EHD behavior of nitrogen bubbles in DC electric fields

The deformation of nitrogen bubbles injected into transformer oil with various DC electric fields was studied experimentally and theoretically. The bubble deformation was visualized by a high speed camera. The major axis of the bubble was elongated along the direction parallel to the electric field, with the elongation increasing as the electric field strength was raised. The electrical Weber number (We) was used to correlate the electric field strength and the dielectric permittivity of the working fluid to the bubble relative aspect ratio (AR(e)/ AR(o)). The experimental results show that the relative aspect ratio increases with increasing We. The electric stresses were calculated on an actual bubble shape including the electrostriction stresses to analyze the bubble elongation. (c) 2007 Elsevier Inc. All rights reserved.