Droplet combustion behavior of nanofluid fuels

Abstract

The design of high-energy-density fuels is an area of significant interest for high speed propulsion systems. There is a tremendous need to augment the energy content of conventional and future synthetic fuels. One possible approach to accomplish this is the addition of highly exothermic and energetic materials nanoparticles (NPs) to liquid fuels. An experimental study about vaporization, ignition and burning characteristics of liquid fuels droplets containing energetic materials NPs was carried out at elevated temperatures and atmospheric pressure under normal gravity. The evaporation, autoignition and combustion of pure and stabilized fuel droplets were also conducted at same ambient conditions for comparison. Single component (n-heptane) and multicomponent (kerosene) liquid hydrocarbon fuels were selected as base fluids. Aluminum NPs were used as energetic additives. The effect of ambient temperature on the evaporation/combustion rate constant and on autoignition delay was investigated. The effects of other factors such as concentration of NPs, type and concentration of the surfactants and the type of base fluids (single- and multi- component hydrocarbon fuel) were also investigated. The research work starts with the investigation of physical and chemical methods to prepare homogeneous, stable and durable nanofluid fuels and their morphology were characterized. Then an isolated droplet was suspended at a silicon carbide fiber and suddenly exposed to high ambient temperature by the help of falling electric furnace at atmospheric pressure. The evaporation/combustion process and the autoignition delay times were recorded using high-speed photography. Evaporation/combustion constants were calculated from the linear regression time histories of droplet diameter squared. Furthermore, the residues obtained at the end of evaporation/combustion were collected and studied using field emission scanning electron microscope (FESEM) and energy dispersive x-ray spect...