Electric effects on the rheology of insulating oils in electrodes with flocked fabric
Electric effects on the rheology of insulating oils in electrodes with flocked fabric
复制标题
植绒织物电极中绝缘油流变性的电效应
DOI：
10.1007/s003970050163
复制
发表时间：
1999
期刊：
影响因子：
2.3
通讯作者：
K. Edamura
中科院分区：
文献类型：
--
作者：
Y. Otsubo;K. Edamura
研究了绝缘油在非均匀电场中的流变行为，该电场由植绒织物覆盖的电极产生。虽然在表面光滑的金属电极之间的均匀电场中，油没有表现出电流变效应，但植绒织物在稳定剪切时导致粘度显著增加。随着油的零场粘度和导电率的降低，粘度的提高幅度增大。在零剪切速率极限下，低电导率的原油表现为具有屈服应力的固体。在没有剪切作用的情况下，将极少量的微粒引入带电油液中，可以观察到微粒在纤维尖端和平板电极之间的快速而大规模的运动。流体在强电场中的局部运动称为电流体动力对流。在静态油中形成循环流动的周期模式。在循环运动过程中耗散的电能有助于保持静止油液中的周期性流动。当应力很低时，周期图案不会被分解。屈服应力对应于破坏EHD对流的磁区结构所需的力。在切变场中，可能需要额外的能量来改变EHD对流的周期模式。定常剪切粘度的显著增加可归因于EHD对流和外部剪切的相互作用。
The rheological behavior of insulating oils is studied in nonuniform electric fields which are generated by an electrode covered with flocked fabric. Although the oils show no electrorheological effects in uniform fields between metal electrodes with smooth surfaces, the flocked fabric leads to a striking increase of viscosity in steady shear. The viscosity enhancement increases with decreasing zero-field viscosity and decreasing conductivity of oils. In the limit of zero shear rate, the oils with low conductivity behave as solids with yield stress. When a very small quantity of fine particles is introduced into electrified oils without shear, a rapid and large-scale motion of particles is observed between the tips of fibers and the plate electrode. The local motion of fluids in high electric fields is referred to as electrohydrodynamic (EHD) convection. Periodic patterns of circulation flow are formed in static oils. The electric energy which is dissipated during the circulation motion contributes to holding the periodic flow in static oils. When the stress is very low, the periodic patterns are not broken down. The yield stress corresponds to the force required to rupture the domain structures of EHD convection. In shear fields, the additional energy may be required to change the periodic patterns of EHD convection. The striking increase of viscosity in steady shear can be attributed to the interactions between EHD convection and external shear.