Electric aircraft has become a major development trend in the future aviation industry due to its advantages of low carbon and environmental protection. The air insulation of electric aircraft needs to withstand high-frequency voltage in high altitude. Therefore, this paper qualitatively studies the air discharge characteristics and microscopic mechanisms between needle-plate electrodes under different pulse voltage parameters and different humidity in the low temperature sub-atmospheric pressure environment of high altitude through simulation and experimentation.
Firstly, the pulse power supply was built by a 4-stage half-bridge Marx circuit. Then, the two-dimensional axisymmetric streamer discharge model of low-temperature sub atmospheric air was built, and three sets of Helmholtz equations were coupled to calculate the photoionization. Finally, the images of air streamer discharge under different conditions were captured by intensified charge coupled device (ICCD).
The following conclusions are drawn through simulation and experiment under the condition of low temperature and sub-atmospheric pressure: (1) The simulation outcomes reveal that when the reduced electric field strength remains the same, as the altitude increases, the breakdown voltage drops, the electron density gradually reduces, the electric field strength of the streamer head decreases, and the development speed of the streamer slows down. As the rising edge of the pulse grows, the electron density decreases simultaneously. When the discharge can be accomplished within one pulse, an increase in the pulse width has minimal effect on the discharge. Under the circumstances of low temperature and sub-atmospheric pressure, with the rise in humidity, the electron density increases concurrently, the peak value of the electric field intensity also rises, and the development speed of the streamer becomes faster. (2) The experimental results indicate that when the reduced electric field strength is consistent, with the increase of altitude, the penetration time of the streamer becomes longer, the channel brightness decreases, and the channel radius increases. When the pulse width of the pulse voltage is greater than the discharge time, the increase in the pulse width has no influence on the discharge process; when the frequency of the pulse voltage rises, the brightness of the streamer channel gradually intensifies; under the condition of low temperature and sub-atmospheric pressure, with the increase in humidity, the penetration time of the streamer becomes shorter and the brightness of the streamer channel increases. (3) Under the same conditions, the simulation and experimental results have a consistent conclusion regarding the development speed of the streamer. The influence of the pulse width on the discharge depends on whether the discharge can be completed within one pulse. The brightness of the streamer channel is positively correlated with the electric field intensity of the streamer head.