International Journal of Applied Electromagnetics and Mechanics - Volume 62, issue 4

Authors: Sun, Hongyu | Wang, Shen | Huang, Songling | Wang, Qing | Zhao, Wei

Article Type: Research Article

Abstract: Electromagnetic ultrasonic testing, based on the propagation characteristics of the ultrasonic wave in the medium, is an effective technique for defect detection. The structural of the electromagnetic acoustic transducer (EMAT) determines the detection effect, which should be reasonably designed. We propose an improved unilateral point-focusing EMAT structure with curved coils in this manuscript. The 3D model of the designed EMAT is numerically simulated utilizing the finite element method, and the bilateral point-focusing EMAT is also studied for comparison. The simulation results of the magnetic field intensity and the distributions of the displacement are shown in the manuscript, which prove the …effectiveness of the improved unilateral point-focusing EMAT. Five impact parameters such as aperture angle, focal position, excitation current, lift-off distance, and coil winding number are investigated in detail. We verify the calculation results of the aperture angle and excitation current by the experiments. The conclusion shows that the focusing intensity of the improved unilateral point-focusing EMAT is relatively higher, and other factors also have a significant effect on the focal intensity. Show more

Keywords: Point focusing, electromagnetic acoustic transducer (EMAT), unilateral, bilateral, numerical simulation

DOI: 10.3233/JAE-190071

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 62, no. 4, pp. 645-662, 2020

Authors: Jiang, Jinbo | Yang, Linsen | Yang, Wen | Su, Yi | Liu, Chang | Qiu, Li | Chen, Long | Yu, Kun

Article Type: Research Article

Abstract: Coil inductance calculation is one of the difficulties in Tesla transformer design. The estimation formulas of the conical winding Tesla transformers with different structures are derived by the simplified equivalent of magnetic circuits, and the estimation results are quite different and inaccuracy. This paper provides an energy method based on the FEM (finite element method) to calculate the coil inductance for a double-core conical winding Tesla transformer. A two-dimensional FEM simulation model is established, the magnetic flux density and flux lines distribution have been analysis. And the primary and secondary inductances of the transformer are calculated. Compared the estimation formula …results with the FEM results, the results show that the error difference calculated by the formula estimation is about 3.61%, and the FEM error difference is about 0.4%. The calculation results of FEM are more accurate and convenient, and this method can provide reference for the design of conical winding Tesla transformers. Show more

Keywords: Tesla transformer, conical winding, inductance calculation, magnetic field distribution

DOI: 10.3233/JAE-190089

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 62, no. 4, pp. 663-671, 2020

Authors: Park, Eui-Jong | Jung, Sang-Yong | Kim, Yong-Jae

Article Type: Research Article

Abstract: The magnetic gears which can replace the mechanical gear system are actively studied recently. Improving the power density is growing importance because the characteristics that as gear ratio grows so power density decreases were observed. This paper analyzes the various characteristics (power density, efficiency, torque ripple, loss, and so on) according to the gear ratio in detail, and proposes a concept that high gear ratio by combining two low gear ratio. A target gear ratio is 10 to 1 and application is 1 kW wind turbine. To obtain the optimal combination, 30 gear ratios were considered, and initial design process was …shown about this concept to propose the direction of improving the power density. All models were analyzed with 2D-FEM by numerical analysis. Show more

Keywords: Finite element analysis, magnetic gears, power density, high gear ratio

DOI: 10.3233/JAE-190097

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 62, no. 4, pp. 673-682, 2020

Authors: Toghraie, Davood

Article Type: Research Article

Abstract: Optimization of the cooling processes by fluids in many industries such as power generation, transportation, machining, and electronics is very important. Heat transfer equipment to achieve higher efficiency, need to downsizing of the equipment, and increase the heat transfer rate per unit of surface. The aim of this paper is to investigate the effect of MHD mixed convection flow of Cu-water nanofluid in a trapezoidal lid-driven cavity with different tilt angles in a range of 0° to 60°. The cavity consists of the non-uniformly heated bottom wall, insulated top wall, and isothermal sidewalls. The governing equations of the flow by …using the finite volume method and the SIMPLE algorithm have been numerically solved. The studies for the wide range of Richardson number (Ri) from 0.01 to 10, volume fraction of nanoparticles from 0.1% to 4% and Hartman number (Ha) from 0 to 40 in the steady-state have been done. Result in the form of streamline, vorticity and temperature contours for three geometry, local Nusselt number graphs for non-uniformly heated bottom surface and velocity profile on the vertical centerline of the cavity in different geometry have been investigated. The results show that the average Nusselt number on the non-uniformly heated bottom wall is dependent on dimensionless parameters and tilt angles. Also, applying a magnetic field, reduce the velocity profile changes, and using nanoparticles will cause increasing the Nusselt number. Show more

Keywords: Mixed convection, magneto-hydrodynamic, trapezoidal cavity, non-uniformly heated surface

DOI: 10.3233/JAE-190123

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 62, no. 4, pp. 683-710, 2020

Authors: Iwamoto, Yuhiro | Nakasumi, Hayaki | Ido, Yasushi | Yamaguchi, Hiroshi

Article Type: Research Article

Abstract: Mn-Zn ferrite-based magnetic fluid is temperature-sensitive. Because of the low Curie temperature of Mn-Zn ferrite particles, magnetization is dramatically attenuated as the temperature rises. This temperature-dependent magnetization can be used to transport heat by magnetically driving a fluid via the application of a non-uniform magnetic field and heat. A potential application of this scheme is long-distance heat transport without the use of mechanical pumps. In the present work, a miniaturized magnetically-driven heat transport device with an inner diameter of 𝜙1.54 mm and a flow path length of 1,500 to 6,000 mm was fabricated. The influence of flow path length on the flow …rate induced by the magnetic body force was investigated experimentally and theoretically. Although the flow rate decreased with increasing flow path length due to friction loss, the driving pressure increased with rising heater temperature because of the temperature-dependent magnetization. The influence of flow path length on the driving pressure is relatively insignificant. An increase in the flow path length leads to effects that both attenuate and enhance the driving pressure. Substantial long-distance (6,000 mm) heat transport was realized by applying a non-uniform magnetic field and heat. Show more

Keywords: Magnetic nanofluid, heat transfer, magnetic fluid, temperature-dependent magnetization, energy conversion

DOI: 10.3233/JAE-190033

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 62, no. 4, pp. 711-724, 2020

Authors: Yan, Xinxiao | Li, Yongjian | Cheng, Zhiguang | Zhang, Changgeng

Article Type: Research Article

Abstract: A 3-D coupled magneto-fluid-thermal model is established for temperature rise prediction in a ventilated dry-type transformer rated at 2500 kVA. In order to accurately estimate electromagnetic losses, a three-dimensional (3-D) transient finite element method considering the effect of eddy-current losses on the foil type windings is proposed. Besides, two orthogonal B -P loss curves are adopted to model the anisotropy of grain-oriented (GO) silicon steel. The non-uniform power losses of winding and core are mapped into the thermal field as heat sources. Moreover, the transformer structures such as the narrow struts, insulation barrier and clamps are considered to improve the …computational accuracy of air velocity and temperature distribution. At last, the test of temperature rise has been carried out to verify the proposed model. Show more

Keywords: Dry-type transformer, eddy currents, power losses, magnetic measurements

DOI: 10.3233/JAE-190054

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 62, no. 4, pp. 725-735, 2020

Authors: Yan, Dong | Guo, Liyan | Shi, Tingna | Wang, Huimin | Yan, Yan | Xia, Changliang

Article Type: Research Article

Abstract: The split ratio is one of the most important design parameters of the machines and has a significant effect on the electromagnetic performance. Using the split ratio, this paper presents a performance analysis method for permanent magnet (PM)-assisted reluctance machine is presented. An accurate analytical model, which considers the saturation of outer iron ribs and the asymmetric saturation of rotor islands, is firstly proposed. In order to reduce the numbers of the adjustable structural parameters during the initial design process and ensure the independence among the parameters, a geometric structure corresponding to the split ratio is then established. The effectiveness …of the proposed analytical model based on the split ratio is verified by FEM, and applied to analyze the electromagnetic performance for the three-flux-barrier PM-assisted reluctance machines. On the basis of the analysis results, the design scheme corresponding to the optimal split ratio, which makes the machine obtain a higher efficiency and guarantees the PMs without irreversible demagnetization, is determined rapidly. Show more

Keywords: Permanent magnet (PM)-assisted reluctance machine, the gradient flux barrier, split ratio, analytical model

DOI: 10.3233/JAE-190104

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 62, no. 4, pp. 737-761, 2020

Authors: Zhou, Hongliang | Zhao, Wu | Zhang, Huiduan | Wang, Yanqin | Wu, Xuefeng | Sun, Zhijia

Article Type: Research Article

Abstract: Magnetorheological fluid (MRF) sealing technology has gained more and more attention in civil engineering, safety engineering, manufacturing, life science, aviation and so on, owing to its great pressure bearing capacity due to the viscous stress and controllable yield stress of MRF under external magnetic field. Even if overpressure occurs, magnetorheological seal (MRS) can restore the serviceability automatically with the help of magnetic field when pressure difference drops back. To have a deep understanding of magnetorheological sealing technique, the paper begins with an introduction of the basic features of MRF and relevant applications of MRS. Then several basic design issues of MRS structure are …introduced. Furthermore, main factors influencing MRS performance are discussed on how to increase the pressure drop of MRS structure. In the end, modeling techniques of MRS structure are provided according to Bingham plastic model, Bi-viscous model, Herschel–Bulkley model and Herschel–Bulkley model with preyield viscosity, respectively, for calculating yield stress of MRF and pressure drop of MRS structure. Hopefully, this review can be regarded as a useful complement to other reviews on MRF technology and applications. Show more

Keywords: Magnetorheological seal, magnetorheological fluid, structure, performance, modeling

DOI: 10.3233/JAE-190082

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 62, no. 4, pp. 763-786, 2020

Authors: Li, Ke | Ling, Feng | Sun, Xiaodong | Cai, Yingfeng | Zhao, Dean | Yang, Zebin

Article Type: Research Article

Abstract: The traditional displacement sensors used in the bearingless induction motors (BIM) have many disadvantages, such as high cost, poor temperature stability, low conversion efficiency and complex motor operation. To improve these disadvantages, the detailed study on the novel displacement sensorless control based on the model reference adaptive system (MRAS) is presented in this paper. Firstly, the principle of radial suspension force generation and the mathematical model of the BIM are introduced. Secondly, the basic structure of the proposed MRAS is constructed and the stability is verified by the Popov’s integral inequality. Thirdly, to improve the control accuracy and dynamic characteristics …of sensorless vector control system, a method of directly controlling rotor eccentric displacement by using suspension force compensation is proposed. Finally, the feasibility and accuracy of the proposed method have been verified by the simulation and experimental results. According to the results obtained, the radial displacement of the rotor can be accurately estimated, and the rotor displacement sensorless control of the BIM based on MRAS is achieved. Show more

Keywords: Bearingless induction motor, model reference adaptive system, rotor displacement sensorless control, direct suspension force control

DOI: 10.3233/JAE-190118

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 62, no. 4, pp. 787-805, 2020

Authors: Ding, Li | Zhang, Jiasheng | Lin, Aiguo | Ge, Yulei

Article Type: Research Article

Abstract: In actual operation, the skin effect electric heat tracing system is powered by the inverter circuit, and the higher harmonic components are inevitably introduced. There is not much research on the influence of harmonic current on the electric heat tracing load loss. In this paper, the harmonic distribution under PWM driving mode is analyzed, and the load loss of the electric heat tracing body under harmonic current is derived. The co-simulation method of PWM inverter circuit and skin electric heat tracing body coupling is proposed. The simulation results of current and loss of co-simulation method and sine wave driving method …are compared. The results show that the parameters of PWM driving mode increase to different degrees, which proves the correctness of the joint simulation method. At the same time, the influence of the output characteristics and modulation parameters of the PWM inverter circuit on the load loss of the electric heat tracing body is analyzed, which provides a theoretical basis for the determination of the parameters of the inverter circuit. In addition, combined with multi-physics coupling analysis, this paper obtains more accurate temperature distribution results of the electric heat tracing system without scaling the size of the electric heat tracing ontology. Not only can we intuitively understand the material selection and hot spot configuration of the electric heat tracing components, but also further understand the influence of current harmonics on the load loss in actual operation, so as to better realize the efficient heat tracing of the skin electric heat tracing system. Show more

Keywords: Electric heat tracing system, harmonic analysis, loss calculation, co-simulation, multi-physics coupling analysis

DOI: 10.3233/JAE-190106

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 62, no. 4, pp. 807-822, 2020