Precise Control of Characterization of a Low-Pressure Plasma Jet by Applying the Magnetic Field

迄今为止，等离子体射流已广泛应用于焊接、切割、固体废物处理、等离子体喷涂、粉末合成等冶金和化工过程，以及MHD发电机、航天器推进等能量转换系统。在这些过程和能量转换系统中，不仅要精确控制气体的温度和速度特性，而且要精确控制等离子体的参数，如电子和离子的能量和密度。那么，等离子体射流的这些特性实际上可以通过输入功率、频率、气体成分和流量、腔室压力和外加电磁场等外部操作参数来控制。在这些参数中，施加磁场可能是在清洁和稳定的条件下精确控制等离子体射流宏观和微观特征的最有效方法之一。也就是说，成功的等离子体控制将带来高质量的过程控制和能量转换效率的提高。本文研究了强反射型磁场对管道内低压氩等离子体射流的热流体特性和等离子体参数的影响。本文的主要结果总结如下：1。由于磁压缩和径向洛伦兹力的作用，等离子体射流向更远的下游延伸了相当大的磁场强度。在射流核心区附近，电离程度最高，由于焦耳加热，气体温度随磁场强度的增加而略有上升。电子数密度随核心区磁场强度的增大而增大，其中电子温度和电子数密度的径向梯度变得陡峭，这是由于电子向喷流核心方向的磁约束。离子激发温度比原子激发温度大。在磁芯区，由于主动激励的作用，随磁场强度的增大，磁芯区磁场强度增大的速度更快。少

Plasma jet has been frequently utilized in the metallurgical and chemical processes, such as welding, cutting, solid waste processing, plasma spraying and powder synthesis and further energy conversion systems such as MHD generator and space craft propulsion so far. In these processes and energy conversion systems, it is very important to control precisely not only the characteristics of gas temperature and velocity but also the plasma parameters such as the energies and densities of electrons and ions.Then these characteristics of plasma jet, in fact, can be controlled by the external operated parameters of the input electric power, the frequency, gas compositions and flow rate, chamber pressure and applied electromagnetic field. Among these parameters, applying magnetic field may be one of the most effective methods to control precisely both the macroscopic and microscopic characterizations of plasma jet under the clean and stable conditions. That is, successful plasma control would … More result in the high quality process control and increase of the energy conversion efficiency.The present report describes the effect of the strong mirror type magnetic field on the thermal-fluid characteristics and also plasma parameters of a low-pressure argon plasma jet in the pipe.The main results obtained here are summarized as follows1. The plasma jet extends to the farther downstream considerably with the magnetic field strength due to the magnetic compression and the Lorentz force in the radial direction. Around the core region of the jet, of which the degree of ionization is the highest, the gas temperature rises a little with the magnetic field strength due to the Joule heating.2. The electron number density increases with the magnetic field strength in the core region, in which the radial gradients of electron temperature and electron number density become steep, due to the magnetic confinement of electrons toward the core of the jet.3. The ionic excited temperature is larger than the atomic one. And it increases more rapidly in the core region with the magnetic field strength due to the active excitation. Less