce the opening of the first electric regulating valve 37, so that the amount of liquid supplied from the condenser 19 to the economizer 23 is reduced, so that the liquid level of the condenser 19 is restored to a higher level.

As shown in S30, S31 and S32 in FIG9 , when the refrigeration system detects that the refrigerant liquid subcooling T _sub under P ₃ and T ₃ is greater than the minimum allowable subcooling T _min of the bearing supply liquid, that is, T _sub > T _min is satisfied, the controller 100 controls the refrigeration system 31 to not perform any action, which can ensure that the bearing lubrication supply liquid is in a supercooled state, which is a pure supercooled pure liquid and almost does not contain gas. At this time, the refrigeration system is normal and no action is taken.

When the system detects that the refrigerant liquid subcooling _Tsub under _P3 and _T3 is less than or equal to the minimum allowable subcooling _Tmin of the bearing supply liquid, that is, _Tsub ＞ _Tmin is not satisfied, and the bearing lubrication supply liquid cannot be guaranteed to be in a subcooled state, the controller 100 adjusts the electronic expansion valve 36 to increase its opening, so that the subcooling of the bearing supply liquid is adjusted to meet the bearing lubrication supply requirements.

The operation process of the above 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 air intake 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 throttling orifice plate 21 along the refrigerant liquid 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 replenishment 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 throttling orifice plate 25 to complete a cycle. 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.

In the initial stage of the operation of the refrigeration system 31, the condenser 19 and the evaporator 29 in the refrigeration system 31 The pressure difference is small. At this time, the controller 100 controls the main refrigerant liquid pump 201 to remain in the open state. The main refrigerant liquid pump 201 continuously pumps refrigerant liquid from the first liquid supply bag 13 containing more 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 path 120 of the second bearing lubrication liquid supply path to the final path 121 of the second bearing lubrication liquid supply path, and then be divided into a bearing lubrication liquid supply branch path 111 and a bearing lubrication liquid supply branch path 112 for lubricating the left and right side 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 pressure 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, thereby 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.

3) Normal shutdown of the refrigeration system:

As shown in Figures 8 and 10, a certain time before the refrigeration system 31 is shut down, the controller 100 turns on the main refrigeration liquid pump 201, and the main refrigeration liquid pump 201 forces liquid supply. At this time, the pressure regulating valve 10 is adjusted to adjust the pressure difference between the liquid pressure 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 of the main refrigeration liquid pump 201 when it is turned on or off will not be too large, reducing the impact on the operation of the refrigeration system. This state can ensure that the bearing 3 in the compressor continues to be lubricated with sufficient refrigerant liquid.

As shown in M1, M2, M3, M7, M8 and M9 in FIG10 , after the refrigeration system 31 is shut down, due to the reduction of 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 operation, the operation 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 and the main refrigeration liquid pump 201 is shut down. When the main refrigeration liquid pump 201 is shut down, the first solenoid valve 33 is opened, so that the connecting pipe path 103 at the bottom of the condenser 19 and the evaporator 29 are connected, so that after the refrigeration system is shut down, the refrigerant liquid level in the two devices becomes evenly distributed, and the bearing liquid supply bag 13 at the lower part of the condenser 19 will also be filled with refrigerant liquid, accumulating sufficient refrigerant liquid for bearing liquid lubrication when the machine is turned on next time.

As shown in M9, M10, M11 and M12 in FIG. 10 , 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, when the bearing supply pressure difference ΔP _brg is less than or equal to the minimum allowable pressure difference ΔP _min of the bearing supply, or when the bearing supply pressure difference ΔP _brg is greater than the minimum allowable pressure difference ΔP _min of the bearing supply, and the duration is less than or equal to the first set time T _s1 , that is, ΔP _brg > ΔP _min is not satisfied, and the duration is > T _s1 , the controller 100 determines that the operation state of the main refrigerant liquid pump 201 is poor, and at this time, the standby refrigerant liquid pump 202 is switched to be used. If ΔP _brg > ΔP _min is satisfied, and the duration is > T _s1 , no action is performed.

As shown in M11, M13 and M14 in Figure 10, if the bearing fluid supply differential pressure ΔP _brg is greater than the minimum allowable bearing fluid supply pressure differential ΔP _min and the duration is greater than the first set time T _s1 , that is, ΔP _brg ＞ΔP _min and the duration is greater than T _s1 , the controller 100 determines that the operating state of the standby refrigerant liquid pump 202 is good, and the bearings of the compressor 42 can be normally supplied with fluid through the second bearing lubrication fluid supply path 126, and no action is performed; if the bearing fluid supply differential pressure ΔP _brg is not greater than the minimum allowable bearing fluid supply pressure differential ΔP _min and the duration is greater than the first set time T _s1 , that is, ΔP _brg ＞ΔP _min and the duration is greater than T _s1 , the controller 100 determines that the operating state of the standby refrigerant liquid pump 202 is poor, and an alarm is issued to prompt the inspection of the bearing lubrication fluid supply path.

Finally, the refrigeration system 31 is shut down safely.

4) Abnormal shutdown of the refrigeration system (such as abnormal power failure):

As shown in FIG8 and FIG10, when the refrigeration system 31 is suddenly shut down due to power failure, 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, so 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 to supply liquid to the emergency bearing, and the refrigerant liquid will From the first liquid supply 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 divided into a bearing lubrication liquid supply branch path 111 and a bearing lubrication liquid supply branch path 112 for lubricating the left and right side bearings 3 in the compressor 42.

As shown in M4, M6 and M8 in Figure 10, due to power failure and shutdown, the system circulation stops, the controller 100 closes the second solenoid valve 12 on the bearing return liquid or return air path 118, and the high pressure of the condenser 19 and the low pressure of the evaporator 29 will always be gradually balanced through the pipeline connection, that is, the process of supplying liquid to the bearing 3 only by the pressure difference ΔP of the refrigeration system can last about 15-20s, but the motor rotor in the permanent magnet motor can generally stop completely within 5-10s. Therefore, in the case of using permanent magnet motors, such an emergency liquid supply method for lubricating the bearings is still reliable and effective.

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-shutdown operation state, that is, the refrigeration system pressure difference ΔP is less than the bearing liquid supply differential ΔP _brg , then there is a sudden power outage and shutdown, and the bearing cannot be supplied with liquid only by the refrigeration system pressure difference ΔP. At this time, the controller 100 controls the refrigeration liquid pump in the refrigeration system 31, which can preferably be powered by a UPS power supply, and the main refrigeration liquid pump 201 can be started and run, so that it can continuously pump liquid from the first liquid supply liquid bag 13 to the bearing 3 in the compressor. In addition, due to the gradual balance of high and low pressures, the refrigerant liquid gradually accumulated in the evaporator 29 can also continuously replenish the refrigerant liquid to the first liquid supply liquid bag 13 through the connecting pipeline 103, so that the main refrigeration liquid pump 201 can always pump sufficient liquid for the bearing 3 to lubricate it, and this process continues until the rotor stops completely.

Finally, the refrigeration system 31 stops operating.

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 for a certain period of time, thereby improving the safety and reliability of the bearing operation after shutdown.

In some embodiments, as shown in S30, S31, S32, S33, S34 and S35 in FIG. 9 and FIG. 10, in all stages of the operation of the refrigeration system, the controller 100 controls the refrigeration system 31 to constantly detect the state parameters of the refrigerant liquid for bearing lubrication:

When the value L _con collected by the first liquid level sensor 17 is greater than the minimum allowable liquid level L _cmin of the condenser 19, that is, 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.

When the refrigeration system detects that the refrigerant liquid subcooling _Tsub under _P3 and _T3 is greater than the minimum allowable subcooling _Tmin of the bearing supply liquid, that is, _Tsub > _Tmin is satisfied, the controller 100 controls the refrigeration system 31 to not perform any action, which can ensure that the bearing lubrication supply liquid is in a supercooled state, which is a pure supercooled pure liquid and almost does not contain gas. At this time, the refrigeration system 31 is normal and does not take any action.

When the system detects that the refrigerant liquid subcooling _Tsub under _P3 and _T3 is less than or equal to the minimum allowable subcooling _Tmin of the bearing supply liquid, that is, _Tsub ＞ _Tmin is not satisfied, and the bearing lubrication supply liquid cannot be guaranteed to be in a subcooled state, the controller 100 adjusts the electronic expansion valve 36 at this time, so that the subcooling of the bearing supply liquid is adjusted to meet the bearing lubrication supply requirements.

The present application applies two different bearing lubrication liquid supply paths to achieve stable and reliable bearing lubrication in all stages. Corresponding pipeline connections and power devices (pumps) are set in the system. According to the operating state 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 are lubricated at each stage. Sufficient refrigerant liquid can be obtained for lubrication, ensuring the safety of system operation.

For the convenience of explanation, the above description has been made in conjunction with specific embodiments. However, the above discussion in some embodiments is not intended to be exhaustive or limit the embodiments to the specific forms disclosed above. According to the above teachings, various modifications and variations can be obtained. The selection and description of the above embodiments are 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

An oil-free bearing liquid supply air conditioning system, 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;

The controller is configured as:

During the startup phase, the main refrigeration liquid pump is turned on;

In the stable 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 liquid and the upward offset value of the bearing supply liquid difference, and the duration is greater than the first set time, the main refrigeration liquid pump is turned off; 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 and the upward offset value of the bearing fluid supply differential, 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 offset value of the bearing fluid supply differential, and the duration is less than or equal to the first set time, the main refrigeration liquid pump is maintained on; and the bearings of the compressor are supplied with fluid through the second bearing lubrication supply path.
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 which are connected in sequence;

The front section path of the first bearing lubrication fluid supply path and the front section path of the second bearing lubrication fluid supply path are arranged in parallel, and the rear section path of the first bearing lubrication fluid supply path and the rear section path of the second bearing lubrication fluid supply path are the same path; the initial section path of the first bearing lubrication fluid supply path and the initial section path of the second bearing lubrication fluid supply path are the same path, and both are connected to the condenser; the final section path of the first bearing lubrication fluid supply path and the final section path of the second bearing lubrication fluid supply path are the same path, and both are connected to the compressor.
The oil-free bearing liquid supply air conditioning system according to claim 2, wherein the controller is further configured as:

In the stable operation stage, and when the main refrigeration liquid pump is turned off and the first bearing lubrication 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 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 supply path.
The oil-free bearing liquid supply air conditioning system according to claim 2, wherein the controller is further configured as:

In the stable operation stage, and when the main refrigeration 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 a second set time, the refrigeration system is controlled to alarm and shut down.
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 fluid or return air.
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 is connected to the last section of the first bearing lubrication fluid supply path and is configured to collect a pressure value of the bearing lubrication 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.
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 and the downward 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 on; the bearing of the compressor is supplied with liquid through the second bearing lubrication supply path;

During the period when 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, 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 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 to check the bearing lubrication liquid supply path;

When the bearing fluid supply pressure differential is less than the difference between the minimum allowable bearing fluid supply pressure differential and the downward offset value of the bearing fluid supply pressure differential, and the duration is greater than the second set time, the refrigeration system is controlled to alarm and shut down;

The bearing supply fluid differential is the difference between the pressure value of the bearing supply fluid and the pressure value of the bearing lubrication return fluid or return air measured in real time.
The oil-free bearing liquid supply air conditioning system according to claim 1, further comprising:

A communication pipeline is provided between the condenser and the evaporator, the communication pipeline comprises a first solenoid valve, and the first solenoid valve is configured to control the opening and closing of the communication pipeline;

A second solenoid valve disposed 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 also configured to:

During the 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 bearing of the compressor is 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 also configured to:

During the normal power-off 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 the 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 failure shutdown stage:

Close the second solenoid valve.
The oil-free bearing liquid supply air conditioning system according to claim 1, wherein the controller is further configured for:

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 bearing of the compressor; 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 standby refrigerant liquid pump is turned on;

During the period when the standby refrigeration 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.
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 of the condenser;

The controller is also 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.
The oil-free bearing liquid supply air conditioning system according to claim 1, further comprising:

a supercooler, the supercooler communicating with the rear section of the first bearing lubricating fluid supply path and the last 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, the first temperature sensor being configured to monitor the temperature of a final section of the first bearing lubrication supply path;

The controller is also configured to:

When the subcooling degree of the refrigerant liquid is greater than the minimum allowable subcooling degree of the bearing supply liquid, the refrigeration system is controlled 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 of the bearing supply liquid and the temperature of the bearing supply liquid, and the minimum allowable subcooling degree of the bearing supply liquid is a preset value.
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 0.05MPa to 0.35MPa;

The upward bias value range of the bearing hydraulic pressure difference is 0MPa to 0.35MPa;

The downward bias value range of the bearing hydraulic pressure difference is 0MPa to 0.35MPa;

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.
A control method for an oil-free bearing liquid supply air conditioning system is applied to the oil-free bearing liquid supply air conditioning system, wherein the oil-free bearing liquid supply air conditioning system comprises:

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 The two refrigeration liquid pumps include a main refrigeration liquid pump and at least one backup refrigeration liquid pump;

The control method comprises:

During the startup phase, the main refrigeration liquid pump is turned on;

In the stable 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 liquid and the upward offset value of the bearing supply liquid difference, and the duration is greater than the first set time, the main refrigeration liquid pump is turned off; 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 and the upward offset value of the bearing fluid supply differential, 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 offset value of the bearing fluid supply differential, and the duration is less than or equal to the first set time, the main refrigeration liquid pump is maintained on; and the bearings of the compressor are supplied with fluid through the second bearing lubrication supply path.
The control method of the oil-free bearing liquid supply air conditioning system according to claim 13 further comprises:

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 which are connected in sequence;

The front section path of the first bearing lubrication fluid supply path and the front section path of the second bearing lubrication fluid supply path are arranged in parallel, and the rear section path of the first bearing lubrication fluid supply path and the rear section path of the second bearing lubrication fluid supply path are the same path; the initial section path of the first bearing lubrication fluid supply path and the initial section path of the second bearing lubrication fluid supply path are the same path, and both are connected to the condenser; the final section path of the first bearing lubrication fluid supply path and the final section path of the second bearing lubrication fluid supply path are the same path, and both are connected to the compressor.
The control method of the oil-free bearing liquid supply air conditioning system according to claim 14 further comprises:

In the stable operation stage, and when the main refrigeration liquid pump is turned off and the first bearing lubrication 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 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 supply path.
The control method of the oil-free bearing liquid supply air conditioning system according to claim 14 further comprises:

In the stable operation stage, and when the main refrigeration 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 a second set time, the refrigeration system is controlled to alarm and shut down.
The control method of the oil-free bearing liquid supply air conditioning system according to claim 13 further comprises:

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 fluid or return air.