Plasma-induced fragmentation of water-in-kerosene emulsion droplets under a high-voltage pulsed discharge

Abstract

Alternative fuels offer significant environmental benefits, yet their reliable ignition and stable combustion in engines and power plants remain challenging, particularly when they contain inert components such as water. In such cases, highly concentrated energy input via pulsed electric discharges is a promising method for initiating the rapid heating, evaporation, fragmentation, and ignition of fuel emulsions. This study examined the key aspects of enhancing plasma-induced fragmentation of emulsion droplets using a pulsed electric discharge. Integral characteristics of such fragmentation were determined for water, kerosene, and water-in-kerosene emulsion droplets at a breakdown voltage of 4–4.5 kV (∼2–2.5 J of energy, sufficient for all tested droplets to reach critical fragmentation conditions). Experiments were performed using a custom high-voltage setup consisting of a pulse generator, an electrode system, and recording instruments. Current and voltage waveforms were analyzed, and high-speed imaging (up to 10 5 fps) was used to capture the dynamics of droplet fragmentation. The results show that plasma-induced fragmentation increases the evaporation surface area by factors of 50, 80, and 120 for water, kerosene, and water-in-kerosene emulsion droplets, respectively. The trajectories of the fragmentation front depend heavily on the composition and phase structure of the droplets. More homogeneous structures promote isotropic propagation of the fragmentation front in all spatial directions. Experimental data were processed to obtain approximating relations for the integral and local characteristics of plasma-assisted fragmentation of emulsion droplets. A physical model was developed describing the initiation of such fragmentation. These findings provide new insights into the mechanisms of plasma-induced fragmentation and offer potential pathways for ignition assistance and atomization enhancement in future gas turbine applications.