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The primary parametric resonance of a ferromagnetic rectangular thin plate with axial time-varying velocity in the air-gap field is researched. Through building the analytical model of air-gap field between the elastic plate and armature, the dynamic changes of air-gap field during resonance are determined. On account of electromagnetic boundary conditions, intraplate magnetic field distribution under the magnetization effect is obtained. Within the framework of magneto-electro-elastic theory and Hamilton principle, the motion governing equation of the axially moving ferromagnetic plate subjected to air-gap magnetizing force is finally deduced. For the simply supported constraint, applying the Galerkin method, the ordinary differential vibration equation of plate under parametric excitations is obtained by separating time–space variable. The multiscale method is applied to investigate the parametric vibration behavior of plate. Based on Lyapunov stability theory, the stability criterion of steady-state amplitude solutions is acquired. Through numerical methods, the correctness of analytical results is verified. The effects of armature and time-varying parameters on the static deflection, steady-state response amplitude, and the regional distribution of stable solutions are studied. The dynamic stability and bifurcation characteristics of the system are explored. Eventually, the results reveal that the static deflection caused by the air-gap magnetizing force makes the thin plate more rigid. The increase of armature and time-varying parameters causes the stable solutions to reduce and then grow by affecting the stiffness and excitation. At high magnetic potential amplitude, high velocity, and small tension, the system motion exhibits prominent chaotic characteristics.

This paper proposes an E-core outer-rotor hybrid-excitation flux switching (OR-HEFS) machine for in-wheel direct driving application. According to the general air gap field modulation theory, the magneto-motive force (MMF) permeance model was established to investigate the air gap flux density, and then the torque generation, the flux regulation principle, and the excitation-winding-induced voltage of the E-core OR-HEFS machine were analyzed. To characterize the output performances, the influence of the design parameters was investigated for the E-core OR-HEFS machine, including the split ratio, stator tooth arc, PM arc, fault-tolerant tooth arc, rotor tooth arc, stator yoke width and rotor yoke width. The performances contained the output torque, torque ripple, flux regulation ratio, and the excitation-winding-induced voltage. On this basis, the aforementioned four performances were optimized by means of the non-dominated sorting genetic algorithm II (NSGA-II). Based on the optimization result, a prototype was manufactured and tested to verify the whole investigation of this paper.

The Double Permanent Magnet Vernier (DPMV) machine is well known for its high torque density and magnet utilization ratio. This paper aims to investigate the torque generation mechanism and its improved design in DPMV machines for hub propulsion based on the field modulation principle. Firstly, the topology of the proposed DPMV machine is introduced, and a commercial PM machine is used as a benchmark. Secondly, the rotor PM, stator PM, and armature magnetic fields are derived and analyzed considering the modulation effect, respectively. Meanwhile, the contribution of each harmonic to average torque is pointed out. It can be concluded that the 7th-, 12th-, 19th- and 24th-order flux density harmonics are the main source of average torque. Thanks to the multi-working harmonic characteristics, the average torque of DPMV machines has significantly increased by 31.8% compared to the counterpart commercial PM machine, while also reducing the PM weight by 75%. Thirdly, the auxiliary barrier structure and dual three-phase winding configuration are proposed from the perspective of optimizing the phase and amplitude of working harmonics, respectively. The improvements in average torque are 9.9% and 5.4%, correspondingly.

Purpose This paper aims to investigate and analyze the air-gap field modulation (AGFM) effect on torque contribution in a 6-slot/4-pole high-speed permanent magnet (HSPM) machine. To further illustrate the torque generation mechanism, the torque contribution is quantified using the Maxwell stress tensor (MST) method. Design/methodology/approach First, a simplified permanent magnet (PM) magnetomotive force model is established to identify the effective main-order working field harmonics. Then, the MST method is used to determine the average torque contributions of the effective main-order working field harmonics. Finally, the influences of various stator and rotor parameters on the AGFM effect are analyzed and optimized to enhance the torque density. Findings Apart from the fundamental harmonics, the AGFM harmonics contribute non-negligible average torque on the HSPM machine, and the optimized machine has higher torque density. Finally, a prototype of the 10 kW HSPM machine is manufactured and experimented with to validate the effectiveness of the theoretical analysis. Originality/value In this paper, the torque generation mechanism of the HSPM machine is investigated and analyzed. Meanwhile, the AGFM effect of the HSPM machine with different design parameters is analyzed and optimized to enhance the torque density.

The different pole–slot combinations of outer rotor surface-mounted permanent magnet (ORSPM) motors are designed and analyzed to satisfy EV driving requirements. Firstly, the analytical model for various slot–pole combinations of ORSPM motors is proposed based on the air-gap field modulation effect. Then, some of the in-wheel motor parameters and requirements are obtained for the vehicle system. In addition, some special pole–slot combination ORSPM motors are built to achieve higher flux density, and the electromagnetic performance is compared based on the finite element (FE) model, revealing that the 56-slot/48-pole (54s48p) in-wheel motor has a higher torque density and superior flux weakening capability than other cases. Finally, a 13 kW prototype with 54s48p is manufactured and tested to confirm the effectiveness of the FE analysis.

Since the slot opening is large in the uniform slot machine, the torque ripple generated by overlapping or misaligning with the rotor cavity is remarkably large in the case of interior permanent magnet (IPM) machine. In this work, it is observed that the magnitude of torque ripple depends strongly on the phase difference between air-gap field harmonics: The ripple is minimized when the two dominant harmonic components cancel each other. Based on this fact, a condition is developed to minimize torque ripple by adjusting the q-flux channel width and d-flux barrier width. The torque ripple minimizing solution is found from a level chart made by subdomain time-stepping analysis. Finite element analysis (FEA) also gives a very similar minimizing solution. A prototype machine is manufactured, and its performances are validated through experiments.

In the field of ocean engineering, the variation of flow field during ship-to-ship (STS) interaction has been a hot topic. Noteworthy, the effect of vortex distribution on flow field characteristic variations during STS interaction remains insufficiently researched. This study modifies the RNG k-ε model using the OpenFOAM platform and verifies its reliability by comparing it with literature data. Subsequently, extended research is conducted to investigate the flow field characteristics of two different ship hull sections under different Reynolds numbers (Re=68,000 and Re=6800), analyzing velocity components, vortex distribution, and trends in pressure and turbulent kinetic energy fields relative to the vortex field. The research reveals that Re primarily governs changes in upstream and downstream flow fields, while in the gap field, the variation in flow field characteristics is more constrained by geometry and boundary conditions. This research provides a valuable reference for assessing flow field characteristics in STS interactions.

In order to analyze the DC winding induced voltage in the wound-rotor synchronous machine, this paper uses the air-gap field modulation principle to investigate its operation mechanism and harmonic order. By establishing the analytical magneto-motive force (MMF)-permeance model, the DC winding induced voltage per electrical cycle under open-circuit condition, armature reaction condition and on-load condition are deduced. Analytical analysis shows that the MMF function, stator and rotor permeance function are critical factors that influence the harmonic order of the DC winding induced voltage. The analysis results are compared with those predicted by the finite element analysis (FEA). Both non-linear steel and linear steel conditions are accounted in the FEA analysis, and the results show that the analytical deduction result agrees well with the FEA analysis result.

Environmental problems associated with emergency emissions, indoor air pollution with harmful particles, and the spread of viruses and bacteria make the topic of cleaning indoor air from small particles of pollution relevant. In the event of a dangerous situation associated with the presence of small particles in the air, especially those smaller than 10 μm, methods for quickly cleaning the air from such pollutants are required. One of these new methods is the efficient spraying of fine aerosol using the ultrasound technique. Fine aerosol with a droplet size of about 30–50 μm interacts more effectively with pollutant particles compared to larger aerosols. In this paper, the process of interaction of droplets with a characteristic size of 30–50 μm with airborne pollutant particles sized 0.1–10 μm is theoretically studied. Particular attention is paid to particles sized 0.1–2 μm, which are the most difficult to remove from the air. The work will serve as a theoretical basis for the development of methods for cleaning indoor air of pollutant particles using fine aerosol.

Studying the magnetoelastic coupling vibration of moving plates under the influence of complex air-gap magnetic fields is of theoretical significance for modeling multi-field dynamics and solving nonlinear dynamic issues. This paper considers the scenario where an armature wall acts on one side of an axially moving ferromagnetic thin plate and investigates the multiple resonance of the plate subjected to a harmonic excitation in the air-gap magnetic field. First, based on electromagnetic theory combined with boundary conditions of the magnetic field, the distribution of the air-gap magnetic field is determined by solving the Laplace equation of the magnetic scalar potential function. Next, expressions for the magnetic and Lorentz forces acting on the moving ferromagnetic plate are derived. Then, the thin plate energy expression considering geometric nonlinearity and the virtual work expressions of the forces are obtained by applying the Kirchhoff plate theory and the principle of virtual work. Subsequently, the nonlinear vibration equation of the system with magnetoelastic coupling is established using the Hamiltonian variational principle. Utilizing the established mechanical model, the principal-internal resonance is analytically solved employing the Galerkin and multiple scales methods, with stability criteria for steady-state motion solutions determined using Lyapunov stability theory. Finally, the nonlinear dynamics of the system are analyzed through analytical and numerical examples, and the influences of different physical parameter variations on the dynamic behavior are discussed. Results indicate that variations in physical parameters affect the amplitude, resonance region, and regions of multiple solutions of the system. Moreover, the system may transition to chaos through quasiperiodic torus breakdown or period-doubling bifurcation due to changes in physical parameters. The results of this study provide theoretical references for research in magnetoelastic coupling nonlinear dynamics in fields of magnetic drive and electromagnetic control, as well as for product design and optimization.