基于DSMC/PIC方法的脉冲真空弧等离子体羽流场的理论与数值模拟研究

Plasma arc jets are widely employed in the fields of aerospace propulsion, industrial coatings, and nuclear fusion reactors, such as the developing of micro cathode arc thrusters employed in the micro satellites. In these devices, where plasma arc jets flow, the dimensions are sometimes very small and this results in the flow field being not a continuum, and the plasma jet is very rarefied, so it is often called plasma plume. In the flow-field of the plasma plume induced by pulsed vacuum arc, there are a series of complicated chemical reactions and interactions between the plume and the wall in a very short period. In order to meet the demand of the design of the pulsed vacuum arc in the future, the characteristics of the evolution and the mechanism of energy transportation of the plasma plume should be predicted very well. Thus, In order to describe the unsteady plasma plume induced by the pulsed vacuum arc, this project will study the chemical reaction models of the multi-species in the pulsed vacuum arc plasma plume based on Direct Monte Carlo method (DSMC). The interaction models of the wall effect will be built up based on probabilistic Monte Carlo method. The electrostatic model and the numerical method will be investigated for the unsteady plasma plume with the particle-in-cell (PIC) method based on the unstructured mesh. The coupled DSMC/PIC algorithm and the MPI parallel computing technology will be developed for the numerical simulation. The evolution of the three-dimensional unsteady plasma plume induced by the pulsed vacuum arc will be numerically simulated. The according test and diagnosis will be implemented to testify the numerical simulaiton. The distribution of the parameters with the variations of the time and the space in the plasma plume will be shown and the transportation characteristics of the plasma plume will be analyzed. A program for numerical simulation of the three-dimensional unsteady plasma plume induced by the pulsed vacuum arc will be provided. Therefore, the project will open a new approach for studying the unsteady plasma plume induced by the pulsed vacuum arc.

脉冲真空弧等离子体羽流在毫米量级的小尺度范围内输运，其在微秒量级的短时间内发生的一系列复杂的热化学非平衡反应和器壁相互作用是急待深化认识的瓶颈问题。为满足未来基于脉冲真空弧的高稳定等离子体器件的设计需求，亟需准确认识非稳态等离子体羽流的能量传输和演化过程。本项目研究适用于直接模拟蒙特卡罗方法（DSMC）的等离子体羽流多组分复杂化学反应模型和器壁相互作用模型，研究基于粒子模拟方法（PIC）的非结构网格等离子体静电场模型，发展多场耦合DSMC/PIC混合算法和大规模并行计算技术，实现三维脉冲真空弧等离子体羽流演化过程的数值模拟。同时有针对性地开展脉冲真空弧等离子体羽流的时空分布等实验诊断，用于约束脉冲真空弧等离子体羽流可计算模型的建立，并通过实验验证数值模拟的正确性，从而揭示脉冲真空弧等离子体羽流的时空分布演化过程和输运特性规律，形成一套基于脉冲真空弧等离子体羽流可计算模型的三维数值模拟程序。

等离子体羽流广泛存在于航天推进、工业镀膜和核反应堆等领域，为满足未来高性能高稳定等离子体器件的设计需求，提高基于脉冲真空弧的高稳定等离子体器件的工作性能，亟需正确预估等离子体羽流特性数据。本项目围绕脉冲真空弧等离子体羽流，解决了基于多场耦合的脉冲真空弧等离子体羽流场的粒子输运特性和演化规律等关键科学问题，形成了一套基于脉冲真空弧等离子体羽流可计算模型的三维数值模拟程序。取得的标志性成果如下：.基于直接模拟Monte Carlo（DSMC）方法，构建了真空弧等离子体羽流的多组分复杂化学反应模型和羽流与器壁相互作用模型，开展了离解-复合反应、电荷转移反应、壁面化学反应模型和壁面反射模型作用下的粒子分布规律研究。采用有限体积方法，构建了非结构四面体网格上泊松方程高精度计算格式，实现泊松方程多种非线性解法器，提升了泊松方程求解计算效率。基于DSMC/PIC混合程序和网格剖分技术，实现了嵌套的两套网格、双时间步长对流场和电场的耦合求解。基于区域分解和MPI并行技术，实现了DSMC/PIC并行计算的动态负载均衡算法，采用基于网格及粒子数综合权重的方法达到负载剖分的均衡，在超算平台上开展了DSMC/PIC混合程序的大规模并行计算。.基于流场/电场强耦合作用的DSMC/PIC并行程序，在超算平台上数值模拟三维非稳态脉冲真空弧等离子体羽流场，描述了脉冲真空弧等离子体羽流场中各种组分粒子的时空分布和变化规律，分析了脉冲真空弧等离子体羽流的能量传输机制，考察了各种化学反应模型、器壁作用模型对等离子体流场和电场的影响。基于脉冲真空弧羽流等离子体参数综合实验诊断平台，获得了脉冲真空弧等离子体羽流粒子密度分布、不同离子比例及能量径向分布等实验数据，通过实验验证了数值模拟结果的正确性。.本项目研究成果可用于开展三维脉冲真空弧等离子体羽流演化过程的数值模拟，为解决三维脉冲真空弧等离子体羽流问题提供了一种新的研究手段，为新型基于脉冲真空弧的高稳定等离子体器件的论证和总体设计提供了理论指导与依据。