磁喷管中带电粒子加速、分离和磁反馈机制研究

Similar to the flow acceleration in the de Laval nozzle, the convergent-divergent magnetic nozzle can also accelerate charged particles/plasmas and convert either thermal or non-directional energy into directional kinetic energy. The mechanism of the magnetic nozzle has been reflected in the thermonuclear reaction, fluid control, electromagnetic propulsion etc. At present, the research of the magnetic field confinement, energy conversion and other aspects of problems have been described, whereas the agreement on the viewpoints about the charged particles detachment and the mechanism of the acceleration has not been reached..This research will establish math-physical model of magnetic nozzle based upon particle dynamics. Adopting PIC-MCC method, the acceleration and detachment process of charged particles and the magnetic feedback phenomenon will be simulated. The research emphases are put on electromagnetic interaction and energy conversion mechanism. The purpose of this research is to clarify main factors influencing the performance of magnetic nozzles and the critical condition of magnetic feedback. In the end the research is expected to explain these three most interesting questions: (1) particle detachment conditions and position on the magnetic lines, (2) the ambipolar electric field developed as a result of velocity differences between particles and the magnetic feedback effect of the field, and (3) the influences of particle collisions. This research is expected to provide useful guidance on the optimization of magnetic nozzles and the improvements of energy conversion efficiency.

类似于固体壁面的拉瓦尔喷管气流加速，附加磁场收缩-扩张型磁力线构成的磁喷管同样可以加速带电粒子/等离子体，并在装置内进行能量转换，其工作机制体现在热核反应、流体控制和电磁推进等热点装置中。虽然已有关于磁喷管磁场约束和能量转化等方面的物理问题描述，但非固体壁面磁力线边界的带电粒子分离与加速机制尚未有一致结论。. 研究将建立基于粒子动力学的磁喷管数学物理模型，采用PIC/MCC方法，仿真磁喷管中带电粒子的加速、分离过程和磁反馈现象；重点定量研究电磁作用机制与能量转化内在机理；进一步与MHD方法磁喷管仿真结果进行对比；明确影响磁喷管效应的主要因素，得到磁喷管工作效率和磁反馈阈值条件；最终解释最令人感兴趣的三个问题：粒子在磁力线上的分离条件和位置、粒子运动速度差异导致双极电场产生的磁反馈效果和粒子之间碰撞效应及影响，为磁喷管的设计优化和能量转化效率提升提供有益参考。

类似于固体壁面的拉瓦尔喷管气流加速，附加磁场收缩-扩张型磁力线构成的磁喷管同样可以加速带电粒子/等离子体，并在装置内进行能量转换，其工作机制体现在热核反应、流体控制和电磁推进等热点装置中。虽然已有关于磁喷管磁场约束和能量转化等方面的物理问题描述，但非固体壁面磁力线边界的带电粒子分离与加速机制尚未有一致结论。.本研究建立了基于粒子动力学的磁喷管数学物理模型，采用PIC/MCC方法首次建立了轴对称的磁喷管全粒子模拟程序，仿真磁喷管中带电粒子的加速、分离过程和磁反馈现象；重点定量研究电磁作用机制与能量转化内在机理；明确影响磁喷管效应的主要因素，得到磁喷管工作效率和磁反馈阈值条件；最终得到了磁喷管中离子加速的动力学来源及其相应的比例，发现电热加速机制的贡献超过2/3。探索了不同入口参数分布对磁喷管内能量转化效率的影响，发现在满足电子磁化的前提下，较低的磁场和集中型分布的入口达到更高的能量转化效率，最高可达65%。明晰了带电粒子从磁场中分离和保障电流回路闭合的机理及其占比，发现电子分离的主导机制是惯性分离，而在束流下游边缘，电子粘性造成的分离快速增大。明确了磁喷管中磁反馈的源头是感应电流，以及感应电流的四种驱动机制及其与等离子体空间参数分布的内在联系。.通过对磁喷管中上述机制的探索，得到的规律可以为将来热核反应中等离子体的流动控制、空间电磁推力器的原理认知和性能优化提供有益的帮助。