A magnetic suspension rotor critical speed prediction model and optimization method

Abstract

This application discloses a critical speed prediction model and optimization method for a magnetic levitation rotor, relating to the field of magnetic levitation motor technology. The prediction model includes a spindle, impellers at both ends of the spindle shoulders, a permanent magnet sleeved on the outer periphery of the middle of the spindle, and annular portions on both sides of the permanent magnet on the outer periphery of the spindle. Axially, the annular portions are spaced apart from the spindle, and adjacent components within the annular portions are also spaced apart. The permanent magnets are spaced apart from the spindle, and the impellers are in contact with the shoulders. Radially, the annular portions are in contact with the spindle, and the permanent magnets are spaced apart from the spindle. This application solves the problem of accurately assessing the critical speed of a magnetic levitation rotor by using through-holes to optimize and improve the critical speed while keeping the model's outer boundaries unchanged. Simultaneously, by reducing the rotor's weight and adjusting the weight-removing position of the through-holes, the distance between the rotor's center of mass and the geometric center of the magnetic bearing is reduced, improving the rotor's operational stability.

Description

Technical Field

[0001] This application relates to the field of magnetic levitation motor technology, and in particular to a critical speed prediction model and optimization method for magnetic levitation rotors. Background Technology

[0002] The demands of social development are leading to increasingly higher energy consumption. Improving equipment efficiency and reducing losses have become key paths to green development. Magnetic levitation equipment uses electromagnetic bearings for support, eliminating energy consumption caused by mechanical bearing friction, and plays a vital role in this green development path.

[0003] However, the operating speed of magnetic levitation rotors is usually as high as tens of thousands of revolutions per minute. When the speed approaches the critical speed, the levitation effect will deteriorate. If it approaches even further, the magnetic bearing will be unable to control the violent vibration of the rotor, causing the rotor to fall. This requires the rotor to have a high critical speed.

[0004] During the research and development of magnetic levitation products, the critical speed of the magnetic levitation rotor needs to be accurately predicted during the design phase. However, it is inevitable that the rotor will sometimes fail to reach the critical speed design point. In addition, due to the difference in weight between the first-stage and second-stage impellers, the rotor's mass distribution is larger on the heavier end of the impeller, which affects its operational stability.

[0005] Therefore, in view of the above-mentioned technical problems, how to accurately assess the critical speed of the magnetic levitation rotor and improve the critical speed is a technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0006] The purpose of this application is to provide a critical speed prediction model and optimization method for magnetic levitation rotors, which solves the problem of the difficulty in accurately assessing the critical speed of magnetic levitation rotors, and can also optimize and improve the critical speed, thereby enhancing the operating stability of the rotor.

[0007] To achieve the above objectives, this application provides a critical speed prediction model for a magnetic levitation rotor, including a spindle, impellers at both ends of the spindle, a permanent magnet sleeved on the outer periphery of the middle part of the spindle, and annular portions sleeved on the outer periphery of the spindle on both sides of the permanent magnet.

[0008] Along the axial direction of the mandrel, the annular portion is spaced apart from the mandrel, and adjacent components within the annular portion are spaced apart. The permanent magnet is spaced apart from the mandrel, and the impeller is bonded to the shaft shoulder.

[0009] In the radial direction of the mandrel, the annular portion is bonded to and in contact with the mandrel, and the permanent magnet is spaced apart from the mandrel.

[0010] Preferably, the mandrel has bolts and nuts that mate with the bolts at both ends, the impeller is pressed against the shaft shoulder by the bolts and the nuts, and the impeller is coaxially arranged with the mandrel.

[0011] Preferably, the annular portion includes a first magnetic isolation ring, a position sensor, a second magnetic isolation ring, a first limiting ring, a radial magnetic bearing, and a second limiting ring arranged sequentially along the axial direction of the mandrel. The first magnetic isolation ring is located near the shoulder of the mandrel, and the second limiting ring is located near the shoulder of the mandrel.

[0012] Preferably, along the axial direction of the mandrel, the opposite surfaces of the first magnetic isolation ring and the position sensor, the opposite surfaces of the position sensor and the second magnetic isolation ring, the opposite surfaces of the second magnetic isolation ring and the first limiting ring, the opposite surfaces of the first limiting ring and the radial magnetic bearing, the opposite surfaces of the radial magnetic bearing and the second limiting ring, and the opposite surfaces of the second limiting ring and the shoulder are all spaced apart.

[0013] In the radial direction of the mandrel, the inner rings of the first magnetic isolation ring, the position sensor, the second magnetic isolation ring, the first limiting ring, the radial magnetic bearing, and the second limiting ring are all interference-fitted with the mandrel to achieve a binding contact.

[0014] Preferably, the permanent magnet is disposed between the two shoulders, and a third magnetic isolation ring is provided between the end of the permanent magnet and the shoulder. In the axial direction of the mandrel, the opposing surfaces of the permanent magnet and the third magnetic isolation ring, and the opposing surfaces of the third magnetic isolation ring and the shoulder are all spaced apart.

[0015] The third magnetic isolation ring is spaced apart from the mandrel in the radial direction of the mandrel.

[0016] Preferably, a protective sleeve is provided around the permanent magnet and the third magnetic isolation ring, and the protective sleeve covers at least the permanent magnet and the third magnetic isolation ring in the axial direction. In the axial direction of the mandrel, the protective sleeve is spaced apart from the shoulder.

[0017] In the radial direction of the mandrel, the sheath is interference-fitted with the permanent magnet and the third magnetic isolation ring to achieve a binding contact.

[0018] A method for optimizing the critical speed of a magnetically levitated rotor, based on the aforementioned critical speed prediction model for a magnetically levitated rotor, includes:

[0019] S1. A first through hole coaxially is opened along the axis of the spindle. The diameter of the first through hole is d1. The optimal value of d1 is obtained with the highest critical speed as the target.

[0020] S2. Perform modal analysis on the model obtained in S1 to obtain its mode shape, and open a second through hole with a diameter of d2 at the stagnation point of the mode shape. The first through hole and the second through hole overlap or partially overlap.

[0021] S3. In the axial direction of the mandrel, the distance from one end of the second through hole to the stagnation point is L1, and the distance from the other end of the second through hole to the stagnation point is L2. Based on the highest critical speed mentioned in S1, the parameters of L1, L2, and d2 are adjusted to further increase the critical speed.

[0022] Preferably, in S3, each parameter L1, L2, and d2 is taken in N groups, and N... 3 The solution is solved once, and the result is used to fit a function to obtain the optimal values ​​of L1, L2, and d2 with the highest critical speed as the target.

[0023] Compared with the prior art, the technical solution provided in this application has at least the following beneficial effects:

[0024] This application utilizes the contact relationships of various components in the finite element model of magnetic levitation rotor dynamics. Specifically, the finite element model considers the thermal expansion and contraction caused by the interference fit of materials, correctly defines the model boundary conditions and the contact relationships between various parts, and ensures that the model has accurate calculation precision, with the error between simulation and experiment guaranteed to be within 5%. Simultaneously, by using through-holes, the critical speed is increased while keeping the model's external boundaries unchanged. By reducing the rotor's weight and adjusting the weight-reducing position of the through-holes, the distance between the magnetic levitation rotor's center of mass and the geometric center of the magnetic bearing is reduced, thereby improving operational stability. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the magnetic levitation rotor structure in the magnetic levitation rotor critical speed prediction model provided in the embodiments of this application.

[0027] Figure 2 This is a schematic diagram of the first through-hole structure in the magnetic levitation rotor critical speed optimization method provided in the embodiments of this application;

[0028] Figure 3 This is a schematic diagram of the second through hole and the vibration mode in the magnetic levitation rotor critical speed optimization method provided in the embodiments of this application.

[0029] In the picture:

[0030] 1-Mandrel; 2-Bolt; 3-Nut; 4-Impeller; 5-First magnetic isolation ring; 6-Position sensor; 7-Second magnetic isolation ring; 8-First limiting ring; 9-Radial magnetic bearing; 10-Second limiting ring; 11-Shoulder; 12-Shoulder; 13-Third magnetic isolation ring; 14-Permanent magnet; 15-Sheath; 16-First through hole; 17-Second through hole. Detailed Implementation

[0031] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0032] It should be noted that in this embodiment, the orientation or positional relationship indicated by terms such as "upper," "lower," "front," and "rear" is based on the orientation or positional relationship shown in the accompanying drawings. It is used only for the convenience of describing this application and for simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this application. Furthermore, "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0033] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] Please refer to Figure 1 In this embodiment, a critical speed prediction model for a magnetic levitation rotor is provided. This model is based on the structure of the magnetic levitation rotor, thereby determining the boundary conditions of the model and the contact relationship between the parts in the model.

[0035] Specifically, the model includes a mandrel 1, with impellers 4 located at both ends of the mandrel 1 at shoulders 11. A permanent magnet 14 is fitted around the outer periphery of the middle part of the mandrel 1, and annular portions are fitted around the outer periphery of the mandrel 1 on both sides of the permanent magnet 14. The boundary conditions for determining the model include:

[0036] A ring-shaped portion is spaced apart from the spindle 1 along the axial direction of the spindle 1. Adjacent parts within the ring-shaped portion are spaced apart. The permanent magnet 14 is spaced apart from the spindle 1. The impeller 4 is bonded to the shaft shoulder 11.

[0037] In the radial direction of the mandrel 1, the annular portion is bonded to the mandrel 1, and the permanent magnet 14 is spaced apart from the mandrel 1.

[0038] In this context, "bonded contact" means that the contact areas of two objects are considered to be completely connected, and no relative sliding or separation between surfaces or lines is allowed.

[0039] Furthermore, the mandrel 1 has bolts 2 and nuts 3 that mate with the bolts 2 at both ends. The bolts 2 are connected to the mandrel 1 by threads, and the impeller 4 is pressed against the shaft shoulder 11 by the bolts 2 and nuts 3. Please refer to [reference needed] for details. Figure 1 This method secures the impeller 4 and the spindle 1 coaxially. It should be noted that when considering the material of the impeller 4, only the stiffness property can be retained, ignoring the material density property. By defining the center of mass position, the weight of the center of mass, and the moments of inertia of the three rotation axes passing through the center of mass, this method does not require redefining the contact between models when optimizing the weight of the impeller 4, thus improving simulation efficiency.

[0040] In some embodiments, the annular portion includes a first magnetic shielding ring 5, a position sensor 6, a second magnetic shielding ring 7, a first limiting ring 8, a radial magnetic bearing 9, and a second limiting ring 10 arranged sequentially along the axial direction of the mandrel 1. Please refer to... Figure 1 The first magnetic shielding ring 5 is located near the shoulder 11, and the second limiting ring 10 is located near the shoulder 12 of the spindle 1. It should be noted that the annular part includes, but is not limited to, the components given above. Other components may be added or removed according to actual needs. The specific components included in the annular part and their functions can be found in the prior art, and will not be elaborated here.

[0041] When determining the model boundary at the corresponding position of the annular part, the first magnetic isolation ring 5 and the position sensor 6 are spaced apart on the axial direction of the mandrel 1, the position sensor 6 and the second magnetic isolation ring 7 are spaced apart on the opposite surface, the second magnetic isolation ring 7 and the first limiting ring 8 are spaced apart on the opposite surface, the first limiting ring 8 and the radial magnetic bearing 9 are spaced apart on the opposite surface, the radial magnetic bearing 9 and the second limiting ring 10 are spaced apart on the opposite surface, and the second limiting ring 10 and the shoulder 12 are spaced apart on the opposite surface.

[0042] In the radial direction of the mandrel 1, the inner rings of the first magnetic isolation ring 5, the position sensor 6, the second magnetic isolation ring 7, the first limiting ring 8, the radial magnetic bearing 9, and the second limiting ring 10 are all interference-fitted with the mandrel 1 to achieve binding contact between the annular part and the mandrel 1.

[0043] The permanent magnet 14 is disposed between the two shoulders 12, and a third magnetic isolation ring 13 is provided between the end of the permanent magnet 14 and the shoulder 12. When determining the model boundary at the corresponding position of the permanent magnet 14, the opposing surfaces of the permanent magnet 14 and the third magnetic isolation ring 13 are spaced apart in the axial direction of the mandrel 1, and the opposing surfaces of the third magnetic isolation ring 13 and the shoulder 12 are spaced apart; in the radial direction of the mandrel 1, the third magnetic isolation ring 13 is spaced apart from the mandrel 1.

[0044] In addition, a sheath 15 is provided around the permanent magnet 14 and the third magnetic isolation ring 13. The sheath 15 covers at least the permanent magnet 14 and the third magnetic isolation ring 13 in the axial direction. When determining the model boundary at the corresponding position of the sheath 15, the sheath 15 is spaced apart from the shoulder 12 in the axial direction of the mandrel 1. In the radial direction of the mandrel 1, the sheath 15 is press-fitted with the permanent magnet 14 and the third magnetic isolation ring 13 to achieve a binding contact.

[0045] It should be noted that the aforementioned interval setting refers to the absence of contact between the two objects, ensuring that the state of one object does not affect the other. Based on the above embodiment, the components such as the first magnetic isolation ring 5, position sensor 6, second magnetic isolation ring 7, first limiting ring 8, radial magnetic bearing 9, second limiting ring 10, spindle 1, third magnetic isolation ring 13, permanent magnet 14, and sheath 15 are not placed in contact at other locations. The stiffness of the radial magnetic bearing 9 is equivalently replaced by linear stiffness, establishing linear stiffness in the x, y, -x, and -y directions respectively; the axial magnetic bearing establishes linear stiffness in the z-axis direction, with a magnitude of static stiffness.

[0046] It can be seen that the finite element model in this application considers the thermal expansion and contraction caused by the interference fit of materials, correctly defines the boundary conditions of the model and the contact relationship between each part, as well as the contact state between the permanent magnet 14 and the mandrel 1 at high speed. According to experimental verification, the model has accurate calculation accuracy, and the error between simulation and experiment can be guaranteed to be within 5%. In addition, the optimization of impeller 4 does not require model reconstruction, saving model building time and improving simulation efficiency.

[0047] This application also provides a method for optimizing the critical speed of a magnetic levitation rotor. This method is based on the above-mentioned critical speed prediction model for a magnetic levitation rotor. The model improves the critical speed and operational stability of the rotor by optimizing the diameter and position of the de-weighting hole.

[0048] The method specifically includes:

[0049] S1. The mandrel 1 has a coaxial first through hole 16 along its axis. Please refer to... Figure 2 The diameter of the first through hole 16 is d1. Using this as an optimization parameter, the optimal value of d1 is obtained with the highest critical speed as the target.

[0050] S2. Perform modal analysis on the model obtained in S1 to obtain its mode shapes. Please refer to [reference needed]. Figure 3 A second through hole 17 with a diameter of d2 is opened at the stagnation point of the mode shape, and the first through hole 16 overlaps or partially overlaps with the second through hole 17.

[0051] S3. In the axial direction of the mandrel 1, the distance from one end of the second through hole 17 to the stagnation point is L1, and the distance from the other end of the second through hole 17 to the stagnation point is L2. Based on the highest critical speed in S1, adjust the parameters of L1, L2, and d2 to further increase the critical speed.

[0052] This method enables the magnetically levitated rotor to seek the highest critical speed by setting a first through hole 16; by setting a second through hole 17, the mass near the stagnation point is further reduced, and the critical speed is further increased based on the first through hole 16.

[0053] Because the rotor design typically involves the first-stage impeller 4 being heavier than the second-stage impeller 4, the load on the two radial magnetic bearings 9 differs significantly during operation, leading to system instability. To address this issue, this invention optimizes the sizes of L1 and L2, reducing the distance between the centroid of the magnetic levitation rotor and the geometric center of the magnetic bearings, thereby improving operational stability.

[0054] Optimizing the mass near the stagnation point is determined by the dimensions L1, L2, and d2. This can be achieved by taking N sets of each parameter L1, L2, and d2, and performing N... 3 Solve the problem 5 times, for example, taking five sets for each parameter and performing 5... 3 The solution is solved once, and the result is used to fit a function to obtain the optimal values ​​of L1, L2, and d2 with the highest critical speed as the target.

[0055] As can be seen, this method, through the optimization of weight reduction via drilling, achieves an increase in the critical speed while keeping the external boundary conditions unchanged. Taking a magnetic levitation rotor with a diameter of 132mm and a speed of 28,000rpm as an example, this method can increase the critical speed by about 1,000rpm, helping the rotor reach the design point. Simultaneously, by reducing the rotor's weight and adjusting the position of the weight reduction hole in the middle, the distance between the rotor's center of mass and the geometric center of the magnetic bearing is reduced, thereby improving operational stability.

[0056] It should be noted that in this specification, relational terms such as first and second are used only to distinguish one entity from several other entities, and do not necessarily require or imply any such actual relationship or order between these entities.

[0057] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this application. It should be noted that those skilled in the art can make several improvements and modifications to this application without departing from the principles of this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. A critical speed prediction model for a magnetically levitated rotor, wherein the model is a finite element model, characterized in that, Includes a mandrel (1), with impellers (4) provided at the shoulders (11) at both ends of the mandrel (1), a permanent magnet (14) sleeved on the outer periphery of the middle part of the mandrel (1), and annular portions sleeved on the outer periphery of the mandrel (1) on both sides of the permanent magnet (14); Along the axial direction of the mandrel (1), the annular portion is spaced apart from the mandrel (1), and adjacent components within the annular portion are spaced apart. The permanent magnet (14) is spaced apart from the mandrel (1), and the impeller (4) is bonded to the shoulder (11). In the radial direction of the mandrel (1), the annular portion is bonded to the mandrel (1), and the permanent magnet (14) is spaced apart from the mandrel (1); The permanent magnet (14) is disposed between the two shoulders (12) of the mandrel (1), and a third magnetic isolation ring (13) is provided between the end of the permanent magnet (14) and the shoulder (12). Along the axial direction of the mandrel (1), the opposite surfaces of the permanent magnet (14) and the third magnetic isolation ring (13) and the opposite surfaces of the third magnetic isolation ring (13) and the shoulder (12) are all spaced apart. The third magnetic isolation ring (13) is arranged at a distance from the mandrel (1) in the radial direction of the mandrel (1); The permanent magnet (14) and the third magnetic isolation ring (13) are covered with a protective sleeve (15), and the protective sleeve (15) covers at least the permanent magnet (14) and the third magnetic isolation ring (13) in the axial direction. In the axial direction of the mandrel (1), the protective sleeve (15) is spaced apart from the shoulder (12). In the radial direction of the mandrel (1), the sheath (15) is interference-fitted with the permanent magnet (14) and the third magnetic isolation ring (13) to achieve a binding contact.

2. The critical speed prediction model for a magnetically levitated rotor according to claim 1, characterized in that, The mandrel (1) has bolts (2) and nuts (3) that cooperate with the bolts (2) at both ends. The impeller (4) is pressed against the shoulder (11) by the bolts (2) and the nuts (3). The impeller (4) is coaxial with the mandrel (1).

3. The critical speed prediction model for a magnetically levitated rotor according to claim 1, characterized in that, The annular portion includes a first magnetic isolation ring (5), a position sensor (6), a second magnetic isolation ring (7), a first limiting ring (8), a radial magnetic bearing (9), and a second limiting ring (10) arranged sequentially along the axial direction of the mandrel (1). The first magnetic isolation ring (5) is located near the shoulder (11), and the second limiting ring (10) is located near the shoulder (12) of the mandrel (1).

4. The critical speed prediction model for a magnetically levitated rotor according to claim 3, characterized in that, Along the axial direction of the mandrel (1), the opposite surfaces of the first magnetic isolation ring (5) and the position sensor (6), the opposite surfaces of the position sensor (6) and the second magnetic isolation ring (7), the opposite surfaces of the second magnetic isolation ring (7) and the first limiting ring (8), the opposite surfaces of the first limiting ring (8) and the radial magnetic bearing (9), the opposite surfaces of the radial magnetic bearing (9) and the second limiting ring (10), and the opposite surfaces of the second limiting ring (10) and the shoulder (12) are all spaced apart; In the radial direction of the mandrel (1), the inner rings of the first magnetic isolation ring (5), the position sensor (6), the second magnetic isolation ring (7), the first limiting ring (8), the radial magnetic bearing (9), and the second limiting ring (10) are all interference-fitted with the mandrel (1) to achieve binding contact.

5. A method for optimizing the critical speed of a magnetically levitated rotor, characterized in that, The method based on the critical speed prediction model of the magnetic levitation rotor according to any one of claims 1-4 includes: S1. The spindle (1) has a coaxial first through hole (16) along its axis. The diameter of the first through hole (16) is d1. The optimal value of d1 is obtained with the highest critical speed as the target. S2. Perform modal analysis on the model obtained in S1 to obtain its mode shape, and open a second through hole (17) with a diameter of d2 at the stagnation point of the mode shape. The first through hole (16) overlaps or partially overlaps with the second through hole (17). S3. In the axial direction of the mandrel (1), the distance from one end of the second through hole (17) to the stagnation point is L1, and the distance from the other end of the second through hole (17) to the stagnation point is L2. Based on the highest critical speed mentioned in S1, the parameters of L1, L2, and d2 are adjusted to further increase the critical speed.

6. The method for optimizing the critical speed of a magnetically levitated rotor according to claim 5, characterized in that, In S3, each parameter L1, L2, and d2 is taken in N groups, and N operations are performed. 3 The solution is solved once, and the result is used to fit a function to obtain the optimal values ​​of L1, L2, and d2 with the highest critical speed as the target.

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