共查询到20条相似文献,搜索用时 31 毫秒
1.
火电厂中的循环水系统具有管径大、流速低等特点,常规测量仪器难以测准其流量,造成循环水泵电耗较大。通过分析两种不同类型时差法超声波流量计的基本原理,说明了现场应用超声波流量计可能遇见的问题,并对其常见故障和解决措施进行了归类分析。现场实际应用表明,使用超声波流量测量系统具有高集成度、反应速度快、测量准确度高等特点。 相似文献
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通过计算流体力学和磁流体动力学的耦合计算,直接给出了一种电磁流量计二维模型里流动(层流)和外加磁场(均匀稳态)的相互作用结果,并得到信号输出即感应电动势与流量的基本关系以及其他变量如感应电场与感应电流的详细空间分布。模拟结果符合理论值,表明可利用磁流体动力学数值模拟来广泛研究不同流场和外加磁场分布下电磁流量计特性。 相似文献
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In this paper, the practical operating equation for the electromagnetic flowmeter is derived for the case of having a circular pipe with an electrolytic conductor flowing through. It is assumed further that the magnetic field is uniform and the velocity profile is axisymmetric (assuming nonconducting walls). The derivation was done before by many authors to whom the author refer to in this paper, but the approach provided here is comprehensive and simple. To add to that, the solution for the electromagnetic flowmeter's operating equation illustrated in this paper is new and is provided using very simple mathematical concepts, eliminating the complexity of solutions provided by other authors in the past. In the end, the practical operating equation derived was validated using a new approach based on the finite element analysis and the moving stream method to estimate the error resulting from using this operating equation with the assumptions of having a uniform magnetic field and an axisymmetric velocity profile, which are difficult to achieve in practice. This error can be used in a dry calibration to estimate the error caused by variable flow characteristics. 相似文献
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《International Journal of Engineering Science》2007,45(2-8):467-485
This paper investigates the plane stress problem of generally anisotropic magneto-electro-elastic beams with the coefficients of elastic compliance, piezoelectricity, dielectric impermeability, piezomagnetism, magnetoelectricity, and magnetic permeability being arbitrary functions of the thickness coordinate. Firstly, partial differential equations governing stress function, electric displacement function and magnetic induction function are derived for plane problems of anisotropic functionally graded magneto-electro-elastic materials. Secondly, these functions are assumed in forms of polynomials in the longitudinal coordinate and can be acquired through a successive integral approach. The analytical expressions of axial force, bending moment, shear force, average electric displacement, average magnetic induction, displacements, electric potential and magnetic potential are then deduced. Thirdly, problems of functionally graded magneto-electro-elastic plane beams are considered, with integral constants being completely determinable from boundary conditions. A series of analytical solutions are thus obtained, including the solutions for beams under tension and pure bending, for cantilever beams subjected to shear force applied at the free end, and for cantilever beams subjected to uniform load. These solutions can be easily degenerated into the solutions for homogenous anisotropic magneto-electro-elastic beams. Finally, a numerical example is presented to show the application of the proposed method. 相似文献
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首先介绍电磁流量计在水厂流量测量中的应用,然后简述电磁流量计的测量原理、优点;根据性能价格比选择流量计;从安装、环境条件和流体特性等方面,论述它在安装调试、运行期的故障。最后介绍清洗探头、防雷电,抗干扰等措施的解决方法。 相似文献
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Finite element analysis of 3-D eddy currents 总被引:8,自引:0,他引:8
The authors review formulations of three-dimensional (3-D) eddy current problems in terms of various magnetic and electric potentials. The differential equations and boundary conditions are formulated to include the necessary gauging conditions and thus to ensure the uniqueness of the potentials. Different sets of potentials can be used in distinct subregions, thus facilitating an economic treatment of various types of problems. A novel technique for interfacing conducting regions with an electric vector and a magnetic scalar potential to eddy-current-free regions with a magnetic vector potential is described. Finite-element solutions to several large eddy-current problems are presented 相似文献
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A package named VECTOR for solving 3-D eddy current problems is presented. The package is a developmental version of the commercial package CARMEN and in the same way solves the vector diffusion equation, involving a modified vector potential, within conductors and the scalar Poisson equation, using a magnetic scalar potential, in non-eddy-current regions. It has been shown that this set of equations yields a unique solution for both the magnetic vector potential (and hence the currents) and the fields (which are derived from the magnetic potentials by differentiation). This package has recently been extended to solve transient problems, using simple time-stepping techniques. Some results using the package for problems with analytic solutions are given 相似文献
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Equations of motion of the magnetization vector in the nutation coil of a nuclear magnetic flowmeter
The dependence of the nutation line shape in a nuclear magnetic flowmeter on the magnetic-field inhomogeneity in the zone of nutation-coil arrangement and the time of occurrence of the magnetized liquid under the action of a radio-frequency field in the coil has been studied by experimental and theoretical methods. The obtained experimental and theoretical data are compared, and directions of investigations to come are outlined. 相似文献
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T. C. Chiam 《Acta Mechanica》1997,122(1-4):169-179
Summary This paper presents solutions of the energy equation for the boundary layer flow of an electrically conducting fluid under the influence of a constant transverse magnetic field over a linearly stretching non-isothermal flat sheet. Effects due to dissipation, stress work and heat generation are considered. Analytical solutions of the resulting linear nonhomogeneous boundary value problems, expressed in terms of Kummer's functions, are presented for the case of prescribed surface temperature as well as the case of prescribed wall heat flux, both of which are assumed to be quadratic functions of distance. The boundary value problems are also solved by direct numerical integration yielding results in excellent agreement with the analytical solutions. 相似文献
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不同介质对质量流量计的校准误差影响 总被引:1,自引:0,他引:1
随着科里奥利质量流量计广泛地运用到CNG加气机中,其计量的准确性越来越受到关注。通过运用目前最流行的有限元(FEM)软件ANSYS对管道内流体速度场进行仿真,观察到在相同质量流量下,不同介质在测量管道内具有不同的流体行为,并定性地分析了气体介质的速度场非对称特性对质量流量计校准误差的影响,最后提出了解决方案和建议。 相似文献
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基于数字锁相环的科氏质量流量计信号处理方法 总被引:2,自引:0,他引:2
针对科里奥利质量流量计信号处理中存在的问题 ,即信号频率在小范围内变化和信号易受谐波干扰 ,采用基于数字锁相环的方法处理科氏质量流量计的信息 ,跟踪信号频率的变化 ,计算相位差。对美国专利提出的方法进行了改进 ,做了仿真。仿真结果表明 ,在有谐波干扰的情况下 ,数字锁相环方法可以准确地跟踪信号频率的变化和计算相位差。本文还对计算误差进行了分析 相似文献
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Z.-Y. Lee 《Acta Mechanica》2007,193(1-2):1-16
Summary This paper deals with one-dimensional axisymmetric quasi-static coupled magnetothermoelastic problems subjected to magnetic
and vapor fields. Laplace transform and finite difference methods are used to analyze the problems. Using the Laplace transform
with respect to time, the general solutions of the governing equations are obtained in the transform domain. The solution
is obtained by using the matrix similarity transformation and inverse Laplace transform. We obtain solutions for the temperature
and thermal deformation distributions for a transient and steady state. It is demonstrated that the computational procedures
established in this paper are capable of solving the generalized magnetothermoelasticity problem of a hollow cylinder with
nonhomogeneous layers. 相似文献
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This paper presents a novel approach for obtaining boundary integral equations of 2D anisotropic magnetoelectroelasticity. This approach is based on the holomorphy theorems and the Stroh formalism and allows developing of the integral equations for the aperiodic, singly and doubly periodic problems of magnetoelectroelasticity. Obtained equations contain the unknown discontinuities of displacement, electric and magnetic potentials and also traction, electric displacement and magnetic induction that allow adopting the existing boundary element procedures for their solution. Analytical solutions for systems of collinear permeable or impermeable cracks are obtained. Numerical boundary element solutions are obtained for the singly and doubly periodic sets of permeable and impermeable cracks in the magnetoelectroelastic medium and a half-plane. Comparison with analytical solutions and other available results validate the present formulations and numerical computation. 相似文献
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A reference model is considered for a magnetic field intended for checking programs and algorithms defining the electromagnetic
field in an electromagnetic flowmeter measurement channel.
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Translated from Izmeritel’naya Tekhnika, No. 4, pp. 39–41, April, 2007. 相似文献
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The results of calibration tests on an air flowmeter instrument with a swivel plate are described. A flowmeter with changeable critical nozzles, calibrated on a test weight flowmeter instrument for gases, is used as the standard means of measurement. 相似文献