High-voltage high-temperature screw compressor oil return system and control method

Abstract

The present invention discloses a high-voltage, high-temperature screw compressor oil return system and control method. The oil return system includes a compressor, an oil separator, an oil cooler, a first buffer oil tank, a second buffer oil tank, and a noise-reducing oil filter. The oil separator, oil cooler, first buffer oil tank, compressor, and oil separator are sequentially connected to form a main oil return pipeline. The oil separator, second buffer oil tank, compressor bearing, compressor exhaust port, and oil separator are sequentially connected to form an auxiliary oil return pipeline. The oil separator, noise-reducing oil filter, compressor head, compressor exhaust port, and oil separator are sequentially connected to form a noise-reducing oil return pipeline. A pressure maintaining valve is installed at the exhaust port of the oil separator, and a check valve is installed between the compressor exhaust port and the oil return port of the oil separator. Through the cooperation of the main oil return pipeline, auxiliary oil return pipeline, noise-reducing oil return pipeline, and compressor oil outlet pipeline, efficient, stable, and reliable oil return of the compressor is achieved.

Description

Technical Field

[0001] This invention relates to the field of compressor technology, specifically to a high-voltage, high-temperature screw compressor oil return system and control method. Background Technology

[0002] In the initial design phase, high-voltage high-temperature screw compressors without built-in oil pans utilize external oil pans to avoid excessive compressor size, considering the overall layout of the compressor and heat exchanger. The external oil pan primarily stores lubricating oil. Screw compressors require a sufficient supply of lubricating oil during operation to ensure smooth operation of components such as the screw and bearings, reduce friction and wear, lower operating noise, and provide a seal between the piston and cylinder surfaces, as well as between rotating bearings within the compressor. Oil return is a crucial circulation process for lubricating oil in screw compressors, ensuring effective circulation and utilization of the lubricating oil. High-temperature screw compressors without built-in oil troughs rely on external oil circuit systems for lubricant storage and circulation. Existing products generally use traditional air-driven oil return methods, where the oil return power comes from the difference between the compressor's discharge and suction pressures. This inherently leads to unstable oil return efficiency and a high risk of oil shortage. Furthermore, screw compressors without built-in oil troughs lack a lubricant storage chamber and rely on pipelines and external oil separation components for oil retention and circulation. External oil troughs are prone to causing poor lubricant return to the compressor, resulting in easy lubrication loss after shutdown and insufficient lubrication support upon restart. This leads to a common problem in this type of compressor: insufficient lubricant during startup, resulting in dry running, poor sealing, and even alarm shutdowns due to insufficient lubrication.

[0003] Patent application CN115507034A discloses a lubricating oil circulation system for an oil-injected screw compressor. It discloses that two oil supply and return circulation loops are formed outside the compressor: a main oil supply circulation loop and an oil injection circulation loop. In the main oil supply circulation loop, the lubricating oil from the compressor's return port enters an oil collector. The lubricating oil in the oil collector passes through a filter to remove impurities from the oil collector's outlet. Then, the oil pump pressurizes the lubricating oil, which then enters the compressor through an oil cooler. Alternatively, the oil pump pressurizes the lubricating oil, which then enters the compressor through both the oil cooler and an oil-cooled bypass pipeline. In the oil injection circulation loop, lubricating oil enters the compressor's injection port from the lubricating oil outlet of the oil-gas separator. The lubricating oil in the oil-gas separator is then injected into the rotor cavity's suction side, mixing with the refrigerant. After compression, it re-enters the oil-gas separator for gas-oil separation, forming the oil injection circulation loop. By preventing the lubricating oil in the main oil supply circulation loop from mixing with the refrigerant, the amount of refrigerant dissolved in the lubricating oil is reduced, lowering the lubricating oil dilution and reducing the main oil supply flow rate. The main oil supply flow rate is the flow rate used for lubricating bearings, etc., thus achieving a reduction in the amount of lubricating oil circulating within the oil-injected screw compressor. However, besides improving the external oil supply and return circulation loops of the compressor, improvements to the compressor itself are also needed to modify the internal oil circuit. Improving the return oil circulation by increasing the stability of the lubricating oil concentration still cannot solve the problems of easy lubricating oil loss after shutdown and untimely lubrication upon restart. Therefore, it is necessary to develop an oil return system for a high-voltage, high-temperature screw compressor without a built-in oil trough that can maintain a stable retention of lubricating oil in the oil circuit after shutdown, quickly establish reliable lubrication at the moment the compressor restarts, and maintain a stable oil return state during normal operation of the compressor. Summary of the Invention

[0004] To address existing technical problems, this invention provides a high-voltage, high-temperature screw compressor oil return system and control method. By setting up a main oil return pipeline, an auxiliary oil return pipeline, a noise-reducing oil return pipeline, and a compressor oil outlet pipeline in coordination, the system achieves stable retention of lubricating oil in the oil circuit after the compressor stops, rapidly establishes reliable lubrication upon compressor restart, and maintains a stable oil return state during normal operation, significantly improving the unit's operational safety, stability, and service life.

[0005] The technical solution of the present invention is: a high-voltage high-temperature screw compressor oil return system, comprising a compressor, an oil separator, an oil cooler, a first buffer oil tank, a second buffer oil tank, and a noise-reducing oil filter;

[0006] The oil outlet of the oil separator, the oil cooler, the first buffer oil tank, the oil return port of the compressor, the exhaust port of the compressor, and the oil return port of the oil separator are connected in sequence to form the main oil return pipeline.

[0007] A main oil circuit angle valve is installed between the oil outlet of the oil separator and the oil cooler, and a main return oil circuit closing solenoid valve and a main return oil circuit flow switch are installed between the first buffer oil tank and the return oil port of the compressor.

[0008] The oil outlet of the oil separator, the second buffer oil tank, the compressor bearing, the compressor exhaust port, and the oil return port of the oil separator are sequentially connected to form an auxiliary oil return pipeline; the compressor bearing includes the compressor middle section bearing and the compressor top bearing, and the second buffer oil tank is connected to the compressor middle section bearing and the compressor top bearing respectively.

[0009] An auxiliary oil circuit angle valve is installed between the oil outlet of the oil separator and the second buffer oil tank; a motor bearing closing solenoid valve and a motor bearing oil supply flow switch are installed between the second buffer oil tank and the compressor bearing; and a compressor top bearing oil supply angle valve is installed between the second buffer oil tank and the compressor top bearing.

[0010] Both the first and second buffer oil tanks are connected to the compressor's pressure relief solenoid valve.

[0011] The oil outlet of the oil separator, the oil filter of the noise reduction oil circuit, the compressor head, the compressor exhaust port and the oil return port of the oil separator are connected in sequence to form a noise reduction oil return pipeline;

[0012] An auxiliary oil circuit angle valve is installed between the oil outlet of the oil separator and the oil filter of the noise reduction oil circuit. An oil injection noise reduction oil supply flow switch is installed between the oil filter of the noise reduction oil circuit and the compressor head. The compressor head has two sides. An oil injection noise reduction solenoid valve I is installed between the oil injection noise reduction oil supply flow switch and the compressor head on one side, and an oil injection noise reduction solenoid valve II is installed between the oil injection noise reduction oil supply flow switch and the compressor head on the other side.

[0013] A pressure maintaining valve is installed at the exhaust port of the oil separator, and a check valve is installed between the exhaust port of the compressor and the oil return port of the oil separator.

[0014] Furthermore, the high-voltage, high-temperature screw compressor oil return system also includes a coil heat exchanger, and the oil return hole at the bottom of the compressor, the coil heat exchanger, and the compressor's suction port are sequentially connected to form the compressor oil return circuit.

[0015] Furthermore, the compressor's exhaust port is sequentially connected to an oil separator, a condenser, an electronic expansion valve, an evaporator, and the compressor's suction port to form a refrigerant main circulation loop.

[0016] Furthermore, the outlet of the condenser is connected in sequence to the oil cooler and the evaporator.

[0017] Furthermore, the exhaust port of the oil separator is connected in sequence to the coil heat exchanger and the evaporator.

[0018] Furthermore, the pressure maintaining valve is located between the exhaust port of the oil separator and the condenser.

[0019] A control method for the oil return system of a high-voltage, high-temperature screw compressor includes the following steps:

[0020] S1. When the compressor starts, a high-pressure environment is formed in the oil separator under the action of the pressure maintaining valve, which provides power for the return oil. The lubricating oil inside the oil separator is sent to the compressor through the main return oil line, the auxiliary return oil line and the noise reduction return oil line, and then sent to the compressor for lubrication and sealing.

[0021] In the main return oil pipeline, the lubricating oil passes through the oil separator, the main oil circuit angle valve, the oil cooler and the first buffer oil tank in sequence. The main return oil circuit closing solenoid valve is opened, and the flow rate of the lubricating oil is adjusted by the main return oil circuit flow switch. The appropriate amount of lubricating oil is controlled to be delivered from the first buffer oil tank to the return oil port of the compressor. The lubricating oil after lubrication in the compressor enters the oil separator with the compressor exhaust.

[0022] In the auxiliary return oil pipeline, the lubricating oil passes through the oil separator, the auxiliary oil line angle valve and the second buffer oil tank in sequence. The motor bearing closing solenoid valve is opened, and the flow rate of the lubricating oil is adjusted by the motor bearing oil supply flow switch. The lubricating oil is divided into two paths: one path is directly supplied to the middle bearing of the compressor, and the other path is supplied to the top bearing of the compressor by adjusting the flow rate of the lubricating oil through the compressor top bearing oil supply angle valve. The lubricating oil after bearing lubrication enters the oil separator with the compressor exhaust.

[0023] In the noise reduction return oil pipeline, the lubricating oil passes through the oil separator, the auxiliary oil line angle valve and the noise reduction oil line oil filter in sequence. The flow rate of the lubricating oil is controlled by the oil injection noise reduction supply flow switch, and the amount of lubricating oil injected at the compressor head position on both sides is controlled by the opening degree of the oil injection noise reduction solenoid valve I and the oil injection noise reduction solenoid valve II. After the noise reduction lubrication is completed, the lubricating oil enters the oil separator with the compressor exhaust.

[0024] S2. During normal operation, the compressor is continuously replenished with lubricating oil through the main return oil line, the auxiliary return oil line, and the noise reduction return oil line. The pressure relief solenoid valve remains open to balance the pressure in the first and second buffer oil tanks.

[0025] When the lubricating oil is used for lubrication and sealing inside the compressor, it is also circulated back through the compressor oil return circuit. In the compressor oil return circuit, the lubricating oil and refrigerant at the bottom of the compressor enter the coil heat exchanger through the oil return hole at the bottom of the compressor. After being heated in the coil heat exchanger, the liquid refrigerant evaporates and mixes with the lubricating oil, and enters the compressor suction port along with the compressor suction process.

[0026] S3. When the compressor stops, the compressor oil return circuit stops returning oil, the control pressure maintaining valve closes, the check valve closes, the main oil return circuit closing solenoid valve, the motor bearing closing solenoid valve, the oil injection noise reduction solenoid valve I and the oil injection noise reduction solenoid valve II close, and the main oil return line, the auxiliary oil return line and the noise reduction oil return line stop returning oil.

[0027] By adopting the above technical solution, the beneficial effects achieved by the present invention are as follows:

[0028] (1) The present invention, through the cooperation of structural devices and control methods such as compressor, oil separator, oil cooler, first buffer oil tank, second buffer oil tank, noise reduction oil filter, pressure maintaining valve and check valve, maintains the stable retention of lubricating oil in the oil circuit after the compressor stops and is not easily lost. It quickly establishes reliable lubrication and timely lubrication at the moment the compressor restarts, and maintains a stable and good oil return state when the compressor is running normally, which significantly improves the operating safety, stability and service life of the unit.

[0029] (2) This invention establishes a main return oil pipeline, an auxiliary return oil pipeline and a noise reduction return oil pipeline to continuously supply oil to different positions of the compressor, such as the middle bearing, the top bearing, the two sides of the compressor head and the interior, so as to achieve good lubrication and sealing effect of the compressor. In addition, since the flow and lubricating oil demand of the first buffer oil tank and the second buffer oil tank to different positions of the compressor are different, flow switches are added to different return oil pipelines for precise calculation and control to meet the oil supply needs of different positions of the compressor.

[0030] (3) The present invention does not require any modification to the compressor structure. The oil return power no longer depends on the difference between the compressor discharge pressure and the suction pressure. Instead, a high-pressure environment is quickly formed in the oil separator through the pressure maintaining valve to provide power for oil return. The pressure in the first buffer oil tank and the second buffer oil tank are balanced by the pressure relief solenoid valve to ensure the continuous power of oil return, which significantly improves the efficiency and stability of oil return. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the oil return system of the high-voltage, high-temperature screw compressor of the present invention;

[0032] Figure 2 This is a schematic diagram of the main return oil pipeline of the present invention;

[0033] Figure 3 This is a schematic diagram of the auxiliary return oil pipeline of the present invention;

[0034] Figure 4 This is a schematic diagram of the compressor's side angle in the noise reduction return oil pipeline of the present invention;

[0035] Figure 5This is a schematic diagram of the compressor's other side angle in the noise reduction return oil pipeline of the present invention.

[0036] In the diagram, 1. Compressor; 2. Oil separator; 3. Oil cooler; 4. First buffer oil tank; 5. Second buffer oil tank; 6. Noise-reducing oil circuit oil filter; 7. Pressure relief solenoid valve; 8. Pressure maintaining valve; 9. Check valve; 10. Coil-type heat exchanger; 11. Main oil circuit angle valve; 12. Main return oil circuit closing solenoid valve; 13. Main return oil circuit flow switch; 21. Auxiliary oil circuit angle valve; 22. Motor bearing closing solenoid valve; 23. Motor bearing oil supply flow switch; 24. Compressor top bearing oil supply angle valve; 31. Oil injection noise reduction oil supply flow switch; 32. Oil injection noise reduction solenoid valve I; 33. Oil injection noise reduction solenoid valve II; 41. Condenser; 42. Evaporator; 43. Electronic expansion valve. Detailed Implementation

[0037] The present invention will be further described in detail below with reference to specific embodiments.

[0038] Example 1

[0039] like Figures 1-5 As shown, because the compressor heads on both sides are symmetrical (in the prior art), they cannot be shown in the same attached drawing. Only one side of the compressor head can be shown in a single attached drawing. Figure 1 , Figure 4 and Figure 5 The dashed line in the diagram represents the connection circuit of the compressor head on the other side of the obscured part of the compressor.

[0040] A high-voltage, high-temperature screw compressor oil return system includes a compressor 1, an oil separator 2, an oil cooler 3, a first buffer oil tank 4, a second buffer oil tank 5, and a noise-reducing oil filter 6.

[0041] The oil outlet of the oil separator 2, the oil cooler 3, the first buffer oil tank 4, the oil return port of the compressor 1, the exhaust port of the compressor 1 and the oil return port of the oil separator 2 are connected in sequence to form the main oil return pipeline.

[0042] The lubricating oil entering the oil separator 2 through the exhaust port of compressor 1 is at an excessively high temperature. To prevent the lubricating oil from becoming too hot and reducing its effectiveness, an oil cooler 3 is installed to cool it down.

[0043] A main oil circuit angle valve 11 is provided between the oil outlet of the oil separator 2 and the oil cooler 3, and a main return oil circuit closing solenoid valve 12 and a main return oil circuit flow switch 13 are provided between the first buffer oil tank 4 and the return oil port of the compressor 1.

[0044] The oil outlet of the oil separator 2, the second buffer oil tank 5, the bearing of the compressor 1, the exhaust port of the compressor 1, and the return oil port of the oil separator 2 are sequentially connected to form an auxiliary return oil pipeline; the bearing of the compressor 1 includes the middle section bearing of the compressor 1 and the top bearing of the compressor 1, and the second buffer oil tank 5 is connected to the middle section bearing of the compressor 1 and the top bearing of the compressor 1 respectively.

[0045] An auxiliary oil circuit angle valve 21 is provided between the oil outlet of the oil separator 2 and the second buffer oil tank 5; a motor bearing closing solenoid valve 22 and a motor bearing oil supply flow switch 23 are provided between the second buffer oil tank 5 and the bearing of the compressor 1; and a compressor top bearing oil supply angle valve 24 is provided between the second buffer oil tank 5 and the top bearing of the compressor 1.

[0046] The lubricating oil in the auxiliary return oil line is divided into two paths after exiting the second buffer oil tank 5. One path directly supplies the middle bearing of the compressor 1, and the other path supplies the top bearing of the compressor 1 through the compressor top bearing oil supply angle valve 24. The flow rate of lubricating oil to the top bearing of the compressor 1 can be manually controlled by the compressor top bearing oil supply angle valve 24, based on the motor bearing closed solenoid valve 22 and the motor bearing oil supply flow switch 23, so as to meet the oil supply needs of the compressor 1.

[0047] The first buffer oil tank 4 and the second buffer oil tank 5 are both connected to the pressure relief solenoid valve 7 of the compressor 1;

[0048] The pressure difference between the first buffer oil tank 4, the second buffer oil tank 5 and the compressor 1 is achieved by controlling the opening and closing of the pressure relief solenoid valve 7, thus ensuring pressure balance.

[0049] The oil outlet of the oil separator 2, the noise-reducing oil filter 6, the compressor head of the compressor 1, the exhaust port of the compressor 1, and the oil return port of the oil separator 2 are connected in sequence to form a noise-reducing oil return pipeline.

[0050] An auxiliary oil circuit angle valve 21 is installed between the oil outlet of the oil separator 2 and the noise reduction oil circuit filter 6. An oil injection noise reduction oil supply flow switch 31 is installed between the noise reduction oil circuit filter 6 and the compressor head of the compressor 1. The compressor head of the compressor 1 has two sides. An oil injection noise reduction solenoid valve I 32 is installed between the oil injection noise reduction oil supply flow switch 31 and the compressor head on one side of the compressor 1. An oil injection noise reduction solenoid valve II 33 is installed between the oil injection noise reduction oil supply flow switch 31 and the compressor head on the other side of the compressor 1.

[0051] Because high-voltage, high-temperature screw compressors are noisy, this noise-reducing oil return line is designed to reduce noise while lubricating the compressor 1 with lubricating oil. Under the action of the oil injection noise reduction oil supply flow switch 31, the oil injection flow is precisely controlled by controlling the opening and closing of the oil injection noise reduction solenoid valve I 32 and the oil injection noise reduction solenoid valve II 33, so as to spray oil at both sides of the compressor head to achieve lubrication and noise reduction.

[0052] A pressure maintaining valve 8 is installed at the exhaust port of the oil separator 2, and a check valve 9 is installed between the exhaust port of the compressor 1 and the oil return port of the oil separator 2.

[0053] Furthermore, the high-voltage high-temperature screw compressor oil return system also includes a coil heat exchanger 10, and the oil return hole at the bottom of the compressor 1, the coil heat exchanger 10 and the suction port of the compressor 1 are connected in sequence to form a compressor oil return circuit.

[0054] During normal operation, some of the lubricating oil in compressor 1 is not discharged with the compressor discharge. Under the action of gravity, it collects at the bottom of compressor 1. Through the compressor oil return line, the lubricating oil and a small amount of refrigerant that were not discharged with the compressor discharge flow out through the oil return hole at the bottom of compressor 1 and enter the coil heat exchanger 10 for heat exchange. This allows a small amount of liquid refrigerant to evaporate and mix with the lubricating oil, entering the suction port of compressor 1 during the suction process, so as to realize the compressor suction and lubricating oil recycling.

[0055] Furthermore, the exhaust port of the compressor 1 is sequentially connected to the oil separator, condenser 41, electronic expansion valve 43, evaporator 42 and the suction port of the compressor 1 to form a refrigerant main circulation loop.

[0056] Furthermore, the outlet of the condenser 41 is also connected in sequence to the oil cooler 3 and the evaporator 42.

[0057] When the lubricating oil in the oil separator 2 is cooled by the oil cooler 3, the cold source comes from the refrigerant in the condenser 41.

[0058] Furthermore, the exhaust port of the oil separator 2 is also connected in sequence to the coil heat exchanger 10 and the evaporator 42.

[0059] The high-temperature refrigerant from the exhaust port of compressor 1 is discharged through the exhaust port of oil separator 2 and then enters coil heat exchanger 10. In coil heat exchanger 10, the lubricating oil and a small amount of refrigerant flowing out of the oil return hole at the bottom of compressor 1 in the compressor oil return circuit and entering coil heat exchanger 10 are heated.

[0060] Furthermore, the pressure maintaining valve 8 is disposed between the exhaust port of the oil separator 2 and the condenser 41.

[0061] A control method for the oil return system of a high-voltage, high-temperature screw compressor includes the following steps:

[0062] S1. When the compressor 1 is turned on, under the action of the pressure maintaining valve 8, a high-pressure environment is formed in the oil separator 2 to provide power for oil return. The lubricating oil inside the oil separator 2 is sent to the compressor 1 through the main oil return pipeline, the auxiliary oil return pipeline and the noise reduction oil return pipeline, and then sent to the compressor 1 for lubrication and sealing.

[0063] In the main return oil pipeline, the lubricating oil passes sequentially through the oil separator 2, the main oil circuit angle valve 11, the oil cooler 3, and the first buffer oil tank 4. The main return oil circuit closing solenoid valve 12 is opened, and the flow rate of the lubricating oil is regulated by the main return oil circuit flow switch 13. A suitable amount of lubricating oil is controlled to be delivered from the first buffer oil tank 4 to the return oil port of the compressor 1. After lubrication within the compressor 1, the lubricating oil enters the oil separator 2 along with the compressor exhaust (e.g., ...). Figure 2 (as shown)

[0064] In the auxiliary oil return pipeline, the lubricating oil passes sequentially through the oil separator 2, the auxiliary oil line angle valve 21, and the second buffer oil tank 5. The motor bearing closing solenoid valve 22 is opened, and the flow rate of the lubricating oil is regulated by the motor bearing oil supply flow switch 23. The lubricating oil is divided into two paths: one path directly supplies the intermediate bearing of the compressor 1, and the other path regulates the flow rate of the lubricating oil through the compressor top bearing oil supply angle valve 24 and supplies it to the top bearing of the compressor 1. The lubricating oil after bearing lubrication enters the oil separator 2 along with the compressor exhaust (e.g., ...). Figure 3 (as shown)

[0065] In the noise reduction return oil pipeline, the lubricating oil passes sequentially through the oil separator 2, the auxiliary oil line angle valve 21, and the noise reduction oil line filter 6. The flow rate of the lubricating oil is controlled by the oil injection noise reduction supply flow switch 31, and the amount of lubricating oil injected at the compressor head positions on both sides of the compressor 1 is controlled by the opening and closing degree of the oil injection noise reduction solenoid valve I 32 and the oil injection noise reduction solenoid valve II 33. After the noise reduction lubrication is completed, the lubricating oil enters the oil separator 2 along with the compressor exhaust (e.g., ...). Figure 4 and Figure 5 (as shown)

[0066] When compressor 1 is turned on, under the action of pressure maintaining valve 8, a high-pressure environment can be quickly formed in oil separator 2 to provide power for oil return and send the lubricating oil inside oil separator 2 to various positions inside compressor 1 for lubrication and sealing. Considering that the flow from the first buffer oil tank 4 and the second buffer oil tank 5 to different positions of compressor 1 and the different lubricating oil requirements are different, flow switches are added in different oil return pipelines to accurately calculate and meet the oil supply requirements of different positions of compressor 1.

[0067] S2. During normal operation, the compressor 1 is continuously replenished with lubricating oil through the main return oil line, auxiliary return oil line, and noise-reducing return oil line. The pressure relief solenoid valve 7 remains open to balance the pressure in the first buffer oil tank 4 and the second buffer oil tank 5 (e.g., Figure 1 (As shown in the content of the middle frame I).

[0068] When the lubricating oil lubricates and seals inside the compressor 1, it also circulates back through the compressor oil return circuit. In the compressor oil return circuit, the lubricating oil and refrigerant at the bottom of the compressor 1 enter the coil heat exchanger 10 through the oil return hole at the bottom of the compressor 1. After being heated in the coil heat exchanger 10, the liquid refrigerant evaporates and mixes with the lubricating oil, entering the suction port of the compressor 1 (e.g., during the suction process of the compressor 1) Figure 1 (As shown in the content of middle frame II);

[0069] When compressor 1 is running normally, the high-efficiency oil separator 2 "captures" the lubricating oil mist in the high-speed gas to a great extent, preventing the lubricating oil mist from entering the downstream with the high-speed gas, and keeping the lubricating oil in the oil separator 2 to the greatest extent, so as to ensure that compressor 1 has a sufficient oil supply source and prevent lubricating oil from flowing into condenser 41 and evaporator 42, so as to realize the continuous replenishment of lubricating oil for compressor by the main oil return line, auxiliary oil return line and noise reduction oil return line.

[0070] When compressor 1 is running normally, if the internal lubricating oil of compressor 1 is used to lubricate and seal related parts, the lubricating oil may not be completely discharged with the compressor exhaust. Under the action of gravity, the lubricating oil that is not discharged with the compressor exhaust and a small amount of refrigerant flow out from the oil outlet at the bottom of compressor 1 and enter the coil heat exchanger 10 for heating. This causes the refrigerant in the oil return line to evaporate, preventing liquid from entering the compressor suction. The evaporated refrigerant, mixed with lubricating oil, enters the suction port of compressor 1 during the suction process, increasing the amount of oil returned and increasing the circulation of lubricating oil in compressor 1.

[0071] S3. When the compressor 1 stops, the compressor oil return circuit stops returning oil, the control pressure maintaining valve 8 closes, the check valve 9 closes, the main oil return circuit closing solenoid valve 12, the motor bearing closing solenoid valve 22, the oil injection noise reduction solenoid valve I 32 and the oil injection noise reduction solenoid valve II 33 close, and the main oil return line, auxiliary oil return line and noise reduction oil return line stop returning oil.

[0072] When compressor 1 stops, the compressor head ceases to work, and the pressure at the discharge end of compressor 1 rapidly decreases to below the pressure inside oil separator 2. At this time, the check valve at the discharge port of compressor 1 closes to prevent gas backflow from causing compressor 1 to reverse, thus preventing the lubricating oil of compressor 1 from being "drawn" out of the lubrication channel and entering evaporator 42. The main oil return line, auxiliary oil return line, and noise reduction oil return line stop returning oil to prevent lubricating oil in the oil supply line and oil separator 2 from entering the evaporator, ensuring oil supply conditions for the next startup.

[0073] In the high-voltage, high-temperature screw compressor oil return system of this embodiment 1, when the compressor 1 is running, the refrigerant circulates through the main refrigerant circulation loop. The refrigerant is compressed inside the compressor 1 and mixes with some of the lubricating oil inside the compressor 1. Both are discharged from the exhaust port of the compressor 1 and enter the oil separator 2. Inside the oil separator 2, the lubricating oil is filtered and retained at the bottom of the oil separator 2. Only the refrigerant enters the condenser 41 through the exhaust port of the oil separator 2 for heat exchange. After heat exchange, the refrigerant first passes through the electronic expansion valve 43 for throttling before entering the evaporator 42. After heat exchange is completed in the evaporator 42, it re-enters the compressor 1 through the suction port, completing the main refrigerant circulation (e.g., ...). Figures 1-5 (As shown by the black lines in the middle). In step S1, the refrigerant in the condenser 41 is sent to the oil cooler 3 to cool the lubricating oil. After heat exchange, the refrigerant flows through the pipe to the evaporator 42, and together with the refrigerant in the evaporator 42, it is sent to the suction port of the compressor 1. The refrigerant is compressed in the compressor 1 and then discharged from the discharge port of the compressor 1, entering the oil separator 2. After passing through the discharge port of the oil separator 2, it is sent to the condenser 41, completing the refrigerant cooling cycle (as shown by the black lines in the middle). Figures 1-5 (As shown by the blue line in the middle). In step S2, in addition to the main refrigerant cycle and the refrigerant cooling cycle, the following cycle is also included: The high-temperature refrigerant drawn from the discharge port of compressor 1 is delivered to oil separator 2, and after being discharged from the discharge port of oil separator 2, it enters coil heat exchanger 10. In coil heat exchanger 10, it heats the lubricating oil flowing out of the oil return hole at the bottom of compressor 1 and a small amount of refrigerant. After the high-temperature refrigerant completes heat exchange in coil heat exchanger 10, it enters evaporator 42 and is finally delivered back to the suction port of compressor 1, completing the refrigerant heating cycle (as shown by the blue line in the middle). Figures 1-5 (As shown by the blue line).

Claims

1. A high-voltage, high-temperature screw compressor oil return system, characterized in that: Includes compressor (1), oil separator (2), oil cooler (3), first buffer oil tank (4), second buffer oil tank (5), and noise reduction oil filter (6); The oil outlet of the oil separator (2), the oil cooler (3), the first buffer oil tank (4), the oil return port of the compressor (1), the exhaust port of the compressor (1) and the oil return port of the oil separator (2) are connected in sequence to form the main oil return pipeline. The oil outlet of the oil separator (2), the second buffer oil tank (5), the bearing of the compressor (1), the exhaust port of the compressor (1) and the return oil port of the oil separator (2) are connected in sequence to form an auxiliary return oil pipeline; the bearing of the compressor (1) includes the middle section bearing of the compressor (1) and the top bearing of the compressor (1), and the second buffer oil tank (5) is connected to the middle section bearing of the compressor (1) and the top bearing of the compressor (1) respectively; The first buffer oil tank (4) and the second buffer oil tank (5) are both connected to the pressure relief solenoid valve (7) of the compressor (1); The oil outlet of the oil separator (2), the oil filter (6) of the noise reduction oil circuit, the head of the compressor (1), the exhaust port of the compressor (1) and the oil return port of the oil separator (2) are connected in sequence to form a noise reduction oil return pipeline. A pressure maintaining valve (8) is provided at the exhaust port of the oil separator (2), and a check valve (9) is provided between the exhaust port of the compressor (1) and the oil return port of the oil separator (2).

2. The oil return system for a high-voltage, high-temperature screw compressor according to claim 1, characterized in that: A main oil circuit angle valve (11) is installed between the oil outlet of the oil separator (2) and the oil cooler (3) in the main oil return pipeline, and a main oil return circuit closing solenoid valve (12) and a main oil return circuit flow switch (13) are installed between the first buffer oil tank (4) and the return oil port of the compressor (1).

3. The oil return system for a high-voltage, high-temperature screw compressor according to claim 1, characterized in that: An auxiliary oil line angle valve (21) is installed between the oil outlet of the oil separator (2) and the second buffer oil tank (5) in the auxiliary return oil line. A motor bearing closing solenoid valve (22) and a motor bearing oil supply flow switch (23) are installed between the second buffer oil tank (5) and the bearing of the compressor (1). A compressor top bearing oil supply angle valve (24) is installed between the second buffer oil tank (5) and the top bearing of the compressor (1).

4. The oil return system for a high-voltage, high-temperature screw compressor according to claim 1, characterized in that: An auxiliary oil circuit angle valve (21) is provided between the oil outlet of the oil separator (2) in the noise reduction oil return pipeline and the oil filter (6) in the noise reduction oil circuit. An oil injection noise reduction oil supply flow switch (31) is provided between the oil filter (6) in the noise reduction oil circuit and the head of the compressor (1). The head of the compressor (1) has two sides. An oil injection noise reduction solenoid valve I (32) is provided between the oil injection noise reduction oil supply flow switch (31) and the head of the compressor (1) on one side. An oil injection noise reduction solenoid valve II (33) is provided between the oil injection noise reduction oil supply flow switch (31) and the head of the compressor (1) on the other side.

5. The oil return system for a high-voltage, high-temperature screw compressor according to claim 1, characterized in that: The high-voltage high-temperature screw compressor oil return system also includes a coil heat exchanger (10). The oil return hole at the bottom of the compressor (1), the coil heat exchanger (10), and the suction port of the compressor (1) are connected in sequence to form the compressor oil return circuit.

6. The oil return system for a high-voltage, high-temperature screw compressor according to claim 1, characterized in that: The exhaust port of the compressor (1) is connected in sequence to the oil separator (2), condenser (41), electronic expansion valve (43), evaporator (42) and the suction port of the compressor (1) to form the main refrigerant circulation loop.

7. The oil return system for a high-voltage, high-temperature screw compressor according to claim 6, characterized in that: The outlet of the condenser (41) is also connected in sequence to the oil cooler (3) and the evaporator (42), and the exhaust port of the oil separator (2) is also connected in sequence to the coil heat exchanger (10) and the evaporator (42).

8. The oil return system for a high-voltage, high-temperature screw compressor according to claim 6, characterized in that: The pressure maintaining valve (8) is located between the exhaust port of the oil separator (2) and the condenser (41).

9. A control method for the oil return system of a high-voltage, high-temperature screw compressor as described in any one of claims 1-8, characterized in that: Includes the following steps: S1. When the compressor (1) is turned on, a high-pressure environment is formed in the oil separator (2) under the action of the pressure maintaining valve (8), which provides power for the return oil and sends the lubricating oil inside the oil separator (2) to the compressor (1) through the main return oil pipeline, the auxiliary return oil pipeline and the noise reduction return oil pipeline, and then sends it to the compressor (1) for lubrication and sealing. In the main return oil pipeline, the lubricating oil passes through the oil separator (2), the main oil line angle valve (11), the oil cooler (3) and the first buffer oil tank (4) in sequence. The main return oil line closing solenoid valve (12) is opened, and the flow rate of the lubricating oil is adjusted by the main return oil line flow switch (13). The appropriate amount of lubricating oil is controlled to be delivered from the first buffer oil tank (4) to the return oil port of the compressor (1). The lubricating oil after being lubricated in the compressor (1) enters the oil separator (2) with the compressor exhaust. In the auxiliary return oil pipeline, the lubricating oil passes through the oil separator (2), the auxiliary oil line angle valve (21), and the second buffer oil tank (5) in sequence. The motor bearing closing solenoid valve (22) is opened, and the flow rate of the lubricating oil is adjusted by the motor bearing oil supply flow switch (23). The lubricating oil is divided into two paths. One path is directly supplied to the middle bearing of the compressor (1), and the other path is adjusted by the compressor top bearing oil supply angle valve (24) and supplied to the top bearing of the compressor (1). The lubricating oil after bearing lubrication enters the oil separator (2) with the compressor exhaust. In the noise reduction return oil pipeline, the lubricating oil passes through the oil separator (2), the auxiliary oil line angle valve (21), and the noise reduction oil line oil filter (6) in sequence. The flow rate of the lubricating oil is controlled by the oil injection noise reduction supply flow switch (31), and the amount of lubricating oil injected at the head position on both sides of the compressor (1) is controlled by the opening and closing degree of the oil injection noise reduction solenoid valve I (32) and the oil injection noise reduction solenoid valve II (33). After the noise reduction lubrication is completed, the lubricating oil enters the oil separator (2) with the compressor exhaust. S2. During normal operation, the compressor (1) is continuously replenished with lubricating oil through the main return oil line, the auxiliary return oil line and the noise reduction return oil line. The pressure relief solenoid valve (7) is kept open to balance the pressure in the first buffer oil tank (4) and the second buffer oil tank (5). When the lubricating oil is used for lubrication and sealing inside the compressor (1), it is also circulated back through the compressor oil return circuit. In the compressor oil return circuit, the lubricating oil and refrigerant at the bottom of the compressor (1) enter the coil heat exchanger (10) through the oil return hole at the bottom of the compressor (1). After being heated in the coil heat exchanger (10), the liquid refrigerant evaporates and mixes with the lubricating oil, and enters the suction port of the compressor (1) along with the suction process of the compressor (1). S3. When the compressor (1) stops, the compressor oil return circuit stops returning oil, the control pressure maintaining valve (8) closes, the check valve (9) closes, the main oil return circuit closing solenoid valve (12), the motor bearing closing solenoid valve (22), the oil injection noise reduction solenoid valve I (32) and the oil injection noise reduction solenoid valve II (33) close, and the main oil return line, auxiliary oil return line and noise reduction oil return line stop returning oil.

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