Abstract:

To investigate the polarization dynamic characteristics of bubbles under a non-uniform electric field, the evolution and dispersion of bubbles in heptane solution are visualized by using high-speed photography. Combined with dimensionless numbers, the effects of gas flow and applied voltage on bubble characteristics and the bubble motion law dominated by polarization force are discussed. The results show that increasing the electric field strength can significantly reduce the growth period and size of the bubbles, and accelerate their generation frequency. Under the action of a weak electric field, the bubble motion is dominated by hydrodynamics and influenced by the wake induction, as the height of its trajectory decreases as the Bo_E increases. In contrast, the effects of a strong electric field cause the bubble movement to be first dominated by the polarization force and exhibits electrohydrodynamic (EHD) properties, and the bubble trajectory extends upward with increasing Bo_E. However, with the vertical decay of the electric field intensity and the influence of the liquid phase resistance, the velocity of the bubbles decreases continuously. When the bubbles leave the region dominated by the polarization force, their motion again exhibits hydrodynamic characteristics, then the bubbles disperse in the liquid phase impacting by the bubble wake and interactions between bubbles.

Key words: gas-liquid two-phase flow, DC electric field, polarization force, conductivity, bubble diameter, bubble trajectory

摘要：

为探讨电场作用下气泡在低电导率工质中的极化运动特性，采用高速数码摄像技术对气泡在正庚烷溶液中的生长和分散过程进行了可视化研究，并结合无量纲数分析了不同气体流量和施加电压下的气泡演变特征以及极化力主导的气泡运动规律。结果表明，增大电场强度可导致气泡生长周期缩短，气泡尺寸显著减小，产生频率加快。在低电场强度下，气泡运动主要表现为流体动力学特性；而在强电场作用下，气泡首先受极化力主导而表现为电流体动力学特性，其直线轨迹高度随Bo_E增大而增大。但随着电场强度在竖直方向上的衰减以及液相阻力影响，气泡运动速度不断减小；当气泡脱离极化力主导区域后，其运动再次表现为流体动力学特性，受尾迹诱导和气泡间相互作用影响，气泡在竖直方向上沿毛细管轴向四周扩散。

关键词: 气液两相流, 直流电场, 极化力, 电导率, 脱离直径, 气泡轨迹