Utilization of bulk nanobubbles to influence combustion characteristics of liquid fuels

Several reports have recently established the possibility of stable suspensions of bulk nanobubbles in liquids, thus opening new directions in a broad range of applications including power and propulsion applications that depend on liquid fuels. In this article, we report our investigation on bulk nanobubble suspensions of oxygen and nitrogen/air nanobubbles in isopropyl alcohol (IPA), ethanol, Jet A-1, and petrol. Bulk nanobubbles were generated by hot and cold solvent mixing method. Physical properties of the suspensions thus obtained were characterized in terms of the surface tension, zeta potential, bubble size distribution, and the mean bubble size. The stability of the suspension was tracked over a duration of three days. Finally, the combustion performance of the various fuel suspensions was investigated through single droplet combustion experiments. Results show successful generation of nanobubbles in all four fuels. IPA showed the highest bubble concentration. Bubble concentration decreased over time for all fuels. Droplet combustion studies revealed that the presence of nanobubbles led to a reduction in the burning rate constants for IPA, ethanol, and petrol, and an increase in burning rate constant for Jet A-1. Nanobubble suspensions are found to exhibit an increased frequency and intensity of bubble growth and bursting events, which in turn induced larger disturbances on the droplet interface in comparison to the pure fuels.