ELECTROSTATICALLY ATOMIZED HYDROCARBON SPRAYS

A burner using an electrostatic method to produce and control a fuel s pray is investigated for non-burning sprays. The burner has a charge i njection nozzle and the liquid flow rate and charge injection rate are varied using hydrocarbon liquids of differing viscosities, surface te nsions and electrical conductivities (kerosene, white spirit and diese l oil). Droplet size distributions are measured and it is shown how th e dropsize, spray pattern, breakup mechanism and breakup length depend on the above variables, and in particular on the specific charge achi eved in the spray. The data are valuable for validating two computer m odels under development. One predicts the electric field and flow fiel d inside the nozzle as a function of emitter potential, geometry and f low rate. The other predicts the effect of charge on spray dispersion, with a view to optimizing spray combustion. It is shown that electros tatic disruptive forces can be used to atomize oils at flow rates comm ensurate with practical combustion systems and that the charge injecti on technique is particularly suitable for highly resistive liquids. Po ssible limitations requiring further research include the need to cont rol the wide spray angle, which may provide fuel-air mixtures too lean near the nozzle, and the need to design for maximum charge injection rate, which is thought to be limited by corona breakdown in the gas ne ar the nozzle orifice.