Axial force active balancing method for fluid machinery and motor

Abstract

The invention provides an axial force active balancing method for a fluid machine. The axial force active balancing method for the fluid machine comprises the steps that S1, fluid axial force borne by an impeller of the fluid machine during working is obtained; s2, configuring a motor for driving the impeller, and enabling the motor to generate an electromagnetic axial force through design or control; and S3, the direction of the electromagnetic axial force is opposite to that of the fluid axial force, the magnitude of the electromagnetic axial force is controlled to at least partially counteract the fluid axial force, and therefore the net axial load transmitted to the supporting bearing is reduced. The driving motor is actively designed and controlled to generate electromagnetic axial force which is equal to the pneumatic / hydraulic axial force of the impeller in magnitude and opposite to the pneumatic / hydraulic axial force of the impeller in direction, so that zero returning or minimization of net axial force is realized at the bearing.

Description

Technical Field

[0001] This application relates to the interdisciplinary field of rotating machinery and electrical engineering, specifically to fluid machinery (such as axial flow fans, centrifugal pumps, compressors, etc.) with integrated drive motors, and particularly to a systematic method for counteracting the aerodynamic / hydraulic axial forces generated during the operation of fluid machinery by actively controlling the electromagnetic axial force generated by the drive motor. This method is applicable to various motor topologies, including axial flux motors and radial flux motors, and aims to fundamentally eliminate axial loads on bearings, significantly improving system lifespan and reliability. Background Technology

[0002] In turbomachinery (such as axial / mixed-flow fans, centrifugal / axial pumps, and turbo compressors), the rotating impeller does work on the fluid, increasing its pressure and kinetic energy. According to the principle of action and reaction, the fluid inevitably exerts an axial force of equal magnitude and opposite direction on the impeller. This axial force is transmitted to the bearings of the drive motor through the shaft and is the primary cause of premature bearing fatigue failure, increased mechanical wear, and worsened system vibration and noise.

[0003] Traditional solutions have obvious limitations: 1. Passive bearing solution: Using specialized bearings such as angular contact ball bearings and thrust bearings to bear axial force. This does not eliminate the force, but only increases the load-bearing capacity, leading to increased bearing cost, increased friction loss, and the internal stress caused by the axial force still exists.

[0004] 2. Mechanical balancing solutions: such as using balancing holes, balancing drums, or balancing discs in the pump. These solutions increase internal leakage, reduce efficiency, have complex structures, and usually can only balance most, not all, of the axial forces, resulting in poor dynamic adjustment capabilities.

[0005] 3. Self-balancing scheme for dual-disc motors: In the field of axial flux motors, to counteract their strong axial magnetic attraction between the stator and rotor, symmetrical multi-disc structures such as dual rotors with a single stator or dual stator with a single rotor are commonly used. Although this design balances the axial force inside the motor, it makes the motor structure complex, costly, and increases its size and weight, and completely ignores the possibility of achieving a simpler balance by utilizing external loads (impeller axial force).

[0006] On the other hand, radial flux motors (the most common type of motor) are traditionally considered to have stator and rotor magnetic forces that act primarily radially, resulting in a negligible net axial force. Therefore, the prior art has never considered actively utilizing or controlling radial flux motors to generate a controllable axial electromagnetic force to counteract external axial forces.

[0007] In summary, existing technologies lack a universal, proactive, and electromagnetically precise matching-based method for axial force balancing that can transcend motor topology types, deeply integrate motor design with fluid machinery design, and achieve source cancellation of axial forces at the system level. Summary of the Invention

[0008] This application aims to provide a universal solution for actively balancing the axial force of a fluid machinery rotor, independent of any specific motor topology. Its core objective is to actively design and control the drive motor to generate an electromagnetic axial force equal in magnitude and opposite in direction to the impeller's aerodynamic / hydraulic axial force, thereby achieving zero or minimization of the net axial force at the bearing.

[0009] This application provides an embodiment of an active axial force balancing method for fluid machinery, the method comprising: Step S1: Obtain the axial force of the fluid acting on the impeller of the fluid machinery during operation; Step S2: Configure the motor that drives the impeller, and design or control the motor to generate an electromagnetic axial force; Step S3: Make the electromagnetic axial force opposite in direction to the fluid axial force, and control its magnitude to at least partially counteract the fluid axial force, thereby reducing the net axial load transmitted to the support bearing.

[0010] After step S1, the magnitude and direction of the fluid axial force on the impeller of the fluid machinery under its design conditions and operating range are determined.

[0011] In step S2, the drive motor topology is selected; if the axial flux motor topology is selected, its axial force comes from the axial magnetic pull between the stator and rotor; if the radial flux motor topology is selected, an unbalanced axial magnetic pull is artificially created by actively introducing the axial asymmetric arrangement of the stator and rotor cores, that is, the stator and rotor are not aligned in the axial length and there is an axial offset.

[0012] In some embodiments, the drive motor topology is an axial flux motor, and the electromagnetic axial force is formed by the axial magnetic pull between the stator and rotor of the drive motor topology.

[0013] In some embodiments, when the motor is a radial flux motor topology, the electromagnetic axial force is generated by arranging the stator core and rotor core of the motor asymmetrically in the axial direction.

[0014] In some embodiments, the axially asymmetrical arrangement of the stator and rotor in the radial flux motor topology includes one of the following modes: Mode A: The axial length of the rotor core is longer than that of the stator core, and the rotor protrudes towards the impeller side; Mode B: The axial length of the rotor core is shorter than that of the stator core, and the rotor is recessed towards the non-impeller side; Mode C: The axial lengths of the stator core and the rotor core are the same, but their central axes are offset in the axial direction by a predetermined factor.

[0015] In some embodiments, the static reference value of the electromagnetic axial force is set by adjusting the axial offset between the stator and the rotor core.

[0016] In some embodiments, the method further includes a dynamic balancing step, which involves monitoring or estimating the real-time operating conditions of the fluid machinery; and based on the real-time operating conditions, dynamically adjusting the control degrees of freedom of the drive motor topology to change the magnitude of the electromagnetic axial force so that it tracks the changes in the fluid axial force.

[0017] In some embodiments, the control degree of freedom is the direct-axis current component or power angle of the drive motor topology.

[0018] In some embodiments, in step S3, parameters are determined and solidified in the mechanical design to achieve static axial force balance; the parameters include the air gap length of the axial flux motor or the stator-rotor axial offset of the radial flux motor.

[0019] This application also provides a drive motor for implementing the axial force active balancing method, wherein the motor is an axial flux motor or a radial flux motor, and the stator core and rotor core of the motor are configured to be asymmetrically arranged in the axial direction, so that when the motor is energized, a net axial electromagnetic force in a preset direction is generated between the stator and the rotor.

[0020] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit the disclosure of this application. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A schematic flowchart of an active axial force balancing method for fluid machinery according to this application is shown.

[0023] Figure 2 A schematic diagram of the stator and rotor axial asymmetric arrangement mode of the radial flux motor topology is shown.

[0024] Figure 3 A schematic flowchart of another active axial force balancing method for fluid machinery according to this application is shown.

[0025] Figure 4 A schematic diagram of the path of the axial flux motor topology / radial flux motor topology proposed in this application is shown.

[0026] Figure 5 A schematic diagram of the design method of the axial flux motor as a drive motor topology of this application is shown. Detailed Implementation

[0027] The embodiments of this application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0028] To enable those skilled in the art to better understand the solutions of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0029] In the embodiments of this application, it should be noted that, in this document, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0030] Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one…" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0031] In the description of the embodiments of this application, the words "example" or "for example" are used to indicate exemplification, illustration, or description. Any embodiment or design described as "example" or "for example" in the embodiments of this application is not to be construed as being more preferred or having more advantages than another embodiment or design. The use of the words "example" or "for example" is intended to present relative concepts in a clear manner.

[0032] In addition, "multiple" in the embodiments of this application refers to two or more. Therefore, "multiple" can also be understood as "at least two" in the embodiments of this application. "At least one" can be understood as one or more, such as one, two or more. For example, including at least one means including one, two or more and is not limited to which ones are included. For example, including at least one of A, B and C, then it can be A, B, C, A and B, A and C, B and C, or A and B and C.

[0033] It should be noted that in the embodiments of this application, "and / or" describes the relationship between associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. In addition, the character " / ", unless otherwise specified, generally indicates that the associated objects before and after it are in an "or" relationship.

[0034] It should be noted that in the embodiments of this application, "connection" can be understood as electrical connection. The connection between two electrical components can be a direct or indirect connection between the two electrical components. For example, the connection between A and B can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components.

[0035] This application provides a method for actively balancing axial forces in fluid machinery, such as... Figure 1 As shown, the method includes: Step S1: Obtain the axial force (F_fluid) of the fluid on the impeller of the fluid machinery during operation. Step S2: Configure the motor that drives the impeller, and design or control the motor to generate an electromagnetic axial force (F_em). Step S3: Make the electromagnetic axial force (F_em) opposite in direction to the fluid axial force (F_fluid), and control its magnitude to at least partially counteract the fluid axial force (F_fluid), thereby reducing the net axial load transmitted to the support bearing.

[0036] After step S1, that is, after obtaining the axial force (F_fluid) of the fluid machinery impeller during operation, the magnitude and direction variation law of the axial force F_fluid of the target fluid machinery impeller under its design conditions and operating range are determined.

[0037] In step S2, the system requires the selection of a drive motor topology. If an axial flux motor topology is selected, its axial force F_em originates from the axial magnetic pull between the stator and rotor. If a radial flux motor topology is selected, an unbalanced axial magnetic pull F_em is artificially created by actively introducing an axially asymmetrical arrangement of the stator and rotor cores, i.e., the stator and rotor are not aligned in the axial length, resulting in an axial offset δ.

[0038] like Figure 2 As shown, the axial asymmetric arrangement of the stator and rotor in the radial flux motor topology includes one of the following modes: Mode A: The axial length of the rotor core is longer than that of the stator core, and the rotor protrudes towards the impeller side; Mode B: The axial length of the rotor core is shorter than that of the stator core, and the rotor is recessed towards the non-impeller side; Mode C: The axial lengths of the stator core and the rotor core are the same, but their central axes are offset in the axial direction by a preset amount.

[0039] The principle of axial force generation: Taking mode A as an example, the rotor protrudes towards the impeller side. In the motor's magnetic circuit, magnetic lines of force always tend to choose the path of least magnetic resistance. Because the air gap magnetic circuit on the protruding side of the rotor (impeller side) is relatively shorter (the rotor core provides a closer magnetic path), the magnetic flux density on this side will be higher than on the other side. This axially asymmetrical magnetic flux distribution will generate a net axial magnetic pull between the stator and rotor, pointing towards the side with higher magnetic flux density, i.e., towards the impeller side. By adjusting the magnitude of the offset δ, the magnitude of this axial force F_em can be continuously and linearly adjusted. When the aerodynamic axial force F_fluid generated when the impeller is working points inward towards the motor (i.e., away from the impeller), the F_em generated in mode A, pointing towards the impeller side, can exactly cancel it out.

[0040] A mathematical model of the axial electromagnetic force F_em of the selected motor is established, which characterizes the relationship between F_em and key motor parameters. The F_em model is coupled with the F_fluid model to satisfy the balance equation at the target operating point: F_em + F_fluid = 0 or less than the allowable threshold. For systems with fixed operating conditions, the key parameters are determined through the aforementioned optimization and solidified in the mechanical design to achieve static axial force balance at the design point. The key parameters include the air gap length g of the axial flux motor or the stator-rotor axial offset δ of the radial flux motor.

[0041] The axial asymmetric arrangement of the stator core and rotor core is achieved by one of the following methods: making the axial length of the rotor core longer than that of the stator core, and making a part of the rotor axially protrude from the stator; making the axial length of the stator core longer than that of the rotor core, and making the rotor as a whole recessed within the stator; or making the stator core and rotor core have the same axial length but their central axes are offset in the axial direction by a predetermined amount.

[0042] The static reference value of the electromagnetic axial force (F_em) is set by adjusting the axial offset (δ) between the stator and rotor core.

[0043] In step S3, for a system with fixed operating conditions, key parameters are determined and solidified in the mechanical design through the optimization in step S2, so as to achieve static axial force balance at the design point; the key parameters include the air gap length g of the axial flux motor or the stator and rotor axial offset δ of the radial flux motor.

[0044] For systems with changing operating conditions, dynamic balance control is implemented. A control degree of freedom for rapid adjustment of F_em is identified, and a real-time mapping relationship between F_em and this control degree of freedom is established. The controller estimates the current F_fluid based on real-time operating conditions, calculates the required F_em, and then generates the target electromagnetic axial force in real time by adjusting the control degree of freedom, achieving dynamic tracking and cancellation.

[0045] like Figure 3 As shown, the method further includes step S4: a dynamic balancing step, which monitors or estimates the real-time operating condition of the fluid machinery; based on the real-time operating condition, dynamically adjusts the control degrees of freedom of the drive motor topology to change the magnitude of the electromagnetic axial force (F_em) so that it tracks the change of the fluid axial force (F_fluid).

[0046] The control degree of freedom is the direct-axis current component (I_d) or power angle of the drive motor topology.

[0047] For systems with changing operating conditions, dynamic balance control is implemented; a control degree of freedom for rapid adjustment of F_em is identified, and a real-time mapping relationship between F_em and this control degree of freedom is established; the controller estimates the current F_fluid based on the real-time operating conditions, calculates the required F_em, and then generates the target electromagnetic axial force in real time by adjusting the control degree of freedom.

[0048] like Figure 4 As shown, this application proposes two parallel technical paths: Path 1 is suitable for axial flux motor topologies. It directly utilizes and precisely controls the inherent, powerful axial electromagnetic attraction or repulsion force of the axial flux motor to match and cancel it out with the impeller axial force. Under this path, the motor structure can be simplified, and a single stator and single rotor topology can be adopted.

[0049] Path 2 is suitable for radial flux motor topologies. It creatively introduces and controls a considerable, directional axial electromagnetic force by breaking the traditional axially symmetrical arrangement of the stator and rotor of radial flux motors, in order to balance the axial force of the impeller.

[0050] Motor topology selection and axial force generation mechanism design: Based on system requirements, the drive motor topology is selected. If an axial flux motor is selected, its axial force F_em originates from the axial magnetic pull between the stator and rotor. If a radial flux motor is selected, an unbalanced axial magnetic pull F_em is artificially created by actively introducing an axial asymmetric arrangement of the stator and rotor cores, that is, the stator and rotor are not aligned in axial length, and there is an axial offset δ.

[0051] When the motor is an axial flux motor topology, the electromagnetic axial force (F_em) is constituted by the axial magnetic pull between the stator and rotor of the motor. When the motor is a radial flux motor topology, the electromagnetic axial force (F_em) is generated by intentionally arranging the stator core and rotor core of the motor asymmetrically in the axial direction.

[0052] For axial flux motors as the drive motor topology, such as Figure 5 As shown, the design method of this application specifically includes the following steps: Step S21: Modeling and quantification of aerodynamic / hydraulic axial forces in the target system. Determine the fluid machinery performance parameters, and accurately calculate the magnitude and direction of the fluid axial force F_a acting on the impeller at the design point and key non-design points using CFD simulation or empirical formulas. Establish a database or functional relationship F_a = f(n, Q) that shows how the force varies with operating conditions (such as speed n and flow rate Q).

[0053] Step S22: Establishment of Electromagnetic Model and Controllable Axial Force Design of Axial Flux Motor: Based on the drive requirements, the main dimensions of the motor are initially determined, and the "axial electromagnetic force F_m" is actively controlled as a core performance indicator during the electromagnetic design stage. A functional relationship is established between F_m and key design variables (such as air gap flux density B_g, air gap length g, permanent magnet parameters, current I, and power angle θ): F_m = g(B_g, g, I, θ). A single-stator, single-rotor topology is preferred, utilizing its inherent unbalanced axial force to counteract F_a.

[0054] Step S23: Electromagnetic-fluid axial force coupling matching and integrated optimization: Construct an integrated fan-motor system model, with axial force balance |F_m + F_a| ≤ ε as one of the core constraints, while also satisfying basic performance constraints such as output torque and efficiency. Perform multi-objective optimization on collaborative design variables such as air gap length g, hub ratio, permanent magnet thickness, and blade parameters to obtain the optimal design scheme.

[0055] Step S24: Dynamic Axial Force Balancing Strategy and Control Integration: For systems operating under varying conditions, dynamic balancing is achieved in the motor controller. The current F_a is estimated based on the F_a-nQ mapping relationship, and F_m is fine-tuned by adjusting the motor's d-axis current I_d or power angle θ to track -F_a. Optionally, closed-loop feedback is formed using axial force or displacement sensors to achieve precise zeroing.

[0056] Step S25: Mechanical Integration and Bearing Verification: Design a rigid connection between the impeller and the motor rotor. Select simple bearings such as deep groove ball bearings and verify their lifespan under near-zero net axial force conditions to ensure the mechanical reliability of the system.

[0057] Taking an industrial axial flow fan as an example, the fan has a flow rate Q = 5000 m³ / h, a total pressure P = 200 Pa, and a rated speed n = 1450 rpm. It is driven by an axial flux permanent magnet synchronous motor.

[0058] In step S21, the aerodynamic axial force is quantified. Through CFD simulation, it is obtained that under rated operating conditions, the impeller aerodynamic axial force F_a ≈ 85 N, pointing inwards towards the motor. Simultaneously, a lookup table for F_a under different speeds and flow rates is established.

[0059] In step S22, to simplify the structure and reduce costs, a single-stator, single-rotor surface permanent magnet axial flux motor was chosen for motor selection and electromagnetic design. The motor has an outer diameter of 380mm, an inner diameter of 150mm, and 4 pole pairs. The axial electromagnetic force F_m is taken as the core design objective.

[0060] In step 23, axial force matching and parameter optimization are performed. A parametric finite element model of the motor is established. The air gap length g (0.8-2.0 mm) and permanent magnet thickness h_m (3-6 mm) are used as the main variables for the sweep. The optimization objective is: under rated current, the output torque T_avg > 2 Nm, and the static axial electromagnetic force F_m_static ≈ 85 N (direction opposite to F_a).

[0061] Simulation determined a set of optimized parameters: g = 1.15 mm, h_m = 4.5 mm. At this point, F_m_static ≈ 85 N, T_avg = 2.1 Nm, which meets the matching requirements.

[0062] In step S24, dynamic balance control is implemented. A compensation algorithm is embedded in the motor vector controller: a two-dimensional mapping table of F_m, I_q, and I_d is established based on simulation. During operation, the estimated value of F_a is obtained by looking up the table based on the real-time speed n and airflow command. The required F_m_desired = -F_a is calculated using feedforward, and combined with the current I_q command, the required I_d_ref command is calculated by looking up the mapping table. Real-time tracking of F_m is achieved by adjusting I_d.

[0063] In step S25: Mechanical integration and verification. The impeller is directly mounted on the outside of the motor rotor disk, sharing the main shaft. A pair of deep groove ball bearings (6208) are selected. Prototype testing shows that under rated operating conditions, the net axial force on the bearing housing is less than 5N, and the system operates smoothly and quietly. The calculated bearing life is improved by two orders of magnitude compared to traditional designs.

[0064] Design an axial flow fan for a computer room air conditioner, using an axial flux motor as the drive motor topology. The fan should have an air volume of 3000 m³ / h, a static pressure of 80 Pa, and a rated speed of 1000 rpm. A permanent magnet synchronous motor (radial flux) should be selected as the drive motor.

[0065] Step S21': Quantify the aerodynamic axial force.

[0066] CFD simulation revealed that under rated operating conditions, the impeller aerodynamic axial force F_fluid = 65 N, with the direction pointing axially toward the inside of the motor (i.e., airflow reaction force).

[0067] Step S22': Motor selection and axial force mechanism determination.

[0068] To reduce costs, a standard radial flux permanent magnet motor was selected for modification. Mode A (rotor-protruding type) was chosen, aiming to generate an electromagnetic axial force F_em pointing in the impeller direction (i.e., opposite to F_fluid). The target F_em = 65N.

[0069] Step S23': Electromagnetic design and parameter optimization.

[0070] A reference motor was selected with the following parameters: stator outer diameter 120mm, core length L_sta = 60mm, 4 poles, and rated torque 4Nm. A three-dimensional parametric finite element model was established. The rotor core length L_rot was set to 68mm (longer than the stator), and the axial offset δ (defined as the offset of the rotor core center relative to the stator core center, with offset towards the impeller being positive) was used as a variable. Simulation was performed. With other parameters fixed, δ was scanned from 0 to +10mm. Simulation results show that when δ = +7.5mm, under rated current, the generated axial electromagnetic force F_em ≈ 65 N, pointing towards the impeller, meeting the balance requirements. At this time, the motor output torque is 3.92 Nm (a 2% decrease compared to the symmetrical design), and the efficiency decreases from 92.1% to 91.6%, which is within an acceptable range.

[0071] Step S24': Mechanical implementation.

[0072] Based on the optimization results, the mechanical design was carried out as follows: the rotor lamination stacking length was increased to 68mm. The axial positioning of the shaft and rotor assembly relative to the bearing mounting surface was set to +7.5mm. The axial positioning of the stator core within the housing ensured that its center was offset from the rotor design center by -7.5mm (i.e., achieving δ=+7.5mm). A pair of ordinary deep groove ball bearings (6005) were selected. Since the axial force was actively balanced, the bearings only bore radial force and residual dynamic force, and the calculated life met the requirements. The impeller was directly mounted on the rotor shaft extension end protruding from the stator.

[0073] Step S25': Control integration.

[0074] Since the fan mainly operates near its rated point, static balancing with parameter curing (δ=+7.5mm) is sufficient. The motor uses standard vector control (FOC) drive, controlling only the quadrature-axis current I_q to adjust the speed and airflow, without requiring a special axial force control loop.

[0075] Performance verification and prototype testing showed that, under rated operating conditions, the axial vibration amplitude of the bearing housing was reduced by more than 90% compared to traditional symmetrical motor fans, the bearing temperature rise was significantly reduced, and the system operated smoothly and quietly, verifying that the axial force was effectively offset.

[0076] For applications requiring variable operating conditions, a dynamic control strategy can be employed. The controller estimates real-time F_fluid based on signals such as speed and flow rate, and dynamically adjusts the command value of the direct-axis current I_d by querying a preset F_em = f(δ, I_d, I_q) mapping table or model, thereby fine-tuning F_em and achieving dynamic balance of axial force across the entire operating range.

[0077] This application also provides a fluid machinery rotor axial force balancing system based on active electromagnetic force cancellation, characterized in that it includes: an impeller, a drive motor, a shaft, bearings, and a controller; the drive motor is configured to generate a controllable electromagnetic axial force F_em; the controller is configured to: estimate or obtain the fluid axial force F_fluid based on the working condition information of the impeller, and control the drive motor so that F_em and F_fluid are in opposite directions, and their magnitude is adjusted to at least partially cancel F_fluid.

[0078] The drive motor is a radial flux motor, and its stator core and rotor core are arranged asymmetrically in the axial direction to form an axial offset δ, so as to generate the electromagnetic axial force F_em.

[0079] The drive motor is an axial flux motor, which generates the electromagnetic axial force F_em by adjusting the axial magnetic pull between its stator and rotor.

[0080] This application also provides a drive motor for implementing the aforementioned active axial force balancing method. The motor is an axial and radial flux motor, comprising an impeller, a drive motor, a shaft, and bearings. The drive motor is a radial flux motor, and the direction of the net axial electromagnetic force is configured to be opposite to the direction of the fluid axial force experienced by the impeller during operation. The stator core and rotor core of the motor are configured to be asymmetrically arranged axially, such that when the motor is energized, a net axial electromagnetic force in a predetermined direction is generated between the stator and rotor.

[0081] This application also provides a motor design method for providing drive for fluid machinery and balancing its axial force, comprising: selecting a motor topology; determining the target electromagnetic axial force that the motor needs to generate based on the axial force requirements of the fluid machinery; if a radial flux topology is selected, enabling the motor to generate the target electromagnetic axial force by setting the axial asymmetric geometric parameters of the stator and rotor cores; if an axial flux topology is selected, enabling the motor to generate the target electromagnetic axial force by setting its axial magnetic circuit parameters.

[0082] Compared with the prior art, the present invention has the following significant advantages: 1. This application is the first to propose “actively using the electromagnetic force of the drive motor to counteract the fluid reaction force of the load”, and has successfully applied it to two major types of motor topologies: axial flux and radial flux, covering the vast majority of rotating motor application scenarios, breaking through the traditional thinking that radial flux motors cannot generate controllable axial force.

[0083] 2. The concept of "asymmetrical axial arrangement of stator and rotor to generate controllable axial force" is a significant innovation in the field of radial motors. Through a simple, reliable, and low-cost mechanical structural adjustment (changing δ), it endows ordinary radial motors with an unprecedented "axial force generation" function, without adding any extra electromagnetic components, thus achieving added functionality.

[0084] 3. Regardless of the type of motor used, this method eliminates the axial load on the bearings, allowing for the use of simpler, cheaper bearings (such as common deep groove ball bearings) and significantly extending their lifespan. For axial flux motors, it simplifies the structure; for radial flux motors, it adds valuable functionality with negligible cost increases.

[0085] 4. This application provides a complete solution from static balancing with fixed parameters to dynamic balancing based on current control, adapting to various application needs from industrial fans to variable operating condition air conditioning fans and water pumps.

[0086] 5. This application promotes a paradigm shift in motor design and fluid machinery design from "simple connection" to "force coupling design," laying the core methodological foundation for the next generation of high-performance, high-reliability, and highly integrated fluid transport equipment.

[0087] The above are merely preferred embodiments of this application and are not intended to limit this application in any way. Although this application has disclosed preferred embodiments as above, it is not intended to limit this application. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the technical solution of this application. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. A method for active balancing of axial forces for a fluid machine, characterized in that, The method comprises: Step S1: obtaining the fluid axial force on the impeller of the fluid machine in operation; Step S2: configuring the motor driving the impeller and making the motor generate an electromagnetic axial force through design or control; Step S3: making the electromagnetic axial force opposite in direction to the fluid axial force and controlling the size thereof to at least partially offset the fluid axial force, thereby reducing the net axial load transmitted to the supporting bearing; After step S1, the size and direction variation law of the fluid axial force on the impeller of the fluid machine in the design operating condition and operating range thereof are determined; In step S2, the driving motor topology is selected; if the axial flux motor topology is selected, the axial force is generated from the axial magnetic pull between the stator and the rotor; if the radial flux motor topology is selected, an axial asymmetric arrangement of the stator and rotor cores is actively introduced, i.e., the stator and the rotor are not aligned in the axial length and there is an axial offset, to artificially create an unbalanced axial magnetic pull.

2. The balancing method of claim 1, wherein, The driving motor topology is an axial flux motor, and the electromagnetic axial force is composed of the axial magnetic pull between the stator and the rotor of the driving motor topology.

3. The balancing method of claim 1, wherein, When the motor is a radial flux motor topology, the electromagnetic axial force is generated by making the stator core and the rotor core of the motor axially asymmetrically arranged.

4. The balancing method of claim 3, wherein, The axial asymmetric arrangement of the stator and rotor of the radial flux motor topology includes one of the following modes: mode A: the rotor core is longer than the stator core in the axial length, and the rotor protrudes towards the impeller side; mode B: the rotor core is shorter than the stator core in the axial length, and the rotor is recessed towards the non-impeller side; mode C: the stator core and the rotor core have the same axial length, but the center axes of the two are axially offset by a preset offset.

5. The balancing method of claim 1, wherein, The static reference value of the electromagnetic axial force is set by adjusting the axial offset between the stator and rotor cores.

6. The balancing method of claim 1, wherein, The method further comprises a dynamic balancing step of monitoring or estimating the real-time operating condition of the fluid machine; based on the real-time operating condition, the control freedom of the driving motor topology is dynamically adjusted to change the size of the electromagnetic axial force, so that it tracks the change of the fluid axial force.

7. The balancing method of claim 1, wherein, The control freedom is the direct-axis current component or the power angle of the driving motor topology.

8. The balancing method of claim 1, wherein, In step S3, parameters are determined and solidified in mechanical design to achieve static axial force balance; the parameters include the air gap length of the axial flux motor, or the axial offset of the stator and rotor of the radial flux motor.

9. An electric machine for implementing the balancing method as claimed in claim 1, characterized in that, The motor is an axial flux motor or a radial flux motor, and the stator core and the rotor core of the motor are configured to be axially asymmetrically arranged, so that when the motor is powered and operated, a preset direction net axial electromagnetic force is generated between the stator and the rotor.

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