CN113790158A

CN113790158A - Oil path circulation system, compressor, oil path control method, and storage medium

Info

Publication number: CN113790158A
Application number: CN202111109092.3A
Authority: CN
Inventors: 张治平; 武晓昆; 刘志华; 毕雨时; 曹聪
Original assignee: Gree Electric Appliances Inc of Zhuhai
Current assignee: Gree Electric Appliances Inc of Zhuhai
Priority date: 2021-09-22
Filing date: 2021-09-22
Publication date: 2021-12-14

Abstract

The invention provides an oil circuit circulating system, a compressor, an oil circuit control method and a storage medium, and relates to the technical field of compressors. The oil circuit circulating system comprises a primary exhaust side bearing oil return branch and a secondary exhaust side bearing oil return branch; the first-stage exhaust side bearing oil return branch is connected with the second-stage exhaust side bearing oil return branch; the first oil return branch is connected with the first-stage exhaust side bearing oil return branch at one end and connected with the first-stage screw rotor cavity at the other end; the oil way circulation system also comprises an adjusting component which can adjust the oil return direction of the oil way circulation system; the compressor is a two-stage screw compressor and comprises an oil circuit circulating system. The oil return path is selected independently according to different environmental working conditions, redundant energy loss caused by excessive oil return of the first-stage bearing is avoided, accurate control of the internal oil quantity of the compressor is realized, and the two-stage screw compressor has the advantage of high operation efficiency.

Description

Oil path circulation system, compressor, oil path control method, and storage medium

Technical Field

The invention relates to the technical field of compressors, in particular to an oil path circulating system, a compressor, an oil path control method and a storage medium.

Background

The two-stage screw compressor has the characteristics of two pairs of screw rotors, namely a low-pressure stage rotor and a high-pressure stage rotor, the two-stage rotors are connected in series to complete steam compression, and the compressor has the advantage of high efficiency due to segmented compression and low single-stage pressure ratio and the compression process is closer to isothermal compression, and is widely applied to the field of high-pressure specific heat pumps. Compared with a single-stage compressor, after the two-stage compressor is compressed in a segmented mode, the bearing arrangement number of the two-stage compression section is increased by 1 time, and the oil circuit number is correspondingly increased by 1 time, but when the two-stage compressor operates in a low-pressure ratio environment, because the single-stage pressure ratio of a low-pressure stage is low and the differential pressure is small, the required lubricating oil amount in the compressor is correspondingly reduced, the throttling hole plugs arranged on two sides of the low-pressure stage bearing cannot adaptively adjust the aperture size, so that the oil supply of the first-stage bearing is excessive, the friction power consumption of corresponding lubricating oil is increased, an oil-gas mixture of first-stage exhaust gas directly enters a suction cavity of a second-stage rotor (shown in figure 1), the oil content of the first-stage exhaust gas directly influences the second-stage suction amount, and the performance of the compressor is further reduced.

Disclosure of Invention

The invention aims to provide an oil circuit circulating system, a compressor, an oil circuit control method and a storage medium, and aims to solve the technical problems that when a two-stage screw compressor is in a low-pressure ratio operation state, oil is supplied to a low-pressure side more, efficiency loss is caused, and the performance of the compressor is reduced in the prior art.

In order to achieve the purpose, the invention provides the following technical scheme:

the invention provides an oil circuit circulating system which comprises a primary exhaust side bearing oil return branch and a secondary exhaust side bearing oil return branch; and the primary exhaust side bearing oil return branch is connected with the secondary exhaust side bearing oil return branch.

As a further improvement of the invention, the device also comprises a first oil return branch, wherein one end of the first oil return branch is connected with the first-stage exhaust side bearing oil return branch, and the other end of the first oil return branch is connected with the first-stage screw rotor cavity.

As a further improvement of the invention, the oil-way circulation system further comprises an adjusting assembly capable of adjusting the oil return direction of the oil-way circulation system.

As a further improvement of the invention, the adjusting component is an electromagnetic valve and is respectively arranged on the first-stage exhaust side bearing oil return branch and the first oil return branch; or the adjusting component is a reversible three-way valve and is arranged at the joint of the first-stage exhaust side bearing oil return branch and the first oil return branch.

As a further improvement of the invention, the device also comprises a controller, an evaporation side pressure sensor arranged at a suction port of the compressor and a condensation side pressure sensor arranged at an exhaust port of the compressor, wherein the controller is electrically connected with the regulating component, the evaporation side pressure sensor and the condensation side pressure sensor.

As a further improvement of the invention, the system also comprises an oil supply branch and an oil-gas treatment assembly connected with the oil supply branch and the exhaust port of the compressor.

As a further improvement of the invention, the oil-gas treatment component comprises an oil-gas separation barrel and an oil storage tank which are sequentially connected through pipelines.

The compressor is a two-stage screw compressor and comprises the oil circuit circulating system.

As a further improvement of the invention, the compressor also comprises a first-stage screw rotor, a second-stage screw rotor and a coupler, wherein the first-stage screw rotor and the second-stage screw rotor are connected through the coupler.

As a further improvement of the invention, one end of the coupler is provided with a comb seal.

The invention provides an oil way control method, which is a method for controlling the oil return direction of a two-stage screw compressor by using an oil way circulating system, and comprises the following steps:

step 100, calculating a pressure ratio, namely calculating the running pressure ratio P2/P1 of the compressor by the controller according to an input signal, wherein P2 is the condensing pressure; p1 is the evaporation pressure;

step 200, working condition judgment: judging whether the compressor operates under a working condition of a small pressure ratio or a working condition of a large pressure ratio according to the operating pressure ratio;

step 300, oil way adjustment: when the compressor operates under the working condition of small pressure ratio, the electromagnetic valve positioned on the first oil return branch in the adjusting assembly is closed, and the electromagnetic valve positioned on the oil return branch of the first-stage exhaust side bearing is opened; or a first outlet of the regulating assembly, which is connected with the first oil return branch by the three-way valve, is closed; when the compressor operates under a working condition of a high pressure ratio, the electromagnetic valve positioned on the first oil return branch in the adjusting assembly is opened, and the electromagnetic valve positioned on the oil return branch of the first-stage exhaust side bearing is closed; or a first outlet of the adjusting assembly, which is connected with the first oil return branch by the three-way valve, is opened.

As a further improvement of the invention, when the operation pressure ratio P2/P1 is less than 3.5, the compressor is judged to be operated under the working condition of small pressure ratio; when the operation pressure ratio P2/P1 is larger than or equal to 3.5, the compressor is judged to be operated under the working condition of large pressure ratio.

The storage medium is a computer-readable storage medium, a computer program is stored in the storage medium, and when the computer program runs, the function of the oil way control method can be realized.

Compared with the prior art, the invention has the following beneficial effects:

according to the oil circuit circulating system provided by the invention, the first-stage exhaust side bearing oil supply branch is connected to the second-stage exhaust side bearing oil return branch, so that when the compressor is in a low-pressure ratio operation state, first-stage exhaust side oil return does not flow back into a first-stage rotor cavity, but enters a second-stage rotor cavity, oil supply at a low-pressure side is reduced, the oil content of first-stage exhaust is reduced, and the oil content of first-stage exhaust is reduced, so that the second-stage suction volume is not occupied, and the efficiency of the compressor is further improved;

according to the oil circuit circulating system provided by the invention, the first oil return branch and the adjusting assembly are arranged, so that the oil return flow direction of the first-stage exhaust side bearing can be adjusted in time according to the operation condition of the compressor, when the compressor is in a low-pressure ratio operation state, the oil flows into the first-stage rotor cavity, and when the compressor is in a high-pressure ratio operation state, the oil flows into the second-stage rotor cavity, and the accurate control of the oil quantity of the oil circuit in the compressor is realized.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a prior art internal oil circuit circulation system for a two-stage screw compressor;

FIG. 2 is a schematic structural view of a first embodiment of an oil circulation system according to the present invention;

fig. 3 is a schematic structural view of an oil circulation system according to a second embodiment of the present invention.

In the figure 1, a first-stage exhaust side bearing oil return branch; 2. a secondary exhaust side bearing oil return branch; 3. a first oil return branch; 5. a first solenoid valve; 6. a second solenoid valve; 7. a controller; 8. an oil-gas separation barrel; 9. an oil storage tank; 10. a first-stage air suction side bearing oil supply branch; 11. a first-stage exhaust side bearing oil supply branch; 12. an oil supply branch of the secondary air suction side bearing; 13. and a secondary exhaust side bearing oil supply branch.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the examples given herein without any inventive step, are within the scope of the present invention.

As shown in fig. 2, the present invention provides an oil circuit circulation system, which includes 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 with the second-stage exhaust side bearing oil return branch 2, and the tail end of the second-stage exhaust side bearing oil return branch 2 is connected with the second-stage rotor cavity;

one end of a first-stage exhaust side bearing oil return branch 1 is connected to the exhaust side of a first-stage screw rotor cavity, and the other end of the first-stage exhaust side bearing oil return branch is connected to a second-stage exhaust side bearing oil return branch 2, so that an oil-gas mixture compressed by a first-stage screw rotor enters the air suction side of a second-stage screw rotor cavity; one end of a 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 of the second-stage exhaust side bearing oil return branch is connected to the air suction side of the second-stage screw rotor cavity, so that an oil-gas mixture compressed by the second-stage screw rotor enters the air suction side of the second-stage screw rotor cavity.

The oil return branch 1 of the first-stage exhaust side bearing is connected to the oil return branch 2 of the second-stage exhaust side bearing connected with the second-stage rotor cavity, so that oil return in the first-stage exhaust side bearing oil return branch 1 enters the second-stage rotor cavity, the problem of much oil supply in the first-stage rotor cavity is avoided when the compressor is in a low-pressure ratio operation state, efficiency loss is avoided, the efficiency of the compressor is improved, the operation performance of the compressor is improved, and the structure is simple.

Of course, the above is a technical scheme for the condition that the operation range of the compressor is narrow, that is, the working condition is comfortable and the change is not obvious, and the long-term operation working condition is in the low pressure ratio operation state.

When the compressor is in a wide-range working condition, namely a hot-summer and cold-winter area, the unit takes into account two working conditions of refrigeration and heating, the range of the working conditions is wide, two running states of a high-pressure ratio and a low-pressure ratio exist, and the oil return scheme has certain defects.

As shown in fig. 3, in a further alternative embodiment of the present invention, a first oil return branch 3 is further included, and one end of the first oil return branch 3 is connected to the first-stage exhaust side bearing oil return branch 1, and the other end is connected to the first-stage screw rotor cavity. The first oil return branch 3 is arranged, so that the return oil in the first-stage exhaust side bearing oil return branch 1 can also return to the first-stage rotor cavity as required.

Furthermore, the oil-way circulation system also comprises an adjusting component which can adjust the oil return direction of the oil-way circulation system. And the oil return in the oil return branch 1 of the primary exhaust side bearing is returned to the primary rotor cavity or the secondary rotor cavity through the adjusting component.

According to the oil circuit circulating system provided by the invention, the adjusting assembly is arranged, so that the flow direction of oil returned by the bearing at the first-stage exhaust side can be adjusted in time according to the operation condition of the compressor, when the compressor is in a low-pressure ratio operation state, the oil flows into the first-stage rotor cavity, and when the compressor is in a high-pressure ratio operation state, the oil flows into the second-stage rotor cavity, so that the accurate control of the oil quantity of the oil circuit in the compressor is realized.

As a first optional embodiment of the present invention, the adjusting components are electromagnetic valves, and are respectively disposed on the first-stage exhaust side bearing oil return branch 1 and the first oil return branch 3, when this scheme is adopted, the electromagnetic valves are respectively a first electromagnetic valve 5 and a second electromagnetic valve 6, the first electromagnetic valve 5 is disposed on the first-stage exhaust side bearing oil return branch 1, and the electromagnetic valve 6 is disposed on the first oil return branch 3.

The electromagnetic valves are respectively arranged on the two oil return branches, so that the opening or closing of the electromagnetic valves on the two oil return branches can be controlled according to the running state of the compressor, the oil return in the first-stage exhaust side bearing oil return branch 1 enters the first-stage rotor cavity or the second-stage rotor cavity, and the accurate control of an internal oil way is realized.

As a second optional embodiment of the present invention, the adjusting component is a reversible three-way valve, and is disposed at a junction of the first oil return branch 3 and the first-stage exhaust-side bearing oil return branch 1; through the circulation direction of control three-way valve, that is to say through the intercommunication that realizes different passageways of opening or closing of two exports in the control three-way valve, can realize that the oil return in one-level exhaust side bearing oil return branch 1 enters into one-level rotor chamber or second grade rotor chamber, realizes the accurate control to inside oil circuit.

Further, the electromagnetic valve further comprises a controller 7, wherein the controller 7 is electrically connected with the adjusting assembly, for example, the controller 7 can be electrically connected with both the first electromagnetic valve 5 and the second electromagnetic valve 6 to transmit switch control signals to the two electromagnetic valves; alternatively, the controller 7 may be electrically connected to the 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 communicating state; the air conditioner also comprises an evaporation side pressure sensor arranged at an air suction port of the compressor and a condensation side pressure sensor arranged at an air exhaust port of the compressor, and the controller 7 is electrically connected with the evaporation side pressure sensor and the condensation side pressure sensor.

The ratio of the evaporation pressure to the condensation pressure measured by the evaporation side pressure sensor and the condensation side pressure sensor is used for judging the running state of the compressor, and the opening state of the regulating piece is controlled according to the running state, so that different flow direction control of oil return is realized.

The oil gas treatment device also comprises four oil supply branches and an oil gas treatment assembly connected with the oil supply branches and the exhaust port of the compressor.

Wherein, the oil gas processing assembly comprises an oil-gas separation barrel 8 and an oil storage tank 9 which are sequentially connected through pipelines.

The four oil supply branches are respectively a primary air suction side bearing oil supply branch 10, a primary air exhaust side bearing oil supply branch 11, a secondary air suction side bearing oil supply branch 12 and a secondary air exhaust side bearing oil supply branch 13.

As shown in fig. 3, the connection line between the controller 7 and the first and second solenoid valves 5 and 6 represents an electrical connection line, not an oil line.

The compressor further comprises a first-stage screw rotor, a second-stage screw rotor and a coupler, the first-stage screw rotor and the second-stage screw rotor are connected through the coupler, the motor drives the first-stage screw rotor to rotate, and the second-stage screw rotor and the first-stage screw rotor are driven by the motor to rotate under the effect of the coupler. Specifically, the first-stage screw rotor and the second-stage screw rotor respectively comprise a male rotor and a female rotor, and the male rotor and/or the female rotor of the two-stage rotors are connected through a coupler.

The novel gear coupling is characterized by further comprising a comb seal arranged at one end of the coupler, and the comb seal is located on one side of a bearing cavity of the screw rotor.

The compressor provided by the invention can judge the operation condition of the compressor according to the external environment pressure, and the change of the oil return position of the oil supply of the first-stage exhaust side bearing is realized by controlling the on-off of the electromagnetic valve through the controller, specifically:

1. when the compressor operates in a low pressure ratio environment (the ratio of the exhaust pressure/the suction pressure of the compressor is less than 3.5 in the embodiment), the lubricating oil of the bearing on the exhaust side of the first stage, which occupies most of the oil supply, does not directly enter the cavity of the rotor of the first stage, but returns to the closed tooth space of the suction side of the second stage after completing the lubricating function, so that the oil content of the exhaust gas of the first stage can be reduced, and the volume of the suction side of the second stage is not occupied, thereby further improving the efficiency of the compressor.

2. When the compressor operates in a high pressure ratio environment (the ratio of the exhaust pressure/the suction pressure of the compressor is not less than 3.5 in the embodiment), 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.

Furthermore, the invention provides a two-stage screw compressor, which comprises a one-stage screw rotor, bearings at two sides of a low-pressure stage air suction side and an exhaust side, a two-stage screw rotor, bearings at two sides of a high-pressure stage air suction side and an exhaust side, and the oil circuit circulation system. Wherein, the first-stage screw rotor and the second-stage screw rotor are connected by a coupling, the bearing cavities on the two exhaust sides are provided with sealing devices, and the outside of the compressor is provided with an oil-gas separation device and an oil storage device.

The oil-gas mixture discharged by the compressor is separated by the external oil-gas separation device, then the lubricating oil enters the oil storage tank 9, and the lubricating oil in the oil storage tank 9 realizes the oil supply inside the compressor under the action of pressure difference. In the compressor, the main oil supply circuit is divided into four branches, namely a first-stage air suction side bearing oil supply branch 10, a first-stage air exhaust side bearing oil supply branch 11, a second-stage air suction side bearing oil supply branch 12 and a second-stage air exhaust side bearing oil supply branch 13, oil is supplied to bearings arranged inside through the four branches, and each branch is provided with a throttling device respectively to control the oil flow. Then, an electromagnetic valve is respectively arranged on the first oil return branch 3 and the first-stage exhaust side bearing oil return branch 1, a controller 7 is arranged to control the on-off of the electromagnetic valve, the input signals of the controller are evaporation pressure P1 and condensation pressure P2, and the controller carries out pressure ratio calculation (condensation pressure value/evaporation pressure value). The evaporation pressure P1 comes from the evaporation side pressure sensor at the suction port of the compressor, and the condensation pressure P2 comes from the condensation side pressure sensor at the exhaust port of the compressor.

When the pressure ratio P2/P1 is less than 3.5, the compressor is judged to operate under the working condition of small pressure ratio, at the moment, the second electromagnetic valve 6 on the second oil return branch 4 is closed, the first electromagnetic valve 5 on the first oil return branch 3 is opened, lubricating oil directly enters a compressor suction cavity after lubricating a suction side bearing at the first-stage suction side, and the lubricating oil and return oil of a second-stage exhaust side bearing jointly enter a first tooth groove behind a second-stage suction closed tooth groove after lubricating a first-stage exhaust side bearing, so that the phenomenon that the oil carried by first-stage exhaust gas excessively affects the volume of second-stage suction gas is avoided, the oil circulation amount of an internal oil circuit is reduced, the efficiency of the compressor is further improved, and the lubricating oil enters an external oil-gas separation device again after the compression and exhaust processes of a second-stage rotor to complete the circulation of the lubricating oil of the system. In order to ensure the oil return sealing of the first-stage exhaust side bearing, comb tooth sealing is required to be arranged between the tail end of the first-stage male rotor and the coupler. The comb tooth seal can be triangular, trapezoidal and the like, and can be replaced by other sealing means, such as a sealing ring and the like;

when the pressure ratio P2/P1 is larger than or equal to 3.5, the compressor is judged to operate under the working condition of large pressure ratio, at the moment, the second electromagnetic valve 6 on the second oil return branch 4 is opened, the first electromagnetic valve 5 on the first oil return branch 3 is closed, oil returned by the first-stage bearing returns to the first-stage rotor cavity, and the oil is used for sealing the tooth grooves, so that the increase of leakage caused by large pressure difference among the tooth grooves is avoided.

The invention provides an oil way control method, which is a method for controlling the oil return direction of a two-stage screw compressor by using the oil way circulating system, and comprises the following steps:

Further, in the embodiment, when the operation pressure ratio P2/P1 is less than 3.5, the compressor is judged to be operated under the low pressure ratio working condition; when the operation pressure ratio P2/P1 is larger than or equal to 3.5, the compressor is judged to be operated under the working condition of large pressure ratio.

It should be noted that "inward" is a direction toward the center of the accommodating space, and "outward" is a direction away from the center of the accommodating space.

In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in fig. 1 to facilitate the description of the invention and to simplify the description, but are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are not to be considered as limiting the invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims

1. An oil circuit circulating system is characterized by comprising a primary exhaust side bearing oil return branch and a secondary exhaust side bearing oil return branch; and the primary exhaust side bearing oil return branch is connected with the secondary exhaust side bearing oil return branch.

2. The oil circuit circulation system according to claim 1, further comprising a first oil return branch, one end of the first oil return branch being connected to the first-stage exhaust side bearing oil return branch, and the other end thereof being connected to the first-stage screw rotor chamber.

3. The oil circulation system according to claim 2, further comprising an adjustment assembly capable of adjusting an oil return direction of the oil circulation system.

4. The oil circuit circulation system according to claim 3, wherein the adjusting assembly is a solenoid valve, and is disposed on the primary exhaust side bearing oil return branch and the first oil return branch, respectively; or the adjusting component is a reversible three-way valve and is arranged at the joint of the first-stage exhaust side bearing oil return branch and the first oil return branch.

5. The oil circuit circulation system of claim 3, further comprising a controller, an evaporator side pressure sensor and a condenser side pressure sensor, the controller being electrically connected to the adjustment assembly, the evaporator side pressure sensor and the condenser side pressure sensor.

6. The oil circulation system of claim 1, further comprising an oil supply branch and an oil and gas treatment assembly connected to the oil supply branch and a compressor discharge port.

7. The oil circuit circulation system of claim 6, wherein the oil and gas treatment assembly comprises an oil and gas separation barrel and an oil storage tank which are sequentially connected by a pipeline.

8. A compressor, characterized in that it is a two-stage screw compressor comprising an oil circulation system according to any one of claims 1 to 7.

9. The compressor of claim 8, further comprising a primary screw rotor, a secondary screw rotor, and a coupling, wherein the primary screw rotor and the secondary screw rotor are connected by the coupling.

10. The compressor of claim 9, wherein the coupling is provided with a comb seal at one end.

11. An oil path control method, characterized in that the method for controlling the oil return direction of the double-stage screw compressor by using the oil path circulation system as claimed in any one of claims 4 to 7 comprises the following steps:

12. The oil passageway control method according to claim 11, wherein 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 operation pressure ratio P2/P1 is larger than or equal to 3.5, the compressor is judged to be operated under the working condition of large pressure ratio.

13. A storage medium, which is a computer-readable storage medium, and in which a computer program is stored, and when the computer program runs, the function of the oil path control method according to any one of claims 11 to 12 is realized.