The Effect of Charge Density on Electro-Sprayed Droplets

ABSTRACT

This paper illustrates the variation in the droplet size with the change in the parameters like voltage, flow rate and electrode spacing when a charged liquid column is made to discharge in ambient conditions. The experimental set up consists of a capillary needle with a ground electrode, which causes the atomization to take place. Image processing techniques were used to determine the droplet size. A series of experiments were conducted with water as the working fluid for flow rates of 3.75 ml/min and 4.6 ml/min. The voltage used for the generation of spray was raised from 2 kV to 4.5 kV. The atomization quality improved with increasing the applied voltage and deteriorated with an increase in the liquid flow rate as well as with the increasing of the distance between the electrodes. The atomization process was also studied by placing a capacitor in the circuit. It was observed that better quality of atomization, without the ground electrode, could be obtained at lower voltage with the introduction of a capacitor in the circuit. This reduces the need of higher working voltage as well as simplifies the overall system by eliminating the requirement of a ground electrode. Furthermore, this study shows that the atomization quality is a function of charge density of the charged liquid column and the droplet size varies as the inverse of the square root of the charge density

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