Tb3Sc1.95Lu0.05Al3O12 (TSLAG) crystals are novel and high-quality magneto-optical materials with the most promising application as the core component of Faraday devices. Cracking is an obstacle to TSLAG crystal growth and is closely influenced by crystal thermal stress distribution. In this work, the evolution of thermal stress during TSLAG crystal growth in the initial Czochralski (Cz) furnace is numerically studied. The reasons for high thermal stress in TSLAG crystal are explained based on the results about the melt flow, the temperature distribution in the furnace, and the crystal/melt interface shape. A large crucible with a shallow melt is proposed to address the problem of significant variations in melt depth during TSLAG crystal growth. Based on the numerical results, the proposed design can stabilize the melt flow structure, suppressing changes in the crystal/melt interface shape and effectively improving thermal stress in the TSLAG crystal growth process, which contributes to precisely regulating the preparation of large-sized high-quality TSLAG crystals.

The Continuous Czochralski (CCZ) is a promising approach for preparing low-cost high-quality monocrystalline silicon in the photovoltaic field. To investigate the coupled mechanism of silicon particles melting/migration and melt turbulent heat transfer during the CCZ monocrystalline silicon growth, based on the Euler–Lagrange framework, a three-dimensional transient heat-mass transfer model is developed using the LES method considering the heat exchange between the silicon particles and the silicon melt as well as the particles size change. In addition, we investigated the effects of key silicon particle parameters such as feeding temperature, particle size and feeding speed, on the silicon particles melting/migration and melt turbulent heat transfer. The results show that appropriately increasing the feeding temperature and speed contributes to achieve more concentrated particles distribution and weaken the movement of silicon particles towards the crystalline interface simultaneously, which conduce to eliminate the adverse impact of continuous feeding on monocrystalline silicon growth. And the feeding temperature has a great effect on the temperature fluctuation near the crystalline interface. In addition, when the feeding speed exceeds 1.5m/s, increasing feeding speed has no significant effect on the particles distribution and melting process. Besides, the feeding particle size has a significant effect on the maximum penetration depth of particles. The small silicon particles prefer moving to the crystalline interface driven by thermophoretic force, which is detrimental to the high-quality CCZ monocrystalline silicon growth.

针对目前研究生创新教育难以系统地融入具有中国特色的思政教育元素的问题.课题组基于思想政治教育背景,以华东交通大学机械工程学科研究生为研究对象,在人才培养标准重构、能力素质体系框架构建、跨界创新思维培养、思政教育融入创新课程体系、实践教学资源整合和教育评价体系完善这六个视角下,构建一套多视角融合培育研究生创新能力的培养模式.该模式重在提高机械工程学科创新型研究生培养质量,探索和实践在机械工程学科创新型人才培养中融入中华传统美德、社会主义核心价值观、工程伦理、爱国教育等思政内涵,实现传授创新创业知识与培育具有中国特色的创新型人才目标的有机统一.

The traditional electromagnetic–thermal bidirectional coupling model (EMTBCM) of permanent magnet synchronous motors (PMSMs) requires a long time to solve, and the temperature-induced torque change is not accounted for in the finite element (FE) numerical calculation of the EM field. This paper presents a precise and efficient EMTBC reduced-order solution model. The specific methods are as follows: First, a torque control technology based on the current injection method is proposed for determining the effect of temperature on the properties of EM materials and EM torque in an EM field, and the accuracy of the FE numerical calculation model is improved. Second, we use the improved EM field finite element numerical calculation model (FEMNCM) to analyze the correlation between the EM loss, the temperature, and the load, and we replace the FEMNCM with the EM field reduction model using the least-squares method. Then, we analyze the law of the PMSM’s internal temperature distribution. We choose the GA-BP algorithm with as few samples as possible and a high accuracy and stability to build the regression prediction model of the temperature field. We use this regression prediction model to replace the complex temperature field calculation. After analyzing the EMTBCM solution strategy, the original complex EMTBC numerical calculation model is substituted with iterations of the magnetic field reduction model and the temperature field regression prediction model. The FE numerical calculation is then used to validate the reduced-order model. The proposed model is validated through numerical simulations. The numerical results indicate that the proposed reduced-order EMTBC model in this paper is accurate and computationally efficient.

Abstract in order to study the torque ripple of permanent magnet synchronous motor for electric vehicle, the method of modular poles instead of single pole is adopted to reduce the torque ripple. The modular poles consist of three kinds of permanent magnets with different remanence and are arranged in a sinusoidal distribution. The pole arc length and position of each magnetic pole are calculated according to the cutting area of sinusoidal air gap flux density wave. By changing the cutting area of sinusoidal air gap flux density wave, the optimal pole arc coefficient of each permanent magnet was determined, and the magnet pole combination with the smallest torque ripple value is obtained. The results show that the sine degree of back electromotive force is improved obviously, the cogging torque is decreased greatly, and the motor with modular poles has obvious effect on torque ripple suppression. The torque of the motor with different kinds of magnetic pole combination is more stable than that of the motor with the same kind of magnetic pole combination. In this paper, the method of using modular poles instead of single pole to reduce torque ripple is of positive significance, which provides a reference for the subsequent performance optimization of electric vehicle motor. © 2023 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

The effects of axial magnetic field on the different directional solidification (DS) process were studied by using a transient numerical model of heat and mass transfer and corresponding experiments. The shape of melt-crystal (m-c) interface, melt flow morphology, thermal stress and Fe impurity concentration in the crystal for different DS process have been studied. The simulation results indicate that axial magnetic field provided a slight convex m-c interface shape, better flow pattern, lower thermal stress as well as lower Fe impurity concentration throughout the entire DS process. To further verify the simulation results, multi-crystalline silicon (mc-Si) ingots were prepared and testing were carried out. The experimental results are in good agreement with the simulation results. The experimental results show that a slight convex m-c interface shape was obtained, and the Fe impurity concentration in the middle area of the ingot was lower and higher minority carrier lifetime could be achieved by using the axial magnetic field.

A linear temporal stability analysis is conducted for inviscid sheared convective boundary layer flow, in which the sheared instability with stable stratification coexists with and caps over the thermal instability with unstable stratification. The classic Taylor–Goldstein equation is applied with different stratification factors Js and Jb in the Brunt–Väisälä frequency, respectively. Two shear-thermal hybrid instabilities, the hybrid shear stratified (HSS) and hybrid Rayleigh–Bénard (HRB) modes, are obtained by solving the eigenvalue problems. It is found that the temporal growth rates of the HSS and HRB modes vary differently with increased Jb in two distinct wavenumber (α̃) regions defined by the intersection point between the stability boundaries of the HSS and HRB modes. Based on Jb,cr where the temporal growth rate of the HSS and HRB are equal, a map of the unique critical boundary, which separates the effective regions of the HSS and HRB modes, is constructed and found to be dependent on Js, Jb, and α̃. The examinations of the subordinate eigenfunctions indicate that the shear instability is well developed in the HSS mode, in which the large vortex structures may prevail and suppress the formation of convective rolls; the shear instability in the HRB mode is either “partly developed” when JbJb,cr, thus only plays a secondary role to modify the dominant convective rolls, and as Jb increases, the eigenfunctions of the HSS mode exhibit different transitional behaviors in the two regions, signifying the “shear enhancement” and “shear sheltering” of the entrainment of buoyancy flux.

Three-dimensional unsteady simulations are performed for the turbulent flow and heat transfer in a Czochralski silicon melt for 300 mm crystal growth. The influence of the horizontal symmetry plane in the cusp magnetic field on the melt flow, temperature field, and crystal/melt interface is systematically analyzed. The numerical results show that the melt velocity and its fluctuation near the interface decrease, while the temperature and its fluctuation increase gradually with the downward horizontal symmetry plane position. For each horizontal symmetry plane position, the oscillation frequencies of melt temperature and velocity consist of a basic frequency and its integer multiple frequencies. Thermal waves with a regular shape rotate on the melt-free surface, and the rotational direction is consistent with the crucible rotation. The interface shape is strongly associated with the heat transfer near the interface, which depends on the melt flow direction and velocity magnitude as well as the temperature gradient below the crystal. In addition, the oscillation of interface temperature is affected by the melt flow below the crystal, changing from high-frequency small fluctuation to low-frequency large fluctuation with the horizontal symmetry plane moving down.

Detecting crystal-melt interface shape during growth is critical to understanding boundary phase-change kinetics and manufacturing high-quality bulk crystalline materials. However, even for the widely used Czochralski system, the detection of this blind spot has not yet been realized. Here, we determine the interface shape evolution in situ by analyzing the correlation between the growth interface electromotive force (GEMF) and seed crystal temperature of a growing boule. Due to the direct response of GEMF to interface thermal behavior, our determinations show good agreement with computational simulations and experimental as-grown boules. On this basis, it is possible to trace the real-time kinetics of crystallization and provide quantitative interface feedback, which help reveal boundary heat and mass transfer, optimize growth conditions, and hence improve crystal quality. This GEMF-based feedback mechanism will be applied to other directional solidification methods for preventing interface instability and homogenizing component distribution in oxide, semiconductor, and metal crystalline materials.

In order to effectively reduce the vibration and noise of in-wheel motor for electric vehicle, the radial electromagnetic force wave of in-wheel motor under load is decomposed by Fourier transform, and the results are obtained.The radial electromagnetic force wave has large harmonic amplitude and wide frequency distribution.Finally, the free mode and harmonic response of three different stator configurations are analysed.The results show that: under the action of the radial force wave, the maximum deformation of the stator without cooling channel is 6.639e-5 mm, the maximum deformation of the stator with radial cooling channel is 5.8224e-5 mm, and the maximum deformation of the stator with axial cooling channel is 6.864e-5 mm.The deformation is very small, and there will be no friction and collision between the stator and the rotor during the operation of the in-wheel motor.

The influences of cusp magnetic field on the turbulent melt flow and the crystal/melt interface are studied by three-dimensional unsteady simulations for 300 mm industrial Czochralski silicon crystal growth. Detailed comparisons are implemented for the melt flow pattern, temperature and velocity oscillations as well as the crystal/melt interface with and without magnetic field. It is found that the melt flow is complex and irregular in this system, accompanied with rich flow structures and large temperature and velocity fluctuations. Under the application of cusp magnetic field, the turbulent melt flow is significantly inhibited with the simple flow structure as well as the periodic temperature and velocity fluctuations. The anticlockwise periodical flow in the melt induced by cusp magnetic field can help to reduce the impurity in the crystal and suppress the crystal/melt interface deformation. In particular, the thermal waves on the melt free surface are firstly observed with cusp magnetic field for large-size Czochralski silicon crystal growth, traveling in the direction of crucible rotation.

This paper focused on studying an octagonal thermal field to improve the quality of multi-crystalline silicon ingot. A global numerical model was adopted to investigate the effects of the modified furnace on the temperature distribution and temperature gradients distribution during the directional solidification process. The numerical results indicated that a more uniform temperature distribution and lower temperature gradients were obtained in the modified furnace. Meanwhile, the experimental ingot was obtained by using the modified furnace. Experimental tests of minority carrier lifetime distribution, dislocation clusters, and the average conversion efficiency for the conventional ingot and the modified octagonal ingot were carried out. The results indicated that the modified octagonal silicon ingot could achieve lower defect density, especially near the crucible wall. Therefore, the average conversion efficiency of the modified octagonal ingot was improved by 0.12% compared with the conventional ingot. Furthermore, the mechanism and control of ingot side dislocation multiplication were discussed.

Under the low speed condition, a method of real-time tracking and estimation of rotor position based on PLL technology is proposed, which is used to solve the control system detection accuracy problem of permanent magnet synchronous motor (PMSM) for electric vehicles. The control principles of high frequency signal fluctuation are analyzed, and the mathematical model of three phases PMSM under rotor estimated synchronous rotating reference frame is established. The basic principles of phase locked loop (PLL) are analyzed. Based on phase locked loop, a rotor position estimation method is designed and analyzed. Finally, simulation model of sensorless control system is set up, and the simulation experiment is carried out. The simulation experiment results show that the sensorless control based on PLL can obtain the accurate rotor positions and the excellent control ability. Therefore, the rotor positions estimation method based on PLL is an ideal method for the sensorless control of electric vehicle drive motor, which can provide theoretical and technical support for improving the control precision of PMSM and quality of electric vehicles.

The temperature fluctuation on the crystal melt interface during Czochralski silicon crystal growth is firstly investigated with LES method based on the relationship between kinetic undercooling and growth rate. The effects of crystal and crucible rotation on the temperature fluctuation are analyzed. The results show that when crystal counter-rotates with crucible, the temperature fluctuations on the interface and that in the melt close to crystal are more intense compared with co-rotation. The characteristic frequencies of temperature fluctuations on the interface and that in the melt are identical for counter-rotation. However, this consistency of the characteristic frequencies is not obvious for co-rotation. In particular, the temperature fluctuations on the interface are about 0.4 K and 0.7 K for co-rotation and counter rotation, respectively. Importantly, the influence mechanism of melt flow instability on temperature fluctuation is clarified by the analyses of cross-correlation and local convective heat transport. (C) 2019 Elsevier Ltd. All rights reserved.

A novel method for real-time prediction of the varied interface shape for CZ crystal growth.

We propose a quasi-steady enthalpy method based on fixed-grid to consider the latent heat of phase change during a solidification/melting process of a pure material. The latent heat of phase change released or absorbed at the solid-liquid interface disperses into a region at the interface in the proposed method. It is validated through comparing to the solutions obtained with the adaptive mesh method which is commonly accepted for its accuracy in modeling solidification/melting processes for pure materials. The effects of the dispersed region size and the phase change rate on the simulation accuracy of the proposed method are investigated. Based on the proposed method, a general form of the distribution function of the latent heat of phase change is proposed. The distribution of the latent heat of phase change in the dispersed region is controlled by selecting different forms of distribution function to improve the simulation accuracy. The selecting principle of the distribution function is proposed on the basis of concentrating the latent heat of phase change at the solid-liquid interface. By following the selecting principle, the accuracy can be controlled and the size of the dispersed region does not need to be determined in advance. Two distribution functions of the latent heat of phase change are investigated. Results show that the proper concentration of the latent heat of phase change at the solid liquid interface is favorable for the simulation accuracy. (C) 2017 Elsevier Ltd. All rights reserved.

The cost of producing single-crystalline silicon with the Czochralski method can be reduced by promoting the crystal size and/or crystal pulling rate. However, more latent heat of solidification needs to be released from the melt-crystal (m-c) interface during the crystal growth process. In this study, the C-CO2 chemical endothermic reaction is proposed as a novel and efficient cooling technique to solve this problem. Compared with the conventional gas cooling method, C-CO2 endothermic reaction method can significantly enhance the heat transfer in the crystal at the m-c interface. It was found that the heat transfer is more enhanced with a chemical reaction of smaller activation energy, and the m-c interface becomes flatter. The influence of the carbon concentration in the chemical reactive gas flow on the heat removal in the crystal at the m-c interface is also investigated. The cooling effect is significantly increased with the increase in the carbon concentration when it is small. However, when the carbon concentration in the reactive gas is high, the cooling effect just increases slightly. The research demonstrates that the proposed chemical endothermic reaction is a promising cooling technique to be applied in CZ-Si crystal growth with large size/high pulling rate.