Study On Calculation Of Plasma Characteristic And Performance Simulation In Pulsed Plasma Thruster

Pulsed plasma thruster(PPT)has characteristic of high specific impulse,small volume,light weight and obvious advantages in the application of micro satellite,is expected to become the first propulsion system of micro satellite.But its low thrust efficiency and other shortcomings limit its function.The plasma properties not only affect the electrical parameters of PPT,but also affect the impulse and ablation quality parameters.The study of plasma can further explore the working mechanism of PPT.At the same time,studies have shown that improvement of PPT electrode configuration and capacitance selection and reasonable layout can effectively improve the efficiency of PPT.Therefore,in this paper,the plasma characteristics of PPT discharge channel is studied.On this basis,the PPT performance simulation of variable structure is carried out.Based on the theory of emission spectra,the spectral intensity in PPT process is measured and the electron temperature and electron density of the plasma in the PPT discharge channel are calculated.The electron temperature is calculated by Boltzmann slope method and the calculation method is improved.It is proved that the wavelength of 588.977 nm can not be used for calculation because it does not accord with the Local thermodynamic equilibrium.Only three wavelengths with large energy difference can get accurate temperature results.The electron density was calculated by the density function of the Stark broadening of the spectral line.The broadening mechanism was considered during the calculation,and the influence of the pulse width of the instrument was evaluated,and the double peak near the wavelength of 658 nm was considered.The evolution of the plasma characteristics in the PPT discharge channel with ti me and space was obtained by setting the threshold voltage,and the variation of the plasma characteristics was obtained.The results show that electron temperature is decreasing and electron density has 2-3 peaks in a single discharge.In different space,temperature has little change,energy loss is small,and density with the plasma out and drop out,close to the wall at the maximum density.The effects of structural changes on the performance of PPT were also investigated.Based on the traditional electromechanical model,the new modified model of PPT for different structures was proposed by using the variation law of the plasma characteristics.The new model takes into account the effects of magnetic field in multiple directions,improves the inductance model under variable magnetic field,and the resistance model and the ablation model under variable structure for the flared tongue shaped structure and the bevel ablation structure.The accuracy of the new model is verified by comparing the simulation results of the prototype and the German ADD SIMP-LEX prototype.Based on the improved model,the performance simulation of the prototype was carried out,and the performance comparison results were obtained under different conditions.It was proved that the best performance of the flared tongue shaped structure was obtained,and the reasonable selection of the capacitor and the increase of the ablation area could improve the performance of PPT effectively.The factors influencing the performance of PPT were discussed from the view of simulation,and the improved method of laboratory prototype was put forward,which could help to design high performance PPT.