SPRAY CHARACTERISTICS OF CHARGE INJECTION ELECTROSTATIC ATOMIZERS WITH SMALL-ORIFICE DIAMETERS

Abstract

Here the characteristics of charged sprays of insulating liquids generated by an improved charge injection (electrostatic) atomizer design are described, and the experimental database previously available in the literature is extended to a smaller range of orifice diameters and to more viscous liquids. Previously identified “subcritical” and “supercritical” electrohydrodynamic (EHD) regimes for the atomizer are confirmed to be present for the viscosity and orifice diameter ranges studied here, showing that these EHD regimes appear to be generic to the atomization method. The jet breakup dynamics and length are qualitatively and quantitatively studied using imaging and phase Doppler anemometry (PDA), and the general spray plume characteristics are quantitatively described in terms of droplet velocity and diameter probability density functions (PDFs). Radial spray charge and mass flow rates are quantified as using a purpose-built collecting system. By appropriately normalizing the data, the degree of self-similarity between different spray data sets is clearly evident and proves that the near-axis droplets are poorly charged and that the mean specific charge increases with radial displacement, again in a self-similar manner.