Air conditioner

Abstract

The application discloses an air conditioner and belongs to the technical field of air conditioners. The air conditioner comprises: a refrigerant circulation loop, which circulates refrigerant in a loop composed of a compressor, an outdoor heat exchanger, an expansion valve, an indoor heat exchanger and a gas-liquid separator; and a controller, which is configured to, in the starting stage and the transition stage of the air conditioner: acquire suction superheat of the compressor, calculate the refrigerant density p in the suction pipe according to the dynamic pressure of the suction port of the compressor, and calculate the suction dryness of the compressor according to the refrigerant property parameters; determine whether the compressor has a liquid strike risk according to the suction superheat and the suction dryness; if the liquid strike risk does not exist, control the opening degree of the expansion valve according to a preset control logic; and if the liquid strike risk exists, control the opening degree of the expansion valve to decrease or control the air conditioner to stop, so that the problem of the compressor liquid strike that is prone to occurring after low-temperature heating sleep starting or after starting after severe defrosting is effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of air conditioning technology, and in particular relates to an air conditioner. Background Technology

[0002] When air conditioners are used in large venues such as factories and shopping malls, the distance between the indoor and outdoor units is inevitably relatively far. In this case, long connecting pipes are required to connect the indoor and outdoor units. Because air conditioners using long connecting pipes (such as multi-split air conditioners) have a larger refrigerant charge in the entire air conditioning system, these systems are more prone to refrigerant return problems.

[0003] Existing measures to prevent liquid refrigerant backflow in multi-split air conditioners include designing a large-capacity gas-liquid separator in the refrigerant circulation loop, and recovering the refrigerant in the pipeline to the gas-liquid separator in the outdoor unit through evacuation during shutdown. However, in actual operation, poor control can also lead to liquid refrigerant returning to the compressor. Additionally, when the air conditioner starts up from low-temperature heating sleep mode or after severe defrosting, the gas-liquid separator is prone to becoming saturated with liquid. Low superheat in both the suction and discharge phases allows liquid refrigerant to fill the gas-liquid separator and return to the compressor through the suction port, causing liquid slugging and damage to the compressor. Summary of the Invention

[0004] This invention aims to at least partially solve one of the technical problems in the related art. Therefore,

[0005] According to embodiments of this disclosure, an air conditioner is provided, comprising:

[0006] The refrigerant circulation loop, in which the refrigerant circulates sequentially through the compressor, condenser, expansion valve, and evaporator, wherein one of the condenser and the evaporator is an outdoor heat exchanger and the other is an indoor heat exchanger;

[0007] A pressure detection device is used to detect the pressure data of the compressor in real time;

[0008] A temperature detection device is used to detect the suction temperature of the compressor in real time;

[0009] The controller is configured to operate during the start-up and transition phases of the air conditioner.

[0010] Obtain the suction superheat of the compressor;

[0011] The refrigerant density ρ in the suction pipe is calculated based on the dynamic pressure at the suction port in the pressure data.

[0012] The suction dryness of the compressor is calculated based on the refrigerant density ρ and refrigerant properties in the suction pipe.

[0013] The compressor is judged to have a risk of liquid slugging based on the suction superheat and suction dryness.

[0014] If there is no risk of liquid slugging, the opening of the expansion valve is adjusted according to the preset control logic; if there is a risk of liquid slugging, the level of liquid slugging risk is determined.

[0015] If the liquid hammer risk level is level one, then control the opening of the expansion valve to decrease to the first opening degree;

[0016] If the liquid hammer risk level is level two, then control the opening of the expansion valve to decrease to the second opening degree;

[0017] If the liquid slugging risk level is level three, then control the air conditioner to shut down;

[0018] Wherein, the return liquid volume of the third level is greater than that of the second level, the return liquid volume of the second level is greater than that of the first level, and the first opening degree is greater than that of the second opening degree.

[0019] The above technical solution has the following advantages or beneficial effects: During the start-up and transition phases of the air conditioner, the suction dryness and suction superheat are monitored in real time, and the opening of the expansion valve is dynamically adjusted based on these indicators to determine whether liquid return and the level of liquid slugging risk. This not only ensures the stable operation of the system but also avoids malfunctions caused by liquid return. Specifically, in the third level, automatic shutdown is controlled to protect the compressor from damage; when there is a risk of liquid slugging but it is not in the third level, the opening of the expansion valve is reduced earlier to prevent the compressor from sucking in too much liquid refrigerant, thereby avoiding the risk of liquid return.

[0020] According to embodiments of this disclosure, the controller is configured to:

[0021] If the intake superheat is not less than the first preset value A, or the intake dryness exceeds the second preset value B, then it is determined that the compressor does not have a risk of liquid slugging.

[0022] If the intake superheat is less than a first preset value A and not less than a fourth preset value W, or if the intake dryness is not greater than a second preset value B, then determine whether the intake dryness is not less than a third preset value C. If yes, then determine that the liquid hammer risk level is the first level, and control the opening of the expansion valve to decrease P to the first opening. If no, then determine that the liquid hammer risk level is the second level, and control the opening of the expansion valve to decrease Q to the second opening.

[0023] If the intake superheat is less than the fourth preset value W, determine whether the intake dryness exceeds the preset threshold D. If yes, determine the liquid slugging risk level as the second level and control the opening of the expansion valve to decrease Q to the second opening. If no, determine the liquid slugging risk level as the third level and control the air conditioner to stop. Wherein, the preset threshold D < the third preset value C.

[0024] The above technical solution has the following advantages or beneficial effects: In the second stage, the opening degree of the expansion valve is controlled to be less than that in the first stage, so as to increase the suction superheat in the second stage, prevent excessive liquid carry-over in the suction, ensure that the compressor operates in a safe state, maximize heat exchange efficiency, avoid energy loss, and improve the overall cooling efficiency of the system.

[0025] According to embodiments of this disclosure, the temperature detection device is further configured to detect the discharge temperature of the compressor in real time, and the controller is configured to:

[0026] During the stable operation phase of the air conditioner, the intake superheat, the change in intake superheat, the exhaust superheat, and the change in exhaust superheat are obtained.

[0027] The presence of liquid slugging risk in the compressor is determined based on the intake superheat and its change or the exhaust superheat and its change.

[0028] If there is no risk of liquid slugging, the opening of the expansion valve is adjusted according to the preset control logic; if there is a risk of liquid slugging, the liquid slugging risk level of the compressor is determined.

[0029] If the liquid hammer risk level is the first level, then control the opening degree of the expansion valve to decrease by P;

[0030] If the liquid hammer risk level is the second level, then control the opening of the expansion valve to decrease by Q, where Q > P;

[0031] If the liquid slugging risk level is the third level, then the air conditioner is shut down.

[0032] The above technical solution has the following advantages or beneficial effects: by adjusting the opening of the expansion valve according to the change in suction superheat or the change in discharge superheat, the state of the refrigerant entering the compressor is changed, liquid return is avoided, and the compressor is effectively protected from damage.

[0033] According to embodiments of this disclosure, the controller is configured to:

[0034] If the intake superheat is not less than the first preset value A, it is determined that the compressor does not have a risk of liquid slugging, and the opening of the expansion valve is adjusted according to the preset control logic.

[0035] If the intake superheat is greater than the fifth preset value E and less than the first preset value A, then determine whether the change in intake superheat is not less than the fourth preset value W; if yes, then determine that the liquid hammer risk level is the first level, and at this time control the opening of the expansion valve to decrease by P; if no, then determine that the liquid hammer risk level is the second level, and at this time control the opening of the expansion valve to decrease by Q.

[0036] If the intake superheat is greater than the sixth preset value F and not greater than the fifth preset value E, then the liquid hammer risk level is determined to be the second level, and the opening of the expansion valve is controlled to decrease by Q.

[0037] If the intake superheat is not greater than the sixth preset value F, the liquid slugging risk level is determined to be level three, and the air conditioner is controlled to shut down.

[0038] The above technical solution has the following advantages or beneficial effects: when judging the liquid slugging risk level based on the change in suction superheat and suction superheat, and in the second level, the opening of the expansion valve is controlled to be less than that in the first level, so as to quickly increase the suction superheat in the second level, prevent excessive liquid carryover in the suction, ensure that the compressor operates in a safe state, maximize heat exchange efficiency, avoid energy loss, and improve the overall cooling efficiency of the system.

[0039] According to embodiments of this disclosure, the controller is configured to:

[0040] If the exhaust superheat is not less than the seventh preset value G, it is determined that the compressor does not have a risk of liquid slugging. At this time, the opening of the expansion valve is adjusted according to the preset control logic.

[0041] If the exhaust superheat is greater than the eighth preset value H and less than the seventh preset value G, then determine whether the change in exhaust superheat is not less than the fourth preset value W; if yes, then determine that the liquid hammer risk level is the first level, and at this time control the opening of the expansion valve to decrease by P; if no, then determine that the liquid hammer risk level is the second level, and at this time control the opening of the expansion valve to decrease by Q.

[0042] If the exhaust superheat is greater than the ninth preset value I and not greater than the eighth preset value H, then the liquid hammer risk level is determined to be the second level, and the opening of the expansion valve is controlled to decrease by Q.

[0043] If the exhaust superheat is not greater than the ninth preset value I, the liquid slugging risk level is determined to be level three, and the air conditioner is controlled to stop.

[0044] The above technical solution has the following advantages or beneficial effects: when judging the liquid slugging risk level based on the change in exhaust superheat and exhaust superheat, and in the second level, the opening of the expansion valve is controlled to be less than that in the first level, so as to quickly increase the exhaust superheat in the second level, prevent liquid accumulation or liquid return problems, ensure that the compressor operates in a safe state, maximize heat exchange efficiency, avoid energy loss, and improve the overall cooling efficiency of the system.

[0045] According to embodiments of this disclosure, the controller is configured to:

[0046] During the stable operation phase of the air conditioner, the exhaust superheat and intake superheat of the compressor are obtained;

[0047] Based on the exhaust superheat and intake superheat, determine whether the compressor has a risk of liquid slugging;

[0048] If there is no risk of liquid slugging, the opening of the expansion valve is adjusted according to the preset control logic; if there is a risk of liquid slugging, the liquid slugging risk level of the compressor is determined.

[0049] If the liquid hammer risk level is the first level, then control the opening degree of the expansion valve to decrease by P;

[0050] If the liquid hammer risk level is the second level, then control the opening of the expansion valve to decrease by Q, where Q > P;

[0051] If the liquid slugging risk level is the third level, then the air conditioner is shut down.

[0052] The above technical solution has the following advantages or beneficial effects: by adjusting the opening of the expansion valve according to the suction superheat and discharge superheat, the state of the refrigerant entering the compressor is changed, liquid return is avoided, and the compressor is effectively protected from damage.

[0053] According to embodiments of this disclosure, the controller is configured to:

[0054] If the exhaust superheat is not less than the seventh preset value G, it is determined that the compressor does not have a risk of liquid slugging. At this time, the opening of the expansion valve is adjusted according to the preset control logic.

[0055] If the exhaust superheat is greater than the tenth preset value J and less than the seventh preset value G, then determine whether the intake superheat is not less than the first preset value A; if yes, then determine that the liquid hammer risk level is the first level, and at this time control the opening of the expansion valve to decrease by P; if no, then determine that the liquid hammer risk level is the second level, and at this time control the opening of the expansion valve to decrease by Q.

[0056] If the exhaust superheat is not greater than the tenth preset value J, then the change in the intake superheat is obtained and it is determined whether it is not less than the fourth preset value W; if so, then the liquid slugging risk level is determined to be the second level, and at this time, the opening of the expansion valve is controlled to decrease Q; if not, then the liquid slugging risk level is determined to be the third level, and at this time, the air conditioner is controlled to stop.

[0057] The above technical solution has the following advantages or beneficial effects: when judging the liquid slugging risk level based on the exhaust superheat and intake superheat, in the second level, the opening degree of the expansion valve is controlled to be less than that in the first level, so as to improve the efficiency of the compressor in the first level. At the same time, in the second level, liquid refrigerant is prevented from flowing into the compressor, thereby reducing liquid return.

[0058] According to embodiments of this disclosure, the refrigerant circulation loop further includes a float-type gas-liquid separator connected in series between the compressor's suction port and the evaporator's outlet, the pressure data includes low-pressure, and the controller is configured to:

[0059] When the air conditioner is running stably, the low-pressure change value is obtained within a preset time period;

[0060] The opening degree of the expansion valve is adjusted according to the low-pressure change value.

[0061] The above technical solution has the following advantages or beneficial effects: by adjusting the opening of the expansion valve according to the change in low pressure, i.e., the change in pressure at the suction port, the state of the refrigerant entering the compressor is changed, avoiding the flow of liquid refrigerant into the compressor, thereby reducing liquid return.

[0062] According to embodiments of this disclosure, the controller is configured to:

[0063] Determine whether the low-pressure change value is not less than the eleventh preset value K. If yes, perform multiple determinations and if the result is still yes, control the air conditioner to stop. If no, perform the first determination: whether the low-pressure change value is not less than the twelfth preset value L.

[0064] In the first judgment, if yes, then control the opening degree of the expansion valve to decrease by m; if no, then perform the second judgment: whether the low pressure change value is not less than the thirteenth preset value M.

[0065] In the second judgment, if yes, then control the opening degree of the expansion valve to decrease by n, n < m; if no, then perform the third judgment: whether the low pressure change value is not less than the fourteenth preset value N.

[0066] If the third determination is true, then the opening degree of the expansion valve remains unchanged.

[0067] The above technical solution has the following advantages or beneficial effects: By detecting changes in low-pressure value and controlling the air conditioner to shut down when the low-pressure change is large, it is possible to effectively prevent liquid refrigerant from flowing back into the compressor and prevent liquid return. When the low-pressure change is small, adjusting the opening of the expansion valve reduces the amount of refrigerant entering the float-type gas-liquid separator, avoiding liquid return caused by excessive refrigerant failing to vaporize effectively.

[0068] In another aspect, this application also provides an air conditioner comprising:

[0069] The refrigerant circulation loop, in which the refrigerant circulates sequentially through the compressor, condenser, expansion valve, and evaporator, wherein one of the condenser and the evaporator is an outdoor heat exchanger and the other is an indoor heat exchanger;

[0070] A pressure detection device is used to detect the pressure data of the compressor in real time;

[0071] A temperature detection device is used to detect the suction temperature of the compressor in real time;

[0072] The controller is configured to operate during the start-up and transition phases of the air conditioner.

[0073] Obtain the suction superheat of the compressor;

[0074] The refrigerant density p in the suction pipe is calculated based on the dynamic pressure of the suction port in the pressure data, and the suction dryness of the compressor is calculated based on the refrigerant density ρ in the suction pipe and the refrigerant physical property parameters.

[0075] The presence and level of liquid slugging risk in the compressor are determined based on the intake superheat and intake dryness.

[0076] If there is no risk of liquid slugging, the opening degree of the expansion valve is adjusted according to the preset control logic;

[0077] If the liquid slugging risk level is level three, then control the air conditioner to shut down;

[0078] If the liquid hammer risk level is level two, then control the opening degree of the expansion valve to decrease by Q;

[0079] If the liquid hammer risk level is level one, then control the opening degree of the expansion valve to decrease by P;

[0080] Where P < Q, the return volume of the third level is greater than the return volume of the second level, and the return volume of the second level is greater than the return volume of the first level.

[0081] The above technical solution has the following advantages or beneficial effects: During the start-up and transition phases of the air conditioner, the suction dryness and suction superheat are monitored in real time, and the opening of the expansion valve is dynamically adjusted based on the assessment of whether liquid return and the level of liquid slugging risk. This not only ensures the stable operation of the system but also avoids malfunctions caused by liquid return. Specifically, in the third stage, automatic shutdown is controlled to protect the compressor from damage; in the second stage, the opening of the expansion valve is controlled to be less than that in the first stage to increase the suction superheat, prevent excessive liquid carryover in the suction, ensure that the compressor operates in a safe state, maximize heat exchange efficiency, avoid energy loss, and improve the overall cooling efficiency of the system. Attached Figure Description

[0082] Figure 1 This is a system block diagram of an air conditioner according to an embodiment of the present disclosure;

[0083] Figure 2 This is a schematic diagram of the refrigerant circulation loop of an air conditioner according to an embodiment of the present disclosure. Figure 1 ;

[0084] Figure 3 This is a schematic diagram of the system structure of an air conditioner according to an embodiment of the present disclosure;

[0085] Figure 4 This is the control logic of the expansion valve of the air conditioner during the start-up and transition phases according to the embodiments of this disclosure;

[0086] Figure 5 This is a control flowchart of the expansion valve of an air conditioner during the start-up and transition phases according to an embodiment of this disclosure;

[0087] Figure 6 This is the control logic of the expansion valve of the air conditioner during the stable operation phase according to the embodiments of this disclosure;

[0088] Figure 7 This is a control flowchart of the expansion valve of an air conditioner during the stable operation phase according to an embodiment of the present disclosure;

[0089] Figure 8 This is a control flowchart of the expansion valve of an air conditioner during the stable operation phase according to another embodiment of this disclosure;

[0090] Figure 9 This is the control logic of the expansion valve of the air conditioner during the stable operation phase according to another embodiment of this disclosure;

[0091] Figure 10 This is a control flow chart of the expansion valve of an air conditioner during the stable operation phase according to another embodiment of this disclosure;

[0092] Figure 11This is an external view of the gas-liquid separator in an air conditioner according to an embodiment of this disclosure;

[0093] Figure 12 and Figure 13 These are cross-sectional views of the gas-liquid separator in an air conditioner at different locations according to embodiments of this disclosure;

[0094] Figure 14 and Figure 15 This is an internal structural diagram of the gas-liquid separator in an air conditioner according to an embodiment of the present disclosure;

[0095] Figure 16 This is a partial view of the gas-liquid separator according to an embodiment of the present disclosure with the covering device in the open state;

[0096] Figure 17 This is a partial view of the gas-liquid separator according to an embodiment of the present disclosure with the covering device in the covered state;

[0097] Figure 18 The control logic of the expansion valve is based on the embodiment of this disclosure, which regulates the low-pressure control.

[0098] Figure 19 This is a flowchart illustrating the process of controlling the expansion valve by detecting low pressure according to an embodiment of this disclosure;

[0099] Figure 20 This is a control flowchart of the expansion valve of the air conditioner during the start-up and transition phases in the cooling mode according to the embodiments of this disclosure;

[0100] Figure 21 This is a control flowchart of the expansion valve of the air conditioner during the start-up and transition phases in the heating mode according to the embodiments of this disclosure. Detailed Implementation

[0101] To make the objectives, technical solutions, and advantages of this application clearer, the application is described and illustrated below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0102] Obviously, the accompanying drawings described below are merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios based on these drawings without any inventive effort. Furthermore, it is understood that although the efforts made in this development process may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, any changes to design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as insufficient disclosure of the content of this application.

[0103] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0104] The terms "connection," "linked," and "coupled" used in this application are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Multiple" in this application refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, "3 and / or 0.9" can represent: 3 alone, 3 and 0.9 simultaneously, and 0.9 alone. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. The terms "first," "second," and "third" used in this application are merely to distinguish similar objects and do not represent a specific ordering of objects.

[0105] This invention provides an air conditioner 10, as described below. Figures 1-21 The air conditioner 10 provided in this application will be described.

[0106] In one illustrative embodiment of the air conditioner 100 provided by the present invention, reference is made to... Figure 1 The air conditioner 100 may be a multi-split air conditioner, which includes at least one indoor unit 20. The indoor unit 20 is typically located indoors and is used for heat exchange with the indoor environment.

[0107] The indoor unit 20 can be configured as a wall-mounted unit, floor-standing unit, ceiling unit, duct unit, curtain unit, or ceiling unit.

[0108] Air conditioner 100 may include outdoor unit 10. Outdoor unit 10 is typically located outdoors and is used to carry indoor heat to the outside.

[0109] The indoor unit 20 and the outdoor unit 10 can be configured as an integrated unit or a split unit.

[0110] The indoor unit 20 may include an indoor unit housing. The indoor unit housing forms the appearance of the indoor unit 20.

[0111] An installation cavity is formed inside the indoor unit housing. The installation cavity is used to accommodate and fix various components in the indoor unit 20.

[0112] The indoor unit housing may include an air inlet. The air inlet communicates with the mounting cavity and serves as the entrance for external air to flow into the indoor unit housing, allowing indoor air to enter the mounting cavity through the air inlet.

[0113] The indoor unit casing may include an air outlet. The air outlet is connected to the mounting cavity and serves as the outlet for the heat exchange airflow inside the indoor unit casing, allowing the airflow inside the mounting cavity to flow out through the air outlet.

[0114] The indoor unit 20 may include an indoor heat exchanger 21. The indoor heat exchanger 21 is located in the mounting cavity and is used to exchange heat with the airflow inside the indoor unit casing.

[0115] The indoor unit 20 may include an indoor fan 22. The indoor fan 22 is disposed within the mounting cavity and is used to drive the air within the mounting cavity to flow from the air inlet to the air outlet.

[0116] The outdoor unit 10 may include an outdoor unit housing. The outdoor unit housing has an internal receiving space and forms the appearance of the outdoor unit 10.

[0117] The outdoor unit housing may include an outdoor air intake. The outdoor air intake may communicate with the housing space. The outdoor air intake can be used to introduce outdoor air into the housing space.

[0118] The outdoor unit casing may include an outdoor air outlet. The outdoor air outlet may communicate with the housing. The outdoor air outlet can be used to draw air from the housing to the outside of the housing.

[0119] The outdoor unit 10 may include an outdoor heat exchanger 11. The outdoor heat exchanger 11 may be located within a housing space.

[0120] The outdoor unit 10 may include an outdoor fan 12. The outdoor fan 12 may be located within the housing. The rotation of the outdoor fan 12 causes outdoor air to enter the housing through the outdoor air inlet and exchange heat with the outdoor heat exchanger 11. The heat-exchanged outdoor air then flows out of the housing through the outdoor air outlet.

[0121] The air conditioner 100 may include a compressor 14. The compressor 14 is located inside the outdoor unit housing.

[0122] The compressor 14 is used to compress refrigerant gas in a low-temperature, low-pressure state into a high-temperature, high-pressure state, and discharge the compressed refrigerant gas to the condenser 42. The compressor 14 can be a variable frequency compressor 14.

[0123] In some embodiments, the outdoor unit 10 may include a gas-liquid separator 16. The gas-liquid separator 16 is used to separate the refrigerant into gas and liquid components.

[0124] refer to Figure 2 The gas-liquid separator 16 can be installed at the suction port of the compressor 14.

[0125] The gas-liquid separator 16 separates the refrigerant returning from the evaporator to the compressor 14 into gas and liquid. During operation, the gas returns to the compressor 14, reducing the amount of liquid refrigerant entering the compressor 14. This prevents excessive liquid refrigerant from entering the compressor 14, which could alter the state of the lubricating oil inside the compressor 14 or even cause liquid compression, severely reducing the operational reliability of the compressor 14.

[0126] The outdoor unit 10 may include a four-way valve 15, which selectively directs the refrigerant compressed by the compressor 14 to the outdoor heat exchanger or the indoor unit 20, depending on the heating or cooling mode.

[0127] Air conditioner 100 may include a refrigerant circulation loop. (Reference) Figure 2 The diagram shows the structure of the refrigerant circulation loop. Connecting pipes are used to connect the indoor unit 20 and the outdoor unit 10 to form a refrigerant circulation loop for refrigerant circulation.

[0128] The air conditioner 100 uses a refrigerant circulation loop to circulate the refrigerant within a circuit consisting of the compressor 14, outdoor heat exchanger 11, indoor heat exchanger 21, four-way valve 15, and gas-liquid separator 16, enabling it to perform indoor cooling or heating. The evaporator and condenser consist of the indoor heat exchanger 21 and the outdoor heat exchanger 11, respectively.

[0129] The outdoor unit 10 may include an expansion valve for throttling. The expansion valve may be located in the outdoor unit 10, or it may be located in both the indoor unit 20 and the outdoor unit 10.

[0130] It is understandable that when the indoor heat exchanger 21 is used as a condenser, the air conditioner 100 is used as a heater in heating mode, and when the indoor heat exchanger 21 is used as an evaporator, the air conditioner 100 is used as a cooler in cooling mode.

[0131] Refrigeration and heating cycles include compression, condensation, expansion, and evaporation processes. They provide cooling or heating to the indoor space through the refrigerant's heat absorption and release processes, thus regulating the indoor temperature. Specifically:

[0132] The condenser condenses the high-temperature, high-pressure gaseous refrigerant compressed by the compressor 14 into liquid refrigerant, and the heat is released to the surrounding environment through the condensation process.

[0133] The liquid refrigerant flowing out of the condenser enters the expansion valve, which expands the high-temperature, high-pressure liquid refrigerant after condensation in the condenser into a low-pressure liquid refrigerant.

[0134] The low-pressure liquid refrigerant flowing out of the expansion valve enters the evaporator. As the liquid refrigerant flows through the evaporator, it absorbs heat and evaporates into a low-temperature, low-pressure refrigerant. The low-temperature, low-pressure refrigerant enters the gas-liquid separator 16 through the four-way valve 15. The gas-liquid separator 16 performs gas-liquid separation so that the refrigerant gas returns to the compressor 14.

[0135] The evaporator achieves a cooling effect by exchanging heat with the material to be cooled using the latent heat of refrigerant evaporation. Throughout this entire cycle, the air conditioner 100 can regulate the temperature of the indoor space.

[0136] The air conditioner 100 may include a controller 30. The controller 30 is electrically connected to the indoor unit 20 and the outdoor unit 10 to control the operation of the various components inside them, so that the various components of the air conditioner 100 can operate to achieve the various predetermined functions of the air conditioner 100.

[0137] It is understood that the controller 30 is electrically connected to at least the compressor 14, the expansion valve, the indoor fan 22, and the outdoor fan 12.

[0138] The controller 30 refers to a device that can generate operation control signals based on instruction operation codes and timing signals, instructing the air conditioner 100 to execute control commands. For example, in response to a power-on or power-off command issued by a user, the controller 30 can perform an operation related to the object selected by the power-on or power-off command.

[0139] In some embodiments, the outdoor unit 10 may include a temperature detection device. The temperature detection device is used to detect the suction temperature and discharge temperature of the compressor 14 in real time.

[0140] refer to Figure 3 The temperature detection device may include an exhaust temperature sensor 182, which is installed at the exhaust port of the compressor 14 to detect the exhaust temperature. The exhaust temperature sensor 182 is electrically connected to the controller 30 to transmit the detected exhaust temperature to the controller 30 for subsequent control.

[0141] The temperature detection device may include a suction temperature sensor 181, which is installed at the suction port of the compressor 14 to detect the suction temperature. The suction temperature sensor 181 is electrically connected to the controller 30 to transmit the detected suction temperature to the controller 30 for subsequent control.

[0142] In related technologies, although setting up a gas-liquid separator 16 can prevent a large amount of liquid refrigerant from entering the compressor 14, liquid return may occur due to improper design or selection of the gas-liquid separator 16, improper control of the opening of the expansion valve (such as when the opening of the expansion valve is too large, the refrigerant in the evaporator may not be completely vaporized, resulting in some liquid refrigerant entering the gas-liquid separator 16), or pressure changes in the air conditioning system.

[0143] To address the aforementioned technical issues, in this embodiment, during the start-up, transition, and stable operation phases of the air conditioner, the opening of the expansion valve is adjusted based on different liquid slugging levels to change the state of the refrigerant entering the compressor 14, thereby preventing liquid return, improving the service life of the compressor 14, and ensuring heat exchange efficiency.

[0144] Understandably, the transition phase refers to the period after the air conditioner has started working, but before it has reached a fully stable operating state.

[0145] refer to Figure 4 The controller 30 is configured to operate during the start-up and transition phases of the air conditioner:

[0146] Obtain the suction superheat of compressor 14;

[0147] The refrigerant density p inside the suction pipe is calculated based on the dynamic pressure at the suction port in the pressure data;

[0148] The suction dryness of the compressor 14 is calculated based on the refrigerant density ρ in the suction pipe and the refrigerant physical property parameters.

[0149] Based on the intake superheat and intake dryness, it can be determined in advance whether there is a risk of liquid slugging in compressor 14;

[0150] If there is no risk of liquid slugging, the opening of the expansion valve is adjusted according to the preset control logic;

[0151] If the liquid slugging risk level is Level 1, then the opening degree of the control expansion valve is reduced to the first opening degree;

[0152] If the liquid slugging risk level is level two, then the opening degree of the control expansion valve is reduced to the second opening degree;

[0153] If the liquid slugging risk level is level three, then control the air conditioner to shut down.

[0154] Among them, the return volume of the third level is greater than that of the second level, the return volume of the second level is greater than that of the first level, and the first opening degree is greater than that of the second opening degree.

[0155] In this embodiment, during the start-up and transition phases of the air conditioner, the suction dryness and suction superheat are monitored in real time. Based on these, the presence of liquid return and the level of liquid slugging risk are determined in advance, and the opening of the expansion valve is dynamically adjusted. This not only ensures the stable operation of the system but also avoids malfunctions caused by liquid return. Specifically, when the liquid slugging risk level is level three, automatic shutdown is controlled to protect the compressor 14 from damage. When the liquid slugging risk level is not level three, the opening of the expansion valve is reduced in advance to prevent the compressor 14 from drawing in too much liquid refrigerant, thereby avoiding the risk of liquid return.

[0156] It is understood that in this embodiment, the controller 30 can calculate the intake superheat and exhaust superheat based on the intake temperature and exhaust temperature.

[0157] Specifically, the suction superheat is TsSH, where TsSH = Ts - Te. Here, Ts is the suction temperature of compressor 14, and Te is the saturation temperature corresponding to the low-pressure Ps, determined by the refrigerant characteristics. The discharge superheat is TdSH, where TdSH = Td - Tc. Here, Td is the discharge temperature of compressor 14, and Tc is the saturation temperature corresponding to the high-pressure Pd, determined by the refrigerant characteristics.

[0158] In this embodiment, the dynamic pressure at the intake port can be calculated by the difference between the total pressure at the intake port and the static pressure at the intake port. Of course, in other embodiments, other methods for testing dynamic pressure can also be used to calculate the dynamic pressure at the intake port.

[0159] In some embodiments, the outdoor unit 10 may include a pressure detection device for detecting pressure data of the compressor 14. The pressure detection device is electrically connected to the controller 30 to transmit the detected pressure data to the controller 30 for subsequent control.

[0160] Specifically, the pressure detection device may include a high-pressure sensor 172, which is located at the exhaust port of the compressor 14 to detect high pressure.

[0161] The pressure detection device may include a low-pressure sensor 173, which is located at the suction port of the compressor 14 to detect low pressure.

[0162] Understandably, in a refrigeration system, the high-pressure Pd refers to the high-pressure side pressure at the condenser end, which is the pressure state of the refrigerant when it enters the condenser after being compressed by the compressor 14. The low-pressure Ps usually refers to the low-pressure side pressure at the evaporator end, which is the pressure state of the refrigerant inside the evaporator.

[0163] The pressure detection device may include a total pressure sensor 171, which is disposed at the suction port of the compressor 14 to detect the total pressure at the suction port. The total pressure represents the sum of the static pressure and the dynamic pressure of the fluid.

[0164] It should be noted that the low pressure detected at the air intake is the same as the static pressure at the air intake. Since the dynamic pressure of the air conditioning system is approximately 10-100 kPa, the total pressure sensor 171 needs to be placed close to the low pressure sensor 173 to avoid excessive pressure loss in the pipeline due to excessive distance, which would affect the accuracy of the detection.

[0165] In this embodiment, calculating the refrigerant density ρ in the suction pipe based on the dynamic pressure at the suction port and the curing parameters of the compressor 14 specifically includes:

[0166] Calculate the dynamic pressure (the difference ΔP between the total pressure P1 and the static pressure Ps) based on the total pressure P1 and the static pressure Ps.

[0167] Using the dynamic pressure formula: Calculate the density of the inhalation tube Where V is the flow velocity at the intake port, and V can be calculated based on the curing parameters of compressor 14.

[0168] The curing parameters of compressor 14 may include the frequency H of compressor 14, the displacement L of compressor 14, and the inner diameter D of the suction pipe (inner diameter of the pipe at the pressure acquisition point), according to V = H × L ÷ π ÷ D. 2 The flow velocity V can be calculated by multiplying by 4.

[0169] For example, L = 28cm 3 Given that H = 60 r / s and the inner diameter of the inhalation tube D = 1.6 cm, then V = 28 × 60 ÷ π ÷ 1.6 2 ×4=835cm / s=8.35m / s. The fixed parameters of compressor 14 are all the parameters determined after the design of air conditioner outdoor unit 10 is completed.

[0170] The calculation of the suction dryness of compressor 14 based on the refrigerant density ρ in the suction pipe and the refrigerant's physical properties specifically includes:

[0171] Based on the refrigerant's physical properties, the saturated liquid density ρ at a given pressure P l saturated gas density ρg It is certain that the relationship between the refrigerant density ρ in the suction pipe and the actual measured density ρ is: ρ = χρ g +(1-χ)ρ l Based on this relationship, the inhalation dryness can be calculated.

[0172] It is understandable that suction dryness refers to the relative dryness or wetness of the refrigerant at the suction port of compressor 14, and suction dryness characterizes the amount of liquid carried. Dryness represents the mass ratio of gaseous refrigerant (i.e., the proportion of gaseous refrigerant to the total refrigerant mass). The suction dryness χ ranges from 0 to 1, where χ = 0 indicates that the refrigerant is completely liquid, and χ = 1 indicates that the refrigerant is completely gaseous. Under normal circumstances, the suction dryness with superheat is 1. When the dryness is below 1, the amount of liquid carried cannot be determined by pressure and temperature. In actual startup and operation, compressor 14 is strictly prohibited from operating with liquid. It can carry a certain amount of liquid vapor, but the dryness needs to be at a relatively high level, approximately 0.8 to 0.9 or higher.

[0173] Therefore, this application controls the intake state of the air conditioner during the start-up process based on the above logic to prevent the compressor 14 from returning liquid.

[0174] In this embodiment, the presence and level of liquid slugging risk of compressor 14 are determined in advance based on the intake superheat and intake dryness. The liquid slugging risk can include level 1, level 3, and high liquid slugging risk.

[0175] In some embodiments, the presence and level of liquid slugging risk in the compressor are determined based on the suction superheat and suction dryness. If no liquid slugging risk exists, the opening of the expansion valve is adjusted according to preset control logic. If the liquid slugging risk level is level three, the air conditioner is shut down; if the liquid slugging risk level is level two, the opening of the expansion valve is reduced by Q; if the liquid slugging risk level is level one, the opening of the expansion valve is reduced by P, where P < Q.

[0176] Specifically, controller 30 is configured as follows:

[0177] If the superheat of the intake air is not less than the first preset value A, or the dryness of the intake air exceeds the second preset value B, then it is determined that there is no risk of liquid slugging in compressor 14.

[0178] If the intake superheat is less than the first preset value A and not less than the fourth preset value W, or if the intake dryness is less than the second preset value B, determine whether the intake dryness is not less than the third preset value C. If yes, determine the liquid hammer risk level as the first level and control the opening of the expansion valve to decrease by P; if no, determine the liquid hammer risk level as the second level and control the opening of the expansion valve to decrease by Q, where P < Q.

[0179] If the superheat of the intake air is less than the fourth preset value W, determine whether the dryness of the intake air exceeds the preset threshold D. If yes, determine the liquid slugging risk level as the second level and control the opening of the expansion valve to decrease Q. If no, determine the liquid slugging risk level as the third level and control the air conditioner to stop. Wherein, the preset threshold D < the third preset value C.

[0180] For example, the first preset value A can be 3℃, the second preset value B can be 0.9, the third preset value C can be 0.8, the preset threshold D can be 0.6, and the fourth preset value W can be any value between 0 and 0.3℃.

[0181] More specifically, participate Figure 5 During the start-up and transition phases of the air conditioner, the suction superheat and suction dryness are monitored in real time, and step S11 is executed: determine whether the suction superheat TsSH meets the condition TsSH≥3℃, or determine whether the suction dryness χ meets the condition χ>0.9. If so, it is determined that there is no risk of liquid slugging in compressor 14.

[0182] In other words, if TsSH≥3℃ or χ>0.9, there is no risk of liquid slugging in compressor 14. At this time, step S12 is executed: the opening of the expansion valve is adjusted according to the preset control logic, that is, it is adjusted according to the normal expansion valve.

[0183] When TsSH≥3℃, it indicates that the suction superheat is high, meaning that a lot of refrigerant evaporates in the evaporator and there is less unevaporated liquid refrigerant. After further gas-liquid separation by the gas-liquid separator 16, the gaseous refrigerant enters the compressor 14, and there is no risk of liquid slugging in the compressor 14.

[0184] A value greater than 0.9 indicates a high suction dryness and low liquid refrigerant content, meaning compressor 14 also faces no risk of liquid slugging. When there is no risk of liquid slugging, the expansion valve...

[0185] The preset control logic is a control logic that compares the intake superheat and exhaust superheat with their relative preset values, and controls the increase or decrease of the valve opening based on the comparison result. This is an existing conventional technology and will not be elaborated on here.

[0186] After completing step S11, if not, i.e. TsSH < 3℃ or χ ≤ 0.9, proceed to step S13: determine whether TsSH satisfies 0℃ ≤ TsSH < 3℃; if yes, proceed to step S14: determine whether the inhalation dryness satisfies χ ≥ 0.8.

[0187] After executing step S14, if the condition is met, the liquid hammer risk level is determined to be level one, and step S15 is executed: control the opening of the expansion valve to decrease P to the first opening; if not, the liquid hammer risk level is determined to be level two, and step S16 is executed: control the opening of the expansion valve to decrease Q to the second opening, where P < Q.

[0188] If not after step S13, proceed to step S17: determine whether the inspiratory dryness satisfies χ>0.6.

[0189] After executing step S17, if the condition is met, the liquid slugging risk level is determined to be Level 2, and step S16 is executed: the opening degree of the expansion valve is reduced to the second opening degree. If not, the liquid slugging risk level is determined to be Level 3, and step S18 is executed: the air conditioner is stopped. Wherein, the preset threshold D < the third preset value C.

[0190] In this embodiment, when the suction superheat TsSH is between 0℃ and 3℃, if the suction dryness χ≥0.8, it means that the suction liquid carryover is barely acceptable and there is a certain suction superheat, which belongs to the first level. At this time, the opening degree P of the expansion valve is appropriately reduced to reduce the refrigerant flow and reduce the risk of liquid return.

[0191] When the suction superheat TsSH is between 0℃ and 3℃, if χ < 0.8, it indicates that there is a lot of liquid in the suction, which is in the second level. In this case, the opening of the expansion valve needs to be closed more, that is, the opening of the expansion valve needs to be reduced by Q, so as to increase the suction superheat, prevent excessive liquid in the suction, ensure that the compressor 14 operates in a safe state, maximize the heat exchange efficiency, avoid energy loss, and improve the overall cooling efficiency of the system.

[0192] If the suction superheat TsSH is less than 0℃, it usually means that there is a fault or abnormality in the system, so the machine should be shut down. In addition, if χ < 0.6, it means that there is too much liquid return, so the machine should be shut down directly to protect the compressor 14.

[0193] It should be noted that the opening degree refers to the extent to which the expansion valve opens during operation, usually expressed as a percentage. The percentage of opening degree reflects the proportional relationship between the actual opening of the expansion valve and the maximum possible opening. In this embodiment, P and Q are the actual number of steps in adjusting the expansion valve, which can be defined as the rate of change. Wherein, P = EVO(n-1) / a, Q = EVO(n-1) / b. a and b are fixed parameters.

[0194] It is understandable that the suction superheat of compressor 14 cannot theoretically be less than 0 during normal operation. In this embodiment, a comparison between TsSH and 0°C is added to consider the possibility of faults or abnormal conditions, thereby further protecting compressor 14.

[0195] In this embodiment, by controlling the opening of the expansion valve in advance based on the suction superheat and suction dryness, liquid return can be effectively avoided. During the start-up and transition phases of the air conditioner, when in the second stage, the opening of the expansion valve is controlled to be less than that in the first stage. This increases the suction superheat in the second stage, prevents excessive liquid carryover in the suction, ensures that the compressor 14 operates in a safe state, maximizes heat exchange efficiency, avoids energy loss, and improves the overall cooling efficiency of the system.

[0196] In some embodiments, reference Figure 6 The controller 30 is also configured as follows:

[0197] During the stable operation phase of the air conditioner, the intake superheat, the change in intake superheat, the exhaust superheat, and the change in exhaust superheat are obtained.

[0198] The risk of liquid slugging in compressor 14 can be determined in advance based on the intake superheat and its change or the exhaust superheat and its change.

[0199] If there is no risk of liquid slugging, the opening of the expansion valve is adjusted according to the preset control logic;

[0200] If there is a risk of liquid slugging, the liquid slugging risk level of compressor 14 is determined in advance. If the liquid slugging risk level is level three, the air conditioner 100 is shut down; otherwise, the opening of the expansion valve is reduced. Specifically, if the liquid slugging risk level is level one, the opening of the expansion valve is reduced by P; if the liquid slugging risk level is level two, the opening of the expansion valve is reduced by Q.

[0201] In this embodiment, the opening of the expansion valve is adjusted according to the change in suction superheat or the change in discharge superheat, thereby changing the state of the refrigerant entering the compressor 14, preventing liquid return, and effectively protecting the compressor 14 from damage.

[0202] During the stable operation phase of the air conditioner, the controller 30 is configured as follows:

[0203] If the intake superheat is not less than the first preset value A, it is determined that there is no risk of liquid slugging in compressor 14, and the opening of the expansion valve is adjusted according to the preset control logic.

[0204] If the intake superheat is greater than the fifth preset value E and less than the first preset value A, then determine whether the change in intake superheat is not less than the fourth preset value W; if yes, then determine the liquid hammer risk level as the first level, and at this time control the opening of the expansion valve to decrease by P; if no, then determine the liquid hammer risk level as the second level, and at this time control the opening of the expansion valve to decrease by Q.

[0205] If the intake superheat is greater than the sixth preset value F but not greater than the fifth preset value E, the liquid hammer risk level is determined to be the second level, and the opening of the expansion valve is reduced by Q.

[0206] If the intake superheat is not greater than the sixth preset value F, the liquid slugging risk level is determined to be level three, and the air conditioner is shut down.

[0207] In this embodiment, when determining the liquid hammer risk level based on the change in intake superheat and intake superheat, and at the second level, the opening of the expansion valve is controlled to be less than that at the first level, so as to quickly increase the intake superheat at the second level, prevent excessive liquid from being carried in the intake, and avoid liquid return.

[0208] For example, the first preset value A can be 3℃, the fifth preset value E can be 1℃, and the sixth preset value F can be 0.5℃.

[0209] Specifically, refer to Figure 7 The controller 30 is configured to execute step S21: determine whether the suction superheat meets TsSH≥3℃. If so, it is determined that there is no risk of liquid slugging in the compressor 14. At this time, step S22 is executed: adjust the opening of the expansion valve according to the preset control logic, that is, adjust it according to the normal expansion valve.

[0210] After completing step S21, if not, proceed to step S23: determine whether the intake superheat meets the following condition: 1℃ < TsSH < 3℃.

[0211] After completing step S23, if yes, proceed to step S24: determine whether the change in intake superheat satisfies ΔTsSH≥0℃; if no, proceed to step S25: determine whether the intake superheat satisfies: 0.5℃<TsSH<1℃.

[0212] After completing step S24, if the condition is met (ΔTsSH≥0℃), the liquid hammer risk level is determined to be Level 1, and step S26 is executed: control the opening of the expansion valve to decrease by P; if the condition is not met (ΔTsSH<0℃), the liquid hammer risk level is determined to be Level 2, and step S27 is executed: control the opening of the expansion valve to decrease by Q.

[0213] After executing step S25, if yes, the liquid slugging risk level is determined to be level two. At this time, step S27 is executed again: control the opening of the expansion valve to decrease Q; if no, step S28 is executed: control the air conditioner to stop.

[0214] In this embodiment, when the air conditioner is in a stable operating phase, if the suction superheat TsSH is 3°C or above, the suction dryness of the compressor 14 is high, there is no risk of liquid return, and the expansion valve is regulated according to normal valve regulation.

[0215] When the suction superheat TsSH is between 1 and 3°C, if ΔTsSH ≥ 0, it indicates that the suction superheat is increasing. That is, with Ps remaining constant, Ts is increasing, the dryness of the refrigerant absorbed by the air conditioning system is increasing, and the risk of liquid return or accumulation is low. In this case, the opening of the expansion valve should be appropriately reduced to EVO(n-1) / a. If ΔTsSH < 0, it indicates that the suction superheat is decreasing. In this case, the opening of the expansion valve needs to be closed more, i.e., the opening of the expansion valve should be reduced to EVO(n-1) / b to increase the suction superheat.

[0216] When the suction superheat TsSH is between 0.5 and 1°C, the opening of the expansion valve needs to be reduced to EVO(n-1) / b to quickly increase the suction superheat. If TsSH ≤ 0.5°C, it indicates excessive liquid return, so the compressor should be shut down directly to protect compressor 14.

[0217] In some other embodiments, during the stable operation phase of the air conditioner, the controller 30 is configured to:

[0218] If the exhaust superheat is not less than the seventh preset value G, it is determined that there is no risk of liquid slugging in compressor 14. At this time, the opening of the expansion valve is adjusted according to the preset control logic.

[0219] If the exhaust superheat is greater than the eighth preset value H and less than the seventh preset value G, then determine whether the change in exhaust superheat is not less than the fourth preset value W; if yes, then determine the liquid slugging risk level as the first level, and at this time control the opening of the expansion valve to decrease by P; if no, then determine the liquid slugging risk level as the second level, and at this time control the opening of the expansion valve to decrease by Q.

[0220] If the exhaust superheat is greater than the ninth preset value l and not greater than the eighth preset value H, the liquid hammer risk level is determined to be the second level, and the opening of the expansion valve is reduced by Q.

[0221] If the exhaust superheat is not greater than the ninth preset value l, the liquid slugging risk level is determined to be level three, and the air conditioner is controlled to stop.

[0222] In this embodiment, when determining the liquid slugging risk level based on the change in exhaust superheat and the exhaust superheat, and at the second level, the opening of the expansion valve is controlled to be less than that at the first level, so as to quickly increase the exhaust superheat at the second level, prevent liquid accumulation or liquid return problems, ensure that the compressor 14 operates in a safe state, maximize heat exchange efficiency, avoid energy loss, and improve the overall cooling efficiency of the system.

[0223] For example, the seventh preset value G can be 10°C, the eighth preset value H can be 6°C, and the ninth preset value I can be 4°C.

[0224] Specifically, refer to Figure 8Step S31: Determine whether the exhaust superheat TdSH meets the requirement of TdSH≥10℃. If so, determine that there is no risk of liquid slugging in compressor 14. Step S32: Adjust the opening of the expansion valve according to the preset control logic, that is, adjust it according to the normal expansion valve.

[0225] After completing step S31, proceed to step S33: determine whether the exhaust superheat meets the following condition: 6℃ < TdSH < 10℃.

[0226] After completing step S33, if yes, proceed to step S34: determine whether the change in exhaust superheat satisfies ΔTdSH≥0℃; if no, proceed to step S35: determine whether the intake superheat satisfies: 4℃<TsSH<6℃.

[0227] After executing step S34, if the condition is met (ΔTdSH≥0℃), the liquid hammer risk level is determined to be Level 1, and step S36 is executed: control the opening of the expansion valve to decrease by P; if the condition is not met (ΔTdSH<0℃), the liquid hammer risk level is determined to be Level 2, and step S37 is executed: control the opening of the expansion valve to decrease by Q.

[0228] After executing step S35, if yes, the liquid slugging risk level is determined to be level two. At this time, step S37 is executed again: control the opening of the expansion valve to decrease Q; if no, step S38 is executed: control the air conditioner to stop.

[0229] When the air conditioner is in a stable operating phase, if the exhaust superheat TdSH is 10℃ or above, the refrigerant dryness of compressor 14 (i.e., suction dryness) is relatively high, and there is no risk of liquid return. It can be adjusted according to the normal valve.

[0230] When the exhaust superheat TdSH is between 6 and 10°C, if ΔTdSH ≥ 0, it indicates an increasing trend in exhaust superheat. That is, with Pd remaining constant, Td is increasing, leading to a higher refrigerant dryness in the air conditioning system and a lower risk of liquid return or accumulation. The expansion valve opening should be appropriately reduced by P to decrease refrigerant flow, allowing for more complete evaporation and preventing liquid return. If ΔTdSH < 0, it indicates a decreasing trend in exhaust superheat. Therefore, the expansion valve opening needs to be closed more significantly, and its opening should be reduced by Q to increase the suction superheat.

[0231] When the exhaust superheat TdSH is between 4 and 6, the opening degree of the expansion valve decreases by Q to rapidly increase the exhaust superheat. If TdSH is less than or equal to 4, it indicates that there is too much liquid return, so the compressor is shut down directly to protect compressor 14.

[0232] In some other embodiments, reference is made to Figure 9 During the stable operation phase of the air conditioner, the controller 30 is configured as follows:

[0233] Obtain the discharge superheat and intake superheat of compressor 14;

[0234] Based on the exhaust superheat and intake superheat, determine in advance whether there is a risk of liquid slugging in compressor 14;

[0235] If there is no risk of liquid slugging, the opening of the expansion valve is adjusted according to the preset control logic;

[0236] If there is a risk of liquid slugging, the liquid slugging risk level of compressor 14 is determined in advance. If the liquid slugging risk level is level three, the air conditioner 100 is shut down; otherwise, the opening of the expansion valve is reduced. Specifically, if the liquid slugging risk level is level one, the opening of the expansion valve is reduced by P; if the liquid slugging risk level is level two, the opening of the expansion valve is reduced by Q.

[0237] In this embodiment, the opening of the expansion valve is adjusted according to the suction superheat and the discharge superheat to change the state of the refrigerant entering the compressor 14, thereby avoiding liquid return and effectively protecting the compressor 14 from damage.

[0238] The controller 30 is configured to:

[0239] If the exhaust superheat is not less than the seventh preset value G, it is determined that there is no risk of liquid slugging in compressor 14. At this time, the opening of the expansion valve is adjusted according to the preset control logic.

[0240] If the exhaust superheat is greater than the tenth preset value J and less than the seventh preset value G, then determine whether the intake superheat is not less than the first preset value A; if yes, then determine the liquid hammer risk level as the first level, and at this time control the opening of the expansion valve to decrease by P; if no, then determine the liquid hammer risk level as the second level, and at this time control the opening of the expansion valve to decrease by Q.

[0241] If the exhaust superheat is not greater than the tenth preset value J, then the change in intake superheat is obtained and it is determined whether it is not less than the fourth preset value W; if so, the liquid slugging risk level is determined to be the second level, and the opening of the expansion valve is reduced by Q; if not, the liquid slugging risk level is determined to be the third level, and the air conditioner is controlled to stop.

[0242] When determining the liquid slugging risk level based on the exhaust superheat and intake superheat, and when the liquid slugging risk level is level two, the opening of the expansion valve is controlled to be less than that of the expansion valve in level one, so as to improve the efficiency of compressor 14 when the liquid slugging risk level is level one, and at the same time, when the liquid slugging risk level is level two, liquid refrigerant is prevented from flowing into compressor 14, thereby reducing liquid return.

[0243] In this embodiment, the tenth preset value J can be 5°C.

[0244] Specifically, refer to Figure 10The controller 30 is configured to execute step S41: determine whether the exhaust superheat meets the requirement of TdSH≥10℃. If so, it is determined that there is no risk of liquid slugging in the compressor 14, and then execute step S42: adjust the opening of the expansion valve according to the preset control logic, that is, adjust it according to the normal expansion valve.

[0245] After completing step S41, if not, proceed to step S43: determine whether the exhaust superheat meets the requirement of 5℃ < TdSH < 10℃.

[0246] After completing step S43, if yes, proceed to step S44: determine whether the intake superheat satisfies TsSH≥3℃. If no, proceed to step S45: determine whether the change in intake superheat satisfies ΔTsSH≥0℃.

[0247] After executing step S44, if the condition is met, the liquid hammer risk level is determined to be Level 1, and step S46 is executed: control the opening degree of the expansion valve to decrease by P; if not, the liquid hammer risk level is determined to be Level 2, and step S47 is executed: control the opening degree of the expansion valve to decrease by Q.

[0248] After completing step S45, if yes, the liquid slugging risk level is determined to be Level 2, and step S46 is executed: control the opening of the expansion valve to decrease Q; if no, step S48 is executed: control the air conditioner to stop.

[0249] In this embodiment, when the air conditioner is in a stable operating phase, if the exhaust superheat TdSH is 10°C or above, the refrigerant absorption state of compressor 14 is relatively dry, and there is no risk of liquid return. It is regulated according to the normal valve.

[0250] When the exhaust superheat TdSH is between 5 and 10, if TsSH ≥ 3, it indicates that the suction superheat is not low, the refrigerant dryness of the air conditioning system is not low, the risk of liquid return or accumulation is small, the efficiency of compressor 14 may be slightly lower, and the opening of the expansion valve only needs to be appropriately reduced by P. If TsSH < 3, it indicates that the suction superheat is low, resulting in low exhaust superheat. In this case, the opening of the expansion valve needs to be closed more, that is, the opening of the expansion valve needs to be reduced by Q to increase the superheat.

[0251] When the exhaust superheat TdSH < 5, if ΔTsSH ≥ 0, it indicates that the suction superheat is increasing, meaning that Ts is rising while Ps remains constant. This indicates that the dryness of the refrigerant absorbed by the system is increasing, reducing the risk of liquid return or accumulation. Therefore, the expansion valve should be appropriately reduced by Q. If ΔTsSH < 0, it indicates that the suction superheat is decreasing, resulting in more liquid return. In this case, the system should be shut down directly to protect compressor 14.

[0252] It should be noted that the change in intake superheat ΔTsSH = TsSH(n) - TsSH(n-1), where TsSH(n) refers to TsSH at time n, and TsSH(n-1) refers to TsSH at time n-1. Similarly, the change in exhaust superheat ΔTdSH = TdSH(n) - TdSH(n-1), where TdSH(n) refers to TdSH at time n, and TdSH(n-1) refers to TdSH at time n-1.

[0253] When air conditioners are installed in large venues, the distance between the indoor unit 20 and the outdoor unit 10 may be particularly far. In this case, long connecting pipes are required between the indoor unit 20 and the outdoor unit 10, with lengths potentially reaching 50m or 100m. This increased pipe length necessitates increasing the refrigerant charge to ensure the air conditioner's normal operation. During low-temperature heating sleep mode startup and defrost startup, the liquid refrigerant returns to the gas-liquid separator 16. Due to the increased refrigerant charge, the liquid level in the gas-liquid separator 16 may exceed the suction port and flow into the compressor. This liquid compression in the compressor can damage it.

[0254] Therefore, this application improves the structure of the gas-liquid separator 16 to make it a float-type separator.

[0255] Reference Figure 11 The gas-liquid separator 16 may include a tank 310. The tank 310 is a closed cylinder, which constitutes the general appearance of the gas-liquid separator 16.

[0256] In some embodiments, the tank 310 may include a cylindrical body 311. The cylindrical body 311 is cylindrical with open upper and lower ends.

[0257] The tank body 310 may include an upper cover 312. The upper cover 312 is connected to the upper end of the cylinder 311 and is used to close the upper end of the cylinder 311.

[0258] The tank body 310 may include a lower end cover 313. The lower end cover 313 is connected to the bottom end of the cylinder body 311 and is used to close the bottom end of the cylinder body 311.

[0259] The gas-liquid separator 16 may include a base 314. The base 314 is connected to the bottom end of the lower end cover 313 and is used for fixed connection with the housing of the outdoor unit 10.

[0260] In some embodiments, the gas-liquid separator 16 may include an inlet pipe 320 for supplying refrigerant into the tank 310. The inlet pipe 320 extends through the tank 310.

[0261] A portion of the air intake pipe 320 is located outside the tank body 310, and a portion of the air intake pipe 320 extends into the tank body 310.

[0262] The external port of the intake pipe 320 is the inlet 320a of the gas-liquid separator 16, which is used to supply refrigerant.

[0263] refer to Figure 12 The port of the inlet pipe 320 that extends into the tank 310 is the outlet 320b of the inlet pipe 320, which is used to allow refrigerant to flow out into the tank 310.

[0264] The gas-liquid separator 16 may include an outlet pipe 330 for allowing refrigerant to flow out of the tank 310. The outlet pipe 330 extends through the tank 310.

[0265] Most of the vent pipe 330 is located inside the tank 310, and one end of the vent pipe 330 extends outside the tank 310.

[0266] The port of the outlet pipe 330 located inside the tank 310 is the refrigerant suction port, which is used to allow gaseous refrigerant to flow into the outlet pipe 330; the port of the outlet pipe 330 exposed outside the tank 310 is the outlet 330b of the gas-liquid separator 16, which is used to allow gaseous refrigerant to flow out of the gas-liquid separator 16.

[0267] In this embodiment, the four-way valve 15 is connected to the inlet 320a of the gas-liquid separator 16, and the outlet 330b of the gas-liquid separator 16 is connected to the suction port of the compressor 14.

[0268] In some embodiments, reference Figure 14 The vent pipe 330 is U-shaped, and both ports of the vent pipe 330 are located at the top.

[0269] The gas-liquid mixture of refrigerant flows into the tank 310 along the inlet pipe 320. The liquid refrigerant is heavier and settles at the bottom of the tank 310, while the gaseous refrigerant flows out of the gas-liquid separator 16 along the outlet pipe 330, thereby achieving gas-liquid separation of the refrigerant.

[0270] In some embodiments, referring to 14, the gas-liquid separator 16 may include a covering device 400. The covering device 400 is connected inside the gas-liquid separator 16 and is used to cover the refrigerant suction port when there is a large amount of liquid refrigerant inside the gas-liquid separator 16, thereby obstructing the suction flow and reducing the low-pressure, so as to reduce the amount of liquid refrigerant returning to the compressor through the outlet pipe 330, and avoid excessive liquid refrigerant flowing to the compressor and causing compressor damage.

[0271] In some embodiments, the covering device 400 is rotatably connected within the gas-liquid separator 16. When there is a large amount of liquid refrigerant, for example, when the liquid level reaches a warning level, the covering device 400 rotates to cover the refrigerant suction port (e.g., when the liquid level reaches a warning level). Figure 17 (As shown); when the liquid refrigerant in the gas-liquid separator 16 is low and the liquid level is normal, the cover device 400 is in the open state with the refrigerant suction port open (as shown). Figure 16 (As shown).

[0272] In the embodiments of this application, the covering device 400 has an open state and a covered state. When the liquid level in the gas-liquid separator 16 is low, the covering device 400 is in the open state with the refrigerant suction port open, which does not affect the normal function of the gas-liquid separator 16; when the liquid level in the gas-liquid separator 16 is high, the covering device 400 rotates from the open state to the covered state to reduce liquid return.

[0273] In some embodiments, the covering device 400 includes a support plate 410. The support plate 410 is rotatably connected to the cylinder 311, or the support plate 410 is rotatably connected to the air outlet pipe 330.

[0274] The rotation center line A of the support plate 410 is set horizontally so that the support plate 410 can rotate vertically.

[0275] When the support plate 410 rotates in the first direction, it moves toward the refrigerant suction port to cover the refrigerant suction port; when the support plate 410 rotates in the second direction, it moves away from the refrigerant suction port to open the refrigerant suction port.

[0276] refer to Figure 15 The covering device 400 includes a float 420. The float 420 may be spherical to facilitate its floating on the liquid surface. The float 420 is connected to a support plate 410 and is used to rotate the support plate 410 when the liquid level in the gas-liquid separator 16 is high.

[0277] When the liquid level in the gas-liquid separator 16 is lower than the position of the float 420, the float 420 is not subject to the buoyancy of the liquid, and the support plate 410 and the float 420 are in a fully open state under their own weight.

[0278] When the liquid level in the gas-liquid separator 16 reaches the float 420 and the liquid level continues to rise, the float 420 rises with the liquid level, causing the support plate 410 to rotate in the first direction; when the liquid level drops, the position of the float 420 drops, causing the support plate 410 to rotate in the second direction opposite to the first direction.

[0279] In some embodiments, a filter screen is provided inside the air outlet pipe 330 near the air inlet 330a.

[0280] When liquid passes through the filter, due to the large size of the droplets, a thin film forms on the surface of the filter medium based on the principle of surface tension. This film prevents the droplets from passing through the filter. After passing through the filter, the liquid content in the refrigerant is reduced, and the gas becomes purer, which can improve the efficiency of gas-liquid separation.

[0281] In addition, the filter screen's ability to block liquid can prevent a large amount of liquid from rapidly returning to the compressor, thus slowing down the liquid inlet rate and suppressing excessive liquid refrigerant from returning to the compressor and affecting liquid slugging.

[0282] refer to Figure 13 A filter 500 is connected to the air outlet 330 near the air inlet 330a.

[0283] In some embodiments, when the support plate 410 covers the refrigerant suction port, the height of the float 420 is lower than the refrigerant suction port. That is, the refrigerant suction port is covered before the liquid level in the gas-liquid separator 16 reaches the refrigerant suction port, which can prevent liquid backflow in advance and improve reliability.

[0284] Since the low-pressure will decrease when the cover 413 covers the refrigerant suction port, the risk of liquid return can be judged by detecting the low-pressure.

[0285] In some embodiments, the upper part of the support plate 410 is a cover 413. The cover 413 is used to open or cover the refrigerant suction port.

[0286] The float 420 is connected to the lower part of the support plate 410. In the height direction, the float 420 is located below the rotation center line A of the support plate 410, and the cover 413 is located above the rotation center line A of the support plate 410. Thus, during the rotation of the support plate 410, the cover 413 and the float 420 move in opposite directions in the height direction.

[0287] When the float 420 rises, it can drive the support plate 410 to rotate in the first direction, and the cover 430 is lowered; when the float 420 falls, the support plate 410 rotates in the second direction, and the cover 430 is raised.

[0288] In some embodiments, when the covering device 400 is in the fully open state, the float 420 abuts against the vent pipe 330. Thus, due to the obstruction of the vent pipe 330, the float 420 can only drive the support plate 410 to rotate in the first direction when it rises.

[0289] In some embodiments, the cover 430 is provided with a plurality of microholes 431. When the cover 430 covers the air intake 330a, the microholes 431 are connected to the air outlet 330.

[0290] By providing micropores 431 on the cover 430, the drastic pressure change caused by the complete closure of the suction port 330a can be prevented. Part of the refrigerant can be throttled and vaporized after passing through the micropores 431.

[0291] In some embodiments, refer to Figure 8 and Figure 9A through hole 331 is provided on the outlet pipe 330 near the suction port 330a. When the liquid level reaches the through hole 331, it can enter the outlet pipe 330 through the through hole 331, which can play a buffering role and slow down the problem of liquid refrigerant level rising and rapid liquid return.

[0292] When the liquid level reaches the highest position of the float 420, the cover 413 covers the refrigerant suction port 430. At this time, the liquid level has not yet risen to the height of the refrigerant suction port. The system can detect the change in suction pressure (the low pressure detected by the low pressure sensor is the suction pressure) and judge in advance that there is a risk of liquid return, thereby controlling the opening of the expansion valve.

[0293] Specifically, when the air conditioner is running stably, the controller 30 is configured as follows:

[0294] Obtain the low-pressure change value within a preset time period;

[0295] Adjusting the opening of the expansion valve or controlling the air conditioner to stop based on changes in low-pressure value.

[0296] In this embodiment, the opening of the expansion valve is adjusted according to the change in low pressure, i.e., the change in pressure at the suction port, to change the state of the refrigerant entering the compressor 14, thereby preventing liquid refrigerant from flowing into the compressor 14 and reducing liquid return.

[0297] In some embodiments, the controller 30 is configured to:

[0298] Determine whether the low-pressure change value is not less than the eleventh preset value K. If yes, perform multiple checks and if the low-pressure change value is still not less than the eleventh preset value K, then control the air conditioner to stop. If no, perform the first check: whether the low-pressure change value is not less than the twelfth preset value L.

[0299] In the first judgment, if yes, the opening degree of the expansion valve is reduced by m; if no, the second judgment is made: whether the change value of the low pressure is not less than the thirteenth preset value M.

[0300] In the second judgment, if yes, the opening degree of the expansion valve is reduced by n, where n < m; if no, the third judgment is made: whether the change value of the low pressure is not less than the fourteenth preset value N.

[0301] In the third judgment, if yes, then the opening degree of the expansion valve remains unchanged.

[0302] By detecting changes in low-pressure value and controlling the air conditioner to shut down when the low-pressure change is significant, liquid refrigerant can be effectively prevented from flowing back into compressor 14, thus preventing liquid return. When the low-pressure change is small, the opening of the expansion valve is adjusted to reduce the amount of refrigerant entering the float-type gas-liquid separator 16, avoiding liquid return caused by excessive refrigerant failing to vaporize effectively.

[0303] In this embodiment, reference Figure 18 The system acquires the frequency change value of compressor 14 and the opening change value of expansion valve within a preset time period. If the frequency change value of compressor 14 does not exceed the fifteenth preset value Y and the opening change value of expansion valve does not exceed the sixteenth preset value Z, the system is considered to be operating stably without change, i.e., the air conditioner is operating stably. If the air conditioner does not meet the stable operation conditions, the above-mentioned control of the opening of expansion valve based on the low-pressure change value will not be implemented.

[0304] For example, the preset time period is 20 seconds. The eleventh preset value K can be 0.1MPa, the twelfth preset value L can be 0.06MPa, the thirteenth preset value M can be 0.04MPa, the fourteenth preset value N can be 0.03MPa, the fifteenth preset value Y can be 2Hz, the sixteenth preset value Z can be 1%, m can be 40%, and n can be 20%.

[0305] refer to Figure 19 The frequency change of compressor 14 is detected 20 seconds before and after the change. Simultaneously, the opening degree (EVO) of the expansion valve is detected 20 seconds before and after the change. If H(20s before) - H(20s after) ≤ 2Hz and EVO(20s before) - EVO(20s after) ≤ 1%, the air conditioner operates stably. At this point, it is determined whether the low-pressure change satisfies Ps(20s before) - Ps(20s before) ≥ 0.1MPa. If so, multiple checks are performed. If Ps(20s before) - Ps(20s before) ≥ 0.1MPa, the air conditioner is shut down. If not, the first check is performed: whether the low-pressure change satisfies Ps(20s before) - Ps(20s before) ≥ 0.06MPa.

[0306] In the first judgment, if yes, then the opening degree of the expansion valve is reduced by m; if no, then the second judgment is made: whether the change value of the low pressure satisfies Ps(20s ago) - Ps(20s ago) ≥ 0.04MPa.

[0307] In the second judgment, if yes, the opening of the expansion valve is reduced by n; if no, the third judgment is made: whether the change in low pressure satisfies Ps(20s ago) - Ps(20s ago) ≥ 0.03MPa.

[0308] In the third judgment, if yes, the opening of the expansion valve remains unchanged; if no, the air conditioner is re-judged to determine whether it is operating stably.

[0309] It should be noted that since the low pressure changes significantly when the compressor 14 and expansion valve are not operating, it indicates that there is a blockage in the circulation loop of the gas-liquid separator 16. This is considered to mean that the inner float 420 in the gas-liquid separator 16 has closed the pipeline, indicating that the float 420 has risen and the liquid level is high enough to meet the requirements for preventing backflow during shutdown.

[0310] When the low-pressure change is small, it is necessary to adjust the opening of the expansion valve. At different heights of the float 420, the airflow is obstructed, causing changes in the low-pressure. The opening of the expansion valve can be adjusted to reduce the amount of refrigerant entering the gas-liquid separator 16.

[0311] In this embodiment, the indoor unit 20 may include an indoor expansion valve 23, which reduces the pressure of the refrigerant supplied to the indoor heat exchanger 211 in cooling mode. The outdoor unit 10 may include an outdoor expansion valve 13, which reduces the pressure of the refrigerant supplied to the outdoor heat exchanger of the outdoor unit 100, thereby lowering the temperature of the refrigerant.

[0312] It should be noted that if the air conditioner includes the aforementioned indoor expansion valve 23 and outdoor expansion valve 13, in the above embodiments, in cooling mode, controlling the opening degree of the expansion valve is equivalent to adjusting the opening degree of the indoor expansion valve 23; in heating mode, controlling the opening degree of the expansion valve is equivalent to adjusting the opening degree of the outdoor expansion valve 13. For example, refer to... Figure 20 , Figure 21 .

[0313] This application can effectively solve the problem of excessive liquid return caused by expansion valve control fluctuations when the exhaust superheat of a multi-split air conditioner is low during low-temperature cooling; and the problem of liquid slugging and compressor damage caused by liquid refrigerant filling the gas-liquid separator during low-temperature heating sleep start-up and after severe defrosting.

[0314] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

[0315] For ease of explanation, the above description has been provided in conjunction with specific embodiments. However, the above exemplary discussion is not intended to be exhaustive or to limit the embodiments to the specific forms disclosed above. Various modifications and variations can be obtained based on the above teachings. The selection and description of the above embodiments are for the purpose of better explaining the principles and practical applications, thereby enabling those skilled in the art to better utilize the described embodiments and various different variations of embodiments suitable for specific use considerations.

Claims

1. An air conditioner, characterized in that, include: The refrigerant circulation loop, in which the refrigerant circulates sequentially through the compressor, condenser, expansion valve, and evaporator, wherein one of the condenser and the evaporator is an outdoor heat exchanger and the other is an indoor heat exchanger; A pressure detection device is used to detect the pressure data of the compressor in real time; A temperature detection device is used to detect the suction temperature of the compressor in real time; The controller is configured to operate during the start-up and transition phases of the air conditioner. Obtain the suction superheat of the compressor; The refrigerant density ρ in the suction pipe is calculated based on the dynamic pressure at the suction port in the pressure data. The suction dryness of the compressor is calculated based on the refrigerant density ρ and refrigerant properties in the suction pipe. The compressor is judged to have a risk of liquid slugging based on the suction superheat and suction dryness. If there is no risk of liquid slugging, the opening of the expansion valve is adjusted according to the preset control logic; if there is a risk of liquid slugging, the level of liquid slugging risk is determined. If the liquid hammer risk level is level one, then control the opening of the expansion valve to decrease to the first opening degree; If the liquid hammer risk level is level two, then control the opening of the expansion valve to decrease to the second opening degree; If the liquid slugging risk level is level three, then control the air conditioner to shut down; Wherein, the return liquid volume of the third level is greater than that of the second level, the return liquid volume of the second level is greater than that of the first level, and the first opening degree is greater than that of the second opening degree.

2. The air conditioner according to claim 1, characterized in that, The controller is configured to: If the intake superheat is not less than the first preset value A, or the intake dryness exceeds the second preset value B, then it is determined that the compressor does not have a risk of liquid slugging. If the superheat of the intake air is less than the first preset value A and not less than the fourth preset value W, or if the dryness of the intake air is not greater than the second preset value B, it is determined whether the dryness of the intake air is not less than the third preset value C. If so, the liquid hammer risk level is determined to be the first level, and the opening of the expansion valve is controlled to be reduced to the first opening. If not, the liquid hammer risk level is determined to be the second level, and the opening degree of the expansion valve is controlled to decrease Q to the second opening degree; If the superheat of the intake air is less than the fourth preset value W, it is determined whether the dryness of the intake air exceeds the preset threshold D. If yes, the liquid slugging risk level is determined to be the second level, and the opening of the expansion valve is controlled to decrease to the second opening. If no, the liquid slugging risk level is determined to be the third level, and the air conditioner is controlled to stop. Wherein, the preset threshold D < the third preset value C.

3. The air conditioner according to claim 1 or 2, characterized in that, The temperature detection device is also used to detect the discharge temperature of the compressor in real time, and the controller is configured to: During the stable operation phase of the air conditioner, the intake superheat, the change in intake superheat, the exhaust superheat, and the change in exhaust superheat are obtained. The presence of liquid slugging risk in the compressor is determined based on the intake superheat and its change or the exhaust superheat and its change. If there is no risk of liquid slugging, the opening of the expansion valve is adjusted according to the preset control logic; if there is a risk of liquid slugging, the liquid slugging risk level of the compressor is determined. If the liquid hammer risk level is the first level, then control the opening degree of the expansion valve to decrease by P; If the liquid hammer risk level is the second level, then control the opening of the expansion valve to decrease by Q, where Q > P; If the liquid slugging risk level is the third level, then the air conditioner is shut down.

4. The air conditioner according to claim 3, characterized in that, The controller is configured to: If the intake superheat is not less than the first preset value A, it is determined that the compressor does not have a risk of liquid slugging, and the opening of the expansion valve is adjusted according to the preset control logic. If the intake superheat is greater than the fifth preset value E and less than the first preset value A, then determine whether the change in intake superheat is not less than the fourth preset value W; if yes, then determine that the liquid hammer risk level is the first level, and at this time control the opening of the expansion valve to decrease by P; if no, then determine that the liquid hammer risk level is the second level, and at this time control the opening of the expansion valve to decrease by Q. If the intake superheat is greater than the sixth preset value F and not greater than the fifth preset value E, then the liquid hammer risk level is determined to be the second level, and the opening of the expansion valve is controlled to decrease by Q. If the intake superheat is not greater than the sixth preset value F, the liquid slugging risk level is determined to be level three, and the air conditioner is controlled to shut down.

5. The air conditioner according to claim 3, characterized in that, The controller is configured to: If the exhaust superheat is not less than the seventh preset value G, it is determined that the compressor does not have a risk of liquid slugging. At this time, the opening of the expansion valve is adjusted according to the preset control logic. If the exhaust superheat is greater than the eighth preset value H and less than the seventh preset value G, then determine whether the change in exhaust superheat is not less than the fourth preset value W; if yes, then determine that the liquid hammer risk level is the first level, and at this time control the opening of the expansion valve to decrease by P; if no, then determine that the liquid hammer risk level is the second level, and at this time control the opening of the expansion valve to decrease by Q. If the exhaust superheat is greater than the ninth preset value I and not greater than the eighth preset value H, then the liquid hammer risk level is determined to be the second level, and the opening of the expansion valve is controlled to decrease by Q. If the exhaust superheat is not greater than the ninth preset value I, the liquid slugging risk level is determined to be level three, and the air conditioner is controlled to stop.

6. The air conditioner according to claim 1 or 3, characterized in that, The temperature detection device is also used to detect the discharge temperature of the compressor in real time, and the controller is configured to: During the stable operation phase of the air conditioner, the exhaust superheat and intake superheat of the compressor are obtained; Based on the exhaust superheat and intake superheat, determine whether the compressor has a risk of liquid slugging; If there is no risk of liquid slugging, the opening of the expansion valve is adjusted according to the preset control logic; if there is a risk of liquid slugging, the liquid slugging risk level of the compressor is determined. If the liquid hammer risk level is the first level, then control the opening degree of the expansion valve to decrease by P; If the liquid hammer risk level is the second level, then control the opening degree of the expansion valve to decrease by Q, P < Q; If the liquid slugging risk level is the third level, then the air conditioner is shut down.

7. The air conditioner according to claim 6, characterized in that, The controller is configured to: If the exhaust superheat is not less than the seventh preset value G, it is determined that the compressor does not have a risk of liquid slugging. At this time, the opening of the expansion valve is adjusted according to the preset control logic. If the exhaust superheat is greater than the tenth preset value J and less than the seventh preset value G, then determine whether the intake superheat is not less than the first preset value A. If yes, the liquid hammer risk level is determined to be Level 1, and the opening degree of the expansion valve is reduced by P; if no, the liquid hammer risk level is determined to be Level 2, and the opening degree of the expansion valve is reduced by Q. If the exhaust superheat is not greater than the tenth preset value J, then the change in the intake superheat is obtained and it is determined whether it is not less than the fourth preset value W; if so, then the liquid slugging risk level is determined to be the second level, and at this time, the opening of the expansion valve is controlled to decrease Q; if not, then the liquid slugging risk level is determined to be the third level, and at this time, the air conditioner is controlled to stop.

8. The air conditioner according to claim 1, characterized in that, The refrigerant circulation loop also includes a float-type gas-liquid separator connected in series between the compressor's suction port and the evaporator's outlet, the pressure data includes low-pressure, and the controller is configured to: When the air conditioner is running stably, the low-pressure change value is obtained within a preset time period; The opening degree of the expansion valve is adjusted according to the low-pressure change value.

9. The air conditioner according to claim 8, characterized in that, The controller is configured to: Determine whether the low-pressure change value is not less than the eleventh preset value K. If yes, perform multiple determinations and if the result is still yes, control the air conditioner to stop. If no, perform the first determination: whether the low-pressure change value is not less than the twelfth preset value L. In the first judgment, if yes, then control the opening degree of the expansion valve to decrease by m; if no, then perform the second judgment: whether the low pressure change value is not less than the thirteenth preset value M. In the second judgment, if yes, then control the opening degree of the expansion valve to decrease by n, n < m; if no, then perform the third judgment: whether the low pressure change value is not less than the fourteenth preset value N. If the third determination is true, then the opening degree of the expansion valve remains unchanged.

10. An air conditioner, characterized in that, include: The refrigerant circulation loop, in which the refrigerant circulates sequentially through the compressor, condenser, expansion valve, and evaporator, wherein one of the condenser and the evaporator is an outdoor heat exchanger and the other is an indoor heat exchanger; A pressure detection device is used to detect the pressure data of the compressor in real time; A temperature detection device is used to detect the suction temperature of the compressor in real time; The controller is configured to operate during the start-up and transition phases of the air conditioner. Obtain the suction superheat of the compressor; The refrigerant density ρ in the suction pipe is calculated based on the dynamic pressure of the suction port in the pressure data, and the suction dryness of the compressor is calculated based on the refrigerant density ρ in the suction pipe and the refrigerant physical property parameters. The presence and level of liquid slugging risk in the compressor are determined based on the intake superheat and intake dryness. If there is no risk of liquid slugging, the opening degree of the expansion valve is adjusted according to the preset control logic; If the liquid slugging risk level is level three, then control the air conditioner to shut down; If the liquid hammer risk level is level two, then control the opening degree of the expansion valve to decrease by Q; If the liquid hammer risk level is level one, then control the opening degree of the expansion valve to decrease by P; Where P < Q, the return volume of the third level is greater than the return volume of the second level, and the return volume of the second level is greater than the return volume of the first level.

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