| Pulsed plasma thruster(Pulsed Plasma Thruster,PPT)has obvious advantages in microsatellite applications because of its simple structure,high reliability,flexible working parameters,accurate thrust,light weight,long life and high specific impulse under low power.At present,the failure forms of PPT in the working process are complex,including carbon deposition in the components in the discharge channel(ceramic sheet,propellant,electrode plate,spark plug),spark plug life and power supply reliability,which will affect the discharge reliability and service life of PPT,and restrict the development of PPT engineering application.At the same time,the performance of PPT varies with the working parameters of key components(including power supply system,spark plug,propellant,electrode plate,ceramic chip)and ignition times.Therefore,it is of great significance to study the influence of the working parameters of the key components of PPT on the performance of PPT,to carry out long-life ignition test,and to explore effective methods to improve propulsion performance and life.The power supply system of PPT and the principle prototype of PPT are developed.A kind of ignition power supply with high reliability,good control precision,long service life and flexible working mode is designed,as well as a charging power supply with strong anti-interference ability,low ripple coefficient and high charging efficiency.The components that make up the key components of PPT are selected and their parameters are optimized,and the integrated coupling design with other parts of PPT is carried out to form a prototype of PPT principle.The size is 200mm × 100mm × 170mm,the mass is 2650g,and the total mass of power processing unit is 249g.The ignition test of the PPT principle prototype is carried out in the vacuum environment,and the working ignition is 450000 times,which verifies the good reliability of the power supply system in the ignition process.The electromechanical model of the aerodynamic force generated by electroheating and the change of ablation quality is established.Taking the developed PPT principle prototype as the object,the simplified electromechanical model is solved by calculation method,and the simulation results are compared with the experimental results,and the effects of power supply system and its electrical parameters on the performance of PPT are obtained.The effects of key components on the propulsion performance and ignition reliability of PPT are studied by experiments.The results show that when the distance between the propellant and the spark plug is 2mm,the ignition reliability of PPT can be improved,the surface area carbon of the propellant can be reduced,and the good propulsion performance can be maintained;when the ignition voltage of the spark plug is the ignition breakdown voltage of the spark plug,the working life of the spark plug and the ignition reliability of PPT can be effectively improved,and the ignition of the spark plug does not affect the propulsion performance of PPT.The reverse connection mode of spark plug can improve the reliability of charging power supply,but it will lose part of the discharge energy and reduce the propulsion performance of PPT.The ceramic chip can effectively block the ablation of PPT discharge on the side of the propellant,and setting the ceramic piece as the front end of the propellant surface can effectively reduce the carbon deposition of the ceramic chip and improve the working life of PPT.With the increase of the ignition times of PPT,the surface shape of the propellant gradually ablated into a concave crescent shape,the impulse of the working element of PPT gradually increased and the specific impulse decreased gradually.Finally,when the number of ignition reaches 450000,the propulsion performance of PPT will gradually stabilize with the stability of the ablation shape of the propellant,and maintain good consistency.Finally,through the ignition failure phenomenon in the experiment,the cause of the failure is analyzed,and the method to improve the life of PPT is obtained.In order to optimize the design,mass,volume and performance of the thruster,a prototype of PPT and its power supply system are developed in this paper.Taking the designed PPT principle prototype and power supply system as the research object,using the methods of theoretical analysis,simulation and experiment,the electrical parameters of PPT,the propulsion distance from propellant to spark plug,the characteristics of spark plug,the connection mode of positive and negative electrode of spark plug,the influence of carbon deposition and ignition times on PPT propulsion performance and ignition reliability are obtained,which is helpful to achieve the goal of high performance and long life of PPT. |
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