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.

Thermal-Chemical Characteristics of Al–Cu Alloy Nanoparticles

“…Metal based energetic materials (EMs) have been used in many applications including thermites, metastable intermolecular composites (MICs), explosives, pyrotechnics, composite solid propellants and energy storage [1][2][3][4]. Aluminum is a favorite choice because of its high reaction enthalpy, abundance, low cost and technological maturity for manufacturing.…”

Effect of metal oxide nanoparticles on the ignition characteristics of diesel fuel droplets: an experimental study

“…It causes that the ignition conditions are easily reached. In comparison with nanofuels, radiation heat transfer may become less significant for pure fuels because pure fuel is transparent to the radiation [9]. The amount of absorbed radiation energy by dosed diesel increases due to the greater radiation heat absorbance of metal oxide nanoparticles.…”

“…While for dense nanofuels, most particles were burned at a later stage as large agglomerate after the consumption of liquid fuel. Tanvir and Qiao [9] studied the droplet-burning rate of ethanol fuel with and without aluminum nanoparticles. Their results showed that the droplet-burning rate increases with increasing particle concentration.…”

Nanofluids revisited

“…Researchers reported enhancements of combustion performance as well as emission characteristics. Possible mechanisms are catalytic processes at the nanoparticle surface as well as increased evaporation rates due to radiation absorption by the particles [83][84][85][86][87][88][89][90][91][92][93][94]. Kao et al as well as Sarkar and Hirani suggested the addition of nanoparticles to brake fluids to improve thermal transport of dissipated braking energy and increase the boiling point to avoid vapor lock [95,96].…”