Electrostatic Atomization of Vegetable Oils with Single and Multi-Orifice Nozzles

An electrostatic atomization nozzle was investigated to determine the viability of using this technology with soybean oil for industrial oil coating processes. The nozzle was constructed with a blunt high voltage electrode producing a plane-to-plane electrostatic atomization nozzle. Testing was conducted for various nozzle geometries including multiple inter-electrode gap distances, orifice diameters, and number of orifices. These nozzle variations were tested at two flow rates (jet velocities) for electrical performance and spray plume characterization. The motivation for testing a multi-orifice version of this nozzle was to increase the oil throughput for the nozzle and spray coverage. The increased capacity of the multi-orifice nozzle would provide more opportunity for the electrostatic atomization system to replace other nozzle technology currently in place for oil coating processes. It was found that this nozzle design works well for the single orifice configuration with soybean oil. The single orifice nozzle produced spray specific charge results similar to previous research with soybean oil. This nozzle with soybean oil also produced similar drop size statistics compared to previous research with kerosene and diesel oil, which have much lower viscosity than soybean oil. This suggests that atomization mechanism of bending and Rayleigh instability is independent of the viscosity of the oil as far as the resulting drop size distribution is concerned. The multi-orifice designs of the electrostatic atomization nozzle proved to be challenging and not consistent. Unexpected arcing occurred in the triangular region between the three orifices. Even with all three of the orifices residing well within the outer diameter of the high voltage electrode, balanced charging did not always occur between the three oil jets resulting in narrow spray plumes among wide vigorously atomized spray plumes. However, it was successfully operated and met the goals of increasing the flow rate and spray coverage produced by the nozzle. Some further design refinements could alleviate the challenges encountered with this nozzle during this investigation.