n-Decane-based nanofluid fuels could be one of the most promising alternative fuels as aviation kerosene for aerospace application. However, the physical and heat-transfer properties of n-decane-based nanofuels have been rarely studied, and the influence of the concentration of nanoparticles on the evaporation characteristics of n-decane-based fuels has been sparsely investigated. This paper investigated physical and heat-transfer properties and evaporation characteristics of graphite/n-decane nanofluid fuels and emphasized the concentration effect of adding graphite nanoplatelets (GNPs) on these characteristics. It was found that there are a linear increase of density and thermal conductivity, a binomial increase of viscosity, and a binomial influence on surface tension as GNP concentration increases, while the boiling point almost remains constant, and the latent heat of vaporization largely decays. There exists a critical GNP concentration of 1.75 wt % for the evaporation performance. At 0∼1.75 wt %, the increase of GNP concentration benefits the evaporation. At 1.75∼4.0 wt %, the enhancement of GNP concentration deteriorates the evaporation performance. A detailed discussion of this evaporation behavior was made, which could be attributed to multiple factors, for example, the aggregation of nanoplatelets, the changes of physical and heat-transfer properties owing to the nanoparticle concentration effect, the surfactant concentration, and the ambient temperature. The concentration of surfactants has a binomial effect, and the ambient temperature has a linear effect on the evaporation rate. This study would promote in depth understanding of physical and heat-transfer properties and evaporation characteristics of nanofluid fuels and develop the application in turbine engines and ramjet engines.

Jet fuel-based nanofluid fuel has been proposed for improving the energy density and utilization efficiency of jet fuel that is widely applied in aircraft powered by aviation turbine engines. To recognize the evaporation behavior of the formed liquid film as a jet fuel-based nanofluid sprayed onto the engine wall or blades, this paper presents the evaporation and deposition characteristics of the jet fuel-based nanofluid liquid film adhering on the hydrophilic substrate. The changes in contact line, contact angle, volume, and deposition pattern during liquid film evaporation under different substrate temperatures, different nanoparticle concentrations, and different kinds of nanoparticle additions were investigated. The effect of nano-Al addition on the evaporation kinetics and deposition pattern of the nano-Al/jet fuel (nAl/JF) nanofluid fuel liquid film was explored. Repeated pinning and de-pinning of contact lines during evaporation occurred, resulting in the formation of concentric multi-ring deposition patterns. The addition of nano-Al increased the evaporation rate and shortened the evaporation lifetime, demonstrating a promotion effect on jet fuel liquid film evaporation. The existence of an energy barrier shows that the movement of three-phase contact lines on the hydrophilic solid surface presented not a continuous sliding behavior but a "stick-slip" behavior, and there were multiple jumps in contact lines and contact angles. Finally, a comparison was made with the deposition pattern of jet fuel liquid films with different graphite and Fe nanoparticle additions during evaporation. The mechanism of deposition phenomena was deeply revealed by the analysis of capillary flow and Marangoni recirculation.