A multi-shaft multi-stage centrifugal compressor for high-temperature heat pump

Abstract

The present invention relates to the technical field of multi-stage centrifugal compressors, and discloses a multi-shaft multi-stage centrifugal compressor for a high-temperature heat pump, comprising an input shaft, an output shaft and a gearbox, wherein the input shaft and the output shaft are mounted on the gearbox, the input shaft is connected to the output shaft through a gear set, a primary compressor is mounted on one end of the output shaft, a secondary compressor is mounted on the other end of the output shaft, and an exhaust compressor is also included, a primary sealing device is provided at the connection between the primary compressor and the gearbox, a secondary sealing device is provided at the connection between the secondary compressor and the gearbox, the primary sealing device is communicated with the secondary sealing device, the secondary sealing device is communicated with the exhaust compressor through an exhaust pipeline, the exhaust compressor is mounted on the input shaft, and the exhaust compressor delivers a working medium to a working medium system. The present invention reduces the leakage of the working medium and improves the sealing effect by arranging a sealing device between the compressor and the gearbox.

Description

Technical Field

[0001] The invention relates to the technical field of multi-stage centrifugal compressors, and in particular to a multi-shaft multi-stage centrifugal compressor for a high-temperature heat pump. Background Art

[0002] The driving source of multi-stage centrifugal compressors on the market currently mainly relies on the drive of the gearbox. The input and output shafts of the gearbox rotate at extremely high speeds. In order to reduce friction loss, the shaft and the box are designed to be non-contact. However, this design brings the risk of high-pressure working fluids penetrating into the gearbox, resulting in a series of problems, which are specifically reflected in the following aspects:

[0003] 1. Sealing performance challenge: In high-temperature heat pump units, the working fluid pressure is relatively high due to system operation requirements. The special requirements of high temperature and high pressure working conditions cause the sealing effect of the sealing device at the junction of the compressor impeller back and the gearbox to deteriorate sharply, resulting in a significant increase in the amount of working fluid leaking into the gearbox, which in turn leads to a sharp increase in leakage losses.

[0004] 2. Large windage loss in the gearbox: The density and pressure of the oil-gas mixture in the gearbox are important factors affecting windage loss. Leakage at the back of the compressor impeller causes the pressure and density of the oil-gas mixture in the box to increase continuously, which in turn increases windage loss, significantly reduces the transmission efficiency of the gearbox, and leads to energy waste and increased costs.

[0005] 3. Insufficient pressure bearing capacity of the box: In high-temperature heat pump units, due to the leakage of high-pressure working fluid at the back of the compressor impeller, the gearbox often needs to withstand higher pressure. The design of traditional centrifugal compressor gearboxes often does not fully consider the operating requirements under such high-pressure conditions, resulting in limited pressure bearing capacity of the box. After long-term operation, the box may deform, leak or even rupture due to the inability to withstand the internal high pressure, which may lead to serious equipment failures and safety hazards.

[0006] 4. Lubricant loss problem: Under high temperature and high pressure conditions, part of the lubricant may be vaporized. The vaporized lubricant and the working fluid are discharged from the gearbox together. Continuous lubricant loss may lead to insufficient lubricant in the gearbox, thus affecting the lubrication effect of the gear and the life of the gearbox. Summary of the invention

[0007] In view of the existing technical problems, the present invention provides a multi-shaft multi-stage centrifugal compressor for a high-temperature heat pump.

[0008] The technical solution of the present invention for solving the above-mentioned technical problems is as follows: a multi-shaft multi-stage centrifugal compressor for a high-temperature heat pump, comprising an input shaft, an output shaft and a gear box, wherein the input shaft and the output shaft are mounted on the gear box, the input shaft is transmission-connected to the output shaft through a gear set, a first-stage compressor is mounted on one end of the output shaft, a second-stage compressor is mounted on the other end of the output shaft, and also comprises an exhaust compressor, a first-stage sealing device is provided at the connection between the first-stage compressor and the gear box, a second-stage sealing device is provided at the connection between the second-stage compressor and the gear box, the first-stage sealing device is communicated with the second-stage sealing device, the second-stage sealing device is communicated with the exhaust compressor through an exhaust pipeline, the exhaust compressor is mounted on the input shaft, and the exhaust compressor transports the working fluid to the working fluid system.

[0009] On the basis of the above technical solution, the present invention can also be improved as follows:

[0010] Preferably, the input shaft is mounted on the gear box via a sliding bearing, a plurality of air guide holes are provided on the sliding bearing, and an inner cavity of the gear box is connected to the air extraction compressor via the air guide holes.

[0011] Preferably, a plurality of labyrinth seals are provided in the primary sealing device and the secondary sealing device, and a plurality of sealing teeth are provided in the labyrinth seal.

[0012] Preferably, the primary sealing device includes a primary high-pressure sealing chamber and a primary low-pressure sealing chamber, the secondary sealing device includes a secondary low-pressure sealing chamber and a secondary high-pressure sealing chamber, the secondary high-pressure sealing chamber is connected to the primary low-pressure sealing chamber through a bypass line, and a throttle valve is provided on the bypass line.

[0013] Preferably, a spiral air guide vane is installed on the output shaft, and the spiral air guide vane extends spirally along the output shaft. The spiral air guide vane is respectively arranged at the connection between the secondary sealing device and the gear box and at the connection between the primary sealing device and the gear box. The spiral air guide vane forms a first lead and a second lead on the output shaft, the pitch of the first lead is greater than the pitch of the second lead, and the first lead is arranged close to the gear box.

[0014] Preferably, a diffuser section is formed between the spiral air guide vane and the primary sealing device, and between the spiral air guide vane and the secondary sealing device, and an angle δ of the diffuser section is 25°-30°.

[0015] Preferably, the gap between the outer edge of the spiral air guide plate and the inner wall of the gear box is less than or equal to 0.03 mm.

[0016] Preferably, the cross-section of the spiral air guide plate is rectangular.

[0017] Preferably, the gearbox is made of nickel-based high-temperature alloy.

[0018] The beneficial effects of the present invention are as follows: by providing a sealing device between the compressor and the gearbox, the leakage of the working fluid into the gearbox is reduced, the sealing effect is improved, and the loss of the working fluid is reduced; by connecting the sealing chamber with the exhaust compressor and delivering the working fluid to the working fluid system, the closed-loop circulation and reuse of the heat pump working fluid is realized, which greatly reduces the loss and replenishment demand of the working fluid, and effectively reduces the operating cost and maintenance expenses of the system; by connecting the inner cavity of the gearbox with the exhaust compressor, the inner cavity of the gearbox is maintained at a negative pressure, the temperature and pressure of the inner cavity of the gearbox are reduced, the problem of lubricating oil gasification is solved, and the gas flow resistance is reduced, the windage loss is reduced, the transmission efficiency of the gearbox is improved, and the overall operating efficiency and stability of the system are improved. By extracting the working fluid from the inner cavity of the gearbox, the loss of the working fluid is reduced, and the risk of the working fluid leaking into the environment is reduced, thereby improving the safety of use. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of the present invention;

[0020] Figure 2 is a schematic diagram of a labyrinth seal of the present invention;

[0021] Figure 3 Schematic diagram of the diffuser section and spiral air guide vane of the present invention;

[0022] Figure 4 is a schematic diagram of a sliding bearing of the present invention;

[0023] Figure 5 It is a schematic cross-sectional view of the sliding bearing of the present invention.

[0024] The reference numerals are recorded as follows: 1. first-stage compressor; 2. first-stage sealing device; 21. first-stage high-pressure sealing chamber; 22. first-stage low-pressure sealing chamber; 3. second-stage compressor; 4. second-stage sealing device; 41. second-stage low-pressure sealing chamber; 42. second-stage high-pressure sealing chamber; 5. labyrinth seal; 51. sealing teeth; 6. input shaft; 7. output shaft; 8. gear box; 9. exhaust compressor; 10. exhaust pipeline; 11. sliding bearing; 12. spiral air guide vane; 13. working fluid system; 14. mounting hole; 15. air guide hole; 16. bypass pipeline; 17. expansion section. DETAILED DESCRIPTION

[0025] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0026] like Figures 1 to 5As shown, the present invention discloses a multi-shaft multi-stage centrifugal compressor for a high-temperature heat pump, including an input shaft 6, an output shaft 7 and a gear box 8, the input shaft 6 and the output shaft 7 are mounted on the gear box 8, the input shaft 6 is connected to the output end of the motor, the input shaft 6 is connected to the output shaft 7 through a gear set, the transmission structure of the gear set adopts the existing technology, a primary compressor 1 is mounted on one end of the output shaft 7, a secondary compressor 3 is mounted on the other end of the output shaft 7, and an exhaust compressor 9 is also included, a primary sealing device 2 is provided at the connection between the primary compressor 1 and the gear box 8, a secondary sealing device 4 is provided at the connection between the secondary compressor 3 and the gear box 8, the primary sealing device 2 is connected to the secondary sealing device 4, the secondary sealing device 4 is connected to the exhaust compressor 9 through an exhaust pipeline 10, the exhaust compressor 9 is mounted on the input shaft 6, and the exhaust compressor 9 transports the working fluid to the working fluid system 13. When the input shaft 6 rotates, it drives the exhaust compressor 9 to work, and transports the working fluid leaked into the secondary sealing device 4 to the working fluid system 13, so as to realize the recycling of the working fluid and reduce the use cost. The impellers in the primary compressor 1 and the secondary compressor 3 rotate at high speed, sucking in low-temperature and low-pressure working fluid, and compressing it into high-temperature and high-pressure working fluid. Due to the contactless fit between the output shaft 7 and the gear box 8, driven by the pressure difference, the working fluid often leaks into the gear box 8 through the gap between the back of the impellers of the primary compressor 1 and the secondary compressor 3 and the gear box 8. By setting the primary sealing device 2 and the secondary sealing device 4, the leaking working fluid is blocked and decelerated, the flow of the working fluid is hindered, the leakage of the working fluid into the gear box 8 is effectively reduced, the working fluid loss is reduced, and the transmission efficiency of the gear set in the gear box 8 is ensured.

[0027] In this embodiment, the input shaft 6 is mounted on the gearbox 8 through a sliding bearing 11, and a plurality of air guide holes 15 are provided on the sliding bearing 11, and the inner cavity of the gearbox 8 is connected to the air extraction compressor 9 through the air guide holes 15. Specifically, the sliding bearing 11 is provided with a mounting hole 14 for the input shaft 6 to pass through, and a plurality of air guide holes 15 are arranged circumferentially along the mounting hole 14, so that the mixed gas in the inner cavity of the gearbox 8 is sucked to the air extraction compressor 9, so that the inner cavity of the gearbox 8 maintains a negative pressure, reduces the gas flow resistance, reduces the wind resistance loss, and improves the overall operation efficiency and stability of the system. During the continuous and efficient operation of the gearbox 8, in order to ensure the smoothness of the gear meshing and reduce wear, it is necessary to rely on the oil pump to accurately spray an appropriate amount of lubricating oil onto the gear contact surface to achieve effective lubrication and significantly reduce friction. However, the high-speed rotating gears will inevitably produce dense oil mist inside the gearbox 8, and the working fluid leaked into the gearbox 8 and the oil mist will mix together to cause the pressure and density of the mixed gas in the inner cavity of the gearbox 8 to increase significantly, thereby increasing the wind resistance loss, which has an adverse effect on the overall efficiency of the system. The inner cavity of the gear box 8 is connected to the exhaust compressor 9 through the air guide hole 15. When the input shaft 6 is working, it drives the exhaust compressor 9 to extract the mixed gas from the inner cavity of the gear box 8, and accurately extracts the working fluid leaking to the secondary low-pressure sealing cavity 41, and then transports it to the working fluid system 13. In this embodiment, the working fluid is transported to the condenser, realizing the closed-loop circulation and reuse of the heat pump working fluid, improving the working fluid utilization efficiency, and saving the working fluid cost.

[0028] Furthermore, the gearbox 8 is made of a nickel-based high-temperature alloy, specifically GH4169 nickel-based high-temperature alloy, which enables the gearbox 8 to have good high-pressure resistance and corrosion resistance, ensuring that it can still operate stably in a high-intensity and high-pressure working environment.

[0029] In this embodiment, a plurality of labyrinth seals 5 are provided in the primary sealing device 2 and the secondary sealing device 4, and a plurality of sealing teeth 51 are provided in the labyrinth seal 5, and the sealing teeth 51 play a role in blocking and reducing the pressure of the leaked working fluid, thereby reducing the leakage of the working fluid. Among them, three labyrinth seals 5 are respectively provided in the primary sealing device 2 and the secondary sealing device 4, forming a three-level labyrinth seal, which hinders the flow of the working fluid and improves the sealing effect. Specifically, the primary sealing device 2 includes a primary high-pressure sealing chamber 21 and a primary low-pressure sealing chamber 22, and the primary high-pressure sealing chamber 21 is close to the primary compressor 1, and the secondary sealing device 4 includes a secondary low-pressure sealing chamber 41 and a secondary high-pressure sealing chamber 42, and the secondary high-pressure sealing chamber 42 is close to the secondary compressor 3, and the secondary high-pressure sealing chamber 42 is connected to the primary low-pressure sealing chamber 22 through a bypass pipeline 16, and a throttle valve is provided on the bypass pipeline 16. Since the working fluid pressure at the secondary compressor 3 is higher, the pressure of the secondary high-pressure sealing chamber 42 is much higher than that of the primary low-pressure sealing chamber 22. When the secondary compressor 3 is working to compress the working fluid, a part of the high-pressure working fluid leaks into the secondary low-pressure sealing chamber 41 through the gap between the labyrinth seal 5 and the output shaft 7, and the other part of the high-pressure working fluid is reduced in pressure through the throttle valve on the bypass line 16, so that the working fluid pressure is close to the pressure in the primary low-pressure sealing chamber 22, and then enters the primary low-pressure sealing chamber 22. After the working fluid enters the primary low-pressure sealing chamber 22, an air seal is formed, which not only effectively curbs the leakage of the working fluid at the primary compressor 1 to the gear box 8, significantly improving the efficiency of the sealing system, but also prevents the high-pressure working fluid at the secondary compressor 3 from flowing back to the primary compressor 1, thereby ensuring the stability and efficiency of the compressor performance.

[0030] In this embodiment, a spiral air guide 12 is installed on the output shaft 7, and the spiral air guide 12 extends spirally along the output shaft 7. A spiral air guide 12 is provided between the secondary sealing device 4 and the gear box 8 and between the primary sealing device 2 and the gear box 8. The spiral air guide 12 forms a first lead and a second lead on the output shaft 7. The pitch of the first lead is greater than the pitch of the second lead, and the first lead is close to the gear box 8. For details, see Figure 3As shown, a diffuser section 17 is formed between the spiral air guide 12 and the primary sealing device 2 and between the spiral air guide 12 and the secondary sealing device 4, and the angle δ of the diffuser section 17 is 25°-30°. After being processed by the primary sealing device 2, the secondary sealing device 4 and the exhaust compressor 9, a trace amount of leaked working fluid may still remain. For this reason, a spiral air guide 12 is installed on the output shaft 7 between the final labyrinth seal 5 and the housing of the gear box 8. The spiral air guide 12 adopts a variable pitch, and the first lead of the inlet section of the spiral air guide 12 is designed as a large lead with a large pitch, which ensures a large suction volume in the initial stage and effectively improves the gas suction efficiency. As the spiral air guide 12 continues to rotate, the closed cavity formed gradually decreases. During this dynamic change process, the gas is gradually compressed to achieve an internal compression effect. This working mode of conveying and compressing not only significantly reduces the overall exhaust compression power consumption, but also effectively reduces the noise and vibration during exhaust, and improves the operating efficiency and environmental friendliness of the equipment. As the output shaft 7 rotates, the mixed gas in the inner cavity of the gear box 8 is spirally driven by the spiral air guide vane 12. When the gas flows through the diffuser section 17, the speed gradually decreases and the pressure slightly increases until it is the same as the pressure of the residual leaked working fluid, forming a tight isolation gas barrier to block the working fluid at the diffuser section 17 from leaking to the gear box 8, further improving the sealing effect and reducing working fluid leakage.

[0031] In this embodiment, specifically, the gap between the outer edge of the spiral air guide 12 and the inner wall of the gear box 8 is less than or equal to 0.03 mm. Since there may be residual leakage working fluid in the secondary sealing device 4 that is evacuated by the air extraction compressor 9, by providing the spiral air guide 12, when the output shaft 7 rotates continuously, the spiral air guide 12 guides the working fluid inside the gear box 8 to flow to the labyrinth seal 5, forming a tight and efficient air-sealing barrier, further reducing the leakage of residual working fluid in the primary sealing device 2 and the secondary sealing device 4 into the gear box 8, reducing working fluid loss, and further improving the sealing effect.

[0032] In this embodiment, specifically, the cross section of the spiral air guide piece 12 is rectangular, that is, the cross section of the spiral air guide piece 12 after being straightened is rectangular. The spiral air guide piece 12 has a good air guiding effect, realizes a more uniform gas distribution, reduces turbulence, is simple to manufacture, and reduces processing costs.

[0033] Since the labyrinth seal of the primary sealing device 2 is adopted between the first-stage compressor 1 and the gear box 8, the air seal formed in the primary sealing device 2 and the air seal formed by the spiral air guide vane 12 after the high-pressure working fluid is throttled in the secondary sealing device 4, the sealing effect between the first-stage compressor 1 and the gear box 8 is greatly improved through the above three-stage sealing.

[0034] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A multi-shaft multi-stage centrifugal compressor for a high-temperature heat pump, comprising an input shaft (6), an output shaft (7) and a gear box (8), wherein the input shaft (6) and the output shaft (7) are mounted on the gear box (8), the input shaft (6) is transmission-connected to the output shaft (7) via a gear set, a first-stage compressor (1) is mounted on one end of the output shaft (7), and a second-stage compressor (3) is mounted on the other end of the output shaft (7), characterized in that: It also comprises an air extraction compressor (9), wherein a primary sealing device (2) is provided at a connection between the primary compressor (1) and the gear box (8), a secondary sealing device (4) is provided at a connection between the secondary compressor (3) and the gear box (8), the primary sealing device (2) is in communication with the secondary sealing device (4), the secondary sealing device (4) is in communication with the air extraction compressor (9) via an air extraction pipeline (10), the input shaft (6) is mounted on the gear box (8) via a sliding bearing (11), a plurality of air guide holes (15) are provided on the sliding bearing (11), and an inner cavity of the gear box (8) is in communication with the air extraction compressor (9) via the air guide holes (15), The air extraction compressor (9) is mounted on the input shaft (6), and the air extraction compressor (9) transports the working medium to the working medium system (13); a spiral air guide plate (12) is mounted on the output shaft (7), and the spiral air guide plate (12) extends spirally along the output shaft (7). The spiral air guide plate (12) is respectively arranged at the connection between the secondary sealing device (4) and the gear box (8) and at the connection between the primary sealing device (2) and the gear box (8). The spiral air guide plate (12) forms a first lead and a second lead on the output shaft (7), and the pitch of the first lead is greater than the pitch of the second lead. The first lead is arranged close to the gear box (8).

2. The multi-shaft multi-stage centrifugal compressor for a high-temperature heat pump according to claim 1, characterized in that: A plurality of labyrinth seals (5) are provided in both the primary sealing device (2) and the secondary sealing device (4), and a plurality of sealing teeth (51) are provided in the labyrinth seals (5).

3. The multi-shaft multi-stage centrifugal compressor for a high-temperature heat pump according to claim 2, characterized in that: The primary sealing device (2) comprises a primary high-pressure sealing chamber (21) and a primary low-pressure sealing chamber (22); the secondary sealing device (4) comprises a secondary low-pressure sealing chamber (41) and a secondary high-pressure sealing chamber (42); the secondary high-pressure sealing chamber (42) is connected to the primary low-pressure sealing chamber (22) via a bypass pipeline (16); and a throttle valve is provided on the bypass pipeline (16).

4. The multi-shaft multi-stage centrifugal compressor for a high-temperature heat pump according to claim 1, characterized in that: A diffuser section (17) is formed between the spiral air guide sheet (12) and the primary sealing device (2), and between the spiral air guide sheet (12) and the secondary sealing device (4), and an angle δ of the diffuser section (17) is 25°-30°.

5. The multi-shaft multi-stage centrifugal compressor for a high-temperature heat pump according to claim 1, characterized in that: The gap between the outer edge of the spiral air guide plate (12) and the inner wall of the gear box (8) is less than or equal to 0.03 mm.

6. The multi-shaft multi-stage centrifugal compressor for a high-temperature heat pump according to claim 5, characterized in that: The cross section of the spiral air guide sheet (12) is rectangular.

7. The multi-shaft multi-stage centrifugal compressor for a high-temperature heat pump according to claim 1, characterized in that: The gear box (8) is made of a nickel-based high-temperature alloy.

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