Screw Turbine Unit Oil Return Device and Control Method

Abstract

This application relates to an oil return device and its control method for a screw compressor unit, belonging to the technical field of screw compressor units. The oil return device includes a compressor and an oil return pipeline at the compressor's suction end; the suction end of the compressor is connected to the input end of the oil return pipeline, and the output end of the oil return pipeline is connected to the first oil return port of the compressor. This application aims to solve the problem of oil accumulation at the suction end of the compressor under low load, leading to frequent start-stop cycles due to oil shortage.

Description

Technical Field

[0001] This application relates to the field of screw compressor technology, and in particular to a screw compressor oil return device and its control method. Background Technology

[0002] In the operation of water-cooled screw compressors, refrigerant oil plays a crucial role in cooling, lubrication, sealing, and energy regulation, ensuring the reliability, stability, and service life of the compressor. During the compressor system circulation, refrigerant oil enters through the compressor's oil return port and lubricates various compressor components as the bearings rotate. When the compressor load is high, the rotor speed is high, directly carrying the refrigerant oil into the system circulation. Conversely, when the compressor load is low, the rotor speed is low, and some refrigerant oil may fall directly to the bottom of the compressor's suction end cover, preventing circulation and causing a shutdown.

[0003] Currently, previous researchers have conducted extensive studies on compressor oil return structures. For example, by adding auxiliary oil return components to the main oil return pipeline, the lubricating oil in the air conditioning system under ultra-low temperature conditions can be returned to the compressor through the auxiliary oil return components, effectively solving the problem of insufficient compressor oil return caused by lubricating oil clogging the capillary tube under ultra-low temperature conditions. Another example is the external oil separator structure for low-temperature water-cooled screw compressors, which can promptly separate the compressor oil carried out from the compressor, preventing it from entering the system and failing to return to the compressor in time, thus causing oil shortage damage to the compressor.

[0004] However, none of the current solutions can solve the problem of oil accumulation at the suction end of the compressor under low load, which causes the compressor to start and stop frequently due to oil shortage. Summary of the Invention

[0005] This application provides an oil return device and control method for a screw compressor unit to solve the problem of oil accumulation at the suction end of the compressor under low load, which causes the compressor to start and stop frequently due to oil shortage.

[0006] In a first aspect, embodiments of this application provide a screw compressor oil return device, including a compressor and a compressor suction end oil return pipeline;

[0007] The suction end of the compressor is connected to the input end of the suction end oil return line of the compressor, and the output end of the suction end oil return line of the compressor is connected to the first oil return port of the compressor.

[0008] Optionally, the screw compressor unit oil return device further includes an oil separator; the compressor suction end oil return pipeline includes a first solenoid valve and a first ejector;

[0009] The compressor's suction end is connected to the first input end of the first ejector, the oil separator's output end is connected to the first end of the first solenoid valve, the first solenoid valve's second end is connected to the second input end of the first ejector, and the first ejector's output end is connected to the compressor's first oil return port.

[0010] Optionally, the compressor suction end oil return line further includes a second solenoid valve and an oil pump;

[0011] The compressor's suction end is connected to the first end of the second solenoid valve, the second end of the second solenoid valve is connected to the first end of the oil pump, and the second end of the oil pump is connected to the compressor's first oil return port.

[0012] Optionally, the screw compressor oil return device further includes a liquid level sensor;

[0013] The measuring end of the liquid level sensor is connected to the suction end of the compressor, the first control end of the liquid level sensor is connected to the controlled end of the first solenoid valve, and the second control end of the liquid level sensor is connected to the controlled end of the second solenoid valve.

[0014] Optionally, the screw compressor unit oil return device further includes a main oil return pipeline; the main oil return pipeline includes a third solenoid valve, a ball valve, a sight glass, and a first oil filter;

[0015] The output end of the oil separator is connected to the first end of the third solenoid valve, the second end of the third solenoid valve is connected to the first end of the ball valve, the second end of the ball valve is connected to the first end of the sight glass, the second end of the sight glass is connected to the input end of the first oil filter, and the output end of the first oil filter is connected to the first oil return port of the compressor.

[0016] Optionally, the screw compressor unit oil return device further includes an evaporator and an evaporator ejector oil return line; the evaporator ejector oil return line includes a second oil filter and a second ejector;

[0017] The output end of the evaporator is connected to the input end of the second oil filter, the output end of the second oil filter is connected to the first input end of the second ejector, the second end of the ball valve is connected to the second input end of the second ejector, and the output end of the second ejector is connected to the second oil return port of the compressor.

[0018] Optionally, the liquid level sensor is used to detect the refrigerant oil level at the suction end of the compressor, and when the refrigerant oil level is greater than or equal to a first preset liquid level value, it controls the first solenoid valve to open and the second solenoid valve to close.

[0019] Optionally, the liquid level sensor is further configured to continue detecting the refrigerant oil level at the suction end of the compressor after controlling the first solenoid valve to open and the second solenoid valve to close, and to control the first solenoid valve to close when the refrigerant oil level is less than or equal to a second preset liquid level value, wherein the second preset liquid level value is less than the first preset liquid level value.

[0020] Optionally, the liquid level sensor is further configured to, after controlling the first solenoid valve to open and the second solenoid valve to close, acquire the opening duration of the first solenoid valve, and when the opening duration is greater than or equal to a preset opening duration, control the first solenoid valve to close and control the second solenoid valve to open.

[0021] Optionally, the liquid level sensor is further configured to continue detecting the refrigerant oil level at the suction end of the compressor after controlling the first solenoid valve to close and the second solenoid valve to open, and to control the second solenoid valve to close when the refrigerant oil level is less than or equal to a second preset liquid level value, wherein the second preset liquid level value is less than the first preset liquid level value.

[0022] Secondly, embodiments of this application provide a control method for a screw compressor oil return device, applied to a level sensor in the screw compressor oil return device described in the first aspect. The control method for the screw compressor oil return device includes:

[0023] Detect the refrigerant oil level at the suction end of the compressor;

[0024] When the refrigeration oil level is greater than or equal to a first preset level value, the first solenoid valve is controlled to open and the second solenoid valve is controlled to close.

[0025] Optionally, after controlling the first solenoid valve to open and the second solenoid valve to close, the method further includes:

[0026] Continue monitoring the refrigerant oil level at the suction end of the compressor;

[0027] When the refrigeration oil level is less than or equal to a second preset level value, the first solenoid valve is controlled to close, wherein the second preset level value is less than the first preset level value.

[0028] Optionally, after controlling the first solenoid valve to open and the second solenoid valve to close, the method further includes:

[0029] Obtain the opening duration of the first solenoid valve;

[0030] When the opening duration is greater than or equal to the preset opening duration, the first solenoid valve is controlled to close and the second solenoid valve is controlled to open.

[0031] Optionally, after controlling the first solenoid valve to close and the second solenoid valve to open, the method further includes:

[0032] Continue monitoring the refrigerant oil level at the suction end of the compressor;

[0033] When the refrigeration oil level is less than or equal to a second preset level value, the second solenoid valve is controlled to close, wherein the second preset level value is less than the first preset level value.

[0034] Compared with the prior art, the above-mentioned technical solution provided in this application embodiment has the following advantages: The screw compressor oil return device provided in this application embodiment includes a compressor and a compressor suction end oil return pipeline. The suction end of the compressor is connected to the input end of the compressor suction end oil return pipeline, and the output end of the compressor suction end oil return pipeline is connected to the first oil return port of the compressor. The compressor suction end oil return pipeline is used to return the refrigerant oil accumulated at the suction end of the compressor to the first oil return port of the compressor. This can improve the oil return efficiency of the compressor, prevent refrigerant oil from accumulating at the suction end of the compressor, ensure the compressor operates normally under low load, and solve the problem of oil accumulation at the suction end of the compressor under low load, which causes the compressor to start and stop frequently due to oil shortage. Attached Figure Description

[0035] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0036] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the oil return device of the screw compressor unit in the embodiments of this application;

[0038] Figure 2 This is a schematic diagram of the oil return device of a screw compressor unit in a specific embodiment of this application;

[0039] Figure 3 This is a schematic diagram of the oil return device of a screw compressor unit in a specific embodiment of this application;

[0040] Figure 4 This is a schematic diagram of the oil return device of a screw compressor unit in a specific embodiment of this application;

[0041] Figure 5 This is a schematic diagram of the oil return device of a screw compressor unit in a specific embodiment of this application;

[0042] Figure 6 This is a schematic diagram of the oil return device of a screw compressor unit in a specific embodiment of this application;

[0043] Figure 7 This is a schematic diagram of the method for controlling the oil return device of the screw compressor unit in an embodiment of this application;

[0044] Figure 8 This is a schematic diagram of the method for controlling the oil return device of a screw compressor unit in a specific embodiment of this application;

[0045] The attached diagram is labeled as follows: 10-compressor, 20-compressor suction end oil return line, 21-first solenoid valve, 22-first ejector, 23-second solenoid valve, 24-oil pump, 30-oil separator, 40-liquid level sensor, 50-main oil return line, 51-third solenoid valve, 52-ball valve, 53-sight glass, 54-first oil filter, 60-evaporator, 70-evaporator ejector oil return line, 71-second oil filter, 72-second ejector. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0047] In this embodiment of the application, a screw compressor oil return device is provided, such as... Figure 1 As shown, the screw compressor unit oil return device includes a compressor 10 and a compressor suction end oil return pipeline 20;

[0048] The suction end of the compressor 10 is connected to the input end of the compressor suction end oil return line 20, and the output end of the compressor suction end oil return line 20 is connected to the first oil return port of the compressor 10.

[0049] The compressor suction end oil return line is used to return the refrigerant oil accumulated at the compressor suction end to the compressor's first oil return port. This improves the compressor's oil return efficiency, prevents refrigerant oil from accumulating at the compressor suction end, ensures the compressor operates normally under low load, and solves the problem of frequent compressor start-stop due to oil shortage caused by oil accumulation at the suction end under low load.

[0050] In one specific embodiment, such as Figure 2As shown, the screw compressor unit oil return device includes a compressor 10, a compressor suction end oil return pipeline 20, and an oil separator 30; the compressor suction end oil return pipeline 20 includes a first solenoid valve 21 and a first ejector 22.

[0051] The suction end of the compressor 10 is connected to the first input end of the first ejector 22, the output end of the oil separator 30 is connected to the first end of the first solenoid valve 21, the second end of the first solenoid valve 21 is connected to the second input end of the first ejector 22, and the output end of the first ejector 22 is connected to the first oil return port of the compressor 10.

[0052] Figure 2 In the diagram, the arrows indicate the flow direction of the refrigerant oil. The refrigerant oil flowing out from the bottom of the compressor's suction end, along with the main oil flowing from the oil separator through the first solenoid valve, converges together through the first ejector into the compressor's first return port.

[0053] It can return the refrigeration oil accumulated at the suction end of the compressor to the first oil return port of the compressor.

[0054] In one specific embodiment, such as Figure 3 As shown, the compressor suction end oil return line 20 includes a first solenoid valve 21, a first ejector 22, a second solenoid valve 23, and an oil pump 24;

[0055] The suction end of the compressor 10 is connected to the first end of the second solenoid valve 23, the second end of the second solenoid valve 23 is connected to the first end of the oil pump 24, and the second end of the oil pump 24 is connected to the first oil return port of the compressor 10.

[0056] Figure 3 In the image, the arrow indicates the direction of the refrigeration oil flow. Figure 3 In this process, there are two ways for the refrigeration oil to flow. The first way is that the refrigeration oil flowing out from the bottom of the compressor's suction end, together with the main oil flowing from the oil separator through the first solenoid valve, flows into the compressor's first oil return port through the first ejector. The second way is that the refrigeration oil flowing out from the bottom of the compressor's suction end flows through the second solenoid valve and is directly drawn into the compressor's first oil return port by the oil pump.

[0057] If the first method fails to return the oil or the oil return effect is poor, the second method can be used: the oil pump can be used to directly draw the refrigerant oil accumulated at the compressor's suction end to the compressor's first oil return port to prevent the refrigerant oil from accumulating at the compressor's suction end.

[0058] In one specific embodiment, such as Figure 4 As shown, the screw compressor unit oil return device includes a compressor 10, a compressor suction end oil return pipeline 20, an oil separator 30, and a liquid level sensor 40.

[0059] The measuring end of the liquid level sensor 40 is connected to the suction end of the compressor 10, the first control end of the liquid level sensor 40 is connected to the controlled end of the first solenoid valve 21, and the second control end of the liquid level sensor 40 is connected to the controlled end of the second solenoid valve 23.

[0060] Figure 4 In the image, the arrow indicates the direction of the refrigeration oil flow.

[0061] A liquid level sensor is installed at the suction end of the compressor. The liquid level sensor can detect the level of the refrigerant oil at the suction end of the compressor and control the opening or closing of the first solenoid valve and the second solenoid valve according to the level of the refrigerant oil at the suction end of the compressor. This enables automatic control so that the refrigerant oil accumulated at the suction end of the compressor flows into the first oil return port of the compressor through the first ejector or through the oil pump.

[0062] In one specific embodiment, such as Figure 5 As shown, the screw compressor unit oil return device includes a compressor 10, a compressor suction end oil return line 20, an oil separator 30, a liquid level sensor 40, and a main oil return line 50; the main oil return line 50 includes a third solenoid valve 51, a ball valve 52, a sight glass 53, and a first oil filter 54.

[0063] The output end of the oil separator 30 is connected to the first end of the third solenoid valve 51, the second end of the third solenoid valve 51 is connected to the first end of the ball valve 52, the second end of the ball valve 52 is connected to the first end of the sight glass 53, the second end of the sight glass 53 is connected to the input end of the first oil filter 54, and the output end of the first oil filter 54 is connected to the first oil return port of the compressor 10.

[0064] Figure 5 In the diagram, the arrows indicate the flow direction of the refrigerant oil. The refrigerant oil in the main return oil line flows as follows: after exiting the oil separator, the refrigerant oil passes through the third solenoid valve, ball valve, sight glass, and first oil filter, and directly enters the compressor's first return oil port. Most of the compressor's return oil comes from the main return oil line.

[0065] In one specific embodiment, such as Figure 6 As shown, the screw compressor unit oil return device includes a compressor 10, a compressor suction end oil return line 20, an oil separator 30, a liquid level sensor 40, a main oil return line 50, an evaporator 60, and an evaporator ejector oil return line 70; the evaporator ejector oil return line 70 includes a second oil filter 71 and a second ejector 72.

[0066] The output end of the evaporator 60 is connected to the input end of the second oil filter 71, the output end of the second oil filter 71 is connected to the first input end of the second ejector 72, the second end of the ball valve 52 is connected to the second input end of the second ejector 72, and the output end of the second ejector 72 is connected to the second oil return port of the compressor 10.

[0067] Figure 6 In the diagram, the arrows indicate the flow direction of the refrigerant oil. The flow direction of the refrigerant oil in the evaporator ejector return line is as follows: the refrigerant oil flowing out from the bottom of the evaporator passes through the second oil filter, and together with the main oil coming from the oil separator through the third solenoid valve and ball valve, it flows through the second ejector and into the second oil return port of the compressor.

[0068] In one specific embodiment, a liquid level sensor is used to detect the level of refrigerant oil at the suction end of the compressor, and when the level of refrigerant oil is greater than or equal to a first preset liquid level value, it controls the first solenoid valve to open and the second solenoid valve to close.

[0069] The first preset liquid level value can be an empirical value or a value obtained from multiple tests. This value is used to determine whether to open the first solenoid valve. If the refrigerant oil level is greater than or equal to the first preset liquid level value, it indicates that a large amount of refrigerant oil has accumulated at the compressor's suction end. This requires the accumulated refrigerant oil to flow back to the compressor's first oil return port to prevent further accumulation and ensure the compressor operates normally under low load. By controlling the first solenoid valve to open, the refrigerant oil flowing from the bottom of the compressor's suction end, along with the main oil flowing from the oil separator through the first solenoid valve, flows together through the first ejector into the compressor's first oil return port. By controlling the second solenoid valve to close, the refrigerant oil flowing from the bottom of the compressor's suction end is prevented from flowing through the second solenoid valve and being directly drawn to the compressor's first oil return port by the oil pump.

[0070] In one specific embodiment, the liquid level sensor is also used to control the first solenoid valve to close and the second solenoid valve to close when the refrigeration oil level is lower than a first preset liquid level value.

[0071] If the refrigerant oil level is lower than the first preset level, it indicates that there is not much refrigerant oil accumulated at the compressor's suction end. This does not affect the compressor's oil return, and there is no need to return the accumulated refrigerant oil at the compressor's suction end to the compressor's first oil return port. Therefore, there is no need to control the opening of the first solenoid valve or the second solenoid valve. At this time, the compressor returns oil through the main oil return line and the evaporator ejector oil return line. If the first solenoid valve is closed, the main oil return can proceed through only one return line. If the first solenoid valve is open, it becomes a two-way oil return, which will affect the oil return flow rate of the line with the third solenoid valve, thereby affecting the ejector oil return at the bottom of the evaporator.

[0072] In one specific embodiment, the liquid level sensor is further configured to continue detecting the refrigerant oil level at the suction end of the compressor after controlling the first solenoid valve to open and the second solenoid valve to close, and to control the first solenoid valve to close when the refrigerant oil level is less than or equal to a second preset liquid level value, wherein the second preset liquid level value is less than the first preset liquid level value.

[0073] The second preset liquid level value can be an empirical value or a value obtained from multiple tests. This value is used to determine whether to close the first solenoid valve. If the refrigerant oil level is less than or equal to the second preset liquid level value, it indicates that the refrigerant oil return effect at the compressor's suction end is good, and there is not much refrigerant oil accumulated at the compressor's suction end, so there is no need to open the first solenoid valve. The first solenoid valve does not need to be continuously open; it will only be closed when there is a significant amount of refrigerant oil accumulated at the compressor's suction end. Closing the first solenoid valve when the refrigerant oil level is less than or equal to the second preset liquid level value prevents it from being continuously open, which could affect the return oil flow rate in the main oil return line and the evaporator ejector oil return line.

[0074] In one specific embodiment, the liquid level sensor is further configured to, after controlling the first solenoid valve to open and the second solenoid valve to close, acquire the opening duration of the first solenoid valve, and when the opening duration is greater than or equal to a preset opening duration, control the first solenoid valve to close and control the second solenoid valve to open.

[0075] The preset opening time can be an empirical value or a value obtained from multiple tests. When the opening time is greater than or equal to the preset opening time, the first solenoid valve is closed and the second solenoid valve is opened. This prevents the first solenoid valve from being continuously open. Controlling the first solenoid valve to close and the second solenoid valve to open allows the refrigerant oil flowing from the bottom of the compressor's suction end to flow through the second solenoid valve and be directly drawn by the oil pump to the compressor's first oil return port. This results in better oil return of the refrigerant oil accumulated at the bottom of the compressor's suction end and does not affect the oil return flow rate of the main oil return line and the evaporator ejector oil return line.

[0076] In one specific embodiment, the liquid level sensor is further configured to continue detecting the refrigerant oil level at the suction end of the compressor after controlling the first solenoid valve to close and the second solenoid valve to open, and to control the second solenoid valve to close when the refrigerant oil level is less than or equal to a second preset liquid level value, wherein the second preset liquid level value is less than the first preset liquid level value.

[0077] When the refrigerant oil level is less than or equal to the second preset level, it indicates that the refrigerant oil return effect at the compressor's suction end is very good, and there is not much refrigerant oil accumulated at the compressor's suction end. Therefore, it is not necessary to keep the second solenoid valve open. At this time, the second solenoid valve can be controlled to close.

[0078] In summary, the screw compressor oil return device provided in this embodiment includes a compressor and a compressor suction end oil return pipeline. The suction end of the compressor is connected to the input end of the compressor suction end oil return pipeline, and the output end of the compressor suction end oil return pipeline is connected to the first oil return port of the compressor. The compressor suction end oil return pipeline is used to return the refrigerant oil accumulated at the suction end of the compressor to the first oil return port of the compressor. This can improve the oil return efficiency of the compressor, prevent refrigerant oil from accumulating at the suction end of the compressor, ensure the compressor operates normally under low load, and solve the problem of oil accumulation at the suction end of the compressor under low load, which causes the compressor to start and stop frequently due to oil shortage.

[0079] Based on the same concept, this application provides a control method for the oil return device of a screw turbine unit, applied to the level sensor in the oil return device of the screw turbine unit provided in this application. Specific implementation of this control method for the oil return device of the screw turbine unit can be found in the description of the method embodiments section; repeated details will not be elaborated upon. Figure 7 As shown, the control method of the screw compressor unit's oil return device mainly includes:

[0080] Step 701: Detect the refrigerant oil level at the compressor's suction end.

[0081] Step 702: When the refrigeration oil level is greater than or equal to the first preset level value, control the first solenoid valve to open and control the second solenoid valve to close.

[0082] If the refrigerant oil level is greater than or equal to the first preset level, it indicates that a large amount of refrigerant oil has accumulated at the compressor's suction end. This refrigerant oil needs to be returned to the compressor's first oil return port to prevent further accumulation and ensure normal compressor operation under low load. By controlling the opening of the first solenoid valve, the refrigerant oil flowing from the bottom of the compressor's suction end, along with the main oil flowing from the oil separator through the first solenoid valve, flows together through the first ejector into the compressor's first oil return port. By controlling the closing of the second solenoid valve, the refrigerant oil flowing from the bottom of the compressor's suction end is prevented from flowing through the second solenoid valve and being directly drawn to the compressor's first oil return port by the oil pump.

[0083] In one specific embodiment, after detecting the refrigerant oil level at the suction end of the compressor, the screw compressor oil return device control method further includes: when the refrigerant oil level is less than a first preset level value, controlling the first solenoid valve to close and controlling the second solenoid valve to close.

[0084] If the refrigerant oil level is lower than the first preset level, it indicates that there is not much refrigerant oil accumulated at the compressor's suction end. This does not affect the compressor's oil return, and there is no need to return the accumulated refrigerant oil at the compressor's suction end to the compressor's first oil return port. Therefore, there is no need to control the opening of the first solenoid valve or the second solenoid valve. At this time, the compressor returns oil through the main oil return line and the evaporator ejector oil return line. If the first solenoid valve is closed, the main oil return can proceed through only one return line. If the first solenoid valve is open, it becomes a two-way oil return, which will affect the oil return flow rate of the line with the third solenoid valve, thereby affecting the ejector oil return at the bottom of the evaporator.

[0085] In one specific embodiment, after controlling the first solenoid valve to open and the second solenoid valve to close, the screw compressor oil return device control method further includes: continuing to detect the refrigerant oil level at the compressor suction end; when the refrigerant oil level is less than or equal to a second preset level value, controlling the first solenoid valve to close, wherein the second preset level value is less than the first preset level value.

[0086] If the refrigerant oil level is less than or equal to the second preset level, it indicates that the refrigerant oil return effect at the compressor's suction end is good, and there is not much refrigerant oil accumulated at the compressor's suction end, so there is no need to open the first solenoid valve. The first solenoid valve does not need to be continuously open; it will only be closed when there is a significant amount of refrigerant oil accumulated at the compressor's suction end. Closing the first solenoid valve when the refrigerant oil level is less than or equal to the second preset level prevents it from being continuously open, which would affect the return oil flow rate in the main oil return line and the evaporator ejector oil return line.

[0087] In one specific embodiment, after controlling the first solenoid valve to open and the second solenoid valve to close, the screw compressor unit oil return device control method further includes: obtaining the opening duration of the first solenoid valve; when the opening duration is greater than or equal to a preset opening duration, controlling the first solenoid valve to close and controlling the second solenoid valve to open.

[0088] When the opening time is greater than or equal to the preset opening time, the first solenoid valve is closed and the second solenoid valve is opened. This prevents the first solenoid valve from being continuously open. Controlling the first solenoid valve to close and the second solenoid valve to open allows the refrigerant oil flowing from the bottom of the compressor's suction end to flow through the second solenoid valve and be directly drawn by the oil pump to the compressor's first oil return port. This results in better oil return of the refrigerant oil accumulated at the bottom of the compressor's suction end and does not affect the oil return flow rate of the main oil return line and the evaporator ejector oil return line.

[0089] In one specific embodiment, after controlling the first solenoid valve to close and the second solenoid valve to open, the screw compressor oil return device control method further includes: continuing to detect the refrigerant oil level at the compressor suction end; when the refrigerant oil level is less than or equal to a second preset level value, controlling the second solenoid valve to close, wherein the second preset level value is less than the first preset level value.

[0090] When the refrigerant oil level is less than or equal to the second preset level, it indicates that the refrigerant oil return effect at the compressor's suction end is very good, and there is not much refrigerant oil accumulated at the compressor's suction end. Therefore, it is not necessary to keep the second solenoid valve open. At this time, the second solenoid valve can be controlled to close.

[0091] In one specific embodiment, such as Figure 8 As shown, the control method of the screw compressor unit oil return device includes:

[0092] Step 801: Detect the refrigerant oil level at the compressor's suction end.

[0093] Step 802: Determine whether the refrigeration oil level is greater than or equal to the first preset level value. If yes, proceed to step 803; otherwise, proceed to step 804.

[0094] Step 803: Control the first solenoid valve to open and control the second solenoid valve to close.

[0095] Step 804: Control the first solenoid valve to close, and control the second solenoid valve to close.

[0096] Step 805: Determine whether the opening duration of the first solenoid valve is greater than or equal to the preset opening duration. If yes, proceed to step 806; otherwise, proceed to step 807.

[0097] Step 806: Control the first solenoid valve to close, control the second solenoid valve to open, and start the oil pump.

[0098] Step 807: Determine whether the refrigeration oil level is less than or equal to the second preset level value. If yes, proceed to step 808; otherwise, proceed to step 809.

[0099] Step 808: Close the first solenoid valve.

[0100] Step 809: Control the first solenoid valve to remain open.

[0101] Step 810: Determine whether the refrigeration oil level is less than or equal to the second preset level value. If yes, proceed to step 811; otherwise, proceed to step 812.

[0102] Step 811: Close the second solenoid valve and shut down the oil pump.

[0103] Step 812: Control the second solenoid valve to remain open and the oil pump to remain open.

[0104] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0105] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A screw compressor unit oil return device, characterized in that, This includes the compressor and the compressor suction end oil return line; The suction end of the compressor is connected to the input end of the suction end oil return line of the compressor, and the output end of the suction end oil return line of the compressor is connected to the first oil return port of the compressor.

2. The screw compressor unit oil return device according to claim 1, characterized in that, The screw compressor unit oil return device also includes an oil separator; the compressor suction end oil return pipeline includes a first solenoid valve and a first ejector. The compressor's suction end is connected to the first input end of the first ejector, the oil separator's output end is connected to the first end of the first solenoid valve, the first solenoid valve's second end is connected to the second input end of the first ejector, and the first ejector's output end is connected to the compressor's first oil return port.

3. The screw compressor unit oil return device according to claim 2, characterized in that, The compressor suction end oil return line also includes a second solenoid valve and an oil pump; The compressor's suction end is connected to the first end of the second solenoid valve, the second end of the second solenoid valve is connected to the first end of the oil pump, and the second end of the oil pump is connected to the compressor's first oil return port.

4. The screw compressor oil return device according to claim 3, characterized in that, The screw compressor unit's oil return device also includes a liquid level sensor; The measuring end of the liquid level sensor is connected to the suction end of the compressor, the first control end of the liquid level sensor is connected to the controlled end of the first solenoid valve, and the second control end of the liquid level sensor is connected to the controlled end of the second solenoid valve.

5. The screw compressor unit oil return device according to claim 4, characterized in that, The screw turbine unit's oil return device also includes a main oil return pipeline; the main oil return pipeline includes a third solenoid valve, a ball valve, a sight glass, and a first oil filter; The output end of the oil separator is connected to the first end of the third solenoid valve, the second end of the third solenoid valve is connected to the first end of the ball valve, the second end of the ball valve is connected to the first end of the sight glass, the second end of the sight glass is connected to the input end of the first oil filter, and the output end of the first oil filter is connected to the first oil return port of the compressor.

6. The screw compressor unit oil return device according to claim 5, characterized in that, The screw compressor unit's oil return device also includes an evaporator and an evaporator ejector oil return line; the evaporator ejector oil return line includes a second oil filter and a second ejector. The output end of the evaporator is connected to the input end of the second oil filter, the output end of the second oil filter is connected to the first input end of the second ejector, the second end of the ball valve is connected to the second input end of the second ejector, and the output end of the second ejector is connected to the second oil return port of the compressor.

7. The screw compressor oil return device according to any one of claims 4 to 6, characterized in that, The liquid level sensor is used to detect the level of refrigerant oil at the suction end of the compressor, and when the level of refrigerant oil is greater than or equal to a first preset level value, it controls the first solenoid valve to open and the second solenoid valve to close.

8. The screw compressor unit oil return device according to claim 7, characterized in that, The liquid level sensor is also used to continue detecting the refrigerant oil level at the suction end of the compressor after controlling the first solenoid valve to open and the second solenoid valve to close. When the refrigerant oil level is less than or equal to a second preset liquid level value, the sensor controls the first solenoid valve to close, wherein the second preset liquid level value is less than the first preset liquid level value.

9. The screw compressor unit oil return device according to claim 7, characterized in that, The liquid level sensor is also used to obtain the opening duration of the first solenoid valve after controlling the first solenoid valve to open and the second solenoid valve to close, and to control the first solenoid valve to close and the second solenoid valve to open when the opening duration is greater than or equal to a preset opening duration.

10. The screw compressor unit oil return device according to claim 9, characterized in that, The liquid level sensor is also used to continue detecting the refrigerant oil level at the suction end of the compressor after controlling the first solenoid valve to close and the second solenoid valve to open. When the refrigerant oil level is less than or equal to a second preset liquid level value, the sensor controls the second solenoid valve to close, wherein the second preset liquid level value is less than the first preset liquid level value.

11. A control method for the oil return device of a screw turbine unit, characterized in that, The level sensor applied in the oil return device of the screw turbine unit according to claim 4, wherein the control method of the oil return device of the screw turbine unit includes: Detect the refrigerant oil level at the suction end of the compressor; When the refrigeration oil level is greater than or equal to a first preset level value, the first solenoid valve is controlled to open and the second solenoid valve is controlled to close.

12. The control method for the oil return device of a screw turbine unit according to claim 11, characterized in that, After controlling the first solenoid valve to open and the second solenoid valve to close, the method further includes: Continue monitoring the refrigerant oil level at the suction end of the compressor; When the refrigeration oil level is less than or equal to a second preset level value, the first solenoid valve is controlled to close, wherein the second preset level value is less than the first preset level value.

13. The control method for the oil return device of a screw turbine unit according to claim 11, characterized in that, After controlling the first solenoid valve to open and the second solenoid valve to close, the method further includes: Obtain the opening duration of the first solenoid valve; When the opening duration is greater than or equal to the preset opening duration, the first solenoid valve is controlled to close and the second solenoid valve is controlled to open.

14. The control method for the oil return device of a screw turbine unit according to claim 13, characterized in that, After controlling the first solenoid valve to close and the second solenoid valve to open, the method further includes: Continue monitoring the refrigerant oil level at the suction end of the compressor; When the refrigeration oil level is less than or equal to a second preset level value, the second solenoid valve is controlled to close, wherein the second preset level value is less than the first preset level value.

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