Theoretical and Experimental Investigations on Instability of an Electrically Charged Liquid Jet

Abstract By employing Lagrange equation of motion, a dispersion equation that accounts for the growth of axisymmetric, as well as non-axisymmetric waves on an electrically charged liquid jet is derived in this work, with considering the electric field configuration of a needle-plate apparatus for liquid spraying. The available theory is capable of predicting the phenomenon of both of axisymmetric and non-axisymmetric deformations of the liquid jet, which has long been observed in practice. It is demonstrated that there exist certain ranges of such parameters as applied voltage and needle-plate distance where the axisymmetric and non-axisymmetric modes of instability take place. The axisymmetric mode has a dominant effect at low electric field strength. As the electric field strength is increased, the non-axisymmetric mode is intensified. The present theory indicates that the critical wavelength, and thus, the droplet size are decreased with increasing applied voltage and/or shortening needle-plate distance, which is consistent with the experimental results.