Experimental evaluation of electrostatically assisted injection and combustion of ethanol-gasoline mixtures for automotive applications

A single nozzle port fuel injector was modified to apply electrostatic charge to the fuel stream, with the intention of studying electrostatically assisted sprays in a practical, port-injected engine. The modifications were kept external to the injector and involved placing an electrode and insulating liner over the tip of the injector. The performance of the modified injector, which combined pressure driven and electrostatic atomization, was characterized in three phases: the injector sprays themselves were studied, combustion of charged fuel droplets was studied, and the injector was installed and tested on a single cylinder spark ignition engine. In the first phase, Fraunhofer diffraction measurements of droplet size, and particle image velocimetry measurements of droplet velocity were performed. The charge transferred by the sprays was measured using an electrometer, and typical forces exerted on droplets in the sprays were estimated. In the second phase, charged fuel droplets of varying composition were suspended from a capillary in normal gravity conditions and ignited. The combustion was captured with high speed video and the rate of recession of droplets of various charge levels was compared. In the final phase of the study, a single cylinder spark ignition engine was modified to allow the installation of an electrostatically assisted fuel injector. The engine was operated both with and without electrostatic charge applied to the injector charge electrode to compare performance with and without electrostatic assistance. Engine performance was measured in terms of power output using a DC dynamometer, the in-cylinder pressure was recorded, and emissions of unburned hydrocarbons, oxides of nitrogen, and carbon monoxide were measured. Findings showed that electrostatic charge can indeed influence the quality of the sprays, the flame morphology and burning rate of fuel droplets, as well as the performance of a spark ignition engine typical of current automotive practice.