Effect of Addition of Energetic Nanoparticles on Droplet-Burning Rate of Liquid Fuels

Abstract

A droplet stream combustion experiment was developed to understand the effect of reducing droplet size to a micrometer scale on the combustion characteristics of nanofluid fuels, which are liquid fuels with a stable suspension of nanoparticles. Pure ethanol and ethanol with aluminum nanoparticles at varying concentrations (up to 5 wt%) and droplet sizes were studied. The effect of particle addition on the droplet-burning rate was determined, and the mechanisms that are responsible for that effect were identified. The results show that the droplet-burning rate increases with increasing particle concentration. For example, with a 5 wt% addition of 80 nm aluminum nanoparticles, the burning rate increased by 140%. The burning rate enhancement is mainly attributed to strong radiation absorption of the nanoparticles suspended within the droplets, which provides more energy from the exothermic reaction (the flame) to the liquid phase (the droplets) for vaporization, thus increasing the burning rate. The radiation absorption effect becomes increasingly important as the droplet size increases.