Tubular linear induction motor for hydraulic capsule pipeline. I.Finite element analysis

An axisymmetric model of the magnetic field of the tubular linear induction motor (TLIM) for application to hydraulic capsule pipelines is developed using finite element method (FEM) analysis. The FEM model is used to analyze a specific TLIM design at standstill for a given supply current. The finite element formulation of the field equations is discussed and the magnetic field contours at different instants of time are presented. FEM computation of the thrust compares very well with experimental data     

A node-based smoothed point interpolation method (NS-PIM) for thermoelastic problems with solution bounds

A node-based smoothed point interpolation method (NS-PIM) is formulated to analyze steady-state thermoelastic problems. In this approach, shape functions are constructed using the point interpolation method (PIM), which permits the straightforward enforcement of essential boundary conditions. The smoothed Galerkin weak form is then used to construct discretized system equations using smoothing domains constructed based on nodes. The bound property, accuracy and convergence of the present formulation are studied using 1D and 2D thermoelasticity problems. It is found that the computed temperature and its resulted gradient are in very good agreement with the analytical results or those obtained using the finite element method (FEM). Compared with the 3-node triangular FEM, the NS-PIM can achieve better accuracy and higher convergence in energy norm using the same linear triangular mesh. Together with the FEM, we now for the first time have a simple way to obtain both upper and lower bounds of the exact solution to thermoelasticity problems.     

BEHAVIOR OF THERMOELASTIC THICK PLATE UNDER LATERAL LOADS

A mathematical model has been developed and solved for predicting the response of a thick thermoelastic axisymmetric solid plate subjected to sudden lateral mechanical and thermal loads. The governing equations of motion and heat conduction have been solved by using Laplace and Fourier transform methods to predict the response of the plate in the physical time domain. A modified Bessel function solution with complex argument is directly used. The model is also formulated and solved with the help of the finite element method (FEM). The results for radial and axial displacements and temperature change have been computed numerically and illustrated graphically for different theories of generalized thermoelasticity. The comparison of exact analysis with that of FEM is also discussed. Excellent agreement is found between the finite element analysis and analytical and classical solutions.     

Steady-state magnetic circuit analysis of salient-pole synchronous machines considering cross-magnetization

A simple magnetic circuit of salient-pole synchronous machines is presented. A method for calculating steady-state electrical performances using the circuit is described. Magnetic saturation including the cross-magnetizing phenomenon is considered in the method. The saturated reactances, field currents, and load angles are calculated easily from the method without much computational effort as compared with the finite element method. Despite the simplicity of the magnetic circuit, the calculated reactances at various load conditions using the method are close to the measured and FEM values.     

Performance analysis of a brushless and exciterless AC generator

In this paper, the authors propose a novel form of brushless AC generator that does not require a shaft-mounted exciter. The constructional details and operating principle of the generator are described and a method for computing the steady-state performance, using a combined circuit and field approach, is introduced. The two-dimensional finite element method (FEM) is used for calculating the magnetic field distribution at different times-steps, from which the EMF and current waveforms can be accurately determined. A technique for optimizing the use of computer internal memory, with a view of improving the accuracy of solution, is briefly discussed. Computed and experimental performance of a 1 kVA prototype generator are presented     

Simulations and experiments on a 12 kW direct driven PM synchronous generator for wind power

A direct driven permanent magnet (PM) synchronous generator has been designed and constructed and results from the first experimental tests are presented. The generator has been designed using the finite element method (FEM) and dynamic simulations have been performed to study the generator. The simulations are performed by using an electromagnetic model, which is described by a combined field and circuit equation model and is solved in a finite element environment. The stator winding of the generator consists of circular cables and the rotor has surface mounted, arched PMs. A complete experimental setup has been constructed consisting of a motor, a frequency converter, a gearbox and electrical loads. Oscilloscopes are used to measure the voltage and the current for each phase. Measurements have been performed for both full load and no load at rated speed. The harmonic content of the voltage is analyzed and compared to results from simulations. Furthermore, the generated electric power has been calculated from knowing the voltage and current and is compared to the simulated power. The agreement between experimental results and results from simulations based on finite element calculations is very high, especially considering harmonics. Several sources of error are suggested that could cause the small differences between the simulated results and the measured data for the constructed generator.     

Kron's reduction method applied to the time stepping finite elementanalysis of induction machines

The behavior of large induction motors during transient as well as steady state running conditions is of significant interest to the power industry. A variety of analytical predictive tools are employed to aid the design and predict their operation under transient and steady state conditions. This paper presents a strategy to reduce the required running time in order to make a parametric study of induction machines such as the assessment of different design options feasible. This is accomplished by reducing the number of finite element equations that must be solved while maintaining the same level of accuracy of solutions. This method is based on Kron's network reduction work for linear systems and has successfully been applied to large lumped parameter model of transformers. This paper illustrates the reduction method by comparing the flux density in the air gap for a complete FEM model of an induction machine to that of the reduced model. The results are essentially identical with a reduction in computational time of approximately 71%     

Tubular linear induction motor for hydraulic capsule pipeline. II.Finite element method (FEM) maximum thrust design

For part I see ibid., vol. 8, no.2, pp. 251-256 (1993). The axisymmetric analysis of the magnetic field and the finite element method (FEM) formulation of the tubular linear induction motor (TLIM) for application to hydraulic capsule pipelines was discussed in part I. In these studies a three-phase sinusoidal current source supplies the stationary windings to produce a traveling magnetic field inducing currents in the cylindrical capsule conducting wall to produce thrust on the capsule. The results of the different studies using the developed FEM tool show that by introducing iron elements in the pipe wall, the thrust can be increased. Five cases are discussed here, and the magnetic field contours for each case are presented. FEM computation of the thrust for all cases is compared to choose the design which produces the maximum thrust     

A two-dimensional finite element recursion relation for the transport equation using nine-diagonal solvers

Abstract

A Galerkin-based finite element recursion relation is used to solve the heat transport equation in two-dimensions. The finite element method (FEM) is a powerful technique that is commonly used for solving complex engineering problems. However, the implementation of the FEM in multi-dimensional problems can be computationally expensive. A finite element recursion algorithm based on bilinear triangular, bilinear quadrilateral and quadratic Lagrangian approximations are employed to discretize the 2-D advection-diffusion equation. This algorithm is an extension of the 1-D Chapeau (linear element) technique, which employed a tridiagonal recursion expression common to the classical central finite-difference approach. The global matrix is nine-diagonal (for 2-D) and is solved using a modified strongly implicit procedure and a left-to-right sweep method.     

The method of fundamental solutions for solving free boundary saturated seepage problem

The problem of seepage flow through a dam is free boundary problem that is more conveniently solved by a meshless method than a mesh-based method such as finite element method (FEM) and finite difference method (FDM). This paper presents method of fundamental solutions, which is one kind of meshless methods, to solve a dam problem using the fundamental solution to the Laplace's equation. Solutions on free boundary are determined by iteration and cubic spline interpolation. The numerical solutions then are compared with the boundary element method (BEM), FDM and FEM to display the performance of present method.     

Meshless analysis of the substrate temperature in plasma spraying process

The substrate temperature plays a very important role in coating formation and its quality during the thermal spraying. Heating effect of the plasma and particle flux on the substrate is explored in detail in terms of different spraying distances using the meshless local Petrov–Galerkin method (MLPG). Based on this approach, a 3D transient heat transfer model is derived rigorously, in which the moving least-squares (MLS) method is introduced to construct the shape functions. A quartic spline function is selected as the weight function of the MLS scheme and also the test function for the discretized weak form, in which the penalty technique is used to treat the essential boundary conditions. For comparison, the finite element method (FEM) is also adopted to solve the same problem. It is found that the computed temperature is in very good agreement with the empirical data and better than that obtained using FEM, which validates the meshless formulation. Both numerical and experimental results indicate that the spraying distance has a crucial influence on heating effect of the plasma jet and particle flux onto the substrate.     

An adaptive degrees-of-freedom finite element method for 3-D nonlinear magneto-thermal field analysis

An adaptive degrees-of-freedom finite element method (FEM) for 3-dimensional nonlinear magneto-thermal fields is proposed in this article. Both magnetic field and thermal field are discretized using a single FEM mesh, and their degrees of freedom (DoFs) are individually controlled based on the field characteristics. Before solving the algebraic equations, the constrained DoFs are removed using the slave-master technique. The computing time and the storage resources of the second set of FEM mesh are saved while meeting the different requirements on discretization. Data transfer between the thermal and magnetic fields are easily implemented, and mapping errors between different meshes are avoided. To showcase the feasibility and the effectiveness of this method, several numerical examples are tested.     

Small induction motor noise calculation

There has been an increasing demand for a quiet induction motor. Electromagnetic noise is jarring to the ear. Most offensive electromagnetic noise is generated when the natural frequencies of the stator coincide with or are close to the frequencies of the magnetomotive forces. In this paper, electromagnetic noise is calculated by boundary element method (BEM) program using the electromagnetic forces of Maxwell stress. The natural frequency and behavior of the stator are calculated by mechanical finite element method (FEM), considering the contact between stator core and frame. Spring elements are introduced between the stator frame and the stacked core. Vibration is calculated by mechanical FEM. Calculated and experimental noise level were within 3 dB(A) at 1200 and 4080 Hz.     

超导限流器的多目标优化设计算法研究

为优化设计超导限流器参数,提出了超导限流器在电力网络中多目标优化设计的一种改进算法。即先基于MATLAB和PSCAD/EMTDC搭建超导限流器仿真模型,并利用有限元模型对其进行准确性校验;然后根据上海市某配电网搭建电力网络仿真模型,从而进行优化设计。在仿真计算过程中,考虑了短路类型和短路初始相位角所带来的影响,从而使超导限流器的优化参数可以通过三个优化目标和四个约束条件来获得。仿真结果表明,参数优化后的超导限流器能在不影响电网正常运行的同时有效限制短路电流。     

新型中速柴油机的振动响应计算与测量分析

建立了6L16/24型中速柴油机的几何模型,划分了有限元网格,计算了轴承力和侧推力等主要激励力,定义了边界条件,并应用有限元法进行了振动响应分析计算,进行了6L16/24型柴油机的振动测量,有限元振动响应分析结果与振动测试结果对比分析表明:建立的有限元模型合理可行,可用于柴油机的研发。     

An efficient algorithm for phase change problem in tumor treatment using αFEM

Cryosurgery is an effective treatment for killing tumor tissues. During the cryosurgery process, a phase transformation occurs in the undesired tissue. The most popular numerical method for simulation of phase change problem is fixed grid methods where the latent heat is function of temperature. In this paper, a fixed grid method using the alpha finite element (αFEM) formulation is presented to simulate the phase transformation and temperature field during the cryosurgery process for liver tumor treatment. The αFEM model is first established and tuned to have a close-to-exact stiffness compared with the standard finite element method (FEM). Three examples of liver tumor treatment including the single probe for regular shape of tumor, and multiple probes for regular and irregular shape of tumor are presented. The numerical results using alpha finite element method have demonstrated the effectiveness of the procedure.     

面向对象有限元程序设计

提出了一种实用的面向对象有限元程序设计方法。使用UML统一建模语言详细地描述了程序主要对象模型的结构,在此框架结构下运用C 语言编制了有限元结构计算程序,利用该程序进行了工程实例计算分析,验证了本文方法的正确性。     

An edge-based smoothed point interpolation method (ES-PIM) for heat transfer analysis of rapid manufacturing system

This paper formulates an edge-based smoothed point interpolation method (ES-PIM) for analyzing 2D and 3D transient heat transfer problems with mixed boundary conditions and complicated geometries. In the ES-PIM, shape functions are constructed using the polynomial PIM with the Delta function property for easy treatment of essential boundary conditions. A generalized smoothing technique is used to reconstruct the temperature gradient field within the edge-based smoothing domains. The generalized smoothed Galerkin weak form is then used to establish the discretized system equations. Our results show that the ES-PIM can provide more close-to-exact stiffness compared with the “overly-stiff” finite element method (FEM) and the “overly-soft” node-based smoothed point interpolation method (NS-PIM). Owing to this important property, the present ES-PIM provides more accurate solutions than standard FEM using the same mesh. As an example, a practical cooling system of the rapid direct plasma deposition dieless manufacturing is studied in detail using the present ES-PIM, and a set of “optional” processing parameters of fluid velocity and temperature are found.     

改进的SSOR-PCG快速求解法在高面板堆石坝求解效率和节约内存中的实践

针对大型高面板堆石坝有限元计算中常用的直接法存在存储空间大、计算时间长的问题,根据刚度矩阵稀疏性特点,采用对称逐步超松弛预处理共轭梯度法(SSOR-PCG法)的改进算法求解线性方程组,并提出了与该算法相适应的有限元刚度矩阵压缩存储的新方法,以典型面板堆石坝为例,将快速求解法和一维半带宽直接法在计算精度、内存占用、计算耗时三方面进行了比较分析。结果表明,快速求解法具有精度高、速度快、占用内存少的优点,可应用于大规模土石坝有限元分析中。     

A New Variational Multiscale FEM for the Steady-State Natural Convection Problem with Bubble Stabilization

In this paper, a new variational multiscale finite element method (FEM) with bubble stabilization for the steady-state natural convection problem is presented. The new variational multiscale FEM is derived by using a decoupling and linear technique. Compared with the common projection-based stabilized FEM, the new method does not need to introduce any extra degree of freedom. Moreover, the new method has the same convergence precision as the standard Galerkin FEM. Finally, some numerical examples are given to show that the new method is efficient, reliable, and can save a lot of CPU-time for this problem.