| The deviation of Hall thruster’s temperature from cold state to thermal steady state is more than 300 °C. When it is equipped on the satellite platform, the thruster performance parameters may create a certain offset compared to that on the ground. The hot stack generated by the magnetic circuit components can influence the magnetic field distribution within the discharge channel, thereby changing the performance of thruster.The commercial software ANSYS is used to simulate temperature changes of the magnetic circuit elements during Hall thruster operation. The simulation results of thruster temperature distribution at each position are obtained. The temperature change of magnetic screen within 100 min is measured. It shows that when the temperature is stable, the temperature of the magnetic shield increases by300°C. The simulation analysis of solar radiation on the thruster temperature is carried out. The result shows that when the sun exposure on the front of the thruster, the temperature rise of components in the thruster is more than 10 °C except the inner and outer ceramic components; and when the sun exposure on the back side of the thruster, the temperature difference between the front side and back side of the thruster is 10 °C.By the Direct Simulation Monte Carlo method, the plasma density and spatial potential under corresponding conditions were computed. The results show that the magnetic field affects the axial position of the ionization region within the channel, the spatial distribution of electric potential and electron temperature, thereby changing the efficiency of the thruster. Variable temperature experiments of the soft magnetic material DT4 C was designed to obtain the relationship between magnetic field strength and magnetic flux density of DT4 C at each segments temperature from 20 ℃ to 500 ℃. Seen from the graph, when the magnetic field strength falls between 300 A/m and 500 A/m, DT4 C permeability tends to decrease. When the magnetic field strength is greater than300 A/m, the permeability of the specimen reduces first then increases further and finally decreases. The two-dimensional magnetic field simulation of thruster is simulated. The max magnetic induction in the thruster discharge channel at high temperature declines by about 15%, and the position of zero magnetic field extends outward about 2.3 mm, when compared with normal temperature case.The method for monitoring the change of magnetic field strength on-line is proposed. The results show that when the excitation coil in series manner is adopted, magnetic field strength decreases with an increase in the coil inductance.When the inductance is small, magnetic field strength relates inversely proportional to the inductance. When the inductance increases, the rate of decline in the magnetic field strength goes faster. By measuring inductance value of the external field coils, the change of the magnetic field in the discharge channel is predicted in order to facilitate the thruster operating point regulator back to the previous state.The temperature change of each part in the thruster within 90 min is monitored. After reaching thermal equilibrium, the measuring point temperature and the performance parameters of thruster are measured. The results show that the discharge current increases; the thrust reduces; the specific impulse changes from2442 s to 2317 s, and efficiency also decreases. The working performance of thruster is stable within 100 minutes after optimization of excitation. |
PDF Full Text Request