Methods for determining the oil level in a compressor and air conditioning systems

Abstract

This invention provides a method for determining the oil level of a compressor and an air conditioning system. The compressor has an oil sump, and a throttling element and a liquid temperature sensor are sequentially installed at the outlet of the oil sump. The liquid temperature sensor is used to measure the temperature Tk of the fluid flowing out of the oil sump after being throttled by the throttling element. The method includes: acquiring the compressor's high-pressure Ph, low-pressure Ps, discharge temperature Tp, and fluid temperature Tk; determining the compression ratio Px based on the high-pressure Ph and low-pressure Ps; calculating the predicted oil temperature Tkcal of the compressor based on the compression ratio Px, discharge temperature Tp, and low-pressure Ps; calculating the difference ΔT between the predicted oil temperature Tkcal and the fluid temperature Tk, and comparing the difference ΔT with preset dynamic parameters; and determining whether the compressor's oil level is qualified based on the comparison result of the difference ΔT and the dynamic parameters. The control method of this application is simple, convenient, reduces manual intervention, and has high accuracy.

Description

Technical Field

[0001] This invention relates to the field of air conditioning, specifically to a method for determining the oil level of a compressor and an air conditioning system. Background Technology

[0002] During the operation of a refrigeration system, the following methods are used to determine the oil level inside the compressor: visually observing the oil level through the sight glass on the compressor; judging the oil level by analyzing the compressor's operating parameters, primarily suction and discharge pressures and temperatures; and determining the oil level by detecting the refrigerant flow rate at the low-pressure gas-liquid separator outlet. However, these methods are subject to various influences, resulting in inaccurate judgments. Furthermore, interpreting parameters such as temperature and pressure requires relevant experience and professional knowledge, making it a relatively difficult skill to master; the interpretation of these parameters is influenced by individual experience and understanding of professional knowledge, and incorrect interpretation can lead to misjudgments of the oil level. Summary of the Invention

[0003] To address the above problems, this invention provides a method for determining the oil level of a compressor and an air conditioning system. By comparing the difference between the predicted oil temperature and the fluid temperature, it is possible to determine whether the oil level in the oil sump is normal. This method is simple, convenient, and reduces the need for manual intervention. The predicted oil temperature is related to the compressor's high pressure, low pressure, and exhaust temperature, and these parameters are all obtained directly from the compressor and used to predict the compressor's oil temperature, thus improving the accuracy of the predicted oil temperature and improving the accuracy of oil level determination.

[0004] This invention provides a method for determining the oil level of a compressor. The compressor has an oil sump, and a throttling element and a liquid temperature sensor are sequentially installed at the outlet of the oil sump. The liquid temperature sensor is used to measure the temperature Tk of the fluid flowing out of the oil sump after being throttled by the throttling element. The oil level determination method includes:

[0005] Parameter acquisition steps: Obtain the compressor's high pressure Ph, low pressure Ps, exhaust temperature Tp, and fluid temperature Tk;

[0006] Data processing steps: Determine the compressor compression ratio Px based on the high pressure Ph and low pressure Ps, and calculate the compressor's predicted oil temperature Tkcal based on the compression ratio Px, exhaust temperature Tp, and low pressure Ps.

[0007] Calculate the difference ΔT between the predicted oil temperature Tkcal and the fluid temperature Tk, and compare the difference ΔT with the preset dynamic parameters;

[0008] Judgment steps: Determine whether the compressor oil level is qualified based on the comparison result of the difference △T and the dynamic parameters.

[0009] According to this technical solution, if the fluid at the oil sump outlet contains refrigerant, the refrigerant evaporates after passing through the throttling element, causing the fluid temperature to decrease. The higher the refrigerant content in the fluid, the lower the fluid temperature after throttling. By comparing the difference between the predicted oil temperature and the fluid temperature, the oil content in the oil sump can be obtained. Specifically, the larger the difference, the lower the fluid temperature after throttling, the more heat is carried away by the refrigerant evaporation, and the relatively high refrigerant content in the fluid, meaning the compressor may be short of oil. Furthermore, after the fluid passes through the throttling element, the temperature change is larger and less affected by factors such as ambient temperature, improving the accuracy of the liquid temperature sensor's detection results. However, if the fluid flowing out of the oil outlet contains little refrigerant and little oil, the compressor will experience dry running, leading to an increase in exhaust temperature and a corresponding increase in the predicted oil temperature. Since almost no fluid flows through the throttling element, the temperature detected by the liquid temperature sensor is slightly higher than the ambient temperature, and the difference between the predicted oil temperature and the fluid temperature Tk remains large, still accurately indicating that the compressor is short of oil.

[0010] Furthermore, the predicted oil temperature is related to the compressor's high-pressure, low-pressure, and exhaust temperature, all of which are directly obtained from the compressor and used to predict the compressor's oil temperature. Timely parameter acquisition improves the accuracy of the predicted oil temperature. Moreover, this predicted oil temperature can be obtained without professional interpretation of temperature, pressure, and other parameters, avoiding misjudgments caused by incorrect interpretation, improving the accuracy of oil level assessment, reducing misjudgments, and ensuring timely protection when oil is low. Simultaneously, the predicted oil temperature can be automatically calculated by the air conditioning system without human intervention, simplifying the oil level determination process.

[0011] In the optional technical solution of the present invention, the predicted oil temperature Tkcal = A·Ps + B·Tp + C·Px, where A, B, and C are all preset constants, and Px = (Ph + 0.1) / (Ps + 0.1).

[0012] According to this technical solution, by operating the air conditioning system and based on historical data such as the compressor's exhaust temperature, low-pressure, compression ratio, and corresponding oil temperature, the above-mentioned formula for predicting oil temperature is obtained through linear regression fitting. All of these parameters are obtained directly from the compressor and are used to predict the compressor's oil temperature, which helps improve the accuracy of the predicted oil temperature results.

[0013] In an optional technical solution of the present invention, in the data processing step, the dynamic parameter = D + α + β + γ; wherein,

[0014] D, α, β, and γ are all constants; α is related to exhaust superheat; β is related to outdoor ambient temperature; and γ is related to compression ratio Px.

[0015] According to this technical solution, the dynamic parameters can be dynamically adjusted according to changes in compressor exhaust superheat, outdoor ambient temperature, and compression ratio. This allows the predicted difference between oil temperature and fluid temperature under different operating conditions to be compared with the matching dynamic parameters, enabling dynamic judgment of the oil level in the compressor and improving the accuracy of oil level judgment.

[0016] In the optional technical solutions of the present invention, -13≤α≤0; -7≤β≤2; -6≤γ≤-2.

[0017] According to this technical solution, by setting reasonable ranges for α, β, and γ values, the accuracy of the oil temperature prediction calculation can be improved, thereby improving the accuracy of oil level judgment and enabling timely action to protect the compressor operation when there is a shortage of oil.

[0018] In an optional technical solution of the present invention, the determination of the compressor oil level in the judgment step, based on the comparison result of the difference ΔT and the dynamic parameters, includes:

[0019] If the difference ΔT < the first dynamic parameter, then the compressor oil level is normal.

[0020] If the difference ΔT ≥ the first dynamic parameter and the difference ΔT ≥ the second dynamic parameter, then the compressor is short of oil.

[0021] If the difference ΔT ≥ the first dynamic parameter and the difference ΔT < the second dynamic parameter, then the compressor oil level is normal; the D values ​​in the first dynamic parameter and the second dynamic parameter are different, and the D value in the first dynamic parameter is less than the D value in the second dynamic parameter.

[0022] According to this technical solution, by comparing the difference ΔT with the first dynamic parameter and the second dynamic parameter to determine the oil level, the occurrence of misjudgment can be reduced and the accuracy of oil level determination can be improved.

[0023] In an optional technical solution of the present invention, the compressor includes:

[0024] The exhaust pipe is connected to the compressor's exhaust port. A high-pressure sensor is installed on the exhaust pipe to detect the high pressure of the refrigerant flowing out of the exhaust port.

[0025] The return gas line is connected to the return gas port of the compressor. A low-pressure sensor is installed on the return gas line to detect the low pressure of the refrigerant flowing out of the return gas port.

[0026] The temperature measuring pipeline is connected between the oil outlet of the oil tank and the return gas pipeline. The throttling element and the liquid temperature sensor are located in the temperature measuring pipeline, and the liquid temperature sensor and the return gas pipeline are separated.

[0027] According to this technical solution, by measuring the high-pressure at the compressor's exhaust port and the low-pressure at the return port, and combining the effects of these pressures on oil temperature, the oil temperature can be predicted, thus improving the accuracy of the predicted oil temperature. The fluid flowing out of the oil outlet, after throttling and temperature measurement, can return to the compressor's return port via the return gas pipeline and flow to the internal components of the compressor, maintaining the normal operation of compressor 1. Furthermore, the liquid temperature sensor is separated from the return gas pipeline, which reduces the influence of the return gas pipeline temperature on the liquid temperature sensor's measurement results, improving the accuracy of the liquid temperature sensor's detection results. By improving the accuracy of the liquid temperature sensor's measurement results and the predicted oil temperature, the accuracy of oil level judgment can be improved.

[0028] In an optional technical solution of the present invention, the throttling element is a capillary tube, the length of the throttling element is 1-1.5m, and the diameter of the throttling element is 6-10mm.

[0029] According to this technical solution, excessively long capillary tubes increase flow resistance, hindering fluid flow within the tube. Furthermore, excessively long capillary tubes cause more heat exchange between the fluid and the external environment, especially at low temperatures, significantly impacting the liquid temperature sensor's readings. Conversely, excessively short capillary tubes result in incomplete refrigerant throttling at the oil sump outlet, leaving liquid refrigerant flowing past the temperature sensor and leading to a lower detected temperature, affecting the assessment of the compressor's oil level. By appropriately controlling the length of the throttling element, complete refrigerant throttling can be ensured, preventing excessive heat exchange between the fluid and the external environment and improving the accuracy of oil temperature detection. Furthermore, appropriately controlling the capillary tube diameter avoids problems such as poor oil return due to excessively small diameters and insufficient oil return due to excessively large diameters. This diameter range also offers significant advantages in terms of structural stability, seismic resistance, and cost control.

[0030] In an optional technical solution of the present invention, a fixing block is also included for fixing the temperature measuring pipeline between the liquid temperature sensor and the return gas pipeline. The fixing block is a heat-insulating fixing block.

[0031] According to this technical solution, the fixing block prevents the capillary tube from breaking due to vibrations generated during the operation of the air conditioner's outdoor unit. Simultaneously, the fixing block's position before the liquid temperature sensor protects it from vibration to some extent, reducing the impact of vibration on the sensor's detection results and improving accuracy. Furthermore, the heat-insulating fixing block prevents the temperature of the return gas line from affecting the liquid temperature sensor's detection results through heat transfer, further improving the accuracy of the sensor's readings.

[0032] In an optional technical solution of the present invention, a filter is also included, disposed between the oil outlet and the throttling element.

[0033] According to this technical solution, the filter can filter the fluid at the oil tank outlet, improve the cleanliness of the fluid, prevent the fluid from becoming clogged when it enters the throttling element, and improve the accuracy of oil temperature measurement results.

[0034] The present invention also provides an air conditioning system, wherein the oil level is determined by the compressor described above. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the compressor in an embodiment of the present invention.

[0036] Figure 2 This is a flowchart illustrating the oil level determination method for the compressor in an embodiment of the present invention.

[0037] Figure 3 This is a flowchart illustrating the determination step in an embodiment of the present invention.

[0038] Figure label:

[0039] Compressor 1; Throttling element 11; Liquid temperature sensor 12; Exhaust pipe 13; Return pipe 14; Temperature measuring pipe 15; Fixing block 16; Filter 17. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0041] like Figure 1 , Figure 2 As shown, the present invention provides a method for determining the oil level of a compressor 1. The compressor 1 has an oil sump, and a throttling element 11 and a liquid temperature sensor 12 are sequentially provided at the outlet of the oil sump (not shown in the figure). The liquid temperature sensor 12 is used to measure the fluid temperature Tk of the fluid flowing out of the oil outlet of the oil sump after being throttled by the throttling element 11. The oil level determination method includes:

[0042] Parameter acquisition steps: Obtain the high pressure Ph, low pressure Ps, exhaust temperature Tp, and fluid temperature Tk of compressor 1;

[0043] Data processing steps: Determine the compressor's compression ratio Px based on the high pressure Ph and low pressure Ps. Calculate the predicted oil temperature Tkcal for compressor 1 based on the compression ratio Px, exhaust temperature Tp, and low pressure Ps.

[0044] Calculate the difference ΔT between the predicted oil temperature Tkcal and the fluid temperature Tk, and compare the difference ΔT with the preset dynamic parameters;

[0045] Judgment steps: Determine whether the oil level of compressor 1 is qualified based on the comparison results of the difference △T and the dynamic parameters.

[0046] In this way, if the fluid at the oil sump outlet contains refrigerant, the refrigerant evaporates after being throttled by the throttling element 11, causing the fluid temperature Tk to decrease. The higher the refrigerant content in the fluid, the lower the fluid temperature Tk after throttling. By comparing the difference between the predicted oil temperature Tkcal and the fluid temperature Tk, the oil content in the oil sump can be obtained. Specifically, the larger the difference, the lower the fluid temperature Tk after throttling, the more heat is carried away by the refrigerant evaporation, and the relatively high refrigerant content in the fluid, meaning that compressor 1 may be short of oil. Furthermore, after the fluid is throttled by the throttling element 11, the temperature change is larger and less affected by factors such as ambient temperature, improving the accuracy of oil temperature detection. If the fluid flowing out of the oil outlet contains little refrigerant and little oil, the compressor 11 will experience dry running, leading to an increase in exhaust temperature and a corresponding increase in the predicted oil temperature Tkcal. Since almost no fluid flows through the throttling element, the temperature detected by the liquid temperature sensor 12 will be slightly higher than the ambient temperature. Therefore, the difference between the predicted oil temperature Tkcal and the fluid temperature TkTk will still be large, and the compressor will still be able to accurately determine that it is short of oil.

[0047] The predicted oil temperature Tkcal is related to the high-pressure, low-pressure, and exhaust temperature of compressor 1, and these parameters are all directly obtained from compressor 1 and used to predict the oil temperature of compressor 1. This helps improve the accuracy of the predicted oil temperature Tkcal result. Furthermore, obtaining the predicted oil temperature Tkcal does not require professional interpretation of parameters such as temperature and pressure, avoiding misjudgments of oil level caused by incorrect interpretation, thus improving the accuracy of oil level judgment and reducing the occurrence of misjudgments. At the same time, the calculation of the predicted oil temperature Tkcal can be automatically performed by the air conditioning system without human intervention, simplifying the oil level determination process.

[0048] In a preferred embodiment of the present invention, the predicted oil temperature Tkcal = A·Ps + B·Tp + C·Px, where A, B, and C are all preset constants, Px = (Ph + 0.1) / (Ps + 0.1), Ph is the gauge pressure, Ph + 0.1 represents the absolute high pressure, and Ps is the gauge pressure, Ps + 0.1 represents the absolute low pressure.

[0049] By operating the air conditioning system and using historical data such as the exhaust temperature, low-pressure, compression ratio, and corresponding oil temperature of compressor 1, the above-mentioned formula for predicting the oil temperature Tkcal is obtained through linear regression fitting. All the parameters mentioned above are directly obtained from compressor 1 and are used to predict the oil temperature of compressor 1, which helps improve the accuracy of the predicted oil temperature Tkcal result.

[0050] In this embodiment, the values ​​of A, B, and C are related to the compressor parameters, system structure, and the operating mode of the air conditioning system. Specifically, -10≤A≤0; 0≤B≤5; -10≤C≤0.

[0051] In a preferred embodiment of the present invention, in the data processing step, the dynamic parameter is defined as D + α + β + γ; where D, α, β, and γ are all constants; and D is related to the compressor's own performance, α is related to the exhaust superheat, β is related to the outdoor ambient temperature, and γ is related to the compression ratio Px. The dynamic parameter can be dynamically adjusted according to changes in the compressor 1's exhaust superheat, outdoor ambient temperature, and compression ratio, so that under different operating conditions, the difference between the predicted oil temperature Tkcal and the fluid temperature Tk can be compared with the matching dynamic parameter, thereby dynamically determining the oil level in the compressor 1 and improving the accuracy of oil level determination.

[0052] In a preferred embodiment of the present invention, -13≤α≤0; -7≤β≤2; -6≤γ≤-2. By setting reasonable numerical ranges for α, β, and γ, the accuracy of the predicted oil temperature Tkcal can be improved, thereby improving the accuracy of oil level judgment and enabling timely protection of compressor 1 in case of oil shortage.

[0053] In a preferred embodiment of the present invention, such as Figure 3 As shown, in the judgment step, determining the oil level of compressor 1 based on the comparison result of the difference ΔT and the dynamic parameters includes:

[0054] If the difference ΔT < the first dynamic parameter, then the oil level of compressor 1 is normal.

[0055] If the difference ΔT ≥ the first dynamic parameter and the difference ΔT ≥ the second dynamic parameter, then compressor 1 is short of oil.

[0056] If the difference ΔT ≥ the first dynamic parameter and the difference ΔT < the second dynamic parameter, then the compressor oil level is normal; the D value in the first dynamic parameter is less than the D value in the second dynamic parameter.

[0057] Furthermore, the value range of D in the first dynamic parameter is [5, 25], and the value range of D in the second dynamic parameter is [10, 35]. For example, the value of D in the first dynamic parameter is 10, and the value of D in the second dynamic parameter is 15. In some embodiments, technicians may also adjust the value of D in the first and second dynamic parameters according to actual needs, without being limited thereto, in order to ensure the accuracy of oil level judgment.

[0058] In this embodiment, by setting different D values ​​and comparing the difference with the first dynamic parameter and the second dynamic parameter, misjudgment can be reduced. For example, in some extreme environmental conditions, if the difference ΔT is greater than the first dynamic parameter even before the compressor 11 has started running, further judgment on whether the difference is greater than the second dynamic parameter can avoid misjudgment and improve the accuracy of judgment. In addition, when the fluid temperature Tk detected by the liquid temperature sensor 12 deviates due to environmental factors, pipe heat transfer, etc., if the D values ​​in the first and second dynamic parameters are the same, that is, only one comparison between the difference and the dynamic parameter is performed, it will be judged as oil shortage when the difference ΔT is greater than the dynamic parameter, and as normal when the difference ΔT is not greater than the dynamic parameter. This may result in frequent switching between oil shortage and normal, affecting the operational stability of the air conditioning system. However, in this embodiment, when the difference is within the range between the first and second dynamic parameters, it is judged as normal oil level, which can prevent frequent switching between oil shortage and normal, increase the running time of the compressor 11 in a certain state, and improve the operational stability of the air conditioning system.

[0059] In this embodiment, when compressor 1 is short of oil, the control device of the air conditioning system is configured to issue an oil return command to ensure the normal operation of compressor 1.

[0060] In a preferred embodiment of the present invention, compressor 1 includes:

[0061] The exhaust pipe 13 is connected to the exhaust port of the compressor 1. A high-pressure sensor (not shown in the figure) is installed on the exhaust pipe 13 to detect the high pressure Ph of the refrigerant flowing out of the exhaust port.

[0062] The return gas line 14 is connected to the return gas port of the compressor 1. A low-pressure sensor is installed on the return gas line 14 to detect the low-pressure Ps of the refrigerant flowing out of the return gas port.

[0063] Temperature measuring pipeline 15 is connected between the oil outlet of the oil tank and the return gas pipeline 14. Throttling element 11 and liquid temperature sensor 12 are provided in temperature measuring pipeline 15, and liquid temperature sensor 12 is spaced apart from return gas pipeline 14.

[0064] In this embodiment, by measuring the high-pressure at the exhaust port and the low-pressure at the return port of compressor 1, and combining the influence of the high-pressure and low-pressure on the oil temperature, the predicted oil temperature Tkcal is calculated, which helps to improve the accuracy of the predicted oil temperature Tkcal. The fluid flowing out of the oil outlet, after throttling and temperature measurement, can return to the return port of compressor 1 via the return gas pipeline 14 and flow to the internal components of the compressor, maintaining the normal operation of compressor 1; this condition is short-lived and does not affect the operation of the compressor. Furthermore, the liquid temperature sensor 12 is separated from the return gas pipeline 14, which reduces the influence of the temperature of the return gas pipeline 14 on the measurement results of the liquid temperature sensor 12 (e.g., during heating, frost may form on the return gas pipeline 14, and the frost may extend along the pipe wall to the temperature measuring pipeline 15, affecting the detection results of the liquid temperature sensor 12), thus improving the accuracy of the detection results of the liquid temperature sensor 12. By improving the accuracy of the liquid temperature sensor 12 measurement results and the predicted oil temperature Tkcal, the accuracy of oil level judgment is improved.

[0065] In a preferred embodiment of the present invention, the throttling element 11 is a capillary tube with a length of 1-1.5 m and a diameter of 6-10 mm. Specifically, if the capillary tube is too long, it will increase flow resistance, resulting in poor fluid flow within the capillary tube. Simultaneously, an excessively long capillary tube will cause more heat exchange between the fluid inside the tube and the external environment, especially at low temperatures, significantly impacting the detection results of the liquid temperature sensor 12. If the capillary tube is too short, the refrigerant in the fluid at the oil sump outlet will not be completely throttled, and some liquid refrigerant will still flow through the liquid temperature sensor 12, leading to a lower detected temperature and affecting the judgment of the oil level in the compressor 1. By reasonably controlling the length of the throttling element 11, complete refrigerant throttling can be ensured, avoiding excessive heat exchange between the fluid and the external environment, thus improving the accuracy of the oil temperature detection results. By properly controlling the diameter of the capillary tube, problems such as poor oil return caused by too small a diameter and insufficient oil return caused by too large a diameter can be avoided. Moreover, this diameter range has outstanding advantages in terms of structural stability, seismic resistance, and cost control.

[0066] In a preferred embodiment of the present invention, a fixing block 16 is further included to fix the temperature measuring pipe 15 between the liquid temperature sensor 12 and the return gas pipe 14. The fixing block 16 is a heat-insulating fixing block; such as a resin fixing block, a rubber fixing block, or other fixing blocks with low thermal conductivity. The fixing block 16 can prevent the capillary tube from breaking due to vibration generated during the operation of the air conditioner outdoor unit. At the same time, the fixing block 16 is located before the liquid temperature sensor 12, which protects it from vibration to a certain extent, reduces the impact of vibration on the detection results of the liquid temperature sensor 12, and helps to improve the accuracy of the detection results. In addition, the fixing block 16 with heat insulation properties can prevent the temperature of the return gas pipe 14 from affecting the detection results of the liquid temperature sensor 12 through heat transfer, thereby improving the accuracy of the detection results of the liquid temperature sensor 12.

[0067] In a preferred embodiment of the present invention, a filter 17 is further included, disposed between the oil outlet and the throttling element 11. The filter 17 can filter the fluid at the oil tank outlet, improve the cleanliness of the fluid, prevent blockage when the fluid enters the throttling element 11 for throttling, and improve the accuracy of the oil temperature measurement results.

[0068] The present invention also provides an air conditioning system that uses the oil level determination method for the compressor 1 described above. By using the oil level determination method described above, it is possible to detect when the compressor 1 is short of oil in a timely manner, thus ensuring the stable and reliable operation of the compressor 1.

[0069] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for determining the oil level of a compressor, characterized in that, The compressor has an oil sump, and a throttling element and a liquid temperature sensor are sequentially installed at the outlet of the oil sump. The liquid temperature sensor is used to measure the fluid temperature Tk after the fluid flowing out of the oil sump has been throttled by the throttling element. The oil level determination method includes: Parameter acquisition steps: Obtain the compressor's high pressure Ph, low pressure Ps, exhaust temperature Tp, and fluid temperature Tk; Data processing steps: Determine the compression ratio Px of the compressor based on the high pressure Ph and the low pressure Ps; calculate the predicted oil temperature Tkcal of the compressor based on the compression ratio Px, the exhaust temperature Tp, and the low pressure Ps. Calculate the difference ΔT between the predicted oil temperature Tkcal and the fluid temperature Tk, and compare the difference ΔT with the preset dynamic parameters; Judgment steps: Determine whether the oil level of the compressor is qualified based on the comparison result between the difference △T and the dynamic parameter.

2. The method for determining the oil level of a compressor according to claim 1, characterized in that, The predicted oil temperature Tkcal is calculated as follows: Tkcal = A•Ps + B•Tp + C•Px, where A, B, and C are preset constants, and Px = (Ph + 0.1) / (Ps + 0.1).

3. The method for determining the oil level of a compressor according to claim 2, characterized in that, In the data processing step, the dynamic parameter = D + α + β + γ; where, D, α, β, and γ are all constants; α is related to exhaust superheat; β is related to outdoor ambient temperature; and γ is related to the compression ratio Px.

4. The method for determining the oil level of a compressor according to claim 3, characterized in that, -13≤α≤0;-7≤β≤2;-6≤γ≤-2; 5. The method for determining the oil level of a compressor according to claim 3, characterized in that, In the judgment step, determining the compressor oil level based on the comparison result of the difference ΔT and the dynamic parameter includes: If the difference ΔT < the first dynamic parameter, then the oil level of the compressor is normal; If the difference ΔT ≥ the first dynamic parameter and the difference ΔT ≥ the second dynamic parameter, then the compressor is short of oil. If the difference ΔT ≥ the first dynamic parameter and the difference ΔT < the second dynamic parameter, then the compressor oil level is normal; the D value in the first dynamic parameter is different from the D value in the second dynamic parameter, and the D value in the first dynamic parameter is less than the D value in the second dynamic parameter.

6. The method for determining the oil level of a compressor according to any one of claims 1 to 5, characterized in that, The compressor includes: An exhaust pipe is connected to the exhaust port of the compressor. A high-pressure sensor is installed on the exhaust pipe to detect the high-pressure Ph of the refrigerant flowing out of the exhaust port. A return gas line is connected to the return gas port of the compressor. A low-pressure sensor is installed on the return gas line to detect the low-pressure Ps of the refrigerant flowing out of the return gas port. A temperature measuring pipeline is connected between the oil outlet of the oil tank and the return gas pipeline. The throttling element and the liquid temperature sensor are located in the temperature measuring pipeline, and the liquid temperature sensor is spaced apart from the return gas pipeline.

7. The method for determining the oil level of a compressor according to claim 6, characterized in that, The throttling element is a capillary tube, the length of which is 1-1.5m and the diameter of which is 6-10mm.

8. The method for determining the oil level of a compressor according to claim 6, characterized in that, It also includes a fixing block disposed between the liquid temperature sensor and the return gas pipeline. The fixing block is used to fix the temperature measuring pipeline between the liquid temperature sensor and the return gas pipeline. The fixing block is a heat-insulating fixing block.

9. The method for determining the oil level of a compressor according to claim 6, characterized in that, It also includes a filter, located between the oil outlet and the throttling element.

10. An air conditioning system, characterized in that, The method for determining the oil level of the compressor according to any one of claims 1 to 9.

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