Study on the Dynamic Characteristics of Bubbles of Different Sizes in the LN2 under DC Non-Uniform Electric Field

The quenching of the R-SFCLs results in the generate of a significant quantity of thermal bubbles, which will induce the breakdown of the R-SFCLs and are inherently unavoidable. The motion characteristics of the bubbles have a significant impact on the breakdown mechanism of the LN
₂
. The objective of this paper is to study the dynamic characteristics of bubbles of different sizes in the LN
₂
under DC non-uniform electric field. In the experiment, the applied voltage
U
was set as −40 kV and −60 kV. The heat flux
H
_f
was 8.9 W/cm
²
, 17.9 W/cm
²
and 27.0 W/cm
²
, separately. A high-speed camera was used to observe the dynamic characteristics of the bubbles in different electric field. The results showed that when there was no applied voltage to the bubbles, the bubbles only move upwards. With the increase of the heat flux of the heater, the deformation rate
D
r of the bubbles are nearly the same. With the applied voltage increased, the deformation rate
D
r increased in the same heat flux condition. Furthermore, the deformation rate
D
r also increased with the heat flux increased under the same electric field strength. The effect of the electric field on larger bubbles is more pronounced on smaller ones. Compare to the smaller bubbles, the larger bubbles have faster velocity in parallel to the electric field direction and larger deformation rate
D
r. The results could help to investigate the breakdown mechanism of the bubbles and LN
₂
composite systems.