Investigation On Characteristics Of Modes And Electro-field In Electrohydrodynamics(EHD) Atomization With Capillary

Electrohydrodynamics(EHD) atomization could obtain many monodispersed tiny droplets with different scales, and the electrostatic spray pattern, size and trajectory of droplet could be changed by adjusting electrical filed. EHD atomization could be applied into many industrial fields. Due to complicated electrical and flow field, it is difficult to establish an ideal physical model to describe the EHD. It is vey important to further investigate the EHD through the theoretical, experimental and numerical methods for its application. In this paper, EHD atomization with capillary was experimentally studied. The droplet pulsation, separation frequency and EHD atomization modes are studied. The space electric field formed by single, double and three capillary electrodes are analyzed and numerically calculated. The flow field of EHD atomization with single capillary was simulated.First of all, an experiment device of electrostatic atomization was set up. The phenomenon of EHD atomization process of deionized water was recorded using the high speed camera. The pulsation and separation frequency of the charged droplets at different voltage and volume flow rate were discussed. The effect of the capillary inner diameter and capillary number on the pulsation characteristics and separation frequency of the charged droplets were analyzed. The research results showed that the voltage and volume flow rate are two important parameters that could affect the droplet pulsation and frequency. With voltage increasing, the separation frequency first increases, and then decreases. The voltage corresponding to the maximum separation frequency increases as the volume flow rate increases. Compared with volume flow rate, the effects of the voltage on separation frequency play a dominated role when volume flow rate is small. Otherwise, the influences of volume flow rate on the separation frequency occupy a leading role.Second, EHD atomization modes of deionized water and ethanol issued from single, double and three capillaries were investigated. The effects of dimensionless volume flow rate ?, electrostatic Bond number ? and capillary inner diameter on atomization modes were analyzed. The results showed that volume flow rate ? and the electrostatic Bond number ? are corresponding to different atomization modes. In same mode, the electrostatic Bond number ? is an important parameter that could affect the meniscus, cone, jet and droplets. The atomization mode corresponding to the liquid flow rate and voltage, meniscus, cone, jet and spatial location of the droplets is connected with the capillary number and its space distribution.Third, the electric field produced by the single, double and three capillary electrodes were solved using elliptic integral method and MATLAB software. The results showed that the electric field decreases with ? and r increasing, which are the angle of point P to z positive axis and the distance of the origin point O to point P respectively. Adding the capillary number, the radial electric field of the area between the capillaries is abated, while the axial electric field is enhanced. The component electric field of incoherent area is enhanced. When ??0 and r is constant value, the smaller a, which is the average radius of capillary, the component of the electric field is smaller. When ?=0, r is smaller than a critical value, the smaller a, the greater the axial field. When r is greater than the critical value, the smaller a, axial electric field is smaller.Finally, the flow field model in electrostatic atomization with single capillary was established. The air flow field, the distribution of the electric field and charged droplets were simulated by using ANSYS-Fluent software with UDF. The results showed that the distance to the capillary axis is smaller, the electric field is greater. The main factor that influences the position and velocity distribution of the droplets is the coulomb repulsion. Due to the interaction between droplets and air, the motion of the droplets makes air acceleration. The axial and radial velocity of air of is larger near the capillary axis. The axial and radial velocity of air of is smaller in the other area.