Effects of dielectric droplets on point-to-plane discharge dynamics and spark formation

In the frame of studies on engine combustion triggered by discharges with injected droplets of gasoline, the question of the influence of dielectric heterogeneities on the discharge development mechanisms has been studied. It has been performed at atmospheric pressure in a point-to-plane gap by means of optical and electrical high-speed techniques. It has been found that the injection of oil or ethanol micrometer-sized droplets into the gap implied several effects on the streamer advancement and its transition towards the spark phase. It has been shown that a jet of dielectric droplets could attract the discharge, increase the threshold of needed applied potential and the streamer velocity and, in a certain way, promote the spark formation. (author)