Experimental and numerical simulation study of the effect for the anode positions on the discharge characteristics of 300W class low power Hall thrusters

Low-power Hall thruster(LHT) generally has poor discharge efficiency characteristics due to the large surface-to-volume ratio.Aiming to further refine and improve the performance of 300 W class LHT in terms of thrust and efficiency,and to obtain the most optimal operating point,the experimental study of the discharge characteristics for three different anode positions was conducted under the operation of various discharge voltages(100-400 V) and anode mass flow rates(0.65 mg·s-1and 0.95 mg·s-1).The experimental results indicated that the thruster has the most excellent performance in terms of thrust and efficiency etc at a channel length of 27 mm for identical operating conditions.In addition,particle in cell simulations,employed to reveal the underlying physical mechanisms,show that the ionization and acceleration zone is pushed downwards towards the channel exit as the anode moves towards the exit.At the identical operating point,when the channel length is reduced from 32 to 27 mm,the ionization and acceleration zone moves towards the exit,and the parameters such as thrust and efficiency increase due to the high ionization rate,ion number density,and axial electric field.When the channel length is further moved to 24 mm,the parameters in terms of thrust(F) and efficiency(ηa) are reduced as a result of the decreasing ionization efficiency(ηm) and the larger plume divergence angle(α).In this paper,the results indicated that an optimum anode position(ΔL=27 mm) exists for the optimum performance.

Investigation into the thermal effect of the LIPS-200 ion thruster plume

The distribution of the thermal effects of the ion thruster plume are essential for estimating the influence of the thruster plume, improving the layout of the spacecraft, and for the thermal shielding of critical sensitive components. In order to obtain the heat flow distribution in the plume of the LIPS-200 xenon ion thruster, an experimental study of the thermal effects of the plume has been conducted in this work,with a total heat flow sensor and a radiant heat flow sensor over an axial distance of 0.5–0.9 m and a thruster angle of 0°–60°. Combined with a Faraday probe and a retarding potential analyzer, the thermal accommodation coefficient of the sensor surface in the plume is available. The results of the experiment show that the xenon ion thruster plume heat flow is mainly concentrated within a range of15°. The total and radial heat flow of the plume downstream of the thruster gradually decreases along the axial and radial directions, with the corresponding values of 11.78 k W m^(-2) and 0.3 k W m^(-2) for the axial 0.5 m position, respectively. At the same position, the radiation heat flow accounts for a very small part of the total heat flow, approximately 3%–5%. The thermal accommodation factor is0.72–0.99 over the measured region. Furthermore, the PIC and DSMC methods based on the Maxwell thermal accommodation coefficient model(EX-PWS) show a maximum error of 28.6% between simulation and experiment for LIPS-200 ion thruster plume heat flow, which, on the one hand, provides an experimental basis for studying the interaction between the ion thruster and the spacecraft, and on the other hand provides optimization of the ion thruster plume simulation model.

The far-field plasma characteristics of LHT40 low-power Hall thruster for commercial aerospace applications

To achieve a better insight into the far-field plasma spatial distribution and evolution characteristics of the 300 W class low-power Hall thruster(LHT)for commercial aerospace applications,a dedicated and integrated plasma diagnostic system composed of seventeen Faraday cups(FC)and two triple Langmuir probes(TLP)is established to investigate the timeaveraged in situ spatial distribution characteristics of far-field ions and electrons.The ion current density(ICD),plasma potential,plasma density,and electron temperature at 1000 mm downstream of 300 W class LHT for commercial aerospace applications in the azimuthal angle range of-90°to 90°were investigated under the conditions of different anode mass flow rates and discharge voltages.The results demonstrated that ICD,beam divergence angle,and mass utilization efficiency increased with increasing anode mass rate.The double-wings phenomenon was observed in the spatial distribution of ICD at large angles from the thruster axis,which is attributed to charge exchange collisions at increasing vacuum backpressure.The plasma electron temperature,electron density,and plasma potential parameters derived from the TLP decreased rapidly in the angle range from 0°to 30°and did not exhibit significant variations above 30°,which was also in good agreement with the results of the measured divergence angle of the FC.The discrepancy of average ion speed was calculated.The maximum error is better than 31.5%which checks the consistency between the TLP’s results and that of FC to some extent.

超临界CO2萃取檀香精油工艺研究

为了探讨利用超临界CO2萃取法提取檀香精油的工艺,以初步确认最适合用于檀香精油萃取的工艺条件。文章以檀香精油的提取率作为考察指标,采用单因素和重复性验证实验方法,考察萃取时间、萃取压力、萃取温度以及药材是否浸泡等因素对超临界CO2萃取檀香精油提取率的影响。结果显示,该工艺具有操作简便、快速、提取率高等特点,是提取檀香精油的有效方法。