Dielectric breakdown properties of Al-air mixtures

In order to investigate the influence of aluminum vapor on the breakdown performance of air, this paper makes a study of the dielectric breakdown characteristics of Al-air mixture in the temperature range of 300–5000 K at atmospheric pressure. A Boltzmann analysis method is used to deal with the electron energy distribution function (EEDF), the reduced ionization coefficients (α/N), the reduced attachment coefficients (η/N) and the critical reduced breakdown strength ((E/N)_cr) so as to explore the influence of temperature and mixing ratio on the dielectric breakdown properties. In the temperature range of 300–2000 K, the property of the mixture is mainly determined by the mixing proportion of aluminum vapor because the composition of particles remains unchanged. In the temperature range of 2000–2500 K, the decomposition of Al₂O₂ leads to the increase of aluminum oxides and NO, and a rise in the percentage of high-energy electrons as well as the increment of α/N. Also, the joint action of O₂ and NO makes η/N increase first and then decrease, and (E/N)_cr goes down to a smaller temperature range. An increase in the proportion of aluminum vapor causes (E/N)_cr to decrease in the low-temperature region and to increase in the high-temperature region, which will reduce the transition between these two temperature regions.