Liquid dielectric

About: Liquid dielectric is a research topic. Over the lifetime, 3702 publications have been published within this topic receiving 45150 citations.

Supersaturated vapor dielectrics

Abstract: Disclosed is an apparatus which is resistant to electrical breakdown consisting of a chamber containing electrodes separated by dielectric gas supersaturated with the vapor from a dielectric liquid.

Effects of voltages with high-frequency contents on the transformer insulation properties

Abstract: This work studies the changes that occur in transformer insulation properties when voltages with steep fronts and high-frequency contents are applied. With a significant growth in the number of wind-farms and solar-plants that use power-electronic-based converters, the problems associated with such voltages on insulation has led to increasing concerns. Distorted voltages accelerate the transformer insulation degradation. Two identical transformers are studied by energizing independently under power frequency sinusoidal and width-modulated pulse trains. The dielectric characteristics of the test objects, like partial discharge activities, insulation resistance, are periodically measured during the ageing process. After a period of 500 hours of testing the dissolved gases are also analyzed. The results for both transformers are compared and discussed.

Combined aerodynamic and electrostatic atomization of dielectric liquid jets

Abstract: The electrical and atomization performance of a plane–plane charge injection atomizer using a dielectric liquid, and operating at pump pressures ranging from 15 to 35 bar corresponding to injection velocities of up to 50 m/s, is explored via low current electrical measurements, spray imaging and phase Doppler anemometry. The work is aimed at understanding the contribution of electrostatic charging relevant to typical higher pressure fuel injection systems such as those employed in the aeronautical, automotive and marine sectors. Results show that mean-specific charge increases with injection velocity significantly. The effect of electrostatic charge is advantageous at the 15–35 bar range, and an arithmetic mean diameter D 10 as low as 0.2d is achievable in the spray core and lower still in the periphery where d is the orifice diameter. Using the data available from this higher pressure system and from previous high Reynolds number systems (Shrimpton and Yule Exp Fluids 26:460–469, 1999), the promotion of primary atomization has been analysed by examining the effect that charge has on liquid jet surface and liquid jet bulk instability. The results suggest that for the low charge density Q v ~ 2 C/m3 cases under consideration here, a significant increase in primary atomization is observed due to a combination of electrical and aerodynamic forces acting on the jet surface, attributed to the significantly higher jet Weber number (We j) when compared to low injection pressure cases. Analysis of Sauter mean diameter results shows that for jets with elevated specific charge density of the order Q v ~ 6 C/m3, the jet creates droplets that a conventional turbulent jet would, but with a significantly lower power requirement. This suggests that ‘turbulent’ primary atomization, the turbulence being induced by electrical forces, may be achieved under injection pressures that would produce laminar jets.

Complex flow patterns at the onset of annular electroconvection in a dielectric liquid subjected to an arbitrary unipolar injection

Abstract: We numerically investigated the annular electroconvection that takes place in a dielectric liquid lying between two concentric cylinder electrodes. A uniform injection of arbitrary strengths either from the inner or outer cylinder introduces free charge carriers into the system, and the resulting Coulomb force induces electroconvection. The problem is characterized by a linear instability that corresponds to the onset of flow motion. The linear stability criteria were determined from direct numerical results and by linear stability analysis, and the results obtained with the two approaches show an excellent agreement. We focused on the fully developed flow pattern in the finite amplitude regime. We observed very different flow motions that were highly dependent on the injection strength.