On the instability of an electrostatically sprayed liquid jet

Electrostatic spraying of insulators using field emission or ionization is characterized by the formation of a thin jet. Experimentally, this jet appears to be stable over most of its length. The stability of such a jet is examined theoretically. Since the jet is insulating, the charge injected becomes surface charge. This charge can be redistributed through electric mobility and charge convection. In addition, there is an electric field with a component parallel to the jet. This charge and field result in both a normal and a shearing electrical force. Calculations show that a charge with no tangential field stabilizes the long wavelengths while it makes the short wavelengths more unstable. On the other hand, a tangential electric field stabilizes the short wavelengths. The effect of both charge and the tangential field is much larger than the sum of the two effects separately. Fields and charge densities that are easily achievable in all experiment can be used to produce a stable jet. Calculations of the growth rate of instabilities for different values of the electrical parameters are presented.<>