A natural electromagnetic magnetic suspension and gas dynamic pressure suspension combined suspension shaft system

Abstract

This invention relates to the field of high-speed rotating machinery technology, and more specifically to a combined suspension shaft system of natural electromagnetic levitation and gas dynamic pressure levitation. The system includes a stator comprising a segmented stator core. The ratio of the number of winding slots to the number of phases, Z / m, is even. The stator has three-phase windings, each of which can form a winding symmetrically distributed along a 180° circumference, generating a 180° symmetrical torque couple. Stator magnetic poles are located on the outer side of each winding slot. A rotor is housed within the stator, and the rotor is equipped with air bearings and segmented magnetic components. The stator and rotor constitute a natural electromagnetic levitation motor. The system employs natural electromagnetic levitation technology combined with foil air dynamic pressure bearing technology to jointly levitate and support the rotor shaft system, supplementing the performance requirements of the foil air dynamic pressure bearing in extreme environments.

Description

Technical Field

[0001] This invention relates to the field of high-speed rotating machinery technology, and more specifically to a combined suspension shaft system of natural electromagnetic levitation and gas dynamic pressure levitation. Background Technology

[0002] High-speed rotating machinery is crucial equipment in energy and power engineering, as well as precision manufacturing, primarily responsible for the conversion between different types of energy. Representative examples include high-speed electric spindle systems, which convert electrical energy into mechanical energy and have significant application prospects in precision drilling and milling. Electric motor-driven high-speed turbine machinery, such as centrifugal air compressors, convert electrical energy into impeller mechanical energy, which in turn is converted into the internal energy of high-pressure air, playing a key role in high-speed blowers and fuel cell air supply systems. Furthermore, high-speed rotating machinery without electric motor input, such as turbochargers, converts gas kinetic energy into rotor kinetic energy via a turbine, which is then converted into the internal energy of high-pressure air via an impeller.

[0003] The efficient and stable operation of these high-speed rotating machines primarily relies on the superior performance of their bearing-rotor systems. Traditional bearing types, such as rolling bearings and grease-lubricated bearings, are limited by their density (DN) values ​​and typically cannot maintain high or ultra-high speeds for extended periods, thus impacting the lifespan and reliability of the rotating machinery. In contrast, foil gas hydrodynamic bearings with elastic support structures offer advantages such as low frictional loss, no DN value limitations, and Coulomb friction damping, making them particularly suitable for supporting high-speed, lightly loaded rotor shaft systems.

[0004] In recent years, to achieve the "dual carbon" goals of carbon neutrality and carbon peaking, China has begun to focus on developing hydrogen energy as a new energy source to replace fossil fuels, and has carried out research and development and industrialization of hydrogen fuel cells. To improve the combustion efficiency of hydrogen fuel cells, high-speed centrifugal air compressors are generally required to provide high-pressure air to the fuel cell stack; therefore, the air compressor is the "lung" of the hydrogen fuel cell. Foil air bearings are core components of the air compressor, supporting the rotor-impeller system to operate at high speeds and stably, typically at speeds below 100,000 rpm. A key reason for this is that bearing damping decreases with increasing speed and frequency. Therefore, the shaft system is at risk of instability under higher speed operating conditions. Furthermore, hydrogen fuel cell applications are typically in highly mobile transportation vehicles. During operation, foil air bearings are subjected to varying degrees of impact and random vibration over extended periods, and also face the risk of surface coating wear and failure during frequent start-stop cycles. These critical requirements pose significant challenges to the performance of foil air bearings or bearing-rotor-motor systems. Summary of the Invention

[0005] The purpose of this invention is to provide a combined suspension shaft system of natural electromagnetic levitation and gas dynamic pressure levitation. It employs natural electromagnetic levitation technology in conjunction with foil aerodynamic pressure bearing technology to jointly suspend and support the rotor shaft system, thus supplementing the performance requirements of foil aerodynamic pressure bearings in extreme environments. All the current in the motor windings participates in naturally levitizing the motor rotor, therefore providing a large force for natural electromagnetic levitation.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A combined suspension shaft system of natural electromagnetic levitation and gas dynamic pressure levitation includes a stator, which includes a segmented stator core. The ratio of the number of winding slots to the number of phases, Z / m, is even. The stator is provided with three-phase windings, each of which can form a winding symmetrically distributed along the circumference at 180°, generating a 180° symmetrical torque couple. Stator magnetic poles are provided on the outer side of each winding slot. A rotor is provided inside the stator, and an air bearing is provided on the rotor. The rotor is provided with segmented magnetic components. The stator and rotor constitute a natural electromagnetic levitation motor.

[0008] The stator poles are distributed in two adjacent stator pole slots;

[0009] The number of winding slots is 24, the number of stator poles is 24, the number of stator pole slots is 48, the number of phases of the natural magnetic levitation motor is 3, and the number of pole pairs of the natural magnetic levitation motor is 2.

[0010] Each phase of the three-phase winding is divided into four pairs of windings symmetrically distributed along a 180° circumference. The starting ends of the four pairs of windings are connected in parallel, and the ending ends of the windings are connected in parallel, forming eight branches. The starting end of each phase winding generates the port of the UVW three-phase winding, and the ending end of each phase winding generates the midpoint O of the UVW three-phase winding, forming the U, V, W three-phase ports of the three-phase winding and the midpoint of the three-phase winding, thus forming a parallel branch three-phase winding with 180° symmetrical parallel connection.

[0011] The stator core is divided into three or more sections, and the magnetic components are divided into three or more sections;

[0012] The segment gap λ of the stator core d =δ, where δ is the electromagnetic air gap of the motor, and λ is the segment gap of the magnetic components. r =λ d ;

[0013] The magnetic component is a 4-pole magnet attached to the surface of the rotor, and a non-magnetic metal sleeve is provided on the outside of the 4-pole magnet.

[0014] The magnetic component is a 4-pole magnet embedded inside the rotor, and a squirrel cage winding is provided on the outside of the rotor.

[0015] The rotor is provided with a thrust plate, and the air bearing includes a radial bearing and a thrust bearing. The radial bearing is a radial foil gas dynamic pressure bearing provided at both ends of the rotor, and the thrust bearing is a thrust foil gas dynamic pressure bearing provided on both sides of the thrust plate.

[0016] The radial foil gas dynamic bearing includes a top foil and a corrugated foil. The inner surface of the rotor-side top foil is coated with a wear-resistant coating. The top foil and the rotor surface cooperate to form an air gap. The corrugated foil is installed between the top foil and the bearing housing. The thrust foil gas dynamic bearing includes a top foil and a corrugated foil. The inner surface of the thrust disc-side top foil is coated with a wear-resistant coating. The top foil and the thrust disc surface cooperate to form an air gap. The corrugated foil is installed between the top foil and the bearing housing.

[0017] The beneficial effects of this invention are as follows:

[0018] Radial active natural magnetic levitation technology and axial passive magnetic levitation technology, combined with the gas dynamic pressure levitation technology of air bearings, have the function of excellent synchronous motor drive. No additional accessories, sensors, or controllers are required. It has natural high reliability and simplicity, and the cost is naturally low. Due to its natural high reliability, the rotational speed of the combined suspension shaft system of this invention can be increased. Since no magnetic levitation sensor is required, it is greatly simplified and the control performance and intelligent diagnostic functions are enhanced.

[0019] Radial foil gas hydrodynamic bearings and thrust foil gas hydrodynamic bearings provide additional radial natural suspension restoring force for high-speed and ultra-high-speed rotor shaft systems to stabilize the radial vibration of the rotor shaft system. They also provide axial passive magnetic suspension restoring force for high-speed and ultra-high-speed rotor shaft systems to help the rotor shaft system maintain a steady position.

[0020] When the high-speed and ultra-high-speed rotor shaft system supported by radial foil gas hydrodynamic bearings and thrust foil gas hydrodynamic bearings is subjected to random and impact vibrations, the radial foil gas hydrodynamic bearings and thrust foil gas hydrodynamic bearings provide additional radial and axial natural magnetic levitation restoring forces to achieve the rotor shaft system's performance of impact resistance and low vibration.

[0021] Radial active natural magnetic levitation and axial passive magnetic levitation forces can provide radial and axial levitation forces for the rotor shaft system at low speeds, which helps reduce coating wear on the surface of foil gas hydrodynamic bearings during start-up and shutdown, and extends the life of radial foil gas hydrodynamic bearings and thrust foil gas hydrodynamic bearings. Attached Figure Description

[0022] The present invention will now be described in further detail with reference to the accompanying drawings and specific implementation methods.

[0023] Figure 1 This is a schematic diagram of the combined suspension shaft system structure of natural electromagnetic levitation and gas dynamic pressure levitation of the present invention;

[0024] Figure 2 This is a schematic diagram of the rotor surface magnet structure of the present invention;

[0025] Figure 3 This is a schematic diagram of the rotor embedded magnet structure of the present invention;

[0026] Figure 4 This is a schematic diagram of the winding connection structure of the present invention;

[0027] Figure 5 This is a schematic diagram illustrating the operating principle of the radial foil gas dynamic bearing of the present invention;

[0028] Figure 6 This is a schematic diagram of the radial foil gas dynamic bearing structure of the present invention;

[0029] Figure 7 This is a schematic diagram of the thrust foil gas dynamic bearing structure of the present invention;

[0030] Figure 8 This is a schematic diagram illustrating the operating principle of the radial foil gas dynamic bearing of the present invention.

[0031] In the diagram: 1. Rotor; 2. Thrust plate; 3. Flywheel; 4. Magnetic component; 5. Stator; 6. Winding; 7. Radial foil gas dynamic bearing; 8. Thrust foil gas dynamic bearing; 9. Non-magnetic metal sleeve; 10. Squirrel cage winding. Detailed Implementation

[0032] The present invention will now be described in further detail with reference to the accompanying drawings.

[0033] like Figures 1 to 8 As shown below, the structure and function of a combined natural electromagnetic levitation and gas dynamic pressure levitation suspension system will be described in detail.

[0034] like Figure 1 As shown, a natural electromagnetic levitation and gas dynamic pressure levitation combined suspension shaft system includes a stator 5, which includes a segmented stator core. The ratio of the number of winding slots to the number of phases Z / m of the stator 5 is even. The stator 5 is provided with three-phase windings, and each phase winding can form a winding 6 symmetrically distributed along the circumference at 180°, generating a 180° symmetrical torque couple. Stator magnetic poles are provided on the outer side of each winding slot. A rotor 1 is provided inside the stator 5. An air bearing is provided on the rotor 1. A segmented magnetic component 4 is provided on the rotor 1. The stator 5 and the rotor 1 constitute a natural electromagnetic levitation motor.

[0035] Air bearings have the functions of protecting the stator and rotor system and improving high-speed stability. They can be foil-type gas dynamic bearings, or different types of foil gas dynamic bearings such as cantilever type or multi-sliding beam type. Air bearings not only play a protective role, but also play a role during normal operation. The higher the speed, the more obvious its role is, and there is no mechanical contact or friction.

[0036] The stator magnetic poles are distributed in two adjacent stator magnetic pole slots. The number of winding slots is 24, the number of stator magnetic poles is 24, the number of stator magnetic pole slots is 48, the number of phases of the natural magnetic levitation motor is 3, and the number of pole pairs of the natural magnetic levitation motor is 2.

[0037] like Figure 4 As shown, each of the 24 stator poles in the stator occupies two adjacent slots. Therefore, the 24 stator poles in the stator need to occupy 48 slots. For clarity, the slot numbers can be even numbers. For example, stator pole 1 occupies adjacent slots 1-2, stator pole 2 occupies adjacent slots 3-4, stator pole 3 occupies adjacent slots 5-6, stator pole 4 occupies adjacent slots 7-8, and so on. Stator pole 24 occupies adjacent slots 47-48.

[0038] Each phase of the three-phase winding is divided into four pairs of windings symmetrically distributed along a 180° circumference. The starting ends of the four pairs of windings are connected in parallel, and the ending ends of the windings are connected in parallel, forming eight branches. The starting end of each phase winding generates the port of the UVW three-phase winding, and the ending end of each phase winding generates the midpoint O of the UVW three-phase winding, forming the U, V, W three-phase ports of the three-phase winding and the midpoint of the three-phase winding, thus forming a parallel branch three-phase winding with 180° symmetrical parallel connection.

[0039] In this invention, each phase winding has four pairs of 180° symmetrical parallel branches. The current in these 180° symmetrical parallel branches is theoretically the same when there is no deviation in the air gap between rotor 1 and stator 5. There is an attractive force between the stator core and rotor 1. When rotor 1 is not rotating, the air gap between rotor 1 and stator 5 is equal, and the attractive force is equal everywhere along the circumference. When rotor 1 rotates, there will inevitably be a deviation in the air gap on both sides of the 180° angle. At this time, rotor 1 will be attracted to the side with the smaller air gap, and the back electromotive force of the parallel branch on the side with the smaller air gap will inevitably increase, and the current will decrease. Conversely, the back electromotive force of the parallel branch on the side with the larger air gap will decrease, and the current will increase. Therefore, the radial tension on the side with the larger air gap increases, and the radial tension on the side with the smaller air gap decreases, inevitably causing the air gap to change in the direction of decreasing deviation and stabilizing the air gap deviation. Therefore, after rotor 1 starts rotating, this invention has the ability to radially and naturally magnetically levitate and restore alignment. This invention has 24 slots (Z), 2 pole pairs (P), and 3 phases (m). Each phase has 4 pairs of 180° symmetrical parallel branch windings, and the three phases have 12 pairs of 180° symmetrical parallel branch windings. Clearly, it can actively restore rotor 1 to center position from 24 directions. Since the back electromotive force is zero when rotor 1 is not started or rotating in its initial state, there is no radial natural magnetic levitation restoring force, and the permanent magnet rotor will be randomly attracted to the side with the smaller air gap. Therefore, when rotor 1 is not rotating, the permanent magnet rotor 1 is radially unstable. Thus, the foil gas dynamic bearing in this invention plays a protective role for the bearing. This invention possesses dynamic radial natural electromagnetic levitation and passive axial magnetic levitation functions using traditional motor drive methods without adding any sensors or controllers. As a permanent magnet motor, this invention naturally also has excellent four-quadrant control functions.

[0040] The stator core is divided into three or more sections to obtain a greater passive magnetic levitation capability in the axial direction. Preferably, it is divided into nine sections. The winding 4 does not need to be divided along with the stator core. The stator winding 4 does not need to be equipped with a position sensor and control circuit. The magnetic components are divided into three or more sections, preferably five or nine sections.

[0041] The segment gap λ of the stator core d =1~2δ, where δ is the electromagnetic air gap of the motor, and λ is the segment gap of the magnetic components. r =λ d The gap between the magnetic components at both ends of rotor 1 along the axial direction is: λ rd =1.5~2λ r =1.5~2λ d This segmentation method gives rotor 1 a passive levitation effect along its axis.

[0042] When λ is less than 1 / 4 to 1 / 5 of the axial length of each segment, the axial magnetic levitation stiffness is almost proportional to the number of segments n. The maximum stiffness of the segmented axial passive magnetic levitation is approximately 0.95nK (N / mm), where K (N / mm) is the stiffness of a single segment of axial passive magnetic levitation; however, the effective axial working range of the magnetic levitation is reduced, approximately 0.95λ.

[0043] The magnetic component 4 is a 4-pole magnet attached to the surface of the rotor 1. A non-magnetic metal sleeve 9 is provided on the outside of the 4-pole magnet. The non-magnetic metal sleeve 9 is a conductive layer, which can be similar to a squirrel cage winding.

[0044] The material of the non-magnetic metal sleeve 9 can be: non-magnetic metal materials such as aluminum, copper, and stainless steel. Thus, the present invention becomes a synchronous motor that can be started asynchronously. The motor of the present invention can start asynchronously, and after reaching near the synchronous speed, it automatically enters synchronous motor operation and becomes a motor that truly has: static and dynamic natural electromagnetic levitation.

[0045] The magnetic component is a 4-pole magnet embedded inside the rotor 1, and a squirrel cage winding 10 is provided on the outside of the rotor 1; 16 squirrel cage guide bars are evenly distributed on the outer circle of the rotor 1, and of course, there is a squirrel cage end ring at the axial end of the rotor 1, making it a motor with inductive starting capability; thus, the present invention becomes a synchronous motor that can be started asynchronously. The motor of the present invention can start asynchronously, and after reaching near the synchronous speed, it automatically enters synchronous motor operation, and becomes a motor that truly has: static and dynamic natural electromagnetic levitation; as a permanent magnet motor, the motor of the present invention naturally also has excellent motor four-quadrant control function;

[0046] The rotor 1 is provided with a thrust plate 2. The air bearing includes a radial bearing and a thrust bearing. The radial bearing is a radial foil gas dynamic pressure bearing 7 provided at both ends of the rotor 1, and the thrust bearing is a thrust foil gas dynamic pressure bearing 8 provided on both sides of the thrust plate 2. When subjected to load, the radial foil gas dynamic pressure bearing 7 and the thrust foil gas dynamic pressure bearing 8 can produce elastic deformation. This elastic deformation gives the radial foil gas dynamic pressure bearing 7 and the thrust foil gas dynamic pressure bearing 8 a certain impact resistance. During the deformation process of the foil, friction will also occur with the bearing seat, etc., providing a certain damping in the dynamic process.

[0047] The nominal gap between rotor 1 and radial foil gas dynamic bearing 7 is smaller than the average electromagnetic air gap between stator core and rotor 1. During the rotation or stop of rotor 1, the stator winding does not have a natural levitation effect on rotor 1, and rotor 1 needs to be supported by radial foil gas dynamic bearing 7.

[0048] The radial foil gas dynamic bearing 7 includes a top foil and a corrugated foil. The surface of the top foil on the rotor side is coated with a wear-resistant coating. The top foil and the surface of the rotor 1 form an air gap. The corrugated foil is installed between the top foil and the bearing housing. The thrust foil gas dynamic bearing 8 includes a top foil and a corrugated foil. The surface of the top foil on the thrust plate side is coated with a wear-resistant coating. The top foil and the surface of the thrust plate 2 form an air gap. The corrugated foil is installed between the top foil and the bearing housing.

[0049] This invention is applicable to both low and high speeds. At low speeds, the stator windings provide the main levitation force, reducing wear on the coating of the foil gas dynamic bearing surface. At high speeds, the dynamic air bearing provides the main levitation force and maintains high-speed stability. The simultaneous action of air suspension and natural suspension improves load-bearing capacity and shaft alignment.

Claims

1. A combined suspension shaft system of natural electromagnetic levitation and gas dynamic pressure levitation, comprising a stator (5), characterized in that: The stator (5) includes a segmented stator core. The ratio of the number of winding slots to the number of phases of the stator (5) is even. The stator (5) is provided with three-phase windings. Each phase winding can form a winding (6) symmetrically distributed along the circumference at 180°, generating a 180° symmetrical torque couple. Stator magnetic poles are provided on the outer side of each winding slot. The stator (5) is provided with a rotor (1). The rotor (1) is provided with an air bearing. The rotor (1) is provided with segmented magnetic components (4). The stator (5) and the rotor (1) constitute a natural magnetic levitation motor. The rotor (1) is provided with a thrust plate (2). The air bearing includes a radial bearing and a thrust bearing. The radial bearing is a radial foil gas dynamic pressure bearing (7) provided at both ends of the rotor (1). The thrust bearing is a thrust foil gas dynamic pressure bearing (8) provided on both sides of the thrust plate (2). The radial foil gas dynamic bearing (7) includes a top foil and a corrugated foil. The surface of the top foil on the rotor (1) side is coated with a wear-resistant coating. The top foil and the surface of the rotor (1) form an air gap. The corrugated foil is installed between the top foil and the bearing seat. The thrust foil gas dynamic bearing (8) includes a top foil and a corrugated foil. The inner surface of the top foil on the thrust plate (2) side is coated with a wear-resistant coating. The top foil and the surface of the thrust plate (2) form an air gap. The corrugated foil is installed between the top foil and the bearing seat. The segment gap λ of the stator core d = (1-2) δ, where δ is the electromagnetic air gap of the electric machine, the segment gap λ of the magnetic force component r = λ d .

2. The combined suspension axis system of natural electromagnetic levitation and gas dynamic pressure levitation according to claim 1, characterized in that: The stator poles are distributed in two adjacent stator pole slots.

3. The combined suspension axis system of natural electromagnetic levitation and gas dynamic pressure levitation according to claim 2, characterized in that: The number of winding slots is 24, the number of stator poles is 24, the number of stator pole slots is 48, the number of phases of the natural magnetic levitation motor is 3, and the number of pole pairs of the natural magnetic levitation motor is 2.

4. The combined suspension axis system of natural electromagnetic levitation and gas dynamic pressure levitation according to claim 3, characterized in that: Each phase of the three-phase winding is divided into four pairs of windings symmetrically distributed along the circumference at 180°. The starting ends of the four pairs of windings are connected in parallel, and the ending ends of the windings are connected in parallel, forming eight branches. The starting end of each phase winding generates the port of the UVW three-phase winding, and the ending end of each phase winding generates the midpoint O of the UVW three-phase winding, forming the U, V, W three-phase ports of the three-phase winding and the midpoint of the three-phase winding, thus forming a parallel branch three-phase winding with 180° symmetrical parallel connection.

5. The combined suspension axis system of natural electromagnetic levitation and gas dynamic pressure levitation according to claim 1, characterized in that: The stator core is divided into three or more sections, and the magnetic components (4) are divided into three or more sections.

6. The combined suspension axis system of natural electromagnetic levitation and gas dynamic pressure levitation according to claim 1, characterized in that: The magnetic component (4) is a 4-pole magnet attached to the surface of the rotor (1), and a non-magnetic metal sleeve (9) is provided on the outside of the 4-pole magnet.

7. The combined suspension axis system of natural electromagnetic levitation and gas dynamic pressure levitation according to claim 1, characterized in that: The magnetic component is a 4-pole magnet embedded inside the rotor (1), and a squirrel cage winding (10) is provided on the outside of the rotor (1).

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