Magnetic suspension rotor critical rotation speed prediction model and optimization method

Abstract

The invention discloses a magnetic suspension rotor critical rotation speed prediction model and an optimization method, and relates to the technical field of magnetic suspension motors, the prediction model comprises a core shaft, impellers are arranged at shaft shoulders at two ends of the core shaft, a permanent magnet sleeves the periphery of the middle part of the core shaft, and an annular part sleeves the periphery of the core shaft at two sides of the permanent magnet; in the axial direction of the mandrel, the annular part and the mandrel are arranged at intervals, adjacent components in the annular part are arranged at intervals, the permanent magnet and the mandrel are arranged at intervals, and the impeller is in binding contact with the shaft shoulder; in the radial direction of the mandrel, the annular part is in binding contact with the mandrel, and the permanent magnets and the mandrel are arranged at intervals. The problem that the critical rotating speed of the magnetic suspension rotor is difficult to accurately evaluate is solved, the critical rotating speed is optimized and improved under the condition that the external boundary of the model is not changed in a through hole forming mode, and meanwhile the weight of the rotor is reduced, the weight removing position of the through hole is adjusted, and the reliability of the magnetic suspension rotor is improved. The distance between the mass center of the magnetic suspension rotor and the geometric center of the magnetic bearing is reduced, and the operation stability of the rotor is improved.

Description

Technical Field

[0001] The present application relates to the technical field of magnetic levitation motors, and in particular to a critical speed prediction model and optimization method for magnetic levitation rotors. Background Art

[0002] The need for social development has increased energy consumption, and improving equipment efficiency and reducing losses have become one of the paths to green development. Magnetic levitation equipment uses electromagnetic bearing support, without the energy consumption caused by mechanical bearing friction, and plays an important role in the path of green development.

[0003] However, the operating speed of the magnetic levitation rotor is usually as high as tens of thousands of revolutions. When the speed approaches the critical speed, the suspension effect will deteriorate. When it approaches further, the magnetic bearing will not be able to control the violent vibration of the rotor, causing the rotor to fall. This requires the rotor to have a higher critical speed.

[0004] In the process of developing magnetic levitation products, the critical speed of the magnetic levitation rotor needs to be accurately predicted during design, but it is inevitable that the rotor cannot reach the critical speed design point. In addition, due to the inconsistent weight of the first-stage impeller and the second-stage impeller, the mass distribution of the rotor is larger at the end close to the heavy impeller, affecting its operating stability.

[0005] Therefore, in view of the above technical problems, how to achieve accurate evaluation of the critical speed of the magnetic levitation rotor and improve the critical speed is a technical problem that technical personnel in this field need to solve. Summary of the invention

[0006] The purpose of this application is to provide a magnetic levitation rotor critical speed prediction model and optimization method to solve the problem of difficult to accurately evaluate the critical speed of the magnetic levitation rotor, and also to optimize and improve the critical speed and improve the operating stability of the rotor.

[0007] To achieve the above-mentioned purpose, the present application provides a critical speed prediction model for a magnetically suspended rotor, comprising a core shaft, impellers are provided at the shoulders at both ends of the core shaft, a permanent magnet is sleeved on the outer periphery of the middle of the core shaft, and an annular portion is sleeved on the outer periphery of the core shaft on both sides of the permanent magnet;

[0008] In the axial direction of the core shaft, the annular portion is spaced apart from the core shaft, and adjacent components in the annular portion are spaced apart from each other, the permanent magnet is spaced apart from the core shaft, and the impeller is in binding contact with the shaft shoulder;

[0009] In the radial direction of the core shaft, the annular portion is in binding contact with the core shaft, and the permanent magnet is spaced apart from the core shaft.

[0010] Preferably, bolts and nuts cooperating with the bolts are provided at both ends of the core shaft, the impeller is pressed at the shaft shoulder by the bolts and the nuts, and the impeller is coaxially arranged with the core shaft.

[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 which are arranged in sequence along the axial direction of the core shaft, the first magnetic isolation ring is close to the shoulder side, and the second limiting ring is close to the shoulder side of the core shaft.

[0012] Preferably, in the axial direction of the core shaft, the opposing surfaces of the first magnetic isolation ring and the position sensor, the opposing surfaces of the position sensor and the second magnetic isolation ring, the opposing surfaces of the second magnetic isolation ring and the first limiting ring, the opposing surfaces of the first limiting ring and the radial magnetic bearing, the opposing surfaces of the radial magnetic bearing and the second limiting ring, and the opposing surfaces of the second limiting ring and the shoulder are all arranged at intervals;

[0013] In the radial direction of the core shaft, 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 fit with the core shaft to achieve binding contact.

[0014] Preferably, the permanent magnet is disposed between the two shoulders, and a third magnetic isolation ring is disposed between the end of the permanent magnet and the shoulder, and in the axial direction of the core shaft, 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 spaced apart;

[0015] In the radial direction of the core shaft, the third magnetic isolation ring is spaced apart from the core shaft.

[0016] Preferably, the permanent magnet and the third magnetic isolation ring are covered with a sheath on their outer peripheries, and the sheath at least covers the permanent magnet and the third magnetic isolation ring in the axial direction, and the sheath is spaced apart from the shoulder in the axial direction of the core shaft;

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

[0018] A method for optimizing the critical speed of a magnetically suspended rotor, based on the above-mentioned critical speed prediction model of the magnetically suspended rotor, comprises:

[0019] S1, the mandrel is provided with a coaxial first through hole along its axis, and the diameter of the first through hole is d 1 , taking the highest critical speed as the target, obtain d 1 The optimal value of

[0020] S2. Perform modal analysis on the model obtained in S1 to obtain its vibration mode, and open a vibration model with a diameter of d at the stationary point of the vibration mode. 2 a second through hole, wherein the first through hole overlaps or partially overlaps with the second through hole;

[0021] S3. In the axial direction of the mandrel, the distance between one end of the second through hole and the stationary point is L 1 , the distance between the other end of the second through hole and the stationary point is L 2 , based on the highest critical speed described in S1, adjust L 1 , L 2 d 2 parameters to further increase the critical speed.

[0022] Preferably, in said S3, L 1 , L 2 d 2 Each parameter is taken into N groups, and N 3 Solve the problem again, perform function fitting based on the result, take the highest critical speed as the target, and obtain L 1 , L 2 d 2 The optimal value of .

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

[0024] This application uses the contact relationship of each component in the finite element model of magnetic levitation rotor dynamics. Specifically, the finite element model takes into account the thermal expansion and contraction caused by the interference assembly method of the material, correctly defines the model boundary conditions and the contact relationship between the parts, so that the model has accurate calculation accuracy, and the error between the simulation and the experiment can be guaranteed to be within 5%. At the same time, by opening a through hole, the critical speed of the model is increased while the external boundary of the model remains unchanged. By reducing the weight of the rotor and adjusting the deweighting position of the through hole, the distance between the center of mass of the magnetic levitation rotor and the geometric center of the magnetic bearing is reduced, thereby improving the operating stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0026] Figure 1 A schematic diagram of the structure of a magnetic levitation rotor in a critical speed prediction model of a magnetic levitation rotor provided in an embodiment of the present application;

[0027] Figure 2 A schematic diagram of a first through hole structure in a magnetic suspension rotor critical speed optimization method provided in an embodiment of the present application;

[0028] Figure 3 A schematic diagram of the second through hole and vibration mode in the magnetic suspension rotor critical speed optimization method provided in an embodiment of the present application.

[0029] In the figure:

[0030] 1-core shaft; 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-shaft shoulder; 12-shoulder; 13-third magnetic isolation ring; 14-permanent magnet; 15-sheath; 16-first through hole; 17-second through hole. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0032] It should be noted that in this embodiment, the directions or positional relationships indicated by "upper", "lower", "front", "back", etc. are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present application. In addition, "first", "second", "third", and "fourth" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0033] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

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

[0035] Specifically, the model includes a core shaft 1, impellers 4 are provided at the shoulders 11 at both ends of the core shaft 1, a permanent magnet 14 is sleeved on the outer periphery of the middle of the core shaft 1, and an annular portion is sleeved on the outer periphery of the core shaft 1 on both sides of the permanent magnet 14. The boundary conditions for determining the model include:

[0036] In the axial direction of the core shaft 1, the annular portion is spaced apart from the core shaft 1, adjacent parts in the annular portion are spaced apart from each other, the permanent magnet 14 is spaced apart from the core shaft 1, and the impeller 4 is in binding contact with the shaft shoulder 11;

[0037] In the radial direction of the core shaft 1 , the annular portion is in binding contact with the core shaft 1 , and the permanent magnet 14 is spaced apart from the core shaft 1 .

[0038] Among them, binding contact means that the contact area of ​​​​the two objects is considered to be completely connected together, and relative sliding or separation between surfaces or lines is not allowed.

[0039] Furthermore, bolts 2 and nuts 3 cooperating with the bolts 2 are provided at both ends of the mandrel 1. The bolts 2 are connected to the mandrel 1 through threads, and the impeller 4 is pressed against the shaft shoulder 11 by the bolts 2 and the nuts 3. For details, please refer to Figure 1 In this way, the impeller 4 is coaxially fixed with the core shaft 1. It should be pointed out that when considering the material of the impeller 4, the material of the impeller 4 can only retain the stiffness attribute and ignore the material density attribute. By defining the center of mass position, center of mass weight, and the moment of inertia of the three rotation axes passing through the center of mass, this method does not need to redefine the contact between models when optimizing the weight of the impeller 4, thereby improving the simulation efficiency.

[0040] In some embodiments, 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, which are sequentially arranged along the axial direction of the core shaft 1. Figure 1 , wherein the first magnetic isolation ring 5 is close to the side of the shaft shoulder 11, and the second limiting ring 10 is close to the side of the shoulder 12 of the core shaft 1. It should be pointed out that the annular portion includes but is not limited to the components given above, and other components can be added or reduced according to actual needs. The specific components and functions of the annular portion can refer to the existing technology and will not be repeated here.

[0041] When determining the model boundary at the corresponding position of the annular portion, in the axial direction of the core shaft 1, the opposing surfaces of the first magnetic isolation ring 5 and the position sensor 6 are spaced apart, the opposing surfaces of the position sensor 6 and the second magnetic isolation ring 7 are spaced apart, the opposing surfaces of the second magnetic isolation ring 7 and the first limiting ring 8 are spaced apart, the opposing surfaces of the first limiting ring 8 and the radial magnetic bearing 9 are spaced apart, the opposing surfaces of the radial magnetic bearing 9 and the second limiting ring 10 are spaced apart, and the opposing surfaces of the second limiting ring 10 and the shoulder 12 are spaced apart;

[0042] In the radial direction of the core shaft 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 fit with the core shaft 1 to achieve binding contact between the annular portion and the core shaft 1 .

[0043] The permanent magnet 14 is arranged 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, in the axial direction of the core shaft 1, the relative surfaces of the permanent magnet 14 and the third magnetic isolation ring 13 are spaced apart, and the relative surfaces of the third magnetic isolation ring 13 and the shoulder 12 are spaced apart; in the radial direction of the core shaft 1, the third magnetic isolation ring 13 is spaced apart from the core shaft 1.

[0044] In addition, a sleeve 15 is provided on the outer periphery of the permanent magnet 14 and the third magnetic isolation ring 13, and the sleeve 15 at least covers 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 sleeve 15, in the axial direction of the core shaft 1, the sleeve 15 is spaced apart from the shoulder 12; in the radial direction of the core shaft 1, the sleeve 15 is interference fit with the permanent magnet 14 and the third magnetic isolation ring 13 to achieve binding contact.

[0045] It should be pointed out that the above-mentioned interval setting means that no contact relationship is set between the two objects, so that the state of one object will not affect the other object. On the basis of the above-mentioned embodiment, no contact relationship is set in other positions between the first magnetic isolation ring 5, the position sensor 6, the second magnetic isolation ring 7, the first limit ring 8, the radial magnetic bearing 9, the second limit ring 10, the core shaft 1, the third magnetic isolation ring 13, the permanent magnet 14, the sleeve 15 and other components. The stiffness of the radial magnetic bearing 9 is replaced by the linear stiffness equivalent, and the linear stiffness is established in the four directions of x, y, -x, and -y respectively; the axial magnetic bearing establishes a linear stiffness in the z-axis direction, and the magnitude is the static stiffness.

[0046] It can be seen that the finite element model of this application takes into account the thermal expansion and contraction caused by the interference assembly method of the material, correctly defines the model boundary conditions and the contact relationship between the various parts, and the contact state between the permanent magnet 14 and the core shaft 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 the impeller 4 does not require the reconstruction of the model, which saves the model construction time and improves the simulation efficiency.

[0047] The present application also provides a method for optimizing the critical speed of a magnetically levitated rotor. The method is implemented based on the above-mentioned magnetically levitated rotor critical speed prediction model. The model improves the critical speed and operating stability of the rotor by optimizing the diameter and position of the deduplication holes.

[0048] The method specifically includes:

[0049] S1, the core shaft 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 d 1 , taking it as the optimization parameter, and taking the highest critical speed as the target, we can obtain d 1 The optimal value of

[0050] S2. Perform modal analysis on the model obtained in S1 to obtain its vibration mode. Please refer to Figure 3 , and open a hole with a diameter of d at the stationary point of the vibration mode 2 The second through hole 17, the first through hole 16 overlaps or partially overlaps with the second through hole 17;

[0051] S3. In the axial direction of the core shaft 1, the distance between one end of the second through hole 17 and the stationary point is L 1 , the distance between the other end of the second through hole 17 and the stationary point is L 2 , based on the highest critical speed in S1, adjust L 1 , L 2 d 2 parameters to further increase the critical speed.

[0052] The method enables the magnetic suspension rotor to seek the highest critical speed by setting the first through hole 16 ; further reduces the mass near the stagnation point by setting the second through hole 17 , and further improves the critical speed based on the first through hole 16 .

[0053] Since the rotor design usually has a heavier primary impeller 4 than a secondary impeller 4, the loads of the two radial magnetic bearings 9 differ greatly during operation, which leads to the instability of the system. 1 , L 2 The size of the magnetic suspension rotor can be reduced, and the distance between the center of mass of the magnetic suspension rotor and the geometric center of the magnetic bearing can be reduced, thereby improving the operating stability.

[0054] The quality near the stationary point is optimized by L 1 , L 2 d 2 The size can be determined by changing L 1 , L 2 d 2 Each parameter is taken into N groups, and N 3 For example, take five groups of each parameter and perform 5 3 Solve the problem again, perform function fitting based on the result, take the highest critical speed as the target, and obtain L 1 , L 2 d 2 The optimal value of .

[0055] It can be seen that this method can improve the critical speed under the condition of unchanged external boundary conditions by optimizing the hole punching and de-weighting. Taking the magnetic suspension rotor with a diameter of 132mm and a speed of 28000rpm as an example, this method can improve the critical speed by about 1000rpm, which can help the rotor reach the design point. At the same time, by reducing the weight of the rotor, adjusting the position of the middle hole for de-weighting, and reducing the distance between the center of mass of the magnetic suspension rotor and the geometric center of the magnetic bearing, the operating stability is improved.

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

[0057] Specific examples are used herein to illustrate the principles and implementation methods of the present application, and the description of the above embodiments is only used to help understand the method and core ideas of the present application. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A critical speed prediction model for a magnetically suspended rotor, characterized in that: It comprises a core shaft (1), impellers (4) are provided at shaft shoulders (11) at both ends of the core shaft (1), a permanent magnet (14) is sleeved on the outer periphery of the middle part of the core shaft (1), and annular portions are sleeved on the outer periphery of the core shaft (1) on both sides of the permanent magnet (14); In the axial direction of the core shaft (1), the annular portion and the core shaft (1) are spaced apart, and adjacent components in the annular portion are spaced apart, the permanent magnet (14) and the core shaft (1) are spaced apart, and the impeller (4) is in binding contact with the shaft shoulder (11); In the radial direction of the core shaft (1), the annular portion is in binding contact with the core shaft (1), and the permanent magnet (14) is spaced apart from the core shaft (1).

2. The critical speed prediction model of the magnetic suspension rotor according to claim 1 is characterized in that: Bolts (2) and nuts (3) matching the bolts (2) are provided at both ends of the core shaft (1); the impeller (4) is pressed against the shaft shoulder (11) by the bolts (2) and the nuts (3); and the impeller (4) is coaxially arranged with the core shaft (1).

3. The critical speed prediction model of the magnetic suspension rotor according to claim 1 is characterized in that: The annular portion comprises 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) which are arranged in sequence along the axial direction of the core shaft (1), wherein the first magnetic isolation ring (5) is close to a side of the shaft shoulder (11), and the second limiting ring (10) is close to a side of a shoulder (12) of the core shaft (1).

4. The critical speed prediction model of the magnetic suspension rotor according to claim 3 is characterized in that: In the axial direction of the core shaft (1), the opposing surfaces of the first magnetic isolation ring (5) and the position sensor (6), the opposing surfaces of the position sensor (6) and the second magnetic isolation ring (7), the opposing surfaces of the second magnetic isolation ring (7) and the first limiting ring (8), the opposing surfaces of the first limiting ring (8) and the radial magnetic bearing (9), the opposing surfaces of the radial magnetic bearing (9) and the second limiting ring (10), and the opposing surfaces of the second limiting ring (10) and the shoulder (12) are all arranged at intervals; In the radial direction of the core shaft (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 fit with the core shaft (1) to achieve binding contact.

5. The critical speed prediction model of the magnetic suspension rotor according to claim 3 is characterized in that: The permanent magnet (14) is arranged between the two shoulders (12), and a third magnetic isolation ring (13) is arranged between the end of the permanent magnet (14) and the shoulder (12), and in the axial direction of the core shaft (1), the opposing surfaces of the permanent magnet (14) and the third magnetic isolation ring (13), and the opposing surfaces of the third magnetic isolation ring (13) and the shoulder (12) are arranged at intervals; In the radial direction of the core shaft (1), the third magnetic isolation ring (13) is arranged at a distance from the core shaft (1).

6. The critical speed prediction model of the magnetic suspension rotor according to claim 5 is characterized in that: The permanent magnet (14) and the third magnetic isolation ring (13) are sheathed with a sheath (15) on their outer circumferences, and the sheath (15) at least covers the permanent magnet (14) and the third magnetic isolation ring (13) in the axial direction, and in the axial direction of the core shaft (1), the sheath (15) is spaced apart from the shoulder (12); In the radial direction of the core shaft (1), the sleeve (15) is interference-fitted with the permanent magnet (14) and the third magnetic isolation ring (13) to achieve binding contact.

7. A method for optimizing the critical speed of a magnetically suspended rotor, characterized in that: The method implemented based on the critical speed prediction model of the magnetic suspension rotor according to any one of claims 1 to 6 comprises: S1, a core shaft (1) is provided with a coaxial first through hole (16) along its axis, the first through hole (16) has a diameter of d1, and the highest critical speed is taken as the target to obtain an optimal value of d1; S2, performing modal analysis on the model obtained in S1 to obtain its vibration mode, and opening a second through hole (17) with a diameter of d2 at the stationary point of the vibration mode, wherein the first through hole (16) overlaps or partially overlaps with the second through hole (17); S3. In the axial direction of the core shaft (1), the distance between one end of the second through hole (17) and the stagnation point is L1, and the distance between the other end of the second through hole (17) and the stagnation point is L2. Based on the highest critical speed described in S1, the parameters of L1, L2, and d2 are adjusted to further increase the critical speed.

8. The method for optimizing the critical speed of a magnetically suspended rotor according to claim 7, characterized in that: In S3, each parameter of L1, L2, and d2 is taken into N groups, and N 3 The solution is obtained again, and function fitting is performed based on the results. The highest critical speed is taken as the target to obtain the optimal values ​​of L1, L2, and d2.

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