基于解析法的电磁发射弹丸内膛磁场分布特性分析

电磁轨道发射装置膛内的磁场分布特性对制导弹丸的器件布局设计非常重要。对电磁轨道发射装置膛内的强磁场环境进行了分析，基于毕奥-萨伐尔定律推导了考虑弹丸运动位移和电流趋肤深度下膛内磁场的计算公式。通过时谐分析方法并采用数据拟合的方式得到了电感梯度与电流频率和弹丸运动位移的函数关系，用以分析弹丸的内弹道运动特性。采用时频分析方法得到了电流趋肤深度随时间的变化关系，从而建立了弹丸中轴线磁场分布特性求解的三维解析计算模型。以实验室的电磁发射装置为例，采用试验电流数据作为输入，对内膛弹丸处磁场分布特性进行解析计算。结果表明：弹丸中轴线的磁感应频率在450 Hz以下，磁感应强度峰值达到0.4 T，并沿弹丸长度方向迅速衰减，100 mm处的磁场基本降为0. 利用磁探针的测试数据验证了理论计算模型的正确性。

Analysis of Distribution Characteristics of In-bore Magnetic Field of Electromagnetically Launched Projectile Based on Analytical Method

The in-bore magnetic field distribution characteristics of electromagnetic launcher should be considered in the layout design of components in guided projectile. The high in-bore magnetic field generated by electromagnetic launcher is analyzed, and a formula for magnetic field distribution is deduced based on Biot-Savart law, in which projectile displacement and current skin depth are considered. The relationship between inductance gradient, current frequency and projectile’s location is obtained by time-harmonic analysis and data fitting to analyze the in-bore kinetic characteristics of projectile interior trajectory. And the time-frequency analysis method is used to achieve the relationship between current skin depth and time to build a 3-D theoretical calculation model (TCM) for the distribution characteristics of magnetic field along the central axis of projectile. A laboratory electromagnetic launcher is taken for example, and the experimental data is used as input for simulation. The results show that the in-bore magnetic induction intensity frequency is below 450 Hz and the peak of in-bore magnetic induction intensity is up to 0.4 T, which gets weaker along the length direction of projectile and approximates to 0 at 100 mm. The validity of TCM is verified by using the experimental data of magnetic probe.