Study On Flow Characteristics Of Arc-Heated Plasma Thrusters Jet

Arc-heated plasma thrusters have been applied to satellite station-keeping, and have many other potential applications in space propulsion. In the arc-heated plasma thruster, gaseous propellant is heated by a DC electric arc to a temperature of about 20000 K, and the hot plasma is subsequently expanded through a convergent-divergent nozzle, in which the gas’s internal energy is converted into the kinetic energy of an axially-exhausting supersonic jet and thereby generates a thrust force. In this paper, the flow characteristics of arc-heated plasma thruster jet are studied by the method of combining theoretical analysis and numerical simulation. The experimental method is used to study the erosion of the nozzle.(1) In this thesis, three kinds of turbulence models (the standard k-ε model, the standard k-ω model and SST k-ω model) are applied to the numerical simulation of the plasma jet, and the calculated results are compared with the experimental results. It is found that the results of the calculation are different from the experimental results when using the standard k-ε model or the standard k-ω model, while using the SST k-ω model is in good agreement with the experimental results. Compared with the standard k-ε model and the standard k-ωmodel, the SST k-ω model is more suitable for numerical simulation of arc-heated plasma thruster jet.(2) As for the self-designed arc-heated plasma thruster, the influence of working current, propellant and anode structure to arc-heated plasma thruster performance are discussed using the method of numerical simulation. The results of the study are as follows:Working current has a great effect on the flow field of arc-heated plasma thruster jet. The current strength directly determines the current density inside the arc-heated plasma thruster, which affects the Joule heat. The increase of the current can significantly increase the plasma temperature and velocity. Meanwhile, the volt-ampere characteristics of the self-designed arc-heated plasma thruster are increased in the current range of the study.Due to differences in the electric conductivity, the operating characteristics of different propellants arc-heated plasma thruster are different. When the working current is 150A, the arc voltage value relationship of the three propulsion arc-heated plasma thruster is: UH2>UN2>UAr, which also means that, in the same working current, the arc-heated plasma thruster power relations as follows:PH2>PN2>PAr.Differences in arc-heated plasma thruster power also ultimately affect the temperature distribution. The temperature of the arc-heated thruster also exhibits the same relationship:TH2>TN2>TAr.The velocity distribution of the central axis of the arc-heated plasma thruster begins to show more obvious difference from the anode throat position due to the influence of the temperature distribution.In the case of the same anode contraction angle and throat length, with the increase of throat diameter, the current density on the arc-heated plasma thruster axis is reduced, and the arc voltage is increased, and the highest temperature and the maximum velocity of the plasma on the arc-heated plasma thruster axis are decreased. Moreover, the influence of throat diameter on the volt-ampere characteristics and plasma jet characteristics of the arc-heated plasma thruster is very obvious. However, the influence of throat length and anode contraction angle on the volt-ampere characteristics and plasma jet characteristics of the arc-heated plasma thruster is negligible.(3) By improving the structure of the arc-heated plasma thruster, the thruster cooling efficiency is improved, effectively prevent the anode ablation, Thus the service life of the anode nozzle is extended. The experimental results showed that the anode ablation mainly concentrated in the anode throat and the expansion section for plasma thrusters with anode throat diameter of 2mm. When the throat diameter is 4mm, the anode ablation mainly concentrated around the outlet of the nozzle, and the amount of the ablation is increased.The research of this paper can provide the theoretical foundation for the numerical simulation and application of the arc-heated plasma thruster.