﻿ 铁磁性舰船壳体对低频磁场屏蔽作用研究
 舰船科学技术  2023, Vol. 45 Issue (20): 62-66    DOI: 10.3404/j.issn.1672-7649.2023.20.011 PDF

Research on the shielding effect of ferromaghetic ship on low-frequercy magnetic fields
LI Guo-dong, LIU Qi, JIANG Run-xiang
College of Electrical Engineering, Naval University of Engineering, Hubei 430033, China
Abstract: In order to achieve the shaft frequency electromagnetic field in magnetic source for accurate modeling, to consider ship body own magnetic field shielding effect, therefore, in this paper, based on the theoretical calculation of the magnetic shielding factor, builds the finite element simulation model of the magnetic shielding coefficient under different frequency simulation calculation, and finally to test. The analysis results show that for the same ship shell, the magnetic shielding coefficient decreases with the increase of frequency. The shielding coefficient corresponding to 1 Hz is between 0.6 and 0.7, the shielding coefficient corresponding to 5 Hz is between 0.2 and 0.3, and the shielding coefficient corresponding to 10Hz is about 0.1, which lays a theoretical foundation for the accurate modeling of the axial frequency electromagnetic field generated by the magnetic source.
Key words: shaft-rate magnetic field     magnetic shielding     warships
0 引　言

1 舰船低频电磁场屏蔽

 图 1 轴截面示意图 Fig. 1 Schematic diagram of shaft section

 $\begin{gathered} {M_x} = {J_x}V = \frac{{\left( {\mu - 1} \right)}}{{1 + \left( {\mu - 1} \right){N_x}}}\frac{{{H_x}}}{{{L_l}}}\pi {R^2}L ，\\ {M_y} = {J_y}V = \frac{{\left( {\mu - 1} \right)}}{{1 + \left( {\mu - 1} \right){N_y}}}\frac{{{H_y}}}{{{L_s}}}\pi {R^2}L ，\\ {M_z} = {J_z}V = \frac{{\left( {\mu - 1} \right)}}{{1 + \left( {\mu - 1} \right){N_z}}}\frac{{{H_z}}}{{{L_s}}}\pi {R^2}L 。\\ \end{gathered}$ (1)

 $S = \frac{{{B_e}}}{{{B_i}}},0 < S < 1。$ (2)

 $\begin{gathered} {M_x}(f) = \frac{{\left( {\mu - 1} \right)}}{{1 + \left( {\mu - 1} \right){N_x}}}\frac{{{H_x}}}{{{L_l}}}{\text{π}} {R^2}LS(f)，\\ {M_y}(f) = \frac{{\left( {\mu - 1} \right)}}{{1 + \left( {\mu - 1} \right){N_y}}}\frac{{{H_y}}}{{{L_s}}}{\text{π}} {R^2}LS(f)，\\ {M_z}(f) = \frac{{\left( {\mu - 1} \right)}}{{1 + \left( {\mu - 1} \right){N_z}}}\frac{{{H_z}}}{{{L_s}}}{\text{π}} {R^2}LS(f) 。\\ \end{gathered}$ (3)

2 有限元数值建模方法

COMSOL软件基于边界元法（Boundary Element Method，BEM）方法计算，BEM方法以边界积分方程为数学基础，同时采用与有限元法（Finite Element Method，FEM）方法相似的划分单元离散技术。通过将边界离散为边界元，将边界积分方程离散为代数方程组，再用数值方法求解代数方程组，得到原问题边界积分方程的解。BEM的最大特点就是降低了求解问题的维数，将三维问题化为其边界面上的二维问题，只以边界变量为基本变量，域内未知量可在需要时根据边界变量求出。该方法具有较高的精度，而且在很多情况下比有限元法更有效。目前，COMSOL软件已被广泛应用于舰船腐蚀相关静态电场和磁场的建模以及ICCP系统保护电流优化和舰船电场隐身领域。

 图 2 仿真几何体 Fig. 2 Geometry of simulation software

 图 3 仿真计算的磁场屏蔽系数 Fig. 3 Magnetic field shielding coefficient calculated by simulation

3 实际测量方法

 图 4 试验布置示意图 Fig. 4 Schematic diagram of test arrangement

 图 5 磁场屏蔽前后的磁场总量测量结果 Fig. 5 Total magnetic field measurement results before and after magnetic field shielding

 图 6 实测的磁场屏蔽系数 Fig. 6 The measured magnetic shielding coefficient

4 结　语

1）根据理论模型仿真计算的磁屏蔽系数随着频率变化的变化规律与试验验证相近，证明了本文所用理论模型以及仿真计算的正确性。对于已知船型的磁场屏蔽系数，可用仿真计算代替测量，降低工程难度。

2）对于同一舰船壳体，磁屏蔽系数随着频率的增加而逐渐减小。

3）1 Hz对应的屏蔽系数在0.6～0.7之间，5 Hz对应的屏蔽系数在0.2～0.3之间，10 Hz对应的屏蔽系数为0.1左右。

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