Analysis of Electrohydrodynamic Effect and Development of New Fluid Devices

在高压直流电场作用于某些绝缘油时，由于电流体动力学（EHD）效应，正极产生了速度约为1ms^<-1>的射流。在这个过程中，电能直接转化为流体的动能。本研究的目的是分析射流和开发新的流体装置。讨论了EHD射流的流态与容器几何形状、电极排列、场强和流体性质的关系。在给定场强下，射流速度随流体电导率和粘度的降低而增加，这一发现为良好工质的配制提供了一种方法。通过控制射流的方向和速度，可以设计出介电流体马达、喷墨喷嘴、微泵和电流变（ER）装置等新型流体装置。流体马达仅由电极、转子和工作流体组成。由于不需要磁场，电介质流体电机具有各种优点。例如，使用柔性和轻质材料的电机是可能的，这可以用于构建软微机械。在高直流电场的作用下，界面上产生了额外的应力，从而导致自由表面从喷嘴出口开始持续演化。研制了由针电极和毛细管组成的无压电换能器喷墨装置。在电场作用下，夹在电极上的流体粘度增加。电流变效应适用于离合器和减震器等机械装置，因为局部流动性是主动控制的。EHD射流在新型流体装置中具有很好的应用前景。

On the application of high DC electric fields to some insulating oils, a fiuidjet with a velocity of about 1ms^<-1> is generatedfromthepositive electrode due to electrohydrodynamic(EHD) effect. In this process, the electric energy is directly converted to kinetic energy of the fluid. The purpose of this study is the analysis of jet flow and development of new fluid devices. The flow patterns of EHD jet is discussed in relation to the geometry of vessel, electrode arrangement, field strength, and fluid properties. The speed of jet flow at a given field strength increases with decreasing electric conductivity and viscosity of fluid This finding provides a formulation method of good working fluids. By controlling the direction and speed of jet flow, new fluid devies are designed such as dielectric fluid motors, inkjet nozzles, micropumps, and elerctrorheological(ER) devices. The fluid motors simply consist of electrodes, rotor, and working fluids. Since the magnetic fields are not required, the dielectric fluid motors have various kinds of advantages. For example, the motors by the use of flexible and light materials are possible and this can serve to construct soft micromachine. When subjected to high DC fields, the extra stresses across the interfaces are induced and the continuous evolution of free surface from the nozzle exit can take place. The inkjet units consisting of needle electrode and capillary are developed without piezoelectric transducers. The fluids which are sandwiched in electrodes with flocked fabrics show viscosity increase under electric fields. The ER effects are applicable to mechanical devices such as clutch and shock absorber because the local fluidity is actively controlled. The EHD jets are very attractive in application to new fluid devices.