亚大气压六相交流电弧等离子体射流特性研究:实验测量

Characteristics of meso-pressure six-phase alternative current arc discharge plasma jet: Experiments

以临近空间高超声速飞行器以及航天器再入大气环境飞行过程"黑障"问题的研究为背景,进行了多相交流电弧放电实验装置的物理设计,建立了六相交流电弧等离子体实验平台(MPX-2015),在背景压力为500 Pa的亚大气压条件下获得了最大直径和长度分别达到14.0 cm和60.0 cm的等离子体射流.研究了工作气体流量、真空腔压强、电极间距以及弧电流等因素对等离子体自由射流和冲击射流特性的影响规律.结果表明:在实验参数范围内,真空腔压强对等离子体的射流特性影响最为显著,等离子体自由射流的长度和直径以及冲击钝体条件下的鞘套有效工作长度和厚度均随着压强的降低而增大;提高沿电极环缝注入的工作气体流量或弧电流亦有利于等离子体鞘套尺寸的增加.上述工作有助于进一步开展临近空间飞行器与其周围复杂介质环境间复杂的气动热效应和"黑障"问题的研究.

During the re-entry process of a supersonic vehicle in near space, the interaction between the flying vehicle and surrounding air is violent due to the hypersonic relative speed.As a consequence, the shock-heated air in the vicinity of the vehicle surface is ionized.Thus, the formed plasma layer operates in strong collision, non-uniform and nonequilibrium states.One of the serious system operation problems resulting from this non-equilibrium plasma layer is the so-called communication blackout.Physical simulation of the near-space plasma environment in laboratory based on various plasma sources is a much lower cost method than the in-situ measurements in the vehicle re-entry process.In this paper, based on the ideas for designing the dual jet direct current arc plasma and the muti-phase alternating current discharge plasma, a physical design on the multi-phase alternating discharge apparatus is proposed for generating a large volume plasma arc-jet.And a multi-phase gas discharge plasma experimental platform-2015（MPX-2015） is established with the image recording/processing, electrical and optical emission spectroscopy measurement system in this laboratory. The preliminary experimental observations show that under a typical operating condition with a 500 Pa background pressure, a large volume plasma jet with a maximum diameter of 14.0 cm and a maximum length of 60.0 cm is obtained on this newly developed platform.The influences of the gas flow rate, the chamber pressure, the electrode gap spacing and the arc current on the characteristics of the plasma free jet and impinging jet are also studied.The experimental results show that within the parameter ranges studied in this paper, the chamber pressure has a very significant influence on the size of the plasma jet, i.e., both the diameter and length of the plasma free jet increase with chamber pressure decreasing, and a similar variation trend is also observed for the thickness and length of the plasma layer surrounding a bluff body.In addition, the size of the plasma layer also increases with the increase of the plasma working gas flowrate and the discharge current.These results are helpful in the more in-depth investigating of the aerodynamic heat effect and blackout issue of the re-entry process of supersonic vehicle in near space in future.In the future research, we will modify the structures of the plasma generators in order to obtain supersonic plasma arc-jets, and study both the quasi-steady and transient characteristics of the arc plasmas, as well as the strong interactions among the plasma jet, the surrounding air and the solid bluff body.