HARMONIC SPRAYING OF CONDUCTING LIQUIDS EMPLOYING AC-DC ELECTRIC-FIELDS

This paper reports the results of the work tarried out to investigate the breakup process of charged conducting liquid jet under the influen ce of an ac field superimposed onto a de field. The main aim of this p aper is to optimize the spraying parameters and to generate uniform dr oplets of highly conducting liquid in a controlled fashion by varying the strength and the frequency of the applied ac field, The electric f ield at the tip of a blunt needle facing a ground electrode was examin ed using a finite-element modeling technique, Three types of ground el ectrode configurations were investigated, A mathematical model for the electrostatic force on the leading edge of the droplet as a function of the liquid flowrate, the applied voltage, and distance between the capillary tip and the ground electrode has been developed, The breakup and droplet formation processes were investigated using a telemicrosc opic lens and charge-coupled device (CCD) camera, The video data was p rocessed using frame grabber software installed on a PC, The digital i mages were then analyzed utilizing image analysis software to give inf ormation on the breakup process and the size of droplets. A frequency range was identified where the formation of the droplets was synchroni zed with the applied ac field frequency. The effects of liquid flowrat e on the synchronous bands were examined, The experimental results sho wed the dependency of the droplets size and the emission frequency on the applied ac frequency.