A centrifugal compressor main shaft, water injection cooling system and control method

Abstract

The present invention discloses a centrifugal compressor main shaft, a water injection cooling system, and a control method. The centrifugal compressor main shaft includes: an impeller side, a sealing side, and a gear shaft; the impeller side includes an impeller and a left shaft body, the left shaft body connecting the impeller and the gear shaft; the sealing side includes a first sealing assembly and a right shaft body, the right shaft body connecting the gear shaft and provided with a first sealing assembly; a first cooling water channel is provided in the impeller side, a first drainage channel is provided in the left shaft body, the first cooling water channel passes through the impeller and the left shaft body, and cooling water is discharged from the first drainage channel after passing through the first cooling water channel; a second cooling water channel is provided in the sealing side, a second drainage channel is provided in the right shaft body, the second cooling water channel passes through the first sealing assembly and the right shaft body, and cooling water is discharged from the second drainage channel after passing through the second cooling water channel. The present invention can achieve efficient cooling of the thrust balancing disk and maintain the stability of the sealing gap during the operation of the compressor.

Description

Technical Field

[0001] The present invention belongs to the technical field of centrifugal compressors, and in particular relates to a centrifugal compressor main shaft, a water injection cooling system and a control method. Background Art

[0002] In the design of supercritical carbon dioxide (SCO2) centrifugal compressors, supercritical carbon dioxide, as a fluid with unique physical properties, typically operates under high pressure and temperature conditions. The sealing system plays a crucial role in this equipment, its primary purpose being to prevent gas leakage from the compressor into the external environment, ensuring operational safety and efficiency.

[0003] However, in actual use, thrust balance disc seals often face the problem of insufficient sealing clearance, which can lead to wear and even damage to the equipment. The root cause is that the thrust balance disc seal is affected by thermal expansion. Under the high-temperature, high-pressure operating environment of a centrifugal compressor, the sealing material expands due to the rising temperature, causing the sealing gap between it and the main shaft to gradually decrease. This expansion effect increases the friction between the thrust balance disc seal and the main shaft, which can cause wear and leakage in the sealing area, and even lead to compressor failure. Furthermore, the problem of impeller overheating during long-term operation of the compressor also needs to be addressed urgently.

[0004] In order to solve the above problems, existing technologies generally select materials with a smaller thermal expansion coefficient to manufacture thrust balance discs, and adopt a multi-stage sealing structure to reduce the expansion problem caused by temperature changes, share the axial force between the thrust balance disc and the main shaft, and delay wear. For example, invention patent application CN112253491A discloses a multi-stage centrifugal supercritical carbon dioxide compressor, which includes a casing, a main shaft, an inter-shaft balancing disk, a low-pressure stage impeller, a high-pressure stage impeller and a shaft end balancing disk. The main shaft is rotatably arranged in the casing, and the main shaft has a high-pressure end and a low-pressure end along the axial direction; the inter-shaft balancing disk, the inter-shaft balancing disk is sleeved on the main shaft, the low-pressure stage impeller is sleeved on the main shaft, and is located on the side of the inter-shaft balancing disk facing the low-pressure end, the low-pressure stage impeller includes a first-stage impeller and a second-stage impeller distributed along the axial direction of the main shaft, the high-pressure stage impeller is sleeved on the main shaft, and is located on the side of the inter-shaft balancing disk facing the high-pressure end, the second-stage impeller includes a third-stage impeller and a fourth-stage impeller distributed along the axial direction of the main shaft, and the shaft end balancing disk is sleeved on the main shaft and is located at the air inlet of the fourth-stage impeller. However, this approach is not only limited by material constraints, but also by the multi-stage sealing structure, which still cannot effectively prevent seal damage caused by temperature rise. The complex structure also increases manufacturing costs and maintenance difficulties. Furthermore, the cooling system of existing supercritical CO2 centrifugal compressors has poor dynamic response and often fails to respond immediately during compressor startup and shutdown. This results in large temperature differences during initial startup, affecting sealing performance.

[0005] Therefore, how to achieve efficient cooling during the operation of the compressor and reduce the impact of overheating and thermal expansion on the sealing gap is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0006] In response to the above-mentioned deficiencies in the prior art, the present invention provides a centrifugal compressor main shaft, a water injection cooling system, and a control method, which can achieve efficient cooling of the thrust balance disc and maintain the stability of the sealing gap during compressor operation.

[0007] In a first aspect, the present invention provides a centrifugal compressor main shaft, specifically comprising: an impeller side, a sealing side, and a gear shaft; the impeller side comprises an impeller and a left shaft body, the left end of the left shaft body being connected to the impeller, and the right end of the left shaft body being connected to the gear shaft; the sealing side comprises a first sealing assembly and a right shaft body, the left end of the right shaft body being connected to the gear shaft, and the right end of the right shaft body being provided with a first sealing assembly;

[0008] A first cooling water channel is provided inside the impeller side, and a first drainage channel is provided on the right edge of the left shaft body. The first cooling water channel runs through the impeller and the left shaft body, and the cooling water is discharged from the first drainage channel after passing through the first cooling water channel.

[0009] A second cooling water channel is set inside the sealing side, and a second drainage channel is set on the left edge of the right shaft body. The second cooling water channel runs through the first sealing assembly and the right shaft body. The cooling water is discharged from the second drainage channel after passing through the second cooling water channel.

[0010] Furthermore, the first cooling water channel includes a first water inlet channel and a first cooling channel. The first water inlet channel passes through the impeller and is connected to the first cooling channel provided in the left shaft. The first cooling channel is connected to the first drainage channel.

[0011] The second cooling water channel includes a second water inlet channel and a second cooling channel. The second water inlet channel passes through the first sealing assembly and is connected to the second cooling channel provided in the right shaft body. The second cooling channel is connected to the second drainage channel.

[0012] The inner diameter of the first cooling channel is not smaller than the inner diameter of the second cooling channel.

[0013] Furthermore, the inner diameter ratio of the first cooling channel to the second cooling channel is 1.2-2.

[0014] Furthermore, the first water inlet channel includes a spiral water channel and a first water injection channel. The first water injection channel is cylindrical and passes through the impeller. The spiral water channel is wound around the outside of the first water injection channel and is arranged in the left shaft body.

[0015] The cooling water enters and passes through the first water injection channel and the spiral water channel respectively, and flows to the first cooling flow channel.

[0016] Furthermore, the spiral water channel includes at least two variable pitch spiral water channels, each variable pitch spiral water channel is a multi-spiral ring structure, including an inlet ring, a support ring and an outlet ring connected in sequence, and the cooling water enters the variable pitch spiral water channel from the water inlet of the inlet ring, passes through the support ring, and flows from the water outlet of the outlet ring to the first cooling channel;

[0017] The water inlets of the variable pitch spiral water channels are distributed at equal angles in the cross section of the first water inlet channel, and the support rings of the variable pitch spiral water channels are arranged in a cross-shaped and equal-spaced pattern.

[0018] Along the cooling water flow direction, the pitch of the spiral ring in each variable pitch spiral water channel increases proportionally;

[0019] In adjacent spiral rings, the pitch ratio between the rear spiral ring and the front spiral ring is 1.1-1.5.

[0020] Furthermore, the second water inlet channel includes a tooth-shaped water channel and a second water injection channel, the second water injection channel penetrates the first sealing component from the center position of the first sealing component, and the tooth-shaped water channel penetrates the first sealing component through the edge portion of the first sealing component;

[0021] The tooth-shaped water channel and the second water injection water channel form an annular second water inlet channel. Cooling water enters and passes through the second water injection water channel and the tooth-shaped water channel and flows to the second cooling channel.

[0022] Furthermore, the tooth-shaped water channel includes a water inlet section, a tooth-shaped cooling section and a water outlet section which are connected in sequence, and the tooth-shaped cooling section is arranged inside the edge portion of the first sealing assembly;

[0023] The inner wall of the toothed cooling section is provided with a plurality of racks, and the spacing between adjacent racks is consistent.

[0024] In a second aspect, the present invention provides a centrifugal compressor main shaft water injection cooling system, comprising: the centrifugal compressor main shaft, a first electric valve, a second electric valve, a first circulating water pump, a second circulating water pump, a circulating cooling water tank, and a monitoring unit;

[0025] The circulating cooling water tank, the first circulating water pump, the first electric valve and the impeller side form a first cooling loop. The cooling water flows from the circulating cooling water tank through the first circulating water pump, the first electric valve and the first cooling water channel and then returns to the circulating cooling water tank.

[0026] The circulating cooling water tank, the second circulating water pump, the second electric valve and the sealing side form a second cooling loop. The cooling water flows from the circulating cooling water tank through the second circulating water pump, the second electric valve and the second cooling water channel and then returns to the circulating cooling water tank.

[0027] The monitoring unit is connected to the first electric valve and the second electric valve signals, and is used to monitor and adjust the cooling water volume flow of the first cooling loop and the second cooling loop.

[0028] Furthermore, the monitoring unit is also used to monitor the water inlet temperature of the first cooling water channel, the water outlet temperature of the first drainage channel, the compressor inlet gas temperature, and the compressor outlet gas temperature;

[0029] Adjust the cooling water volume flow of the first cooling loop, including:

[0030] Determine the optimal heat generation power and cooling water heat absorption power on the impeller side based on the water inlet temperature of the first cooling water channel, the water outlet temperature of the first drainage channel, the compressor inlet gas temperature, and the optimal compressor outlet gas temperature;

[0031] Determine the optimal cooling water volume flow rate of the first cooling loop based on the optimal heat production power and cooling water heat absorption power on the impeller side;

[0032] According to the real-time temperature of the compressor outlet gas and the optimal temperature of the compressor outlet gas, combined with the optimal cooling water volume flow of the first cooling loop and the impeller side cooling water mass flow when the first electric valve is opened to the maximum, the current opening of the first electric valve is determined and the first electric valve is controlled.

[0033] Furthermore, the optimal cooling water volume flow rate of the first cooling loop satisfies the following relationship:

[0034]

[0035] in, is the compressor gas mass flow rate, is the specific heat capacity of gas at constant pressure, is the optimal temperature of the compressor outlet gas, is the compressor inlet gas temperature, is the specific heat capacity of cooling water at constant pressure, is the outlet water temperature of the first drainage channel, is the inlet water temperature of the first cooling water channel, is the optimal cooling water volume flow rate of the first cooling loop, is the cooling water density.

[0036] Furthermore, the current opening of the first electric valve is determined based on the real-time temperature of the compressor outlet gas and the optimal temperature of the compressor outlet gas, in combination with the optimal cooling water volume flow of the first cooling loop and the impeller-side cooling water mass flow when the first electric valve is opened to the maximum, including:

[0037] determining an optimal opening of the first electric valve according to an optimal cooling water volume flow of the first cooling loop;

[0038] Determine the temperature change of the compressor outlet gas according to the current compressor outlet gas temperature and the optimal compressor outlet gas temperature;

[0039] The current opening of the first electric valve is determined according to the temperature change of the compressor outlet gas and the optimal opening of the first electric valve.

[0040] The optimal opening of the first electric valve satisfies the following relationship:

[0041]

[0042] in, is the opening of the first electric valve, is the impeller side cooling water mass flow rate when the first electric valve is opened to the maximum, Compressor gas mass flow rate, is the specific heat capacity of gas at constant pressure, is the specific heat capacity of gas at constant pressure, is the optimal temperature of the compressor outlet gas, is the compressor inlet gas temperature, is the specific heat capacity of cooling water at constant pressure, is the outlet water temperature of the first drainage channel, is the inlet water temperature of the first cooling water channel.

[0043] The current opening of the first electric valve satisfies the following relationship:

[0044]

[0045] in, is the current opening of the first electric valve, is the current temperature of the gas at the compressor outlet, The upper limit of the compressor outlet gas temperature.

[0046] Furthermore, the monitoring unit is also used to monitor the outlet water temperature of the second drainage channel and the inlet water temperature of the second cooling water channel.

[0047] Adjust the cooling water volume flow rate of the second cooling loop, specifically including:

[0048] Conduct force analysis on the impeller side to determine the friction heat power on the seal side;

[0049] Determine the heat power to be absorbed based on the outlet water temperature of the first drainage channel and the inlet water temperature of the second cooling water channel, combined with the friction heat power on the sealing side;

[0050] Determine the cooling water mass flow rate of the second cooling loop based on the optimal expansion gap of the thrust balancing disk and the heat power to be absorbed;

[0051] According to the cooling water mass flow rate of the second cooling loop and the cooling water mass flow rate of the second electric valve when the second electric valve is at its maximum opening, the opening degree of the second electric valve is given and the second electric valve is controlled.

[0052] Furthermore, the cooling water mass flow rate of the second cooling loop satisfies the following relationship:

[0053]

[0054] Where m2 is the cooling water mass flow rate of the second cooling loop, α is the thermal expansion coefficient of the sealing material of the thrust balance disc, and F n is the radial positive pressure of the thrust balance disc generating friction, D is the diameter of the thrust balance disc, n is the speed of the thrust balance disc, T3 is the inlet water temperature of the second cooling water channel, δ max is the maximum allowable expansion gap of the sealing material of the thrust balancing disc, δ0 is the initial design gap of the sealing material of the thrust balancing disc, T4 is the maximum outlet water temperature of the second drainage channel corresponding to the maximum allowable expansion gap, and B is the multiple of the optimal expansion gap of the sealing material of the thrust balancing disc, B<1.

[0055] Furthermore, the opening of the second electric valve satisfies the following relationship:

[0056]

[0057] Where K2 is the opening of the second electric valve, A is the effective pressure bearing area of the impeller, p1 and p2 are the compressor outlet pressure and compressor inlet pressure respectively, m 2,max It is the cooling water mass flow rate of the second cooling loop when the second electric valve is opened to the maximum, that is, the maximum cooling water mass flow rate of the second cooling loop.

[0058] In a third aspect, the present invention further provides a centrifugal compressor main shaft water injection cooling control method, which uses the above-mentioned water injection cooling system and specifically includes the following steps:

[0059] The valve opening of the first electric valve is set, and the first circulating water pump is turned on. The cooling water flows from the circulating cooling water tank through the first circulating water pump, the first electric valve and the first cooling water channel to cool the impeller side of the centrifugal compressor main shaft, and then returns to the circulating cooling water tank. The monitoring unit monitors and controls the opening of the second electric valve to adjust the cooling water volume flow rate;

[0060] Set the valve opening of the second electric valve, turn on the second circulating water pump, and the cooling water flows from the circulating cooling water tank through the second circulating water pump, the second electric valve and the second cooling water channel to cool the sealing side of the centrifugal compressor main shaft, and then returns to the circulating cooling water tank. The monitoring unit monitors and controls the opening of the second electric valve and adjusts the cooling water volume flow rate.

[0061] The present invention provides a centrifugal compressor main shaft, water injection cooling system and control method, which have at least the following beneficial effects:

[0062] (1) Independent cooling water channels are set up on the impeller side and the seal side of the main shaft to cool the impeller side and the seal side respectively, realizing the integrated design of zoned precise temperature control water injection cooling and sealing structure. The water injection cooling and the sealing structure are combined so that the thrust balance disc can be continuously and stably cooled during operation, avoiding the problem of unstable sealing gap caused by thermal expansion.

[0063] (2) The impeller side adopts a variable pitch spiral water channel to enhance the heat transfer efficiency through turbulence; the carbon ring seal side adopts an equidistant tooth channel water channel to effectively increase the heat transfer area.

[0064] (3) The cooling water flow rate is automatically adjusted based on the temperature changes and load conditions within the compressor, controlling the temperature of the impeller and thrust balance plate, maintaining a stable gap between the thrust balance plate seal and the main shaft, and avoiding friction damage caused by an excessively small seal gap. Compared to traditional external cooling systems and fixed-flow systems, the spindle water injection cooling and control strategy of the present invention is more targeted and efficient, enabling rapid and precise temperature regulation under different operating conditions and preventing seal failure. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 A schematic structural diagram of a centrifugal compressor main shaft provided by the present invention;

[0066] Figure 2 A schematic structural diagram of a spiral water channel according to an embodiment of the present invention;

[0067] Figure 3 A schematic cross-sectional view of a first drainage channel according to an embodiment of the present invention;

[0068] Figure 4 A schematic cross-sectional view of a second drainage channel of an embodiment provided by the present invention;

[0069] Figure 5 A schematic diagram of a centrifugal compressor main shaft water injection cooling system provided by the present invention;

[0070] Figure 6 This is a flow chart of a centrifugal compressor main shaft water injection cooling control method provided by the present invention.

[0071] Explanation of the reference numerals: 1-impeller side, 11-impeller, 12-left shaft, 13-first drainage channel, 14-first water inlet channel, 15-first cooling channel, 16-spiral water channel, 161-inlet ring, 162-support ring, 163-outlet ring, 17-first water injection channel, 2-sealing side, 201-first outlet, 202-second outlet, 21-first seal, 22-right shaft, 23-second drainage channel, 24-second water inlet Flow channel, 25-second cooling flow channel, 26-toothed water channel, 27-second water injection flow channel, 2-sealing side, 3-gear shaft, 411-first annular shell, 412-second annular shell, 421-first tube body, 422-second tube body, 100-centrifugal compressor main shaft, 200-first electric valve, 300-second electric valve, 400-first circulating water pump, 500-second circulating water pump, 600-circulating cooling water tank, 700-control unit. DETAILED DESCRIPTION

[0072] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0073] The terms used in the embodiments of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The singular forms "a," "an," "the," and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, and unless the context clearly indicates otherwise, "a plurality" generally includes at least two.

[0074] It should also be noted that the terms "include," "comprises," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a product or device comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such product or device. In the absence of further limitations, an element defined by the phrase "comprises a..." does not exclude the presence of other identical elements in the product or device comprising the element.

[0075] like Figure 1As shown, the present invention provides a centrifugal compressor main shaft, which may specifically include: an impeller side 1, a sealing side 2, and a gear shaft 3; the impeller side 1 includes an impeller 11 and a left shaft body 12, the left end of the left shaft body 12 is connected to the impeller 11, and the right end of the left shaft body 12 is connected to the gear shaft 3; the sealing side 2 includes a first sealing assembly 21 and a right shaft body 22, the left end of the right shaft body 22 is connected to the gear shaft 3, and the right end of the right shaft body 22 is provided with a first sealing assembly 21;

[0076] A first cooling water channel is provided in the impeller side 1, and a first drainage channel 13 is provided on the right edge of the left shaft 12. The first cooling water channel runs through the impeller 11 and the left shaft 12, and the cooling water is discharged from the first drainage channel 13 after passing through the first cooling water channel.

[0077] A second cooling water channel is provided within the sealing side 2, and a second drainage channel 23 is provided on the left edge of the right shaft 22. The second cooling water channel runs through the first sealing assembly 21 and the right shaft 22. Cooling water flows through the second cooling water channel and is discharged through the second drainage channel 23. Preferably, the first and second cooling water channels are coaxially arranged to ensure high structural stability and reduce energy loss during spindle operation. The first sealing assembly includes a thrust balancing disc.

[0078] The cooling water channel is set inside the main shaft, which has a compact design, saves space, reduces the overall weight of the compressor, and reduces the complexity and cost of the cooling system; by cooling with water from the inside, the water flow directly acts on the sealing area and impeller of the thrust balance disk, effectively reducing the temperature of the sealing area and the impeller, and avoiding problems such as thermal expansion caused by temperature increase; by setting independent first cooling water channels inside the impeller side and the sealing side respectively, the impeller side cooling and the sealing side cooling can be carried out separately, realizing zoned temperature control and improving the utilization rate of energy and water resources; the second cooling water channel is set in the sealing side, combining water injection cooling with the sealing structure, so that the thrust balance disk can be continuously and stably cooled during operation, avoiding the problem of unstable sealing gap caused by thermal expansion.

[0079] like Figure 1As shown, the first cooling water channel includes a first water inlet channel 14 and a first cooling channel 15. The first water inlet channel 14 runs through the impeller 11 and communicates with the first cooling channel 15 set in the left shaft body. The first cooling channel 15 is connected to the first drainage channel 13. Through the connection between the first water inlet channel and the first cooling channel, cooling water can be circulated from the inside of the impeller side for cooling, thereby improving the cooling effect on the impeller side. The second cooling water channel includes a second water inlet channel 24 and a second cooling channel 25. The second water inlet channel 24 runs through the first sealing assembly 21 and communicates with the second cooling channel 25 set in the right shaft body. The second cooling channel 25 is connected to the second drainage channel 23. Through the connection between the second water inlet channel and the second cooling channel, cooling water can be circulated from the inside of the sealing side for cooling, thereby improving the cooling effect on the sealing side.

[0080] In a supercritical carbon dioxide centrifugal compressor, the main shaft size on the impeller side is relatively large, mainly to meet its mechanical strength and stability requirements under high-pressure and high-density working conditions. The high-density characteristics of supercritical carbon dioxide cause the impeller to bear greater centrifugal and axial forces during operation. The larger main shaft size can provide higher bending and torsional strength, reduce deformation and fatigue damage, and thus improve the reliability of the equipment. Based on this, the embodiment of the present invention can relatively increase the heat exchange area and improve the heat exchange efficiency of the impeller side by setting the inner diameter of the first cooling channel to be not less than the inner diameter of the second cooling channel, effectively reduce the temperature of the impeller side, reduce the impact of thermal expansion on the impeller side, avoid deformation and stress concentration caused by high temperature, thereby improving the mechanical strength and stability of the impeller side and extending the service life.

[0081] Preferably, the inner diameter ratio of the first cooling channel 15 to the second cooling channel 25 is 1.2-2.

[0082] like Figures 1 and 2 As shown, the first water inlet channel 14 is arranged at the part of the left shaft body that passes through the impeller, that is, the first water inlet channel 14 is arranged in the end portion where the left shaft body and the impeller are fixed. The first water inlet channel 14 includes a spiral water channel 16 and a first water injection channel 17. The first water injection channel is cylindrical and passes through the impeller. The spiral water channel 16 is wound around the outside of the first water injection channel 17 and is arranged in the left shaft body. The cooling water enters and passes through the first water injection channel 17 and the spiral water channel 16 respectively and flows to the first cooling channel 15. By setting up the spiral water channel, the path of cooling water can be improved, the heat exchange area can be increased, and thus the cooling effect of the impeller can be improved; the first water injection water channel can exchange heat with the cooling water in the spiral water channel to improve the heat exchange effect of the spiral water channel, and can also directly cool the impeller, thereby realizing multi-stage coordinated cooling of the impeller (the spiral water channel cools the impeller at the first stage, the first water injection water channel cools the impeller at the second stage, and the first water injection water channel cools the impeller at the third stage, indirectly realizing the cooling of the impeller on the basis of the cooling of the impeller), ensuring that the temperature on the impeller side is within the safe operating range.

[0083] In actual application scenarios, the spiral water channel may include at least two variable pitch spiral water channels, each variable pitch spiral water channel is a multi-spiral ring structure, including an inlet ring 161, a support ring 162 and an outlet ring 163 connected in sequence, and the cooling water enters the variable pitch spiral water channel from the water inlet of the inlet ring, passes through the support ring, and flows to the first cooling channel from the water outlet of the outlet ring; the water inlets of each variable pitch spiral water channel are distributed at equal angles in the cross section of the first inlet water channel, and the support rings of each variable pitch spiral water channel are arranged crosswise and at equal intervals.

[0084] By providing multiple variable-pitch spiral water channels, the heat exchange efficiency can be improved without increasing the size of the variable-pitch spiral water channels, thereby enhancing the cooling effect of the variable-pitch spiral water channels on the impeller. Furthermore, the design of equal-angle distribution ensures optimal spacing between the variable-pitch spiral water channels, enabling each variable-pitch spiral water channel to achieve a good cooling effect. The pitch of the spiral rings in each variable-pitch spiral water channel increases proportionally along the direction of cooling water flow, thereby achieving a variable pitch effect. Furthermore, the increase in pitch along the direction of cooling water flow satisfies the structural characteristics of the impeller, which is narrow in front and wide in the back, matching the gradient change in its heat-generating area, thereby better cooling the impeller.

[0085] The pitch ratio between the rear and front spiral rings of adjacent spiral rings is 1.1-1.5. The smaller-pitch spiral rings near the left end of the impeller are more closely spaced, providing a larger heat exchange area and enabling rapid heat exchange with the impeller during the initial cooling water injection phase. As the cooling water flows, the pitch between the spiral rings increases, and the spacing becomes increasingly sparse, facilitating the rapid outflow of cooling water after heat exchange into the primary cooling channel, improving heat exchange efficiency and rapidly cooling the impeller.

[0086] like Figure 1 As shown, the second water inlet channel includes a toothed channel 26 and a second water injection channel 27. The second water injection channel 27 extends from the center of the first sealing assembly 21 through the first sealing assembly, and then passes through the edge of the first sealing assembly. The toothed channel 26 and the second water injection channel 27 form an annular second water inlet channel. Cooling water enters and passes through the second water injection channel 27 and the toothed channel 26, respectively, and flows to the second cooling channel 25. The provision of the toothed channel can cool the outer edge of the thrust balance disk. The structure of the toothed channel can also further increase the heat exchange area of the cooling water, thereby improving the cooling effect on the sealing structure. The second water injection channel can cool the toothed channel while also cooling the thrust balance disk, thereby improving the cooling effect on the first sealing assembly and preventing thermal expansion problems in the sealing structure.

[0087] Among them, the toothed water channel may include a water inlet section, a toothed cooling section and a water outlet section connected in sequence, and the toothed cooling section is arranged inside the edge of the first sealing component; the inner wall of the toothed cooling section is provided with a plurality of racks, and the spacing between adjacent racks is consistent.

[0088] In this way, the cooling water flow rate through the rack can be guaranteed to be the same, avoiding the situation where some cooling surfaces fail to achieve heat exchange due to stall. The design of the rack cooling section can effectively increase the heat exchange area and ensure a better cooling effect at the thrust balance plate; wherein, the racks on the same inner wall in the toothed cooling section can be separate or continuous. The separate type means that the rack is arranged in a ring shape on the inner wall, and the continuous type means that the rack is arranged in a spiral ring shape on the inner wall. In actual application scenarios, the rack includes a dorsal side and an oblique side. The dorsal side is perpendicular to the inner wall, and the oblique side is inclined from the inner wall toward the flow direction of the cooling water, thereby achieving the effect of diversion and increasing the cooling path. In addition, a plurality of water inlet cooling water channels and water outlet cooling water channels can be provided in the water inlet section and the water outlet section respectively. The toothed cooling section is an annular cavity and is connected to the water inlet cooling water channel and the water outlet cooling water channel.

[0089] like Figure 3 As shown, in this embodiment, the first drainage channel 13 of the left shaft body discharges cooling water through the first drainage pipe. Specifically, the first drainage pipe includes a first annular shell 411 and a first tube body 421 connected to the first annular shell 411. The first annular shell 411 is sleeved on the left shaft body, and the first outlet 201 of the first cooling channel 15 is located inside the first annular shell 411. The structure of the first drainage pipe cooperating with the left shaft body can enable the cooling water in the first cooling channel 15 to enter the first annular shell 411 through the first outlet 201 when the main shaft of the centrifugal compressor rotates, and finally realize the function of discharging cooling water through the first drainage channel 13 connected to the inside of the first annular shell 411. As shown Figure 4 As shown, the second drainage channel 23 of the right shaft body discharges cooling water through a second drainage pipe. Specifically, the second drainage pipe includes a second annular housing 412 and a second pipe body 422 connected to the second annular housing 412. The second annular housing 412 is sleeved on the right shaft body, and the second outlet 202 of the second cooling channel 25 is located within the second annular housing 412. The structure of the second drainage pipe and the right shaft body allows the cooling water in the second cooling channel 25 to enter the second annular housing 412 through the second outlet 202 when the centrifugal compressor main shaft rotates, and ultimately discharge the cooling water through the second drainage channel 23 connected to the interior of the second annular housing 412.

[0090] Furthermore, multiple first drainage channels and multiple second drainage channels can be set, and multiple first drainage channels and multiple second drainage channels are respectively arranged perpendicular to the axes of the left shaft body and the right shaft body, and multiple first drainage channels and multiple second drainage channels are respectively arranged at equal intervals along the circumference of the left shaft body and the right shaft body, which can ensure that the first drainage channel and the second drainage channel have good drainage effects, and at the same time avoid the centrifugal force of the drainage channel when discharging cooling water to affect the overall rotation of the main shaft.

[0091] The traditional cooling method of centrifugal compressors often requires complex external cooling channels and equipment. The main shaft water injection cooling of this embodiment achieves cooling through the cooling channels inside the main shaft. Compared with the traditional cooling system, the main shaft water injection cooling of this embodiment can adjust the temperature of the sealing area more quickly. The sealing area refers to the area where the compressor casing forms a seal with the main shaft. Furthermore, this embodiment can, on the basis of cooling the main shaft, better heat exchange and cooling the areas where the impeller and thrust balance plate are located where the temperature is more concentrated, to ensure that the seal always remains in an ideal working state when the compressor starts and stops or the load changes, avoiding sealing failure problems caused by excessive temperature difference or instantaneous load changes.

[0092] In high-temperature, high-pressure environments, the stability of sealing performance is crucial. The spindle water injection cooling solution effectively avoids the negative impact of excessive temperatures on sealing performance through real-time cooling, maintaining higher sealing reliability, especially during long-term high-load operation.

[0093] In addition, the centrifugal compressor main shaft of the present invention is not only suitable for SCO2 centrifugal compressors, but can also be extended to other rotating mechanical equipment in high-temperature and high-pressure environments, such as gas turbines, steam compressors, etc., and has strong adaptability and broad application prospects.

[0094] The operating principle of the centrifugal compressor main shaft of the present invention is:

[0095] During long-term operation, centrifugal compressors generate heat due to factors such as gas compression, component friction, and motor heating, which can cause problems such as impeller overheating and seal expansion.

[0096] After the main shaft of the centrifugal compressor of the present invention is in operation, water can be injected into the cooling water channel on the impeller side. Specifically, cooling water is injected into the first water injection channel and the spiral water channel inside the left shaft body respectively; the spiral water channel has a large heat exchange area, and the cooling water therein fully exchanges heat with the impeller, taking away the heat generated by the rotation of the impeller; at the same time, the cooling water in the first water injection channel exchanges heat with the heated cooling water in the spiral water channel, further improving the cooling effect of the impeller. The cooling water in the first water injection channel and the spiral water channel merges into the first cooling channel, and after exchanging heat with the left shaft body, it is discharged through the first drainage channel, thereby achieving cooling of the impeller side and preventing the impeller from overheating.

[0097] Independent of the impeller-side cooling water channel, the seal-side cooling water channel can also be filled with cooling water. Specifically, water is injected into the second water injection channel and the tooth-shaped water channel inside the right shaft body. The tooth-shaped water channel is an annular cavity set according to the thrust balance disk, with a large heat exchange area. The cooling water therein fully exchanges heat with the first sealing component, cooling the thrust balance disk; the cooling water in the second water injection channel cools the right shaft body. The cooling water in the second water injection channel and the tooth-shaped water channel merge in the second cooling channel, further exchange heat with the right shaft body, and is discharged through the second drainage channel, achieving cooling on the seal side and ensuring the stability of the sealing gap.

[0098] like Figure 5 As shown, the present invention provides a centrifugal compressor main shaft water injection cooling system, which may include: the above-mentioned centrifugal compressor main shaft 100, a first electric valve 200, a second electric valve 300, a first circulating water pump 400, a second circulating water pump 500, a circulating cooling water tank 600 and a monitoring unit 700;

[0099] The circulating cooling water tank, the first circulating water pump, the first electric valve and the impeller side form a first cooling loop. The cooling water flows from the circulating cooling water tank through the first circulating water pump, the first electric valve and the first cooling water channel and then returns to the circulating cooling water tank.

[0100] The circulating cooling water tank, the second circulating water pump, the second electric valve and the sealing side form a second cooling loop. The cooling water flows from the circulating cooling water tank through the second circulating water pump, the second electric valve and the second cooling water channel and then returns to the circulating cooling water tank.

[0101] The monitoring unit is connected to the first electric valve and the second electric valve signals, and is used to monitor and adjust the cooling water volume flow of the first cooling loop and the second cooling loop.

[0102] The monitoring unit is also used to monitor the water inlet temperature of the first cooling water channel, the water outlet temperature of the first drainage channel, the compressor inlet gas temperature, and the compressor outlet gas temperature;

[0103] Adjust the cooling water volume flow of the first cooling loop, including:

[0104] S1: Determine the optimal heat generation power and cooling water heat absorption power on the impeller side based on the water inlet temperature of the first cooling water channel, the water outlet temperature of the first drainage channel, the compressor inlet gas temperature, and the optimal compressor outlet gas temperature;

[0105] S2: Determine the optimal cooling water volume flow rate of the first cooling loop based on the optimal heat production power and cooling water heat absorption power on the impeller side;

[0106] S3: Based on the real-time temperature of the compressor outlet gas and the optimal temperature of the compressor outlet gas, combined with the optimal cooling water volume flow of the first cooling loop and the impeller side cooling water mass flow when the first electric valve is opened to the maximum, the current opening of the first electric valve is determined and the first electric valve is controlled.

[0107] In a certain embodiment, the cooling water volume flow rate of the first cooling loop is adjusted based on the analysis of the inlet water temperature of the first cooling water channel, the outlet water temperature of the first drainage channel, the compressor inlet gas temperature, and the compressor outlet gas temperature, and the valve opening of the first electric valve is controlled.

[0108] In S1, the optimal heat generation power of the impeller is determined to satisfy the following relationship:

[0109]

[0110] in, is the impeller heat generation power, is the compressor gas mass flow rate, is the specific heat capacity of gas at constant pressure, is the optimal temperature of the compressor outlet gas, is the compressor inlet gas temperature;

[0111] Determine the heat absorption power of the cooling water on the impeller side to meet the following relationship:

[0112]

[0113] in, is the cooling water heat absorption power, m1 is the cooling water mass flow rate on the compressor impeller side, is the specific heat capacity of cooling water at constant pressure, is the outlet water temperature of the first drainage channel, is the water inlet temperature of the first cooling water channel;

[0114] In S2, when determining the optimal cooling water volume flow rate of the first cooling loop, the cooling water must satisfy the following conditions when dissipating heat to the impeller side: , determine the optimal lower limit of the impeller side cooling water mass flow rate, and obtain the optimal cooling water volume flow rate on the corresponding impeller side, that is, the optimal cooling water volume flow rate of the first cooling loop, which satisfies the following relationship:

[0115]

[0116] Among them, m1 is the mass flow rate of cooling water on the compressor impeller side, is the compressor gas mass flow rate, is the specific heat capacity of gas at constant pressure, is the compressor outlet gas temperature, is the compressor inlet gas temperature, is the specific heat capacity of cooling water at constant pressure, is the outlet water temperature of the first drainage channel, is the inlet water temperature of the first cooling water channel, is the optimal cooling water volume flow rate of the first cooling loop, is the cooling water density;

[0117] In S3, the current opening of the first electric valve is determined based on the real-time temperature of the compressor outlet gas and the optimal temperature of the compressor outlet gas, in combination with the optimal cooling water volume flow of the first cooling loop and the impeller-side cooling water mass flow when the first electric valve is opened to the maximum, including:

[0118] determining an optimal opening of the first electric valve according to an optimal cooling water volume flow of the first cooling loop;

[0119] Determine the temperature change of the compressor outlet gas according to the current compressor outlet gas temperature and the optimal compressor outlet gas temperature;

[0120] The current opening of the first electric valve is determined according to the temperature change of the compressor outlet gas and the optimal opening of the first electric valve.

[0121] The optimal opening of the first electric valve satisfies the following relationship:

[0122]

[0123] Where, is the opening of the first electric valve, is the impeller side cooling water mass flow rate when the first electric valve is opened to the maximum, is the compressor gas mass flow rate, is the specific heat capacity of gas at constant pressure, is the optimal temperature of the compressor outlet gas, is the compressor inlet gas temperature, is the specific heat capacity of cooling water at constant pressure, is the outlet water temperature of the first drainage channel, is the inlet water temperature of the first cooling water channel.

[0124] The current opening of the first electric valve satisfies the following relationship:

[0125]

[0126] in, is the current opening of the first electric valve, is the current temperature of the gas at the compressor outlet, The upper limit of the compressor outlet gas temperature.

[0127] In addition, the monitoring unit is further configured to monitor the outlet water temperature of the second drainage channel and the inlet water temperature of the second cooling water channel, and to control the valve opening of the second electric valve based on the analysis of the outlet water temperature of the second drainage channel and the inlet water temperature of the second cooling water channel, specifically including:

[0128] Conduct force analysis on the impeller side to determine the friction heat power on the seal side;

[0129] Determine the heat power to be absorbed based on the outlet water temperature of the first drainage channel and the inlet water temperature of the second cooling water channel, combined with the friction heat power on the sealing side;

[0130] Determine the cooling water mass flow rate of the second cooling loop based on the optimal expansion gap of the thrust balancing disk and the heat power to be absorbed;

[0131] According to the cooling water mass flow rate of the second cooling loop and the cooling water mass flow rate of the second electric valve when the second electric valve is at its maximum opening, the opening degree of the second electric valve is given and the second electric valve is controlled.

[0132] Among them, the friction heat power P on the sealing side fri It can be determined by the radial positive pressure corresponding to the pressure difference before and after the impeller and the speed of the thrust balance disc, satisfying the following relationship:

[0133]

[0134] Where μ is the friction coefficient of the sealing material corresponding to the thrust balance disc, F n is the radial positive pressure that generates friction force for the thrust balance disc, D is the diameter of the thrust balance disc, and n is the rotational speed of the thrust balance disc.

[0135] The heat power transferred from the impeller side to the seal side can be determined based on the outlet water temperature of the first drainage channel and the inlet water temperature of the second cooling water channel. Combined with the friction heat power on the seal side, the heat power to be absorbed can be obtained, which satisfies the following relationship:

[0136]

[0137] Where Q total is the heat power to be absorbed, T3 is the inlet water temperature of the second cooling water channel;

[0138] After determining the heat power to be absorbed, the cooling water mass flow rate of the second cooling loop can be obtained by combining the optimal expansion gap of the thrust balancing disk to satisfy the following relationship:

[0139]

[0140] Where m2 is the cooling water mass flow rate of the second cooling loop, α is the thermal expansion coefficient of the sealing material of the thrust balance disc, and δ maxis the maximum allowable expansion gap of the sealing material of the thrust balancing disc, δ0 is the initial design gap of the sealing material of the thrust balancing disc, T4 is the maximum outlet water temperature of the second drainage channel corresponding to the maximum allowable expansion gap, B is the multiple of the optimal expansion gap of the sealing material of the thrust balancing disc, B<1, is the cooling water volume flow rate of the second cooling loop, is the cooling water density.

[0141] Determining the opening of the second electric valve includes: obtaining the maximum opening of the second electric valve (the maximum opening of the second electric valve K 2,max =100%), the cooling water mass flow rate of the second cooling loop and the determined cooling water volume flow rate of the second cooling loop give the opening of the second electric valve, which satisfies the following relationship:

[0142]

[0143] Where K2 is the opening of the second electric valve, m 2,max is the cooling water mass flow rate of the second cooling loop when the second electric valve is at its maximum opening, i.e., the maximum cooling water mass flow rate of the second cooling loop. The adjustment of the valve opening can be used to adjust the cooling water mass flow rate or the cooling water volume flow rate. In addition, in this embodiment, the thrust balancing disc is a symmetrical structure, the gas pressure of the compressor is evenly distributed, and the thrust balancing disc is in a state of dynamic equilibrium. When calculating the frictional heat power on the sealing side, the radial positive pressure corresponding to the friction force is equal to the axial thrust generated by the gas acting on the impeller, i.e. , at this time, the opening of the second electric valve can satisfy the following relationship:

[0144]

[0145] Where A is the effective pressure-bearing area of the impeller, that is, the projected area of the impeller in the axial direction, p1 and p2 are the compressor outlet pressure and the compressor inlet pressure, respectively.

[0146] Of course, the valve opening of the second electric valve can also be controlled by the following methods:

[0147] Monitor the cooling water outlet temperature of the second drainage channel ;

[0148] Establish through experiments or simulations and seal expansion gap the relationship between;

[0149] when When the temperature increases, the valve opening of the second electric valve can be increased according to the PID control algorithm to increase the cooling water volume flow of the second cooling loop to avoid overheating;

[0150] when When decreasing, the valve opening of the second electric valve can be reduced according to the PID control algorithm to reduce the cooling water volume flow of the second cooling loop.

[0151] The centrifugal compressor spindle water injection cooling system automatically adjusts the cooling water volume flow rate injected into the primary and secondary cooling water channels based on internal compressor temperature and load conditions. This precisely controls the temperature of the impeller and primary seal assembly, preventing impeller overheating and ensuring seal gap stability. Compared to traditional fixed-flow cooling systems, this intelligent control system can more efficiently adapt to varying operating conditions, improving system adaptability and accuracy.

[0152] like Figure 6 As shown, the present invention also provides a centrifugal compressor main shaft water injection cooling control method, which adopts the above-mentioned water injection cooling system and specifically includes the following steps:

[0153] The valve opening of the first electric valve is set, and the first circulating water pump is turned on. Cooling water flows from the circulating cooling water tank through the first circulating water pump, the first electric valve, and the first cooling water channel to cool the impeller side of the centrifugal compressor main shaft, and then returns to the circulating cooling water tank. The monitoring unit monitors and controls the opening of the first electric valve and adjusts the cooling water volume flow rate;

[0154] Set the valve opening of the second electric valve, turn on the second circulating water pump, and the cooling water flows from the circulating cooling water tank through the second circulating water pump, the second electric valve and the second cooling water channel to cool the sealing side of the centrifugal compressor main shaft, and then returns to the circulating cooling water tank. The monitoring unit monitors and controls the opening of the second electric valve and adjusts the cooling water volume flow rate.

[0155] Although preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic inventive concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the invention. Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the invention. Thus, the present invention is intended to include such changes and modifications as fall within the scope of the claims and their equivalents.

Claims

1. A centrifugal compressor main shaft, characterized in that: Specifically including: impeller side, sealing side and gear shaft; the impeller side includes an impeller and a left shaft body, the left end of the left shaft body is connected to the impeller, and the right end of the left shaft body is connected to the gear shaft; the sealing side includes a first sealing assembly and a right shaft body, the left end of the right shaft body is connected to the gear shaft, and the right end of the right shaft body is provided with a first sealing assembly; A first cooling water channel is provided inside the impeller side, and a first drainage channel is provided on the right edge of the left shaft body. The first cooling water channel runs through the impeller and the left shaft body, and the cooling water is discharged from the first drainage channel after passing through the first cooling water channel. A second cooling water channel is provided inside the sealing side, and a second drainage channel is provided on the left edge of the right shaft body. The second cooling water channel runs through the first sealing assembly and the right shaft body. The cooling water passes through the second cooling water channel and is discharged from the second drainage channel. The first cooling water channel includes a first water inlet channel and a first cooling channel. The first water inlet channel runs through the impeller and is connected to the first cooling channel provided in the left shaft. The first cooling channel is connected to the first drainage channel. The first water inlet channel includes a spiral water channel and a first water injection channel. The first water injection channel is cylindrical and passes through the impeller. The spiral water channel is wound around the outside of the first water injection channel and is arranged in the left shaft body. The cooling water enters and passes through the first water injection channel and the spiral water channel respectively, and flows to the first cooling channel; The spiral water channel includes at least two variable pitch spiral water channels, each variable pitch spiral water channel is a multi-spiral ring structure, including an inlet ring, a support ring and an outlet ring connected in sequence, and cooling water enters the variable pitch spiral water channel from the water inlet of the inlet ring, passes through the support ring, and flows to the first cooling channel from the water outlet of the outlet ring; The water inlets of the variable pitch spiral water channels are distributed at equal angles in the cross section of the first water inlet channel, and the support rings of the variable pitch spiral water channels are arranged in a cross-shaped and equal-spaced pattern. Along the cooling water flow direction, the pitch of the spiral ring in each variable pitch spiral water channel increases proportionally; In adjacent spiral rings, the pitch ratio between the rear spiral ring and the front spiral ring is 1.1-1.

5.

2. The centrifugal compressor main shaft according to claim 1, characterized in that: The second cooling water channel includes a second water inlet channel and a second cooling channel. The second water inlet channel passes through the first sealing assembly and is connected to the second cooling channel provided in the right shaft body. The second cooling channel is connected to the second drainage channel. The inner diameter of the first cooling channel is not smaller than the inner diameter of the second cooling channel.

3. The centrifugal compressor main shaft according to claim 2, characterized in that: The inner diameter ratio of the first cooling channel to the second cooling channel is 1.2-2.

4. The centrifugal compressor main shaft according to claim 2, characterized in that: The second water inlet channel includes a tooth-shaped water channel and a second water injection channel, the second water injection channel penetrates the first sealing component from the center position of the first sealing component, and the tooth-shaped water channel penetrates the first sealing component through the edge of the first sealing component; The tooth-shaped water channel is arranged around the second water injection channel, and the cooling water enters and passes through the second water injection channel and the tooth-shaped water channel respectively, and flows into the second cooling channel.

5. The centrifugal compressor main shaft according to claim 4, characterized in that: The tooth-shaped water channel includes a water inlet section, a tooth-shaped cooling section and a water outlet section which are connected in sequence, and the tooth-shaped cooling section is arranged inside the edge portion of the first sealing component; The inner wall of the toothed cooling section is provided with a plurality of racks, and the spacing between adjacent racks is consistent.

6. A centrifugal compressor main shaft water injection cooling system, characterized in that: include: The centrifugal compressor main shaft, the first electric valve, the second electric valve, the first circulating water pump, the second circulating water pump, the circulating cooling water tank and the monitoring unit according to any one of claims 1 to 5; The circulating cooling water tank, the first circulating water pump, the first electric valve and the impeller side form a first cooling loop. The cooling water flows from the circulating cooling water tank through the first circulating water pump, the first electric valve and the first cooling water channel and then returns to the circulating cooling water tank. The circulating cooling water tank, the second circulating water pump, the second electric valve and the sealing side form a second cooling loop. The cooling water flows from the circulating cooling water tank through the second circulating water pump, the second electric valve and the second cooling water channel and then returns to the circulating cooling water tank. The monitoring unit is connected to the first electric valve and the second electric valve signals, and is used to monitor and adjust the cooling water volume flow of the first cooling loop and the second cooling loop.

7. The centrifugal compressor main shaft water injection cooling system according to claim 6, characterized in that: The monitoring unit is also used to monitor the water inlet temperature of the first cooling water channel, the water outlet temperature of the first drainage channel, the compressor inlet gas temperature, and the compressor outlet gas temperature; Adjust the cooling water volume flow of the first cooling loop, including: Determine the optimal heat generation power and cooling water heat absorption power on the impeller side based on the water inlet temperature of the first cooling water channel, the water outlet temperature of the first drainage channel, the compressor inlet gas temperature, and the optimal compressor outlet gas temperature; Determine the optimal cooling water volume flow rate of the first cooling loop based on the optimal heat production power and cooling water heat absorption power on the impeller side; According to the real-time temperature of the compressor outlet gas and the optimal temperature of the compressor outlet gas, combined with the optimal cooling water volume flow of the first cooling loop and the impeller side cooling water mass flow when the first electric valve is opened to the maximum, the current opening of the first electric valve is determined and the first electric valve is controlled.

8. A centrifugal compressor main shaft water injection cooling control method, characterized in that: The water injection cooling system according to claim 6 or 7 specifically comprises the following steps: The valve opening of the first electric valve is set, and the first circulating water pump is turned on. Cooling water flows from the circulating cooling water tank through the first circulating water pump, the first electric valve, and the first cooling water channel to cool the impeller side of the centrifugal compressor main shaft, and then returns to the circulating cooling water tank. The monitoring unit monitors and controls the valve opening of the first electric valve and adjusts the cooling water volume flow rate; Set the valve opening of the second electric valve, start the second circulating water pump, and the cooling water flows from the circulating cooling water tank through the second circulating water pump, the second electric valve and the second cooling water channel to cool the sealing side of the centrifugal compressor main shaft, and then returns to the circulating cooling water tank. The monitoring unit monitors and controls the valve opening of the second electric valve and adjusts the cooling water volume flow rate.

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