Electrostatic-spray theory

Abstract

The statistical equilibrium model for the electrostatic spraying of liquids, previously described by the author, is compared with the available experimental data for Woods’s metal, octoil, and glycerine. The model’s Lagrangian multipliers α′, β′, and δ′ have been evaluated for these fluids. In the two instances where the ratio α′/β′ could be determined (Woods’s metal and octoil), the same value −10−17±15% J was obtained. A tentative expression for this ratio is presented and it is proposed that all practical electrostatic-spray systems are dominated by electron-emission-limited processes. Discontinuities in mean specific charge as a function of droplet radius are predicted and shown to be consistent with the available data. Best correspondence with limited data indicates α′ to be proportional to an inverse fluid property capillary number. In addition, an expression for the pulsed system Lagrangian multiplier δ′ is developed for steady-state systems. The detailed characteristics of a pulsed benzene spray appropriate for use in internal-combustion engines are described.