Oil circulation system, compressor, oil circuit control method, storage medium

Abstract

The present invention provides an oil circuit circulation system, a compressor, an oil circuit control method, and a storage medium, and relates to the technical field of compressors. The oil circuit circulation system includes a primary exhaust side bearing oil return branch and a secondary exhaust side bearing oil return branch; the primary exhaust side bearing oil return branch is connected to the secondary exhaust side bearing oil return branch; it also includes a first oil return branch, one end of the first oil return branch is connected to the primary exhaust side bearing oil return branch, and the other end is connected to the primary screw rotor cavity; it also includes an adjustment component that can adjust the oil return direction of the oil circuit circulation system; the compressor is a two-stage screw compressor, including an oil circuit circulation system. The present invention is used for the bearing oil return structure of the two-stage screw compressor, and the oil return path is selected autonomously according to different environmental conditions, so as to avoid excessive energy loss caused by excessive oil return of the primary bearing, realize precise control of the oil volume inside the compressor, and have the advantage of high compressor operation efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of compressors, and in particular to an oil circuit circulation system, a compressor, an oil circuit control method, and a storage medium. Background Art

[0002] The two-stage screw compressor features two pairs of screw rotors, namely the low-pressure stage and the high-pressure stage rotors. The two-stage rotors are connected in series to complete the steam compression. Due to the staged compression, the single-stage pressure ratio is relatively low, and the compression process is closer to isothermal compression. Therefore, the compressor has the advantage of high efficiency and is widely used in the field of high-pressure ratio heat pumps. Compared with the single-stage compressor, after staged compression, the number of bearing arrangements in the two-stage compression section has increased by 1 times, and the number of oil circuits has increased by 1 times accordingly. However, when the two-stage compressor operates in a small pressure ratio environment, due to the low single-stage pressure ratio and small pressure difference of the low-pressure stage, the amount of lubricating oil required inside the compressor is reduced accordingly. The throttling hole plugs arranged on the bearings on both sides of the low-pressure stage cannot adaptively adjust the aperture size, resulting in more oil supply to the first-stage bearing, and the corresponding increase in the friction power consumption of the lubricating oil. In addition, the oil-gas mixture of the first-stage exhaust directly enters the suction chamber of the second-stage rotor (such as Figure 1 As shown in the figure, the oil content of the first-stage exhaust will directly affect the second-stage suction volume, further reducing the performance of the compressor. Summary of the invention

[0003] The object of the present invention is to provide an oil circuit circulation system, a compressor, an oil circuit control method, and a storage medium to solve the technical problem in the prior art that when a two-stage screw compressor is in low-pressure ratio operation, more oil is supplied to the low-pressure side, resulting in efficiency loss and reduced compressor performance.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] The present invention provides an oil circulation system, comprising a primary exhaust side bearing oil return branch and a secondary exhaust side bearing oil return branch; the primary exhaust side bearing oil return branch is connected to the secondary exhaust side bearing oil return branch.

[0006] As a further improvement of the present invention, it also includes a first oil return branch, one end of which is connected to the first-stage exhaust side bearing oil return branch, and the other end is connected to the first-stage screw rotor cavity.

[0007] As a further improvement of the present invention, it also includes an adjustment component capable of adjusting the oil return direction of the oil circulation system.

[0008] As a further improvement of the present invention, the regulating component is a solenoid valve, which is respectively arranged on the first-stage exhaust side bearing oil return branch and the first oil return branch; or, the regulating component is a reversible three-way valve, which is arranged at the junction of the first-stage exhaust side bearing oil return branch and the first oil return branch.

[0009] As a further improvement of the present invention, it also includes a controller, an evaporation side pressure sensor arranged at the compressor suction port, and a condensation side pressure sensor arranged at the compressor exhaust port, and the controller is electrically connected to the adjustment component, the evaporation side pressure sensor, and the condensation side pressure sensor.

[0010] As a further improvement of the present invention, it also includes an oil supply branch and an oil and gas processing component connected to the oil supply branch and the compressor exhaust port.

[0011] As a further improvement of the present invention, the oil and gas processing assembly includes an oil and gas separation barrel and an oil storage tank which are connected in sequence by pipelines.

[0012] The present invention provides a compressor, which is a two-stage screw compressor and includes the oil circulation system.

[0013] As a further improvement of the present invention, the compressor further includes a primary screw rotor, a secondary screw rotor and a coupling, and the primary screw rotor and the secondary screw rotor are connected via the coupling.

[0014] As a further improvement of the present invention, a comb seal is provided at one end of the coupling.

[0015] The present invention provides an oil circuit control method, which uses the oil circuit circulation system to control the oil return direction of a two-stage screw compressor, comprising the following steps:

[0016] Step 100, pressure ratio calculation, the controller calculates the compressor operating pressure ratio P2 / P1 according to the input signal, where P2 is the condensing pressure; P1 is the evaporating pressure;

[0017] Step 200, operating condition determination: determining whether the compressor is operating under a small pressure ratio operating condition or a large pressure ratio operating condition according to the operating pressure ratio;

[0018] Step 300, oil circuit adjustment: when the compressor operates under a small pressure ratio condition, the solenoid valve located on the first oil return branch in the adjustment component is closed, and the solenoid valve located on the first-stage exhaust side bearing oil return branch is opened; or, the first outlet connected to the first oil return branch by the three-way valve in the adjustment component is closed; when the compressor operates under a large pressure ratio condition, the solenoid valve located on the first oil return branch in the adjustment component is opened, and the solenoid valve located on the first-stage exhaust side bearing oil return branch is closed; or, the first outlet connected to the first oil return branch by the three-way valve in the adjustment component is opened.

[0019] As a further improvement of the present invention, when the operating pressure ratio P2 / P1<3.5, it is determined that the compressor is operating under a small pressure ratio condition; when the operating pressure ratio P2 / P1≥3.5, it is determined that the compressor is operating under a large pressure ratio condition.

[0020] A storage medium provided by the present invention is a computer-readable storage medium, wherein a computer program is stored inside the storage medium, and when the computer program is executed, the function of the oil circuit control method can be realized.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The oil circulation system provided by the present invention connects the oil supply branch of the first-stage exhaust side bearing to the oil return branch of the second-stage exhaust side bearing, so that when the compressor is in a low-pressure ratio operating state, the return oil on the first-stage exhaust side does not flow back into the first-stage rotor cavity, but enters the second-stage rotor cavity, thereby reducing the oil supply on the low-pressure side and reducing the oil content of the first-stage exhaust. Since the oil content of the first-stage exhaust is reduced, the second-stage suction volume is not occupied, and the efficiency of the compressor is further improved.

[0023] The oil circulation system provided by the present invention, by setting a first oil return branch and an adjusting component, can timely adjust the flow direction of the return oil from the first-stage exhaust side bearing according to the operating conditions of the compressor. When the compressor is in a low-pressure ratio operating state, the return oil flows into the first-stage rotor cavity, and when the compressor is in a high-pressure ratio operating state, the return oil flows into the second-stage rotor cavity, thereby realizing precise control of the oil amount in the oil circuit inside the compressor. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 It is an internal oil circulation system of a two-stage screw compressor in the prior art;

[0026] Figure 2 It is a structural schematic diagram of a first embodiment of the oil circuit circulation system of the present invention;

[0027] Figure 3 It is a structural schematic diagram of the second embodiment of the oil circuit circulation system of the present invention.

[0028] In the figure, 1, the first-stage exhaust side bearing oil return branch; 2, the second-stage exhaust side bearing oil return branch; 3, the first oil return branch; 5, the first solenoid valve; 6, the second solenoid valve; 7, the controller; 8, the oil-gas separation barrel; 9, the oil storage tank; 10, the first-stage suction side bearing oil supply branch; 11, the first-stage exhaust side bearing oil supply branch; 12, the second-stage suction side bearing oil supply branch; 13, the second-stage exhaust side bearing oil supply branch. DETAILED DESCRIPTION

[0029] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0030] like Figure 2 As shown, the present invention provides an oil circulation system, including a first-stage exhaust side bearing oil return branch 1 and a second-stage exhaust side bearing oil return branch 2; the first-stage exhaust side bearing oil return branch 1 is connected to the second-stage exhaust side bearing oil return branch 2, and the end of the second-stage exhaust side bearing oil return branch 2 is connected to the second-stage rotor cavity;

[0031] It should be noted that one end of the first-stage exhaust side bearing oil return branch 1 is connected to the exhaust side of the first-stage screw rotor cavity, and the other end is connected to the second-stage exhaust side bearing oil return branch 2, so that the oil-gas mixture compressed by the first-stage screw rotor enters the suction side of the second-stage screw rotor cavity; one end of the second-stage exhaust side bearing oil return branch 2 is connected to the exhaust side of the second-stage screw rotor cavity, and the other end is connected to the suction side of the second-stage screw rotor cavity, so that the oil-gas mixture compressed by the second-stage screw rotor enters the suction side of the second-stage screw rotor cavity.

[0032] By connecting the first-stage exhaust side bearing oil return branch 1 to the second-stage exhaust side bearing oil return branch 2 connected to the second-stage rotor cavity, the return oil in the first-stage exhaust side bearing oil return branch 1 enters the second-stage rotor cavity, so that when the compressor is operating at a small pressure ratio, the problem of excessive oil supply in the first-stage rotor cavity will not be caused, and efficiency loss is avoided, thereby improving the efficiency of the compressor, improving the operating performance of the compressor, and having a simple structure.

[0033] Of course, the above is a technical solution for when the compressor has a narrow operating range, that is, the operating conditions are comfortable and the changes are not obvious, and the long-term operating conditions are in a low pressure ratio operating state.

[0034] When the compressor is in a wide range of operating conditions, that is, in hot summer and cold winter areas, the unit takes into account both cooling and heating conditions. The operating condition range is relatively wide, and there are two operating states: large pressure ratio and small pressure ratio. The above oil return scheme has certain shortcomings.

[0035] like Figure 3 As shown, in view of this situation, a further optional embodiment of the present invention further includes a first oil return branch 3, one end of the first oil return branch 3 is connected to the first exhaust side bearing oil return branch 1, and the other end is connected to the first screw rotor cavity. By providing the first oil return branch 3, the return oil in the first exhaust side bearing oil return branch 1 can also flow back to the first rotor cavity as needed.

[0036] Furthermore, it also includes an adjustment component capable of adjusting the oil return direction of the oil circulation system. The oil return in the first exhaust side bearing oil return branch 1 is returned to the first rotor cavity or the second rotor cavity through the adjustment component.

[0037] The oil circulation system provided by the present invention can adjust the flow direction of the return oil from the first-stage exhaust side bearing in time according to the operating conditions of the compressor by setting an adjustment component. When the compressor is in a low-pressure ratio operating state, the return oil flows into the first-stage rotor cavity. When the compressor is in a high-pressure ratio operating state, the return oil flows into the second-stage rotor cavity, thereby realizing precise control of the oil amount in the oil circuit inside the compressor.

[0038] As a first optional embodiment of the present invention, the regulating component is a solenoid valve, which is respectively arranged on the first-stage exhaust side bearing oil return branch 1 and the first oil return branch 3. When this scheme is adopted, the solenoid valves are respectively a first solenoid valve 5 and a second solenoid valve 6. The first solenoid valve 5 is arranged on the first-stage exhaust side bearing oil return branch 1, and the solenoid valve 6 is arranged on the first oil return branch 3.

[0039] By respectively arranging solenoid valves on the two oil return branches, the opening or closing of the solenoid valves on the two oil return branches can be controlled according to the operating status of the compressor, so that the return oil in the first-stage exhaust side bearing oil return branch 1 enters the first-stage rotor cavity or the second-stage rotor cavity, thereby realizing precise control of the internal oil circuit.

[0040] As a second optional embodiment of the present invention, the regulating component is a reversible three-way valve, which is arranged at the junction of the first oil return branch 3 and the first-stage exhaust side bearing oil return branch 1; by controlling the flow direction of the three-way valve, that is, by controlling the opening or closing of the two outlets in the three-way valve to achieve the connection of different passages, the return oil in the first-stage exhaust side bearing oil return branch 1 can enter the first-stage rotor cavity or the second-stage rotor cavity, thereby realizing precise control of the internal oil circuit.

[0041] Furthermore, it also includes a controller 7, which is electrically connected to the regulating component. For example, the controller 7 can be electrically connected to the first solenoid valve 5 and the second solenoid valve 6 to transmit a switch control signal to the two solenoid valves; or, the controller 7 can be electrically connected to the reversing three-way valve to transmit a reversing signal to the three-way valve so that one of the two flow paths in the three-way valve is in a connected state; it also includes an evaporation side pressure sensor arranged at the compressor suction port and a condensation side pressure sensor arranged at the compressor exhaust port, and the controller 7 is electrically connected to the evaporation side pressure sensor and the condensation side pressure sensor.

[0042] The ratio of the evaporation pressure and the condensation pressure measured by the evaporation side pressure sensor and the condensation side pressure sensor is used to determine the operating state of the compressor, and the opening state of the adjustment component is controlled according to the state to achieve different flow direction control of the return oil.

[0043] It also includes four oil supply branches and an oil and gas processing component connected to the oil supply branches and the compressor exhaust port.

[0044] The oil and gas processing assembly includes an oil and gas separation barrel 8 and an oil storage tank 9 which are connected in sequence by pipelines.

[0045] The four oil supply branches are respectively a first-stage suction side bearing oil supply branch 10, a first-stage exhaust side bearing oil supply branch 11, a second-stage suction side bearing oil supply branch 12, and a second-stage exhaust side bearing oil supply branch 13.

[0046] It should be noted that if Figure 3 As shown, the connection lines between the controller 7 and the first solenoid valve 5 and the second solenoid valve 6 represent electrical connection lines, not oil pipelines.

[0047] The present invention provides a compressor, which is a two-stage screw compressor and includes the above-mentioned oil circulation system.

[0048] The compressor further includes a primary screw rotor, a secondary screw rotor and a coupling, wherein the primary screw rotor and the secondary screw rotor are connected via the coupling, the primary screw rotor is driven by a motor to rotate, and the secondary screw rotor is driven by the motor to rotate together with the primary screw rotor under the action of the coupling. Specifically, the primary screw rotor and the secondary screw rotor each include a male rotor and a female rotor, and the male rotor and / or the female rotor of the two-stage rotor are connected via a coupling.

[0049] It also includes a comb teeth seal arranged at one end of the coupling, and the comb teeth seal is specifically located at one side of the bearing cavity of the screw rotor.

[0050] The compressor provided by the present invention can judge the operating condition of the compressor according to the external environmental pressure, and control the on-off of the solenoid valve through the controller to change the return oil position of the first-stage exhaust side bearing oil supply, specifically:

[0051] 1. When the compressor operates in a small pressure ratio environment (in this embodiment, the ratio of compressor exhaust pressure / intake pressure is specified to be less than 3.5), the lubricating oil of the first-stage exhaust side bearing, which occupies most of the oil supply, does not directly enter the first-stage rotor cavity after completing the lubrication function, but returns to the second-stage intake closed tooth groove. This can reduce the oil content of the first-stage exhaust and does not occupy the second-stage intake volume, thereby further improving the efficiency of the compressor.

[0052] 2. When the compressor operates in a high pressure ratio environment (in this embodiment, the ratio of the compressor exhaust pressure / intake pressure is specified to be ≥3.5), the lubricating oil of the first-stage exhaust side bearing directly returns to the first-stage rotor cavity to complete the gap sealing of the first-stage rotor section.

[0053] Furthermore, the present invention provides a two-stage screw compressor, comprising a first-stage screw rotor, bearings on both sides of the low-pressure stage suction and exhaust, a second-stage screw rotor, bearings on both sides of the high-pressure stage suction and exhaust, and the above-mentioned oil circulation system. The first-stage screw rotor and the second-stage screw rotor are connected by a coupling, the bearing cavities on the exhaust sides of the two stages are both provided with sealing devices, and an oil-gas separation device and an oil storage device are provided outside the compressor.

[0054] The oil-gas mixture discharged by the compressor is separated by an external oil-gas separation device, and the lubricating oil enters the oil storage tank 9. The lubricating oil in the oil storage tank 9 is supplied to the compressor by the pressure difference. Inside the compressor, the main oil supply circuit is divided into four branches, namely, the first-stage suction side bearing oil supply branch 10, the first-stage exhaust side bearing oil supply branch 11, the second-stage suction side bearing oil supply branch 12, and the second-stage exhaust side bearing oil supply branch 13. The four branches are used to supply oil to the bearings arranged inside. Each branch is provided with a throttling device to control the oil flow. Then, a solenoid valve is provided on the first oil return branch 3 and the first-stage exhaust side bearing oil return branch 1, respectively, and a controller 7 is provided to control the on and off of the solenoid valve. The input signal of the controller is the evaporation pressure P1 and the condensation pressure P2, and the controller calculates the pressure ratio (condensation pressure value / evaporation pressure value). The evaporation pressure P1 comes from the evaporation side pressure sensor at the compressor suction port, and the condensation pressure P2 comes from the condensation side pressure sensor at the compressor exhaust port.

[0055] When the pressure ratio P2 / P1<3.5, the compressor is determined to be operating under a low pressure ratio condition. At this time, the second solenoid valve 6 on the second oil return branch 4 is closed, and the first solenoid valve 5 on the first oil return branch 3 is opened. On the first-stage suction side, the lubricating oil directly enters the suction chamber of the compressor after lubricating the suction side bearing. After lubricating the first-stage exhaust side bearing, the lubricating oil enters the first tooth groove after the second-stage suction closed tooth groove together with the return oil of the second-stage exhaust side bearing. This can avoid excessive oil in the first-stage exhaust affecting the second-stage suction volume, reduce the oil circulation volume in the internal oil circuit, and further improve the efficiency of the compressor. After the compression and exhaust process of the second-stage rotor, it enters the external oil-gas separation device again to complete the system lubricating oil circulation. In order to ensure the oil return seal of the first-stage exhaust side bearing, a comb tooth seal needs to be set between the end of the first-stage male rotor and the coupling. The shape of the comb tooth seal can be a triangle, trapezoid, etc., and the comb tooth seal can also be replaced by other sealing means, such as a sealing ring;

[0056] When the pressure ratio P2 / P1≥3.5, the compressor is determined to be operating under a large pressure ratio condition. At this time, the second solenoid valve 6 on the second oil return branch 4 is opened, and the first solenoid valve 5 on the first oil return branch 3 is closed. The primary bearing return oil returns to the primary rotor cavity. This part of the oil is used for tooth groove sealing to avoid increased leakage caused by the large pressure difference between the tooth grooves.

[0057] The present invention provides an oil circuit control method, which uses the above-mentioned oil circuit circulation system to control the oil return direction of a two-stage screw compressor, comprising the following steps:

[0058] Step 100, pressure ratio calculation, the controller calculates the compressor operating pressure ratio P2 / P1 according to the input signal, where P2 is the condensing pressure; P1 is the evaporating pressure;

[0059] Step 200, operating condition determination: determining whether the compressor is operating under a small pressure ratio operating condition or a large pressure ratio operating condition according to the operating pressure ratio;

[0060] Step 300, oil circuit adjustment: when the compressor operates under a small pressure ratio condition, the solenoid valve located on the first oil return branch in the adjustment component is closed, and the solenoid valve located on the first-stage exhaust side bearing oil return branch is opened; or, the first outlet connected to the first oil return branch by the three-way valve in the adjustment component is closed; when the compressor operates under a large pressure ratio condition, the solenoid valve located on the first oil return branch in the adjustment component is opened, and the solenoid valve located on the first-stage exhaust side bearing oil return branch is closed; or, the first outlet connected to the first oil return branch by the three-way valve in the adjustment component is opened.

[0061] Furthermore, in this embodiment, when the operating pressure ratio P2 / P1<3.5, it is determined that the compressor is operating under a small pressure ratio condition; when the operating pressure ratio P2 / P1≥3.5, it is determined that the compressor is operating under a large pressure ratio condition.

[0062] A storage medium provided by the present invention is a computer-readable storage medium, in which a computer program is stored. When the computer program is running, the function of the oil circuit control method can be realized.

[0063] First of all, it should be explained here that “inward” refers to the direction toward the center of the accommodating space, and “outward” refers to the direction away from the center of the accommodating space.

[0064] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate directions or positional relationships based on the attached Figure 1 The orientation or positional relationship shown is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0065] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0066] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0067] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0068] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0069] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. An oil circuit circulation method, characterized in that: It includes an oil circulation system, including a first-stage exhaust side bearing oil return branch and a second-stage exhaust side bearing oil return branch; the first-stage exhaust side bearing oil return branch is connected to the second-stage exhaust side bearing oil return branch; It also includes a first oil return branch, one end of which is connected to the first-stage exhaust side bearing oil return branch, and the other end is connected to the first-stage screw rotor cavity; It also includes an adjustment component capable of adjusting the oil return direction of the oil circulation system; The regulating component is a solenoid valve, which is respectively arranged on the first-stage exhaust side bearing oil return branch and the first oil return branch; Alternatively, the regulating component is a reversible three-way valve, which is arranged at the junction of the first-stage exhaust side bearing oil return branch and the first oil return branch; The method for controlling the oil return direction of a two-stage screw compressor by the oil circulation system comprises the following steps: Step 100, pressure ratio calculation, the controller calculates the compressor operating pressure ratio P2 / P1 according to the input signal, where P2 is the condensing pressure; P1 is the evaporating pressure; Step 200, operating condition determination: determining whether the compressor is operating under a small pressure ratio operating condition or a large pressure ratio operating condition according to the operating pressure ratio; Step 300, oil circuit adjustment: when the compressor operates under a small pressure ratio condition, the solenoid valve located on the first oil return branch in the adjustment component is closed, and the solenoid valve located on the first-stage exhaust side bearing oil return branch is opened; or, the first outlet connected to the first oil return branch by the three-way valve in the adjustment component is closed; when the compressor operates under a large pressure ratio condition, the solenoid valve located on the first oil return branch in the adjustment component is opened, and the solenoid valve located on the first-stage exhaust side bearing oil return branch is closed; or, the first outlet connected to the first oil return branch by the three-way valve in the adjustment component is opened.

2. The oil circulation method according to claim 1, characterized in that: It also includes a controller, an evaporation side pressure sensor and a condensation side pressure sensor, and the controller is electrically connected to the adjustment component, the evaporation side pressure sensor and the condensation side pressure sensor.

3. The oil circulation method according to claim 1, characterized in that: It also includes an oil supply branch and an oil and gas processing component connected to the oil supply branch and the compressor exhaust port.

4. The oil circulation method according to claim 3, characterized in that: The oil and gas processing assembly comprises an oil and gas separation barrel and an oil storage tank which are connected in sequence by pipelines.

5. The oil circulation method according to claim 1, characterized in that: When the operating pressure ratio P2 / P1<3.5, it is determined that the compressor is operating under a small pressure ratio condition; when the operating pressure ratio P2 / P1≥3.5, it is determined that the compressor is operating under a large pressure ratio condition.

6. A compressor, characterized in that: The compressor is a two-stage screw compressor, comprising the oil circulation method as described in any one of claims 1-5.

7. The compressor according to claim 6, characterized in that The compressor further comprises a primary screw rotor, a secondary screw rotor and a coupling, and the primary screw rotor and the secondary screw rotor are connected via the coupling.

8. The compressor according to claim 7, characterized in that A comb seal is arranged at one end of the coupling.

9. A storage medium, characterized in that: It is a computer-readable storage medium, which stores a computer program. When the computer program is executed, it can realize the function of the oil circulation method as described in any one of claims 1 to 5.

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