Studies Of The Characteristics On Cascade Arc Plasma Sources

The communication black barrier problem faced by reentry spacecraft and highspeed aerospace vehicles is a frontier subject of aerospace science and technology,in order to recognize and solve this problem,it has become an important research method to construct a ground-based simulation device for plasma environment in the near space,and to conduct experimental research.The key to the ground experimental study of the black barrier problem is to generate a sub-wavelength characteristic parameter plasma with high density,low electron temperature,strong collision,and high enthalpy value,Harbin Institute of Technology "Near Space Plasma Environment Simulation and Research System" uses a cascade arc plasma source to achieve the goal.In order to more accurately simulate the real sub-wavelength plasma,and then study the physical process of the black barrier problem and its mitigation measures in the laboratory,this article will rely on the experimental platform to systematically study the working characteristics of the cascade arc plasma source.The main content is divided into the following aspects:For the interaction between the jet plasma generated by the plasma source and the downstream bluff body,we have established a mathematical and physical model to describe the non-equilibrium plasma transport process,simulated in Fluent,a computational fluid dynamics software,and study the relationship between the state of the plasma at the plasma source nozzle and the environmental factors on the coating characteristics of the bluff body.Orthogonal experiments have been used to study the influence of different plasma parameters at the plasma source nozzle,the surface temperature of the bluff body,the ambient back pressure,the maximum diameter of the bluff body and the distance from the jet inlet on the length and thickness of the effective working area of the plasma.On this basis,the key parameters that affect the coating characteristics of the plasma on the bluff body are clearly defined to provide a basis for the directional control of the plasma parameters.For the plasma parameters needed to be measured in the experiment,we construct a diagnostic system including a spectrum,Langmuir probe and image acquisition.In order to realize the spatial resolution diagnosis of the spectrum,based on the spectrum diagnostic instrument and the plasma discharge experimental platform,a twodimensional motion platform and field diaphragm for the optical fiber probe are designed.In order to realize the radial point-by-point diagnosis of plasma beam,we design and manufacture Langmuir probe,using servo motor and screw module to realize onedimensional movement of the probe,designing data generation and acquisition circuit,write Lab VIEW program,realizing probe electrical signal collection,processing and plasma parameter evaluation.In addition,in order to observe the shape and size parameters of the plasma beam,we construct an image acquisition platform.Based on the diagnosis system,the working characteristics of the cascade arc plasma source are experimentally studied,and the working gas is argon.Explore the relationship between the pressure in the plasma vacuum chamber and the intake air flow,and find the range of discharge conditions where the arc source can work normally.Under different working conditions,an arc source discharge experiment was carried out to diagnose the corresponding electron density,electron temperature and beam diameter.Analyze the effects of arc source current,vacuum chamber background pressure,inlet flow rate on electron density,electron temperature and beam diameter,and the distribution relationship of plasma parameters in the beam axis and radial to further establish their regulation of plasma parameters Regularity.In this paper,the working characteristics of the cascade arc plasma source are studied from two perspectives of numerical simulation and experimental diagnosis,the ideal working range of the plasma source is clarified,the influence relationship of different factors on the plasma parameter distribution law is established,and the different external sources are evaluated.The importance of the influence of the applied parameters on the plasma parameters provides theoretical guidance and data support for the design and optimization of the arc source and the control of the plasma parameters in the simulation of the plasma environment in the adjacent space.