Electrostatic effects on gasoline direct injection in atmospheric ambiance

An experimental investigation of electrostatic effects on gasoline injection from a commercially available injector into atmospheric ambiance is reported. The injector was modified with the addition of an insulated insert that introduced a sharp edge, through which an electric charge was introduced into the fuel. Visualization experiments were performed in order to characterize spray morphology both for electrostatically charged and noncharged sprays. Supported by PDA measurements of droplet size and velocity, these results indicate a faster transition of charged sprays from an initial stage of a narrow, columnlike spray to the desirable, hollow-cone spray. Light Fraunhofer diffraction measurements indicate slow temporal variation of the droplet size during injection and also that charged sprays have a considerably better repeatability of droplet size. These measurements were combined with a measurement of the average induced charge density in order to yield estimates of the electrostatic and inertial forces exerted on the droplets.